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Microbial diversity is associated with improved outcomes in recipients of allogeneic hematopoietic cell transplantation (allo-HCT), but the mechanism underlying this observation is unclear. In a cohort of 174 patients who underwent allo-HCT, we demonstrate that a diverse intestinal microbiome early after allo-HCT is associated with an increased number of innate-like mucosal-associated invariant T (MAIT) cells, which are in turn associated with improved overall survival and less acute graft-versus-host disease (aGVHD). Immune profiling of conventional and unconventional immune cell subsets revealed that the prevalence of Vδ2 cells, the major circulating subpopulation of γδ T cells, closely correlated with the frequency of MAIT cells and was associated with less aGVHD. Analysis of these populations using both single-cell transcriptomics and flow cytometry suggested a shift toward activated phenotypes and a gain of cytotoxic and effector functions after transplantation. A diverse intestinal microbiome with the capacity to produce activating ligands for MAIT and Vδ2 cells appeared to be necessary for the maintenance of these populations after allo-HCT. These data suggest an immunological link between intestinal microbial diversity, microbe-derived ligands, and maintenance of unconventional T cells.

International audience; Both mouse and human harbour memory phenotype CD8+ T cells specific for antigens in hosts that have not been previously exposed to these antigens. The origin and the nature of the stimuli responsible for generation of CD44hi CD8+ T cells in specific pathogen-free (SPF) mice remain controversial. It is known that microbiota plays a crucial role in the prevention and resolution of systemic infections by influencing myelopoiesis, regulating dendritic cells, inflammasome activation and promoting the production of type I and II interferons. By contrast, here we suggest that microbiota has a direct effect on generation of memory phenotype CD44hiGP33+CD8+ T cells. In SPF mice, it generates a novel GP33+CD44hiCD8+ T cell sub-population associating the properties of innate and genuine memory cells. These cells are highly enriched in the bone marrow, proliferate rapidly and express immediate effector functions. They dominate the response to LCMV and express particular TCRβ chains. The sequence of these selected TCRβ chains overlaps with that of GP33+CD8+ T cells directly selected by microbiota in the gut epithelium of SPF mice, demonstrating a common selection mechanism in gut and peripheral CD8+ T cell pool. Therefore microbiota has a direct role in priming T cell immunity in SPF mice and in the selection of TCRβ repertoires during systemic infection. We identify a mechanism that primes T cell immunity in SPF mice and may have a major role in colonization resistance and protection from infection.

The intestinal immune system can respond to invading pathogens yet maintain immune tolerance to self-antigens and microbiota. Myeloid cells are central to these processes, but the signaling pathways that underlie tolerance versus inflammation are unclear. Here we show that mice lacking Calcineurin B in CD11chighMHCII+ cells (Cnb1 CD11c mice) spontaneously develop intestinal inflammation and are susceptible to induced colitis. In these mice, colitis is associated with expansion of T helper type 1 (Th1) and Th17 cell populations and a decrease in the number of FoxP3+ regulatory T (Treg) cells, and the pathology is linked to the inability of intestinal Cnb1-deficient CD11chighMHCII+ cells to express IL-2. Deleting IL-2 in CD11chighMHCII+ cells induces spontaneous colitis resembling human inflammatory bowel disease. Our findings identify that the calcineurin–NFAT–IL-2 pathway in myeloid cells is a critical regulator of intestinal homeostasis by influencing the balance of inflammatory and regulatory responses in the mouse intestine.

