1001. Knockdown of CXCR4 Expression Sufficient for Blocking HIV-1-Infection Requires Combinatorial Intrabody and siRNA Mediated HIV-1 Vector Gene Delivery

Abstract

A number of chemokine receptors have been shown to facilitate HIV-1 entry in tissue culture, however, only CCR5 and CXCR4 have been convincingly demonstrated to be the relevant chemokine co-receptors. Mechanisms based on targeting CCR5 or CXCR4 to prevent viral entry may prove to be beneficial for cellular protection against HIV-1 infection and provide a clinical benefit. In contrast to CCR5, targeting CXCR4 by conventional siRNA or intrabody gene delivery has proven insufficient to promote adequate protection. To develop vectors that protect CD4 T-cells from X4 tropic infection, a SIN HIV-1 vector containing CXCR4 siRNA and intrabody genes in combination has been generated, termed the CGW-siX4/X4i vector. When transduced into primary CD4 T-cells, CXCR4 cell surface expression decreased 7-fold as determined by mean fluorescence intensity (MFI), compared to the vectors containing only intrabody, 2-fold or siRNA, 2-fold. These results confirm expression of the intrabody and siRNA genes from the same vector provides additive effects for CXCR4 knockdown.