Characteristics of the env genes of HIV type 1 quasispecies in long-term nonprogressors with broadly neutralizing antibodies

Comparison of the Biological Basis for Non-HIV Transmission to HIV-Exposed Seronegative Individuals, Disease Non-Progression in HIV Long-Term Non-Progressors and Elite Controllers

HIV-exposed seronegative individuals (HESIs) are a small fraction of persons who are multiply exposed to human immunodeficiency virus (HIV), but do not exhibit serological or clinical evidence of HIV infection. In other words, they are groups of people maintaining an uninfected status for a long time, even after being exposed to HIV several times. The long-term non-progressors (LTNPs), on the other hand, are a group of HIV-infected individuals (approx. 5%) who remain clinically and immunologically stable for an extended number of years without combination antiretroviral therapy (cART). Meanwhile, elite controllers are comprise a much lower number (0.5%) of HIV-infected persons who spontaneously and durably control viremia to below levels of detection for at least 12 months, even when using the most sensitive assays, such as polymerase chain reaction (PCR) in the absence of cART. Despite the fact that there is no universal agreement regarding the mechanisms by which these groups of individuals are able to control HIV infection and/or disease progression, there is a general consensus that the mechanisms of protection are multifaceted and include genetic, immunological as well as viral factors. In this review, we analyze and compare the biological factors responsible for the control of HIV in these unique groups of individuals.

A Comparison of Cell Activation, Exhaustion, and Expression of HIV Coreceptors and Restriction Factors in HIV-1- and HIV-2-Infected Nonprogressors

Human immunodeficiency viruses induce rare attenuated diseases due either to HIV-1 in the exceptional long-term nonprogressors (LTNPs) or to HIV-2 in West Africa. To better understand characteristics of these two disease types we performed a multiplex comparative analysis of cell activation, exhaustion, and expression of coreceptors and restriction factors in CD4 T cells susceptible to harbor those viruses. We analyzed by flow cytometry the expression of HLA-DR, PD1, CCR5, CXCR6, SAMHD1, Blimp-1, and TRIM5α on CD4 T cell subsets from 10 HIV-1⁺ LTNPs and 14 HIV-2⁺ (12 nonprogressors and 2 progressors) of the ANRS CO-15 and CO-5 cohorts, respectively, and 12 HIV^- healthy donors (HD). The V3 loop of the HIV-1 envelope from 6 HIV-1+ LTNPs was sequenced to determine the CXCR6-binding capacity. Proportions of HLA-DR⁺ and PD1+ cells were higher in memory CD4 T subsets from HIV-1 LTNPs compared with HIV-2 and HD. Similar findings were observed for CCR5+ cells although limited to central-memory CD4 T cell (TCM) and follicular helper T cell subsets, whereas all major subsets from HIV-1 LTNPs contained less CXCR6+ cells compared with HIV-2. All six V3 loop sequences from HIV-1 LTNPs contained a proline at position 326. Proportions of SAMHD1+ cells were higher in all resting CD4 T subsets from HIV-1 LTNPs compared with the other groups, whereas Blimp-1+ and Trim5α+ cells did not differ. The CD4 T cell subsets from HIV-1 LTNPs differ from those of HIV-2-infected subjects by higher levels of activation, exhaustion, and SAMHD1 expression that can reflect the distinct patterns of host/virus relationships.

Common evolutionary features of the envelope glycoprotein of HIV-1 in patients belonging to a transmission chain

The diversity of the HIV-1 envelope glycoproteins (Env) is largely a consequence of the pressure exerted by the adaptive immune response to infection. While it was generally assumed that the neutralizing antibody (NAb) response depended mainly on the infected individual, the concept that virus-related factors could be important in inducing this response has recently emerged. Here, we analyzed the influence of the infecting viral strain in shaping NAb responses in four HIV-1 infected subjects belonging to a transmission chain. We also explored the impact of NAb responses on the functional evolution of the viral quasispecies. The four patients developed a strong autologous neutralizing antibody response that drove viral escape and coincided with a parallel evolution of their infecting quasispecies towards increasing infectious properties, increasing susceptibility to T20 and increasing resistance to both CD4 analogs and V3 loop-directed NAbs. This evolution was associated with identical Env sequence changes at several positions in the V3 loop, the fusion peptide and the HR2 domain of gp41. The common evolutionary pattern of Env in different hosts suggests that the capacity of a given Env to adapt to changing environments may be restricted by functional constraints that limit its evolutionary landscape.

