HIV-1 NEF: THERAPEUTIC STRATEGIES AND VIROLOGICAL SYNAPSE-MEDIATED INFECTION

Abstract

HIV-1 infection is one of the greatest public health concerns today. The current HIV/AIDS therapy is effective in halting virus multiplication and has improved the outlook of AIDS; however, high cost, side effects, and the rise of drug-resistant viral strains have posed challenges for long-term treatment and management and mandate development of alternative anti-HIV therapies. Despite the fact that a great deal of progress has been made in our understanding of the infection over the last twenty-seven years, there are many unanswered basic scientific questions and no vaccines. In this study, we focused on two aspects related to the HIV-1 protein Nef: one is development of a Nef-based anti-HIV therapeutic strategy; the other is discovery of a novel mechanism that accounts for Nef-enhanced viral infectivity.

We first devised an anti-HIV therapeutic strategy that took advantage of the high virion incorporation of the Nef mutant Nef7 to deliver anti-HIV factors to the virion. We performed a series of proof-of-concept experiments, using the host anti-HIV cellular factor APOBEC3G (A3G). The Nef7.A3G fusion protein retains important properties of Nef7: higher virion incorporation efficiency, lack of PAK2 activation, and reduced CD4 and MHC I downregulation, as well the anti-HIV infectivity function of A3G. Moreover, virus-like particle (VLP)-mediated delivery of Nef7.A3G into infected CD4+ T lymphocytes leads to inhibition of HIV-1 replication in these cells. These results support the use of Nef7 as an anti-HIV therapeutic strategy for the delivery of therapeutic proteins into HIV-1 virions.

HIV-1 Nef protein has long been known to enhance viral infectivity. However, the underlying molecular mechanism remained elusive. Here we show that Nef is important for VS formation and VS-mediated virus transmission from cell to cell, especially in primary cells. Nef accomplishes this by inducing the clustering of VS components CD81 and ZAP70 and by inducing formation of actin protrusions, and these functions involve specific and distinct Nef domains. These findings not only yield new insights into the regulatory function of Nef in viral infectivity, but could also lead to development of more effective anti-HIV therapies that work equally well at blocking both VS-mediated and cell-free virus infection.