V3 Region Of Gp120 Research Articles

Single nucleotide polymorphisms in the V3 region of glycoprotein 120 among Human immunodeficiency Virus positive subjects in Nigeria.

Background: The Cysteine-Cysteine Receptor 5 (CCR5) molecule is the most important co-receptor for macrophage-tropic HIV-1. A 32-bp deletion in the gene encoding CCR5 (CCR5-del32) confers nearly complete resistance to HIV-1 infection in homozygotes, and slows the rate of progression to AIDS in heterozygous adults. This study aimed to determine the frequencies of chemokine receptor 5 (CCR5) genes alleles associated with V3 loop of glycoprotein (gp) 120 among HIV patients in Yenagoa, Nigeria. Methods: Genomic DNA was extracted from whole 100 blood samples using Quick gDNA Mini Prep kit. A portion of the CCR5 gene and gp 120 regions of HIV-1 DNA were amplified from the gDNA by PCR with sequence specific primers and universal primers respetively followed by agarose gel electrophoresis. DNA sequencing of the resultant gp 120 amplicon was also carried out. Results: The CCR5 gene was positive at 189bp. None was positive to the CCR5/Δ32 heterozygous and none was also positive to the Δ32 homozygous deletion. The V3 region of the HIV DNA was seen to be positive at 250bp. Conclusion: This study shows that there is Single nucleotide polymorphism (SNP) of the protein sequence in the V3 region of gp120 among positive individuals in the study population.

Specific Substitutions in Region V2 of gp120 env confer SHIV Neutralisation Resistance

A tier 2 SHIV-MK38 strain was obtained after two in vivo passages of tier 1 SHIV-MK1. SHIV-MK38#818, cloned from the MK38 strain, was neutralisation-resistant, like the parental MK38 strain, to SHIV-infected monkey plasma (MP), HIV-1-infected human pooled plasma (HPP), and KD247 monoclonal antibody (mAb) (anti-V3 gp120 env). We investigated the mechanisms underlying the resistance of #818, specifically the amino acid substitutions that confer resistance to MK1. We introduced amino acid substitutions in the MK1 envelope by in vitro mutagenesis and then compared the neutralisation resistance to MP, HPP, and KD247 mAb with #818 in a neutralisation assay using TZM-bl cells. We selected 11 substitutions in the V1, V2, C2, V4, C4, and V5 regions based on the alignment of env of MK1 and #818. The neutralisation resistance of the mutant MK1s with 7 of 11 substitutions in the V1, C2, C4, and V5 regions did not change significantly. These substitutions did not alter any negative charges or N-glycans. The substitutions N169D and K187E, which added negative charges, and S190N in the V2 region of gp120 and A389T in V4, which created sites for N-glycan, conferred high neutralisation resistance. The combinations N169D+K187E, N169D+S190N, and N169D+A389T resulted in MK1 neutralisation resistance close to that of #818. The combinations without 169D were neutralisation-sensitive. Therefore, N169D is the most important substitution for neutralisation resistance. This study demonstrated that although the V3 region sequences of #818 and MK1 are the same, V3 binding antibodies cannot neutralise #818 pseudovirus. Instead, mutations in the V2 and V4 regions inhibit the neutralisation of anti-V3 antibodies. We hypothesised that 169D and 190N altered the MK1 Env conformation so that the V3 region is buried. Therefore, the V2 region may block KD247 from binding to the tip of the V3 region.

Functional Antibody Response Against V1V2 and V3 of HIV gp120 in the VAX003 and VAX004 Vaccine Trials

Immunization with HIV AIDSVAX gp120 vaccines in the phase III VAX003 and VAX004 trials did not confer protection. To understand the shortcomings in antibody (Ab) responses induced by these vaccines, we evaluated the kinetics of Ab responses to the V1V2 and V3 regions of gp120 and the induction of Ab-mediated antiviral functions during the course of 7 vaccinations over a 30.5-month period. Plasma samples from VAX003 and VAX004 vaccinees and placebo recipients were measured for ELISA-binding Abs and for virus neutralization, Ab-dependent cellular phagocytosis (ADCP), and Ab-dependent cellular cytotoxicity (ADCC). Ab responses to V1V2 and V3 peaked after 3 to 4 immunizations and declined after 5 to 7 immunizations. The deteriorating responses were most evident against epitopes in the underside of the V1V2 β-barrel and in the V3 crown. Correspondingly, vaccinees demonstrated higher neutralization against SF162 pseudovirus sensitive to anti-V1V2 and anti-V3 Abs after 3 or 4 immunizations than after 7 immunizations. Higher levels of ADCP and ADCC were also observed at early or mid-time points as compared with the final time point. Hence, VAX003 and VAX004 vaccinees generated V1V2- and V3-binding Abs and functional Abs after 3 to 4 immunizations, but subsequent boosts did not maintain these responses.

