Previous Article | Next Article 
Journal of Virology, May 1999, p. 3975-3985, Vol. 73, No. 5
AIDS Research Center and Infectious Disease Unit,
Massachusetts General Hospital and Harvard Medical School, Boston,
Massachusetts 021141; Northwestern
University School of Medicine, Chicago, Illinois
606112; Santa Fe Institute, Santa
Fe, New Mexico 87501, and Los Alamos National Laboratory, Los
Alamos, New Mexico 875453; University of
Massachusetts Medical School, Worcester, Massachusetts
016054; Department of Pediatrics, Baylor
College of Medicine, Houston, Texas 770305;
Children's Diagnostic & Treatment Center, Fort Lauderdale,
Florida 333016; Bronx-Lebanon
Hospital Center, Bronx, New York 104577;
Department of Pediatrics, University of California San
Francisco Medical Center, San Francisco, California
941438; and Aaron Diamond AIDS Research
Center, The Rockefeller University, New York, New York
100169
Received 11 September 1998/Accepted 27 January 1999
Host immunologic factors, including human immunodeficiency virus
(HIV)-specific cytotoxic T lymphocytes (CTL), are thought to contribute
to the control of HIV type 1 (HIV-1) replication and thus delay disease
progression in infected individuals. Host immunologic factors are also
likely to influence perinatal transmission of HIV-1 from infected
mother to infant. In this study, the potential role of CTL in
modulating HIV-1 transmission from mother to infant was examined in 11 HIV-1-infected mothers, 3 of whom transmitted virus to their offspring.
Frequencies of HIV-1-specific human leukocyte antigen class
I-restricted CTL responses and viral epitope amino acid sequence
variation were determined in the mothers and their infected infants.
Maternal HIV-1-specific CTL clones were derived from each of the
HIV-1-infected pregnant women. Amino acid substitutions within the
targeted CTL epitopes were more frequently identified in transmitting
mothers than in nontransmitting mothers, and immune escape from CTL
recognition was detected in all three transmitting mothers but in only
one of eight nontransmitting mothers. The majority of viral sequences
obtained from the HIV-1-infected infant blood samples were susceptible
to maternal CTL. These findings demonstrate that epitope amino acid
sequence variation and escape from CTL recognition occur more
frequently in mothers that transmit HIV-1 to their infants than in
those who do not. However, the transmitted virus can be a CTL
susceptible form, suggesting inadequate in vivo immune control.
The expanding human immunodeficiency
virus type 1 (HIV-1) epidemic is fueled in part by perinatal
transmission of the virus. Although antiviral therapy in the peripartum
period significantly diminishes transmission (13), rates of
40% or higher occur in populations without ready access to
pharmacological interventions (5, 47). The majority of these
transmissions occur at or near the time of delivery (17, 18,
44). A better understanding of the factors contributing to
perinatal transmission is key to designing new therapies that prevent
transmission and is likely to provide insights regarding disease
pathogenesis as well (45).
Perinatal HIV-1 transmission is typified by selection of a particular
genotypic variant in the infected infant (46, 55). This
selective virus transmission is compatible with several alternative hypotheses (61). First, the predominant viral sequence
variant in the infant may be derived from an antigenically distinct
variant in the mother that escaped the constraints of a critical immune surveillance mechanism. Second, transmission could be a stochastic phenomenon whereby the infants' viral sequences are acquired by random
transmission of a limited number of virions or infected cells either at
the time of birth or during gestation. While this genotypic variant may
have represented a major form in the mother at the time of
transmission, this variant later could become a minor form in the
mother because of genetic evolution. Lastly, the persistent form of
virus in the infant may reflect differences in cell tropism,
replicative capabilities, or chemokine coreceptor usage for viral entry
(29, 43) that permit selective transmission or amplification
of a particular genotypic variant within the infant (61).
Results from studies designed to elucidate the mechanism underlying
perinatal HIV-1 transmission are conflicting. Prolonged exposure to
infected cervicovaginal secretions is associated with transmission
(41), but there are conflicting data regarding the relative
contributions of high levels of virus in maternal peripheral blood
(6, 11, 16, 19, 56, 58), levels of maternal neutralizing
antibodies (14, 30, 34, 52, 53), and the ability to secrete
inflammatory cytokines in response to viral peptides (9).
Host immunologic factors have also been proposed as a factor in
perinatal HIV-1 transmission and could possibly explain the observed
selective transmission (54). The infant's viruses may be
derived from an antigenically distinct variant arising in the mother
that escapes a critical immune surveillance mechanism, possibly as a
consequence of amino acid changes in B-cell (1, 23) or
cytotoxic T-lymphocyte (CTL) epitopes (48, 59) that abrogate
or antagonize immune recognition. These escape variants would,
therefore, have a survival advantage that might facilitate their transmission.
Emerging data indicate that CTL exert significant immune pressure in
HIV-1 infection, suggesting that this response might participate in
modulating transmission. A temporal association between the emergence
of HIV-1-specific CTL and a drop in plasma viremia has been observed
during primary infection (3, 39), and strong CTL responses
are maintained in persons with long-term nonprogressing HIV-1 infection
and low viral loads (27, 35, 51, 60). CTL responses have
also been associated with the emergence of immune escape due to
mutations within CTL epitopes, both during primary infection
(4) and with disease progression (24, 60),
although the numbers of subjects studied has been small, and
appropriate controls have been difficult to identify. The role of
immune escape in disease pathogenesis remains controversial, as other
studies have failed to identify escape as a means of disease
progression (28). Although a vigorous human leukocyte antigen (HLA) class I-restricted immune response has been associated with a low rate of development of disease and increased time of survival, it is not clear why this host defense is ultimately unable to
eliminate the virus and prevent disease progression. Within the
infected host, sequestration of viruses in immunologically privileged
sites, lack of adequate T helper cell function (8), down
modulation of major histocompatibility complex (MHC) antigen expression
(12), and amino acid sequence variation in well-defined class I-restricted CTL epitopes (48, 59) have been
postulated to explain this apparent paradox (63). Selection
for a virus population harboring amino acid sequence changes in
residues within or near class I-restricted epitopes could facilitate
CTL escape by disrupting correct endogenous processing of the antigen,
HLA binding, and/or optimal recognition of the peptide-HLA complex by
T-cell receptors (48).
Whether transmission per se is associated with escape from CTL
recognition has yet to be determined conclusively. We reasoned that the
question of whether CTL serve as an important immunological defense
could be addressed experimentally in a setting in which transmission
could be readily monitored and in which the transmitted virus could be
examined. We therefore evaluated the maternal HIV-1-specific CTL
responses in a cohort of transmitting and nontransmitting mothers
(6). Mothers enrolled in the Ariel Cohort for the Prevention of HIV Transmission from Mother to Infant were evaluated for the epitope specificity of their clonal CTL responses at the time of
delivery. Additionally, autologous viral sequences were amplified, at
endpoint dilution, from peripheral blood obtained from each HIV-1-infected mother and her infected infant at or within days of the
time of delivery to screen for evidence of sequence variation within
the defined CTL epitopes and to determine the effects of such amino
acid sequence changes on recognition by maternal CTL. Finally, we
evaluated the virus obtained from the infants for recognition by the
maternal CTL response as a correlate of immune escape and a potential
mechanism underlying perinatal HIV-1 transmission.
Subjects.
Study subjects were selected from a cohort of
HIV-1-infected pregnant women enrolled in the Ariel Project for the
Prevention of Transmission of HIV from Mother to Infant and monitored
throughout their pregnancies. The Ariel cohort enrolled mothers at the
seven clinical sites located in Fort Lauderdale, Fla.; Newark, N.J.; Houston, Tex.; Bronx, N.Y.; Stamford, Conn.; Worcester, Mass.; and New
Orleans, La. Subjects included in this study were prospectively monitored at the Houston, Bronx, Worcester, and Fort Lauderdale clinical sites. The characteristics of the Ariel cohort are described elsewhere (6). Among the total of 204 HIV-1-infected
pregnant women enrolled in the study, we selected 3 of the 8 women who infected their infants during gestation and 8 of the 185 women who did
not, based on sample availability and the detection of an
immunodominant CTL response. The numbers of copies of virion-associated RNA per milliliter of plasma were quantified for each woman at the time
peripheral blood was obtained for T-cell cloning, a visit corresponding
to the time of delivery, by the AMPLICOR HIV-1 Monitor Test (Roche
Diagnostic Systems, Inc., Branchburg, N.J.) as instructed by the
manufacturer. The infection status of the infants born to these mothers
was determined by the presence of HIV-1 proviral DNA in peripheral
blood mononuclear cells by using a PCR-based assay and by viral
coculture at delivery and at regular intervals thereafter.
