Previous Article | Next Article 
Journal of Virology, September 1998, p. 7349-7356, Vol. 72, No. 9
0022-538X/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Binding of Sindbis Virus to Cell Surface
Heparan Sulfate
Andrew P.
Byrnes1 and
Diane E.
Griffin1,2,*
Departments of Molecular Microbiology and
Immunology1 and
Medicine and
Neurology,2 Johns Hopkins University School
of Hygiene and Public Health, Baltimore, Maryland 21205
Received 26 February 1998/Accepted 5 June 1998
 |
ABSTRACT |
Alphaviruses are arthropod-borne viruses with wide species ranges
and diverse tissue tropisms. The cell surface receptors which allow
infection of so many different species and cell types are still
incompletely characterized. We show here that the widely expressed
glycosaminoglycan heparan sulfate can participate in the binding of
Sindbis virus to cells. Enzymatic removal of heparan sulfate or the use
of heparan sulfate-deficient cells led to a large reduction in virus
binding. Sindbis virus bound to immobilized heparin, and this
interaction was blocked by neutralizing antibodies against the viral E2
glycoprotein. Further experiments showed that a high degree of
sulfation was critical for the ability of heparin to bind Sindbis
virus. However, Sindbis virus was still able to infect and replicate on
cells which were completely deficient in heparan sulfate, indicating
that additional receptors must be involved. Cell surface binding of
another alphavirus, Ross River virus, was found to be independent of
heparan sulfate.
 |
INTRODUCTION |
The alphaviruses belong to a genus
of enveloped RNA viruses which can replicate in insects, birds, and
mammals, including humans (60). They have a wide
geographic distribution and pose a serious threat to human health
in certain regions, causing fever, rash, arthralgia,
myalgia, and fatal encephalitis. In mammals, some alphaviruses
have tropisms for specific cell types such as muscle, neurons, and
lymphatic cells. A better knowledge of the cellular receptors
used by alphaviruses would have obvious implications for
understanding of the different cellular tropisms and pathogeneses of
these viruses, as well as applications to the design of safe live-attenuated vaccines.
Alphavirus virions have a simple structure, with a single strand of
positive-sense RNA enclosed in an icosahedral capsid, which is
surrounded by a lipid envelope derived from the host plasma membrane.
The envelope contains two viral glycoproteins, E1 and E2, which are
organized in spikes. During the initiation of infection, E2 is mainly
responsible for binding to cellular receptors. Following endocytosis, a
low-pH-dependent rearrangement of the glycoproteins occurs, triggering
the membrane fusion activity of E1 and allowing entry of the capsid
into the cytoplasm.
Alphaviruses cycle alternately between vertebrates and hematophagous
insects (usually mosquitoes), suggesting either that virions bind to
receptors that are highly conserved between species or that the virus
can use multiple receptors. A previous study has identified a role for
the 67-kDa high-affinity laminin receptor in binding of Sindbis virus
(SV) to rodent and monkey cells but not to avian cells (68).
Another study using Venezuelan equine encephalitis (VEE) virus
identified a 32-kDa receptor in mosquito cells which also appears
to be a laminin receptor (34). Other studies have
identified unknown 74- and 110-kDa proteins as possible receptors for
SV on mouse neuroblastoma cells (66) and a 63-kDa protein on
chicken cells (69).
The normal in vivo role of glycosaminoglycans (GAGs) is to bind a
diverse group of growth factors, chemokines, enzymes, and matrix
components (20). In addition, however, these carbohydrates are important in the cell surface binding of a number of
bacteria, parasites, and viruses (52). GAGs are
unbranched polysaccharides present ubiquitously on cell surfaces
and in the extracellular matrix and are usually found covalently
attached to core proteins (proteoglycans) (31, 61). Some
common types of GAG include heparan sulfate (HS), chondroitin sulfate
(CS), dermatan sulfate, and keratan sulfate. GAGs acquire a
net negative charge through N and O sulfation, and GAG-binding
domains of proteins are typically positively charged regions containing
arginine and lysine. Importantly, GAGs are found in a wide
variety of vertebrate and invertebrate species, including insects
(7).
The first virus found to bind HS was herpes simplex virus (HSV)
(70), and since then a number of other herpesviruses have been demonstrated to use HS as an initial receptor (43, 45, 58). In addition, recent work has shown that HS is also involved in the binding of human immunodeficiency virus type 1, foot-and-mouth disease virus, respiratory syncytial virus, dengue virus, and adeno-associated virus type 2 (9, 21, 32, 47, 62). It should
be noted, however, that additional receptors besides HS are involved in
binding and entry of many, perhaps all, of these viruses.
There is suggestive evidence that GAGs may be involved in the binding
of alphaviruses to cells. Binding appears to involve electrostatic
interactions between ionizable groups on the virus and the cell
membrane
it is highly dependent on the pH of the medium, and binding
is reduced in medium of elevated ionic strength (15, 18, 34, 37,
38, 49). Studies have also shown that polyanions, including
sulfated polysaccharides such as heparin, can influence
binding of alphaviruses. When present during viral absorption,
polyanions reduce the number of plaques formed in plaque assays
(40), and pretreatment of certain cells with heparin can increase binding of SV (63). A sulfated polysaccharide
contained in agar has been known for many years to inhibit the growth
and decrease the plaque size of alphaviruses (4, 11, 57).
Finally, the finding that treatment of cells with
heparinase reduces the plaque-forming efficiency of SV
(40) directly suggests that SV might bind to HS.
 |
MATERIALS AND METHODS |
Chemicals and antibodies.
The following were obtained from
Sigma (St. Louis, Mo.): heparin (183 U/mg, from porcine
intestinal mucosa), chondroitin sulfate A (CS-A) (bovine trachea), CS-B
(porcine skin), CS-C (shark cartilage), dextran (molecular weight,
500,000), heparinase I (EC 4.2.2.7), and chondroitinase ABC (EC
4.2.2.4; affinity-purified). Dextran sulfate (17% S) and DEAE-dextran
were obtained from Pharmacia (Piscataway, N.J.). The following were
obtained from Seikagaku America Inc. (Rockville, Md.): HS (bovine
kidney; 5.0 to 6.0% S), N-desulfated, N-acetylated
heparin (<0.2% NS, >8.0% S); completely desulfated
N-acetylated heparin (<0.1% NS, <1.5% S); completely desulfated N-sulfated heparin (>4.5% NS, 4.5 to 7.0%
S).
Monoclonal antibodies were obtained as ascites from BALB/c mice. The
following monoclonal antibodies were used: 202 immunoglobulin G3 (IgG3)
against SV E2 epitope ab (42), R6 IgG2a against SV E2
epitope c (46), and the control antibody 3E1, an IgG1
recognizing HSV (HB-8067, from the American Type Culture Collection
[Manassas, Va.]). IgG was purified from ascites with the Pierce T-Gel
purification kit. Purified IgG was stored in frozen aliquots until use.
Fab fragments were prepared by papain digestion with the Pierce
Immunopure Fab preparation kit and were separated from Fc and
undigested IgG with a protein A-Sepharose column. Concentrations of
antibody were determined by optical densitometry at 280 nm.
Viruses and cells.
Chinese hamster ovary (CHO-K1) cells
(CCL-61) and the GAG-deficient CHO derivatives pgsA-745 (CRL-2242),
pgsD-677 (CRL-2244), and pgsE-606 (CRL-2246) (2, 13, 33)
were obtained from the American Type Culture Collection and grown in
Ham's F-12 medium supplemented with 10% fetal calf serum and 50 µg
of gentamicin per ml. BHK-21 cells were grown in Dulbecco's modified
Eagle medium with the same supplements. SV strain Toto 1101 (51) and Ross River virus (RRV) strain T48 (27)
were grown and titered on BHK-21 cells.
For
35S-labeled viral stocks, BHK cells were infected for
1 h at a multiplicity of infection of approximately 2. Three hours
later, cells were rinsed and the medium was replaced with Met-Cys-free
Dulbecco's modified Eagle medium containing 1% fetal calf serum
and
35 µCi of [
35S]Met-Cys per ml. Supernatant fluid was
collected at 24 h postinfection
and clarified by centrifugation. A
one-third volume of 40% polyethylene
glycol 8000 in 2 M NaCl was
added, and the mixture was rocked
overnight at 4°C. Virus was
precipitated by centrifugation at
18,000 ×
g for
1 h and resuspended in a small volume of phosphate-buffered
saline
(PBS). Virus was applied to the top of a linear 15 to 40%
(wt/vol)
potassium tartrate gradient in PBS and centrifuged for
1.5 h at
190,000 ×
g. The viral band was collected and pelleted
by centrifugation through a 15% sucrose cushion for 30 min at
240,000 ×
g. Virus was resuspended in a small volume
of binding
buffer: PBS (pH 7.2) supplemented with 0.5 mM
MgCl
2, 0.5 mM CaCl
2 and 0.5% bovine serum
albumin (BSA). Virus was stored in aliquots
at

70°C. The counts per
minute (cpm)/PFU ratio for SV Toto 1101
was 9.0 × 10
4. For RRV T48, the ratio was 3.8 × 10
3.
Plaque assays.
Virus was diluted in PBS supplemented with
0.5 mM MgCl2 and 0.5 mM CaCl2. Polyanion
inhibitors were added as noted in Results. The medium was removed from
confluent BHK monolayers in 35-mm wells, and 200 µl of virus was
added. Cells were infected for 1 h in a humidified 5%
CO2 atmosphere at 37°C, with occasional rocking. Cells
were then overlaid with warm modified Eagle medium containing 0.6%
Bacto Agar (Difco, Detroit, Mich.) and 1% fetal calf serum and lacking
phenol red. Plaques were stained at 2 days with neutral red. When CHO
cells (or their derivatives) were used for plaque assays, agarose was
used instead of agar (to increase plaque diameter), and the overlay was
supplemented with nonessential amino acids.
