Search

Understanding HIV-1 persistence despite antiretroviral therapy (ART) is of paramount importance. Both single-genome sequencing (SGS) and integration site analysis (ISA) provide useful information regarding the structure of persistent HIV DNA populations; however, until recently, there was no way to link integration sites to their cognate proviral sequences. Here, we used multiple-displacement amplification (MDA) of cellular DNA diluted to a proviral endpoint to obtain full-length proviral sequences and their corresponding sites of integration. We applied this method to lymph node and peripheral blood mononuclear cells from 5 ART-treated donors to determine whether groups of identical subgenomic sequences in the 2 compartments are the result of clonal expansion of infected cells or a viral genetic bottleneck. We found that identical proviral sequences can result from both cellular expansion and viral genetic bottlenecks occurring prior to ART initiation and following ART failure. We identified an expanded T cell clone carrying an intact provirus that matched a variant previously detected by viral outgrowth assays and expanded clones with wild-type and drug-resistant defective proviruses. We also found 2 clones from 1 donor that carried identical proviruses except for nonoverlapping deletions, from which we could infer the sequence of the intact parental virus. Thus, MDA-SGS can be used for "viral reconstruction" to better understand intrapatient HIV-1 evolution and to determine the clonality and structure of proviruses within expanded clones, including those with drug-resistant mutations. Importantly, we demonstrate that identical sequences observed by standard SGS are not always sufficient to establish proviral clonality. [ABSTRACT FROM AUTHOR]

The HIV-1 capsid houses the viral genome and interacts extensively with host cell proteins throughout the viral life cycle. It is composed of capsid protein (CA), which assembles into a conical fullerene lattice composed of roughly 200 CA hexamers and 12 CA pentamers. Previous structural analyses of individual CA hexamers and pentamers have provided valuable insight into capsid structure and function, but detailed structural information about these assemblies in the broader context of the capsid lattice is lacking. In this study, we combined cryoelectron tomography and single particle analysis (SPA) cryoelectron microscopy to determine structures of continuous regions of the capsid lattice containing both hexamers and pentamers. We also developed a method of liposome scaffold-based in vitro lattice assembly ("lattice templating") that enabled us to directly study the lattice under a wider range of conditions than has previously been possible. Using this approach, we identified a critical role for inositol hexakisphosphate in pentamer formation and determined the structure of the CA lattice bound to the capsid-targeting antiretroviral drug GS-6207 (lenacapavir). Our work reveals key structural details of the mature HIV-1 CA lattice and establishes the combination of lattice templating and SPA as a robust strategy for studying retroviral capsid structure and capsid interactions with host proteins and antiviral compounds. [ABSTRACT FROM AUTHOR]

AIDS-defining cancers declined after combined antiretroviral therapy (cART) introduction, but lymphomas are still elevated in HIV type 1 (HIV-1)-infected patients. In particular, non-Hodgkin's lymphomas (NHLs) represent the majority of all AIDS-defining cancers and are the most frequent cause of death in these patients. We have recently demonstrated that amino acid (aa) insertions at the HIV-1 matrix protein p17 COOH-terminal region cause protein destabilization, leading to conformational changes. Misfolded p17 variants (vp17s) strongly impact clonogenic B cell growth properties that may contribute to B cell lymphomagenesis as suggested by the significantly higher frequency of detection of vp17s with COOH-terminal aa insertions in plasma of HIV-1-infected patients with NHL. Here, we expand our previous observations by assessing the prevalence of vp17s in large retrospective cohorts of patients with and without lymphoma. We confirm the significantly higher prevalence of vp17s in lymphoma patients than in HIV-1-infected individuals without lymphoma. Analysis of 3,990 sequences deposited between 1985 and 2017 allowed us to highlight a worldwide increasing prevalence of HIV-1 mutants expressing vp17s over time. Since genomic surveillance uncovered a cluster of HIV-1 expressing a B cell clonogenic vp17 dated from 2011 to 2019, we conclude that aa insertions can be fixed in HIV-1 and that mutant viruses displaying B cell clonogenic vp17s are actively spreading. [ABSTRACT FROM AUTHOR]

