Javier Martinez-Picado

HIV-1 replication and immune dynamics are affected by raltegravir intensification of HAART-suppressed subjects

Highly active antiretroviral therapy (HAART) results in potent and durable suppression of HIV-1 viremia. However, HIV-1 replication resumes if therapy is interrupted. Although it is generally believed that active replication has been halted in individuals on HAART, immune activation and inflammation continue at abnormal levels, suggesting continued, low-level viral replication. To assess whether active replication might be driving immune activation in HAART, we examined the impact of treatment intensification with the integrase inhibitor raltegravir on viral complementary DNA and immune activation parameters. In the presence of raltegravir, linear HIV-1 cDNA is prevented from integrating into chromatin and is subsequently converted to episomal cDNAs. Raltegravir intensification of a three-drug suppressive HAART regimen resulted in a specific and transient increase in episomal DNAs in a large percentage of HAART-suppressed subjects. Furthermore, in subjects with these episomal DNAs, immune activation was higher at baseline and was subsequently normalized after raltegravir intensification. These results suggest that, despite suppressive HAART, active replication persists in some infected individuals and drives immune activation. The ability of raltegravir intensification to perturb the reservoir that supports active replication has implications for therapeutic strategies aimed at achieving viral eradication.

Fitness Cost of Escape Mutations in p24 Gag in Association with Control of Human Immunodeficiency Virus Type 1

ABSTRACT Mutational escape by human immunodeficiency virus (HIV) from cytotoxic T-lymphocyte (CTL) recognition is a major challenge for vaccine design. However, recent studies suggest that CTL escape may carry a sufficient cost to viral replicative capacity to facilitate subsequent immune control of a now attenuated virus. In order to examine how limitations can be imposed on viral escape, the epitope TSTLQEQIGW (TW10 [Gag residues 240 to 249]), presented by two HLA alleles associated with effective control of HIV, HLA-B*57 and -B*5801, was investigated. The in vitro experiments described here demonstrate that the dominant TW10 escape mutation, T242N, reduces viral replicative capacity. Structural analysis reveals that T242 plays a critical role in defining the start point and in stabilizing helix 6 within p24 Gag, ensuring that escape occurs at a significant cost. A very similar role is played by Thr-180, which is also an escape residue, but within a second p24 Gag epitope associated with immune control. Analysis of HIV type 1 gag in 206 B*57/5801-positive subjects reveals three principle alternative TW10-associated variants, and each is strongly linked to concomitant additional variants within p24 Gag, suggesting that functional constraints operate against their occurrence alone. The extreme conservation of p24 Gag and the predictable nature of escape variation resulting from these tight functional constraints indicate that p24 Gag may be a critical immunogen in vaccine design and suggest novel vaccination strategies to limit viral escape options from such epitopes.

Towards an HIV cure: a global scientific strategy

Given the limitations of antiretroviral therapy and recent advances in our understanding of HIV persistence during effective treatment, there is a growing recognition that a cure for HIV infection is both needed and feasible. The International AIDS Society convened a group of international experts to develop a scientific strategy for research towards an HIV cure. Several priorities for basic, translational and clinical research were identified. This Opinion article summarizes the groups recommended key goals for the international community.

Immune Selection for Altered Antigen Processing Leads to Cytotoxic T Lymphocyte Escape in Chronic HIV-1 Infection

Mutations within cytotoxic T lymphocyte (CTL) epitopes impair T cell recognition, but escape mutations arising in flanking regions that alter antigen processing have not been defined in natural human infections. In human histocompatibility leukocyte antigen (HLA)-B57+ HIV-infected persons, immune selection pressure leads to a mutation from alanine to proline at Gag residue 146 immediately preceding the NH2 terminus of a dominant HLA-B57–restricted epitope, ISPRTLNAW. Although N-extended wild-type or mutant peptides remained well-recognized, mutant virus–infected CD4 T cells failed to be recognized by the same CTL clones. The A146P mutation prevented NH2-terminal trimming of the optimal epitope by the endoplasmic reticulum aminopeptidase I. These results demonstrate that allele-associated sequence variation within the flanking region of CTL epitopes can alter antigen processing. Identifying such mutations is of major relevance in the construction of vaccine sequences.

