HIV-2 infection is highly prevalent in West Africa and has been increasingly observed in non-African countries, mostly associated with migratory populations [1]. It has a much more benign course and lower viremia than HIV-1 [2], though with similar clinical spectra. Half of the HIV-2 infected patients with less than 200 CD4+ T-cells/μl exhibit undetectable viremia, despite harbouring numbers of infected cells comparable to their HIV-1 counterparts [3]. Moreover, CD4+ T-cell loss occurs in direct association with progressive immune activation in both infections, though the depletion rate is much slower in HIV-2 [2,4]. HIV-1 disease progression has been linked to disruption of gut-associated lymphoid tissue (GALT) and increased levels of microbial translocation, leading to systemic immune activation. There are currently no data on the impact of HIV-2 on GALT. Here, we provide evidence of HIV-2 replication in the gut despite the low viremia, which was associated with major mucosal disruption and CD4+ T-cell depletion that recovered upon antiretroviral treatment (ART). An 18-year-old man, from Guinea-Bissau, with HIV-2 infection possibly acquired by vertical transmission, presented with mild diarrhoea since the first year of life. Colonoscopy showed loss of haustra and rectal ulcers, with moderate lymphoplasmocytic and neutrophilic infiltrates in rectal biopsies (Fig. 1a,b). Circulating CD4+ T-cells were low (19%, 103 cells/μl), in association with hyperimmune activation (Fig. 1c) and detectable viremia (4575 RNAcopies/ml), albeit at levels much lower than those found in HIV-1 infection. There was a significant depletion of CD4+ T-cells and an increase in CD8 T-cells in sigmoid lamina propria (Fig. 1a). This ratio inversion was associated with increased regulatory T-cells (Treg, FOXP3+) and decreased interleukin (IL)-17 producing cells (Fig. 1a), an immunological profile strikingly similar to that described for HIV-1 infected individuals.Fig. 1: Gut disturbances in an HIV-2 infected patient, and their recovery upon antiretroviral therapy.(a) Longitudinal evaluation of sigmoid mucosa: colonoscopy images and lamina propria lymphocyte populations assessed by immunohistochemistry (reference healthy controls’ counts/mm2: CD4+: 501 ± 56, n = 19; CD8+: 202 ± 36, n = 19; FOXP3+: 69 ± 19, n = 17; IL-17+: 123 ± 26, n = 15). (b) Haematoxylin-eosin staining of colon biopsies collected pre-antiretroviral treatment (ART) and of surgical piece (1 year post-ART). Dashed lines highlight inflammatory infiltrates and ulcerated regions. (c) Immune activation markers assessed by flow cytometry, numbers inside gates indicate frequency (reference healthy controls’ frequencies, n = 16: 1.2 ± 0.1 and 4.4 ± 1.4 of HLA-DR+CD38+ within CD4+ and CD8 T-cells, respectively; 4.6 ± 0.7 of CD16+CD14 bright cells within monocytes). (d) Levels of viral replication in the gut pre-ART assessed by immunohistochemistry against HIV-2 Gag (anti-SIV p27 that cross-reacts with HIV-2 p26, AIDS Research and Reference Reagent Program, Division of AIDS, NIAID, from Dr P. Szawlowski). Arrows indicate positive cells. Scale bars = 50 μm.These gut disturbances were accompanied by an increase in serum markers usually linked with high levels of microbial translocation, assessed as previously described [5]: plasma lipopolysaccharide (136 pg/ml), serum lipopolysaccharide binding protein (1.2 μg/ml) and soluble-CD14 (3.2 μg/ml), as well as systemic immune activation (Fig. 1c). Thus, our findings support a contribution of microbial translocation to HIV-2 pathogenesis, adding to this ongoing debate [5,6]. Local viral replication is considered a main determinant of HIV-1 associated mucosal disturbances. We found expression of HIV-2 Gag protein in different colon segments (Fig. 1d), which supports a significant degree of mucosal HIV-2 replication, despite the low viremia. This is in line with our previous findings of ongoing viral replication in HIV-2 patients with undetectable circulating virus, and similar levels of cell-associated viral burden in the two infections [3]. ART (emtricitabine/tenofovir/saquinavir/ritonavir) was initiated with clear virological (undetectable viremia) and immunological responses (845 CD4+ T-cells/μl, 25.5%; 1-year post-ART), accompanied by a progressive decline in systemic activation markers (Fig. 1c). Notably, our patient presented a marked delay of puberty (bone age of 12.5 years), and, similar to HIV-1 infected children, an interstitial lymphoid pneumonia that fully resolved with therapy. Conversely, diarrhoea persisted with exacerbation of inflammatory histologic findings (transmural chronic inflammatory infiltrate with lymphoid aggregates, sparse noncaseating granulomas and mucosal architectural distortion), mimicking Crohn's disease, leading to the development of rectal stenosis that required endoscopic dilatations and segmental resection (Fig. 1a,b). In spite of these disturbances, there was a recovery of lamina propria lymphocyte imbalances (Fig. 1a), as well as lack of evidence of HIV-2 replication (Gag expression, data not shown). It is plausible that this paradoxical evolution represents a form of late immunological reconstitution disease because, at that time, there was already a recovery