Cell-binding assay.
Cells were plated at 4 × 105 per well in 12-well plates and used the following day.
Medium was removed from the cells, which were then rinsed twice on ice
with ice-cold binding buffer (PBS [pH 7.2], 0.5 mM MgCl2,
0.5 mM CaCl2, 0.5% BSA). Approximately 104 cpm
of 35S-labeled virus was added to each well in 150 µl of
binding buffer, and plates were rocked at 4°C for varying lengths of
time. Virus was removed and monolayers were rapidly rinsed twice with
ice-cold binding buffer. Cells were lysed in 1% sodium dodecyl
sulfate, and cpm were assayed by liquid scintillation.
In some experiments, cell monolayers were pretreated with
heparinase or chondroitinase. Enzyme incubations were performed
in binding buffer at room temperature with constant shaking for
1 h. Monolayers were rinsed twice, and virus binding was assayed
as
described above at 4°C.
Polyanion-binding assay.
Because GAGs bound poorly to
plastic plates, we adapted the method of Yang et al. (71) to
allow covalent coupling of polysaccharides through their carboxyl
groups. Ninety-six-well plates precoated with reactive hydrazide
linkers (Corning Costar, Wilkes Barre, Pa.) were incubated with 25 µg
of polysaccharide per well in 100 µl of 100 mM
1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and 50 mM borate, pH 5.2. Incubation was at room temperature overnight with constant shaking.
Plates were rinsed three times with 0.5 M sodium acetate, pH 4.0, and
incubated for 30 min in this solution. Plates were rinsed three times
with PBS and blocked with PBS containing 0.5% BSA for 30 min. Virus
(5 × 103 to 1 × 104 cpm) in 100 µl of PBS (pH 7.0) with 0.5% BSA was added to each well. All
incubations were performed at room temperature with constant shaking.
After 2 h, 50 µl from each well was collected and counted by
liquid scintillation. The amount bound to the plate was calculated by
subtracting the resulting cpm from the cpm in an uncoated well. When
antibody was used to block binding, virus and antibody were mixed for
30 min at room temperature before being added to the 96-well plate.
Heparin-Sepharose chromatography.
Prepacked 1-ml HiTrap
heparin-Sepharose columns (Pharmacia) were equilibrated at
room temperature with 10 ml of 100 mM NaCl-5 mM phosphate (pH
7.5)-0.5% BSA at a flow rate of 1 ml/min. Approximately 105 cpm of 35S-labeled virus was added in 1 ml
of the same buffer, followed by 4 ml of buffer. The virus was eluted
with a 40-ml linear gradient from 100 to 500 mM NaCl containing 5 mM
phosphate (pH 7.5) and 0.5% BSA. One-milliliter fractions were
collected and counted by liquid scintillation. Any remaining virus was
removed from the column by using 0.5% sodium dodecyl sulfate. The NaCl
concentration of each fraction was determined by measuring the
conductivity of a 50-fold-diluted aliquot.
Statistical analysis.
All results are expressed as
means ± standard deviations. Error bars in graphs represent
standard deviations. Unless otherwise noted, results were tested for
significance by analysis of variance (ANOVA), followed by the Tukey
test to determine differences among groups. Results having P
values of <0.05 were considered significant.
 |
RESULTS |
Inhibition of plaque formation by GAGs.
It has previously been
reported that certain polyanions, including some GAGs, decrease the
number of SV plaques when present in the medium during the binding step
of plaque assays (40). This might be interpreted as a type
of competition experiment; an excess of polyanions in the medium could
be preventing binding of the virus to a cell surface polyanion.
The major GAGs found on most cells are HS and CS. We examined this
blocking phenomenon further in plaque assays on BHK cells
by using
heparin (a highly sulfated version of HS) and the three
forms
of CS found on the cell surface: CS-A, CS-B (also known
as dermatan
sulfate), and CS-C. Heparin and dextran sulfate (an
artificial, highly
sulfated polysaccharide) inhibited plaque formation
to similar degrees
(Fig.
1A). CS-A and CS-C had no effect,
but
CS-B inhibited plaque formation when present in high
concentrations.

View larger version (18K):
[in this window]
[in a new window]
|
FIG. 1.
Inhibitory effects of polysaccharides on plaque
formation by SV. SV strain Toto 1101 was used throughout this study.
(A) SV was mixed with various GAGs or the highly sulfated
polysaccharide dextran sulfate and incubated on monolayers of BHK cells
for 1 h at 37°C before being overlaid with agar. (B) The
requirement for high sulfation was shown by the inability of HS or
various forms of desulfated heparin to inhibit SV
plaque formation. Abbreviations: CDSNS, completely desulfated,
N sulfated; CDSNAc, completely desulfated, N acetylated;
NDSNAc, N desulfated, N acetylated. Error bars are omitted for
clarity of presentation. Each point is the mean of three or more
measurements. *, P of <0.05 versus no inhibitor.
|
|
Recognition of GAG-binding sites by proteins is a function both of
saccharide sequence and the position and degree of sulfation.
HSV-1,
for example, shows strong preferences for certain motifs
in HS
(
14). Although heparin inhibited plaque formation in
our
assay, HS did not (Fig.
1B). Heparin has two- to threefold-more
sulfates per residue than HS (
16), and it is not unusual for
HS preparations of low sulfate content to show no inhibitory effect
on
HS-binding viruses (
9,
36). Because heparin and HS
contain
the same saccharides and differ only in the degree of
sulfation,
a large amount of sulfation must be critical to the ability
to
inhibit SV plaque formation. Further experiments with three
different
types of desulfated heparin, none of which
were able to inhibit
plaque formation, indicated that both N and O
sulfation are mandatory
for the inhibitory activity of heparin
(Fig.
1B).
Studies with radiolabeled SV confirmed that heparin in the
medium was able to decrease viral binding to cells (data not shown),
although additional interference of heparin at later steps,
such
as viral entry, cannot be excluded.
Cell surface HS binds SV.
Cell surface GAGs can be removed
enzymatically. Treatment of CHO cell monolayers with heparinase
I, which degrades HS, caused a decrease in the binding of radiolabeled
SV to the cell surface (Fig. 2).
Treatment of GAG-deficient pgsA-745 cells with up to 6 mIU of
heparinase per ml had no effect on binding of virus (data not
shown), indicating that the effect of heparinase was not due to
contaminating protease activity. Binding to CHO cells was unaffected by
digestion with chondroitinase ABC, which degrades all three forms of CS
(Fig. 2). Likewise, on BHK cells, heparinase I decreased binding of SV to a similar extent, and chondroitinase ABC again had no
effect (data not shown). Pretreatment of BHK monolayers with
heparinase was also able to reduce the number of plaques in a
standard plaque assay (data not shown), in agreement with previous
results (40). When binding of radiolabeled RRV was examined,
however, treatment of BHK or CHO cells with up to 6 mIU of
heparinase per ml had no effect on binding (data not shown).

View larger version (16K):
[in this window]
[in a new window]
|
FIG. 2.
Digestion of GAGs decreases the ability of cells to bind
SV. CHO monolayers were predigested with various concentrations of
heparinase I or chondroitinase ABC, and the amount of
radiolabeled virus bound after 1 h at 4°C was measured. Each
point is the mean of three measurements. *, P of <0.05
versus no enzyme.
|
|
As further confirmation that cellular HS binds SV, we examined binding
to a series of CHO cell mutants which are impaired
in GAG synthesis
(Fig.
3A). Radiolabeled virus bound
poorly to
pgsA-745 cells, which do not synthesize either HS or CS
because
of a deficiency in xylosyltransferase (
13), although
binding
was not completely abolished. SV bound equally poorly to
pgsD-677
cells, which are deficient in
N-acetylglucosaminyl-
and glucuronosyltransferase
(
33) and have no HS but a
threefold-higher level of CS on the
cell surface. Together, these
results indicate that HS is the
major GAG involved in binding of SV. As
further evidence of this,
binding to pgsE-606 cells, which are
deficient in
N-sulfotransferase
and produce a mixture of
normal and undersulfated HS (
2), was
intermediate between
binding to wild-type CHO cells and cell lines
which are completely
deficient in HS (Fig.
3A).

View larger version (14K):
[in this window]
[in a new window]
|
FIG. 3.
Binding of alphaviruses to GAG-deficient cells. (A)
Binding of SV to wild-type CHO cells, pgsE cells with partially
desulfated HS, pgsD cells lacking HS but having elevated CS,
and pgsA cells with no HS or CS. At each time point, binding to CHO
cells was significantly greater than binding to the three mutant cell
lines. Binding to pgsE cells was also significantly greater than
binding to pgsA and pgsD cells. There was no significant difference
between binding to pgsD and binding to pgsA cells. (B) Binding of RRV.
Binding to CHO cells was significantly greater than to the three mutant
cell lines (but see text). Each point is the mean of three
measurements.
|
|
RRV bound relatively well to CHO cells and to all three mutant cell
lines (Fig.