Characteristics of HIV-1 env genes from Chinese chronically infected donors with highly broad cross-neutralizing activity

Knowledge about the special characteristics of HIV-1 envelope (env) glycoproteins in rare individuals developing >90% neutralization breadth in Chinese subtype B' slow progressors may provide insights for vaccine design against local viruses. We performed a cross-sectional analysis on 7 samples. We tested the neutralization breadth and geometric mean ID50 titers (GMTs) of these samples, and divided them into hBCN+ and hBCN- group according to whether their neutralization breadth >90%. We obtained env sequences in these samples through single genome amplification (SGA) assay. By comparing with hBCN-, subtype B chronically infected group (B-SP), and Chinese subtype B group (B-Database), we analyzed the characteristics of the env sequences of hBCN+ group. Longer V1 and V4 regions with more glycosylation sites were found in hBCN+ samples compared to hBCN- samples. Further analysis compared to B-SP and B-Database showed that hBCN+ group exhibited unique extra-long V1 region containing higher proportion of N-glycan sites and additional cysteines.

Impact of HIV-1 Diversity on Its Sensitivity to Neutralization

The HIV-1 pandemic remains a major burden on global public health and a vaccine to prevent HIV-1 infection is highly desirable but has not yet been developed. Among the many roadblocks to achieve this goal, the high antigenic diversity of the HIV-1 envelope protein (Env) is one of the most important and challenging to overcome. The recent development of broadly neutralizing antibodies has considerably improved our knowledge on Env structure and its interplay with neutralizing antibodies. This review aims at highlighting how the genetic diversity of HIV-1 thwarts current, and possibly future, vaccine developments. We will focus on the impact of HIV-1 Env diversification on the sensitivity to neutralizing antibodies and the repercussions of this continuous process at a population level.

HIV-Specific B Cell Frequency Correlates with Neutralization Breadth in Patients Naturally Controlling HIV-Infection

HIV-specific broadly neutralizing antibodies (bnAbs) have been isolated from patients with high viremia but also from HIV controllers that repress HIV-1 replication. In these elite controllers (ECs), multiple parameters contribute to viral suppression, including genetic factors and immune responses. Defining the immune correlates associated with the generation of bnAbs may help in designing efficient immunotherapies. In this study, in ECs either positive or negative for the HLA-B*57 protective allele, in treated HIV-infected and HIV-negative individuals, we characterized memory B cell compartments and HIV-specific memory B cells responses using flow cytometry and ELISPOT. ECs preserved their memory B cell compartments and in contrast to treated patients, maintained detectable HIV-specific memory B cell responses. All ECs presented IgG1 + HIV-specific memory B cells but some individuals also preserved IgG2 + or IgG3 + responses. Importantly, we also analyzed the capacity of sera from ECs to neutralize a panel of HIV strains including transmitted/founder virus. 29% and 21% of HLA-B*57 + and HLA-B*57 − ECs, respectively, neutralized at least 40% of the viral strains tested. Remarkably, in HLA-B*57 + ECs the frequency of HIV-Env-specific memory B cells correlated positively with the neutralization breadth suggesting that preservation of HIV-specific memory B cells might contribute to the neutralizing responses in these patients.

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In contrast to treated HIV-infected patients, elite controllers (ECs) maintain HIV-specific memory B cell responses.

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In HLA-B*57 + ECs, HIV-specific B cell frequency correlates positively with the neutralization breadth of tier-2 HIV strains.

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In HLA-B*57 + and HLA-B*57 − ECs different antibody functions are probably involved in suppressing HIV replication.

A fraction of HIV-1-infected individuals (so-called elite controllers, ECs) naturally control HIV-1 replication maintaining undetectable viral loads. Understanding the mechanisms implicated in natural control of HIV-1 infection will help in developing efficient HIV vaccines. In ECs, we analyzed the influence of B cell antibody responses. We show that in contrast to successfully treated HIV-1-infected patients, ECs preserve memory B cell compartments and maintain HIV-specific B cell responses. In ECs positive for the protective HLA-B*57 allele, HIV-specific memory B cell responses are positively associated with the breadth of HIV neutralization. These findings will help develop novel immunotherapies to fight HIV.