of mucosal CD4+ T-cells and IL-17 production (Fig. 1a). Gut manifestations disappeared after prolonged ART, with sustained immunological response, both in gut mucosa (Fig. 1a) and peripheral blood (716 CD4+ T-cells/μl, 48.1%; 5 years post-ART). Thus, our results represent a rational basis for starting ART in HIV-2 infection irrespectively of viremia. There are currently no randomized trials addressing ART in HIV-2 infected individuals [1]. Longitudinal studies suggest that HIV-2 infected patients have a limited response to ART, specifically a reduced CD4+ T-cell recovery as compared with HIV-1 [2,3]. This might be related to virologic inefficacy, as antiretroviral drugs have not been specifically designed for HIV-2, and genotypic and phenotypic resistance studies are limited precluding an adequate choice of the best regimens [1]. Alternatively, the prolonged course of HIV-2 disease might lead to irreversible damage of secondary lymphoid organs, thereby preventing complete immunological recovery. In conclusion, this is the first study of mucosal CD4+ T-cell depletion with loss of IL-17 producing cells in HIV-2 infection, which was shown to recover upon suppression of ongoing low-level viral replication with ART. Our results represent an argument in favour of treating HIV infection in the context of reduced viremia. Acknowledgements S.M.F., A.R.P., C.F. and RT performed research; S.M.F., L.C. and S.E.P. did the collection of clinical data; S.M.F., R.M.M.V. and A.E.S designed the study, analysed data and wrote the article. This work was supported by the Fundação para a Ciência e Tecnologia (FCT), and the Programa Operacional Ciência e Inovação 2010 (PIC/IC/82712/2007 to A.E.S.). S.M.F., A.R.P. and R.T. received FCT scholarships. Conflicts of interest There are no conflicts of interest.
Chronic Granulomatous Disease (CGD) results from primary defects in phagocytic reactive oxygen species (ROS) production. T-cell evaluation is usually neglected during patients' follow-up, although T-cell depletion has been reported in CGD through unknown mechanisms. We describe here a 36-year-old patient with X-linked CGD with severe CD4 T-cell depletion below 200 CD4 T-cells/l, providing insights into the mechanisms that underlie T-cell loss in the context of oxidative burst defects. In addition to the typical infections, the patient featured a progressive T-cell loss associated with persistent lymphocyte activation, expansion of IL-17-producing CD4 T-cells, and impaired thymic activity leading to a reduced replenishment of the T-cell pool. A relative CD4 depletion was also found at the gut mucosal level, though no bias to IL-17-production was documented. This immunological pattern of exhaustion of immune resources favors prompt, potentially curative, therapeutic interventions in CGD patients, namely stem-cell transplantation or gene therapy. Moreover, this clinical case raises new research questions on the interplay of ROS production and T-cell homeostasis and immune senescence.
ABSTRACT A unique HIV-host equilibrium exists in untreated HIV-2-infected individuals. This equilibrium is characterized by low to undetectable levels of viremia throughout the disease course, despite the establishment of disseminated HIV-2 reservoirs at levels comparable to those observed in untreated HIV-1 infection. Although the clinical spectrum is similar in the two infections, HIV-2 infection is associated with a much lower rate of CD4 T-cell decline and has a limited impact on the mortality of infected adults. Here we investigated HIV-2 infection of the human thymus, the primary organ for T-cell production. Human thymic tissue and suspensions of total or purified CD4 single-positive thymocytes were infected with HIV-2 or HIV-1 primary isolates using either CCR5 or CXCR4 coreceptors. We found that HIV-2 infected both thymic organ cultures and thymocyte suspensions, as attested to by the total HIV DNA and cell-associated viral mRNA levels. Nevertheless, thymocytes featured reduced levels of intracellular Gag viral protein, irrespective of HIV-2 coreceptor tropism and cell differentiation stage, in agreement with the low viral load in culture supernatants. Our data show that HIV-2 is able to infect the human thymus, but the HIV-2 replication cycle in thymocytes is impaired, providing a new model to identify therapeutic targets for viral replication control. IMPORTANCE HIV-1 infects the thymus, leading to a decrease in CD4 T-cell production that contributes to the characteristic CD4 T-cell loss. HIV-2 infection is associated with a very low rate of progression to AIDS and is therefore considered a unique naturally occurring model of attenuated HIV disease. HIV-2-infected individuals feature low to undetectable plasma viral loads, in spite of the numbers of circulating infected T cells being similar to those found in patients infected with HIV-1. We assessed, for the first time, the direct impact of HIV-2 infection on the human thymus. We show that HIV-2 is able to infect the thymus but that the HIV-2 replication cycle in thymocytes is impaired. We propose that this system will be important to devise immunotherapies that target viral production, aiding the design of future therapeutic strategies for HIV control.
