The conserved coreceptor binding site and the 3rd hypervariable loop of HIV

Advances into the understanding of how the human immunodeficiency virus (HIV) attaches to and enters cells has led to a number of new anti-viral drugs that block this process. Although the major steps of HIV entry have been elucidated in detail, a number of important factors that could impact the effectiveness of the entry inhibitors remain to be examined. The first portion of this thesis examines the role of the conserved coreceptor (CoR) binding site in the viral Env protein in entry and entry inhibition. The CoR binding site is important for gp120 binding to CCR5 and CXCR4. I undertook a large functional study to examine the impact of mutations in the CoR binding site on fusion mediated by major and minor coreceptors, coreceptor binding, CoR antagonist and T-20 susceptibility. The results showed that this region is indeed a region involved in CoR utilization, as these highly conserved residues play a part in interacting with both the major and minor CoR\u27s. The second portion of this thesis explores the novel approach of engineering a fully-functional HIV-1 envelope protein (Env), which lacks the protective shielding of the V1, V2, and V3 hypervariable loops. Truncation of the V3 loop of a particular HIV-1 strain, R3A, followed by serial passage, produced an adapted virus with increased infectivity and an adapted Env with improved fusogenicity. Furthermore, the truncation caused a profound and complete resistance to all CoR antagonists tested, while increasing the susceptibility to the fusion inhibitor T-20. Future studies will explore how this adapted Env interacts with its coreceptors, as well as how this modified Env functions as an immunogen