Characterization of the different mechanisms of inhibition by cyclic and acyclic defensins on CCR5 and CXCR4 HIV-1 replication

The acquired immune deficiency syndrome (AIDS) is a growing worldwide pandemic. The etiologic agent of AIDS, the human immunodeficiency virus (HIV), has been isolated, and much insight into viral replication and pathogenesis has been gained. Nevertheless, many mysteries remain regarding HIV-1, the pathogenesis of AIDS and the immune response mounted against HIV-1. For example, it is not known why CCR5 tropic HIV-1 (R5 HIV-1) is selected following transmission. Previously our laboratory found that R5 HIV-1 replicates in resting memory T cells (RMTC) while CXCR4 tropic HIV-1 (X4 HIV-1) is unable to replicate in RMTC. We hypothesize that the ability of R5 HIV-1 to selectively replicate in RMTC accounts for its selection following transmission and is related to cellular signaling initiated upon viral binding of the chemokine receptor. We showed that R5, but not X4, HIV-1 activates PYK2. Quantitative real time PCR revealed that RMTC infected with X4 HIV-1 contained less complete cDNA and more 2-LTR circles than RMTC infected with R5 HIV-1. This indicates a possible defect in X4 HIV-1 integration in RMTC. The role of innate immunity in controlling HIV-1 infection is not well known. Small peptides known as defensins, make up part of our innate immune system and affect both X4 and R5 HIV-1 replication. We found that the -- and --defensins tested inhibited viral replication when added both pre- and post-entry, and they directly inactivated R5 and X4 HIV-1. In contrast, the --defensin tested inhibited HIV-1 replication only when present at the time of infection and directly inactivated X4 HIV-1, but not R5 HIV-1. We conclude that --, --, and --defensins inhibit HIV-1 replication by different mechanisms. Defensin and cell signaling studies such as these may lead to novel inhibitors of HIV-1.