Safety and immunogenicity of an HLA-based HIV envelope polyvalent synthetic peptide immunogen. DATRI 010 Study Group. Division of AIDS Treatment Research Initiative

OBJECTIVE

To evaluate the safety and immunogenicity of a polyvalent (PV) HIV envelope synthetic peptide immunogen, C4-V3. The immunogen comprised four peptides containing T-helper epitopes from the fourth constant region (C4) of gp120 of HIV-1MN, and T-helper, cytotoxic T-lymphocyte HLA-B7-restricted, and B-cell neutralizing epitopes from the gp120 third variable region (V3) of four clade B HIV-1 isolates, HIV-1MN, HIV-1RF, HIV-1EV91, and HIV-1Can0A.

DESIGN

A pilot, Phase I controlled trial [Division of AIDS Treatment Research Initiative (DATRI) 010] conducted at a single center.

METHODS

Ten HIV-infected, HLA-B7-positive patients with CD4 cells > 500 x 10(6)/l were enrolled. Eight patients received the C4-V3 PV immunogen emulsified in incomplete Freund's adjuvant in five intramuscular injections over 24 weeks, and two controls received incomplete Freund's adjuvant alone. All subjects were followed for 52 weeks.

RESULTS

Four out of eight C4-V3 PV recipients generated at least fourfold rise in serum antibody titers to at least three immunogen peptides in contrast to none of the control subjects. Four out of eight C4-V3 PV recipients and none of the controls had an at least fourfold rise in neutralizing antibodies to either HIV-1MN, HIV-1RF, or HIV-1(4489-5) laboratory-adapted HIV isolates. 3H-Thymidine incorporation assays of peripheral blood mononuclear cells increased at least fivefold over the baseline stimulation index to at least one of the immunogen peptides in two consecutive post-immunization timepoints in five out of eight C4-V3 PV recipients versus none of the controls. CD4 cell counts and plasma HIV RNA levels did not change in patients who received either C4-V3 PV or adjuvant alone. Adverse events consisted primarily of grade 1 injection site reactions in six subjects (four C4-V3 recipients, two controls).

CONCLUSIONS

C4-V3 PV synthetic peptides demonstrated both immunogenicity and safety in HIV-infected patients.

Demonstration of peripheral fucose units in N-linked glycans of human immunodeficiency virus type 1 gp 120: effects on glycoprotein conformation

Fucosylated N-linked glycans are important constituents of membrane glycoproteins, owing to their significance as biologically active ligands for several selectins and their role in modulating protein conformation of viral glycoproteins. The human immunodeficiency virus type 1 (HIV-1) glycoprotein contains more than 30 different glycan structures but so far fucose was found associated solely with the innermost GlcNAc of N-linked glycans. In the present report we determined whether fucose units also were linked to the distal GlcNAc via alpha(1-3) or alpha(1-4) linkages in N-linked glycans of gp 120. [3H]-fucose labelled gp 120 was subjected to endoglycosidase F digestion, releasing diantennary complex type N-linked glycans, but leaving the inner polypeptide-bound carbohydrates, GlcNAc and possibly associated fucose units, intact. Gel filtration of the digested material revealed that [3H]-fucose label was released from gp 120 by this treatment, indicating presence of peripheral fucose units. Furthermore, [3H]-focuse label was also released by treatment of the labelled gp 120 with an alpha-L-fucosidase specifically removing fucose in alpha(1-3) and alpha(1-4) linkages. Altogether the results indicated presence of fucose units linked to peripheral GlcNAc of gp 120 N-linked glycans. We have earlier shown that other peripheral carbohydrate determinants, i.e. beta(1-4)-galactose on N-linked glycans, maintain a correct antigenic conformation of gp 120. Using a coupled ELISA system, where changes in antigenic behaviour of a viral glycoprotein were correlated to stepwise elimination of peripheral monosaccharides from N-linked glycans, we found that treatment of gp 120 with a pan-specific alpha-fucosidase as well as an enzyme specific for alpha(1-3)- or alpha(1-4)-linked fucose disclosed a hidden linear epitope situated in the gp 120 C2 region. The effects of the general fucosidase on epitope exposure was more prominent than those obtained with the enzyme with narrow specificity, suggesting that peripheral and inner fucose units co-operate in the maintenance of gp 120 conformation.