Virological and immunological effects of treatment interruptions in HIV-1 infected patients with treatment failure.

ObjectiveTo analyse the immunological and virological effects of treatment interruptions in HIV-1-infected patients with treatment failure and multidrug-resistant virus. MethodsDrug susceptibility was assessed using Antivirogram and genotypic analysis was based on population and clonal sequencing for 48 patients who had interrupted treatment (⩾ 2 months). ResultsTreatment interruption resulted in viral load increases (mean 0.7 log10 copies/ml;P = 0.0001) and CD4 cell count decreases (mean 89 × 106 cells/l;P = 0.0001). A complete shift to wild-type virus at the phenotypic, genotypic and clonal level was observed in 28/45 patients. These patients differed from those that did not show a shift to wild type in baseline CD4 cell counts (192 versus 59 × 106 cells/l;P = 0.007) and in the relationship between baseline viral load and CD4 cell count (no correlation versus a significant negative correlation;P = 0.008). Response to re-initiation of treatment fell with increasing viral load [relative hazard (RH) 0.33;P = 0.001] and with increasing total number of drugs with reduced susceptibility (RH 0.51;P = 0.0003); it improved with the number of new drugs received (RH 2.12;P = 0.0002) and a shift to wild type (RH 5.22, P = 0.006). ConclusionsChanges in surrogate markers suggest that treatment provided benefit in spite of virological failure and resistant virus. Although patients with a shift to wild-type virus responded better in the short term to treatment re-initiation, the long-term effects are not known and the risk of immune deterioration needs to be carefully considered.

Barriers to a cure for HIV: new ways to target and eradicate HIV-1 reservoirs

Antiretroviral therapy for HIV infection needs lifelong access and strict adherence to regimens that are both expensive and associated with toxic effects. A curative intervention will be needed to fully stop the epidemic. The failure to eradicate HIV infection during long-term antiretroviral therapy shows the intrinsic stability of the viral genome in latently infected CD4T cells and other cells, and possibly a sustained low-level viral replication. Heterogeneity in latently infected cell populations and homoeostatic proliferation of infected cells might affect the dynamics of virus production and persistence. Despite potent antiretroviral therapy, chronic immune activation, inflammation, and immune dysfunction persist, and are likely to have important effects on the size and distribution of the viral reservoir. The inability of the immune system to recognise cells harbouring latent virus and to eliminate cells actively producing virus is the biggest challenge to finding a cure. We look at new approaches to unravelling the complex virus-host interactions that lead to persistent infection and latency, and discuss the rationale for combination of novel treatment strategies with available antiretroviral treatment options to cure HIV.

Capture and transfer of HIV-1 particles by mature dendritic cells converges with the exosome-dissemination pathway

Exosomes are secreted cellular vesicles that can be internalized by dendritic cells (DCs), contributing to antigen-specific naive CD4(+) T-cell activation. Here, we demonstrate that human immunodeficiency virus type 1 (HIV-1) can exploit this exosome antigen-dissemination pathway intrinsic to mature DCs (mDCs) for mediating trans-infection of T lymphocytes. Capture of HIV-1, HIV-1 Gag-enhanced green fluorescent protein (eGFP) viral-like particles (VLPs), and exosomes by DCs was up-regulated upon maturation, resulting in localization within a CD81(+) compartment. Uptake of VLPs or exosomes could be inhibited by a challenge with either particle, suggesting that the expression of common determinant(s) on VLP or exosome surface is necessary for internalization by mDCs. Capture by mDCs was insensitive to proteolysis but blocked when virus, VLPs, or exosomes were produced from cells treated with sphingolipid biosynthesis inhibitors that modulate the lipid composition of the budding particles. Finally, VLPs and exosomes captured by mDCs were transmitted to T lymphocytes in an envelope glycoprotein-independent manner, underscoring a new potential viral dissemination pathway.

HIV dynamics and T-cell immunity after three structured treatment interruptions in chronic HIV-1 infection.