3B). There was nevertheless a significant
decrease in
binding to pgsA-745 cells, a finding that was replicated
in three
additional experiments. However, statistical analysis
also revealed
that binding at 1, 2 and 3 h to pgsD-677 cells (which
have CS but
no HS) was significantly less than binding to pgsA-745
cells (which
have neither CS nor HS). In addition, binding to
pgsE-606 cells (which
have normal CS but undersulfated HS) was
also significantly less than
binding to pgsA-745 cells at 2 and
3 h. It is clear that the small
differences in binding of RRV
to these cell lines must be due to other
factors besides the presence
or absence of GAGs on the cell surface.
These cell lines were
created with ethylmethane sulfonate mutagenesis
(
13), and it
is possible that they have multiple mutations
or that other small
differences have arisen during the process of
separately cloning
and expanding these cell lines. Given that treating
cells with
heparinase did not decrease binding of RRV and RRV
did not bind
well to heparin (see below), the slight difference
in binding
between CHO and pgsA-745 cells is not sufficient evidence
that
RRV binds cell surface HS.
Plaque assays on CHO and pgsA-745 cells demonstrated that SV was able
to infect and replicate on both cell lines. Plaque sizes
on the two
cell lines under agarose were similar, but the number
of plaques on
pgsA-745 cells was reduced to 11% ± 1.0% of the
number on CHO cells
(
P < 0.001 [
t test]), as would be
expected
because of the deficiency in viral binding. These results
confirm
that HS is important for binding of SV to cells but that other
receptors besides HS are by themselves sufficient to allow binding
and
entry of virus, although at a greatly reduced level.
Curiously, RRV replicated very poorly on CHO and pgsA-745 cells and was
unable to form plaques, even though it bound well
to both cell lines.
It is unclear whether this is analogous to
the postentry block in
replication seen with HSV-1 on CHO cells
(
59).
Binding of virus to immobilized GAGs.
In order to demonstrate
that GAGs were by themselves sufficient to mediate binding of virus (in
the absence of any other receptor), we immobilized various GAGs on
plastic plates and examined the binding of radiolabeled virus. Sindbis
virus bound at significant levels to heparin, dextran sulfate,
and CS-B but not to HS, dextran, desulfated heparin,
CS-A, or CS-C (Fig. 4A). This confirms
that the degree of sulfation is a critical factor in binding. The
result that SV bound well to CS-B was in agreement with the finding
that CS-B was able to inhibit plaque formation (Fig. 1). RRV, in
contrast, did not bind significantly to heparin or CS-B,
although it bound at high levels to dextran sulfate (Fig. 4B).

View larger version (19K):
[in this window]
[in a new window]
|
FIG. 4.
Binding of alphaviruses to immobilized GAGs.
Ninety-six-well plates were coated with various GAGs, and the amount of
radiolabeled virus that bound was assessed. (A) Binding of SV. (B)
Binding of RRV. Ten thousand counts per minute of virus per well were
used. Each bar represents the mean of four measurements. *,
P of <0.05 versus uncoated wells. See the legend to Fig. 1
for abbreviations.
|
|
Antibodies against the alphaviral glycoproteins, particularly against
E2, are able to neutralize virus in plaque assays and
reduce infection
in vivo. It was of interest to determine whether
monoclonal antibodies
to E2 could block binding of SV to isolated
GAGs. Heparin was chosen as
a substrate because it bound virus
well and was similar to the
physiological HS substrate. Purified
monoclonal antibodies against two
different neutralizing epitopes
on the E2 glycoprotein were able to
decrease the binding of radiolabeled
SV to immobilized heparin
(Fig.
5). R6 IgG (against E2c) inhibited
binding somewhat better than Fab fragments of R6, but both were
able to
completely block viral binding. Monoclonal antibody 202,
which
recognizes the E2ab epitope, was unable to completely inhibit
binding
but was still able to inhibit binding even at relatively
low
concentrations (Fig.
5). This might be related to cross-linking
of the
virus by 202, because Fab fragments of 202 did not show
this effect and
inhibited binding only at high concentrations.

View larger version (14K):
[in this window]
[in a new window]
|
FIG. 5.
Antibodies against the E2 glycoprotein can inhibit
binding of SV to heparin. Ninety-six-well plates coated with
heparin were incubated with 5,000 cpm of SV in the presence or
absence of IgG or Fab fragments. R6 recognizes the E2c epitope, and 202 recognizes the E2ab epitope. 3E1 is a control antibody against HSV-1.
Each point is the mean of two measurements. An additional experiment
gave similar results.
|
|
Sindbis virus also bound to heparin immobilized on Sepharose
beads and could be eluted from heparin-Sepharose columns with
increasing concentrations of NaCl (Fig.
6A). High concentrations
of salt disrupt
the electrostatic interactions between heparin
and
heparin-binding proteins, and this technique can yield
sensitive
information about the relative strength of binding. SV eluted
as a single peak at 343 mM NaCl. RRV T48, however, eluted as three
distinct peaks, at 100, 118, and 189 mM NaCl (Fig.
6B). Elution
of RRV
at lower salt concentrations than SV was consistent with
the poor
ability of RRV to bind to immobilized heparin (Fig.
4B).
Peak
fractions 3, 10, and 17 (Fig.
6B) were collected and plaqued
on BHK
cells. Fraction 3 contained no detectable infectious virus.
The
composition of this peak is unknown

it was observed in three
separate
gradient-purified preparations of RRV, where it accounted
for roughly 5 to 8% of total cpm (Fig.
6B to D). Elution of material
in 100 mM NaCl
was never seen with SV (which was prepared in an
identical manner).

View larger version (22K):
[in this window]
[in a new window]
|
FIG. 6.
Elution of alphavirus from heparin-Sepharose
columns. Virus (70,000 to 100,000 cpm) was added to the column in 100 mM NaCl buffer and eluted with a gradient of from 100 to 500 mM NaCl.
(A) SV. (B) RRV. Single viral clones from RRV peak fractions 10 and 17 were selected, grown, and radiolabeled. These viral clones eluted at
salt concentrations similar to the peaks from which they were
originally taken (C and D).
|
|
Individual plaques from RRV T48 fractions 10 and 17 were picked,
passaged once on BHK cells, and used to make
35S-labeled
purified virus. Both viruses grew to similar titers
and had similar
plaque sizes under agar overlays. Virus RRV 10a,
originally obtained
from the 118 mM peak, eluted at 112 mM NaCl
(Fig.
6C). Virus RRV 17a,
originally from the 189 mM peak, eluted
at 187 mM NaCl (Fig.
6D). This
indicates that our original preparation
of RRV T48 contained two
genetically distinct viral variants with
different abilities to bind to
heparin. The sequencing of such
variants will help to map the
regions of the glycoproteins which
are responsible for binding to
heparin.
Effects of sulfated polysaccharides on plaque size.
Studies
performed several decades ago found that an inhibitor in agar
influences the plaque sizes of viruses from many different families,
and the inhibitor was eventually determined to be a sulfated
polysaccharide (64). This inhibitor appears to slow the
spread of viruses which bind well to it, resulting in plaques with
reduced diameters. Agarose, a purified form of agar, does not contain
sulfated polysaccharides, and consequently alphaviruses with
small-plaque phenotypes under agar often have substantially increased
plaque sizes under agarose (48, 57). We found that SV plaque
size could be increased dramatically by using agarose overlays instead
of agar, indicating that the sulfated polysaccharide in agar was
inhibitory (Fig. 7A). As further
confirmation of this, addition of the cationic polymer DEAE-dextran to
agar led to increased plaque size, and addition of heparin to
agarose decreased plaque size compared with agarose alone (Fig. 7A).
Such manipulations had no effect on the plaque size of RRV (Fig. 7B),
consistent with the lack of interaction between RRV and GAGs in other
assays.

View larger version (15K):
[in this window]
[in a new window]
|
FIG. 7.
Effect of overlay on plaque diameter. Virus was absorbed
to monolayers of BHK cells for 1 h at 37°C and then overlaid
with 0.6% agar or agarose with or without additives. Plaque diameters
were measured at 2 days to the nearest 0.5 mm. (A) Effect of overlay
composition on SV strain Toto 1101. *, P of <0.05 versus
agar plus DEAE-dextran; , P of <0.05 versus agarose. (B)
Overlay composition had no significant effect on the plaque size of RRV
strain T48. Each bar is the mean of 15 or more measurements. Results
were analyzed by ANOVA on ranks, followed by Dunn's test.
|
|
 |
DISCUSSION |
We have shown that SV binds to cell surface HS based on a variety
of evidence, including the ability of heparin in the medium to
interfere with cell surface binding, decreased binding of SV to
heparinase-treated cells, decreased binding to cells which are
genetically deficient in HS, and direct binding of SV to immobilized heparin. In contrast, we were unable to show that RRV could
bind to cell surface GAGs, and RRV had a relatively poor ability to bind to immobilized heparin.
Proteins which have affinity for GAGs bind to them largely through
electrostatic interactions, with positively charged Arg and Lys side
chains interacting with negatively charged sulfates (17). As
in numerous other studies with HS-binding proteins, we found that
highly sulfated heparin was the most effective substrate for
binding, indicating that the degree of sulfation, more than the
polysaccharide backbone, was the critical determinant for strength of
binding. It has been observed for many years that cellular binding of a
number of alphaviruses (SV, Semliki Forest virus, and eastern equine
encephalitis, western equine encephalitis, and VEE viruses) is highly
dependent on electrostatic interactions because it is influenced by the
pH and ionic strength of the medium (15, 18, 34, 37, 38,
49). It therefore seems probable that other alphaviruses, in
addition to SV, also bind to cell surface HS.
Other receptors.