B cell-driven HIV type 1 expression in T cells: an essential role of CD86 costimulatory molecule

During HIV-1 infection, HIV-1 is sequestered and actively replicates within lymphoid organs, mainly in areas essential for antigen-specific T-B interactions. We investigated whether cognate T-B interactions not only drive humoral response to HIV-1 but also enhance viral replication. Costimulation of in vitro HIV-1-infected tonsillar T cells with autologous or allogeneic activated B cells increased both viral replication and T cell proliferation. Addition of CD86 MAb to cocultures inhibited most p24 (84 +/- 12%, n = 13) and IL-2 (99 +/- 2%, n = 6) production, decreased T cell proliferation by 46 +/- 15% (n = 13), and decreased TNF-alpha and IFN-gamma production by 67 +/- 17% (n = 6) and 53 +/- 6% (n = 6), respectively. In contrast, CD80 MAb, which strongly inhibited IL-2 production (77 +/- 10%, n = 6), moderately downregulated p24 and TNF-alpha production (29 +/- 21%, n = 13 and 34 +/- 10%, n = 6, respectively) and did not decrease T cell proliferation (8 +/- 10%, n = 13) or IFN-gamma production (14 +/- 13%, n = 6). We thus showed that B cells deliver a potent CD86/CD28 costimulatory signal that induces T cell proliferation and simultaneously enhances HIV-1 replication. CD86+ B cells, mainly localized within the light zone of germinal centers, might thus favor active in situ replication of HIV-1 in response to each new challenge by T-dependent antigens.

Evaluation of different V3 peptides in an enzyme immunoassay for specific HIV type 1 group O antibody detection

Strategies to discriminate group O from group M infections need to be improved. We have developed and evaluated an HIV-1 group O V3 peptide-based enzyme immunoassay (PEIA) for specific HIV-1 group O antibody detection among HIV-1-infected patients. Synthetic peptides, derived from the amino acid sequences of the V3 loop of 15 different group O strains and 7 group O consensus sequences, were evaluated in a PEIA against a panel of genetically confirmed group O (n = 33), group M (n = 90), and HIV-1 antibody-negative sera (n = 17). The best-performing PEIA(s) were then used to screen 134 sera of European and 336 sera of Cameroonian origin for the presence of anti-HIV-1 group O antibodies. The reactivity of reference ("gold standard") sera to individual peptides in the PEIA resulted in the selection of five different peptides with sensitivities (sens), specificities (spec), and test efficiencies (TEs) in the range of 90 to 100%. Improvement of the PEIA was obtained with simultaneous reactivity of at least two different peptides in separate wells of an ELISA plate, together with stringent criteria for positivity. We were able to select seven peptide combinations each with a sens, spec, and TE of 96.9, 100, and 99.2%, respectively. None of the 134 European and 4 (1.2%) of the 336 Cameroonian samples sera were group O positive in the optimized HIV-1 group O PEIA; this was confirmed by the repeated presence of reactives, in agreement with the present knowledge of group O infection distribution. Finally, we were able to develop a strategy with a higher TE (99.2%) than the previously used ANT-70 (98.5%) and ANT-70/MVP5180 (95.7%). Our results show that optimal specificity rather than optimal sensitivity makes the V3 PEIA a sufficiently accurate epidemiological tool to be useful in estimating specifically group O infection among HIV-1-infected patients.