In persons living with HIV-1 (PLWH) who start antiretroviral therapy (ART), plasma virus decays in a biphasic fashion to below the detection limit. The first phase reflects the short half-life (<1 d) of cells that produce most of the plasma virus. The second phase represents the slower turnover (t1/2 = 14 d) of another infected cell population, whose identity is unclear. Using the intact proviral DNA assay (IPDA) to distinguish intact and defective proviruses, we analyzed viral decay in 17 PLWH initiating ART. Circulating CD4+ T cells with intact proviruses include few of the rapidly decaying first-phase cells. Instead, this population initially decays more slowly (t1/2 = 12.9 d) in a process that largely represents death or exit from the circulation rather than transition to latency. This more protracted decay potentially allows for immune selection. After ~3 mo, the decay slope changes, and CD4+ T cells with intact proviruses decay with a half-life of 19 mo, which is still shorter than that of the latently infected cells that persist on long-term ART. Two-long-terminal repeat (2LTR) circles decay with fast and slow phases paralleling intact proviruses, a finding that precludes their use as a simple marker of ongoing viral replication. Proviruses with defects at the 5' or 3' end of the genome show equivalent monophasic decay at rates that vary among individuals. Understanding these complex early decay processes is important for correct use of reservoir assays and may provide insights into properties of surviving cells that can constitute the stable latent reservoir. [ABSTRACT FROM AUTHOR]

Koala populations are currently in rapid decline across Australia, with infectious diseases being a contributing cause. The koala retrovirus (KoRV) is a gammaretrovirus present in both captive and wild koala colonies that presents an additional challenge for koala conservation in addition to habitat loss, climate change, and other factors. Currently, nine different subtypes (A to I) have been identified; however, KoRV genetic diversity analyses have been limited. KoRV is thought to be exogenously transmitted between individuals, with KoRV-A also being endogenous and transmitted through the germline. The mechanisms of exogenous KoRV transmission are yet to be extensively investigated. Here, deep sequencing was employed on 109 captive koalas of known pedigree, housed in two institutions from Southeast Queensland, to provide a detailed analysis of KoRV transmission dynamics and genetic diversity. The final dataset included 421 unique KoRV sequences, along with the finding of an additional subtype (KoRV-K). Our analysis suggests that exogenous transmission of KoRV occurs primarily between dam and joey, with evidence provided for multiple subtypes, including nonendogenized KoRV-A. No evidence of sexual transmission was observed, with mating partners found to share a similar number of sequences as unrelated koala pairs. Importantly, both distinct captive colonies showed similar trends. These findings indicate that breeding strategies or antiretroviral treatment of females could be employed as effective management approaches in combating KoRV transmission. [ABSTRACT FROM AUTHOR]

Cholesterol-PIE12-trimer (CPT31) is a potent D-peptide HIV entry inhibitor that targets the highly conserved gp41 N-peptide pocket region. CPT31 exhibited strong inhibitory breadth against diverse panels of primary virus isolates. In a simian-HIV chimeric virus AD8 (SHIVAD8) macaque model, CPT31 prevented infection from a single high-dose rectal challenge. In chronically infected animals, CPT31 monotherapy rapidly reduced viral load by ~2 logs before rebound occurred due to the emergence of drug resistance. In chronically infected animals with viremia initially controlled by combination antiretroviral therapy (cART), CPT31 monotherapy prevented viral rebound after discontinuation of cART. These data establish CPT31 as a promising candidate for HIV prevention and treatment. [ABSTRACT FROM AUTHOR]

HIV-1 persists in cellular reservoirs that can reignite viremia if antiretroviral therapy (ART) is interrupted. Therefore, insight into the nature of those reservoirs may be revealed from the composition of recrudescing viremia following treatment cessation. A minor population of macrophage-tropic (M-tropic) viruses was identified in a library of recombinant viruses constructed with individual envelope genes that were obtained from plasma of six individuals undergoing analytic treatment interruption (ATI). M-tropic viruses could also be enriched from post-ATI plasma using macrophage-specific (CD14) but not CD4+ T cell-specific (CD3) antibodies, suggesting that M-tropic viruses had a macrophage origin. Molecular clock analysis indicated that the establishment of M-tropic HIV-1 variants predated ATI. Collectively, these data suggest that macrophages are a viral reservoir in HIV-1-infected individuals on effective ART and that M-tropic variants can appear in rebounding viremia when treatment is interrupted. These findings have implications for the design of curative strategies for HIV-1. [ABSTRACT FROM AUTHOR]

