This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrowReprints and Permissions
Right arrow Copyright Information
Right arrow Books from ASM Press
Right arrow MicrobeWorld
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Coil, D. A.
Right arrow Articles by Miller, A. D.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Coil, D. A.
Right arrow Articles by Miller, A. D.

 Previous Article  |  Next Article 

Journal of Virology, September 2005, p. 11496-11500, Vol. 79, No. 17
0022-538X/05/$08.00+0     doi:10.1128/JVI.79.17.11496-11500.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

Enhancement of Enveloped Virus Entry by Phosphatidylserine

David A. Coil1,2 and A. Dusty Miller1*

Division of Human Biology,1 Molecular and Cellular Biology Program, Fred Hutchinson Cancer Research Center, Seattle, Washington 981092

Received 5 May 2005/ Accepted 26 May 2005


arrow
ABSTRACT
 
Enveloped virus vectors are used in a wide variety of applications. We have discovered that treatment of cultured cells with phosphatidylserine (PS) liposomes can increase virus vector infection by up to 20-fold. This effect does not abrogate virus receptor requirements, is specific to PS compared to other phospholipids, and is limited to enveloped viruses. Furthermore, the enhancement of infection does not occur through increases in virus receptor levels or virus binding, indicating that virus fusion is enhanced. The liposomes are easily generated, store well, and allow enhanced infection with a variety of virus vectors and cell types.


arrow
TEXT
 
Enveloped virus vectors, in particular, retrovirus vectors and vectors incorporating the vesicular stomatitis virus envelope (Env) glycoprotein (VSV-G), are currently used in a wide variety of applications ranging from mutagenesis to gene therapy (for examples, see references 2, 16, and 43). However, many applications are limited by vector titer. Viruses can be concentrated to circumvent this limitation, but concentration is difficult for some viruses, including many common retroviruses. Infection rates can also be improved by including polycations such as Polybrene, protamine sulfate, or charged polymers during infection (20, 21, 23, 38, 40). Improved infection is thought to occur by reducing the repulsive-charge interactions between the viral envelope and the cell (12, 13).

We recently discovered that infection by two different enveloped virus vectors could also be enhanced by the treatment of target cells with liposomes composed of phosphatidylserine (PS) (10). This effect was cumulative with Polybrene and therefore suggested that PS treatment would provide a useful tool to enhance virus infection. Here we further characterize this phenomenon and find that PS treatment may influence virus fusion.

PS treatment of target cells enhances infection by multiple enveloped viruses when functional virus receptors are present. We treated a variety of cell types with PS and exposed them to several different viral vectors to examine the specificity and magnitude of transduction enhancement by PS (Table 1). All cells expressed functional receptors for the virus vectors used. Viruses carried the LAPSN retroviral vector (27) that encodes human placental alkaline phosphatase (AP) or the LNCG retroviral vector (32) that encodes green fluorescent protein (GFP) and were made using the following packaging cell lines that express the indicated Env proteins: PA317 (amphotropic murine leukemia virus [MLV] strain 4070A) (24); FlyRD (RD114) (11); PJ4 (jaagsiekte sheep retrovirus [JSRV]) (30); and PG13 (gibbon ape leukemia virus [GALV]) (25). VSV-G pseudotype vectors were made by transfection, as described previously (10). Treatment of the target cells with PS increased transduction by these viruses by 2- to 20-fold. We also examined the relationship of this enhancement to the one provided by Polybrene and determined that the treatments had synergistic effects. For example, JSRV infection of Rat-2/Hyal2 cells was enhanced 4-fold by Polybrene alone, 6-fold by PS alone, and 25-fold by the two combined (means of results of two experiments).


View this table:
[in this window]
[in a new window]
  		TABLE 1. Enhancement of enveloped virus infection following treatment of cells with PSa

We attempted to use PS treatment to increase infection of HT-1080 cells by two nonenveloped viruses, an adenovirus type 5 vector (Ad.RSV-ßgal) (42) and an adeno-associated virus type 2 vector (CWCZn) (15), both of which encoded ß-galactosidase. In these cases, PS treatment actually reduced virus infection by 75% and 25%, respectively. These results show that PS does not stimulate infection by these nonenveloped virus vectors and suggest that PS enhancement of infection may take place at the fusion step of virus entry, which is not required by nonenveloped viruses.