Antibody-secreting cells specific for simian immunodeficiency virus antigens in lymphoid and mucosal tissues of immunized macaques

OBJECTIVES

To examine whether the route of immunization affects the induction of antibody-secreting cells (ASC) in the circulation of macaques. The distribution of ASC in the rectal mucosa and lymphoid tissues following challenge with simian immunodeficiency virus (SIV) was investigated.

DESIGN

Macaques were immunized with recombinant SIV gp120 and p27 antigens by the targeted iliac lymph node (TILN) route of immunization or the nasal and rectal route, augmented by intramuscular immunization [naso-rectal intramuscular (NRI)]. The macaques were challenged with live SIV by the rectal route and ASC were assayed in the circulation before and after SIV challenge, and in the tissues removed at post-mortem.

METHODS

ASC were examined in the circulation by Elispot assay. Mononuclear cells were prepared from peripheral blood, iliac and axillary lymph nodes and spleen. Rectal tissue was treated by enzyme digestion to elute mononuclear cells.

RESULTS

TILN and NRI immunization induced circulating IgA and IgG ASC to both gp120 and p27. Following rectal challenge with SIV, TILN macaques were protected from infection whereas NRI route-immunized and unimmunized controls became infected. IgA ASC to p27 were increased significantly in the iliac lymph nodes of the TILN immunized macaques compared with unimmunized controls (P < 0.05). Only IgA ASC were found in the rectal mucosa of the immunized protected macaques but both IgA and IgG ASC were detected in the unimmunized infected macaques. Overall the number of IgG ASC specific for p27 was significantly higher in the infected NRI and control macaques than in the protected macaques (P < 0.02). A progressive increase in IgG but not IgA ASC was detected in the peripheral blood mononuclear cells of the unimmunized infected macaques.

CONCLUSIONS

The results suggest that cells secreting IgA antibodies to p27 in the iliac lymph nodes of the TILN immunized macaques correlate significantly with protection from infection. The unimmunized infected macaques showed a progressive increase in IgG ASC in the peripheral blood after SIV challenge; this was found in the iliac and axillary lymph nodes and also in the spleen, suggesting that it is an immune response to the SIV infection.

Mechanisms of resistance of HIV-1 primary isolates to complement-mediated lysis

Previous studies suggested that HIV-1 primary isolates (PI) were resistant to complement-mediated lysis (CML), while virus produced in certain T cell lines and virus taken directly from the plasma of HIV+ persons were both susceptible to CML. The purpose of this study was to investigate the mechanism(s) of PI resistance. PI were resistant to CML using pooled seropositive serum as an antibody source. Additionally, PI obtained from two patients at several times over 2 years were resistant to CML using autologous antibody. PI were also resistant to CML induced by monoclonal antibodies which neutralize a broad range of PI. Resistance to CML was associated with low binding of antibody to PI but was not due to low gp120 levels. Cell-line-derived virus and PI were equally sensitive to CML induced by antibody to host-cell proteins, suggesting that PBMC do not contribute properties to virions which make them more physically resistant to CML in general but that PI resistance is restricted to CML induced by antiviral antibody. These studies show that PI are resistant to CML mediated by various antiviral antibodies and indicate that low binding of antibody to virus is an important factor contributing to resistance.

Expression of the extracellular domain of the human immunodeficiency virus type 1 envelope protein and its fusion with beta-galactosidase in Saccharomyces cerevisiae

Two envelope glycoprotein gene fragments were cloned from the proviral genome of the HXB2 isolate of human immunodeficiency virus (HIV). For the production of the two domains of the envelope gene product these cloned gene fragments were inserted into an Escherichia coli-yeast inducible shuttle vector fused to the galactokinase (GAL1) promoter. Cell extracts from strains of Saccharomyces cerevisiae harboring these two vectors (pYENV1 and pYENV2) were found to contain a specific protein with a size of 50 kDa when induced by galactose, while the protein could not be detected in extracts from control cells containing only the E. coli-yeast vector in the presence of galactose. Furthermore, another expression plasmid coding for fusion proteins from the majority of the external envelope glycoprotein (gp120) moiety and a large part of the beta-galactosidase was constructed. Antibodies from HIV type 1-positive sera could react with recombinant fusion polypeptides. Transformants could produce this fusion protein to a level of about 1.6% of the total protein content, as deduced from beta-galactosidase activity.