The p6 domain of HIV-1 Gag contains highly conserved peptide motifs that recruit host machinery to sites of virus assembly, thereby promoting particle release from the infected cell. We previously reported that mutations in the YPXnL motif of p6, which binds the host protein Alix, severely impair HIV-1 replication. Propagation of the p6-Alix binding site mutants in the Jurkat T cell line led to the emergence of viral revertants containing compensatory mutations not in Gag but in Vpu and the envelope (Env) glycoprotein subunits gp120 and gp41. The Env compensatory mutants replicate in Jurkat T cells and primary human peripheral blood mononuclear cells, despite exhibiting severe defects in cell-free particle infectivity and Envmediated fusogenicity. Remarkably, the Env compensatory mutants can also rescue a replication-delayed integrase (IN) mutant, and exhibit reduced sensitivity to the IN inhibitor Dolutegravir (DTG), demonstrating that they confer a global replication advantage. In addition, confirming the ability of Env mutants to confer escape from DTG, we performed de novo selection for DTG resistance and observed resistance mutations in Env. These results identify amino acid substitutions in Env that confer broad escape from defects in virus replication imposed by either mutations in the HIV-1 genome or by an antiretroviral inhibitor. We attribute this phenotype to the ability of the Env mutants to mediate highly efficient cell-to-cell transmission, resulting in an increase in the multiplicity of infection. These findings have broad implications for our understanding of Env function and the evolution of HIV-1 drug resistance. [ABSTRACT FROM AUTHOR]

Combination antiretroviral therapy controls but does not cure HIV-1 infection because a small fraction of cells harbor latent viruses that can produce rebound viremia when therapy is interrupted. The circulating latent virus reservoir has been documented by a variety of methods, most prominently by viral outgrowth assays (VOAs) in which CD4+ T cells are activated to produce virus in vitro, or more recently by amplifying proviral near full-length (NFL) sequences from DNA. Analysis of samples obtained in clinical studies in which individuals underwent analytical treatment interruption (ATI), showed little if any overlap between circulating latent viruses obtained from outgrowth cultures and rebound viruses from plasma. To determine whether intact proviruses amplified from DNA are more closely related to rebound viruses than those obtained from VOAs, we assayed 12 individuals who underwent ATI after infusion of a combination of two monoclonal anti-HIV-1 antibodies. A total of 435 intact proviruses obtained by NFL sequencing were compared with 650 latent viruses from VOAs and 246 plasma rebound viruses. Although, intact NFL and outgrowth culture sequences showed similar levels of stability and diversity with 39% overlap, the size of the reservoir estimated from NFL sequencing was larger than and did not correlate with VOAs. Finally, intact proviruses documented by NFL sequencing showed no sequence overlap with rebound viruses; however, they appear to contribute to recombinant viruses found in plasma during rebound. [ABSTRACT FROM AUTHOR]

HIV integrates into the host genome to create a persistent viral reservoir. Stimulation of CD4+ memory T lymphocytes with common γc-chain cytokines renders these cells more susceptible to HIV infection, making them a key component of the reservoir itself. IL- 15 is up-regulated during primary HIV infection, a time when the HIV reservoir established. Therefore, we investigated the molecular and cellular impact of IL-15 on CD4+ T-cell infection. We found that IL-15 stimulation induces SAM domain and HD domain-containing protein 1 (SAMHD1) phosphorylation due to cell cycle entry, relieving an early block to infection. Perturbation of the pathways downstream of IL-15 receptor (IL-15R) indicated that SAMHD1 phosphorylation after IL-15 stimulation is JAK dependent. Treating CD4+ T cells with Ruxolitinib, an inhibitor of JAK1 and JAK2, effectively blocked IL-15-induced SAMHD1 phosphorylation and protected CD4+ T cells from HIV infection. Using high-resolution single-cell immune profiling using mass cytometry by TOF (CyTOF), we found that IL-15 stimulation altered the composition of CD4+ T-cell memory populations by increasing proliferation of memory CD4+ T cells, including CD4+ T memory stem cells (TSCM). IL-15-stimulated CD4+ TSCM, harboring phosphorylated SAMHD1, were preferentially infected. We propose that IL-15 plays a pivotal role in creating a self-renewing, persistent HIV reservoir by facilitating infection of CD4+ T cells with stem cell-like properties. Time-limited interventions with JAK1 inhibitors, such as Ruxolitinib, should prevent the inactivation of the endogenous restriction factor SAMHD1 and protect this long-lived CD4+ T-memory cell population from HIV infection. [ABSTRACT FROM AUTHOR]

