The growth kinetics of parental MVA-B and deletion mutant MVA-B A40R were similar (Figure 1D), confirming that this MVA A40 protein is not required for MVA replication. 3.3. of an effector memory phenotype, together with enhanced levels of antibodies against HIV-1 gp120. Reintroduction of the A40R gene into the MVA-B A40R genome (virus termed MVA-B A40R-rev) promoted in infected cells high mRNA and protein A40 levels, with A40 protein localized in the cell membrane. MVA-B A40R-rev significantly reduced mRNA levels of IFN- and of several other innate immune-related genes in infected human macrophages. In immunized mice, MVA-B A40R-rev reduced the magnitude of the HIV-1-specific CD4+ and CD8+ T cell responses compared to MVA-B A40R. These results revealed an immunosuppressive role of the A40 protein, findings relevant for the optimization of poxvirus vectors as vaccines. gene, poxvirus, MVA, HIV vaccine, mice, immune responses 1. Introduction The acquired immune deficiency syndrome (AIDS) pandemic caused by the human immunodeficiency virus (HIV)-1 is spreading worldwide, with high impact and severity in human health. In spite of active antiretroviral therapy (ART), in 2017, an estimated 1.8 million individuals became newly infected with HIV-1 and 940, 000 people died from AIDS-related illnesses worldwide, according to the Joint United Nations Programme on HIV/AIDS. Therefore, the discovery of an effective vaccine against HIV/AIDS that could control the infection and disease progression DW-1350 should be one of the main priorities of the developed world. An effective vaccine against HIV/AIDS should stimulate both humoral and cellular immune responses to multiple HIV-1 viral antigens, including structural and regulatory proteins, and induce strong, broad, polyfunctional, and durable T- and B-cell responses [1]. Although neutralizing antibodies against gp120 are crucial, due to the difficulty in obtaining immunogens capable of inducing high titers of neutralizing antibodies with broad specificities, a focus on HIV-1-specific T-cell immune responses has been one of the main routes pursued in the development of HIV-1 vaccines [2]. For example, in non-human primates, there is a good correlation between vaccine-induced HIV-1-specific cellular immunogenicity and protection after a challenge with a pathogenic simian/human immunodeficiency virus (SHIV) [3,4,5], where CD8+ T cells play an important role in immunity to HIV-1 [5]. Moreover, there is substantial evidence which points out that HIV-1-specific CD4+ and CD8+ T cells mediates protection in vivo [6], and the crucial role played by T cells in HIV-1 suppression comes from studying the immune system in elite controllers, a group of people who are able to control HIV-1 Rabbit polyclonal to ALG1 replication without any ART treatment [7,8]. Of the numerous clinical trials carried out so far with different HIV/AIDS vaccine candidates, only the RV144 phase III clinical trial showed a modest protection of 31.2% against HIV-1 contamination. This clinical trial was based on priming with a recombinant canarypoxvirus ALVAC vector expressing the Env protein from subtypes B/E and Gag/Pro from subtype B, followed by boosting with HIV-1 gp120 protein from subtypes B/E [9]. Thus, improved poxvirus recombinants should be considered as components of an effective HIV/AIDS vaccine. One of the most promising DW-1350 poxvirus vectors is the modified vaccinia virus Ankara (MVA), which has been widely used as a vaccine candidate in preclinical and clinical trials against several prevalent and emerging infectious diseases, including HIV/AIDS, proving to be extremely safe, highly immunogenic, and protective [10,11,12,13,14,15]. Previously, we constructed a recombinant MVA expressing HIV-1 gp120 (engineered to be produced as a cell-released product) and Gag-Pol-Nef (GPN, as an intracellular polyprotein) antigens from clade B (termed MVA-B) [16]. MVA-B has been extensively studied in vitro and in different animal models [4,16,17,18,19,20,21,22,23,24,25]. Furthermore, MVA-B joined in a phase I clinical trial (RISVAC02) in healthy human volunteers, being well tolerated and eliciting moderate HIV-1-specific T-cell and antibody responses, mainly directed against the Env antigen, for almost one year [26,27]. Four years later, only 20% percent of vaccinees maintained low HIV-1-specific T-cell responses, suggesting that MVA-B lacks the capacity to induce long-term HIV-1-specific T-cell memory responses. However, a late MVA-B boost significantly increased the binding and neutralizing antibody responses in most of the vaccinees [28]. Moreover, in chronically HIV-1-infected individuals, vaccination with MVA-B enhanced HIV-1-specific CD4+ T cells but did not have a major impact on the latent reservoir or the DW-1350 rebound of plasma viral load after combined ART interruption [29,30,31,32]. After MVA-B therapeutic vaccination, a balance between activation and regulation of HIV-1-specific CD8+ T cell responses was observed [33], and likewise to inducing HIV-1-particular T-cell reactions in contaminated people chronically, MVA-B impacts monocyte phenotype and their capability to create cytokines [34]..