Gianfranco Pancino

Post-Treatment HIV-1 Controllers with a Long-Term Virological Remission after the Interruption of Early Initiated Antiretroviral Therapy ANRS VISCONTI Study

Combination antiretroviral therapy (cART) reduces HIV-associated morbidities and mortalities but cannot cure the infection. Given the difficulty of eradicating HIV-1, a functional cure for HIV-infected patients appears to be a more reachable short-term goal. We identified 14 HIV patients (post-treatment controllers [PTCs]) whose viremia remained controlled for several years after the interruption of prolonged cART initiated during the primary infection. Most PTCs lacked the protective HLA B alleles that are overrepresented in spontaneous HIV controllers (HICs); instead, they carried risk-associated HLA alleles that were largely absent among the HICs. Accordingly, the PTCs had poorer CD8+ T cell responses and more severe primary infections than the HICs did. Moreover, the incidence of viral control after the interruption of early antiretroviral therapy was higher among the PTCs than has been reported for spontaneous control. Off therapy, the PTCs were able to maintain and, in some cases, further reduce an extremely low viral reservoir. We found that long-lived HIV-infected CD4+ T cells contributed poorly to the total resting HIV reservoir in the PTCs because of a low rate of infection of naïve T cells and a skewed distribution of resting memory CD4+ T cell subsets. Our results show that early and prolonged cART may allow some individuals with a rather unfavorable background to achieve long-term infection control and may have important implications in the search for a functional HIV cure.

SAMHD1 restricts the replication of human immunodeficiency virus type 1 by depleting the intracellular pool of deoxynucleoside triphosphates

SAMHD1 restricts the infection of dendritic and other myeloid cells by human immunodeficiency virus type 1 (HIV-1), but in lentiviruses of the simian immunodeficiency virus of sooty mangabey (SIVsm)–HIV-2 lineage, SAMHD1 is counteracted by the virion-packaged accessory protein Vpx. Here we found that SAMHD1 restricted infection by hydrolyzing intracellular deoxynucleoside triphosphates (dNTPs), lowering their concentrations to below those required for the synthesis of the viral DNA by reverse transcriptase (RT). SAMHD1-mediated restriction was alleviated by the addition of exogenous deoxynucleosides. An HIV-1 with a mutant RT with low affinity for dNTPs was particularly sensitive to SAMHD1-mediated restriction. Vpx prevented the SAMHD1-mediated decrease in dNTP concentration and induced the degradation of human and rhesus macaque SAMHD1 but had no effect on mouse SAMHD1. Nucleotide-pool depletion could be a general mechanism for protecting cells from infectious agents that replicate through a DNA intermediate.

HIV controllers exhibit potent CD8 T cell capacity to suppress HIV infection ex vivo and peculiar cytotoxic T lymphocyte activation phenotype

Some rare HIV-1-infected individuals, referred to as HIV controllers (HIC), have persistently undetectable plasma viral load in the absence of therapy. This control of HIV-1 replication has been associated with a strong, multifunctional specific CD8+ T cell response. However, no direct link between this immune response and the control of viremia has so far been provided. We investigated parameters of specific CD8+ T cell response and in vitro susceptibility to HIV-1 infection in 11 HIC. We found high frequencies of HIV-specific CD8+ T cells. Interestingly, these cells expressed the activation marker HLA-DR but not CD38. This unique phenotype differentiates HIV-specific CD8+ T cells from HIC and noncontroller subjects and likely reflects a high potential to expand upon exposure to antigen and a capacity to exert effector functions. Accordingly, although CD4+ T cells from HIC were fully susceptible to HIV-1 superinfection, their CD8+ T cells effectively suppressed HIV-1 infection. Remarkably, this potent anti-HIV activity was observed without prior stimulation of CD8+ T cells. This activity was not mediated by secreted inhibitory factors but was due to the elimination of infected CD4+ T cells and was observed only with autologous CD4+ T cells, indicating an HLA-restricted cytotoxic mechanism. This constitutive antiviral capacity of CD8+ T cells could account for the control of viral replication in HIC.