Reducing V3 Antigenicity and Immunogenicity on Soluble, Native-Like HIV-1 Env SOSIP Trimers.

ABSTRACTNative-like trimers of the SOSIP design are being developed as immunogens in human immunodeficiency virus type 1 (HIV-1) vaccine development programs. These trimers display the epitopes for multiple broadly neutralizing antibodies (bNAbs) but can also expose binding sites for some types of nonneutralizing antibodies (non-NAbs). Among the latter are epitopes in the gp120 V3 region that are highly immunogenic when SOSIP trimers are evaluated in animal models. It is presently uncertain whether antibodies against V3 can interfere with the induction of NAbs, but there are good arguments in favor of suppressing such “off-target” immune responses. Accordingly, we have assessed how to minimize the exposure of V3 non-NAb epitopes and thereby reduce their immunogenicity by introducing N-glycans within the V3 region of BG505 SOSIP trimers. We found that inserting glycans at positions 306 and 314 (termed M1 and M7) markedly reduced V3 antigenicity while improving the presentation of trimer apex bNAb epitopes. Both added glycans were shown to be predominantly of the Man6GlcNAc2 form. The additional introduction of the E64K ground-state stabilizing substitution markedly reduced or ablated soluble CD4 (sCD4) induction of non-NAb epitopes in V3 and/or associated with the coreceptor binding site. When a V3 glycan- and E64K-modified trimer variant, BG505 SOSIP.664-E64K.M1M7, was tested in rabbits, V3 immunogenicity was eliminated while the autologous NAb response was unchanged.IMPORTANCE Trimeric proteins are being developed for future HIV-1 vaccine trials in humans, with the goal of eliciting broadly active neutralizing antibodies (NAbs) that are active against a wide variety of circulating strains. In animal models, the present generation of native-like trimer immunogens, exemplified by the BG505 SOSIP.664 construct, induces narrow-specificity antibodies against the neutralization-resistant (tier-2), sequence-matched virus and more broadly active antibodies against sequence-divergent atypically neutralization-sensitive (tier-1) viruses. A concern in the trimer immunogen design field has been whether the latter off-target antibodies might interfere with the induction of the more desired responses to tier-2 epitopes. Here, we have inserted two glycans into the dominant site for tier-1 NAbs, the gp120 V3 region, to block the induction of off-target antibodies. We characterized the new trimers, tested them as immunogens in rabbits, and found that the blocking glycans eliminated the induction of tier-1 NAbs to V3-epitopes.

Increased HIV-1 sensitivity to neutralizing antibodies by mutations in the Env V3-coding region for resistance to CXCR4 antagonists.

HIV-1 passage in cell culture in the presence of chemokine receptor antagonists can result in selection of viruses with env mutations that confer resistance to these inhibitors. In the present study, we examined the effect of HIV-1env mutations that confer resistance to CXCR4 antagonists on envelope (Env) sensitivity to neutralizing antibodies (NAbs). Serial passage of CXCR4-tropic HIV-1 NL4-3 in PM1/CCR5 cells under CXCR4 antagonists KRH-3955, AMD3100 and AMD070 yielded two KRH-3955-resistant, one AMD3100-resistant and one AMD070-resistant viruses. These viruses had multiple env mutations including the Env gp120 V3 region. The majority of viruses having these CXCR4 antagonist-resistant Envs showed higher sensitivity to NAbs 447-52D, b12 and 2F5 targeting the V3 region, the gp120 CD4-binding site and the gp41 membrane proximal region, respectively, compared to NL4-3 WT virus. Recombinant NL4-3 viruses with the V3-coding region replaced with those derived from the CXCR4 antagonist-resistant viruses showed increased sensitivity to NAbs b12, 2F5 and 447-52D. Molecular dynamics simulations of Env gp120 outer domains predicted that the V3 mutations increased levels of fluctuations at the tip and stem of the V3 loop. These results indicate that mutations in the V3-coding region that result in loss of viral sensitivity to CXCR4 antagonists increase viral sensitivity to NAbs, providing insights into our understanding of the interplay of viral Env accessibility to chemokine receptors and sensitivity to NAbs.