Cell lines.
Epstein-Barr virus-transformed B-lymphoblastoid
cell lines (B-LCL) were established from the peripheral blood
mononuclear cells (PBMC) of each subject and maintained as previously
described (57) in RPMI 1640 medium (Sigma, St. Louis, Mo.)
containing 20% heat-inactivated fetal calf serum (Sigma). RPMI 1640 medium used for all cell lines was supplemented with
L-glutamine (2 mM), penicillin (50 U/ml), streptomycin (50 µg/ml), and HEPES (10 mM). Additional allogeneic B-LCL used in HLA
restriction experiments were established and maintained in a similar fashion.
HLA class I typing.
HLA typing was performed by using a
standard lymphocytotoxicity assay and confirmed in some cases with a
PCR-based allele-specific molecular typing assay (24).
Recombinant vaccinia virus constructs.
Recombinant vaccinia
viruses expressing the full-length HIV-1 gp160 gene (VPE16) as well as
serial truncations of the HIV-1 envelope gene (VPE17-22) were provided
by P. Earl and B. Moss. Recombinant vaccinia viruses expressing HIV-1
p55gag (vAbT141), p24gag (vAbT286),
p17gag (vAbT228), HIV-1 Pol (vAbT204), HIV-1 Nef (vT23),
and wild-type control (NYCBH) were provided by Therion Biologics
(Cambridge, Mass.). Stocks of recombinant vaccinia viruses were
adjusted to approximately 109 PFU/ml, stored in aliquots at
HIV-1 peptide synthesis.
Synthetic peptides corresponding to
the HIV-1 HXB10 sequence (26), consisting of a series of
peptides 25 amino acids in length that overlapped by 8 amino acids,
were synthesized and purified by Multiple Peptide Systems (San Diego,
Calif.) as described previously (31). Peptides were
synthesized as COOH-terminal amides unless otherwise noted. Smaller
peptides of 8 to 15 amino acids used for fine mapping were synthesized
as free acids on an automated peptide sequencer (Applied Biosystems
model 420A). Lyophilized peptides were reconstituted at 2 mg/ml in
sterile distilled water with 10% dimethyl sulfoxide (Sigma) and 1% 1 mM dithiothreitol (Sigma).
Isolation of HIV-1-specific CTL clones and lines.
CTL clones
were isolated and maintained as described previously (57).
Briefly, PBMC were obtained by separation of whole blood on a
Ficoll-sodium diatrozoate gradient (Sigma) and were plated at
concentrations ranging from 10 to 100 cells per well of a 96-well
plate. Cells were maintained with a feeder solution containing
106 irradiated allogeneic PBMC per ml from uninfected
subjects in RPMI 1640 with 10% heat-inactivated fetal calf serum
supplemented with 100 U of human recombinant interleukin-2 (Hoffmann-La
Roche, Nutley, N.J.) per ml. The CD3-specific monoclonal antibody (MAb) 12F6 (62) was added at a final concentration of 0.1 µg/ml
to stimulate T-cell proliferation. Cells from wells demonstrating growth were restimulated further as previously described
(32) and then tested for cytolytic activity against
autologous target cells infected with recombinant vaccinia viruses
expressing HIV-1 genes approximately 4 to 6 weeks after the initial
cloning. T-cell clones exhibiting HIV-1-specific CTL activities were
restimulated every 14 to 21 days with anti-CD3 MAb and irradiated
allogeneic PBMC.
Flow cytometric analysis.
Cells were incubated with
fluorescent probe-conjugated anti-CD3/anti-CD4, anti-CD3/anti-CD8, and
anti-mouse immunoglobulin G2b (IgG2b)/IgG1 MAbs as controls (Coulter
Electronics, Hialeah, Fla.), singly or in combination. Samples of
stained cells were analyzed with a FACScan flow cytometer (Becton
Dickinson and Co., Mountain View, Calif.) as described previously
(32).
Cytotoxicity assay.
Target cells consisted of B-LCL infected
with recombinant vaccinia viruses or preincubated with synthetic HIV-1
peptides. Target B-LCL were infected with recombinant vaccinia virus as previously described (59), and labeled with 65 to 100 µCi
of [51CrO4] Na2 (New England
Nuclear, North Billerica, Mass.) overnight, and then washed three times
with RPMI 1640 medium. Peptide-sensitized target cells were obtained by
incubating 2 × 106 to 3 × 106 B-LCL
with peptide for 60 min during 51Cr labeling. Cytolytic
activity was determined in a standard 4-h 51Cr release
assay using U-bottom microtiter plates containing 5 × 103 targets per well. Assays were performed in duplicate.
Supernatant fluids were harvested onto 96-well plates containing solid
scintillate, allowed to dry overnight, and then counted in a TopCount
microplate scintillation counter (Packard Instrument Co., Meriden,
Conn.). Maximum release was determined by lysis of targets in detergent (1% Triton X-100; Sigma). Percent lysis was determined as 100 × [(experimental release In vitro amplification of epitope-encoding regions and viral
sequence analysis.
To explore the relationship between CTL
recognition or escape and genetic diversity within class I
MHC-restricted epitopes, we assessed the diversity of viral sequences
within these individuals by examining proviral sequences spanning
selected fragments of the gag, pol,
env, and nef coding regions. PCR was used to
amplify proviral DNA at endpoint dilution in cells obtained from the
index visit near the time of parturition. In some cases only short
fragments spanning just the regions of interest were sequenced, but in
other cases longer sequences were generated, and those sequences were incorporated into the phylogenetic analysis shown in Fig. 3. The positions of the oligonucleotide primers are numbered according to the
HXB2 isolate in the human retroviruses and AIDS database (37). LTRF1.1 (nucleotides 518 to 542;
5'-TAAGCCTCAATAAAGCTTGCCTTG-3'), LTRF2.1 (nucleotides 574 to
542; 5'-TGTGACTCTGGTA[A/G]CTAGAGATCCC-3'), LTRF3.1
(nucleotides 626 to 650; 5'-TCTCTAGCAGTGCGCCCCGAACAGG-3'), VACGAGR1 (nucleotides 2314 to 2338;
5'-TCTGCTCCTGTATCTAATAGAGCTT-3'), VACGAGR2 (nucleotides 2375 to 2399; 5'-TCC[C/T]CCTATCATTTTTGGTTTCCAT-3'), VACGAGR3
(nucleotides 2468 to 2492; 5'-TGTAGGTCCTACTAATACTGTACCT-3'), and CTLPOLF1 (nucleotides 2318 to 2341;
5'-TCTATTAGATACAGGAGCAGATGA-3') are the gag
amplification primers. The outer sets of gag amplification primers and their amplicon sizes are LTRF1.1 and VACGAGR3 (1,974 bp),
LTRF1.1 and VACGAGR2 (1,881 bp), LTRF2.1 and VACGAGR3 (1,918 bp), and
LTRF2.1 and VACGAGR2 (1,825 bp). The inner sets of gag amplification primers and their amplicon sizes are LTRF2.1 and VACGAGR2
(1,825 bp), LTRF2.1 and VACGAG1 (1,764 bp), LTRF3.1 and VACGAGR1 (1,712 bp), and LTRF3.1 and VACGAGR2 (1,974 bp). CTLPOLF2 (nucleotides 2391 to
2415; 5'-TAGG[G/A]GGAATTGGAGGTTTTATCA-3'), CTLPOLF3
(nucleotides 2467 to 2490; 5'-TAGGTACAGTATTAGTAGGACCTA-3'), CTLPOLR1 (nucleotides 4060 to 4083;
5'-TATCTGGTTGTGCTTGAATGATTC-3'), CTLPOLR2 (nucleotides 4321 to 4344; 5'-TGGCTACTATTTCTTTTGCTACTA-3'), and
CTLPOLR3 (nucleotides 4649 to 4673;
5'-TTGACTTTGGGGATTGTAGGGAAT-3') are the pol
amplification primers. The outer sets of pol amplification primers and their amplicon sizes are CTLPOLF1 and CTLPOLR3 (2,355 bp),
CTLPOLF1 and CTLPOLR2 (2,355 bp), CTLPOLF2 and CTLPOLR3 (2,282 bp), and CTLPOLF2 and CTLPOLR2 (1,953 bp). The outer sets of
pol amplification primers and their amplicon sizes are
CTLPOLF2 and CTLPOLR2 (1,953 bp), CTLPOLF2 and CTLPOLR2 (1,953 bp),
CTLPOLF2 and CTLPOLR1 (1,692 bp), CTLPOLF3 and CTLPOLR2 (1,877 bp), and CTLPOLF3 and CTLPOLR1 (1,616 bp). KKE5P3 (nucleotides 6189 to 6213;
5'-GCGACCCGGGTTGATAGA[C/A]TAA[T/G]AGAAAGAGCAGA-3') and
KKE3P1 (nucleotides 8809 to 8833;
5'-GCGAGAATTCATCC[C/A]AC[T/C]A[C/T]ACTAC[T/G]TTTTGACCA-3') are the env amplification primers. The input DNA
molecules were quantified by PCR using serial fivefold dilutions.