PS treatment of target cells does not allow entry of viruses in cases where a functional receptor is not present. To test whether the enhancement of virus infection was receptor independent, we exposed a variety of cell lines to viruses that ordinarily cannot infect these cells due to lack of functional receptors. We tested a Moloney MLV pseudotype LAPSN vector made by using PE501 retrovirus packaging cells (26) on HT-1080 and HEK 293 human cells; a JSRV pseudotype LAPSN vector on the rat cell lines 208F, NRK, and Rat-2; a GALV pseudotype LAPSN vector on NIH 3T3 mouse cells; and a xenotropic MLV (AKR6) pseudotype LAPSN vector on CHO-K1 hamster cells. The LAPSN(AKR6) xenotropic virus was produced by infection of Mus dunni tail fibroblasts with LAPSN and replication-competent AKR6 virus (8). Transduction was undetectable (<1 AP+ focus-forming unit/ml) with or without PS in two independent experiments for all of these virus-cell combinations. Positive-control infections showed that all of these cell types were appropriately infectible by retroviral vectors that recognized receptors expressed by the cells (data not shown).

PS treatment temporarily increases the amount of cell-surface PS on target cells. To further characterize the effect of PS treatment, we investigated whether the exogenously added PS liposomes were incorporated into the plasma membrane of the target cells. The increase of cell-surface PS levels measured in NIH 3T3, ZF4, HT-1080, and Rat-2 cells after PS treatment is depicted in Fig. 1. Both the background PS levels and the magnitude of the increase after the addition of PS liposomes vary in these cell types. However, there was no obvious correlation between the increase in cell-surface PS levels (Fig. 1) and the magnitude of the enhancement of virus infection (Table 1). Expression of various viral receptors on NIH 3T3 and Rat-2 cells did not affect PS levels or the response to PS liposomes in this assay (<5% change in duplicate experiments [data not shown]). Within 72 h of PS treatment, the PS levels of treated cells were back to normal, and the cells were infectible to the same level as untreated cells (data not shown).



View larger version (30K):
[in this window]
[in a new window]
  		FIG. 1. PS treatment increases the amount of cell-surface PS in various cell types. Cells were treated with PS at 400 µM for 24 h and were stained for surface PS levels with fluorescent dye-labeled annexin-V as previously described (10). This protein binds tightly and specifically to PS and is commonly used to measure cell-surface PS levels (3, 19, 35-37). The dotted line shows untreated cells, the thin line shows control cells labeled with annexin-V, and the thick line shows PS-treated cells labeled with annexin-V. Each peak contains approximately 10,000 cells.

The dose response of target cells to PS treatment varies between cell types. In addition to PS having various effects on virus infection, the different cell lines had varied responses to the addition of PS. A few cell lines exhibited moderate death and an inhibition of growth, whereas most cells lines were less affected. Variation between cell types in cell-surface PS levels after the addition of 400 µM PS liposomes is indicated in Fig. 1.

To examine the dose response of infection to different amounts of PS, HT-1080 and Rat-2/Hyal2 cells were incubated with various levels of PS for 24 h, and the rate of infection following exposure to LAPSN(JSRV) virus was determined (Fig. 2). For Rat-2/Hyal2 cells, the optimum concentration of PS was 80 µM, whereas the optimum concentration for HT-1080 cells was 320 µM. At the highest levels of PS, the Rat-2/Hyal2 cells began to die, whereas the HT-1080 cells were much more resistant to this toxicity (data not shown). Because the dose response of cells to PS varies between cell types, it will be important to determine the optimal concentration of PS for a given cell type. Our results indicate that even higher levels of enhancement might be achieved in some cell types by treating cells with lower concentrations of PS than those used in Table 1.



View larger version (19K):
[in this window]
[in a new window]
  		FIG. 2. Effects of various concentrations of PS on virus infection of two cell types. PS treatment of HT-1080 and Rat-2/Hyal2 cells and virus infection by LAPSN(JSRV) were performed as described in the text except that PS liposomes were added at concentrations of 400, 320, 240, 80, 32, and 6.4 µM. Data shown are means ± standard deviations for triplicate wells. This experiment was repeated once with similar results.

