Altered interplay between gut mucosa and microbiota during treated HIV infection may possibly contribute to increased bacterial translocation and chronic immune activation, both of which are predictors of morbidity and mortality. Although a dysbiotic gut microbiota has recently been reported in HIV+ individuals, the metagenome gene pool associated with HIV infection remains unknown. The aim of this study is to characterize the functional gene content of gut microbiota in HIV+ patients and to define the metabolic pathways of this bacterial community, which is potentially associated with immune dysfunction. We determined systemic markers of innate and adaptive immunity in a cohort of HIV-infected individuals on successful antiretroviral therapy without comorbidities and in healthy non-HIV-infected subjects. Metagenome sequencing revealed an altered functional profile, with enrichment of the genes involved in various pathogenic processes, lipopolysaccharide biosynthesis, bacterial translocation, and other inflammatory pathways. In contrast, we observed depletion of genes involved in amino acid metabolism and energy processes. Bayesian networks showed significant interactions between the bacterial community, their altered metabolic pathways, and systemic markers of immune dysfunction. This study reveals altered metabolic activity of microbiota and provides novel insight into the potential host-microbiota interactions driving the sustained inflammatory state in successfully treated HIV-infected patients.

Cytolytic CD8 T cells play a crucial role in the control and elimination of virus-infected cells and are a major focus of HIV cure efforts. However, it has been shown that HIV-specific CD8 T cells are infrequently found within germinal centers (GCs), a predominant site of active and latent HIV infection. We demonstrate that HIV infection induces marked changes in the phenotype, frequency, and localization of CD8 T cells within the lymph node (LN). Significantly increased frequencies of CD8 T cells in the B cell follicles and GCs were found in LNs from treated and untreated HIV-infected individuals. This profile was associated with persistent local immune activation but did not appear to be directly related to local viral replication. Follicular CD8 (fCD8) T cells, despite compromised cytokine polyfunctionality, showed good cytolytic potential characterized by high ex vivo expression of granzyme B and perforin. We used an anti-HIV/anti-CD3 bispecific antibody in a redirected killing assay and found that fCD8 T cells had better killing activity than did non-fCD8 T cells. Our results indicate that CD8 T cells with potent cytolytic activity are recruited to GCs during HIV infection and, if appropriately redirected to kill HIV-infected cells, could be an effective component of an HIV cure strategy.

SUMMARYElimination of lymphoid tissue reservoirs is a key component of HIV eradication strategies. CD8+ T cells play a critical role in control of HIV, but their functional attributes in lymph nodes (LNs) remain unclear. Here, we show that memory, follicular CXCR5+, and HIV-specific CD8+ T cells from LNs do not manifest the properties of cytolytic CD8+ T cells. While the frequency of follicular CXCR5+ CD8+ T cells was strongly inversely associated with peripheral viremia, this association was not dependent on cytolytic CXCR5+ CD8+ T cells. Moreover, the poor cytolytic activity of LN CD8+ T cells was linked to a compartmentalized dissociation between effector programming and the transcription factor T-bet. In line with this, activation of LN CD8+ T cells only partially induced the acquisition of cytolytic functions relative to peripheral blood CD8+ T cells. These results suggest that a state of immune privilege against CD8+ T cell-mediated cytolysis exists in lymphoid tissue, potentially facilitating the persistence of HIV.

Altered interactions between the gut mucosa and bacteria during HIV infection seem to contribute to chronic immune dysfunction. A deeper understanding of how nutritional interventions could ameliorate gut dysbiosis is needed. Forty-four subjects, including 12 HIV viremic untreated (VU) patients, 23 antiretroviral therapy-treated (ART) virally suppressed patients (15 immunological responders and 8 non-responders) and 9 HIV controls (HIV), were blindly randomized to receive either prebiotics (scGOS/lcFOS/glutamine) or placebo (34/10) over 6 weeks in this pilot study. We assessed fecal microbiota composition using deep 16S rRNA gene sequencing and several immunological and genetic markers involved in HIV immunopathogenesis. The short dietary supplementation attenuated HIV-associated dysbiosis, which was most apparent in VU individuals but less so in ART subjects, whose gut microbiota was found more resilient. This compositional shift was not observed in the placebo arm. Significantly, declines in indirect markers of bacterial translocation and T-cell activation, improvement of thymic output, and changes in butyrate production were observed. Increases in the abundance of Faecalibacterium and Lachnospira strongly correlated with moderate but significant increases of butyrate production and amelioration of the inflammatory biomarkers soluble CD14 and high-sensitivity C-reactive protein, especially among VU. Hence, the bacterial butyrate synthesis pathway holds promise as a viable target for interventions.

Alone among herpesviruses, persistent Cytomegalovirus (CMV) markedly alters the numbers and proportions of peripheral immune cells in infected-vs-uninfected people. Because the rate of CMV infection increases with age in most countries, it has been suggested that it drives or at least exacerbates “immunosenescence”. This contention remains controversial and was the primary subject of the Third International Workshop on CMV & Immunosenescence which was held in Cordoba, Spain, 15-16th March, 2012. Discussions focused on several main themes including the effects of CMV on adaptive immunity and immunosenescence, characterization of CMV-specific T cells, impact of CMV infection and ageing on innate immunity, and finally, most important, the clinical implications of immunosenescence and CMV infection. Here we summarize the major findings of this workshop.

