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Pathogenic human immunodeficiency virus (HIV)/simian immunodeficiency virus (SIV) infection of humans and rhesus macaques (RMs) induces persistently high production of type I interferon (IFN-I), which is thought to contribute to disease progression. To elucidate the specific role of interferon alpha (IFN-α) in SIV pathogenesis, 12 RMs were treated prior to intravenous (i.v.) SIV mac239 infection with a high or a low dose of an antibody (AGS-009) that neutralizes most IFN-α subtypes and were compared with six mock-infused, SIV-infected controls. Plasma viremia was measured postinfection to assess the effect of IFN-α blockade on virus replication, and peripheral blood and lymphoid tissue samples were analyzed by immunophenotypic staining. Consistent with the known antiviral effect of IFN-I, high-dose AGS-009 treatment induced a modest increase in acute-phase viral loads versus controls. Four out of 6 RMs receiving a high dose of AGS-009 also experienced an early decline in CD4 + T cell counts that was associated with progression to AIDS. Interestingly, 50% of the animals treated with AGS-009 (6/12) developed AIDS within 1 year of infection compared with 17% (1/6) of untreated controls. Finally, blockade of IFN-α decreased the levels of activated CD4 + and CD8 + T cells, as well as B cells, as measured by PD-1 and/or Ki67 expression. The lower levels of activated lymphocytes in IFN-α-blockaded animals supports the hypothesis that IFN-α signaling contributes to lymphocyte activation during SIV infection and suggests that this signaling pathway is involved in controlling virus replication during acute infection. The potential anti-inflammatory effect of IFN-α blockade should be explored as a strategy to reduce immune activation in HIV-infected individuals. IMPORTANCE Interferon alpha (IFN-α) is a member of a family of molecules (type I interferons) that prevent or limit virus infections in mammals. However, IFN-α production may contribute to the chronic immune activation that is thought to be the primary cause of immune decline and AIDS in HIV-infected patients. The study presented here attempts to understand the contribution of IFN-α to the natural history and progression of SIV infection of rhesus macaques, the primary nonhuman primate model system for testing hypotheses about HIV infection in humans. Here, we show that blockade of IFN-α action promotes lower chronic immune activation but higher early viral loads, with a trend toward faster disease progression. This study has significant implications for new treatments designed to impact the type I interferon system., (Copyright © 2018 American Society for Microbiology.)

Unlabelled: Human immunodeficiency virus (HIV) persistence in latently infected resting memory CD4+ T-cells is the major barrier to HIV cure. Cellular histone deacetylases (HDACs) are important in maintaining HIV latency and histone deacetylase inhibitors (HDACi) may reverse latency by activating HIV transcription from latently infected CD4+ T-cells. We performed a single arm, open label, proof-of-concept study in which vorinostat, a pan-HDACi, was administered 400 mg orally once daily for 14 days to 20 HIV-infected individuals on suppressive antiretroviral therapy (ART). The primary endpoint was change in cell associated unspliced (CA-US) HIV RNA in total CD4+ T-cells from blood at day 14. The study is registered at ClinicalTrials.gov (NCT01365065). Vorinostat was safe and well tolerated and there were no dose modifications or study drug discontinuations. CA-US HIV RNA in blood increased significantly in 18/20 patients (90%) with a median fold change from baseline to peak value of 7.4 (IQR 3.4, 9.1). CA-US RNA was significantly elevated 8 hours post drug and remained elevated 70 days after last dose. Significant early changes in expression of genes associated with chromatin remodeling and activation of HIV transcription correlated with the magnitude of increased CA-US HIV RNA. There were no statistically significant changes in plasma HIV RNA, concentration of HIV DNA, integrated DNA, inducible virus in CD4+ T-cells or markers of T-cell activation. Vorinostat induced a significant and sustained increase in HIV transcription from latency in the majority of HIV-infected patients. However, additional interventions will be needed to efficiently induce virus production and ultimately eliminate latently infected cells., Trial Registration: ClinicalTrials.gov NCT01365065.