Multiplexed highly-accurate DNA sequencing of closely-related HIV-1 variants using continuous long reads from single molecule, real-time sequencing

Single Molecule, Real-Time (SMRT) Sequencing (Pacific Biosciences, Menlo Park, CA, USA) provides the longest continuous DNA sequencing reads currently available. However, the relatively high error rate in the raw read data requires novel analysis methods to deconvolute sequences derived from complex samples. Here, we present a workflow of novel computer algorithms able to reconstruct viral variant genomes present in mixtures with an accuracy of >QV50. This approach relies exclusively on Continuous Long Reads (CLR), which are the raw reads generated during SMRT Sequencing. We successfully implement this workflow for simultaneous sequencing of mixtures containing up to forty different >9 kb HIV-1 full genomes. This was achieved using a single SMRT Cell for each mixture and desktop computing power. This novel approach opens the possibility of solving complex sequencing tasks that currently lack a solution.

Cross-neutralizing antibody profile of Chinese HIV-1-infected individuals and the viral envelope features from elite neutralizers

OBJECTIVE

Knowledge about the profile of neutralization responses and the viral envelope features of HIV-1-infected individuals in China may provide new insights for vaccine design against local viruses.

METHODS

Eight hundred sixty plasma samples from antiretroviral treatment-naive HIV-1-infected individuals in Xinjiang province (611) and Guangxi province (249), who had acquired infection over 3 years through intravenous drug use or sexual contact, were examined for their ability to neutralize diverse envelope-pseudoviruses of 5 subtypes. The sequence features of the envelopes from elite neutralizers were analyzed.

RESULTS

From Xinjiang and Guangxi, 29.1% and 5.2% of plasmas displayed intrasubtype cross neutralization against subtype B and subtype C, respectively. From Xinjiang, 10.6% of the plasmas displayed broad neutralization against the 3 subtypes, B, C, and CRF01_AE; whereas only 2.4% from Guangxi displayed broad neutralization. Envelopes from 6 elite neutralizers were obtained by single-genome amplification. The variations of their envelopes including the lengths, glycans, and net charges in V1, V2, and V4 regions were compared with those from CRF07_BC env sequences from the HIV Sequence Database. The Envs from 3 elite neutralizers displayed the sensitivities to the monoclonal broadly neutralizing antibodies such as PG9, PG16, and 4E10. Some unique characteristics of the envelope glycoproteins from the Chinese elite neutralizers were found.

CONCLUSIONS

The neutralization profile of HIV-1-infected individuals in the 2 regions of China, where the HIV-1 subtypes are the representative in China, and the unique characteristics of the envelope glycoproteins from the Chinese elite neutralizers provide useful information for viral infection prevention and an insight for vaccine design against locally epidemic viruses.

Coreceptor usage, diversity, and divergence in drug-naive and drug-exposed individuals from Malawi, infected with HIV-1 subtype C for more than 20 years

There are few cohorts of individuals who have survived infection with HIV-1 for more than 20 years, reported and followed in the literature, and even fewer from Africa. Here we present data on a cohort of subtype C-infected individuals from rural northern Malawi. By sequencing multiple clones from long-term survivors at different time points, and using multiple genotyping approaches, we show that 5 of the 11 individuals are predicted as CXCR4 using (by ≥3/5 predictors) but only one individual is predicted as CXCR4 using by all five algorithms. Using any one genotyping approach overestimates the number of predicted CXCR4 sequences. Patterns of diversity and divergence were variable between the HIV-1 long-term survivors with some individuals showing very small amounts of variation and change, and others showing a greater amount; both patterns are consistent with what has been described in the literature.

Human immunodeficiency virus type-1 (HIV-1) continues to evolve in presence of broadly neutralizing antibodies more than ten years after infection

Background

The evolution of HIV-1 and its immune escape to autologous neutralizing antibodies (Nabs) during the acute/early phases of infection have been analyzed in depth in many studies. In contrast, little is known about neither the long-term evolution of the virus in patients who developed broadly Nabs (bNabs) or the mechanism of escape in presence of these bNabs.