Adjuvant is required when using Env lipopeptide construct to induce HIV type 1-specific neutralizing antibody responses in mice in vivo

Extensive immunological studies on HIV-1 infection, the causative agent of AIDS in humans, have led to the conclusion that efficient protection against this infection should require early elicitation of neutralizing antibodies as well as cellular immune and particularly cytotoxic T lymphocyte responses. The use of synthetic peptides modified at one end by introduction of a lipidic tail is now well known to be an effective means of eliciting virus-specific cytotoxic T lymphocyte responses in vivo, both in mouse and humans. To ascertain that such a strategy can be used for vaccinal purposes, particularly against HIV-1 infection, it remains to be determined whether these molecules can also act as effective inducers of antibody responses, most of all of the neutralizing type. The present study set out to address this question by using a synthetic HIV-1 ENV lipopeptide construct, previously identified as a potent immunogen for in vivo induction of ENV-specific CTL responses in BALB/c mice. We first showed that V3 peptide-specific antibodies were effectively induced by the lipopeptide construct. However, we provided evidence that the biological activity of these antibodies, i.e., their ability to neutralize HIV-1 infectivity in vitro, was strongly influenced by the immunizing conditions and protocol, in that only those antibodies generated by the use of adjuvanted lipopeptide formulations were effective. Albeit at a slightly lower efficacy than by the intraperitoneal route, neutralizing antibodies could also be induced using the subcutaneous route. With the prospect of a human peptide vaccine in mind, we then studied the properties of different known or possibly clinically relevant adjuvants. We found that alum, the only relevant adjuvant for human use, not only provides inefficient help to the lipopeptide construct in generating neutralizing antibodies, but tends to have deleterious effects on the ability of the construct to induce CTL responses. The only protocol that gave satisfactory results in terms of the magnitude of the neutralizing antibody responses was a mineral oil-based lipopeptide formulation. When induced under those conditions, strong neutralizing activities were still present up to 8 months after the last injection.

Human immunodeficiency virus type 1 disease progression, CCR5 genotype, and specific immune responses

The correlation among the presence of a 32-bp deletion in the CC-chemokine receptor 5 (CCR5) gene, disease progression, and human immunodeficiency virus type 1 (HIV-1)-specific immune responses was analyzed for a cohort of 79 Caucasian HIV-1-infected patients. The CCR5 genotype (CCR5/CCR5 = wild type/wild type or delta32CCR5/CCR5 = 32-bp deletion/wild type) in peripheral blood mononuclear cells was determined by PCR, followed by sequencing of both wild-type and delta32CCR5 gene fragments. HIV-1-specific humoral responses to gp41 and V3MN peptides were determined by enzyme immunoassays. The prevalence of the delta32CCR5 allele was lower among 37 patients with rapid progression (progression to AIDS or to a CD4 cell count of <200 x 10(6)/liter in less than 9 years; P < 0.01) compared to that for 42 patients with slow progression (no AIDS and CD4 cell count of >200 x 10(6)/liter after at least 9 years from infection) or to that for 25 non-HIV-1-infected Swedish blood donors (P < 0.05). No differences were observed in the wild-type CCR5 sequences between the different groups of patients. For three analyzed patients, the 32-bp delta32CCR5 gene deletions were identical. The antibody titers against gp41 and a V3MN peptide in patients with the delta32CCR5/CCR5 genotype were not significantly different from those in pair-matched CCR5/CCR5 controls. However, in 13 analyzed patients, a stronger serum neutralizing activity was associated with the delta32CCR5/CCR5 genotype. Thus, a CCR5/CCR5 genotype correlates with a shortened AIDS-free HIV-1 infection period and possibly with a worse neutralizing activity, without an evident influence on the antibody response to two major antigenic regions of HIV-1 envelope.