Cutting Edge: Increased NK Cell Activity in HIV-1-Exposed but Uninfected Vietnamese Intravascular Drug Users

We addressed the role of innate immunity in the protection against HIV-1 infection by studying NK cell function in 37 Vietnamese intravascular drug users (IDUs), who appeared to remain HIV-1 uninfected despite many years of high-risk exposure (exposed uninfected, EU), 10 IDUs who underwent seroconversion and 28 unexposed blood donors. Main results were: NK cell lytic activities against both the NK-susceptible K562 cell line and the NK-resistant Daudi cell line were significantly augmented in EU IDUs compared with either controls or seroconverters before or after seroconversion; NK cells producing the cytokines IFN-γ and TNF-α and the β chemokines CCL3, CCL4, and CCL5 were also increased in the EU IDUs, either after in vitro activation or without stimulation. The finding of an enhanced NK cell function in EU IDUs, especially compared with IDUs who became HIV-1 infected, supports the hypothesis that NK cells contribute to the protection against HIV-1 infection.

Heterogeneity in HIV Suppression by CD8 T Cells from HIV Controllers: Association with Gag-Specific CD8 T Cell Responses

“HIV controllers” (HICs) are rare individuals in whom HIV-1 plasma viral load remains undetectable without antiretroviral treatment. This spontaneous viral control in HICs is usually associated to strong functional HIV-specific CD8+ T cell responses. Accordingly, we have recently shown that CD8+ T cells from HICs strongly suppress ex vivo HIV-1 infection of autologous CD4+ T cells, suggesting a crucial role of this response in vivo. Knowledge of the mechanisms underlying the CD8+ T cell antiviral activity might help to develop effective T cell-based vaccines. In the present work, we further characterized the HIV-suppressive capacity of CD8+ T cells in 19 HICs. CD8+ T cells from 14 of the 19 HICs showed strong HIV-suppressive capacity ex vivo. This capacity was stable over time and was partially effective even on other primate lentiviruses. HIV-suppressive capacity of CD8+ T cells correlated strongly with the frequency of HIV-specific CD8+ T cells, and in particular of Gag-specific CD8+ T cells. We also identified five HICs who had weak HIV-suppressive CD8+ T cell capacities and HIV-specific CD8+ T cell responses. Among these five HICs, at least three had highly in vitro replicative viruses, suggesting that the control of viremia in these patients is not due to replication-defective viruses. These results, on the one hand, suggest the importance of Gag responses in the antiviral potency of CD8+ T cells from HICs and, on the other hand, propose that other host mechanisms may contribute to restraining HIV infection in HICs.

Human TRIM Gene Expression in Response to Interferons

Background Tripartite motif (TRIM) proteins constitute a family of proteins that share a conserved tripartite architecture. The recent discovery of the anti-HIV activity of TRIM5α in primate cells has stimulated much interest in the potential role of TRIM proteins in antiviral activities and innate immunity. Principal Findings To test if TRIM genes are up-regulated during antiviral immune responses, we performed a systematic analysis of TRIM gene expression in human primary lymphocytes and monocyte-derived macrophages in response to interferons (IFNs, type I and II) or following FcγR-mediated activation of macrophages. We found that 27 of the 72 human TRIM genes are sensitive to IFN. Our analysis identifies 9 additional TRIM genes that are up-regulated by IFNs, among which only 3 have previously been found to display an antiviral activity. Also, we found 2 TRIM proteins, TRIM9 and 54, to be specifically up-regulated in FcγR-activated macrophages. Conclusions Our results present the first comprehensive TRIM gene expression analysis in primary human immune cells, and suggest the involvement of additional TRIM proteins in regulating host antiviral activities.

