During the past two decades of HIV vaccine development, a wide variety of AIDS vaccine strategies have been explored. Among the many tested, DNA and viral vector-based vaccines that activate cellular immune responses have shown some promise despite their limitations. Vaccines based on plasmid DNA are ideal candidates as vaccines due to their safety record in various clinical trials as well as ease of manufacturing, storage and delivery for mass immunization when the need arises. Furthermore, DNA vaccines offer an effective method of delivering multiple immunogens/epitopes representing a single or several pathogens. The efficacy of the DNA vaccines can be enhanced by the addition of adjuvants such as CpG motifs or immunomodulatory cytokines to the vaccine formula. These observations strongly indicate that DNA vaccines delivered with immunostimulatory adjuvants could be the new generation of vaccines for emerging infectious diseases. We developed a novel adjuvant consisting of an empty capsid of an adenoviral vector, termed CAP and used it as an immunological adjuvant to a DNA vaccine. Our preliminary studies indicate that CAP activated splenic APC in vitro and induced pro-inflammatory cytokines including IL-12 both in vivo and in vitro. In addition, coadministration of CAP and plasmid DNA coding for gag antigen, resulted in a dramatic increase in gag-specific CD4 and CD8 T cell proliferation and Th1 cytokine production. These data suggest that CAP can function as an immunomodulatory adjuvant with the ability to enhance immunogen-specific Th1 cytokine production. To test our hypothesis, we propose to further evaluate CAP as an immunological adjuvant to HIV vaccines to promote HIV-specific cellular and humoral responses. We will use two types of immunogens 1) plasmid DNA encoding HIV-1 (NL4-3 Clade B) gag, pol, tat and rev and 2) recombinant gag and tat proteins (rGag and rTat) along with CAP and evaluate its potency in prime-boost protocols.
The specific aims of the grant are to evaluate CAP as an adjuvant to DNA or protein-based HIV vaccines and to determine the effectiveness of prime-boost combinations in naive as well as mice with pre-existing anti-Ad immunity.
The AIDS epidemic is a global emergency and preventive and therapeutic vaccines for AIDS offer the best hope of ending the pandemic. We are evaluating the use of a preparation derived from a product already approved for human use to enhance the potency of HIV vaccines. The initial results which we plan to extend in this study, show the enhancement is not only due to greater immune responses but also a shift of the type of response to one better suited to protect against HIV.
