Treatment of AIDS has been greatly aided by the development of anti-HIV-1 drugs such as inhibitors of the HIV-1 reverse transcriptase and protease. However, combinatorial treatment utilizing these drugs comes with high cost, toxic side effects, viral persistence as well as development of drug-resistant mutants. A safe and effective vaccine would be the ultimate tool for prevention and elimination of AIDS epidemic. Progress in developing a vaccine against HIV-1 viral components has encountered great difficulties because the virus is capable to elude the protective immunity due to its high mutation rate. An alternative vaccine strategy is to target those cellular components involved in HIV-1 infection. The HIV-1 co-receptors, especially CCR5, are particularly attractive for the vaccine purpose due to their central roles in HIV-1 entry. The goal of this research application is to test the concept that using a human IgG1 molecule as scaffold, antigen presentation and processing of the extracellular domains of human CCR5 could be greatly enhanced, resulting a marked increase in immunogenicity of CCR5. In this pilot study, efforts will be made to design and identify optimal forms of CCR5-IgG molecules as effective immunogens for induction of anti-CCR5 humoral immune responses capable of inhibiting a broad range of R5-tropic HIV-1 infection. Extensive studies have indicated that both the N-terminus (Nt) and the second extracellular loop (ECL2) of CCR5 are critical for its HIV-1 co-receptor activity. As prototype immunogens, different CCR5 Nt- or ECL2-1gG fusion proteins will be constructed to specifically conserve their native conformation and/or post-translational modification. Upon in vitro confirmation of the desired structural features and biological activities, the CCR5- IgG fusion molecules will be used to genetically immunize mice for evaluation of their potential to elicit immune responses to CCR5. As CCR5 is a self-antigen, different prime-boost DNA vaccination protocols will be tested for maximizing induction of neutralizing antibodies able to block R5 HIV-1 virus entry. Strategies include use of biological adjuvants to selectively regulate T cell responses. B-cell/T-cell epitopes of CCR5 identified in this study will shed a new light on future vaccine designs. Data generated herein will provide valuable information not only for design of an AIDS vaccine but also for general vaccine strategy targeting self-antigen, thus warrants further NIH R01 funding.