INTRODUCTION Lymphoma cells are dependent on the tumor microenvironment (TME) for their survival and proliferation. Dissection of TME composition provides insight into lymphomagenesis, better prognostication, and enhancement of therapeutic options. Flow cytometry provides a robust approach for single-cell analysis. Nonetheless lack of well-defined comparator groups and/or a robust, reproducible approaches for analyzing the multidimensional data often limited such studies. In the current study, we analyzed the T cell background on a large reference set of follicular hyperplasia (FH) lymph node samples utilizing a robust standardized high dimensionality flow cytometry and a novel reproducible analytical pipeline. We then compared this baseline reference set with tumor infiltrating T cell subsets in follicular lymphoma (FL; in treatment naïve FL-NA and relapsed/refractory FL-RR sets). METHODS On behalf of the imCORE Network we analyzed 44 FH and 81 FL (35 FL-NA and 44 FL-RR) with 2 standardized flow cytometry panels (23 antigen/18-color) (Table 1). We evaluated the T cell subset distribution as well as immune checkpoint expression (TIGIT, TIM3, PD-1, CD96, LAG3, CTLA4, CD73) within analytically defined T cell clusters. Analysis was performed using semiautomated multi-step analytical pipeline as outlined in Figure 1. Using standardized instrument settings and an R-based algorithms (gaussNorm) to minimize technical variations in sample acquisition we analyzed the T-cells subpopulations using a dimensionality reduction technique (UMAP), combined with an unsupervised clustering algorithm (FlowSOM). Statistical analysis was performed using non-parametric Wilcoxon test. RESULTS In the 3 cohorts, several marked differences in the composition T cells subsets were observed. Compared to FH the FL lymph nodes were depleted for CD4 & CD8 naïve subsets (Table 2) and were characterized by an immune suppressive microenvironment enriched in specific subsets of activated T regulatory cells and exhausted memory effector cells. The pool of CD8 naïve cells was restored in FL-RR cases (Table 2). FL-NA nodes showed enrichment of T follicular regulatory cells (Tfr; Table 2) (0.9% vs 2.7%, p In association with the increase of Tfr cells, the concentration of CTLA4+, TIGIT+, PD1bright T follicular helper cells (Tfh) was reduced in FL-RR compared to FL-NA (Fig. 2C). The Tfr/Treg expansion was also associated with a marked increase in exhausted memory T cells in both CD4 and CD8 compartments (CD4 EM TP and CD8 EM DP, Table 2). In FL isolates the CD4 compartment was characterized by the expression of triple positive (CTLA4, TIGIT, PD1) phenotype in EM cells while the memory CD8 cells overexpressed TIGIT and PD1 (Fig. 2D). A smaller subpopulation of memory CD8 cells, almost undetectable in FH samples, characterized by the expression of CTLA4, PD1, TIGIT and TIM3 is expanded in FL isolates (Fig. 2D). CONCLUSION Our data suggest that change in balance between TFH and Tfr may lead to more aggressive therapy resistant disease in FL. The interplay between TFH and Tfr, has been postulated to shape the immune response in FL with TFH promoting germinal center formation and Tfr inhibiting TFH and follicular effector T cells. While both TFH and Tfr compartments are expanded in FL, in the relapsed/ refractory FL cases, the Tfr compartment is further expanded at the expense of TFH leading to more immunosuppressive background. Furthermore our study suggests a rational way of designing immune checkpoint inhibitor studies in FL. Effector memory T-cells in FL isolates show an exhausted phenotype characterized by the expression of the inhibitory receptors CTLA4, TIGIT, PD1 in the CD4 compartment, and TIGIT, PD1 in the CD8. In addition, the noteworthy expansion of TIM3+ memory CD8 cells in FL. Targeting these most highly expressed checkpoints in FL alone or in combination may provide an avenue for rational trial design. Figure 1 Figure 1. Disclosures Roshal: Celgene: Other: Provision of services; Auron Therapeutics: Other: Ownership / Equity interests; Provision of services; Physicians' Education Resource: Other: Provision of services. Dogan: Physicians' Education Resource: Honoraria; Peer View: Honoraria; Roche: Consultancy, Research Funding; Takeda: Consultancy, Research Funding; Seattle Genetics: Consultancy; EUSA Pharma: Consultancy.