Twenty 5-µl samples of endpoint-diluted DNA were amplified in a
100-µl reaction mix containing 0.2 µM outer primer pair as
described elsewhere (22). PCR was performed with a
Perkin-Elmer/Cetus 9600 automated thermal cycler programmed for for 35 cycles at 98°C for 10 s, 50°C for 30 s, and 72°C for 3 min, with a final extension at 72°C for 10 min. A 5-µl sample was
reamplified from each reaction in a 100-µl reaction mix containing
0.2 µM inner primer pair by means of the same cycle profile as
specified above. HIV-1-negative cell DNA and reagent controls were run
in parallel (40). PCR product DNA was resolved by
electrophoresis on a 1.0% NuSieve GTG gel (FMC BioProducts). The
correctly sized band was purified from the agarose gel by
electroelution using gene capsules (Geno Technologies, Inc.) and
inserted into pCR 2.1 (Invitrogen), using the principles of TA cloning.
One microgram of the double-stranded DNA template was sequenced in both
forward and reverse directions, using the respective gag,
pol, and env internal primers with the use of dideoxynucleoside triphosphates (Dye-Deoxy terminators) and analyzed with a model 377 sequencing system (Applied Biosystems) as described elsewhere (22).
Phylogenetic reconstruction and statistical analysis.
The
sequences were hand aligned by using a modified version of the MASE
program (20). The sequences were gap stripped
(42), and phylogenetic analysis was done by the
neighbor-joining, bootstrap, and maximum-likelihood methods from the
PHYLIP package (21). Statistics were done with the Splus
package, version 3.4 (MathSoft, Inc.).
Nucleotide sequence accession numbers.
The viral sequences
reported in this study are available in GenBank, under accession no.
AF121459 to AF121669.
Characterization of the maternal CTL response.
Subjects from
the Ariel cohort were randomly screened for CTL responses to HIV at or
near the time of delivery. Three HIV-1-infected mothers who infected
their infants and eight mothers who did not transmit virus were
selected for detailed study on the basis of sample availability and the
ability of their established T-cell clones to recognize HIV-1-specific
antigens. The ranges of viral loads measured at delivery among the two
groups were not statistically distinguishable, in accord with the small
sample size. There was also no discernible difference between the two
groups in terms of intrapartum azidothymidine (AZT) use, but those
mothers who infected their infants in our study tended to have higher
peripheral CD4+ T-cell counts (Table
1).
0022-538X/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Frequent Detection of Escape from Cytotoxic T-Lymphocyte
Recognition in Perinatal Human Immunodeficiency Virus (HIV) Type
1 Transmission: the Ariel Project for the Prevention of
Transmission of HIV from Mother to Infant
ABSTRACT
Top
Abstract
Introduction
Materials and Methods
Results
Discussion
References
INTRODUCTION
Top
Abstract
Introduction
Materials and Methods
Results
Discussion
References
MATERIALS AND METHODS
Top
Abstract
Introduction
Materials and Methods
Results
Discussion
References
80°C, and thawed immediately prior to use.
spontaneous release)/(maximum
release spontaneous release)]. Spontaneous release values were
less than 30% of maximal release for all reported assays.
RESULTS
Top
Abstract
Introduction
Materials and Methods
Results
Discussion
References
TABLE 1.
Characteristics of mothers
|
|
|
Genetic variation within targeted HLA class I-restricted epitopes. Having identified the HIV-1-specific epitopes targeted by the mothers, we next evaluated viral sequence variation within the specific HLA class I-restricted epitope and determined the effects of sequence variation on CTL recognition. We analyzed the viral sequences within each of the infected mothers by examining proviral sequences spanning the relevant portions of the gag, pol, env, and nef coding regions of the viral genome from peripheral blood samples obtained at the time of delivery. The target sequences were amplified by nested PCR at endpoint dilution to obviate resampling of any single template molecule (38). Product DNAs were inserted into pAMP by UDG cloning, and 5 to 17 clones from each sample were sequenced in both directions. Several of the epitopes were sequenced only across a short fragment, spanning the epitope, while others were sequenced embedded in long sequences, augmented by additional short fragments. Those epitope sequences that were obtained embedded in longer fragments were suitable for phylogenetic analysis. In all cases where longer sequences were available, phylogenetic reconstructions of the mothers' viral sequences showed distinct clusters corresponding to the respective nontransmitting mother, or mother-infant pair, indicating absence of PCR-product contamination and establishing epidemiological linkage between the transmitting mother and her infant, and proving that there were no sample mix-ups (see Fig. 3). BLAST searches against GenBank gave no indication of any contamination problems.
The extent of genetic diversity within an A3-restricted p17 epitope differed for one mother who infected her infant (11113) compared to another who did not (19143) (Tables 2 and 3). While the A3-restricted p17 epitope sequence KIRLRPGGK was highly conserved among the genetic variants obtained from nontransmitting mother 19143, amino acid substitutions were found within the same A3-restricted p17 epitope for transmitting mother 11113. The predominant epitope sequence had a lysine-to-arginine (K-to-R) substitution at the carboxyl terminus, an important residue for peptide binding to A3 (15, 50), and was not recognized by the CTL from transmitting mother 11113 (Fig. 2) or by the CTL from nontransmitting mother 19143 (data not shown). Likewise, among the other transmitting mothers 19142 and 19145, a high proportion of epitope variants were found within at least one of the epitopes targeted. Overall, four of the seven defined HLA class I-restricted epitopes targeted by T-cell clones obtained from transmitters 11113, 19142, and 19145 had amino acid changes, with a range of two to five variant forms of the epitope detected. Among the eight nontransmitting mothers, three of the eight defined HLA class I-restricted epitopes targeted by T-cell clones had amino acid changes, and there were never more than two variant forms present.
|
, respectively, in Tables 2 and 3,
based on Fig. 2). Based on a tally of observed variant sequences and
CTL reactivity, the transmitting mothers have 41 ++ reactive epitopes,
12 +, and 28 , while the nontransmitting mothers have 93 ++, 3 +, and
8 . A 3 × 2 contingency table indicates that there is a low
probability that such distinctive sets of observed variants could have
occurred by chance alone (P 
10
4).