HIV-1 co-receptor tropism and disease progression in children and young adults with perinatally acquired HIV-1 infection. The HICCUP Study

ObjectivesRetrospective analysis of evolution of HIV tropism and association with disease progression in perinatal HIV-1 infection (PaHIV). MethodologyEligible patients with PaHIV were grouped as slow, rapid or long-term non-progressors (LTNP). The V3 region of gp120 was sequenced from stored plasma samples and tropism determined by geno2pheno algorithm (FPR 5.75%). Logistic regression with generalised estimating equations assessed factors associated with R5 virus. Time to tropism change was assessed using standard survival methods. ResultsAt baseline (n=48) median age was 12 years (IQR 9.3–14.8), 52% were female, 79% were Black African, 96% were non-B subtypes and 81% (39/48) had R5-using virus. Median follow-up was 7.7 years (308.6 person-years), with a median of five (range 1–14) samples per subject (total 252). Analysing all samples, R5 virus was associated with higher current CD4 cell count (median 520 cells/mm3 R5 vs 202 for X4, P=0.0005), LTNP (35% vs 11%, P=0.05), non-Black ethnicity (74% vs 89%, P=0.05) and female gender (55% vs 28%, P=0.005). Twelve of 38 (31%) with R5 virus at baseline switched to X4/dual-using virus, with an estimated 5-year risk of switch of 24.4% (95% CI 9.7–39.2%) predicted by lower current CD4 cell count (unadjusted HR 0.62/50 cells higher, 95% CI 0.47–0.81, P=0.0006). Eleven of 19 (58%) with X4/dual-using virus subsequently had R5 virus at one or more time points. ConclusionMaraviroc was a treatment option for 81% at 12 years, falling to 56% at 18 years, with lower CD4 cell count predictive of co-receptor switching. Paediatric studies of CCR5 antagonists should be expedited to ensure they are an early treatment option before tropism switching occurs.

Functional and Structural Characterization of Human V3-Specific Monoclonal Antibody 2424 with Neutralizing Activity against HIV-1 JRFL.

The V3 region of HIV-1 gp120 is important for virus-coreceptor interaction and highly immunogenic. Although most anti-V3 antibodies neutralize only the sensitive tier 1 viruses, anti-V3 antibodies effective against the more resistant viruses exist, and a better understanding of these antibodies and their epitopes would be beneficial for the development of novel vaccine immunogens against HIV. The HIV-1 isolate JRFL with its cryptic V3 is resistant to most V3-specific monoclonal antibodies (MAbs). However, the V3 MAb 2424 achieves 100% neutralization against JRFL. 2424 is encoded by IGHV3-53 and IGLV2-28 genes, a pairing rarely used by the other V3 MAbs. 2424 also has distinct binding and neutralization profiles. Studies of 2424-mediated neutralization of JRFL produced with a mannosidase inhibitor further revealed that its neutralizing activity is unaffected by the glycan composition of the virus envelope. To understand the distinct activity of 2424, we determined the crystal structure of 2424 Fab in complex with a JRFL V3 peptide and showed that the 2424 epitope is located at the tip of the V3 crown ((307)IHIGPGRAFYT(319)), dominated by interactions with His(P308), Pro(P313), and Arg(P315). The binding mode of 2424 is similar to that of the well-characterized MAb 447-52D, although 2424 is more side chain dependent. The 2424 epitope is focused on the very apex of V3, away from nearby glycans, facilitating antibody access. This feature distinguishes the 2424 epitope from the other V3 crown epitopes and indicates that the tip of V3 is a potential site to target and incorporate into HIV vaccine immunogens. HIV/AIDS vaccines are crucial for controlling the HIV epidemics that continue to afflict millions of people worldwide. However, HIV vaccine development has been hampered by significant scientific challenges, one of which is the inability of HIV vaccine candidates evaluated thus far to elicit production of potent and broadly neutralizing antibodies. The V3 loop is one of the few immunogenic targets on the virus envelope glycoprotein that can induce neutralizing antibodies, but in many viruses, parts of V3 are inaccessible for antibody recognition. This study examined a V3-specific monoclonal antibody that can completely neutralize HIV-1 JRFL, a virus isolate resistant to most V3 antibodies. Our data reveal that this antibody recognizes the most distal tip of V3, which is not as occluded as other parts of V3. Hence, the epitope of 2424 is in one of the vulnerable sites on the virus that may be exploited in designing HIV vaccine immunogens.

