Brigitte Autran

Superior control of HIV-1 replication by CD8+ T cells is reflected by their avidity, polyfunctionality, and clonal turnover

The key attributes of CD8+ T cell protective immunity in human immunodeficiency virus (HIV) infection remain unclear. We report that CD8+ T cell responses specific for Gag and, in particular, the immunodominant p24 epitope KK10 correlate with control of HIV-1 replication in human histocompatibility leukocyte antigen (HLA)–B27 patients. To understand further the nature of CD8+ T cell–mediated antiviral efficacy, we performed a comprehensive study of CD8+ T cells specific for the HLA-B27–restricted epitope KK10 in chronic HIV-1 infection based on the use of multiparametric flow cytometry together with molecular clonotypic analysis and viral sequencing. We show that B27-KK10–specific CD8+ T cells are characterized by polyfunctional capabilities, increased clonal turnover, and superior functional avidity. Such attributes are interlinked and constitute the basis for effective control of HIV-1 replication. These data on the features of effective CD8+ T cells in HIV infection may aid in the development of successful T cell vaccines.

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.

Perturbation of CD4+ and CD8+ T-cell repertoires during progression to AIDS and regulation of the CD4+ repertoire during antiviral therapy

The T-cell antigen receptor (TCR) repertoire was studied longitudinally by analyzing the varying lengths of the beta chain CDR3 hypervariable region during the course of HIV-1 infection and following combination antiretroviral therapy. Drastic restrictions in CD8+ T-cell repertoire usage were found at all stages of natural progression and persisted during the first six months of treatment. In contrast, significant CD4+ T-cell repertoire perturbations were not found in early stages of infection but correlated with progression to AIDS. Out of ten patients presenting with pretreatment perturbations, normalization of the CD4+ repertoire was observed in eight good responders, but not in two cases of unsuccessful therapy. These results indicate that, besides CD4+ cell count rise, an efficient control of HIV replication may allow qualitative modifications of the CD4+ repertoire balance.

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.

Multicentric Castleman's disease in HIV infection: a clinical and pathological study of 20 patients.

ObjectivesTo describe, in a retrospective study, the clinical and pathological spectrum of multicentric Castlemans disease (MCD) in HIV infection. PatientsThe diagnosis of MCD was established by lymph node biopsy in 20 HIV-infected patients. All patients had been HIV-infected by sexual contact. At diagnosis, HIV infection was asymptomatic in eight patients and Kaposis sarcoma was present in 12. Mean±SD CD4+ cell count was 156 × 99 × 106/l. ResultsPatients were referred with a syndrome of fever and splenomegaly (100%), peripheral iymphadenopathy (90%), hepatomegaly (70%), severe weight loss (70%), respiratory symptoms (65%) and oedema (55%). Anaemia was a constant finding and seven (35%) patients presented with pancytopenia. Serum markers of inflammation were present in most patients: a high level of C reactive protein (90%), poiyclonal hypergammaglobulinaemia (89%) and hypoalbuminaemia (56%). The histological pattern of the lymph nodes was characterized by small hyalinized germinal centres surrounded by concentric layers of small lymphocytes, vascular hyperplasia, hyalinized vessels and large interfollicular sheets of plasma cells. Five patients were classified as plasma cell type MCD and 15 as hyaline vascular/plasma cell (mixed) type. Immunophenotyping studies (n = 1 3) demonstrated a poiyclonal B-cell process. No linkage with Epstein-Barr virus (EBV) could be demonstrated immunohistochemically using an anti-latent membrane protein-1 monoclonal antibody (n = 16) or by RNA in situ hybridization with an EBV-encoded RNA transcript-specific probe (n = 1 3). Remission was obtained with low-dose and usually single agent chemotherapy in 16 patients. During follow-up, non-Hodgkins lymphoma developed in two patients and Kaposis sarcoma in three. Fatal outcome occurred in 14 patients with a median survival of 14 months. ConclusionMCD associated with HIV infection is a distinct clinico-pathological entity that can be differentiated from other types of HIV-associated systemic lymphoproliferative disorders. It is very similar to MCD observed in non-HIV-infected patients, except for the high prevalence of pulmonary symptoms and for the stronger association with Kaposis sarcoma. Single-agent chemotherapy with vinblastine is effective and may prolong survival.

Explosion of tuberculin-specific Th1-responses induces immune restoration syndrome in tuberculosis and HIV co-infected patients.