Addition of other phospholipids does not affect enveloped-virus infection. To address the possibility that nonspecific disruption of the cell membrane by the addition of phospholipids was responsible for the enhancement of infection by PS, we examined the effects of liposomes composed of other phospholipids. Our previous work had shown that phosphatidylcholine (PC) liposomes had no effect on VSV-G and RD114 pseudotype vector infection in ZF4 cells (10). In addition to PS and PC, Rat-2/Hyal2 cells were treated with phosphatidylglycerol (PG), and phosphatidylethanolamine (PE). These lipids were chosen because of their similarity to PS and their potential roles in membrane fusion; PG may interact with the human immunodeficiency virus type 1 fusion peptide to play a role in lentiviral fusion (28, 29), and PE has the ability to promote the bilayer- to hexagonal-phase transition that may facilitate membrane fusion (34). The addition of PC, PG, or PE did not affect the PS levels in the target cells as measured by annexin-V staining (<5% change in duplicate experiments). None of these three phospholipids had any noticeable effect on virus infection, while the addition of PS resulted in a large boost in infection by LAPSN(JSRV) virus (Fig. 3). Similar results were found for LAPSN(RD114) virus infection of HT-1080 cells (data not shown).



View larger version (17K):
[in this window]
[in a new window]
  		FIG. 3. Enhancement of infection is specific to PS compared to other phospholipids. LAPSN(JSRV) infections of Rat-2/Hyal2 cells were performed as described in the text. The same protocol was used for generation of liposomes from L-{alpha}-phosphatidyl-DL-glycerol, L-{alpha}-phosphatidylcholine, and L-{alpha}-phosphatidylethanolamine (Sigma) as described for PS. Liposomes were added to cells at 400 µM for 24 h. Data shown are means ± standard deviations from two experiments, each performed in duplicate.

PS treatment has little effect on virus receptor levels or Env binding to cells. To examine whether PS treatment increased virus infection by increasing virus receptor levels or by increasing virus binding to cells, we measured cell-surface receptor levels and JSRV Env binding to Rat-2/Hyal2 cells. The Rat-2/Hyal2 cells contain an amino-terminal FLAG-tagged Hyal2 protein which functions as a receptor for JSRV (31). These cells were treated with or without 80 µM PS for 24 h, and receptor levels were measured using an anti-FLAG antibody (Fig. 4). This concentration of PS was used because it maximizes the increase in infectivity for this cell type (Fig. 2) and therefore should maximize changes in factors that mediate the increase. In the same assay, the amount of JSRV Env binding was measured by using a JSRV Env surface domain-human immunoglobulin G fusion protein (JSU-IgG) as previously described (39) (Fig. 4). Both the levels of Hyal2 protein and JSU-IgG binding show <2-fold increases after PS treatment. In addition, the background fluorescence of the cells alone increases with PS treatment, reducing the measured effect even further. These small changes are unlikely to account for the up-to-sevenfold increase in JSRV infection observed in these cells upon PS treatment. The fact that neither receptor levels nor virus binding was significantly affected by PS treatment further supports the hypothesis that PS treatment enhances the fusion step of virus entry.



View larger version (19K):
[in this window]
[in a new window]
  		FIG. 4. PS treatment effects on virus binding and receptor levels. The left panels show the binding of FLAG antibody to the Rat-2/Hyal2 cells, with and without PS treatment. Cells were treated with 80 µM PS for 24 h. Dashed lines represent the level of fluorescence of cells without any antibody; dotted lines represent cells incubated with secondary antibody only; and solid heavy lines represent cells incubated with anti-FLAG antibody and secondary antibody. The two right panels show the binding of JSU-IgG to the Rat-2/Hyal2 cells with and without PS treatment. Both sets of experiments were performed simultaneously using the same PS preparation. Dashed lines represent the level of fluorescence of cells without any antibody; dotted lines represent cells incubated with secondary antibody only; and solid heavy lines represent cells incubated with JSU-IgG (21 µg/ml) and secondary antibody. Each peak contains approximately 50,000 cells. This experiment was repeated three additional times, and the relative positions of the peaks varied by ≤10%.