Is an HIV vaccine achievable? - Pros

The development of an HIV/ AIDS vaccine has been a long and difficult endeavor, which so far was met with a great many failures. New, recent advances may however change the deal. The RV144 clinical trial in Thailand showed that a canarypox-gp120 prime-boost vaccination regimen had a modest 31% efficacy at 42 months after vaccination, but protection was as high as 60% at 6 months after vaccination. A series of new trials is expected to take place in the near future to try to improve these numbers using a more potent vector than canarypox, gp140 rather than gp120, a water-in-oil adjuvant rather than aluminium salts, and increasing the number of booster immunizations. Protection in the RV144 trial correlated with the induction of antibodies (Ab) to the V2 region of gp120, not with neutralizing Abs. A major difficulty met in the development of an efficacious HIV vaccine has indeed been to design proper immunogens able to elicit broadly neutralizing Abs (bnAbs) that can neutralize a wide range of circulating virus strains. BnAbs are highly protective, as demonstrated by passive immunization experiments and by vectored immunoprophylaxis experiments using AAV as a vector in animal models such as macaques or humanized mice. Their efficacy in humans should be tested soon in upcoming clinical trials. On another hand, the report that monkeys immunized with a simian CMV-SIV vaccine can clear SIV infection following viral challenge has emphasized the importance of self-renewing, long-lasting memory TEM cells that can differentiate into specific effector T cells and control provirus activation, eventually resulting in the clearance of infection. A HIV vaccine that could elicit both a bnAb response and the formation of specific TEM cells would obviously be an ideal vaccine. It might even offer hopes for a cure of HIV infection when used therapeutically in HIV-infected persons. The development of such a vaccine is still long and difficult but may not to be an unrealistic goal.

Alterations in HIV-1 gp120 V3 region are necessary but not sufficient for coreceptor switching in CRF07_BC in China.

The most predominant HIV-1 strains in China's current epidemic is the Circulating Recombinant Form 07_BC (CRF07_BC). CRF07_BC is mainly considered as a CCR5-tropic (R5) virus, since CXCR4-tropic (X4) viruses have thus far not been found in this subtype, and the molecular determinants of coreceptor switching remain unknown. To investigate the mechanisms underlying coreceptor requirement in CRF07_BC viruses, we characterized a panel of pNL4-3-based chimeric viruses with mutated V3 loop regions derived from an HIV-1 CRF07_BC infectious clone pXJDC13. Among 17 chimeric viruses, seven were dual-tropic and induced syncytium formation in MT-2 cells. Two amino acid insertions between positions 13 and 14, as well as arginine substitution at position 11 or 16 (IG insertion and P16R mutation or MG insertion and S11R mutation), conferred the chimeric viruses CXCR4-tropic features, which were same as subtype C X4 viruses. Next, to construct CRF07_BC X4 variants, mutated V3 loops were cloned into the CRF07_BC infectious clone pXJDC13. These V3 loops, which in the pNL4-3 backbone conferred chimeric viruses with CXCR4-using ability, abrogated infectivity completely in the CRF07_BC pXJDC13 genetic background. Similarly, IG insertion or MG insertion and S11R mutation dramatically diminished or completely abolished viral infectivity in other envelopes of subtype C or CRF07_BC. These results suggest that the effects of IG insertion and P16R mutation or MG insertion and S11R mutation on CXCR4 usage are context dependent, and additional mutations elsewhere in the envelope are needed to compensate for these fitness-reducing alterations.

Plasma IgG to Linear Epitopes in the V2 and V3 Regions of HIV-1 gp120 Correlate with a Reduced Risk of Infection in the RV144 Vaccine Efficacy Trial