Objectives:To test the hypothesis that an acute exacerbation of mycobacteria-specific Th1 response after HIV infection control by HAART causes immune restoration syndrome (IRS) in HIV–tuberculosis (TB) coinfected patients. Design:Prospective, multicenter study of 19 consecutive untreated HIV–TB coinfected patients included when initiating antimycobacterial therapy and sequentially evaluated during HAART and at time of IRS. IRS was defined according to classical clinical diagnostic criteria. Patients were declared IRS− if no IRS occurred within 3 months after HAART initiation. Methods:Mycobacteria-specific [purified protein derivative (PPD), ESAT-6, 85B] Th1 cells producing interferon (IFN)-γ quantified by ELISpot, in vitro production of 25 cytokines/chemokines in antigen-stimulated peripheral blood mononuclear cell (PBMC) supernatants quantified by chemiluminescence. Results:Seven patients (37%) experienced IRS (IRS+). Mycobacteria-specific (PPD) Th1 IFN-γ-producing cells increased sharply during IRS (median, 2970 spot forming cells/106 PBMC), but not the cytomegalovirus-specific responses tested as control. Only three IRS+ patients had low ESAT-6− but no 85B-specific responses. IRS− patients did not develop acute PPD-specific responses except in one case. In addition, at time of IRS a peak of PPD-specific Th1 cytokines/chemokines [interleukin (IL)-2, IL-12, IFN-γ, IP10 and monokine-induced by IFN-γ] without Th2 cytokines, and a peak of non-specific inflammatory cytokines/chemokines (TNF-α, IL-6, IL-1β, IL-10, RANTES and MCP-1) occurred. These findings were independent from CD4 cell count, viral loads or time of HAART initiation. Conclusion:An acute exacerbation of Th1 responses against mycobacterial antigens appears to cause IRS in patients co-infected with HIV and TB. This key event provides new evidence valuable for the diagnosis and treatment of IRS.

Cytofluorometric methods for assessing absolute numbers of cell subsets in blood

The enumeration of absolute levels of cells and their subsets in clinical samples is of primary importance in human immunodeficiency virus (HIV)+ individuals (CD4+ T- lymphocyte enumeration), in patients who are candidates for autotransplantation (CD34+ hematopoietic progenitor cells), and in evaluating leukoreduced blood products (residual white blood cells). These measurements share a number of technical options, namely, single- or multiple-color cell staining and logical gating strategies. These can be accomplished using single- or dual-platform counting technologies employing cytometric methods. Dual-platform counting technologies couple the percentage of positive cell subsets obtained by cytometry and the absolute cell count obtained by automated hematology analyzers to derive the absolute value of such subsets. Despite having many conceptual and technical limitations, this approach is traditionally considered as the reference method for absolute cell count enumeration. As a result, the development of single-platform technologies has recently attracted attention with several different technical approaches now being readily available. These single-platform approaches have less sources of variability. A number of reports clearly demonstrate that they provide better coefficients of variation (CVs) in multicenter studies and a lower chance to generate aberrant results. These methods are therefore candidates for the new gold standard for absolute cell assessments. The currently available technical options are discussed in this review together with the results of some cross-comparative studies. Each analytical system has its own specific requirements as far as the dispensing precision steps are concerned. The importance of precision reverse pipetting is emphasized. Issues still under development include the establishment of the critical error ranges, which are different in each test setting, and the applicability of simplified low-cost techniques to be used in countries with limited resources.

HIV AND T CELL EXPANSION IN SPLENIC WHITE PULPS IS ACCOMPANIED BY INFILTRATION OF HIV-SPECIFIC CYTOTOXIC T LYMPHOCYTES

Human immunodeficiency virus (HIV) replication and T cell proliferation were investigated in situ by a PCR-based analysis of individual microdissected splenic white pulps. Founder effects, revealed by an exquisite compartmentalization of HIV genotypes and T cells, indicated the recruitment of latently infected CD4+ T cells through highly localized antigen presentation rather than the infection of CD4+ T lymphoblasts by blood-borne virus or immune complexes. HIV-infected white pulps could be infiltrated by HIV-specific cytotoxic T lymphocytes, thereby implicating them in CD4+ T cell destruction in vivo. Together these data describe an iterative and deleterious mechanism of antigen-driven T cell recruitment and activation, as well as HIV replication and spread, with consequent destruction of the newly infected cells.

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.

Accelerated immune senescence and HIV-1 infection

A recent consensus has emerged regarding the association between chronic immune activation and poor outcome in HIV-1 infection. However, its basis remains unclear. Accumulating evidence suggests that the cells of the immune system may have a limited replicative lifespan in vivo. In this context, persistent activation during chronic HIV infection may lead to an exhaustion of immune resources. This may occur at two levels: Clonal and Global. Some HIV-1-specific CD8+ T-cells start expressing the senescence marker CD57 soon after primary infection. Persistently activated HIV-1-specific T-cell clones may eventually reach stages of replicative senescence and disappear, resulting in the specific loss of CD8+ T-cell populations important to control viral replication. In addition, HIV-1 infected individuals are characterized by the accumulation of highly differentiated CD8+ and CD4+ T-cells overtime. Together with the decline of T-cell renewal capacities, this may reflect a general ageing of the lymphocyte population. Similar observations have been done in HIV non-infected elderly individuals, which suggests that premature immunosenescence occurs in HIV-1 infection, as a result of persistent immune activation.