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HIV-1 Glycoprotein 120-Specific Exosome-Targeted CD8+ T Cell Vaccine



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Immunosuppression is a hallmark of human immunodeficiency virus-1 (HIV-1) infection. Upon binding to cluster of differentiation (CD) 4 receptor via trimeric glycoprotein (Gp) 120, HIV-1 enters and multiplies in CD4+ T cells, leading to the death of these cells. CD4+ T helper (Th) cells are required for the generation and maintenance of CD8+ T cells, which are crucial to control HIV-1 proliferation. The stimulation of HIV-1-specific CD8+ T cell responses in CD4-deficient environment is a major scientific challenge. In addition, dendritic cells (DCs) expressing C-type lectin and dendritic cell-specific intercellular adhesion molecule-3-grabbing non-integrin (DC-SIGN) with high affinity for Gp120, appear to act as “Trojan horses”, facilitating the spread of HIV-1 from mucosal surfaces to T cells in lymph nodes, and these HIV-1-infected T cells have been found to be impaired. Currently, highly active antiretroviral therapy (HAART) is the only means to halt progression of acquired immunodeficiency syndrome (AIDS). Although HAART suppresses viral replication and significantly improves prognosis, toxicity and cost of the treatment have become major limitations for its use. In addition, with long-term use, HAART also decreases HIV-1-specific CD4+ Th1 and CD8+ T cell responses, causing a functional decrease in capacity of HIV-1-capturing DCs in initiating adaptive immune responses. As a result, HIV patients are unable to eliminate infected cells and proviral latent reservoirs. Therefore, how to stimulate efficient CD8+ T cell responses in AIDS patients is one of the major challenges in HIV-1 patient therapy. Previously, it was demonstrated that novel ovalbumin (OVA)-specific exosome (EXO)-targeted CD4+ T cell vaccine (CD4+aTexo) was capable of stimulating CD4+ T cell-independent CD8+ T cell responses and antitumor immunity to a highly metastasizing tumor challenge in wild-type mice. Since CD4+ T cells are killed by HIV-1, the present study proposed to use active CD8+ T cells rather than active CD4+ T cells for vaccine development. First, OVA-specific CD8+aTexo (OVA-aTexo) vaccine was prepared by pulsing concanavalin A (Con A)-stimulated CD8+ T cells with OVA-pulsed DCs (DCOVA)-released exosomes (EXOOVA). In wild-type mice, OVA-aTexo vaccine stimulated CD4-independent OVA-specific CD8+ T cell responses via CD40L and interleukin (IL)-2 signaling, and exosomal peptide major histo-compatibility complex (pMHC)-I targeting. To further provide insight into whether CD8+aTexo vaccine induces similar cellular immune response in the context of human immune system, transgenic A2-Kb mice expressing α1 and α2 domains of human leukocyte antigen (HLA)-A2 and α3 domain of mouse H2-Kb were used. Adenovirus (AdVGp120) expressing HIV-1 envelope protein Gp120 was used to transfect bone-marrow DCs to generate DC expressing Gp120 and DCGp120-released EXO were purified (EXOGp120). EXOGp120 were also purified from the culture supernatant of DC2.4Gp120-transfected cells. Next, Gp120-specific CD8+aTexo (Gp120-aTexo) vaccine was prepared by pulsing ConA-stimulated CD8+ T cells with EXOGp120. In wild-type and A2-Kb mice, Gp120-aTexo vaccine stimulated Gp120-specific effector and memory CD8+ cytotoxic T lymphocyte (CTL) responses, and provided preventive immunity to BL610-Gp120 and BL6-10A2Kb/Gp120 tumor cells, respectively. Gp120-aTexo vaccine also provided therapeutic immunity against 3 and 6-day lung tumor metastasis in transgenic A2-Kb mice. Taken together, these results represent a novel approach to the induction of immunity for the treatment of AIDS patients with CD4+ T cell deficiency or for use in AIDS patients on HAART to clear virus-infected cells.



HIV-1 infection, T cell vaccine, glycoprotein-120, adenovirus, exosomes



Master of Science (M.Sc.)


Graduate Studies and Research


Health Sciences


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