Given that HIV evolution and latent reservoir establishment occur continually within-host, and that latently infected cells can persist long-term, the HIV reservoir should comprise a genetically heterogeneous archive recapitulating within-host HIV evolution. However, this has yet to be conclusively demonstrated, in part due to the challenges of reconstructing within-host reservoir establishment dynamics over long timescales. We developed a phylogenetic framework to reconstruct the integration dates of individual latent HIV lineages. The framework first involves inference and rooting of a maximum-likelihood phylogeny relating plasma HIV RNA sequences serially sampled before the initiation of suppressive antiretroviral therapy, along with putative latent sequences sampled thereafter. A linear model relating root-to-tip distances of plasma HIV RNA sequences to their sampling dates is used to convert root-to-tip distances of putative latent lineages to their establishment (integration) dates. Reconstruction of the ages of putative latent sequences sampled from chronically HIV-infected individuals up to 10 y following initiation of suppressive therapy revealed a genetically heterogeneous reservoir that recapitulated HIV's within-host evolutionary history. Reservoir sequences were interspersed throughout multiple within-host lineages, with the oldest dating to >20 y before sampling; historic genetic bottleneck events were also recorded therein. Notably, plasma HIV RNA sequences isolated from a viremia blip in an individual receiving otherwise suppressive therapy were highly genetically diverse and spanned a 20-y age range, suggestive of spontaneous in vivo HIV reactivation from a large latently infected cell pool. Our framework for reservoir dating provides a potentially powerful addition to the HIV persistence research toolkit. [ABSTRACT FROM AUTHOR]

Ukraine has one of the largest HIV epidemics in Europe, historically driven by people who inject drugs (PWID). The epidemic showed signs of stabilization in 2012, but the recent war in eastern Ukraine may be reigniting virus spread. We investigated the movement of HIV-infected people within Ukraine before and during the conflict. We analyzed HIV-1 subtype-A pol nucleotide sequences sampled during 2012-2015 from 427 patients of 24 regional AIDS centers and used phylogeographic analysis to reconstruct virus movement among different locations in Ukraine. We then tested for correlations between reported PWID behaviors and reconstructed patterns of virus spread. Our analyses suggest that Donetsk and Lugansk, two cities not controlled by the Ukrainian government in eastern Ukraine, were significant exporters of the virus to the rest of the country. Additional analyses showed that viral dissemination within the country changed after 2013. Spearman correlation analysis showed that incoming virus flow was correlated with the number of HIV-infected internally displaced people. Additionally, there was a correlation between more intensive virus movement and locations with a higher proportion of PWID practicing risky sexual behaviors. Our findings suggest that effective prevention responses should involve internally displaced people and people who frequently travel to war-affected regions. Scale-up of harm reduction services for PWID will be an important factor in preventing new local HIV outbreaks in Ukraine. [ABSTRACT FROM AUTHOR]

HIV-1-infected individuals harbor a latent reservoir of infected CD4+ T cells that is not eradicated by antiretroviral therapy (ART). This reservoir presents the greatest barrier to an HIV-1 cure and has remained difficult to characterize, in part, because the vast majority of integrated sequences are defective and incapable of reactivation. To characterize the replication-competent reservoir, we have combined two techniques, quantitative viral outgrowth and qualitative sequence analysis of clonal outgrowth viruses. Leukapheresis samples from four fully ART-suppressed, chronically infected individuals were assayed at two time points separated by a 4- to 6-mo interval. Overall, 54% of the viruses emerging from the latent reservoir showed gp160 env sequences that were identical to at least one other virus. Moreover, 43% of the env sequences from viruses emerging from the reservoir were part of identical groups at the two time points. Groups of identical expanded sequences made up 54% of proviral DNA, and, as might be expected, the sequences of replication-competent viruses in the active reservoir showed limited overlap with integrated proviral DNA, most of which is known to represent defective viruses. Finally, there was an inverse correlation between proviral DNA clone size and the probability of reactivation, suggesting that replication-competent viruses are less likely to be found among highly expanded provirus-containing cell clones. [ABSTRACT FROM AUTHOR]