PS liposomes are easily generated in large batches and can be frozen without loss of activity. For all experiments described so far, fresh PS was produced before each experiment in order to maintain consistency. To be useful as a general tool to enhance virus infection, it would be more convenient to produce large quantities of PS liposomes and freeze them in aliquots. We found that PS liposomes had the same effects on cells whether they were made in large or small batches (data not shown). Therefore, we made PS in a few large batches and kept aliquots at either 4°C or –20°C. In two experiments, the liposomes kept at 4°C lost approximately 25% of their activity within 3 days. However, aliquots stored at –20°C retained their effectiveness for at least 30 days (data not shown). In fact, there was an additional twofold increase in the effectiveness of PS liposomes after being frozen, which persisted for the 30-day time course (results of two experiments [data not shown]).

PS treatment most likely affects virus fusion. This conclusion is supported by the fact that receptor levels and virus binding are minimally affected by PS treatment in a case where a large increase in infection is noted. Furthermore, the enhancement of infection occurred only for enveloped viruses and not for the two nonenveloped viruses tested. We do not believe that this enhancement is a charge effect relating to virus adsorption, such as that of Polybrene, since PS is negatively charged and anions have repeatedly been shown to reduce virus infection (4, 22, 38). There are many facets to virus fusion that could be influenced by a large increase in PS concentration in the plasma membrane, such as lipid packing, alterations in bilayer curvature, changes in membrane fluidity, and locally induced changes in the bilayer phase (for a review, see reference 33). Further biophysical studies will be required to elucidate the particular mechanism by which PS enhances virus fusion.

Our results demonstrate that an increase in cell surface levels of PS allows a corresponding increase in virus infection. Interestingly, PS is normally found primarily on the inner leaflet of the plasma membrane, and there are relatively low levels of PS found on the outside of cells (6, 41, 44). It is possible that the typical levels of PS in a cell are a rate-limiting factor affecting normal virus fusion.

Virus-cell fusion is a complex and incompletely understood process (for reviews, see references 5, 9, and 33). No role for PS in the fusion of enveloped viruses has been proposed so far, although there is evidence for postentry requirements of PS in Sindbis virus replication (18) and in mRNA capping of Semliki Forest virus (1). The presence of PS in the virion may play a supporting role in human immunodeficiency virus infection (7). Similarly, PS inclusion into Sendai virus virosomes allows an increased level of virosome/cell fusion (17). However, the level of phosphatidylserine in the target cell membrane has not been previously shown to play any role in virus entry. Our results indicate that PS plays a role in facilitating enveloped virus fusion and can be used as a general tool to increase infection rates.


arrow
ACKNOWLEDGMENTS
 
We thank Christine Halbert for providing the Ad.RSV-ßgal and CWCZn(AAV2) vectors, Neal Van Hoeven for generation of the NIH 3T3/RDR and Rat-2/Hyal2 cell lines and for various vector preparations, and the laboratories of Adam Geballe and Roland Strong for regular use of equipment.

This work was supported by NIH grants HL54881 and DK47754.


arrow
FOOTNOTES
 
* Corresponding author. Mailing address: Fred Hutchinson Cancer Research Center, 1100 Fairview Ave. N., Room C2-105, P.O. Box 19024, Seattle, WA 98109-1024. Phone: (206) 667-2890. Fax: (206) 667-6523. E-mail: dmiller{at}fhcrc.org. Back