Maternal CTL recognition of transmitted viruses. We next sought to determine if CTL clones derived from the mother recognized the defined HLA class I-restricted cognate epitope in the infant's sequences. Peptides corresponding to the variant epitopes found in the infants were synthesized and then tested for recognition by their mother's CTL clones. Two of the three infants had defined epitope sequences with mutations that conferred escape from maternal CTL recognition, although in all three infants the most prevalent epitope sequences were CTL susceptible (Table 2 and Fig. 2A). Interestingly, none of the infant genetic escape variants was found in the mother at the time of peripheral blood sampling. Furthermore, although in several cases CTL escape variants were the predominant sequences isolated in the mother, those escape sequences were not detected in the respective infants (Table 2 and Fig. 2A). Instead, a minor maternal variant sequence, well recognized by maternal CTL, was often the major epitope sequence isolated in the infant. On the whole, more than 90% of the infant epitope sequences tested were recognized by maternal CTL.
One possible explanation for the presence of CTL-susceptible virus in the infant is that reversion to a more fit virus may have occurred in vivo in the infant in the absence of immune pressure. To address this issue, phylogenetic analysis was performed on one of the mother-infant pairs in which adequately long sequences for careful analysis could be obtained. The clustering patterns of the sequences from the mother-infant pair (mother 11113 and infant 11213) indicate that the unusual, CTL-susceptible form found in the mother was actually the transmitted variant of the virus, rather than that the back-mutation to wild type from a CTL-resistant form occurred in the infant (Fig. 3B). Thus, although CTL escape was significantly associated with transmission, the actual transmitted virus was apparently not an escape variant.
|
| |
DISCUSSION |
|---|
|
Top
Abstract
Introduction
Materials and Methods
Results
Discussion
References
|
|---|
This study is unique in providing a detailed molecular analysis of the HIV-1-specific epitopes targeted by the CTL response in mothers who transmitted the virus to their offspring, in their infected infants, and in HIV-1-infected mothers who did not infect their offspring. Within the limitations of our data set, we found an association between greater viral sequence variation in well-defined, HLA class I-restricted maternal epitopes and the propensity for the mother to transmit the virus during gestation. These results further indicate that viral escape from CTL recognition is frequently detected in mothers who transmit virus to their infants and that minor susceptible variants in the mother can become the major variant transmitted to the infant. In contrast to the immune escape detected in the transmitting mothers, lack of CTL recognition of in vivo virus was infrequently detected in nontransmitting mothers. Four of the seven CTL clones derived from the three mothers who transmitted virus to their offspring, and only one CTL clone derived from a mother who did not, failed to recognize autologous viral variant sequences within cognate HLA class I-restricted epitopes. Consistent with selective perinatal HIV-1 transmission (61), a relatively homogeneous population of genetic variants was found in peripheral blood obtained from the infant after delivery, contrasting with the higher genetic diversity found in the peripheral blood obtained from the mothers. The predominant infant genotype often represented a minor maternal viral variant. Despite the presence of multiple immune escape variants in the transmitting mothers, the predominant viral strain in each of the three infants contained an epitope sequence well recognized by the maternal CTL response. One possible explanation for the presence of CTL-susceptible viral epitope variants in the infants is reversion of the transmitted escape variants to susceptible virus due to lack of persistent immune pressure in the infants. Evidence against this hypothesis may be found in the evaluation of mother-infant pair 11113-11213. In this case, viral sequences susceptible to maternal CTL predominated in the infant despite the predominance of escape variants in the mother. Since infant 11213 did not share either of the HLA class I alleles that restricted transmitting mother 11113 CTL (Table 2), this infant would be unlikely to develop CTL that could maintain immune pressure through the epitopes recognized by those maternal CTL. This lack of immune pressure in the infant might be expected to allow for a reversion of the transmitted virus that carried CTL escape sequences to a more fit virus that carried CTL-susceptible epitope sequences. However, the phylogenetic analysis depicted in Fig. 3 clearly indicates that the virus transmitted from 11113 to 11213 was the CTL-susceptible form, despite the predominance of escape variants in the mother. These data add to a number of studies implicating escape from CTL recognition in the pathogenesis of HIV infection (4, 24, 48, 59, 60) but indicate that factors other than simple nonrecognition of the cognate epitope must be involved in perinatal transmission.
Selection for escape variants with mutations within well-defined HLA class I-restricted CTL epitopes can result in loss of reactivity of the epitope and act as a selective force that drives the evolution of the virus (4, 48, 49). This has been observed in acute infection when mutations within early targeted epitopes leads to loss of recognition (4, 49) and in chronic infection when mutations within CTL epitopes have been associated with more rapid disease progression (24). In addition, vastly different rates of disease progression found in a set of HLA-identical siblings infected by a common batch of contaminated factor VIII was associated with different patterns of amino acid changes in HLA class I-restricted epitopes and intensity of the CTL response (25). These studies and the present study indicate that immune selection pressure is exerted by CTL. Our study is unique in demonstrating that despite the presence of CTL escape variants in the mother, the virus that is established in the infant is a maternal CTL-susceptible form.
The increased frequency of CTL escape mutations in transmitting compared to nontransmitting mothers suggests a role for the CTL response in the transmission process, but the transmission of CTL-susceptible forms is counterintuitive. A number of factors could account for this. Viral variants can lead to antagonism of existing CTL responses (2, 36), but we were unable to find any evidence of this phenomenon (59a). Alternatively, the increased frequency of variants in the transmitting mothers may reflect an overall impairment of the ability to effectively contain viral replication. Critical additional CTL responses directed at type-specific epitopes present in vivo may be immune escape variants which went undetected because only laboratory strains of virus could be used for screening. Also, as these studies examined CTL and viruses derived from PBMC, it is possible that tissue-specific responses not represented in the peripheral blood are present in other relevant compartments (i.e., placenta or birth canal). Nevertheless, the data clearly demonstrate that variation within CTL epitopes is more prominent in women who transmit virus to their infants. The rapid and mutation-prone replication of the virus produces a diverse population that can effectively counter host-mediated selection pressures and perpetuate infection within the host (10). Whereas the viral sequences derived from the mothers show an accumulation of mutations in CTL epitopes consistent with positive selection for change, the infants have relatively little evidence of selective pressure for change. Thus, progressive shifts in the virus population in the HIV-1-infected mother, in contrast to the presumed relative evolutionary stasis in the infant, likely contribute to the observed disparity in amino acid sequences of the epitopes matched between an HIV-1-infected infant and the mother.
Ideally this study would have been performed with mothers matched for the same HLA antigens and target epitopes, but this was not feasible even in the large cohort of HIV-1-infected pregnant women we examined. The small sample size was a necessary constraint imposed by the detailed characterizations performed in this study, and the subjects included were limited to those in whom CTL clones could be established and maintained for full characterization. CTL responses were detected only if they were cross-reactive with the reference strains of virus used for the vaccinia constructs; thus, additional CTL responses may have been present but not detected. Furthermore, testing against reference strain rather than autologous virus might bias the analysis toward conserved epitopes in regions with structural and functional constraints that are less likely to participate in immune evasion. Nevertheless, these studies found greater amino acid changes within well-defined MHC class I-restricted epitopes for HIV-1-infected mothers who transmitted the virus to their infants relative to those mothers who did not. Thus, despite these experimental limitations, which are also inherent to other epitope mapping studies, the data clearly demonstrate the occurrence of CTL immune escape in the context of perinatal HIV-1 transmission. In summary, our data indicate that CTL immune escape occurs in perinatal HIV-1 transmission and provide further evidence of CTL-mediated immune selection pressure in this infection. Although antiviral drug intervention has been shown to decrease perinatal transmission (13, 56), our results suggest that interventions designed to augment cellular immunity to the viruses present in vivo, and minimizing immune escape, might also prove beneficial.
| |
ACKNOWLEDGMENTS |
|---|
This work was supported by the Pediatric AIDS Foundation and Public Health Service grants HD-31756 and R37AI28568, through the Elizabeth Glaser Scientist Award (B.T.K., K.I., and R.A.K.), and a gift from an anonymous foundation.