Microbial diversity is associated with improved outcome in patients receiving allogeneic hematopoietic cell transplantation (allo-HCT), however, the mechanism underlying this observation is unclear. Unconventional T cells recognize specific metabolites of bacterial biosynthesis and their role in the post-HCT immunity has not yet been fully clarified. Here we have performed an observational study (n = 174 patients) using 16S rRNA sequencing of early post-HCT patient stool samples (day 7-21 after HCT) paired with multiparameter flow cytometry (performed at day 30 and day 100 after HCT) to explore the relationship between the intestinal microbiome early after HCT and the unconventional T cell populations in circulation. Our data extend findings of other groups suggesting that mucosal-associated invariant T (MAIT) cells are dependent on a diverse microbiome and are also associated with favorable allo-HCT outcome. In addition, we report for the first time that the Vδ2 subset of γδ T cells is positively correlated with MAIT cells as well as independent predictors of favorable transplant outcome. We first focused on MAIT cells as these cells respond to metabolites of the bacterial riboflavin biosynthesis pathway and should therefore be responsive to changes in the gut microbiome. MAIT cell frequency on day 30 after HCT was significantly higher in peripheral blood stem cell (PBSC) graft recipients who had higher peri-engraftment stool diversity (day 7-21; p=0.014, n=118, α-diversity measured using Simpson's reciprocal index, Figure A). Patients with higher-than-median MAIT cell frequency had improved 2-year overall survival (p=0.047, n=118 PBSC recipients, Figure B) and lower non-relapse mortality (p=0.031) compared with patients with lower-than-median frequency. High dimensional flow cytometry analysis using clustering algorithms Uniform Manifold Approximation and Projection (UMAP) and Self Organizing Map (FlowSOM) identified the Vδ2 subset of γδ T cells as the only differentially abundant population associated with higher MAIT cell frequency, and furthermore, frequencies of these two cell types were highly correlated (R=0.38, p=2.8e-05, Figure C). Vδ2 cells are activated by the bacterial metabolite, 4-hydroxy-3-methyl-but-2-enyl pyrophosphate (HMBPP), an intermediate of the microbial isoprenoid biosynthetic pathway. Vδ2 cell frequencies were higher in patients with higher stool α-diversity (p=0.0026, n=118 PBSC recipients, Figure D) and interestingly, appeared protective with regard to acute graft versus host disease (aGVHD), as we observed a higher frequency of Vδ2 cells among patients who had no or grade 1 disease compared with patients who experienced grade 2-4 aGVHD (p=0.013). We next used Linear Discriminant effect Size (LefSE) analysis to identify statistically significant differences between bacterial taxa in our groups of interest (threshold p>0.01 and effect size>4) and observed that higher MAIT and Vδ2 cell numbers are associated with higher abundance of bacteria belonging to the phylum Bacteroidetes and lower MAIT and Vδ2 cell numbers are associated with higher abundance of the members of the phylum Firmicutes. Furthermore, using the PICRUSt2 algorithm, which uses 16S amplicon abundance data to predict the abundance of functional pathways, we observed a significantly increased predicted abundance of HMBPP, the phosphoantigen ligand for Vδ2 cells, in the patients with higher circulating Vδ2 cell frequencies (p=0.00054). Our findings confirm our hypothesis that a diverse microbiota supports the reconstitution of protective unconventional T cell populations, namely MAIT and Vδ2 cells, which are in turn associated with a favorable HCT outcome. Although further studies are needed to dissect the functional contribution of these cells to the post-transplantation immune milieu, our work offers a valuable insight into the interplay between the intestinal microbiome and reconstitution of immune subsets after allo-HCT and may aid in the design of microbiota-targeted interventions. Figure 1 Figure 1. Disclosures Gomes: Xbiome: Current Employment. Zappasodi: iTeos Therapeutics: Consultancy; Astra Zeneca: Research Funding; Bristol Myers Squibb: Research Funding. Ponce: CareDx: Consultancy, Honoraria; Takeda Pharmaceuticals: Research Funding; Generon Pharmaceuticals: Consultancy; Kadmon pharmaceuticals: Consultancy, Honoraria; Ceramedix: Consultancy, Honoraria; Seres Therapeutics: Consultancy, Research Funding. Giralt: JENSENN: Membership on an entity's Board of Directors or advisory committees; SANOFI: Membership on an entity's Board of Directors or advisory committees; AMGEN: Membership on an entity's Board of Directors or advisory committees; PFIZER: Membership on an entity's Board of Directors or advisory committees; GSK: Membership on an entity's Board of Directors or advisory committees; JAZZ: Membership on an entity's Board of Directors or advisory committees; BMS: Membership on an entity's Board of Directors or advisory committees; CELGENE: Membership on an entity's Board of Directors or advisory committees; Actinnum: Membership on an entity's Board of Directors or advisory committees. Peled: Seres: Other: Intellectual Property Rights, Research Funding and Travelfees; DaVolterra: Consultancy; Other: Other: Jonathan U. Peled had filed intellectual property applications related to the microbiome (referencenumbers #62/843,849, #62/977,908, and #15/756,845); MaaT Pharma: Consultancy. Perales: Cidara: Honoraria; Celgene: Honoraria; Merck: Honoraria; MorphoSys: Honoraria; Nektar Therapeutics: Honoraria, Other; Equilium: Honoraria; Karyopharm: Honoraria; Takeda: Honoraria; Bristol-Myers Squibb: Honoraria; Kite/Gilead: Honoraria, Other; Medigene: Honoraria; Novartis: Honoraria, Other; Sellas Life Sciences: Honoraria; Servier: Honoraria; Miltenyi Biotec: Honoraria, Other; Omeros: Honoraria; Incyte: Honoraria, Other; NexImmune: Honoraria. van den Brink: Rheos: Honoraria; Merck & Co, Inc: Honoraria; Therakos: Honoraria; Amgen: Honoraria; GlaskoSmithKline: Other: has consulted, received honorarium from or participated in advisory boards; Synthekine (Spouse): Other: has consulted, received honorarium from or participated in advisory boards; Kite Pharmaceuticals: Other; Notch Therapeutics: Honoraria; Nektar Therapeutics: Honoraria; Priothera: Research Funding; Wolters Kluwer: Patents & Royalties; Juno Therapeutics: Other; Frazier Healthcare Partners: Honoraria; DKMS (nonprofit): Other; Seres: Other: Honorarium, Intellectual Property Rights, Research Fundingand Stock Options; Forty-Seven, Inc.: Honoraria; Lygenesis: Other: has consulted, received honorarium from or participated in advisory boards ; WindMILTherapeutics: Honoraria; Pharmacyclics: Other; Jazz Pharmaceuticals: Honoraria; Novartis (Spouse): Other: has consulted, received honorarium from or participated in advisory boards; Da Volterra: Other: has consulted, received honorarium from or participated in advisory boards; Ceramedix: Other: has consulted, received honorarium from or participated in advisory boards ; MagentaTherapeutics: Honoraria; Pluto Therapeutics: Current holder of stock options in a privately-held company, Other: has consulted, received honorarium from or participated in advisory boards .

