Development of in vivo secreted antiviral entry inhibitory peptides for the treatment of HIV-infection
Final Report Abstract
Human immunodeficiency virus (HIV) is the causative agent of acquired immunodeficiency syndrome (AIDS). Antiretroviral therapy (ART) is discussed as the major medical success of the late 20th century as it impacted beneficially on the life expectancy and the quality of life of persons infected with HIV. However, ART has to be taken life-long with all its subsequent side effects. Furthermore, there is a considerable long-term risk of developing drug resistant virus variants. Therefore, novel treatment strategies are required. Here, we focussed on a gene transfer based strategy to prevent viral entry. Specifically, we aimed to improve an in vivo secreted antiviral entry inhibitory peptide (iSAVE) that had been developed previously by one of the applicants (von Laer). As in vivo delivery “tool” we chose for adeno-associated viral (AAV) vectors, which mediate high level transgene expression following transduction of post-mitotic tissues such as liver and muscle. As target organs we decided for the liver for systemic overexpression of iSAVE and for cells of the hematopoietic system for mediating local protection. While for the former a natural occurring serotype is present (AAV8), we aimed to develop an AAV variant through capsid-modification for the latter. A novel iSAVE peptide with reduced immunogenicity was generated and various strategies were applied to improve its secretion efficacy and stability. As expected, intravenous administration of AAV8 vectors resulted in high-level transgene expression and secretion of the transgene product. However, iSAVE in sera was barely detectable presumably due to efficient clearance. By exploiting two different in vivo screening strategies (AAV peptide display and phage display) in humanized mouse models peptides were identified, which mediated enhanced cell entry and efficient nuclear delivery of capsid-modified AAV vectors (AAV targeting vectors) into human peripheral blood lymphocytes (hPBLs). However, a particle-per-cell ratio of 105 had to be applied to obtain reasonable transduction efficiencies (approximately 20%).