Immunosenescence, defined as the age-associated dysregulation and dysfunction of the immune system, is characterized by impaired protective immunity and decreased efficacy of vaccines. An increasing number of immunological, clinical and epidemiological studies suggest that persistent Cytomegalovirus (CMV) infection is associated with accelerated aging of the immune system and with several age-related diseases. However, current evidence on whether and how human CMV (HCMV) infection is implicated in immunosenescence and in age-related diseases remains incomplete and many aspects of CMV involvement in immune aging remain controversial. The attendees of the 4th International Workshop on "CMV & Immunosenescence", held in Parma, Italy, 25-27th March, 2013, presented and discussed data related to these open questions, which are reported in this commentary.

Relationship between thymic function and elderly survival has been suspected, despite the fact that formal proof is elusive due to technical limitations of thymic function-related markers. The newly described sj/β-TREC ratio allows now, by overcoming these limitations, an accurate measurement of thymic output in elderly humans. Thus, the aim of this study was to determine the impact of thymic function and inflammatory markers on healthy elderly human survival. Healthy volunteers (n=151), aged over 65, were asked to participate (CARRERITAS cohort). Subjects were excluded if diagnosed of dementia or, during the last 6 months, had clinical data of infection, hospital admission, antitumor therapy, or any treatment that could influence the immune status. Thymic function (sj/β-TREC ratio), CD4:CD8 T cell ratio, C-reactive protein, interleukin-6, and neutrophilia were determined from basal samples. All basal variables and age were associated with 2-year allcause mortality. Multivariate analysis showed that only thymic function and C-reactive protein were independently associated with time to death. In conclusion, we show, for the first time, the direct role of thymic function in human survival. C-reactive protein raise is also a marker of mortality in the healthy elderly, in a thymic-independent way.

IntroductionAn adequate immune response is the result of a fine balance between a multitude of activating and inhibitory signals, and disruption of this delicate balance can lead to autoimmunity or immunodeficiency. Activation signals can be negatively regulated by cell surface receptors bearing immunoreceptor tyrosine-based inhibitory motifs (ITIMs) in their cytoplasmic tail. 1 Examples of ITIM-containing receptors expressed on B cells include Fc␥RIIB, CD22, CD72, paired Ig-like receptor (PIR)-B, CD85j, Fc receptorlike (FCRL)4, and CD305. [2][3][4][5] The coligation of the B-cell receptor (BCR) and ITIM-containing receptors results in the attenuation of BCR-mediated signals. 3,5,6 Depending on the developmental stage or activation status, B cells express different sets of inhibitory receptors on their cell surface. 5,7,8 For example, CD305 is highly expressed on naive human B cells, and its expression is low in memory B cells, 5 whereas FCRL4 is mostly expressed on a subset of memory cells and is almost absent on naive B cells. 7 The expression of certain ITIM-containing receptors, such as FCRL4 and CD85j, is increased in specific B-cell subsets that are substantially expanded in certain disease settings, such as in HIV-infected viremic patients with high viral loads 9 and in persons exposed to Plasmodium falciparum. 10 It is acknowledged that the deregulation of the expression of these receptors contributes to the B-cell dysfunctions observed in HIV and malarial chronic infections. 11 CD300a belongs to the CD300 family of activating/inhibitory receptors whose genes are clustered in human chromosome 17. 12 CD300a is a type I transmembrane receptor with an IgV-like extracellular domain and a cytoplasmic tail that has 3 classic ITIM motifs 12,13 and is expressed on cells of both lymphoid and myeloid lineages. 12 Its ligation is capable of inhibiting natural killer cell-mediated cytotoxicity, 13,14 Fc␥RIIa-mediated reactive oxygen species production and Ca 2ϩ flux in neutrophils, 15 Fc⑀RI-mediated activation of mast cells, 16 and eosinophil responses to eotaxin, granulocyte-macrophage colony-stimulating factor, and IL-5. 17 In a murine model of asthma, treatment of mice with a bispecific antibody linking CD300a to CCR3 reversed remodeling and airway inflammation. 18 In another in vivo study, a bispecific antibody fragment linking CD300a to IgE was able to abrogate allergic reactions. 19 Finally, a recent study showed that a bispecific antibody that links kit with CD300a abrogates the allergic reaction induced by stem cell factor in a model of anaphylaxis. 20 All these studies highlight the potential of specifically targeting CD300a for therapeutic purposes.In this study, we demonstrate that CD300a is differentially expressed on human B-cell subsets and can function as a negative regulator of BCR-mediated signaling. Furthermore, we show that the expression of this receptor is deregulated in HIV-infected patients, suggesting a potential role for CD300a in HIV-associated disease progression. The online version of thi...