Both mouse and human harbour memory phenotype CD8

The intestinal immune system can respond to invading pathogens yet maintain immune tolerance to self-antigens and microbiota. Myeloid cells are central to these processes, but the signaling pathways that underlie tolerance versus inflammation are unclear. Here we show that mice lacking Calcineurin B in CD11chighMHCII+ cells (Cnb1CD11c mice) spontaneously develop intestinal inflammation and are susceptible to induced colitis. In these mice, colitis is associated with expansion of T helper type 1 (Th1) and Th17 cell populations and a decrease in the number of FoxP3+ regulatory T (Treg) cells, and the pathology is linked to the inability of intestinal Cnb1-deficient CD11chighMHCII+ cells to express IL-2. Deleting IL-2 in CD11chighMHCII+ cells induces spontaneous colitis resembling human inflammatory bowel disease. Our findings identify that the calcineurin–NFAT–IL-2 pathway in myeloid cells is a critical regulator of intestinal homeostasis by influencing the balance of inflammatory and regulatory responses in the mouse intestine., Treg cells can maintain intestinal homeostasis and limit intestinal bowel disease. Here the authors use a mouse model of spontaneous colitis to show that calcineurin-NFAT-induced IL-2 production by dendritic cells regulates the balance between Treg and effector T cells in the gut lamina propria.

