Study of the HIV-1-mediated induction of BAFF in primary human monocytes and monocyte-derived macrophages

Authors: Gomez, Alejandro Martin
Advisor: Tremblay, Michel J.
Abstract: HIV-1 (Human Immunodeficiency Virus I) infection is characterized by persistent viral replication, chronic immune activation, CD4+ T cell depletion and several immune dysfunctions that are observed even in cells that are not targeted by the virus such as B lymphocytes. Some B-cell abnormalities observed in HIV-1-infected individuals include hypergammaglobulinemia, nonspecific B-cell activation, class switching, increased cell turnover, breakage of tolerance as well as a loss of the capacity to generate and maintain memory, among others. Several cytokines and growth factors that are increased in the serum of HIV-1-infected individuals have been suggested to directly and/or indirectly trigger B-cell activation, and one of these is the B-cell-activating factor (BAFF). BAFF is an essential component of B-cell homeostasis but excess production results in B-cell hyperplasia, lymphoproliferation, hypergammaglobulinemia, and symptoms of autoimmunity. The mechanisms of BAFF upregulation in the context of HIV-1 infection are not fully understood and no previous studies have addressed the ability of fully competent HIV-1 to induce BAFF production by myeloid cells. The different studies presented in this thesis converge to the general objective of better characterizing the mechanisms underlying BAFF upregulation by primary human monocytes and monocyte-derived macrophages in the context of HIV-1 infection. We show here that HIV-1 drives BAFF secretion in monocytes by a type-I interferon (IFN)-dependent process. Moreover, we identified plasmacytoid dendritic cells (pDCs) as the cellular source of this type-I IFN-directed modulatory effect in our monocyte cultures, demonstrating that a pDC/monocyte interplay is required for the HIV-1-induced BAFF production. In addition, we provide evidence that HIV-1 upregulates BAFF production in monocyte-derived macrophages and this process relies on productive virus infection, which is itself influenced by the cell phenotype status, and is independent of Toll-like receptors and type-I IFN signal transduction as well as the action of Nef. Altogether, this doctoral project provides new insights for the increased BAFF levels observed during HIV-1 infection. These findings might be relevant for the design of therapies that could help restore the functionality of the B-cell compartment in HIV-1-infected individuals.
Document Type: Thèse de doctorat
Issue Date: 2015
Open Access Date: 23 April 2018
Grantor: Université Laval
Collection:Thèses et mémoires

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