Results

We have studied the viral population infecting a long term non progressor HIV-1 infected patient who had developed broadly neutralizing antibodies toward all tier 2/3 viruses (6 clades) tested, 9 years after infection, and was then followed up over 7 years. The autologous neutralization titers of the sequential sera toward env variants representative of the viral population significantly increased during the follow-up period. The most resistant pseudotyped virus was identified at the last visit suggesting that it represented a late emerging escape variant. We identified 5 amino acids substitutions that appeared associated with escape to broadly neutralizing antibodies. They were V319I/S, R/K355T, R/W429G, Q460E and G/T463E, in V3, C3 and V5 regions.

Conclusion

This study showed that HIV-1 may continue to evolve in presence of both broadly neutralizing antibodies and increasing autologous neutralizing activity more than 10 years post-infection.

Characterization of circulating HIV type 1 env genes in plasma of two antiretroviral-naive slow progressing patients with broad neutralizing antibody response with evidence of recombination

In the present study, we investigated genetic divergence between complete autologous HIV-1 env genes amplified directly from plasma of two antiretroviral-naive, slow progressing Indian patients with broad neutralizing antibody response. All the envelope (Env) clones obtained from one patient (LT1) belonged to subtype C; the second patient (LT5) harbored quasispecies comprised of pure B, C, and B/C recombinants with distinct breakpoints indicative of dual infection with genetically distinct strains. Further characterization of these Envs would provide insight into the biological properties under strong humoral immune response.

Naturally occurring substitutions of conserved residues in human immunodeficiency virus type 1 variants of different clades are involved in PG9 and PG16 resistance to neutralization

The recently described anti-human immunodeficiency virus type 1 (HIV-1) human mAb PG9 and PG16 are cross-clade broadly neutralizing. Therefore, it can be postulated that the targeted epitope(s) are highly conserved among variants of the entire group M. We analysed the sensitivity to PG9 and PG16 of pseudotyped viruses carrying envelope glycoproteins from the viral quasispecies of three HIV-1 clade CRF01_AE-infected patients. The broad heterogeneity in sensitivity to PG9 and PG16, despite closely genetically related envelope glycoproteins issued from single individuals, allowed us to identify two gp120 cross-clade conserved residues, a lysine at position 168 in the V2 loop and an isoleucine at position 215 in the C2 region, whose substitutions were associated with resistance to PG9 and PG16. By site-directed mutagenesis, we confirmed both in clades B and CRF01_AE that the substitutions K168E and I215M have a major impact on PG9 and PG16 neutralization sensitivity of pseudotyped viruses.

The V1V2 domain and an N-linked glycosylation site in the V3 loop of the HIV-1 envelope glycoprotein modulate neutralization sensitivity to the human broadly neutralizing antibody 2G12

The broadly neutralizing human monoclonal antibody 2G12 binds to a carbohydrate-dependent epitope involving three major potential N-linked glycosylation sites (PNGS) of gp120 (N295, N332, and N392). Through analysis of the sensitivity to 2G12 of pseudotyped viruses carrying envelope proteins from HIV-1 clade B-infected long-term nonprogressors, we selected two naturally occurring env clones with opposite sensitivities to 2G12, albeit harboring the 3 particular PNGS known to be essential for 2G12 binding (N295, N332, and N392). The resistant clone presented a long and potentially heavily glycosylated V1V2 loop and an additional PNGS (N302) in the V3 loop. The sensitive clone harbored a short V1V2 loop and lacked the PNGS at N302. We created chimeric envelope genes by swapping the V1V2 domains of the two env clones. The influence of N302 on 2G12 sensitivity was assessed by PCR-based site-directed mutagenesis. Both the exchange of the V1V2 domain and the introduction of the PNGS at N302 on the 2G12-sensitive clone induced a significant decrease in sensitivity to 2G12. In contrast, the reverse V1V2 exchange and the removal of the PNGS at N302 on the 2G12-resistant clone increased sensitivity to 2G12, confirming the influence of these regions on 2G12 sensitivity. Our results, supported by a molecular-modeling study, suggest that both the V1V2 loop and an additional PNGS in V3 might limit access to the 2G12 epitope.