As mentioned in the introduction, many of the
viruses which are known to bind to GAGs also use other cell surface
molecules, usually proteins, as receptors. The situation has been most
carefully studied with HSV-1, where binding to HS is followed by
binding to a more specific protein receptor (44). This is
also true of HS-binding growth factors and signaling proteins such as
fibroblast growth factor: signal transduction and endocytosis require
binding to an additional, nonproteoglycan receptor (56).
Because SV was able to bind to and replicate on GAG-deficient pgsA-745
cells, it is clear that other receptors must also be involved.
The nature of these additional receptors is not completely clear. It
has previously been found that treating cells with either
proteases or
phospholipases decreases binding of SV (
66). Both
of these
results could conceivably be explained by digestion or
release of cell
surface proteoglycans, which exist as a mixture
of transmembrane
proteins and glycosylphosphatidylinositol-linked
proteins
(
6). Further studies on pgsA-745 cells in the absence
of
GAGs will be helpful in determining whether the remaining receptors
are
proteins, lipids, or carbohydrates.
The 67-kDa high-affinity laminin receptor has been identified as a
possible SV receptor on some types of mammalian cells (
68),
and a 32-kDa probable laminin receptor has also been identified
as a
possible receptor for VEE virus on mosquito cells (
34).
There are many different types of laminin receptors on the mammalian
cell surface, including the 67-kDa high-affinity receptor, another
67-kDa elastin-laminin receptor, a number of different integrin
receptors, and a number of different members of the galactoside-binding
lectin family (
41). The high-affinity laminin receptor is a
peculiar protein which has been the subject of intense interest
because
of its upregulation on metastatic tumor cells (
8).
The cell
surface receptor is a 67-kDa glycoprotein, but the putative
cDNA
encodes only a 37-kDa protein. Overexpression of this cDNA
leads to an
increase in binding of SV (
68). The 37-kDa protein
appears
to be a precursor of the 67-kDa protein on the basis of
shared
epitopes, partial amino acid sequencing of the 67-kDa protein,
and
pulse-chase analysis of its synthesis, but how it increases
its mass is
unclear. The 37-kDa protein contains neither a signal
sequence for
membrane translocation nor a transmembrane domain.
The coding sequence
is highly conserved among mammals, with only
two differences out of 295 amino acids between hamsters and humans
(
68). Bizarrely,
however, it has recently been discovered that
the 37-kDa protein is
also a ribosomal subunit (
10,
65).
Interestingly, laminin itself is an HS-binding protein, with several
independent binding sites on its three chains (
41).
It is
not clear whether this is related to the ability of the
high-affinity
laminin receptor to bind SV.
Implications for viral behavior and virulence.
Alphavirus
variants with reduced plaque sizes often have reduced virulence in vivo
as well, although there are certainly exceptions to this rule, and
fresh wild-type isolates frequently contain a mixture of large-plaque
and small-plaque viruses. Repeated tissue culture passaging of
alphaviruses can lead to decreased plaque size and decreased virulence
(19, 39). Small-plaque and large-plaque alphavirus
variants typically have different affinities for hydroxyapatite (a form
of calcium phosphate), indicating changes in the surface charge of the
glycoproteins (3, 23). It may be possible to reinterpret
these findings in light of our demonstration that SV can bind to
HS. We suggest that alphaviruses with a small-plaque phenotype under
agar (indicating strong binding to the agar sulfated polysaccharide)
may also bind better to HS and that strong binding to HS may decrease
virulence in vivo.
The strain of SV used in this study, Toto 1101, is a relatively
avirulent molecular clone derived from HRSP, a small-plaque
virus
(
51). Like most laboratory strains of SV, HRSP has been
passaged many times in tissue culture. Ongoing work indicates
that
other strains of SV also bind to HS. For example, strain
AR339 elutes
from heparin-Sepharose at an NaCl concentration of
338 mM and,
like Toto 1101, binds markedly better to CHO cells
than to
GAG-deficient pgsA-745 cells (
5). Further investigations
with minimally passaged strains of SV will be necessary to determine
the extent to which wild isolates bind HS. Nevertheless, it is
clear
that strains of SV in common laboratory usage bind significantly
to HS.
How might altering the affinity of alphaviruses for HS affect virulence
and pathogenesis? It is known that tissue culture
passaging of another
HS-binding virus, foot-and-mouth disease
virus, selects for variants
with increased heparin-binding ability,
decreased plaque size,
and decreased virulence (
53). These changes
are the result
of a single amino acid substitution in the VP3
capsid protein, from His
to Arg, and this probably leads to an
increased heparin
affinity through a direct interaction between
the Arg and
heparin (
53). These heparin-binding variant
viruses
replicate poorly in animals and rapidly revert to virulent
viruses
with reduced heparin affinity through loss of the
Arg or a spatially
proximal Lys. In this case, at least, viruses
which bind well
to HS have a selective advantage in tissue
culture but are disadvantaged
in animals.
There is evidence in the literature that changes in affinity for HS
could have implications for alphavirus pathogenesis. It
is useful to
first review the pharmacokinetics of HS-binding proteins:
when injected
intravenously, proteins with high heparin affinity
are removed
from the circulation and sequestered by cell surface
HS within minutes
(
28,
67,
72). Most of the injected protein
ends up in the
liver, where the HS is unusually highly sulfated,
having almost twice
as many sulfates as HS in other tissues (
35).
Intravenous
injection of heparin can increase the circulating
half-life of
intravenously injected HS-binding proteins and even
release previously
bound protein into the circulation. Heparin
affinity can also control
the tissue distribution of proteins.
For example, the
heparin-binding enzyme extracellular superoxide
dismutase
(EC-SOD) is normally sequestered by HS in tissue interstitial
spaces
and on endothelial cell surfaces. Roughly 2% of the human
population
has an allele for an EC-SOD variant with a single change
from Arg to
Gly, resulting in reduced affinity for heparin and
a
10-fold-greater plasma concentration of EC-SOD (
54).
Likewise,
when EC-SOD is injected subcutaneously or intramuscularly,
normal
EC-SOD is retained much longer at the injection site than
truncated
variants with reduced heparin affinity
(
29).
Remarkably, similar phenomena have been seen in a number of studies
with alphaviruses, and we would put forward the hypothesis
that this is
a function of binding to HS. Following intravenous
injection of virus,
it has been observed that small-plaque variants
of SV, VEE virus, and
western equine encephalitis virus are cleared
from the circulation much
faster than large-plaque strains (
22,
25,
50). For example,
30 min after injection of a radiolabeled
small-plaque variant of VEE,
more than 99% of the virus has disappeared
from the plasma, but when a
large-plaque variant is injected,
less than 1% is cleared in the same
time (
25). Half of the cpm
from the small-plaque virus can
be found accumulated in the liver,
and electron microscopic examination
of the liver reveals binding
and uptake of large amounts of virus. When
injected subcutaneously,
the small-plaque virus infects hamsters
poorly. Most animals fail
to seroconvert, and those that die have all
developed revertant
viruses with large-plaque morphologies
(
25).
As a second example, the major attenuating mutation in the TC-83
vaccine strain of VEE has been mapped to a change at E2 position
120 from Thr to Arg, a gain of a positively charged residue
(
30).
This virus has a smaller plaque size and a higher
affinity for
hydroxyapatite than the parental TD strain (
24)
and absorbs
better to BHK cells (
55). TC-83 is cleared
rapidly from the
plasma after intravenous injection, unlike TD
(
26). After subcutaneous
injection, TC-83 replicates more
slowly than virulent VEE but
eventually reaches slightly higher titers
in the bone marrow and
lymph nodes. However, the plasma viremia is much
lower (
1,
26). Interestingly, substitution of Lys at E2 120 also leads
to attenuation (
12).
These changes in plaque size and in vivo behavior suggest a possible
role for HS binding. To prove this, such viral variants
will need to be
tested in vitro for heparin affinity and binding
to cell
surface HS. In vivo, it would be expected that concurrent
intravenous
injection of heparin would increase the circulating
half-life
of small-plaque variants, as is seen with other heparin-binding
proteins. Sequencing of such variants will help to define the
regions
of the glycoproteins that are involved in binding to HS.
 |
ACKNOWLEDGMENTS |
This work was supported by a postdoctoral fellowship from the
National Multiple Sclerosis Society and by grants R01-NS18596 and
T32-AI07417 from the National Institutes of Health.
 |
FOOTNOTES |
*
Corresponding author. Mailing address: Department of
Molecular Microbiology and Immunology, Johns Hopkins University School of Hygiene and Public Health, 615 N. Wolfe St., Baltimore, MD 21205. Phone: (410) 955-3459. Fax: (410) 955-0105. E-mail:
dgriffin{at}welchlink.welch.jhu.edu.
 |
REFERENCES |
| 1.
|
Austin, F. J., and W. F. Scherer.
1971.
Studies of viral virulence. I. Growth and histopathology of virulent and attenuated strains of Venezuelan encephalitis virus in hamsters.
Am. J. Pathol.
62:195-210[Medline].
|
| 2.
|
Bame, K. J.,
L. Zhang,
G. David, and J. D. Esko.
1994.
Sulphated and undersulphated heparan sulphate proteoglycans in a Chinese hamster ovary cell mutant defective in N-sulphotransferase.
Biochem. J.
303:81-87.
|
| 3.
|
Bose, H. R.,
G. Z. Carl, and B. P. Sagik.
1970.
Separation of Sindbis virus plaque-type variants by calcium phosphate chromatography.
Arch. Gesamte Virusforsch.
29:83-89[Medline].
|
| 4.
|
Brown, L. N., and R. A. Packer.
1964.
Some factors affecting plaque size of western equine encephalomyelitis virus.