HIV-1 envelope protein gp120 triggers a Th2 response in mice that shifts to Th1 in the presence of human growth hormone

Immunization of mice with HIV-1-gp120 results in predominant activation of the Th2 lymphocyte subset, leading to enhanced IL-4 production. Administration of human growth hormone at the time of gp120 immunization provokes a change in the cytokine production pattern, with lower IL-4 and higher gamma-IFN and IL-2 synthesis levels, indicating a preferential switch in stimulation from Th2 to Th1 cells. A growth hormone would thus be of great use for pharmacological intervention in those cases in which an infectious microorganism evades immune defenses by provoking a Th2 response. In addition, the ability of growth hormone to induce a Th1-type response upon vaccination with an HIV-antigen should be examined in the development of new therapeutic strategies or in the design of novel vaccines against HIV infection.

Substitutions in a major histocompatibility complex class II-restricted human immunodeficiency virus type 1 gp120 epitope can affect CD4+ T-helper-cell function

It has been suggested that the inability of the immune response to control human immunodeficiency virus type 1 (HIV-1) replication may be due, at least in part, to the capacity of this virus to escape from immune recognition through mutation. While there is increasing evidence for the importance of HIV-1-specific CD4+ T cells in containing HIV-1 spread in the infected individual, little is known about the consequences of HIV-1 mutation on virus-specific CD() T-cell function. The impact of HIV-1 sequence variation on CD4+ T-helper (Th)- cell function was assessed with a rhesus monkey model for immune recognition of the HIV-1 envelope (Env) glycoprotein. A series of HIV-1 Env(484-496) variant peptides were shown to retain the ability to bind to the appropriate rhesus monkey major histocompatibility complex class II DR molecule. Peptides bearing substitutions at position 490, however, failed to drive the proliferation or cytokine secretion of two well-characterized HXBc2 Env-specific rhesus monkey CD4+ Th-cell lines. Exogenous costimulation was ineffective in complementing the ability of the nonstimulatory peptides to induce [3H]thymidine incorporation by these cells. Finally, HIV-1 Env(484-496) variant peptides with substitutions at position 490 antagonized the HXBc2 Env peptide-induced proliferative response of the CD4+ Th-cell lines. Thus, HIV-1 variants appear to have the capacity to neutralize the function of virus-specific CD4+ T lymphocytes.

Genetic control of the immune response to HIV type 1 envelope glycoprotein 120 in mice: effects of MHC and transgenic human CD4

HIV infection elicits a strong immune response to viral proteins, including broadly cross-reactive antibodies to envelope glycoprotein 120 (gp120). However, vaccination with recombinant gp120 generally produces lower titered antibodies with narrow specificity. We have examined host genes that may control the strength and breadth of the response to gp120 vaccines. Because of the complexity of the human MHC, we have focused on the response of MHC congenic mice, which share an identical genetic background, differing only in H-2 type. The antibody response to gp120 varied markedly with H-2 type. H-2a and H-2k mice gave consistently high antibody titers, while H-2s mice gave 100-fold lower titers, and H-2b mice gave low to intermediate responses. Nearly the same genetic control applied for antibodies to both unique and shared determinants and on a variety of different genetic backgrounds. Transgenic mice expressing human CD4 gave the same titers as normal H-2-matched controls. MHC-linked genetic control of the quantity and quality of antibodies indicate a requirement for T cell help in producing antibodies to unique and shared determinants of gp120.