We thank David McDonald of the Santa Fe Institute for his efforts at maintaining the PAF Ariel project database and for help with the genetic sequence analysis.
| |
FOOTNOTES |
|---|
* Corresponding author. Mailing address for Steven M. Wolinsky: Northwestern University School of Medicine, 303 E. Chicago Ave., Chicago, IL 60611. Phone: (312) 908-5210. Fax: (312) 908-4588. E-mail: s-wolinsky{at}nwu.edu. Mailing address for Bruce D. Walker: AIDS Research Center and Infectious Disease Unit, Massachusetts General Hospital and Harvard Medical School, Fruit Street, Boston, Massachusetts 02114. Phone: (617) 724-8332. Fax: (617) 726-4691. E-mail: bwalker{at}helix.mgh.harvard.edu.
Present address: Department of Medicine, University of Colorado
Health Sciences Center, Denver, CO 80262.
Present address: University of Texas Southwestern Medical School,
Dallas, Tex.
§ The Ariel Project is a Pediatric AIDS Foundation-sponsored project. Clinical site principal investigators include S.M.W., I.C.H., A.W., and K.L., as well as Russell B. Van Dyke (Tulane University of Medicine, New Orleans, La.), Arlene Bardeguez (UMD-New Jersey Medical School, Newark, N.J.), and Richard R. Viscarello (Maternal Fetal Care, P.C., Stamford, Conn.). Core investigators include B.T.K., B.D.W., and S.M.W., as well as David Ho and Rick Koup (Aaron Diamond AIDS Research Center, New York, N.Y.), Irvin Chen and Paul Krogstad, (University of California, Los Angeles), and James Mullins (University of Washington, Seattle). A.J.A. and S.C. are study coordinators. The Data Management Center is coordinated by B.T.K., David McDonald, and Robert Funkhouser.
| |
REFERENCES |
|---|
|
Top
Abstract
Introduction
Materials and Methods
Results
Discussion
References
|
|---|
| 1. |
Back, N. K.,
L. Smit,
M. Schutten,
P. L. Nara,
M. Tersmette, and J. Goudsmit.
1993.
Mutations in human immunodeficiency virus type 1 gp41 affect sensitivity to neutralization by gp120 antibodies.
J. Virol.
67:6897-6902 |
| 2. | Bertoletti, A., A. Sette, F. V. Chisari, A. Penna, M. Levrero, M. De Carli, F. Fiaccadori, and C. Ferrari. 1994. Natural variants of cytotoxic epitopes are T-cell receptor antagonists for antiviral cytotoxic T cells. Nature 369:407-410[Medline]. |
| 3. |
Borrow, P.,
H. Lewicki,
B. H. Hahn,
G. M. Shaw, and M. B. Oldstone.
1994.
Virus-specific CD8+ cytotoxic T-lymphocyte activity associated with control of viremia in primary human immunodeficiency virus type 1 infection.
J. Virol.
68:6103-6110 |
| 4. | Borrow, P., H. Lewicki, X. Wei, M. S. Horwitz, N. Peffer, H. Meyers, J. A. Nelson, J. E. Gairin, B. H. Hahn, M. B. Oldstone, and G. M. Shaw. 1997. Antiviral pressure exerted by HIV-1-specific cytotoxic T lymphocytes (CTLs) during primary infection demonstrated by rapid selection of CTL escape virus. Nat. Med. 3:205-211[Medline]. |
| 5. | Bryson, Y. J. 1996. Perinatal HIV-1 transmission: recent advances and therapeutic interventions. AIDS 10:S33-S42. |
| 6. | Cao, Y., P. Krogstad, B. T. Korber, R. A. Koup, M. Muldoon, C. Macken, J. L. Song, Z. Jin, J. Q. Zhao, S. Clapp, I. S. Chen, D. D. Ho, and A. J. Ammann. 1997. Maternal HIV-1 viral load and vertical transmission of infection: the Ariel Project for the prevention of HIV transmission from mother to infant. Nat. Med. 3:549-552[Medline]. |
| 7. | Centers for Disease Control and Prevention. 1992. 1993 Revised classification system for HIV infection and expanded surveillance case definition for AIDS among adolescents and adults. Morbid. Mortal. Weekly Rep. 41:RR-17. |
| 8. |
Clerici, M., and G. M. Shearer.
1993.
A TH1 TH2 switch is a critical step in the etiology of HIV infection.
Immunol. Today
14:107-111[Medline].
|
| 9. | Clerici, M., A. V. Sison, J. A. Berzofsky, T. A. Rakusan, C. D. Brandt, M. Ellaurie, M. Villa, C. Colie, D. J. Venzon, J. L. Sever, and G. M. Shearer. 1993. Cellular immune factors associated with mother-to-infant transmission of HIV. AIDS 7:1427-1433[Medline]. |
| 10. | Coffin, J. M. 1995. HIV population dynamics in vivo: implications for genetic variation, pathogenesis, and therapy. Science 267:483-489. |
| 11. | Coll, O., M. Hernandez, C. A. Boucher, C. Fortuny, B. M. de Tejada, Y. Canet, I. Caragol, J. Tijnagel, J. M. Bertran, and T. Espanol. 1997. Vertical HIV-1 transmission correlates with a high maternal viral load at delivery. J. Acquired Immune Defic. Syndr. Hum. Retrovirol. 14:26-30[Medline]. |
| 12. | Collins, K. L., B. K. Chen, S. A. Kalams, B. D. Walker, and D. Baltimore. 1998. HIV-1 Nef protein protects infected primary cells against killing by cytotoxic T lymphocytes. Nature 391:397-401[Medline]. |
| 13. |
Connor, E. M.,
R. S. Sperling,
R. Gelber,
P. Kiselev,
G. Scott,
M. J. O'Sullivan,
R. VanDyke,
M. Bey,
W. Shearer,
R. L. Jacobson,
E. Jimenez,
E. O'Neill,
B. Bazin,
J. Delfraissy,
M. Culnane,
R. Coombs,
M. Elkins,
J. Moye,
P. Stratton, and J. Balsley.
1994.
Reduction of maternal-infant transmission of human immunodeficiency virus type 1 with zidovudine treatment. Pediatric AIDS Clinical Trials Group Protocol 076 Study Group.
N. Engl. J. Med.
331:1173-1180 |
| 14. |
Devash, Y.,
T. A. Calvelli,
D. G. Wood,
K. J. Reagan, and A. Rubinstein.
1990.
Vertical transmission of human immunodeficiency virus is correlated with the absence of high-affinity/avidity maternal antibodies to the gp120 principal neutralizing domain.
Proc. Natl. Acad. Sci. USA
87:3445-3449 |
| 15. |
DiBrino, M.,
K. C. Parker,
J. Shiloach,
M. Knierman,
J. Lukszo,
R. V. Turner,
W. E. Biddison, and J. E. Coligan.
1993.
Endogenous peptides bound to HLA-A3 possess a specific combination of anchor residues that permit identification of potential antigenic peptides.
Proc. Natl. Acad. Sci. USA
90:1508-1512 |
| 16. |
Dickover, R. E.,
E. M. Garratty,
S. A. Herman,
M. S. Sim,
S. Plaeger,
P. J. Boyer,
M. Keller,
A. Deveikis,
E. R. Stiehm, and Y. J. Bryson.
1996.
Identification of levels of maternal HIV-1 RNA associated with risk of perinatal transmission. Effect of maternal zidovudine treatment on viral load.
JAMA
275:599-605 |
| 17. | Ehrnst, A., S. Lindgren, E. Belfrage, A. Sonnerborg, M. Dictor, B. Johansson, and A. B. Bohlin. 1992. Intrauterine and intrapartum transmission of HIV. Lancet 339:245-246. |
| 18. | Ehrnst, A., S. Lindgren, M. Dictor, B. Johansson, A. Sonnerborg, J. Czajkowski, G. Sundin, and A. B. Bohlin. 1991. HIV in pregnant women and their offspring: evidence for late transmission. Lancet 338:203-207[Medline]. |
| 19. |
Fang, G.,
H. Burger,
R. Grimson,
P. Tropper,
S. Nachman,
D. Mayers,
O. Weislow,
R. Moore,
C. Reyelt,
N. Hutcheon,
D. Baker, and B. Weiser.
1995.
Maternal plasma human immunodeficiency virus type 1 RNA level: a determinant and projected threshold for mother-to-child transmission.