Physiologically T-regulatory cells (Treg) suppress immune responses against self-antigens preventing autoimmunity. However, in cancer they are believed to suppress anti-tumor immune response, and the presence of Treg in the tumor microenvironment has been associated with adverse outcome in most cancers. Treg are integral part of tumor microenvironment in lymphoma, and can use different mechanisms to inhibit both adaptive and immune response (including CD4, CD8, DC, macrophages, B-cells and NK cells) modulating therefore the interaction between lymphoma and the host microenvironment. Increased numbers of Treg have been associated with adverse clinical outcome in follicular lymphoma (FL) but a more favorable outcome in classical Hodgkin lymphoma (CHL). In this study we examined Treg phenotype in detail using multiparameter flow cytometry in lymph node specimens with normal histology (NLN) and involved by FL and CHL. We report that both CD4 positive T-cells and Treg subset show distinct phenotypes in different disease entities suggesting different biological functions. Single cell suspensions were prepared from NLN (n=10) and lymph node biopsies involved by FL (n=10) and CHL (n=10), and high dimensional multiparameter flow cytometric immunophenotyping was performed using antibodies against immune checkpoints (TIGIT, TIM3, PD-1, CD96, LAG3, CTLA4, CD73). To characterize the CD4 T-cell compartments we used a dimensionality reduction algorithm for non-linear data representations (tSNE). We studied the CD4+FoxP3-CD25- and Treg characterized by CD4+FoxP3+CD25+ phenotype separately and in both the compartments we identified and characterized subpopulations specific for each of the disease cohorts. tSNE representations CD4 positive T-cells and Treg showed different distributions in NLN, FL and HL. In NLN, CD4 cells broader heterogeneity without distinct clusters whereas in FL and CHL CD4 positive T-cells and Treg (Figure 2 A-B) showed highly polarized phenotypes which were distinct from each other and nearly absent within normal Treg compartment. We observed a strong expression of the immune checkpoint regulators TIM3, LAG3, CTL4, Tbet and PD1 in CD4 T-cells derived from HL tissues. In contrast FL CD4 T-cells were mainly characterized by an up regulation of PD1, CTLA4 and TIGIT. The TIGIT+ cells in FL samples are mainly CXCR5+PD1bright and they up regulate CTLA-4 in the FoxP3+ compartment. In all the neoplastic tissues the FoxP3+CD25+ T-Reg express mainly an activated/memory phenotype (CD45RO+CTLA4+), but while in HL microenvironment they show a TH1 phenotype (CXCR3+Tbet+), in FL they mainly express PD1+CXCR5+ (Figure 1B). Additionally, the dominant population of regulatory T-cells derived from HL samples down modulate PD1 expression, show high level of expression of TH1-associated transcription factor Tbet and have high proliferation index, while in FL, PD1 is brightly expressed, Tbet is not expressed and proliferation index is low in the dominant population (Figure 1A). The distinct phenotypic differences of Treg in FL lymphoma and CHL may account for the better prognosis seen in CHL with increased Treg which has TH1 like phenotype, therefore predicted to have anti-tumor activity. The differences seen in the expression immune checkpoint regulators both on CD4 positive T-cells and Treg subset may explain different rate responses seen in FL compared to CHL with checkpoint therapy. Disclosures Roshal: Physicians' Education Resource: Other: Provision of services; Celgene: Other: Provision of Services; Auron Therapeutics: Equity Ownership, Other: Provision of services. Dogan:Corvus Pharmaceuticals: Consultancy; Novartis: Consultancy; Takeda: Consultancy; Roche: Consultancy, Research Funding; Celgene: Consultancy; Seattle Genetics: Consultancy.