Objective: Memory B-cell loss has long been recognized as an important contributor to HIV immunodeficiency. HIV-2 infection, which is characterized by a slow rate of progression to AIDS and reduced to undetectable viremia, provides a unique model to investigate B-cell disturbances. Design and methods: B-cell subsets were evaluated in 38 HIV-2-infected individuals, along with markers of T-cell activation and serum levels of immunoglobulins and a major B-cell homeostatic cytokine, B-cell activating factor (BAFF). Untreated HIV-1-infected and seronegative control individuals were studied in parallel. Statistical analysis was performed using Mann–Whitney tests and Spearman's correlations. Results: We found that HIV-2 was associated with significant depletion of both unswitched (CD27+IgD+) and switched (CD27+IgDneg) memory B-cells that directly correlated with T-cell activation, even in individuals with undetectable plasma viral load. Nevertheless, the presence of detectable viremia, even at low levels, was associated with significant memory B-cell loss and higher BAFF levels. Moreover, these alterations were not recovered by antiretroviral-therapy, as treated HIV-2-infected patients showed more pronounced B-cell disturbances, possibly related to their extended length of infection. Conclusion: These first data regarding B-cell imbalances during HIV-2 infection show that, irrespective of viremia, prolonged HIV infection leads to irreversible damage of memory B-cell homeostasis.
HIV-1 mother-to-child transmission (MTCT) was evaluated in terms of the molecular characterization of the env and nef genomic regions and quantification of maternal RNA viral loads. Assignment of viral subtype was achieved by direct sequencing of PCR 1172products amplified from proviral DNA in 45 HIV-1-nontransmitting mothers (NTM), along with 13 pairs of HIV-1-transmitting mothers (TM) and their infected children (C). Analysis of the env C2V3C3 and nef sequences revealed that subtypes G and B, and their genetic combinations (AG, BG), accounted for over 84.5% of all viruses identified. The genetic structure form envA-nefG was the most commonly observed, with a lower frequency in the NTM (13.3%) compared to the TM (23.1%) group. A greater number of genetic forms was observed among NTM, namely the presence of sequences assigned to subtypes D and F, as well as the intergenetic A/J, and C/U, recombinant forms, along with a mosaic provirus with a complex putative envA-nefEGE genetic structure. No significant differences were found when RNA viral loads were evaluated as a function of the viral subtypes. Nevertheless, a relatively high quantification of HIV-1 RNA was obtained in the NTM group, emphasizing the importance of the compliance and effectiveness of therapeutic schemes to control viral replication and reduce the risk of HIV vertical transmission. V3 sequences displaying features associated with the R5 phenotype dominated in both groups. Both C2V3C3 and Nef's functional domains were conserved during HIV-1 vertical transmission.
Monocytes and myeloid dendritic cells (mDCs) are important orchestrators of innate and human immunodeficiency virus (HIV)–specific immune responses and of the generalized inflammation that characterizes AIDS progression. To our knowledge, we are the first to investigate monocyte and mDC imbalances in HIV type 2 (HIV-2)–positive patients, who typically feature reduced viremia and slow disease progression despite the recognized ability of HIV-2 to establish viral reservoirs and overcome host restriction factors in myeloid cells. We found a heightened state of monocyte and mDC activation throughout HIV-2 infection (characterized by CD14brightCD16+ expansion, as well as increased levels of soluble CD14, HLA-DR, and CD86), together with progressive mDC depletion. Importantly, HIV-2–positive patients also featured overexpression of the inhibitory molecule PD-L1 on monocytes and mDCs, which may act by limiting the production of proinflammatory molecules. These data, from patients with a naturally occurring form of attenuated HIV disease, challenge current paradigms regarding the role of monocytes in HIV/AIDS and open new perspectives regarding potential strategies to modulate inflammatory states.
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