Proc. Natl. Acad. Sci. USA
92:12100-12104 |
| 20. | Faulkner, D. V., and J. Jurka. 1988. Multiple aligned sequence editor (MASE). Trends Biochem. Sci. 13:321-322[Medline]. |
| 21. | Felsenstein, J. 1993. Phylogeny Inference Package (PHYLIP), version 3.5c. Department of Genetics, University of Washington, Seattle, Wash. |
| 22. | Ganeshan, S., R. E. Dickover, B. T. Korber, Y. J. Bryson, and S. M. Wolinsky. 1997. Human immunodeficiency virus type 1 genetic evolution in children with different rates of development of disease. J. Virol. 71:663-677[Abstract]. |
| 23. | Garrity, R. R., G. Rimmelzwaan, A. Minassian, W. P. Tsai, G. Lin, J. J. de Jong, J. Goudsmit, and P. L. Nara. 1997. Refocusing neutralizing antibody response by targeted dampening of an immunodominant epitope. J. Immunol. 159:279-289[Abstract]. |
| 24. | Goulder, P. J., R. E. Phillips, R. A. Colbert, S. McAdam, G. Ogg, M. A. Nowak, P. Giangrande, G. Luzzi, B. Morgan, A. Edwards, A. J. McMichael, and S. Rowland-Jones. 1997. Late escape from an immunodominant cytotoxic T-lymphocyte response associated with progression to AIDS. Nat. Med. 3:212-217[Medline]. |
| 25. |
Goulder, P. J.,
A. K. Sewell,
D. G. Lalloo,
D. A. Price,
J. A. Whelan,
J. Evans,
G. P. Taylor,
G. Luzzi,
P. Giangrande,
R. E. Phillips, and A. J. McMichael.
1997.
Patterns of immunodominance in HIV-1-specific cytotoxic T lymphocyte responses in two human histocompatibility leukocyte antigens (HLA)-identical siblings with HLA-A*0201 are influenced by epitope mutation.
J. Exp. Med.
185:1423-1433 |
| 26. | Hahn, B. H., G. M. Shaw, S. K. Arya, M. Popovic, R. C. Gallo, and F. Wong-Staal. 1984. Molecular cloning and characterization of the HTLV-III virus associated with AIDS. Nature 312:166-169[Medline]. |
| 27. | Harrer, T., E. Harrer, S. A. Kalams, P. Barbosa, A. Trocha, R. P. Johnson, T. Elbeik, M. B. Feinberg, S. P. Buchbinder, and B. D. Walker. 1996. Cytotoxic T lymphocytes in asymptomatic long-term nonprogressing HIV-1 infection. Breadth and specificity of the response and relation to in vivo viral quasispecies in a person with prolonged infection and low viral load. J. Immunol. 156:2616-2623[Abstract]. |
| 28. | Hay, C. M., D. J. Ruhl, N. O. Basgoz, C. C. Wilson, J. M. Billingsley, M. P. DePasquale, R. T. D'Aquila, and B. D. Walker. Lack of viral escape and defective in vivo activation of HIV-1-specific CTL in rapidly progressive HIV-1 infection. Submitted for publication. |
| 29. | Huang, Y., W. A. Paxton, S. M. Wolinsky, A. U. Neumann, L. Zhang, T. He, S. Kang, D. Ceradini, Z. Jin, K. Yazdanbakhsh, K. Kunstman, D. Erickson, E. Dragon, N. R. Landau, J. Phair, D. D. Ho, and R. A. Koup. 1996. The role of a mutant CCR5 allele in HIV-1 transmission and disease progression. Nat. Med. 2:1240-1243[Medline]. |
| 30. | Husson, R. N., Y. Lan, E. Kojima, D. Venzon, H. Mitsuya, and K. McIntosh. 1995. Vertical transmission of human immunodeficiency virus type 1: autologous neutralizing antibody, virus load, and virus phenotype. J. Pediatr. 126:865-871[Medline]. |
| 31. |
Johnson, R. P.,
A. Trocha,
T. M. Buchanan, and B. D. Walker.
1993.
Recognition of a highly conserved region of human immunodeficiency virus type 1 gp120 by an HLA-Cw4-restricted cytotoxic T-lymphocyte clone.
J. Virol.
67:438-445 |
| 32. | Johnson, R. P., A. Trocha, L. Yang, G. P. Mazzara, D. L. Panicali, T. M. Buchanan, and B. D. Walker. 1991. HIV-1 gag-specific cytotoxic T lymphocytes recognize multiple highly conserved epitopes. Fine specificity of the gag-specific response defined by using unstimulated peripheral blood mononuclear cells and cloned effector cells. J. Immunol. 147:1512-1521[Abstract]. |
| 33. |
Kalams, S. A.,
R. P. Johnson,
M. J. Dynan,
K. E. Hartman,
T. Harrer,
E. Harrer,
A. K. Trocha,
W. A. Blattner,
S. P. Buchbinder, and B. D. Walker.
1996.
T cell receptor usage and fine specificity of human immunodeficiency virus 1-specific cytotoxic T lymphocyte clones: analysis of quasispecies recognition reveals a dominant response directed against a minor in vivo variant.
J. Exp. Med.
183:1669-1679 |
| 34. | Khouri, Y. F., K. McIntosh, L. Cavacini, M. Posner, M. Pagano, R. Tuomala, and W. A. Marasco. 1995. Vertical transmission of HIV-1. Correlation with maternal viral load and plasma levels of CD4 binding site anti-gp120 antibodies. J. Clin. Investig. 95:732-737. |
| 35. |
Klein, M. R.,
C. A. van Baalen,
A. M. Holwerda,
S. R. Kerkhof Garde,
R. J. Bende,
I. P. Keet,
J. K. Eeftinck-Schattenkerk,
A. D. Osterhaus,
H. Schuitemaker, and F. Miedema.
1995.
Kinetics of Gag-specific cytotoxic T lymphocyte responses during the clinical course of HIV-1 infection: a longitudinal analysis of rapid progressors and long-term asymptomatics.
J. Exp. Med.
181:1365-1372 |
| 36. | Klenerman, P., S. Rowland-Jones, S. McAdam, J. Edwards, S. Daenke, D. Lalloo, B. Koppe, W. Rosenberg, D. Boyd, A. Edwards, P. Giangrande, R. E. Phillips, and A. J. McMichael. 1994. Cytotoxic T-cell activity antagonized by naturally occurring HIV-1 Gag variants. Nature 369:403-407[Medline]. |
| 37. | Korber, B. T., C. Brander, B. F. Haynes, J. P. Moore, R. Koup, and B. D. Walker (ed.). 1997. HIV molecular immunology database 1997. Theoretical Biology and Biophysics, Los Alamos National Laboratory, Los Alamos, N.Mex. |
| 38. |
Korber, B. T.,
K. J. Kunstman,
B. K. Patterson,
M. Furtado,
M. M. McEvilly,
R. Levy, and S. M. Wolinsky.
1994.
Genetic differences between blood- and brain-derived viral sequences from human immunodeficiency virus type 1-infected patients: evidence of conserved elements in the V3 region of the envelope protein of brain-derived sequences.
J. Virol.
68:7467-7481 |
| 39. |
Koup, R. A.,
J. T. Safrit,
Y. Cao,
C. A. Andrews,
G. McLeod,
W. Borkowsky,
C. Farthing, and D. D. Ho.
1994.
Temporal association of cellular immune responses with the initial control of viremia in primary human immunodeficiency virus type 1 syndrome.
J. Virol.
68:4650-4655 |
| 40. | Kwok, S., and R. Higuchi. 1989. Avoiding false positives with PCR. Nature 339:237-238[Medline]. |
| 41. |
Landesman, S. H.,
L. A. Kalish,
D. N. Burns,
H. Minkoff,
H. E. Fox,
C. Zorrilla,
P. Garcia,
M. G. Fowler,
L. Mofenson, and R. Tuomala.
1996.
Obstetrical factors and the transmission of human immunodeficiency virus type 1 from mother to child. The Women and Infants Transmission Study.