arrow
REFERENCES
 
    1
  1. Ahola, T., A. Lampio, P. Auvinen, and L. Kaariainen. 1999. Semliki Forest virus mRNA capping enzyme requires association with anionic membrane phospholipids for activity. EMBO J. 18:3164-3172.[CrossRef][Medline]
    2. 2
  2. Amsterdam, A. 2003. Insertional mutagenesis in zebrafish. Dev. Dyn. 228:523-534.[CrossRef][Medline]
    3. 3
  3. Andree, H. A., C. P. Reutelingsperger, R. Hauptmann, H. C. Hemker, W. T. Hermens, and G. M. Willems. 1990. Binding of vascular anticoagulant alpha (VAC alpha) to planar phospholipid bilayers. J. Biol. Chem. 265:4923-4928.[Abstract/Free Full Text]
    4. 4
  4. Batra, R. K., J. C. Olsen, D. K. Hoganson, B. Caterson, and R. C. Boucher. 1997. Retroviral gene transfer is inhibited by chondroitin sulfate proteoglycans/glycosaminoglycans in malignant pleural effusions. J. Biol. Chem. 272:11736-11743.[Abstract/Free Full Text]
    5. 5
  5. Blumenthal, R., M. J. Clague, S. R. Durell, and R. M. Epand. 2003. Membrane fusion. Chem. Rev. 103:53-69.[CrossRef][Medline]
    6. 6
  6. Boon, J. M., and B. D. Smith. 2002. Chemical control of phospholipid distribution across bilayer membranes. Med. Res. Rev. 22:251-281.[CrossRef][Medline]
    7. 7
  7. Callahan, M. K., P. M. Popernack, S. Tsutsui, L. Truong, R. A. Schlegel, and A. J. Henderson. 2003. Phosphatidylserine on HIV envelope is a cofactor for infection of monocytic cells. J. Immunol. 170:4840-4845.[Abstract/Free Full Text]
    8. 8
  8. Chesebro, B., and K. Wehrly. 1985. Different murine cell lines manifest unique patterns of interference to superinfection by murine leukemia viruses. Virology 141:119-129.[CrossRef][Medline]
    9. 9
  9. Chizmadzhev, Y. A. 2004. The mechanisms of lipid-protein rearrangements during viral infection. Bioelectrochemistry 63:129-136.[CrossRef][Medline]
    10. 10
  10. Coil, D. A., and A. D. Miller. 2004. Phosphatidylserine is not the cell surface receptor for vesicular stomatitis virus. J. Virol. 78:10920-10926.[Abstract/Free Full Text]
    11. 11
  11. Cosset, F.-L., Y. Takeuchi, J.-L. Battini, R. A. Weiss, and M. K. L. Collins. 1995. High-titer packaging cells producing recombinant retroviruses resistant to human serum. J. Virol. 69:7430-7436.[Abstract]
    12. 12
  12. Davis, H. E., J. R. Morgan, and M. L. Yarmush. 2002. Polybrene increases retrovirus gene transfer efficiency by enhancing receptor-independent virus adsorption on target cell membranes. Biophys. Chem. 97:159-172.[CrossRef][Medline]
    13. 13
  13. Davis, H. E., M. Rosinski, J. R. Morgan, and M. L. Yarmush. 2004. Charged polymers modulate retrovirus transduction via membrane charge neutralization and virus aggregation. Biophys. J. 86:1234-1242.[Medline]
    14. 14
  14. Dirks, C., and A. D. Miller. 2001. Many nonmammalian cells exhibit postentry blocks to transduction by gammaretroviruses pseudotyped with various viral envelopes, including vesicular stomatitis virus G glycoprotein. J. Virol. 75:6375-6383.[Abstract/Free Full Text]
    15. 15
  15. Halbert, C. L., E. A. Rutledge, J. M. Allen, D. W. Russell, and A. D. Miller. 2000. Repeat transduction in the mouse lung by using adeno-associated virus vectors with different serotypes. J. Virol. 74:1524-1532.[Abstract/Free Full Text]
    16. 16
  16. Hu, W. S., and V. K. Pathak. 2000. Design of retroviral vectors and helper cells for gene therapy. Pharmacol. Rev. 52:493-511.[Abstract/Free Full Text]
    17. 17
  17. Kim, H. S., and Y. S. Park. 2002. Effect of lipid compositions on gene transfer into 293 cells using Sendai F/HN-virosomes. J. Biochem. Mol. Biol. 35:459-464.[Medline]
    18. 18
