Evaluation of novel therapeutics for HIV prevention and treatment in a humanized mouse model

In the absence of an effective HIV-1 vaccine finding alternative therapeutics and preventative methods has become essential. In this regard preventative approaches such as pre-exposure chemo-prophylaxis that employ either topical applied microbicides or systemically administered anti-retroviral drugs show great promise. In these studies, we evaluated two new classes of clinically approved drugs with different modes of action namely, an integrase inhibitor raltegravir and a CCR5 inhibitor maraviroc as potential systemically and topically applied pre-exposure chemo-prophylaxis. Additionally, therapeutic strategies designed to combat HIV/AIDS using siRNAs show considerable promise. However, targeted delivery of these synthetic molecules into infected cells in vivo has been a formidable challenge. In addressing this need we sought to evaluate the efficacy of a chimeric construct consisting of an HIV-1 gp120 specific aptamer with viral neutralization capacity fused to a siRNA with proven efficacy against tat/rev viral transcripts. We also sought to evaluate the efficacy of structurally flexible, cationic PAMAM dendrimers as a siRNA delivery system.;For these novel therapeutic strategies to succeed it is important to evaluate them in both in vitro and in vivo. The rhesus macaque has been a valuable research tool for comparative HIV-1 studies. However, aspects of this model render its usefulness limited considering its expensive nature and not utilizing HIV-1 itself. In this regard the recently developed humanized mouse model that permits multi-lineage human hematopoiesis is an excellent alternative to the non human primate model. To generate humanized mice, neonatal Rag2-/-gammac-/- or Rag1 -/-gammac-/- mice were xenografted with human CD34+ hematopoietic stem cells, resulting in a model that can permit HIV-1 infection. Upon infection by HIV-1 chronic viremia develops with a subsequent loss of CD4 T cells. These mice also successfully mimic the predominant mode of HIV-1 transmission via the sexual vaginal route which also results in chronic viremia and helper T cell loss. Thus this small animal model permits the rapid preclinical evaluation of potential candidates for pre-exposure prophylactic (PrEP) efficacy as well as novel RNA-based therapeutics.;Here we utilize these humanized mouse models to evaluate the PrEP efficacies of the drugs named above as well as the in vivo efficacy of siRNAs delivered by utilizing a chimeric aptamer construct or a PAMAM dendrimer. Our results showed that both of these approaches using either a chimeric aptamer or a PAMAM dendrimer resulted in suppression of viral loads in vivo and most importantly also resulted in protection from T-cell depletion, making these compounds attractive therapeutic candidates for the treatment of HIV-1 infection. Lastly, using the same humanized mouse model we also successfully tested a gene therapy strategy employing lentiviral vectors having RNA-based anti-HIV-1 constructs convey intracellular immunization against HIV-1 in vivo.