N. Engl. J. Med.
334:1617-1623 |
| 42. |
Learn, G. H., Jr.,
B. T. Korber,
B. Foley,
B. H. Hahn,
S. M. Wolinsky, and J. I. Mullins.
1996.
Maintaining the integrity of human immunodeficiency virus sequence databases.
J. Virol.
70:5720-5730 |
| 43. |
Lu, Z.,
J. F. Berson,
Y. Chen,
J. D. Turner,
T. Zhang,
M. Sharron,
M. H. Jenks,
Z. Wang,
J. Kim,
J. Rucker,
J. A. Hoxie,
S. C. Peiper, and R. W. Doms.
1997.
Evolution of HIV-1 coreceptor usage through interactions with distinct CCR5 and CXCR4 domains.
Proc. Natl. Acad. Sci. USA
94:6426-6431 |
| 44. | Luzuriaga, K., P. McQuilken, A. Alimenti, M. Somasundaran, R. Hesselton, and J. L. Sullivan. 1993. Early viremia and immune responses in vertical human immunodeficiency virus type 1 infection. J. Infect. Dis. 167:1008-1013[Medline]. |
| 45. | Mofenson, L. M. 1997. Interaction between timing of perinatal human immunodeficiency virus infection and the design of preventive and therapeutic interventions. Acta Paediatr. Suppl. 421:1-9[Medline]. |
| 46. | Mulder-Kampinga, G. A., A. Simonon, C. L. Kuiken, J. Dekker, H. J. Scherpbier, P. van de Perre, K. Boer, and J. Goudsmit. 1995. Similarity in env and gag genes between genomic RNAs of human immunodeficiency virus type 1 (HIV-1) from mother and infant is unrelated to time of HIV-1 RNA positivity in the child. J. Virol. 69:2285-2296[Abstract]. |
| 47. |
Peckham, C., and D. Gibb.
1995.
Mother-to-child transmission of the human immunodeficiency virus.
N. Engl. J. Med.
333:298-302 |
| 48. | Phillips, R. E., S. Rowland-Jones, D. F. Nixon, F. M. Gotch, J. P. Edwards, A. O. Ogunlesi, J. G. Elvin, J. A. Rothbard, C. R. Bangham, C. R. Rizza, and A. J. McMichael. 1991. Human immunodeficiency virus genetic variation that can escape cytotoxic T cell recognition. Nature 354:453-459[Medline]. |
| 49. |
Price, D. A.,
P. J. Goulder,
P. Klenerman,
A. K. Sewell,
P. J. Easterbrook,
M. Troop,
C. R. Bangham, and R. E. Phillips.
1997.
Positive selection of HIV-1 cytotoxic T lymphocyte escape variants during primary infection.
Proc. Natl. Acad. Sci. USA
94:1890-1895 |
| 50. | Rammensee, H. G., T. Friede, and S. Stevanoviic. 1995. MHC ligands and peptide motifs: first listing. Immunogenetics 41:178-228[Medline]. |
| 51. | Rinaldo, C., X. L. Huang, Z. F. Fan, M. Ding, L. Beltz, A. Logar, D. Panicali, G. Mazzara, J. Liebmann, M. Cottrill, and P. Gupta. 1995. High levels of anti-human immunodeficiency virus type 1 (HIV-1) memory cytotoxic T-lymphocyte activity and low viral load are associated with lack of disease in HIV-1-infected long-term nonprogressors. J. Virol. 69:5838-5842[Abstract]. |
| 52. | Robertson, C. A., J. Y. Mok, K. S. Froebel, P. Simmonds, S. M. Burns, H. S. Marsden, and S. Graham. 1992. Maternal antibodies to gp120 V3 sequence do not correlate with protection against vertical transmission of human immunodeficiency virus. J. Infect. Dis. 166:704-709[Medline]. |
| 53. |
Rossi, P.,
V. Moschese,
P. A. Broliden,
C. Fundaro,
I. Quinti,
A. Plebani,
C. Giaquinto,
P. A. Tovo,
K. Ljunggren,
J. Rosen,
H. Wigzell,
M. Jondal, and B. Wahren.
1989.
Presence of maternal antibodies to human immunodeficiency virus 1 envelope glycoprotein gp120 epitopes correlates with the uninfected status of children born to seropositive mothers.
Proc. Natl. Acad. Sci. USA
86:8055-8058 |
| 54. | Rowland-Jones, S. L., D. F. Nixon, M. C. Aldhous, F. Gotch, K. Ariyoshi, N. Hallam, J. S. Kroll, K. Froebel, and A. McMichael. 1993. HIV-specific cytotoxic T-cell activity in an HIV-exposed but uninfected infant. Lancet 341:860-861[Medline]. |
| 55. |
Scarlatti, G.,
T. Leitner,
E. Halapi,
J. Wahlberg,
P. Marchisio,
M. A. Clerici-Schoeller,
H. Wigzell,
E. M. Fenyo,
J. Albert,
M. Uhlen, and P. Rossi.
1993.
Comparison of variable region 3 sequences of human immunodeficiency virus type 1 from infected children with the RNA and DNA sequences of the virus populations of their mothers.
Proc. Natl. Acad. Sci. USA
90:1721-1725 |
| 56. |
Sperling, R. S.,
D. E. Shapiro,
R. W. Coombs,
J. A. Todd,
S. A. Herman,
G. D. McSherry,
M. J. O'Sullivan,
R. B. Van Dyke,
E. Jimenez,
C. Rouzioux,
P. M. Flynn, and J. L. Sullivan.
1996.
Maternal viral load, zidovudine treatment, and the risk of transmission of human immunodeficiency virus type 1 from mother to infant. Pediatric AIDS Clinical Trials Group Protocol 076 Study Group.
N. Engl. J. Med.
335:1621-1629 |
| 57. |
Walker, B. D.,
C. Flexner,
K. Birch-Limberger,
L. Fisher,
T. J. Paradis,
A. Aldovini,
R. Young,
B. Moss, and R. T. Schooley.
1989.
Long-term culture and fine specificity of human cytotoxic T-lymphocyte clones reactive with human immunodeficiency virus type 1.
Proc. Natl. Acad. Sci. USA
86:9514-9518 |
| 58. |
Weiser, B.,
S. Nachman,
P. Tropper,
K. H. Viscosi,
R. Grimson,
G. Baxter,
G. Fang,
C. Reyelt,
N. Hutcheon, and H. Burger.
1994.
Quantitation of human immunodeficiency virus type 1 during pregnancy: relationship of viral titer to mother-to-child transmission and stability of viral load.
Proc. Natl. Acad. Sci. USA
91:8037-8041 |
| 59. | Wilson, C. C., S. A. Kalams, B. M. Wilkes, D. J. Ruhl, F. Gao, B. H. Hahn, I. C. Hanson, K. Luzuriaga, S. Wolinsky, R. Koup, S. P. Buchbinder, R. P. Johnson, and B. D. Walker. 1997. Overlapping epitopes in human immunodeficiency virus type 1 gp120 presented by HLA A, B, and C molecules: effects of viral variation on cytotoxic T-lymphocyte recognition. J. Virol. 71:1256-1264[Abstract]. |
| 59a. | Wilson, C. C., and B. D. Walker. Unpublished data. |
| 60. | Wolinsky, S. M., B. T. Korber, A. U. Neumann, M. Daniels, K. J. Kunstman, A. J. Whetsell, M. R. Furtado, Y. Cao, D. D. Ho, and J. T. Safrit. 1996. Adaptive evolution of human immunodeficiency virus-type 1 during the natural course of infection. Science 272:537-542[Abstract]. |
| 61. |
Wolinsky, S. M.,
C. M. Wike,
B. T. Korber,
C. Hutto,
W. P. Parks,
L. L. Rosenblum,
K. J. Kunstman,
M. R. Furtado, and J. L. Munoz.
1992.
Selective transmission of human immunodeficiency virus type-1 variants from mothers to infants.