Reservoirs of infectious HIV-1 persist despite years of combination antiretroviral therapy and make curing HIV-1 infections a major challenge. Most of the proviral DNA resides in CD4+T cells. Some of these CD4+T cells are clonally expanded; most of the proviruses are defective. It is not known if any of the clonally expanded cells carry replication-competent proviruses. We report that a highly expanded CD4+ T-cell clone contains an intact provirus. The highly expanded clone produced infectious virus that was detected as persistent plasma viremia during cART in an HIV-1-infected patient who had squamous cell cancer. Cells containing the intact provirus were widely distributed and significantly enriched in cancer metastases. These results show that clonally expanded CD4+T cells can be a reservoir of infectious HIV-1. [ABSTRACT FROM AUTHOR]

Nucleoside analog reverse transcriptase inhibitors (NRTIs) are the essential components of highly active antiretroviral (HAART) therapy targeting HIV reverse transcriptase (RT). NRTI triphosphates (NRTI-TP), the biologically active forms, act as chain terminators of viral DNA synthesis. Unfortunately, NRTIs also inhibit human mitochondrial DNA polymerase (Pol γ), causing unwanted mitochondrial toxicity. Understanding the structural and mechanistic differences between Pol γ and RT in response to NRTIs will provide invaluable insight to aid in designing more effective drugs with lower toxicity. The NRTIs emtricitabine [(-)-2,3′-dideoxy-5-fluoro-3′-thiacytidine, (-)-FTC] and lamivudine, [(-)-2,3′-dideoxy-3′-thiacytidine, (-)-3TC] are both potent RT inhibitors, but Pol γ discriminates against (-)-FTC-TP by two orders of magnitude better than (-)-3TC-TP. Furthermore, although (-)-FTC-TP is only slightly more potent against HIV RT than its enantiomer (+)-FTC-TP, it is discriminated by human Pol γ four orders of magnitude more efficiently than (+)-FTC-TP. As a result, (-)-FTC is a much less toxic NRTI. Here, we present the structural and kinetic basis for this striking difference by identifying the discriminator residues of drug selectivity in both viral and human enzymes responsible for substrate selection and inhibitor specificity. For the first time, to our knowledge, this work illuminates the mechanism of (-)-FTC-TP differential selectivity and provides a structural scaffold for development of novel NRTIs with lower toxicity. [ABSTRACT FROM AUTHOR]

During HIV-1 fusion to the host cell membrane, the N-terminal heptad repeat (NHR) and the C-terminal heptad repeat (CHR) of the envelope subunit gp41 become transiently exposed and accessible to fusion inhibitors or Abs. In this process, the NHR region adopts a trimeric coiled-coil conformation that can be a target for therapeutic intervention. Here, we present an approach to rationally design single-chain protein constructs that mimic the NHR coiled-coil surface. The proteins were built by connecting with short loops two parallel NHR helices and an antiparallel one with the inverse sequence followed by engineering of stabilizing interactions. The constructs were expressed in Escherichia coli, purified with high yield, and folded as highly stable helical coiled coils. The crystal structure of one of the constructs confirmed the predicted fold and its ability to accurately mimic an exposed gp41 NHR surface. These single-chain proteins bound to synthetic CHR peptides with very high affinity, and furthermore, they showed broad inhibitory activity of HIV-1 fusion on various pseudoviruses and primary isolates. [ABSTRACT FROM AUTHOR]

AIDS remains incurable due to the permanent integration of HIV-1 into the host genome, imparting risk of viral reactivation even after antiretroviral therapy. New strategies are needed to ablate the viral genome from latently infected cells, because current methods are too inefficient and prone to adverse off-target effects. To eliminate the integrated HIV-1 genome, we used the Cas9/guide RNA (gRNA) system, in single and multiplex configurations. We identified highly specific targets within the HIV-1 LTR U3 region that were efficiently edited by Cas9/gRNA, inactivating viral gene expression and replication in latently infected microglial, promon-ocytic, and T cells. Cas9/gRNAs caused neither genotoxicity nor off-target editing to the host cells, and completely excised a 9,709-bp fragment of integrated proviral DNA that spanned from its 5' to 3' LTRs. Furthermore, the presence of multiplex gRNAs within Cas9-expressing cells prevented HIV-1 infection. Our results suggest that Cas9/gRNA can be engineered to provide a specific, efficacious prophylactic and therapeutic approach against AIDS. [ABSTRACT FROM AUTHOR]