Neutralizing and non-neutralizing antibodies to linear epitopes on HIV-1 envelope glycoproteins have potential to mediate antiviral effector functions that could be beneficial to vaccine-induced protection. Here, plasma IgG responses were assessed in three HIV-1 gp120 vaccine efficacy trials (RV144, Vax003, Vax004) and in HIV-1-infected individuals by using arrays of overlapping peptides spanning the entire consensus gp160 of all major genetic subtypes and circulating recombinant forms (CRFs) of the virus. In RV144, where 31.2% efficacy against HIV-1 infection was seen, dominant responses targeted the C1, V2, V3 and C5 regions of gp120. An analysis of RV144 case-control samples showed that IgG to V2 CRF01_AE significantly inversely correlated with infection risk (OR= 0.54, p=0.0042), as did the response to other V2 subtypes (OR=0.60-0.63, p=0.016-0.025). The response to V3 CRF01_AE also inversely correlated with infection risk but only in vaccine recipients who had lower levels of other antibodies, especially Env-specific plasma IgA (OR=0.49, p=0.007) and neutralizing antibodies (OR=0.5, p=0.008). Responses to C1 and C5 showed no significant correlation with infection risk. In Vax003 and Vax004, where no significant protection was seen, serum IgG responses targeted the same epitopes as in RV144 with the exception of an additional C1 reactivity in Vax003 and infrequent V2 reactivity in Vax004. In HIV-1 infected subjects, dominant responses targeted the V3 and C5 regions of gp120, as well as the immunodominant domain, heptad repeat 1 (HR-1) and membrane proximal external region (MPER) of gp41. These results highlight the presence of several dominant linear B cell epitopes on the HIV-1 envelope glycoproteins. They also generate the hypothesis that IgG to linear epitopes in the V2 and V3 regions of gp120 are part of a complex interplay of immune responses that contributed to protection in RV144.

A Twin-Cysteine Motif in the V2 Region of gp120 Is Associated with SIV Envelope Trimer Stabilization

The V1 and V2 variable regions of the primate immunodeficiency viruses contribute to the trimer association domain of the gp120 exterior envelope glycoprotein. A pair of V2 cysteine residues at 183 and 191 (“twin cysteines”) is present in several simian immunodeficiency viruses, human immunodeficiency virus type 2 (HIV-2) and some SIVcpz lineages, but not in HIV-1. To examine the role of this potentially disulfide-bonded twin-cysteine motif, the cysteine residues in the SIVmac239 envelope glycoproteins were individually and pairwise substituted by alanine residues. All of the twin-cysteine mutants exhibited decreases in gp120 association with the Env trimer, membrane-fusing activity, and ability to support virus entry. Thus, the twin-cysteine motif plays a role in Env trimer stabilization in SIV and may do so in HIV-2 and some SIVcpz as well. This implies that HIV-1 lost the twin-cysteines, and may have relatively unstable Env trimers compared to SIV and HIV-2.

Short Communication: Synergism Between a CD4-Mimic Peptide and Antibodies Elicited by a Constrained V3 Peptide

Due to the different mechanisms HIV-1 has evolved to escape from a neutralizing antibody response it has been extremely challenging to develop an effective anti-HIV-1 vaccine. The V3 region of the gp120 HIV-1 envelope glycoprotein has been considered as one of the possible targets for an anti-HIV vaccine. It is well known that the V3 region of gp120 is at least partially masked in circulating strains and becomes exposed only after CD4 binding. However, when the virus is bound to surface CD4, steric hindrance prevents effective neutralization by V3-directed antibodies. Here we have used a 27-residue CD4-mimetic peptide in combination with immune sera elicited by an optimally constrained V3 peptide to enhance neutralization of a panel of clade B viruses. We observed strong synergism between the immune sera and the CD4-mimetic in the neutralization of tier 1 and a representative tier 2 clade B virus suggesting that the constrained V3 peptide immunogen correctly mimics the V3 conformation even in tier 2 clade B viruses. This synergy should improve the potential of CD4-mimetic compounds for preexposure prophylaxis and in the treatment of HIV-1-infected patients who usually manifest high titers of V3-directed antibodies. Moreover, constrained V3 immunogens elicit immune sera that may neutralize HIV in synergy with CD4 binding site antibodies that expose V3 and the coreceptor binding site.