First human trial of a DNA-based vaccine for treatment of human immunodeficiency virus type 1 infection: safety and host response

A DNA-based vaccine containing human immunodeficiency virus type 1 (HIV-1) env and rev genes was tested for safety and host immune response in 15 asymptomatic HIV-infected patients who were not using antiviral drugs and who had CD4+ lymphocyte counts of > or = 500 per microliter of blood. Successive groups received three doses of vaccine (30, 100, or 300 microg) at 10-week intervals in a dose-escalation trial. Vaccine administration induced no local or systemic reactions, and no laboratory abnormalities were detected. Specifically, no patient developed anti-DNA antibody or muscle enzyme elevations. No consistent change occurred in CD4 or CD8 lymphocyte counts or in plasma HIV concentration. Antibody against gp120 increased in individual patients in the 100- and 300-/microg groups. Some increases were noted in cytotoxic T lymphocyte activity against gp160-bearing targets and in lymphocyte proliferative activity. The safety and potential immunogenicity of an HIV-directed DNA-based vaccine was demonstrated, a finding that should encourage further studies.

Shared antigenic epitopes on the V3 loop of HIV-1 gp120 and proteins on activated human T cells

Proliferation of HIV-1 in the infected host is characterized by a progressive loss of CD4+ T lymphocytes and consequent dysregulation of the immune system. Both direct and indirect mechanisms have been proposed. We show here that proteins with molecular weights 35, 48, and 110 kDa on stimulated primary human T cells are recognized by neutralizing antibodies against the V3 loop of HIV-1 gp120. Recognition is specific since it can be blocked by a recombinant HIV-1 gp120. Furthermore, these V3 monoclonal antibodies, as well as sera from AIDS patients that recognized these V3-like proteins, induced killing of HIV-1-infected as well as uninfected T cells. This killing was also inhibited by HIV-1 gp120 V3 peptides. These results indicate that the V3 loop shares epitopes with proteins on stimulated T cells. This may be an additional autoimmune mechanism contributing to CD4+ T cell disappearance in AIDS. V3 antibodies have been proposed as potential prophylactic agents. However, if such vaccines were based on certain epitopes, they might induce cross-reacting immune responses with cellular proteins. Vaccine candidates should be evaluated for such potential effects.

A conserved HIV gp120 glycoprotein structure involved in chemokine receptor binding

The entry of primate immunodeficiency viruses into target cells depends on a sequential interaction of the gp120 envelope glycoprotein with the cellular receptors, CD4 and members of the chemokine receptor family. The gp120 third variable (V3) loop has been implicated in chemokine receptor binding, but the use of the CCR5 chemokine receptor by diverse primate immunodeficiency viruses suggests the involvement of an additional, conserved gp120 element. Through the use of gp120 mutants, a highly conserved gp120 structure was shown to be critical for CCR5 binding. This structure is located adjacent to the V3 loop and contains neutralization epitopes induced by CD4 binding. This conserved element may be a useful target for pharmacologic or prophylactic intervention in human immunodeficiency virus (HIV) infections.

Structure of an HIV gp120 envelope glycoprotein in complex with the CD4 receptor and a neutralizing human antibody

The entry of human immunodeficiency virus (HIV) into cells requires the sequential interaction of the viral exterior envelope glycoprotein, gp120, with the CD4 glycoprotein and a chemokine receptor on the cell surface. These interactions initiate a fusion of the viral and cellular membranes. Although gp120 can elicit virus-neutralizing antibodies, HIV eludes the immune system. We have solved the X-ray crystal structure at 2.5 A resolution of an HIV-1 gp120 core complexed with a two-domain fragment of human CD4 and an antigen-binding fragment of a neutralizing antibody that blocks chemokine-receptor binding. The structure reveals a cavity-laden CD4-gp120 interface, a conserved binding site for the chemokine receptor, evidence for a conformational change upon CD4 binding, the nature of a CD4-induced antibody epitope, and specific mechanisms for immune evasion. Our results provide a framework for understanding the complex biology of HIV entry into cells and should guide efforts to intervene.