  18. Kuge, O., Y. Akamatsu, and M. Nishijima. 1989. Abortive infection with Sindbis virus of a Chinese hamster ovary cell mutant defective in phosphatidylserine and phosphatidylethanolamine biosynthesis. Biochim. Biophys. Acta 986:61-69.[Medline]
    19. 19
  19. Kuypers, F. A., R. A. Lewis, M. Hua, M. A. Schott, D. Discher, J. D. Ernst, and B. H. Lubin. 1996. Detection of altered membrane phospholipid asymmetry in subpopulations of human red blood cells using fluorescently labeled annexin V. Blood 87:1179-1187.[Abstract/Free Full Text]
    20. 20
  20. Landazuri, N., and J. M. Le Doux. 2004. Complexation of retroviruses with charged polymers enhances gene transfer by increasing the rate that viruses are delivered to cells. J. Gene Med. 6:1304-1319.[CrossRef][Medline]
    21. 21
  21. Le Doux, J. M., N. Landazuri, M. L. Yarmush, and J. R. Morgan. 2001. Complexation of retrovirus with cationic and anionic polymers increases the efficiency of gene transfer. Hum. Gene Ther. 12:1611-1621.[CrossRef][Medline]
    22. 22
  22. Le Doux, J. M., J. R. Morgan, R. G. Snow, and M. L. Yarmush. 1996. Proteoglycans secreted by packaging cell lines inhibit retrovirus infection. J. Virol. 70:6468-6473.[Abstract]
    23. 23
  23. Manning, J. S., A. J. Hackett, and N. B. Darby, Jr. 1971. Effect of polycations on sensitivity of BALB-3T3 cells to murine leukemia and sarcoma virus infectivity. Appl. Microbiol. 22:1162-1163.[Medline]
    24. 24
  24. Miller, A. D., and C. Buttimore. 1986. Redesign of retrovirus packaging cell lines to avoid recombination leading to helper virus production. Mol. Cell. Biol. 6:2895-2902.[Abstract/Free Full Text]
    25. 25
  25. Miller, A. D., J. V. Garcia, N. von Suhr, C. M. Lynch, C. Wilson, and M. V. Eiden. 1991. Construction and properties of retrovirus packaging cells based on gibbon ape leukemia virus. J. Virol. 65:2220-2224.[Abstract/Free Full Text]
    26. 26
  26. Miller, A. D., and G. J. Rosman. 1989. Improved retroviral vectors for gene transfer and expression. BioTechniques 7:980-990.[Medline]
    27. 27
  27. Miller, D. G., R. H. Edwards, and A. D. Miller. 1994. Cloning of the cellular receptor for amphotropic murine retroviruses reveals homology to that for gibbon ape leukemia virus. Proc. Natl. Acad. Sci. USA 91:78-82.[Abstract/Free Full Text]
    28. 28
  28. Nieva, J. L., S. Nir, A. Muga, F. M. Goni, and J. Wilschut. 1994. Interaction of the HIV-1 fusion peptide with phospholipid vesicles: different structural requirements for fusion and leakage. Biochemistry 33:3201-3209.[CrossRef][Medline]
    29. 29
  29. Rafalski, M., J. D. Lear, and W. F. DeGrado. 1990. Phospholipid interactions of synthetic peptides representing the N-terminus of HIV gp41. Biochemistry 29:7917-7922.[CrossRef][Medline]
    30. 30
  30. Rai, S. K., J. C. DeMartini, and A. D. Miller. 2000. Retrovirus vectors bearing jaagsiekte sheep retrovirus Env transduce human cells by using a new receptor localized to chromosome 3p21.3. J. Virol. 74:4698-4704.[Abstract/Free Full Text]
    31. 31
  31. Rai, S. K., F.-M. Duh, V. Vigdorovich, A. Danilkovitch-Miagkova, M. I. Lerman, and A. D. Miller. 2001. Candidate tumor suppressor HYAL2 is a glycosylphosphatidylinositol (GPI)-anchored cell-surface receptor for jaagsiekte sheep retrovirus, the envelope protein of which mediates oncogenic transformation. Proc. Natl. Acad. Sci. USA 98:4443-4448.[Abstract/Free Full Text]
    32. 32
  32. Rasko, J. E., J. L. Battini, R. J. Gottschalk, I. Mazo, and A. D. Miller. 1999. The RD114/simian type D retrovirus receptor is a neutral amino acid transporter. Proc. Natl. Acad. Sci. USA 96:2129-2134.[Abstract/Free Full Text]