The feline AIDS model for HIV-1 treatment failed in the 1990s, due to structural features resembling protease inhibitor (PI) resistant HIV-1 variants. Widespread drug-resistance to PIs now invokes the possibility of rescuing feline immunodeficiency virus (FIV) as a model for PI treatment. We here analyzed susceptibility of FIV to second generation PIs, lopinavir, atazanavir, and the structurally unrelated non-peptidic PI tipranavir. We found that FIV protease resembles HIV-1 protease drug resistance mutations limiting binding of lopinavir and atazanavir but not tipranavir. All three PIs were found to inhibit FIV replication in a concentration-dependent manner, but only tipranavir inhibited FIV similarly to HIV-1. This drug inhibited FIV synergistically with ritonavir. Inhibition of protease activity was confirmed by Western blot analysis. In molecular docking simulations, tipranavir displayed energetically favorable interactions with the catalytic cavity of the mature dimeric FIV protease. The calculated hydrogen bond network was similar to that found in HIV-1 protease/tipranavir complexes and involved atoms in the protein backbone. We also modeled the interaction of tipranavir with an immature protease monomer, suggesting that inhibition of protease dimerization may be a secondary modality for FIV inhibition by tipranavir. In conclusion, tipranavir is the first FDA-approved non-reverse transcriptase inhibitor of HIV-1 to show anti-FIV properties. The tipranavir response by FIV may 1) support the idea of using FIV as a small animal model for PI-resistant HIV-1, thus expanding access to animal AIDS models; and 2) pave the way for development of novel broad-based inhibitors for treatment of drug resistant HIV-1.

Human T cells that express a T cell antigen receptor (TCR) containing γ-chain variable region 9 and δ-chain variable region 2 (Vγ9Vδ2) recognize phosphorylated prenyl metabolites as antigens in the presence of antigen-presenting cells but independently of major histocompatibility complex (MHC), the MHC class I-related molecule MR1 and antigen-presenting CD1 molecules. Here we used genetic approaches to identify the molecule that binds and presents phosphorylated antigens. We found that the butyrophilin BTN3A1 bound phosphorylated antigens with low affinity, at a stoichiometry of 1:1, and stimulated mouse T cells with transgenic expression of a human Vγ9Vδ2 TCR. The structures of the BTN3A1 distal domain in complex with host- or microbe-derived phosphorylated antigens had an immunoglobulin-like fold in which the antigens bound in a shallow pocket. Soluble Vγ9Vδ2 TCR interacted specifically with BTN3A1-antigen complexes. Accordingly, BTN3A1 represents an antigen-presenting molecule required for the activation of Vγ9Vδ2 T cells.

Antigen-specific γδ T cells represent an early innate defense known to play an important role in anti-mycobacterial immunity. We have investigated the immune functions of Vγ9Vδ2 T cells from Broncho-Alveolar lavages (BAC) samples of active TB patients. We observed that BAC Vγ9Vδ2 T cells presented a strong down-modulation of CD3 expression compared with Vγ9Vδ2 T cells from peripheral blood. Furthermore, Vγ9Vδ2 T cells mainly showed a central memory phenotype, expressed high levels of NK inhibitory receptors and TEMRA cells showed low expression of CD16 compared to circulating Vγ9Vδ2 T cells. Interestingly, the ability of BAC Vγ9Vδ2 T cells to respond to antigen stimulation was dramatically reduced, differently from blood counterpart. These observations indicate that γδ T cell functions are specifically impaired in situ by active TB, suggesting that the alveolar ambient during tuberculosis may affect resident γδ T cells in comparison to circulating cells. © 2013 Elsevier Inc.

Protective immunity against mycobacterial infections such asMycobacterium tuberculosisis mediated by interactions between specific T cells and activated antigen presenting cells. To date, many aspects of mycobacterial immunity have shown that innate cells could be the key elements that substantially may influence the subsequent adaptive host response. During the early phases of infection, innate lymphocyte subsets play a pivotal role in this context. Here we summarize the findings of recent investigations onγδT lymphocytes and their role in tuberculosis immunity.