Am. J. Vet. Res.
25:487-493[Medline].
|
| 5.
| Byrnes, A. P., and D. E. Griffin.
Unpublished data.
|
| 6.
|
Carey, D. J., and D. M. Evans.
1989.
Membrane anchoring of heparan sulfate proteoglycans by phosphatidylinositol and kinetics of synthesis of peripheral and detergent-solubilized proteoglycans in Schwann cells.
J. Cell Biol.
108:1891-1897[Abstract/Free Full Text].
|
| 7.
|
Cássaro, C. M. F., and C. P. Dietrich.
1977.
Distribution of sulfated mucopolysaccharides in invertebrates.
J. Biol. Chem.
252:2254-2261[Abstract/Free Full Text].
|
| 8.
|
Castronovo, V.
1993.
Laminin receptors and laminin-binding proteins during tumor invasion and metastasis.
Invasion Metastasis
13:1-30[Medline].
|
| 9.
|
Chen, Y.,
T. Maguire,
R. E. Hileman,
J. R. Fromm,
J. D. Esko,
R. J. Linhardt, and R. M. Marks.
1997.
Dengue virus infectivity depends on envelope protein binding to target cell heparan sulfate.
Nat. Med.
3:866-871[Medline].
|
| 10.
|
Clausse, N.,
P. Jackers,
P. Jarès,
B. Joris,
M. E. Sobel, and V. Castronovo.
1996.
Identification of the active gene coding for the metastasis-associated 37LRP/p40 multifunctional protein.
DNA Cell Biol.
15:1009-1023[Medline].
|
| 11.
|
Colön, J. I.,
J. B. Idoine,
O. M. Brand, and R. D. Costlow.
1965.
Mode of action of an inhibitor from agar on growth and hemagglutination of group A arboviruses.
J. Bacteriol.
90:172-179[Abstract/Free Full Text].
|
| 12.
|
Davis, N. L.,
N. Powell,
G. F. Greenwald,
L. V. Willis,
B. J. B. Johnson,
J. F. Smith, and R. E. Johnston.
1991.
Attenuating mutations in the E2 glycoprotein gene of Venezuelan equine encephalitis virus: construction of single and multiple mutants in a full-length cDNA clone.
Virology
183:20-31[Medline].
|
| 13.
|
Esko, J. D.,
T. E. Stewart, and W. H. Taylor.
1985.
Animal cell mutants defective in glycosaminoglycan biosynthesis.
Proc. Natl. Acad. Sci. USA
82:3197-3201[Abstract/Free Full Text].
|
| 14.
|
Feyzi, E.,
E. Trybala,
T. Bergström,
U. Lindahl, and D. Spillmann.
1997.
Structural requirement of heparan sulfate for interaction with herpes simplex virus type 1 virions and isolated glycoprotein C.
J. Biol. Chem.
272:24850-24857[Abstract/Free Full Text].
|
| 15.
|
Fries, E., and A. Helenius.
1979.
Binding of Semliki Forest virus and its spike glycoproteins to cells.
Eur. J. Biochem.
97:213-220[Medline].
|
| 16.
|
Gallagher, J. T., and A. Walker.
1985.
Molecular distinctions between heparan sulphate and heparin. Analysis of sulphation patterns indicates that heparan sulphate and heparin are separate families of N-sulphated polysaccharides.
Biochem. J.
230:665-674[Medline].
|
| 17.
|
Gromm, J. R.,
R. E. Hilemann,
E. E. O. Caldwell,
J. M. Weiler, and R. J. Linhardt.
1995.
Differences in the interaction of heparin with arginine and lysine and the importance of these basic amino acids in the binding of heparin to acidic fibroblast growth factor.
Arch. Biochem. Biophys.
323:279-287[Medline].
|
| 18.
|
Hahon, N., and K. O. Cooke.
1967.
Primary virus-cell interactions in the immunofluorescence assay of Venezuelan equine encephalomyelitis virus.
J. Virol.
1:317-326[Abstract/Free Full Text].
|
| 19.
|
Heydrick, F. P.,
R. F. Wachter, and H. J. Hearn.
1966.
Host influence on the characteristics of Venezuelan equine encephalomyelitis virus.
J. Bacteriol.
91:2343-2348[Abstract/Free Full Text].
|
| 20.
|
Jackson, R. L.,
S. J. Busch, and A. D. Cardin.
1991.
Glycosaminoglycans: molecular properties, protein interactions, and role in physiological processes.
Physiol. Rev.
71:481-539[Free Full Text].
|
| 21.
|
Jackson, T.,
F. M. Ellard,
R. Abu Ghazaleh,
S. M. Brookes,
W. E. Blakemore,
A. H. Corteyn,
D. I. Stuart,
J. W. I. Newman, and A. M. Q. King.
1996.
Efficient infection of cells in culture by type O foot-and-mouth disease virus requires binding to cell surface heparan sulfate.
J. Virol.
70:5282-5287[Abstract/Free Full Text].
|
| 22.
|
Jahrling, P. B.
1976.
Virulence heterogeneity of a predominantly avirulent western equine encephalitis virus population.
J. Gen. Virol.
32:121-128[Abstract/Free Full Text].
|
| 23.
|
Jahrling, P. B., and J. L. Beall.
1977.
Chromatographic separations of alphavirus strains by hydroxylapatite.
J. Clin. Microbiol.
6:238-243[Abstract/Free Full Text].
|
| 24.
|
Jahrling, P. B., and G. A. Eddy.
1977.
Comparisons among members of the Venezuelan encephalitis virus complex using hydroxylapatite column chromatography.
Am. J. Epidemiol.
106:408-417[Abstract/Free Full Text].
|
| 25.
|
Jahrling, P. B., and L. Gorelkin.
1975.
Selective clearance of a benign clone of Venezuelan equine encephalitis virus from hamster plasma by hepatic reticuloendothelial cells.
J. Infect. Dis.
132:667-676[Medline].
|
| 26.
|
Jahrling, P. B., and W. F. Scherer.
1973.
Growth curves and clearance rates of virulent and benign Venezuelan encephalitis viruses in hamsters.
Infect. Immun.
8:456-462[Abstract/Free Full Text].
|
| 27.
|
Karabatsos, N.
1985.
International catalogue of arboviruses including certain other viruses of vertebrates, 3rd ed., p. 867-868.
American Society for Tropical Medicine and Hygiene, San Antonio, Tex.
|
| 28.
|
Karlsson, K., and S. L. Marklund.
1988.
Plasma clearance of human extracellular-superoxide dismutase C in rabbits.
J. Clin. Investig.
82:762-766.
|
| 29.
|
Karlsson, K.,
J. Sandström,
A. Edlund, and S. L. Marklund.
1994.
Turnover of extracellular-superoxide dismutase in tissues.
Lab. Investig.
70:705-710[Medline].
|
| 30.
|
Kinney, R. M.,
G.-J. Chang,
K. R. Tsuchiya,
J. M. Sneider,
J. T. Roehrig,
T. M. Woodward, and D. W. Trent.
1993.
Attenuation of Venezuelan equine encephalitis virus strain TC-83 is encoded by the 5' noncoding region and the E2 envelope glycoprotein.
J. Virol.
67:1269-1277[Abstract/Free Full Text].
|
| 31.
|
Kjellén, L., and U. Lindahl.
1991.
Proteoglycans: structures and interactions.
Annu. Rev. Biochem.
60:443-475[Medline].
|
| 32.
|
Krusat, T., and H.-J. Streckert.
1997.
Heparin-dependent attachment of respiratory syncytial virus (RSV) to host cells.
Arch. Virol.
142:1247-1254[Medline].
|
| 33.
|
Lidholt, K.,
J. L. Weinke,
C. S. Kiser,
F. N. Lugemwa,
K. J. Bame,
S. Cheifetz,
J. Massagué,
U. Lindahl, and J. D. Esko.
1992.
A single mutation affects both N-acetylglucosaminyltransferase and glucuronosyltransferase activities in a Chinese hamster ovary cell mutant defective in heparan sulfate biosynthesis.
Proc. Natl. Acad. Sci. USA
89:2267-2271[Abstract/Free Full Text].
|
| 34.
|
Ludwig, G. V.,
J. P. Kondig, and J. F. Smith.
1996.
A putative receptor for Venezuelan equine encephalitis virus from mosquito cells.
J. Virol.
70:5592-5599[Abstract/Free Full Text].
|
| 35.
|
Luon, M.,
J. A. Deakin, and J. T. Gallagher.
1994.
Liver heparan sulfate structure: a novel molecular design.
J. Biol. Chem.
269:11208-11215[Abstract/Free Full Text].
|
| 36.
|
Lycke, E.,
M. Johansson,
B. Svennerholm, and U. Lindahl.
1991.
Binding of herpes simplex virus to cellular heparan sulphate, an initial step in the adsorption process.
J. Gen. Virol.
72:1131-1137[Abstract/Free Full Text].
|
| 37.
|
Marker, S. C.,
D. Connelly, and P. B. Jahrling.
1977.
Receptor interaction between eastern equine encephalitis virus and chicken embryo fibroblasts.
J. Virol.
21:981-985[Abstract/Free Full Text].
|
| 38.
|
Marker, S. C., and P. B. Jahrling.
1979.
Correlation between virus-cell receptor properties of alphaviruses in vitro and virulence in vivo.
Arch. Virol.
62:53-62[Medline].
|
| 39.
|
Marshall, I. D.,
R. P. Scrivani, and W. C. Reeves.
1962.
Variation in the size of plaques produced in tissue culture by strains of western equine encephalitis virus.
