HIV replication in monocyte-derived macrophages/microglia: Influence of the host cell

HIV currently remains a world-wide epidemic with the need for better drug regimens only to be found through an improved understanding of viral pathogenesis. One of the two main targets of HIV infection, monocyte-derived macrophages (MDM) and microglia (the macrophages of the central nervous system (CNS)), are vital to the establishment and maintenance of infection. Even with current drug cocktail therapies, HIV infection of the CNS continues to be of clinical significance. With that focus, in the first part of this thesis we developed an in vitro model of CNS infection using primary human adult mixed glia cultures under varying conditions of activation, which we believe are reflective of the natural in vivo state of the CNS. Using this model we have described a replication block at the late stages of viral replication in non-activated microglia. Furthermore, examination of P55Gag biochemistry revealed an aberrant processing pattern; such a phenotype has not been reported previously.; Using this model, in the latter part of this thesis, we identify a novel interaction between the viral protein p55Gag and the host protein Annexin 2 (Anx2) in MDM. This cell type-dependent interaction (Anx2 is not expressed in CD4+ T cells) is direct and specific. The functional significance of Anx2 during HIV replication is demonstrated through down-regulation of Anx2 expression by siRNA, associated with a corresponding decrease in viral output. Confocal and electron microscopy experiments further revealed a defect in viral maturation also associated with Anx2 down-regulation. Given the natural location and function of Anx2 as a player in endosomal sorting, among other roles, we propose that Anx2 acts a cellular binding partner involved in directing viral assembly to the endosomal pathway.; This thesis describes the establishment of an in vitro model to study HIV infection of primary MDM and microglia, as well as how this model can be used to identify novel host proteins important for viral replication. The need for new therapeutic targets, especially cellular targets, cannot be underestimated. In addition to the identification of Anx2 presented here, we hope that our model will serve as a framework for future discoveries and clinical developments.