12 páginas -- PAGS nros. 141-152, Objective: Cell infection by HIV-1 is inhibited by both the expression of CD38 and a soluble peptide (sCD38p) corresponding to its extracellular membrane-proximal amino acid sequence (amino acids 51 - 74). We show here the effects of PEG conjugation to sCD38p and provide new insights into the mechanisms behind the anti-HIV-1 effects of CD38 and derived peptides. Research design/methods: In-vitro and in-silico study. Results: PEGylation of sCD38p increased its ability to inhibit replication of HIV-1 in MT-4 cells and syncytia formation in cocultures of MT-2 and persistently HIV-1IIIB-infected H9IIIB cells. In silico modeling suggests that sCD38p and CD4 form stable heterodimers involving, among others, an interaction between lysine 57 (K57) of CD38 and a groove in the CD4 receptor, which, in CD4/gp120 complexes, is partially occupied by a lysine residue of the HIV-1 envelope glycoprotein. K57 substitution with a glycine in sCD38p impaired its ability to inhibit syncytia formation in MT-2/H9IIIB cell cocultures and gp120 binding to CD4 in a mouse T cell line expressing human but not mouse CD4. Conclusions: PEGylation significantly improves the anti-HIV-1 activity of sCD38p, whose effect is probably due to competition with gp120 for a common binding site on CD4 although other mechanisms cannot be excluded so far. The inhibitory concentrations of the sCD38p-PEG as well as its poor toxicity, merit further consideration in anti-HIV-1 strategies

Tuberculosis (TB) is still the principal cause of death caused by a single infectious agent, and the balance between the bacillus and host defense mechanisms reflects the different manifestations of the pathology. The aim of this work was to study the role of myeloid-derived suppressor cells (MDSCs) during active pulmonary tuberculosis at the site of infection. We observed an expansion of MDSCs in the lung and blood of patients with active TB, which are correlated with an enhanced amount of nitric oxide in the plasma. We also found that these cells have the remarkable ability to suppress T-cell response, suggesting an important role in the modulation of the immune response against TB. Interestingly, a trend in the diminution of MDSCs was found after an efficacious anti-TB therapy, suggesting that these cells may be used as a potential biomarker for monitoring anti-TB therapy efficacy.

Latently infected, resting memory CD4+ T cells and macrophages represent a major obstacle to the eradication of HIV-1. For this purpose, "shock and kill" strategies have been proposed (activation of HIV-1 followed by stimuli leading to cell death). Histone deacetylase inhibitors (HDACIs) induce HIV-1 activation from quiescence, yet class/isoform-selective HDACIs are needed to specifically target HIV-1 latency. We tested 32 small molecule HDACIs for their ability to induce HIV-1 activation in the ACH-2 and U1 cell line models. In general, potent activators of HIV-1 replication were found among non-class selective and class I-selective HDACIs. However, class I selectivity did not reduce the toxicity of most of the molecules for uninfected cells, which is a major concern for possible HDACI-based therapies. To overcome this problem, complementary strategies using lower HDACI concentrations have been explored. We added to class I HDACIs the glutathione-synthesis inhibitor buthionine sulfoximine (BSO), in an attempt to create an intracellular environment that would facilitate HIV-1 activation. The basis for this strategy was that HIV-1 replication decreases the intracellular levels of reduced glutathione, creating a pro-oxidant environment which in turn stimulates HIV-1 transcription. We found that BSO increased the ability of class I HDACIs to activate HIV-1. This interaction allowed the use of both types of drugs at concentrations that were non-toxic for uninfected cells, whereas the infected cell cultures succumbed more readily to the drug combination. These effects were associated with BSO-induced recruitment of HDACI-insensitive cells into the responding cell population, as shown in Jurkat cell models for HIV-1 quiescence. The results of the present study may contribute to the future design of class I HDACIs for treating HIV-1. Moreover, the combined effects of class I-selective HDACIs and the glutathione synthesis inhibitor BSO suggest the existence of an Achilles' heel that could be manipulated in order to facilitate the "kill" phase of experimental HIV-1 eradication strategies. © 2009 Savarino et al; licensee BioMed Central Ltd.