Antiretroviral therapy can reduce HIV-1 to undetectable levels in peripheral blood, but the effectiveness of treatment in suppressing replication in lymphoid tissue reservoirs has not been determined. Here we show in lymph node samples obtained before and during 6 mo of treatment that the tissue concentrations of five of the most frequently used antiretroviral drugs are much lower than in peripheral blood. These lower concentrations correlated with continued virus replication measured by the slower decay or increases in the follicular dendritic cell network pool of virions and with detection of viral RNA in productively infected cells. The evidence of persistent replication associated with apparently suboptimal drug concentrations argues for development and evaluation of novel therapeutic strategies that will fully suppress viral replication in lymphatic tissues. These strategies could avert the long-term clinical consequences of chronic immune activation driven directly or indirectly by low-level viral replication to thereby improve immune reconstitution. [ABSTRACT FROM AUTHOR]

Effective control of HIV-1 infection in humans is achieved using combinations of antiretroviral therapy (ART) drugs. In humanized mice (hu-mice), control of viremia can be achieved using either ART or by immunotherapy using combinations of broadly neutralizing antibodies (bNAbs). Here we show that treatment of HIV-1-infected hu-mice with a combination of three highly potent bNAbs not only resulted in complete viremic control but also led to a reduction in cell-associated HIV-1 DNA. Moreover, lowering the initial viral load by coadministration of ART and immunotherapy enabled prolonged viremic control by a single bNAb after ART was withdrawn. Similarly, a single injection of adeno-associated virus directing expression of one bNAb produced durable viremic control after ART was terminated. We conclude that immunotherapy reduces plasma viral load and cell-associated HIV-1 DNA and that decreasing the initial viral load enables single bNAbs to control viremia in hu-mice. [ABSTRACT FROM AUTHOR]

Recently, there has been much debate about the prospects of eliminating HIV from high endemic countries by a test-and-treat strategy. This strategy entails regular HIV testing in the entire population and starting antiretroviral treatment immediately in all who are found to be HIV infected. We present the concept of the elimination threshold and investigate under what conditions of treatment uptake and dropout elimination of HIV is feasible. We used a deterministic model incorporating an accurate description of disease progression and variable infectivity. We derived explicit expressions for the basic reproduction number and the elimination threshold. Using estimates of exponential growth rates of HIV during the initial phase of epidemics, we investigated for which populations elimination is within reach. The concept of the elimination threshold allows an assessment of the prospects of elimination of HIV from information in the early phase of the epidemic. The relative elimination threshold quantifies prospects of elimination independently of the details of the transmission dynamics. Elimination of HIV by test-and-treat is only feasible for populations with very low reproduction numbers or if the reproduction number is lowered significantly as a result of additional interventions. Allowing low infectiousness during primary infection, the likelihood of elimination becomes somewhat higher. The elimination threshold is a powerful tool for assessing prospects of elimination from available data on epidemic growth rates of HIV. Empirical estimates of the epidemic growth rate from phylogenetic studies were used to assess the potential for elimination in specific populations. [ABSTRACT FROM AUTHOR]

Chronic immune activation is a major complication of antiretroviral therapy (ART) for HIV infection and can cause a devastating immune reconstitution inflammatory syndrome (IRIS) in the brain. The mechanism of T-cell activation in this population is not well understood. We found HIV-Tat protein and IL-17-expressing mononuclear cells in the brain of an individual with IRIS. Tat was also present in the CSF of individuals virologically controlled on ART. Hence we examined if Tat protein could directly activate T cells. Tat transcriptionally dysregulated 94 genes and induced secretion of 11 cytokines particularly activation of IL-17 signaling pathways supporting the development of a proinflammatory state. Tat increased IL-17 transcription and secretion in T cells. Tat entered the T cells rapidly by clathrin-mediated endocytosis and localized to both the cytoplasm and the nucleus. Tat activated T cells through a nonclassical pathway dependent upon vascular endothelial growth factor receptor-2 and downstream secondary signaling pathways but independent of the T-cell receptor. However, Tat stimulation of T cells did not induce T-cell proliferation but increased viral infectivity. This study demonstrates Tat's role as a virulence factor, by driving T-cell activation and contributing to IRIS pathophysiology. This supports the necessity of an anti-Tat therapy in conjunction with ART and identifies multiple targetable pathways to prevent Tat-mediated T-cell activation. [ABSTRACT FROM AUTHOR]

