Novel peptide-based HIV-1 immunotherapy

Presence of HIV-1 Nef specific CD4 T cell response is associated with non-progression in HIV-1 infection

The ex vivo response to three HLA-DR-restricted Nef peptides (Nef 66-97, Nef 133-159, Nef 180-202) and one HLA-DQ-restricted Nef peptide (Nef 56-68) was evaluated in 28 HIV-seropositive patients and 6 Long-term Non-Progressors (LTNPs). Analyzing specific proliferative response and IFN-gamma secretion, patients were identified as high responders, medium responders and non-responders to peptides. As high responder patients, LTNP patients showed strong proliferative response to all the Nef-peptides as strong IFN-gamma secretion. Twenty-four months later, all high responder patients were always without antiretroviral treatment whereas 50% of medium responders and at least 66% of low responder patients followed bi-therapy. CDC classification confirmed also unfavourable evolution for these two last groups. All high responder patients conserved stable CD4 counts, proliferative response to Nef peptides as strong IFN-gamma secretion during this 24-month period. So, early good T CD4 response to peptides of the Nef protein could thus be regarded as a factor of good prognosis in HIV infection and a tool of importance in the decision to put or not a patient under treatment.

Immunization with HIV protease peptides linked to syngeneic erythrocytes

New potent vaccine adjuvants are desirable for increasing the efficacy of novel vaccine modalities such as DNA and peptides. We therefore tested if syngeneic erythrocytes could serve as delivery vectors for selected HIV peptides and compared the potency of these constructs to immunization with peptides in phosphate buffered saline or in incomplete Freunds adjuvant. Immunization of mice with peptides in a low dose (5 ng) coupled to erythrocytes induced a weak immune response in mice. These peptides alone (5 microg) gave no immune responses, while formulating the peptides (50 microg) in IFA induced strong homologous immunity as well as prominent cross reactivity to a related mutant epitope. Thus, vaccine delivery using syngeneic erythrocytes, although attractive for clinical use, might be of limited value due to the low amount of antigen that can be loaded per erythrocyte.