ObjectiveTo evaluate whether controlled re-exposures to autologous HIV-1 could boost HIV-specific immunity and limit virus replication in patients with chronic HIV-1 infection. Patients and designSubjects with at least 2 years virus suppression during antiretroviral therapy and a CD4 : CD8 ratio > 1 were randomly assigned to interrupt highly active antiretroviral treatment (HAART) three times (n = 12) or to continue their previous HAART (n = 14). ResultsIn 10/12 interrupter patients a rebound of HIV-1 RNA was detected in all three structured treatment interruptions (STI). Plasma virus doubling time was shorter during the first STI than in the second and third STI, corresponding to an average 13% reduction in viral basic reproductive rate. However, the mean time before plasma viral load rose to > 50 copies/ml was significantly shorter in the second and third STI. The average frequency of HIV-specific CD8 T cells in the interrupter patients at the end of the third STI cycle was significantly higher compared with the baseline and the end of the first STI. A substantial increase in HIV-specific CD8 T cell frequencies was found in four interrupter patients, whereas there were no changes in all 14 non-interrupter individuals. A weak p24-specific T helper response developed in 5/12 interrupter patients compared with no response in non-interruptors, but these responses were transient and disappeared rapidly. ConclusionThe increase in the control of viral replication, and positive effects of STI on immune responses in this population should encourage the further development of HIV-specific immune-based therapeutic strategies.

Comparative transcriptomics of extreme phenotypes of human HIV-1 infection and SIV infection in sooty mangabey and rhesus macaque

High levels of HIV-1 replication during the chronic phase of infection usually correlate with rapid progression to severe immunodeficiency. However, a minority of highly viremic individuals remains asymptomatic and maintains high CD4⁺ T cell counts. This tolerant profile is poorly understood and reminiscent of the widely studied nonprogressive disease model of SIV infection in natural hosts. Here, we identify transcriptome differences between rapid progressors (RPs) and viremic nonprogressors (VNPs) and highlight several genes relevant for the understanding of HIV-1-induced immunosuppression. RPs were characterized by a specific transcriptome profile of CD4⁺ and CD8⁺ T cells similar to that observed in pathogenic SIV-infected rhesus macaques. In contrast, VNPs exhibited lower expression of interferon-stimulated genes and shared a common gene regulation profile with nonpathogenic SIV-infected sooty mangabeys. A short list of genes associated with VNP, including CASP1, CD38, LAG3, TNFSF13B, SOCS1, and EEF1D, showed significant correlation with time to disease progression when evaluated in an independent set of CD4⁺ T cell expression data. This work characterizes 2 minimally studied clinical patterns of progression to AIDS, whose analysis may inform our understanding of HIV pathogenesis.

HIV-1 reverse transcriptase inhibitor resistance mutations and fitness: A view from the clinic and ex vivo

Genetic diversity plays a key role in human immunodeficiency virus (HIV) adaptation, providing a mechanism to escape host immune responses and develop resistance to antiretroviral drugs. This process is driven by the high-mutation rate during DNA synthesis by reverse transcriptase (RT), by the large viral populations, by rapid viral turnover, and by the high-recombination rate. Drugs targeting HIV RT are included in all regimens of highly active antiretroviral therapy (HAART), which helps to reduce the morbidity and mortality of HIV-infected patients. However, the emergence of resistant viruses is a significant obstacle to effective long-term management of HIV infection and AIDS. The increasing complexity of antiretroviral regimens has favored selection of HIV variants harboring multiple drug resistance mutations. Evolution of drug resistance is characterized by severe fitness losses when the drug is not present, which can be partially overcome by compensatory mutations or other adaptive changes that restore replication capacity. Here, we review the impact of mutations conferring resistance to nucleoside and nonnucleoside RT inhibitors on in vitro and in vivo fitness, their involvement in pathogenesis, persistence upon withdrawal of treatment, and transmission. We describe the techniques used to estimate viral fitness, the molecular mechanisms that help to improve the viral fitness of drug-resistant variants, and the clinical implications of viral fitness data, by exploring the potential relationship between plasma viral load, drug resistance, and disease progression.