Broad neutralizing antibody response and genetic variation in HIV-1 env genes in Koreans with primary HIV-1 infections

To determine the neutralization profiles induced by HIV-1 Korean clade B, which has a monophyletic lineage and relative limited genetic diversity, we investigated the ability of HIV variants to elicit neutralizing antibodies in the immune response to primary infection. We selected seven Korean drug-naïve subjects with an HIV-1 primary infection and did pseudovirion-based neutralization assays using env genes of Korean HIV origin. The neutralizing antibody responses to the Korean clade B showed broad reactivity to subtype B but a highly subtype-specific pattern. The lengths of the amino acid sequences and the PNGS numbers in the V1-V5 region were positively correlated with neutralization. These results imply that the genetic characteristics of HIV-1 env may affect neutralizing antibody responses in HIV-1-infected individuals. This is the first report describing the relationship between neutralizing antibody responses and HIV-1 genetic characteristics in Korean subjects. It can be useful for developing AIDS vaccines against HIV-1 subtype B strains.

Human immunodeficiency virus type 1 long-term non-progressors: the viral, genetic and immunological basis for disease non-progression

A small subset of human immunodeficiency virus type 1 (HIV-1)-infected, therapy-naive individuals--referred to as long-term non-progressors (LTNPs)--maintain a favourable course of infection, often being asymptomatic for many years with high CD4(+) and CD8(+) T-cell counts (>500 cells  μl(-1)) and low plasma HIV-RNA levels (<10 ,000 copies ml(-1)). Research in the field has undergone considerable development in recent years and LTNPs offer a piece of the puzzle in understanding the ways that persons can naturally control HIV-1 infection. Their method of control is based on viral, genetic and immunological components. With respect to virological features, genomic sequencing has shown that some LTNPs are infected with attenuated strains of HIV-1 and harbour mutant nef, vpr, vif or rev genes that contain single nuclear polymorphisms, or less frequently, large deletions, in conserved domains. Studies have also shown that some LTNPs have unique genetic advantages, including heterozygosity for the CCR5-Δ32 polymorphism, and have been found with excitatory mutations that upregulate the production of the chemokines that competitively inhibit HIV-1 binding to CCR5 or CXCR4. Lastly, immunological factors are crucial for providing LTNPs with a natural form of control, the most important being robust HIV-specific CD4(+) and CD8(+) T-cell responses that correlate with lower viral loads. Many LTNPs carry the HLA class I B57 allele that enhances presentation of antigenic peptides on the surface of infected CD4(+) cells to cytotoxic CD8(+) T cells. For these reasons, LTNPs serve as an ideal model for HIV-1 vaccine development due to their natural control of HIV-1 infection.

Autologous neutralizing antibodies to the transmitted/founder viruses emerge late after simian immunodeficiency virus SIVmac251 infection of rhesus monkeys

While the simian immunodeficiency virus (SIV)-infected rhesus monkey is an important animal model for human immunodeficiency virus type 1 (HIV-1) infection of humans, much remains to be learned about the evolution of the humoral immune response in this model. In HIV-1 infection, autologous neutralizing antibodies emerge 2 to 3 months after infection. However, the ontogeny of the SIV-specific neutralizing antibody response in mucosally infected animals has not been defined. We characterized the kinetics of the autologous neutralizing antibody response to the transmitted/founder SIVmac251 using a pseudovirion-based TZM-bl cell assay and monitored env sequence evolution using single-genome amplification in four rhesus animals that were infected via intrarectal inoculations. We show that the SIVmac251 founder viruses induced neutralizing antibodies at 5 to 8 months after infection. Despite their slow emergence and low titers, these neutralizing antibodies selected for escape mutants that harbored substitutions and deletions in variable region 1 (V1), V2, and V4 of Env. The neutralizing antibody response was initially focused on V4 at 5 to 8 months after infection and then targeted V1/V2 and V4 by 16 months. These findings reveal a striking delay in the development of neutralizing antibodies in SIVmac-infected animals, thus raising questions concerning the suitability of SIVmac251 as a challenge strain to screen AIDS vaccines that elicit neutralizing antibodies as a means to prevent virus acquisition. They also illustrate the capacity of the SIVmac quasispecies to modify antigenic determinants in response to very modest titers of neutralizing antibodies.