The innate immune response induced by type I interferons (IFNs) plays a critical role in the establishment of HIV infection. IFNs are induced early in HIV infection and trigger an antiviral defense program by signaling through the IFNα/β receptor (IFNAR), which consists of two subunits, IFNAR1 and IFNAR2. Changes in IFNAR expression in HIV target cells, as well as other immune cells, could therefore have important consequences for initial HIV spread. It was previously reported that IFNAR2 expression is increased in peripheral blood CD4 + CXCR4 + T cells of HIV + patients compared to HIV uninfected controls, suggesting that HIV infection may alter the IFN responsiveness of target cells. However, the earliest immune cells affected by HIV in vivo reside in the gut-associated lymphoid tissue (GALT). To date, it remains unknown if IFNAR expression is altered in GALT immune cells in the context of HIV infection and exposure to IFNs, including the 12 IFNα subtypes. Here, we analyzed the expression of surface bound and soluble IFNAR2 on Lamina propria mononuclear cells (LPMCs) isolated from the GALT of HIVindividuals and in plasma samples of HIV + patients. IFNAR2 expression varied between different T cells, B cells and natural killer cells, but was not altered following HIV infection. Furthermore, expression of the soluble IFNAR2a isoform was not changed in HIV + patients compared to healthy donors, nor in LPMCs after HIV-1 infection ex vivo. Even though the 12 human IFNα subtypes trigger different biological responses and vary in their affinity to both receptor subunits, stimulation of LPMCs with different recombinant IFNα subtypes did not result in any significant changes in IFNAR2 surface expression. Our data suggests that potential changes in the IFN responsiveness of mucosal immune cells during HIV infection are unlikely dictated by changes in IFNAR2 expression.

Chronic hepatitis B virus (HBV) infection continues to be a major health problem worldwide and remains hard to be cured. Therapy with interferon (IFN) α is an important method for the clinical treatment of chronic hepatitis B. IFNα exhibits direct antiviral effects as well as immunomodulatory activities, which can induce sustained antiviral responses in part of the treated chronic hepatitis B patients. Numerous IFNα subtypes with high sequence identity between 76-96% exist which are characterized by diverse, non-redundant biological activities. Our previous studies have demonstrated that the clinically approved IFNα2 is not the most effective subtype for the anti-HBV treatment among all IFNα subtypes. So far very little is known about the IFNα subtype expression pattern during early HBV infection and the IFNα subtype-specific susceptibility during persistent HBV infection as well as its related cellular mechanism. Here we determined the Ifna subtype mRNA expression during acute and chronic HBV infection by using the well-established hydrodynamic injection (HDI) mouse model and we revealed a transient but strong expression of a panel of Ifna subtypes in the spleen of HBV persistent replication mice compared to HDI controls. Immunotherapy with distinct IFNα subtypes controlled chronic HBV infection. IFNα subtype-mediated antiviral response and immune activation were comprehensively analyzed in an AAV-HBV persistent infection murine model and murine IFNα2 was identified as the most effective subtype in suppression of HBV replication. Further analysis of the immune response revealed a strong immunomodulatory activity of murine IFNα2 on splenic and intrahepatic NK and T cell activation during persistent HBV infection. Taken together, our data provide IFNα subtype-specific differences in the antiviral and immunomodulatory effector responses and a strong expression of all IFNα subtypes in the spleen during persistent HBV infection in mice. This knowledge will support the development of novel immunotherapeutic strategies for chronic hepatitis B infection.

Specific CD8+ T cells are crucial for the control of viruses. However, during many chronic viral infections these cells become dysfunctional. Immune checkpoint receptors, like PD-1 expressed on CD8+ T cells, contribute to this functional suppression during chronic infection. However, during the acute phase of infection virus-specific CD8+ T cells express high levels of PD-1 but are fully competent in killing virus-infected cells and there is increasing evidence that the biological activity of inhibitory receptors is strongly influenced by the availability of their respective ligands. We determined the expression of ligands for inhibitory receptors on infected myeloid cells during the acute phase of Friend retroviral (FV) infection. FV infection of granulocytes, monocytes, and macrophages strongly increased the cell surface expression of PD-L1 and the recently described ligand HVEM for inhibitory receptors BTLA and CD160. In addition, the infection of human myeloid cells in vitro with HIV also enhanced the expression of PD-L1 and HVEM. In infected mice, the upregulation of inhibitory ligands on infected cells was accompanied by enhanced frequencies of FV-specific CD8+ T cells that express PD-1, and the inhibitory receptors CD160 and BTLA. To define the functional effects of HVEM on activated CD8+ T cells, FV-infected mice were treated with blocking antibodies that prevented the interaction of HVEM with its two receptors, CD160 or BTLA, alone or in combination with anti-PD-L1 antibodies. Blocking the interaction of HVEM with CD160 and BTLA improved the production of cytotoxic molecules and the elimination of FV-infected cells. This effect was augmented when the therapy was combined with anti-PD-L1 antibodies, resulting in an additional expansion of cytotoxic CD8+ T cells. Thus, the ligand HVEM for the inhibitory receptors CD160 and BTLA downregulates the functionality of CD8+ T cells during retroviral infection and are potential targets for the immunomodulatory therapy of chronic viral infections.

15 16 The innate immune response induced by type I interferons (IFNs) play a critical role in the 17 establishment of HIV infection. IFNs are induced early in HIV infection and trigger an antiviral 18 defense program by signaling through the IFNa/b receptor (IFNAR), which consists of two 19