    33. 33
  33. Rawat, S. S., M. Viard, S. A. Gallo, A. Rein, R. Blumenthal, and A. Puri. 2003. Modulation of entry of enveloped viruses by cholesterol and sphingolipids. Mol. Membr. Biol. 20:243-254.[CrossRef][Medline]
    34. 34
  34. Siegel, D. P., and R. M. Epand. 1997. The mechanism of lamellar-to-inverted hexagonal phase transitions in phosphatidylethanolamine: implications for membrane fusion mechanisms. Biophys. J. 73:3089-3111.[Medline]
    35. 35
  35. Stuart, M. C., C. P. Reutelingsperger, and P. M. Frederik. 1998. Binding of annexin V to bilayers with various phospholipid compositions using glass beads in a flow cytometer. Cytometry 33:414-419.[CrossRef][Medline]
    36. 36
  36. Swairjo, M. A., N. O. Concha, M. A. Kaetzel, J. R. Dedman, and B. A. Seaton. 1995. Ca(2+)-bridging mechanism and phospholipid head group recognition in the membrane-binding protein annexin V. Nat. Struct. Biol. 2:968-974.[CrossRef][Medline]
    37. 37
  37. Tait, J. F., D. Gibson, and K. Fujikawa. 1989. Phospholipid binding properties of human placental anticoagulant protein-I, a member of the lipocortin family. J. Biol. Chem. 264:7944-7949.[Abstract/Free Full Text]
    38. 38
  38. Toyoshima, K., and P. K. Vogt. 1969. Enhancement and inhibition of avian sarcoma viruses by polycations and polyanions. Virology 38:414-426.[CrossRef][Medline]
    39. 39
  39. Van Hoeven, N. S., and A. D. Miller. 2005. Improved enzootic nasal tumor virus pseudotype packaging cell lines reveal virus entry requirements in addition to the primary receptor Hyal2. J. Virol. 79:87-94.[Abstract/Free Full Text]
    40. 40
  40. Wallis, C., and J. L. Melnick. 1968. Mechanism of enhancement of virus plaques by cationic polymers. J. Virol. 2:267-274.[Abstract/Free Full Text]
    41. 41
  41. Williamson, P., and R. A. Schlegel. 1994. Back and forth: the regulation and function of transbilayer phospholipid movement in eukaryotic cells. Mol. Membr. Biol. 11:199-216.[Medline]
    42. 42
  42. Wilson, C. B., L. J. Embree, D. Schowalter, R. Albert, A. Aruffo, D. Hollenbaugh, P. Linsley, and M. A. Kay. 1998. Transient inhibition of CD28 and CD40 ligand interactions prolongs adenovirus-mediated transgene expression in the lung and facilitates expression after secondary vector administration. J. Virol. 72:7542-7550.[Abstract/Free Full Text]
    43. 43
  43. Yee, J. K., T. Friedmann, and J. C. Burns. 1994. Generation of high-titer pseudotyped retroviral vectors with very broad host range. Methods Cell Biol. 43:99-112.
    44. 44
  44. Zwaal, R. F., and A. J. Schroit. 1997. Pathophysiologic implications of membrane phospholipid asymmetry in blood cells. Blood 89:1121-1132.[Free Full Text]

Journal of Virology, September 2005, p. 11496-11500, Vol. 79, No. 17
0022-538X/05/$08.00+0     doi:10.1128/JVI.79.17.11496-11500.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Johannsdottir, H. K., Mancini, R., Kartenbeck, J., Amato, L., Helenius, A. (2009). Host Cell Factors and Functions Involved in Vesicular Stomatitis Virus Entry. J. Virol. 83: 440-453 [Abstract] [Full Text]  

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrowReprints and Permissions
Right arrow Copyright Information
Right arrow Books from ASM Press
Right arrow MicrobeWorld
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Coil, D. A.
Right arrow Articles by Miller, A. D.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Coil, D. A.
Right arrow Articles by Miller, A. D.

Copyright © 2009 by the American Society for Microbiology.   For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»