Science
255:1134-1137 |
| 62. | Wong, J. T., and R. B. Colvin. 1987. Bi-specific monoclonal antibodies: selective binding and complement fixation to cells that express two different surface antigens. J. Immunol. 139:1369-1374[Abstract]. |
| 63. | Yang, O. O., S. A. Kalams, A. Trocha, H. Cao, A. Luster, R. P. Johnson, and B. D. Walker. 1997. Suppression of human immunodeficiency virus type 1 replication by CD8+ cells: evidence for HLA class I-restricted triggering of cytolytic and noncytolytic mechanisms. J. Virol. 71:3120-3128[Abstract]. |
Journal of Virology, May 1999, p. 3975-3985, Vol. 73, No. 5
0022-538X/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
This article has been cited by other articles:
-
Hieshima, K., Nagakubo, D., Nakayama, T., Shirakawa, A.-K., Jin, Z., Yoshie, O.
(2008). Tax-Inducible Production of CC Chemokine Ligand 22 by Human T Cell Leukemia Virus Type 1 (HTLV-1)-Infected T Cells Promotes Preferential Transmission of HTLV-1 to CCR4-Expressing CD4+ T Cells. J. Immunol.
180: 931-939
[Abstract] [Full Text] -
Sanchez-Merino, V., Nie, S., Luzuriaga, K.
(2005). HIV-1-Specific CD8+ T Cell Responses and Viral Evolution in Women and Infants. J. Immunol.
175: 6976-6986
[Abstract] [Full Text] -
Genovese, D., Dettori, S., Argentini, C., Villano, U., Chionne, P., Angelico, M., Rapicetta, M.
(2005). Molecular Epidemiology of Hepatitis C Virus Genotype 4 Isolates in Egypt and Analysis of the Variability of Envelope Proteins E1 and E2 in Patients with Chronic Hepatitis. J. Clin. Microbiol.
43: 1902-1909
[Abstract] [Full Text] -
Loffredo, J. T., Sidney, J., Wojewoda, C., Dodds, E., Reynolds, M. R., Napoe, G., Mothe, B. R., O'Connor, D. H., Wilson, N. A., Watkins, D. I., Sette, A.
(2004). Identification of Seventeen New Simian Immunodeficiency Virus-Derived CD8+ T Cell Epitopes Restricted by the High Frequency Molecule, Mamu-A*02, and Potential Escape from CTL Recognition. J. Immunol.
173: 5064-5076
[Abstract] [Full Text] -
Allen, T. M., Altfeld, M., Yu, X. G., O'Sullivan, K. M., Lichterfeld, M., Le Gall, S., John, M., Mothe, B. R., Lee, P. K., Kalife, E. T., Cohen, D. E., Freedberg, K. A., Strick, D. A., Johnston, M. N., Sette, A., Rosenberg, E. S., Mallal, S. A., Goulder, P. J. R., Brander, C., Walker, B. D.
(2004). Selection, Transmission, and Reversion of an Antigen-Processing Cytotoxic T-Lymphocyte Escape Mutation in Human Immunodeficiency Virus Type 1 Infection. J. Virol.
78: 7069-7078
[Abstract] [Full Text] -
de Oliveira, T., Salemi, M., Gordon, M., Vandamme, A.-M., van Rensburg, E. J., Engelbrecht, S., Coovadia, H. M., Cassol, S.
(2004). Mapping Sites of Positive Selection and Amino Acid Diversification in the HIV Genome: An Alternative Approach to Vaccine Design?. Genetics
167: 1047-1058
[Abstract] [Full Text] -
Shriner, D., Shankarappa, R., Jensen, M. A., Nickle, D. C., Mittler, J. E., Margolick, J. B., Mullins, J. I.
(2004). Influence of Random Genetic Drift on Human Immunodeficiency Virus Type 1 env Evolution During Chronic Infection. Genetics
166: 1155-1164
[Abstract] [Full Text] -
Geels, M. J., Cornelissen, M., Schuitemaker, H., Anderson, K., Kwa, D., Maas, J., Dekker, J. T., Baan, E., Zorgdrager, F., van den Burg, R., van Beelen, M., Lukashov, V. V., Fu, T.-M., Paxton, W. A., van der Hoek, L., Dubey, S. A., Shiver, J. W., Goudsmit, J.
(2003). Identification of Sequential Viral Escape Mutants Associated with Altered T-Cell Responses in a Human Immunodeficiency Virus Type 1-Infected Individual. J. Virol.
77: 12430-12440
[Abstract] [Full Text] -
Hanke, T., Barnfield, C., Wee, E. G.-T., Agren, L., Samuel, R. V., Larke, N., Liljestrom, P.
(2003). Construction and immunogenicity in a prime-boost regimen of a Semliki Forest virus-vectored experimental HIV clade A vaccine. J. Gen. Virol.
84: 361-368
[Abstract] [Full Text] -
Yusim, K., Kesmir, C., Gaschen, B., Addo, M. M., Altfeld, M., Brunak, S., Chigaev, A., Detours, V., Korber, B. T.
(2002). Clustering Patterns of Cytotoxic T-Lymphocyte Epitopes in Human Immunodeficiency Virus Type 1 (HIV-1) Proteins Reveal Imprints of Immune Evasion on HIV-1 Global Variation. J. Virol.
76: 8757-8768
[Abstract] [Full Text] -
Sabbaj, S., Edwards, B. H., Ghosh, M. K., Semrau, K., Cheelo, S., Thea, D. M., Kuhn, L., Ritter, G. D., Mulligan, M. J., Goepfert, P. A., Aldrovandi, G. M.
(2002). Human Immunodeficiency Virus-Specific CD8+ T Cells in Human Breast Milk. J. Virol.
76: 7365-7373
[Abstract] [Full Text] -
Currier, J. R., deSouza, M., Chanbancherd, P., Bernstein, W., Birx, D. L., Cox, J. H.
(2002). Comprehensive Screening for Human Immunodeficiency Virus Type 1 Subtype-Specific CD8 Cytotoxic T Lymphocytes and Definition of Degenerate Epitopes Restricted by HLA-A0207 and -CW0304 Alleles. J. Virol.
76: 4971-4986
[Abstract] [Full Text] -
Wee, E. G.-T., Patel, S., McMichael, A. J., Hanke, T.
(2002). A DNA/MVA-based candidate human immunodeficiency virus vaccine for Kenya induces multi-specific T cell responses in rhesus macaques. J. Gen. Virol.
83: 75-80
[Abstract] [Full Text] -
Day, C. L., Shea, A. K., Altfeld, M. A., Olson, D. P., Buchbinder, S. P., Hecht, F. M., Rosenberg, E. S., Walker, B. D., Kalams, S. A.
(2001). Relative Dominance of Epitope-Specific Cytotoxic T-Lymphocyte Responses in Human Immunodeficiency Virus Type 1-Infected Persons with Shared HLA Alleles. J. Virol.
75: 6279-6291
[Abstract] [Full Text] -
Dickover, R. E., Garratty, E. M., Plaeger, S., Bryson, Y. J.
(2001). Perinatal Transmission of Major, Minor, and Multiple Maternal Human Immunodeficiency Virus Type 1 Variants In Utero and Intrapartum. J. Virol.
75: 2194-2203
[Abstract] [Full Text] -
Dela Cruz, C. S., Tan, R., Rowland-Jones, S. L., Barber, B. H.
(2000). Creating HIV-1 reverse transcriptase cytotoxic T lymphocyte target structures by HLA-A2 heavy chain modifications. Int Immunol
12: 1293-1302
[Abstract] [Full Text] -
Goulder, P. J. R., Brander, C., Annamalai, K., Mngqundaniso, N., Govender, U., Tang, Y., He, S., Hartman, K. E., O'Callaghan, C. A., Ogg, G. S., Altfeld, M. A., Rosenberg, E. S., Cao, H., Kalams, S. A., Hammond, M., Bunce, M., Pelton, S. I., Burchett, S. A., McIntosh, K., Coovadia, H. M., Walker, B. D.
(2000). Differential Narrow Focusing of Immunodominant Human Immunodeficiency Virus Gag-Specific Cytotoxic T-Lymphocyte Responses in Infected African and Caucasoid Adults and Children. J. Virol.
74: 5679-5690
[Abstract] [Full Text]
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Copyright © 2009 by the American Society for Microbiology. For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»