Background: CD4+ T cells are critically important in HIV infection, being both the primary cells infected by HIV and likely playing a direct or indirect role in helping control virus replication. Key areas of interest in HIV vaccine research are mechanisms of viral escape from the immune response. Interestingly, in HIV infection it has been shown that peptide sequence variation can reduce CD4+ T cell responses to the virus, and small changes to peptide sequences can transform agonist peptides into antagonist peptides., Results: We describe, at a molecular level, the consequences of antagonism of HIV p24-specific CD4+ T cells. Antagonist peptide exposure in the presence of agonist peptide caused a global suppression of agonist-induced gene expression and signaling molecule phosphorylation. In addition to down-regulation of factors associated with T cell activation, a smaller subset of genes associated with negative regulation of cell activation was up-regulated, including KFL-2, SOCS-1, and SPDEY9P. Finally, antagonist peptide in the absence of agonist peptide also delivered a negative signal to T cells., Conclusions: Small changes in p24-specific peptides can result in T cell antagonism and reductions of both T cell receptor signaling and activation. These changes are at least in part mediated by a dominant negative signal delivered by antagonist peptide, as evidenced by up-regulation of negative regulatory genes in the presence of agonist plus antagonist stimulation. Antagonism can have dramatic effects on CD4+ T cell function and presents a potential obstacle to HIV vaccine development.

The molecular events involved in the establishment and maintenance of CD4+ central memory and effector memory T cells (TCM and TEM, respectively) are poorly understood. In this study, we demonstrate that ex vivo isolated TCM are more resistant to both spontaneous and Fas-induced apoptosis than TEM and have an increased capacity to proliferate and persist in vitro. Using global gene expression profiling, single cell proteomics, and functional assays, we show that the survival of CD4+ TCM depends, at least in part, on the activation and phosphorylation of signal transducer and activator of transcription 5a (STAT5a) and forkhead box O3a (FOXO3a). TCM showed a significant increase in the levels of phosphorylation of STAT5a compared with TEM in response to both IL-2 (P<0.04) and IL-7 (P<0.002); the latter is well known for its capacity to enhance T cell survival. Moreover, ex vivo TCM express higher levels of the transcriptionally inactive phosphorylated forms of FOXO3a and concomitantly lower levels of the proapoptotic FOXO3a target, Bim. Experiments aimed at blocking FOXO3a phosphorylation confirmed the role of this phosphoprotein in protecting TCM from apoptosis. Our results provide, for the first time in humans, an insight into molecular mechanisms that could be responsible for the longevity and persistence of CD4+ TCM.

Background: Xenotransplantation may provide a solution to the increasing shortage of donor organs. Acute vascular rejection and cell-mediated rejection remain the primary barriers to successful xenotransplantation. In animal models where acute vascular rejection can be attenuated, xenografts succumb to cell-mediated rejection. The mechanisms of acute vascular rejection and cell-mediated rejection are poorly understood., Methods: Using a heterotopic rat-to-mouse cardiac transplantation model, we demonstrate that IL-12p40 attenuates both allogeneic and xenogeneic acute vascular rejection pathology by suppressing B-cell activation and anti-rat isotype switching. To study the mechanism of xenogeneic cell-mediated rejection, we use B-cell deficient mice that only develop cell-mediated rejection pathology. To elucidate the role of IL-12 in cell-mediated rejection, we generated B cell/ IL-12p40 double knockout mice., Results: We demonstrate that xenogeneic cell-mediated rejection is mediated by CD4+ T cells, and is accompanied by elevated FasL and granzyme mRNA expression. Strikingly, by generating B cell/IL-12p40 double knockout mice, we demonstrate that xenogeneic cell-mediated rejection is IL-12p40 dependent. In contrast, we demonstrate that allogeneic cellular rejection is IL-12p40 independent., Conclusions: We conclude that IL-12 plays a dual role in xenotransplantation by driving xenogeneic CD4+ T cell responses but suppressing both allogeneic and xenogeneic B cell responses. Therefore, the mechanism of allogeneic and xenogeneic transplantation rejection is differentially regulated by IL-12.