Skin tattooing as an effective tool for delivering DNA and protein vaccine immunogens

Background Skin is an excellent site for vaccine administration due to the abundance of antigen presenting cells and easy access. When DNA or protein is delivered into the skin, uptake and expression of immunogens can lead to a rapid and robust induction of immune responses.Skin tattooing has been suggested as a useful tool delivering vaccines intradermally. We have chosen to use the skin tattooing technique to deliver both DNA and protein immunogens that are focusing the immune response on the highly immunogenic V3 region of HIV-1 gp120. Methods A GFP-containing plasmid was used first to optimize the protocol for skin tattooing on BALB/c mice. Subsequently, BALB/c mice were immunized using a DNA prime/Protein boost regimen. DNA skin tattooing was used first as the prime to deliver a gp120-encoding DNA plasmid intradermally at weeks 0, 2, and 4. The animals were then given a fusion protein, V3-bearing cholera toxin subunit B (V3-CTB), via skin tattooing (Group1; n=5) or intramuscular injection (Group2; n=5) at weeks 10 and 14. Two weeks after the final immunization, the sera were collected and analyzed. Results GFP expressed in skin cells was visualized by confocal microscopy showing that skin tattooing can effectively deliver DNA into these cells. ELISA assays using sera drawn after the final immunization confirmed that tattoodelivered DNA followed by V3-CTBelicited V3 binding antibodies, and these antibodies have potent neutralizing activities in an HIV pseudovirus neutralization assay. Conclusion Immunization by skin tattooing is an easy, effective, and economical way to administer both DNA and protein vaccines. Interestingly, the needle perforations may serve as a potent and natural adjuvant for the immunization, making skin tattooing a promising vaccine delivery technique.

Comprehensive Investigation of Common Antibody-Dependent Cell-Mediated Cytotoxicity Antibody Epitopes of HIV-1 CRF01_AE gp120

The antibody-dependent cell-mediated cytotoxicity (ADCC) mechanism involves both innate and adaptive immune systems. While a number of epitope mapping studies of neutralizing (Nt) antibodies and cytotoxic T lymphocyte (CTL) against a variety of HIV-1 clades have been reported, there has been a paucity of similar studies aimed at identifying epitopes of ADCC-inducing antibodies. Herein we screened 35 sera from HIV-1 CRF01_AE-infected blood donors for ADCC antibody activity against gp120 utilizing an EGFP-CEM-NK(r) flow cytometric assay. Eighteen sera with high ADCC antibody activity were then comprehensively examined for ADCC antibody epitopes using the HIV-1 subtype CRF01_AE TH023 gp120 peptide set consisting of 126 peptides of 15 amino acids in length, overlapping by 11 amino acids. This peptide set was divided into five pools (E1-E5). Each positive peptide pool was further investigated for fine epitope mapping of ADCC antibody activity using a 5 by 5 peptide matrix format. Interestingly, six and three peptides from peptide pools E1 and E2, respectively, responded to at least 33.33% of the tested sera. These nine common ADCC epitopes were localized to the C1 and V2 region of gp120. Furthermore, 5/9 epitopes were also shown to serve as full or partial Nt antibody targets for HIV-1 subtypes B and CRF01_AE. We submit these data on epitope mapping of ADCC or dual ADCC-Nt antibodies against HIV-1 gp120 that should be considered in the formulation of vaccines against HIV-1.

V3 determinants of HIV-1 escape from the CCR5 inhibitors Maraviroc and Vicriviroc

HIV-1 develops resistance to CCR5 antagonists such as Maraviroc (MVC) and Vicriviroc (VVC) both in vitro and in vivo, with most changes arising in the gp120 V3 region. Both compounds bind to the same hydrophobic cavity in CCR5 in subtly different ways. Here, we investigated which V3 sequence changes are most associated with MVC and VVC resistance and how they affect the interaction between gp120 and the CCR5 NT. We found that VVC- and MVC-selected amino acid changes map to different V3 locations and involve residues that interact with the CCR5 NT in different ways. Changes in VVC-selected, but not MVC-selected, variants often involve charged residues. Although the overall V3 charge tends not to change, the introduction or removal of charged residues at specific positions affects the local electrostatic potential and could have structural and functional implications. In summary, VVC and MVC trigger the evolution of distinct HIV-1 resistance patterns in V3.

Binding Antibody Responses to the Immunogenic Regions Of Viral Envelope in HIV-1-Infected Indian Children

Limited information exists on the antibody responses elicited against the viral envelope in HIV-1-infected children. In this cross-sectional study, we assessed the antibody responses against three different immunogenic regions of HIV-1 envelope, namely V3 region of gp120, membrane proximal external region (MPER), and immunodominant loop (IDL) of gp41 in HIV-1-infected children from north India. We recruited 75 HIV-1-infected (40 antiretroviral naive and 35 treated) children, with age ranging from 1.5 to 16 y. Antibodies to V3 and the IDL region were found in a majority of the infected children, whereas antibodies to MPER were found in approximately one-third of the children studied. Higher antibody titers to the immunogenic regions corresponded to the symptomatic stages of HIV-1 infection in both naive and antiretroviral therapy (ART)-treated children. High titers of anti-V3C and anti-IDL antibodies were observed in a subset of antiretroviral-naive patients with suppressed viremia (<47 RNA copies/mL), suggesting that antibodies to these immunogenic regions are present regardless of their viremic status. Further, the antibody titers were significantly lower in the plasma of treated patients compared to naive patients, regardless of whether they were virologically suppressed or not. This is the first report on the antibody responses elicited in HIV-1-infected children in India. The study may help to understand the humoral antibody responses directed against viral envelope in HIV-1-infected children.