In the absence of an effective HIV-1 vaccine, passive immunization using broadly neutralizing Abs or Ab-like molecules could provide an alternative to the daily administration of oral antiretroviral agents that has recently shown promise as preexposure prophylaxis. Currently, no single broadly neutralizing Ab (bNAb) or combination of bNAbs neutralizes all HIV-1 strains at practically achievable concentrations in vivo. To address this problem, we created bispecific Abs that combine the HIV-1 inhibitory activity of ibalizumab (iMab), a humanized mAb directed to domain 2 of human CD4, with that of anti-gp120 bNAbs. These bispecific bNAbs (BibNAbs) exploit iMab's potent anti-HIV-1 activity and demonstrated clinical efficacy and safety to anchor and thereby concentrate a second broadly neutralizing agent at the site of viral entry. Two BibNabs, PG9-iMab and PG16-iMab, exhibit exceptional breadth and potency, neutralizing 100% of the 118 viruses tested at low picomolar concentrations, including viruses resistant to both parental mAbs. The enhanced potency of these BibNAbs was entirely dependent on CD4 anchoring, not on membrane anchoring per se, and required optimal Ab geometry and linker length. We propose that iMab-based BibNAbs, such as PG9-iMab and PG16-iMab, are promising candidates for passive immunization to prevent HIV-1 infection. [ABSTRACT FROM AUTHOR]

Control of HIV replication in elite controller (EC) and long-term nonprogressor (LTNP) patients has been associated with efficient CD8+ cytotoxic T-lymphocyte function. However, innate immunity may play a role in HIV control. We studied the expression of natural cytotoxicity receptors (NKp46, NKp30, and NKp44) and their induction over a short time frame (2-4 d) on activation of natural killer (NK)cells in 31 HIV controller patients (15 EC5, 16 LTNPs). In ECILTNP, induction of NKp46 expression was normal but short (2 d), and NKp30 was induced to lower levels vs. healthy donors. Notably, in antiretroviral-treated aviremic progressor patients (TAPPs), no induction of NKp46 or NKp30 expression occurred. More importantly, EC/LTNP failed to induce expression of NKp44, a receptor efficiently induced in activated NK cells in TAPPs. The specific lack of NKp44 expression resulted in sharply decreased capability of killing target cells by NKp44, whereas TAPPs had conserved NKp44-mediated lysis. Importantly, conserved NK cell responses, accompanied by a selective defect in the NKp44-activating pathway, may result in lack of killing of uninfected CD4+NKp44Ligand+ cells when induced by HlVgp41 peptide-S3, representing a relevant mechanism of CD4+ depletion. In addition, peripheral NK cells from EC/LTNP had increased NKG2D expression, significant HLA-DR up-regulation, and a mature (NKG2A—CD5T+killer cell Ig-like receptor+CD85j+) phenotype, with cytolytic function also against immature dendritic cells. Thus, NK cells in EC/LTNP can maintain substantially unchanged functional capabilities, whereas the lack of NKp44 induction may be related to CD4 maintenance, representing a hallmark of these patients. [ABSTRACT FROM AUTHOR]

The HIV Prevention Trials Network (HPTN) 052 study, which showed the effectiveness of antiretroviral treatment in reducing HIV transmission, has been hailed as a "game changer" in the fight against HIV, prompting calls for scaling up treatment as prevention (TasP). However, it is unclear how TasP can be financed, given flat-lining support for global HIV programs. We assess whether TasP is indeed a game changer or if comparable benefits are obtainable at similar or lower cost by increasing coverage of medical male circumcision (MMC) and antiretroviral treatment (ART) at CD4 <350/μL. We develop a new mathematical model and apply it to South Africa, finding that high ART coverage combined with high MMC coverage provides approximately the same HIV incidence reduction as TasP, for $5 billion less over 2009-2020. MMC outperforms ART significantly in cost per infection averted ($1,096 vs. $6,790) and performs comparably in cost per death averted ($5,198 vs. $5,604). TasP is substantially less cost effective at $8,375 per infection and $7,739 per death averted. The prevention benefits of HIV treatment are largely reaped with high ART coverage. The most cost-effective HIV prevention strategy is to expand MMC coverage and then scale up ART, but the most cost-effective HIV-mortality reduction strategy is to scale up MMC and ART jointly. TasP is cost effective by commonly used absolute benchmarks but it is far less cost effective than MMC and ART. Given South Africa's current annual ART spending, the $5 billion in savings offered by MMC and ART over TasP in the next decade, for similar health benefits, challenges the widely hailed status of TasP as a game changer. [ABSTRACT FROM AUTHOR]