The mechanism of protection from type 1 diabetes conferred by regulatory T-cells induced by oral insulin treatment of NOD mice is not well understood. We demonstrate that oral insulin feeding of NOD mice induces the function of insulin B-chain reactive CD4+ regulatory T-cells, which compete with diabetogenic effector T-cells for the recognition of insulin in NOD.Scid recipient mice. These effector T-cells become deprived of interleukin (IL)-2 and interferon (IFN)-gamma and are unable to expand and migrate to the pancreas. Type 1 diabetes-protective splenic regulatory T-cells secrete relatively little transforming growth factor (TGF)-beta1, suggesting that TGF-beta may not contribute to the inactivation of effector T-cells in NOD.Scid recipients. The observed preferential infiltration of insulin-reactive regulatory T-cells rather than effector T-cells in the pancreas results in a nondestructive insulitis that correlates with an increased intrapancreatic expression of macrophage inflammatory protein-1beta. Thus, oral insulin therapy overcomes a deficiency in regulatory T-cells and protects against type 1 diabetes by inducing insulin B-chain reactive regulatory T-cells to block cytokine secretion and migration of diabetogenic effector T-cells to the pancreas. Our data emphasize that continuous oral insulin feeding over a prolonged period is required to prevent type 1 diabetes.

We have previously demonstrated that the growth of weakly immunogenic murine sarcomas leads to the induction of immunologically specific pre-effector cells in tumor-draining lymph nodes (TDLN). The in vitro activation of TDLN cells with anti-CD3 monoclonal antibodies (mAbs) and interleukin-2 (IL-2) resulted in the acquisition of effector function as measured by tumor regression in the adoptive immunotherapy of pulmonary metastases. Further studies were performed to characterize the mechanisms associated with in vivo tumor reactivity mediated by activated TDLN cells. By positive selection, CD4+ and CD8+ T cells were purified and activated by the anti-CD3/IL-2 method. CD8+, but not CD4+, cells manifested tumor-specific granulocyte-macrophage colony-stimulating factor (GM-CSF) and interferon-gamma (IFN-gamma) release in vitro, and elicited tumor regression in vivo. By contrast, only activated CD4+ were found to release significant amounts of IL-2 in response to tumor antigen but did not mediate tumor regression in vivo. Mixing the two purified populations enhanced the antitumor activity of the CD8+ T cells. In culture, IL-2 was found to augment the relative amount of tumor-specific release of GM-CSF and IFN-gamma by activated TDLN cells. We found that the tumor-specific release of GM-CSF and IFN-gamma by activated lymphocytes was strongly associated with the in vivo therapeutic efficacy of these cells. Evidence in support of this included the following: (1) cytokine release of TDLN derived after different durations of tumor growth correlated with tumor reactivity in adoptive transfer studies, (2) cytokine release of T cells derived from different lymphoid organs corresponded with tumor reactivity in adoptive transfer, and (3) in vivo administration of neutralizing mAb to IFN-gamma and GM-CSF significantly inhibited the antitumor reactivity of TDLN cells. These studies document the contributory roles of IFN-gamma, GM-CSF, and IL-2 released by activated CD4+ and CD8+ T cells involved in tumor regression.

We have previously reported that the poorly immunogenic D5 melanoma transduced to secrete granulocyte-macrophage colony-stimulating factor (GM-CSF) will elicit immunity in tumor-draining lymph node (TDLN) cells after subcutaneous inoculation. After in vitro activation with anti-CD3 and interleukin-2 (IL-2), these cells acquire in vivo antitumor reactivity to wild-type tumor in the adoptive immunotherapy of pulmonary metastases. Using monoclonal antibodies, depletion of CD4+ or CD8+ T cells immediately after the adoptive transfer of activated TDLN cells revealed that both subsets could mediate the regression of tumor in the absence of exogenous IL-2 administration. CD8+ cells were more potent than CD4+ cells in mediating tumor regression on a per cell basis. We found that the exogenous administration of IL-2 enhanced the antitumor efficacy of CD4+ T cells. Purified CD4+ and CD8+ TDLN cells that were activated separately in culture released GM-CSF and interferon-gamma in response to wild-type tumor in vitro and mediated tumor regression in vivo. Last, the induction of either immune CD4+ or CD8+ T-cell subset during growth of the GM-CSF-secreting melanoma was found to be unaffected by the depletion of the alternate T-cell subset before tumor inoculation. These findings demonstrate that both CD4+ and CD8+ T cells can independently acquire therapeutic reactivity and presumably recognize two separate epitopes involved in tumor rejection.