Am. J. Hyg.
76:216-224.
|
| 40.
|
Mastromarino, P.,
C. Conti,
R. Petruzziello,
R. Lapadula, and N. Orsi.
1991.
Effect of polyions on the early events of Sindbis virus infection of Vero cells.
Arch. Virol.
121:19-27[Medline].
|
| 41.
|
Mecham, R. P.
1991.
Receptors for laminin on mammalian cells.
FASEB J.
5:2538-2546[Abstract].
|
| 42.
|
Mendoza, Q. P.,
J. Stanley, and D. E. Griffin.
1988.
Monoclonal antibodies to the E1 and E2 glycoproteins of Sindbis virus: definition of epitopes and efficiency of protection from fatal encephalitis.
J. Gen. Virol.
70:3015-3022[Abstract/Free Full Text].
|
| 43.
|
Mettenleiter, T. C.,
L. Zsak,
F. Zuckermann,
N. Sugg,
H. Kern, and T. Ben-Porat.
1990.
Interaction of glycoprotein gIII with a cellular heparinlike substance mediates adsorption of pseudorabies virus.
J. Virol.
64:278-286[Abstract/Free Full Text].
|
| 44.
|
Montgomery, R. I.,
M. S. Warner,
B. J. Lum, and P. G. Spear.
1996.
Herpes simplex virus-1 entry into cells mediated by a novel member of the TNF/NGF receptor family.
Cell
87:427-436[Medline].
|
| 45.
|
Neyts, J.,
R. Snoeck,
D. Schols,
J. Balzarini,
J. D. Esko,
A. van Schepdael, and E. de Clercq.
1992.
Sulfated polymers inhibit the interaction of human cytomegalovirus with cell surface heparan sulfate.
Virology
189:48-58[Medline].
|
| 46.
|
Olmsted, R. A.,
W. J. Meyer, and R. E. Johnston.
1986.
Characterization of Sindbis virus epitopes important for penetration in cell culture and pathogenesis in animals.
Virology
148:245-254[Medline].
|
| 47.
|
Patel, M.,
M. Yanagishita,
G. Roderiquez,
D. C. Bou-Habib,
T. Oravecz,
B. C. Hascall, and M. A. Norcross.
1993.
Cell-surface heparan sulfate proteoglycan mediates HIV-1 infection of T-cell lines.
AIDS Res. Hum. Retroviruses
9:167-174[Medline].
|
| 48.
|
Pattyn, S. R., and L. de Vleesschauwer.
1967.
Plaque production by group A arboviruses. I. Influence of DEAE-dextran on plaques under agar and agarose. Plaque production under carboxymethylcellulose.
Acta Virol.
11:305-311[Medline].
|
| 49.
|
Pierce, J. S.,
E. G. Strauss, and J. H. Strauss.
1974.
Effect of ionic strength on the binding of Sindbis virus to chick cells.
J. Virol.
13:1030-1036[Abstract/Free Full Text].
|
| 50.
|
Postic, B.,
C. J. Schleupner,
J. A. Armstrong, and M. Ho.
1969.
Two variants of Sindbis virus which differ in interferon induction and serum clearance. I. The phenomenon.
J. Infect. Dis.
120:339-347[Medline].
|
| 51.
|
Rice, C. M.,
R. Levis,
J. H. Strauss, and H. V. Huang.
1987.
Production of infectious RNA transcripts from Sindbis virus cDNA clones: mapping of lethal mutations, rescue of a temperature-sensitive marker, and in vitro mutagenesis to generate defined mutants.
J. Virol.
61:3809-3819[Abstract/Free Full Text].
|
| 52.
|
Rostand, K. S., and J. D. Esko.
1997.
Microbial adherence to and invasion through proteoglycans.
Infect. Immun.
65:1-8[Medline].
|
| 53.
|
Sa-Carvalho, D.,
E. Rieder,
B. Baxt,
R. Rodatte,
A. Tanuri, and P. W. Mason.
1997.
Tissue culture adaptation of foot-and-mouth disease virus selects viruses that bind to heparin and are attenuated in cattle.
J. Virol.
71:5115-5123[Abstract].
|
| 54.
|
Sandström, J.,
P. Nilsson,
K. Karlsson, and S. L. Marklund.
1994.
10-fold increase in human plasma extracellular superoxide dismutase content caused by a mutation in heparin-binding domain.
J. Biol. Chem.
269:19163-19166[Abstract/Free Full Text].
|
| 55.
|
Scherer, W. F.,
C. A. Ellsworth, and A. K. Ventura.
1971.
Studies of viral virulence. II. Growth and adsorption curves of virulent and attenuated strains of Venezuelan encephalitis virus in cultured cells.
Am. J. Pathol.
62:211-219[Medline].
|
| 56.
|
Schlessinger, J.,
I. Lax, and M. Lemmon.
1995.
Regulation of growth factor activation by proteoglycans: what is the role of the low affinity receptors?
Cell
83:357-360[Medline].
|
| 57.
|
Schleupner, C. J.,
B. Postic,
J. A. Armstrong,
R. W. Atchison, and M. Ho.
1969.
Two variants of Sindbis virus which differ in interferon induction. II. Virological characterizations.
J. Infect. Dis.
120:348-355[Medline].
|
| 58.
|
Secchiero, P.,
D. Sun,
A. L. de Vico,
R. W. Crowley,
M. S. Reitz,
G. Zauli,
P. Lusso, and R. C. Gallo.
1997.
Role of the extracellular domain of human herpesvirus 7 glycoprotein B in virus binding to cell surface heparan sulfate proteoglycans.
J. Virol.
71:4571-4580[Abstract].
|
| 59.
|
Shieh, M.-T.,
D. WuDunn,
R. I. Montgomery,
J. D. Esko, and P. G. Spear.
1992.
Cell surface receptors for herpes simplex virus are heparan sulfate proteoglycans.
J. Cell Biol.
116:1273-1281[Abstract/Free Full Text].
|
| 60.
|
Strauss, J. H., and E. G. Strauss.
1994.
The alphaviruses: gene expression, replication, and evolution.
Microbiol. Rev.
58:491-562[Abstract/Free Full Text].
|
| 61.
|
Stringer, S. E., and J. T. Gallagher.
1997.
Heparan sulphate.
Int. J. Biochem. Cell Biol.
29:709-714[Medline].
|
| 62.
|
Summerford, C., and R. J. Samulski.
1998.
Membrane-associated heparan sulfate proteoglycan is a receptor for adeno-associated virus type 2 virions.
J. Virol.
72:1438-1445[Abstract/Free Full Text].
|
| 63.
|
Symington, J., and M. J. Schlesinger.
1978.
Characterization of a Sindbis virus variant with altered host range.
Arch. Virol.
58:127-136[Medline].
|
| 64.
|
Takemoto, K. K.
1966.
Plaque mutants of animal viruses.
Prog. Med. Virol.
8:314-348[Medline].
|
| 65.
|
Tohgo, A.,
S. Takasawa,
H. Munakata,
H. Yonekura,
N. Hayashi, and H. Okamoto.
1994.
Structural determination and characterization of a 40 kDa protein isolated from rat 40 S ribosomal subunit.
FEBS Lett.
340:133-138[Medline].
|
| 66.
|
Ubol, S., and D. E. Griffin.
1991.
Identification of a putative alphavirus receptor on mouse neural cells.
J. Virol.
65:6913-6921[Abstract/Free Full Text].
|
| 67.
|
Wallinder, L.,
J. Peterson,
T. Olivecrona, and G. Bengtsson-Olivecrona.
1984.
Hepatic and extrahepatic uptake of intravenously injected lipoprotein lipase.
Biochim. Biophys. Acta
795:513-524[Medline].
|
| 68.
|
Wang, K.-S.,
R. J. Kuhn,
E. G. Strauss,
S. Ou, and J. H. Strauss.
1992.
High-affinity laminin receptor is a receptor for Sindbis virus in mammalian cells.
J. Virol.
66:4992-5001[Abstract/Free Full Text].
|
| 69.
|
Wang, K.-S.,
A. L. Schmaljohn,
R. J. Kuhn, and J. H. Strauss.
1991.
Antiidiotypic antibodies as probes for the Sindbis virus receptor.
Virology
181:694-702[Medline].
|
| 70.
|
WuDunn, D., and P. G. Spear.
1989.
Initial interaction of herpes simplex virus with cells is binding to heparan sulfate.
J. Virol.
63:52-58[Abstract/Free Full Text].
|
| 71.
|
Yang, B.,
B. L. Yang, and P. F. Goetinck.
1995.
Biotinylated hyaluronic acid as a probe for identifying hyaluronic acid-binding proteins.
Anal. Biochem.
228:299-306[Medline].
|
| 72.
|
Yuge, T.,
A. Furukawa,
K. Nakamura,
Y. Nagashima,
K. Shinozaki,
T. Nakamura, and R. Kimura.
1997.
Metabolism of the intravenously administered recombinant human basic fibroblast growth factor, trafermin, in liver and kidney: degradation implicated in its selective localization to the fenestrated type microvasculatures.
Biol. Pharm. Bull.
20:786-793[Medline].
|
Journal of Virology, September 1998, p. 7349-7356, Vol. 72, No. 9
0022-538X/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
This article has been cited by other articles:
-
Knight, R. L., Schultz, K. L. W., Kent, R. J., Venkatesan, M., Griffin, D. E.
(2009). Role of N-Linked Glycosylation for Sindbis Virus Infection and Replication in Vertebrate and Invertebrate Systems. J. Virol.