HIV type 1 (HIV-1) persists within resting CD4+ T cells despite antiretroviral therapy (ART). To better understand the kinetics by which resting cell infection (RCI) is established, we developed a mathematical model that accurately predicts (r = 0.65, P = 2.5 x 10-4) the initial frequency of RCI measured about 1 year postinfection, based on the time of ART initiation and the dynamic changes in viremia and CD4+ T cells. In the largest cohort of patients treated during acute seronegative HIV infection (AHI) in whom RCI has been stringently quantified, we found that early ART reduced the generation of latently infected cells. Although RCI declined after the first year of ART in most acutely infected patients, there was a striking absence of decline when initial RCI frequency was less than 0.5 per million. Notably, low-level viremia was observed more frequently as RCI increased. Together these observations suggest that (i) the degree of RCI is directly related to the availability of CD4+ T cells susceptible to HIV, whether viremia is controlled by the immune response and/or ART; and (ii) that two pools of infected resting CD4+ T cells exist, namely, less stable cells, observable in patients in whom viremia is not well controlled in early infection, and extremely stable cells that are established despite early ART. These findings reinforce and extend the concept that new approaches will be needed to eradicate HIV infection, and, in particular, highlight the need to target the extremely small but universal, long-lived latent reservoir. [ABSTRACT FROM AUTHOR]

The antiviral potency of the cytokine IFN-α has been long appreciated but remains poorly understood. A number of studies have suggested that induction of the apolipoprotein B mRNA editing enzyme, catalytic polypeptide 3 (APOBEC3) and bone marrow stromal cell antigen 2 (BST-2/tetherin/CD317) retroviral restriction factors underlies the IFN-α-mediated suppression of HIV-1 replication in vitro. We sought to characterize the as-yet-undefined relationship between IFN-α treatment, retroviral restriction factors, and HIV-1 in vivo. APOBEC3G, APOBEC3F, and BST-2 expression levels were measured in HIV/hepatitis C virus (HCV)-coinfected, antiretroviral therapy-naïve individuals before, during, and after pegylated IFN-α/ribavirin (IFN-α/riba) combination therapy. IFN-α/riba therapy decreased HIV-1 viral load by −0.921 (±0.858) log10 copies/mL in HIV/HCV-coinfected patients. APOBEC3G/3F and BST-2 mRNA expression was significantly elevated during IFN-α/riba treatment in patient-derived CD4+ T cells (P < 0.04 and P < 0.008, paired Wilcoxon), and extent of BST-2 induction was correlated with reduction in HIV-1 viral load during treatment (P < 0.05, Pearson's r). APOBEC3 induction during treatment was correlated with degree of viral hypermutation (P < 0.03, Spearman's ρ), and evolution of the HIV-1 accessory protein viral protein U (Vpu) during IFN-α/riba treatment was suggestive of increased BST-2-mediated selection pressure. These data suggest that host restriction factors play a critical role in the antiretroviral capacity of IFN-α in vivo, and warrant investigation into therapeutic strategies that specifically enhance the expression of these intrinsic immune factors in HIV-1-infected individuals. [ABSTRACT FROM AUTHOR]

The author comments on how T-cell proliferation reservoir expansion can prove to be a barrier in curing HIV infection. Topics discussed include lifelong treatment with antiretroviral therapy (ART) for HIV infection, clonal expansion of HIV-1-infected cells, and cell cycle arrest caused by HIV-1 protein Vpr.

The article presents the authors' insight on their study of HIV-1 envelope glycoprotein epitopes. The authors describe regions on the HIV-1 surface protein called gp120 that are epitopes of nonneutralizing antibodies and support effector cells destroy CD4+ T cells during in vitro infection. Moreover, the authors consider the use of the study in the treatment of HIV-1 infected individuals without antiretroviral therapy.