Restriction of HIV-1 replication in macrophages and CD4+ T cells from HIV controllers

How HIV controllers (HICs) maintain undetectable viremia without therapy is unknown. The strong CD8(+) T-cell HIV suppressive capacity found in many, but not all, HICs may contribute to long-lasting viral control. However, other earlier defense mechanisms may be involved. Here, we examined intrinsic HIC cell resistance to HIV-1 infection. After in vitro challenge, monocyte-derived macrophages and anti-CD3-activated CD4(+) T cells from HICs showed low HIV-1 susceptibility. CD4 T-cell resistance was independent of HIV-1 coreceptors and affected also SIVmac infection. CD4(+) T cells from HICs expressed ex vivo higher levels of p21(Waf1/Cip1), which has been involved in the control of HIV-1 replication, than cells from control subjects. However, HIV restriction in anti-CD3-activated CD4(+) T cells and macrophages was not associated with p21 expression. Restriction inhibited accumulation of reverse transcripts, leading to reduction of HIV-1 integrated proviruses. The block could be overcome by high viral inocula, suggesting the action of a saturable mechanism. Importantly, cell-associated HIV-1 DNA load was extremely low in HICs and correlated with CD4(+) T-cell permissiveness to infection. These results point to a contribution of intrinsic cell resistance to the control of infection and the containment of viral reservoir in HICs.

Reduced CD4 T cell activation and in vitro susceptibility to HIV-1 infection in exposed uninfected Central Africans

BackgroundEnvironmentally driven immune activation was suggested to contribute to high rates of HIV-1 infection in Africa. We report here a study of immune activation markers and susceptibility to HIV-1 infection in vitro of forty-five highly exposed uninfected partners (EUs) of HIV-1 infected individuals in Central African Republic, in comparison with forty-four low-risk blood donors (UCs).ResultsAnalysis of T lymphocyte subsets and activation markers in whole blood showed that the absolute values and the percentage of HLA-DR+CD4 T cells and of CCR5+CD4 T cells were lower in the EUs than in the UCs (p = 0.0001). Mutations in the CCR5 coding region were not found in either group. Susceptibility to in vitro infection of unstimulated peripheral blood mononuclear cells, prior of PHA activation, was decreased in EUs compared to UCs, either using a CXCR4-tropic or a CCR5-tropic HIV-1 strain (p = 0.02 and p = 0.05, respectively). Levels of MIP-1β, but not of MIP-1α or RANTES, in the supernatants of PHA-activated PBMC, were higher in the EUs than in the UCs (p = 0.007).ConclusionWe found low levels of CD4 T cell activation and reduced PBMC susceptibility to HIV-1 infection in Central African EUs, indicating that both may contribute to the resistance to HIV-1 infection.

The Human Immunodeficiency Virus Type 2 Vpx Protein Usurps the CUL4A-DDB1DCAF1 Ubiquitin Ligase To Overcome a Postentry Block in Macrophage Infection

ABSTRACT The human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV) genomes encode several auxiliary proteins that have increasingly shown their importance in the virus-host relationship. One of these proteins, Vpx, is unique to the HIV-2/SIVsm lineage and is critical for viral replication in macrophages. The functional basis for this requirement, as well as the Vpx mode of action, has remained unexplained, and it is all the more enigmatic that HIV type 1 (HIV-1), which has no Vpx counterpart, can infect macrophages. Here, we underscore DCAF1 as a critical host effector of Vpx in its ability to mediate infection and long-term replication of HIV-2 in human macrophages. Vpx assembles with the CUL4A-DDB1 ubiquitin ligase through DCAF1 recruitment. Precluding Vpx present in the incoming virions from recruiting DCAF1 in target macrophages leads to a postentry block characterized by defective accumulation of HIV-2 reverse transcripts. In addition, Vpx from SIVsm functionally complements Vpx-defective HIV-2 in a DCAF1-binding-dependent manner. Altogether, our data point to a mechanism in which Vpx diverts the Cul4A-DDB1DCAF1 ligase to inactivate an evolutionarily conserved factor, which restricts macrophage infection by HIV-2 and closely related simian viruses.

Replication-competent HIV strains infect HIV controllers despite undetectable viremia (ANRS EP36 study).

The replicative potential of HIV-1 strains in a well-characterized group of eight HIV controllers was investigated. Replication-competent viruses were detected in CD4 T-cell co-culture supernatants from all HIV controllers. The phylogenetic analysis of C2V4 suggested viral evolution or co-infection or superinfection in two out of the four patients analysed. The vif and vpr genes were normal. Infection with HIV-1 variants with attenuated replicative capacity cannot be a general factor accounting for undetectable viraemia in HIV controllers.