83: 5640-5647
[Abstract]
[Full Text]
-
Parrott, M. M., Sitarski, S. A., Arnold, R. J., Picton, L. K., Hill, R. B., Mukhopadhyay, S.
(2009). Role of Conserved Cysteines in the Alphavirus E3 Protein. J. Virol.
83: 2584-2591
[Abstract]
[Full Text]
-
Suzuki, R., Winkelmann, E. R., Mason, P. W.
(2009). Construction and Characterization of a Single-Cycle Chimeric Flavivirus Vaccine Candidate That Protects Mice against Lethal Challenge with Dengue Virus Type 2. J. Virol.
83: 1870-1880
[Abstract]
[Full Text]
-
Thammawat, S., Sadlon, T. A., Hallsworth, P. G., Gordon, D. L.
(2008). Role of Cellular Glycosaminoglycans and Charged Regions of Viral G Protein in Human Metapneumovirus Infection. J. Virol.
82: 11767-11774
[Abstract]
[Full Text]
-
Prestwood, T. R., Prigozhin, D. M., Sharar, K. L., Zellweger, R. M., Shresta, S.
(2008). A Mouse-Passaged Dengue Virus Strain with Reduced Affinity for Heparan Sulfate Causes Severe Disease in Mice by Establishing Increased Systemic Viral Loads. J. Virol.
82: 8411-8421
[Abstract]
[Full Text]
-
Aguilar, P. V., Adams, A. P., Wang, E., Kang, W., Carrara, A.-S., Anishchenko, M., Frolov, I., Weaver, S. C.
(2008). Structural and Nonstructural Protein Genome Regions of Eastern Equine Encephalitis Virus Are Determinants of Interferon Sensitivity and Murine Virulence. J. Virol.
82: 4920-4930
[Abstract]
[Full Text]
-
Pierro, D. J., Powers, E. L., Olson, K. E.
(2007). Genetic determinants of Sindbis virus strain TR339 affecting midgut infection in the mosquito Aedes aegypti. J. Gen. Virol.
88: 1545-1554
[Abstract]
[Full Text]
-
Ryman, K. D., Gardner, C. L., Burke, C. W., Meier, K. C., Thompson, J. M., Klimstra, W. B.
(2007). Heparan Sulfate Binding Can Contribute to the Neurovirulence of Neuroadapted and Nonneuroadapted Sindbis Viruses. J. Virol.
81: 3563-3573
[Abstract]
[Full Text]
-
Crim, R. L., Audet, S. A., Feldman, S. A., Mostowski, H. S., Beeler, J. A.
(2007). Identification of Linear Heparin-Binding Peptides Derived from Human Respiratory Syncytial Virus Fusion Glycoprotein That Inhibit Infectivity. J. Virol.
81: 261-271
[Abstract]
[Full Text]
-
Misinzo, G., Delputte, P. L., Meerts, P., Lefebvre, D. J., Nauwynck, H. J.
(2006). Porcine circovirus 2 uses heparan sulfate and chondroitin sulfate B glycosaminoglycans as receptors for its attachment to host cells.. J. Virol.
80: 3487-3494
[Abstract]
[Full Text]
-
Assavalapsakul, W., Smith, D. R., Panyim, S.
(2006). Identification and Characterization of a Penaeus monodon Lymphoid Cell-Expressed Receptor for the Yellow Head Virus. J. Virol.
80: 262-269
[Abstract]
[Full Text]
-
Greene, I. P., Wang, E., Deardorff, E. R., Milleron, R., Domingo, E., Weaver, S. C.
(2005). Effect of Alternating Passage on Adaptation of Sindbis Virus to Vertebrate and Invertebrate Cells. J. Virol.
79: 14253-14260
[Abstract]
[Full Text]
-
Aguilar, P. V., Paessler, S., Carrara, A.-S., Baron, S., Poast, J., Wang, E., Moncayo, A. C., Anishchenko, M., Watts, D., Tesh, R. B., Weaver, S. C.
(2005). Variation in Interferon Sensitivity and Induction among Strains of Eastern Equine Encephalitis Virus. J. Virol.
79: 11300-11310
[Abstract]
[Full Text]
-
Greene, I. P., Paessler, S., Austgen, L., Anishchenko, M., Brault, A. C., Bowen, R. A., Weaver, S. C.
(2005). Envelope Glycoprotein Mutations Mediate Equine Amplification and Virulence of Epizootic Venezuelan Equine Encephalitis Virus. J. Virol.
79: 9128-9133
[Abstract]
[Full Text]
-
Vlasak, M., Goesler, I., Blaas, D.
(2005). Human Rhinovirus Type 89 Variants Use Heparan Sulfate Proteoglycan for Cell Attachment. J. Virol.
79: 5963-5970
[Abstract]
[Full Text]
-
Zahn, A., Allain, J.-P.
(2005). Hepatitis C virus and hepatitis B virus bind to heparin: purification of largely IgG-free virions from infected plasma by heparin chromatography. J. Gen. Virol.
86: 677-685
[Abstract]
[Full Text]
-
Thepparit, C., Smith, D. R.
(2004). Serotype-Specific Entry of Dengue Virus into Liver Cells: Identification of the 37-Kilodalton/67-Kilodalton High-Affinity Laminin Receptor as a Dengue Virus Serotype 1 Receptor. J. Virol.
78: 12647-12656
[Abstract]
[Full Text]
-
Tseng, J.-C., Hurtado, A., Yee, H., Levin, B., Boivin, C., Benet, M., Blank, S. V., Pellicer, A., Meruelo, D.
(2004). Using Sindbis Viral Vectors for Specific Detection and Suppression of Advanced Ovarian Cancer in Animal Models. Cancer Res.
64: 6684-6692
[Abstract]
[Full Text]
-
Basu, A., Beyene, A., Meyer, K., Ray, R.
(2004). The Hypervariable Region 1 of the E2 Glycoprotein of Hepatitis C Virus Binds to Glycosaminoglycans, but This Binding Does Not Lead to Infection in a Pseudotype System. J. Virol.
78: 4478-4486
[Abstract]
[Full Text]
-
Smith, A. E., Helenius, A.
(2004). How Viruses Enter Animal Cells. Science
304: 237-242
[Abstract]
[Full Text]
-
Escribano-Romero, E., Jimenez-Clavero, M. A., Gomes, P., Garcia-Ranea, J. A., Ley, V.
(2004). Heparan sulphate mediates swine vesicular disease virus attachment to the host cell. J. Gen. Virol.
85: 653-663
[Abstract]
[Full Text]
-
Kahl, C. A., Marsh, J., Fyffe, J., Sanders, D. A., Cornetta, K.
(2004). Human Immunodeficiency Virus Type 1-Derived Lentivirus Vectors Pseudotyped with Envelope Glycoproteins Derived from Ross River Virus and Semliki Forest Virus. J. Virol.
78: 1421-1430
[Abstract]
[Full Text]
-
Shafti-Keramat, S., Handisurya, A., Kriehuber, E., Meneguzzi, G., Slupetzky, K., Kirnbauer, R.
(2003). Different Heparan Sulfate Proteoglycans Serve as Cellular Receptors for Human Papillomaviruses. J. Virol.
77: 13125-13135
[Abstract]
[Full Text]
-
Klimstra, W. B., Nangle, E. M., Smith, M. S., Yurochko, A. D., Ryman, K. D.
(2003). DC-SIGN and L-SIGN Can Act as Attachment Receptors for Alphaviruses and Distinguish between Mosquito Cell- and Mammalian Cell-Derived Viruses. J. Virol.
77: 12022-12032
[Abstract]
[Full Text]
-
Kern, A., Schmidt, K., Leder, C., Muller, O. J., Wobus, C. E., Bettinger, K., Von der Lieth, C. W., King, J. A., Kleinschmidt, J. A.
(2003). Identification of a Heparin-Binding Motif on Adeno-Associated Virus Type 2 Capsids. J. Virol.
77: 11072-11081
[Abstract]
[Full Text]
-
Okuma, K., Dalton, K. P., Buonocore, L., Ramsburg, E., Rose, J. K.
(2003). Development of a Novel Surrogate Virus for Human T-Cell Leukemia Virus Type 1: Inhibition of Infection by Osteoprotegerin. J. Virol.
77: 8562-8569
[Abstract]
[Full Text]
-
Zhao, Q., Pacheco, J. M., Mason, P. W.
(2003). Evaluation of Genetically Engineered Derivatives of a Chinese Strain of Foot-and-Mouth Disease Virus Reveals a Novel Cell-Binding Site Which Functions in Cell Culture and in Animals. J. Virol.
77: 3269-3280
[Abstract]
[Full Text]
-
Wang, E., Brault, A. C., Powers, A. M., Kang, W., Weaver, S. C.
(2002). Glycosaminoglycan Binding Properties of Natural Venezuelan Equine Encephalitis Virus Isolates. J. Virol.
77: 1204-1210
[Abstract]
[Full Text]
-
Smit, J. M., Waarts, B.-L., Kimata, K., Klimstra, W. B., Bittman, R., Wilschut, J.
(2002). Adaptation of Alphaviruses to Heparan Sulfate: Interaction of Sindbis and Semliki Forest Viruses with Liposomes Containing Lipid-Conjugated Heparin. J. Virol.
76: 10128-10137
[Abstract]
[Full Text]
-
Iqbal, M., McCauley, J. W.
(2002). Identification of the glycosaminoglycan-binding site on the glycoprotein Erns of bovine viral diarrhoea virus by site-directed mutagenesis. J. Gen. Virol.
