The use of peptides for studying molecular events in HIV- and HSV-infections

Synthetic peptides were used as tools in order to study various characteristic sof human immunodeficiency virus (HIV) and herpes simplex virus (HSV). Peptides were designed as multiple antigenic peptides (MAPs) and used as HIV vaccines in experimental animals. The included HIV epitopes were more immunogenic when immunized as MAPs than as a protein. This was probably due to the fork-like MAP structure which gave an effective multimeric epitope delivery to the immune cells. The anti-peptide antibodies also bound to the protein and showed biological activity.

An accurate antibody population profile is crucial in order to evaluate different vaccine candidates. Specific antibody populations in HIV envelope protein gpl60-vaccinated animals, HIV infected patients or untreated infected patients from Sweden and Argentina, were analyzed. A broad vaccine-induced antibody production in immunized animals anda slight expansion of the existing immunity in vaccinated HIV-infected humans. A new immunodominant region of the HIV envelope was identified, against which the majority of HIV seropositive Swedish and Argentinian patients showed reactivity. By using peptides the HIV-specific antibody pool could be mapped in detail which was not possible by using the entire gpl60 protein. A comparison of different adjuvants revealed that the muramyl dipeptide (MDP) and proteosome adjuvants were potent enhancers of immunity against the HIV envelope protein gpl60. A mini antibody was designed, corresponding to a complementarity determining region (CDR) in the antigen-binding domain of an HIV-specific antibody with neutralizing capacity. The CDR peptide competed with the whole antibody for its epitope, located in the third variable loop (V3) of the HIV envelope protein gpl20. The mini antibody also showed broad neutralization of both laboratory-adapted virus and primary isolates. This CDR peptide appeared to cross cellular membranes and may be capable of inactivating viral envelopes intracellularly. It might be used to treat HIV-infected individuals and should induce less side effects and spread more effeciently than whole antibodies.

The interaction between the HIV envelope protein gpl20 and its cellular co-receptor CCR5 was analyzed. CCR5 mediates a which is a post-binding interaction necessary for cellular fusion. Strong binding of gpl20 was seen against peptides representing the N-terminal and first extracellular loop regions in CCR5. In addition, the N-terminal CCR5 domain peptide bound strongly to the V3 loop of gpl20, which is the major neutralization determinant of HIV. Both the N-terminal CCR5 peptide and peptide-induced rabbit immune sera showed specific inhibition of viral replication. This indicates a possibility to treat HIV-infected patients with CCR5 peptides that block the post binding fusion step. Discrimination between herpes simplex virus type 1 (HSV-I) and type 2 (HSV-2) infection is important in prevention of virus transmission. Sites of HSV glycoproteins were analyzed for their potency for serodiagnosis of latent HSV infection. Peptides from the glycoproteins G (gG) and D (gD) proteins showed promise as HSV-2 specific and HSV type-common antigens respectively. Interestingly, the most homologous region of HSV-1 / HSV-2 gG was highly discriminating and with sensitivities and specificities similar to native antigens. These peptides may be developed into HSV diagnostic tests.