Short Communication: Phylogenetic Characterization of HIV Type 1 CRF01_AE V3 Envelope Sequences in Pregnant Women in Northern Vietnam

Characterization of HIV-1 strains is important for surveillance of the HIV-1 epidemic. In Vietnam HIV-1-infected pregnant women often fail to receive the care they are entitled to. Here, we analyzed phylogenetically HIV-1 env sequences from 37 HIV-1-infected pregnant women from Ha Noi (n=22) and Hai Phong (n=15), where they delivered in 2005-2007. All carried CRF01_AE in the gp120 V3 region. In 21 women CRF01_AE was also found in the reverse transcriptase gene. We compared their env gp120 V3 sequences phylogenetically in a maximum likelihood tree to those of 198 other CRF01_AE sequences in Vietnam and 229 from neighboring countries, predominantly Thailand, from the HIV-1 database. Altogether 464 sequences were analyzed. All but one of the maternal sequences colocalized with sequences from northern Vietnam. The maternal sequences had evolved the least when compared to sequences collected in Ha Noi in 2002, as shown by analysis of synonymous and nonsynonymous changes, than to other Vietnamese sequences collected earlier and/or elsewhere. Since the HIV-1 epidemic in women in Vietnam may still be underestimated, characterization of HIV-1 in pregnant women is important to observe how HIV-1 has evolved and follow its molecular epidemiology.

Virus-inhibitory peptide

Virus-inhibitory peptide

Multiple CCR5 Conformations on the Cell Surface Are Used Differentially by Human Immunodeficiency Viruses Resistant or Sensitive to CCR5 Inhibitors

Resistance to small-molecule CCR5 inhibitors arises when HIV-1 variants acquire the ability to use inhibitor-bound CCR5 while still recognizing free CCR5. Two isolates, CC101.19 and D1/85.16, became resistant via four substitutions in the gp120 V3 region and three in the gp41 fusion peptide (FP), respectively. The binding characteristics of a panel of monoclonal antibodies (MAbs) imply that several antigenic forms of CCR5 are expressed at different levels on the surfaces of U87-CD4-CCR5 cells and primary CD4(+) T cells, in a cell-type-dependent manner. CCR5 binding and HIV-1 infection inhibition experiments suggest that the two CCR5 inhibitor-resistant viruses altered their interactions with CCR5 in different ways. As a result, both mutants became generally more sensitive to inhibition by CCR5 MAbs, and the FP mutant is specifically sensitive to a MAb that stains discrete cell surface clusters of CCR5 that may correspond to lipid rafts. We conclude that some MAbs detect different antigenic forms of CCR5 and that inhibitor-sensitive and -resistant viruses can use these CCR5 forms differently for entry in the presence or absence of CCR5 inhibitors.

Resistance of a human immunodeficiency virus type 1 isolate to a small molecule CCR5 inhibitor can involve sequence changes in both gp120 and gp41

Here, we describe the genetic pathways taken by a human immunodeficiency virus type 1 (HIV-1) isolate, D101.12, to become resistant to the small molecule CCR5 inhibitor, vicriviroc (VCV), in vitro. Resistant D101.12 variants contained at least one substitution in the gp120 V3 region (H308P), plus one of two patterns of gp41 sequence changes involving the fusion peptide (FP) and a downstream residue: G514V+V535M or M518V+F519L+V535M. Studies of Env-chimeric and point-substituted viruses in peripheral blood mononuclear cells (PBMC) and TZM-bl cells showed that resistance can arise from the cooperative action of gp120 and gp41 changes, while retaining CCR5 usage. Modeling the VCV inhibition data from the two cell types suggests that D101.12 discriminates between high- and low-VCV affinity forms of CCR5 less than D1/85.16, a resistant virus with three FP substitutions.