83: 2153-2159
[Abstract]
[Full Text]
-
Kang, Y., Stein, C. S., Heth, J. A., Sinn, P. L., Penisten, A. K., Staber, P. D., Ratliff, K. L., Shen, H., Barker, C. K., Martins, I., Sharkey, C. M., Sanders, D. A., McCray, P. B. Jr., Davidson, B. L.
(2002). In Vivo Gene Transfer Using a Nonprimate Lentiviral Vector Pseudotyped with Ross River Virus Glycoproteins. J. Virol.
76: 9378-9388
[Abstract]
[Full Text]
-
Reddi, H. V., Lipton, H. L.
(2002). Heparan Sulfate Mediates Infection of High-Neurovirulence Theiler's Viruses. J. Virol.
76: 8400-8407
[Abstract]
[Full Text]
-
Lee, P., Knight, R., Smit, J. M., Wilschut, J., Griffin, D. E.
(2002). A Single Mutation in the E2 Glycoprotein Important for Neurovirulence Influences Binding of Sindbis Virus to Neuroblastoma Cells. J. Virol.
76: 6302-6310
[Abstract]
[Full Text]
-
Delputte, P. L., Vanderheijden, N., Nauwynck, H. J., Pensaert, M. B.
(2002). Involvement of the Matrix Protein in Attachment of Porcine Reproductive and Respiratory Syndrome Virus to a Heparinlike Receptor on Porcine Alveolar Macrophages. J. Virol.
76: 4312-4320
[Abstract]
[Full Text]
-
Brault, A. C., Powers, A. M., Holmes, E. C., Woelk, C. H., Weaver, S. C.
(2002). Positively Charged Amino Acid Substitutions in the E2 Envelope Glycoprotein Are Associated with the Emergence of Venezuelan Equine Encephalitis Virus. J. Virol.
76: 1718-1730
[Abstract]
[Full Text]
-
Smit, J. M., Klimstra, W. B., Ryman, K. D., Bittman, R., Johnston, R. E., Wilschut, J.
(2001). PE2 Cleavage Mutants of Sindbis Virus: Correlation between Viral Infectivity and pH-Dependent Membrane Fusion Activation of the Spike Heterodimer. J. Virol.
75: 11196-11204
[Abstract]
[Full Text]
-
Hulst, M. M., van Gennip, H. G. P., Vlot, A. C., Schooten, E., de Smit, A. J., Moormann, R. J. M.
(2001). Interaction of Classical Swine Fever Virus with Membrane-Associated Heparan Sulfate: Role for Virus Replication In Vivo and Virulence. J. Virol.
75: 9585-9595
[Abstract]
[Full Text]
-
Wang, F.-Z., Akula, S. M., Pramod, N. P., Zeng, L., Chandran, B.
(2001). Human Herpesvirus 8 Envelope Glycoprotein K8.1A Interaction with the Target Cells Involves Heparan Sulfate. J. Virol.
75: 7517-7527
[Abstract]
[Full Text]
-
Heil, M. L., Albee, A., Strauss, J. H., Kuhn, R. J.
(2001). An Amino Acid Substitution in the Coding Region of the E2 Glycoprotein Adapts Ross River Virus To Utilize Heparan Sulfate as an Attachment Moiety. J. Virol.
75: 6303-6309
[Abstract]
[Full Text]
-
Brault, A. C., Powers, A. M., Medina, G., Wang, E., Kang, W., Salas, R. A., De Siger, J., Weaver, S. C.
(2001). Potential Sources of the 1995 Venezuelan Equine Encephalitis Subtype IC Epidemic. J. Virol.
75: 5823-5832
[Abstract]
[Full Text]
-
Mandl, C. W., Kroschewski, H., Allison, S. L., Kofler, R., Holzmann, H., Meixner, T., Heinz, F. X.
(2001). Adaptation of Tick-Borne Encephalitis Virus to BHK-21 Cells Results in the Formation of Multiple Heparan Sulfate Binding Sites in the Envelope Protein and Attenuation In Vivo. J. Virol.
75: 5627-5637
[Abstract]
[Full Text]
-
Giroglou, T., Florin, L., Schäfer, F., Streeck, R. E., Sapp, M.
(2001). Human Papillomavirus Infection Requires Cell Surface Heparan Sulfate. J. Virol.
75: 1565-1570
[Abstract]
[Full Text]
-
Gardner, J. P., Frolov, I., Perri, S., Ji, Y., MacKichan, M. L., zur Megede, J., Chen, M., Belli, B. A., Driver, D. A., Sherrill, S., Greer, C. E., Otten, G. R., Barnett, S. W., Liu, M. A., Dubensky, T. W., Polo, J. M.
(2000). Infection of Human Dendritic Cells by a Sindbis Virus Replicon Vector Is Determined by a Single Amino Acid Substitution in the E2 Glycoprotein. J. Virol.
74: 11849-11857
[Abstract]
[Full Text]
-
Hallak, L. K., Spillmann, D., Collins, P. L., Peeples, M. E.
(2000). Glycosaminoglycan Sulfation Requirements for Respiratory Syncytial Virus Infection. J. Virol.
74: 10508-10513
[Abstract]
[Full Text]
-
Martínez, I., Melero, J. A.
(2000). Binding of human respiratory syncytial virus to cells: implication of sulfated cell surface proteoglycans. J. Gen. Virol.
81: 2715-2722
[Abstract]
[Full Text]
-
Hulst, M. M., van Gennip, H. G. P., Moormann, R. J. M.
(2000). Passage of Classical Swine Fever Virus in Cultured Swine Kidney Cells Selects Virus Variants That Bind to Heparan Sulfate due to a Single Amino Acid Change in Envelope Protein Erns. J. Virol.
74: 9553-9561
[Abstract]
[Full Text]
-
Lee, E., Lobigs, M.
(2000). Substitutions at the Putative Receptor-Binding Site of an Encephalitic Flavivirus Alter Virulence and Host Cell Tropism and Reveal a Role for Glycosaminoglycans in Entry. J. Virol.
74: 8867-8875
[Abstract]
[Full Text]
-
Feldman, S. A., Audet, S., Beeler, J. A.
(2000). The Fusion Glycoprotein of Human Respiratory Syncytial Virus Facilitates Virus Attachment and Infectivity via an Interaction with Cellular Heparan Sulfate. J. Virol.
74: 6442-6447
[Abstract]
[Full Text]
-
Schneider-Schaulies, J.
(2000). Cellular receptors for viruses: links to tropism and pathogenesis. J. Gen. Virol.
81: 1413-1429
[Full Text]
-
Takikawa, S., Ishii, K., Aizaki, H., Suzuki, T., Asakura, H., Matsuura, Y., Miyamura, T.
(2000). Cell Fusion Activity of Hepatitis C Virus Envelope Proteins. J. Virol.
74: 5066-5074
[Abstract]
[Full Text]
-
Baranowski, E., Ruiz-Jarabo, C. M., Sevilla, N., Andreu, D., Beck, E., Domingo, E.
(2000). Cell Recognition by Foot-and-Mouth Disease Virus That Lacks the RGD Integrin-Binding Motif: Flexibility in Aphthovirus Receptor Usage. J. Virol.
74: 1641-1647
[Abstract]
[Full Text]
-
Iqbal, M., Flick-Smith, H., McCauley, J. W.
(2000). Interactions of bovine viral diarrhoea virus glycoprotein Erns with cell surface glycosaminoglycans. J. Gen. Virol.
81: 451-459
[Abstract]
[Full Text]
-
Byrnes, A. P., Griffin, D. E.
(2000). Large-Plaque Mutants of Sindbis Virus Show Reduced Binding to Heparan Sulfate, Heightened Viremia, and Slower Clearance from the Circulation. J. Virol.
74: 644-651
[Abstract]
[Full Text]
-
Vazquez, M.-I., Esteban, M.
(1999). Identification of Functional Domains in the 14-Kilodalton Envelope Protein (A27L) of Vaccinia Virus. J. Virol.
73: 9098-9109
[Abstract]
[Full Text]
-
Smit, J. M., Bittman, R., Wilschut, J.
(1999). Low-pH-Dependent Fusion of Sindbis Virus with Receptor-Free Cholesterol- and Sphingolipid-Containing Liposomes. J. Virol.
73: 8476-8484
[Abstract]
[Full Text]
-
Nisole, S., Krust, B., Callebaut, C., Guichard, G., Muller, S., Briand, J.-P., Hovanessian, A. G.
(1999). The Anti-HIV Pseudopeptide HB-19 Forms a Complex with the Cell-surface-expressed Nucleolin Independent of Heparan Sulfate Proteoglycans. J. Biol. Chem.
274: 27875-27884
[Abstract]
[Full Text]
-
Klimstra, W. B., Heidner, H. W., Johnston, R. E.
(1999). The Furin Protease Cleavage Recognition Sequence of Sindbis Virus PE2 Can Mediate Virion Attachment to Cell Surface Heparan Sulfate. J. Virol.
73: 6299-6306
[Abstract]
[Full Text]
-
Feldman, S. A., Hendry, R. M., Beeler, J. A.
(1999). Identification of a Linear Heparin Binding Domain for Human Respiratory Syncytial Virus Attachment Glycoprotein G. J. Virol.
73: 6610-6617
[Abstract]
[Full Text]
-
Jan, J.-T., Byrnes, A. P., Griffin, D. E.
(1999). Characterization of a Chinese Hamster Ovary Cell Line Developed by Retroviral Insertional Mutagenesis That Is Resistant to Sindbis Virus Infection. J. Virol.
73: 4919-4924
[Abstract]
[Full Text]