The antigenic structure of the HIV gp120 envelope glycoprotein

The human immunodeficiency virus HIV-1 establishes persistent infections in humans which lead to acquired immunodeficiency syndrome (AIDS). The HIV-1 envelope glycoproteins, gp120 and gp41, are assembled into a trimeric complex that mediates virus entry into target cells. HIV-1 entry depends on the sequential interaction of the gp120 exterior envelope glycoprotein with the receptors on the cell, CD4 and members of the chemokine receptor family. The gp120 glycoprotein, which can be shed from the envelope complex, elicits both virus-neutralizing and non-neutralizing antibodies during natural infection. Antibodies that lack neutralizing activity are often directed against the gp120 regions that are occluded on the assembled trimer and which are exposed only upon shedding. Neutralizing antibodies, by contrast, must access the functional envelope glycoprotein complex and typically recognize conserved or variable epitopes near the receptor-binding regions. Here we describe the spatial organization of conserved neutralization epitopes on gp120, using epitope maps in conjunction with the X-ray crystal structure of a ternary complex that includes a gp120 core, CD4 and a neutralizing antibody. A large fraction of the predicted accessible surface of gp120 in the trimer is composed of variable, heavily glycosylated core and loop structures that surround the receptor-binding regions. Understanding the structural basis for the ability of HIV-1 to evade the humoral immune response should assist in the design of a vaccine.

Cutting edge: JAK3 activation and rescue of T cells from HIV gp120-induced unresponsiveness

In early HIV disease, immunodeficiency is characterized by the inability of CD4+ T cells to produce a critical cytokine, IL-2, and to express the receptor for IL-2 (IL-2R) in response to antigenic or mitogenic stimulation. The shared common gamma-chain (gamma(c)) of IL-2R and its associated Janus kinase, JAK3, are indispensable for normal T cell function. Here, we show that the inhibition of IL-2R expression and proliferation induced by ligation of CD4 by HIV envelope glycoprotein, gp120, is correlated with inhibition of expression and activation of JAK3. Stimulation through the gamma(c)-related cytokine receptors restores JAK3 expression and activation and rescues CD4-mediated T cell unresponsiveness. Collectively, these data argue that inhibition of JAK3 expression and activation may, in part, explain the T cell dysfunction seen in early HIV disease. In addition, rescue from gp120-mediated T cell unresponsiveness by activation of JAK3 suggests a novel therapeutic approach for enhancing immune function in HIV disease.

Neutralizing antibodies directed against the V3 loop select for different escape variants in a virus with mutated reverse transcriptase (M184V) than in wild-type human immunodeficiency virus type 1

The M184V substitution in human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) encodes high-level resistance to the (-)-enantiomer of 2',3'-dideoxy-3'-thiacytidine (3TC) and low-level resistance to each of 2',3'-dideoxycytidine (ddC) and 2',3'-dideoxyinosine (ddI). This mutation also results in decreased HIV replication fitness in primary cells, diminished RT processivity, and increased RT fidelity. To assess the effect of this substitution on genetic variation in the HIV env region, we cultured both M184V-containing and wild-type BH10 in MT-4 cells in the presence of the neutralizing monoclonal antibody 447-52D, targeted to the GPGR epitope within the V3 loop of gp120. Outgrowth of viruses resistant to neutralization was followed by sequence analysis of the V3 loop by standard methodology. Wild-type HIV first showed escape after 15-22 days in culture. Sequence analysis revealed an arginine-to-lysine change within the GPGR epitope in the V3 loop (R20K, AGA --> AAA) in six of six clones sequenced after day 36. In contrast, M184V-containing HIV first showed escape between days 25 and 32 and sequence analysis revealed an aspartate-to-tyrosine change at amino acid 5 in V3 (N5Y; AAC --> TAC) in two of six clones at day 36 and in five of five clones at day 55. Similar results were obtained in two independent antibody selection protocols. The escape mutation in the wild type is consistent with the G --> A hypermutation observed in wild-type HIV-1, recently shown to cause an initial M184I change (before M184V) in 3TC-treated patients. In contrast, the N5Y substitution seen with M184V-containing HIV-1 is an A --> T transversion in V3.