title: Peptide immunization in humans: a combined CD8+/CD4+ T cell-targeted vaccine restimulates the memory CD4 T cell response but fails to induce cytotoxic T lymphocytes (CTL).
abstract: Immunization with short antigenic peptides represents a potential strategy to induce peptide-specific CTL in vivo. In this study, a synthetic vaccine consisting of an HIV-derived, HLA-A2.1-binding CTL epitope and a tetanus toxin-derived T helper epitope was evaluated for its capacity to induce peptide-specific CTL in humans. Thirteen volunteers were immunized and boosted twice with 100 micrograms of the CTL epitope plus 300 micrograms of the T helper peptide (p30). Peripheral blood mononuclear cells (PBMC) were regularly analysed for cytotoxic and proliferative responses before, between and after the immunizations, and the serum was tested for anti-peptide antibodies. No unequivocal induction of HIV peptide-specific CTL in any of the volunteers was observed. However, a wide pattern of mild and transient side reactions was observed, ranging from local redness at the injection site to generalized exanthema, myalgias, arthralgias and fever. The side-effects were related to the T helper epitope, as they were similar to the side-effects experienced after tetanus immunization, correlated to the magnitude of the p30-specific in vitro proliferative response, and occurred only if p30 was co-injected. No antibodies against the HIV-derived peptides nor against p30 were detectable in the serum after repeated immunizations. The data suggest that the CTL peptide, at the concentration used in this study, failed to induce a cytotoxic immune response in vivo, although the T helper peptide seems to be capable of restimulating the specific memory T cells.
authors.affiliation: Institute of Immunology and Allergology, Inselspital, Bern, Switzerland.
authors.forename: C
authors.initials: C
authors.lastname: Brander
authors.forename: G
authors.initials: G
authors.lastname: Corradin
authors.forename: T
authors.initials: T
authors.lastname: Hasler
authors.forename: W J
authors.initials: WJ
authors.lastname: Pichler
mesh_terms: D000818:Animals; D015704:CD4 Antigens / Q000276:immunology*; D018984:Epitopes, T-Lymphocyte / Q000276:immunology*; D005260:Female; D015789:HLA-A2 Antigen / Q000276:immunology*; D007114:Immunization / Q000662:veterinary*; D008213:Lymphocyte Activation; D008252:Macaca fascicularis / Q000276:immunology*; D008297:Male; D010446:Peptide Fragments; D018449:SAIDS Vaccines / Q000276:immunology*; D015302:Simian Immunodeficiency Virus / Q000276:immunology*; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology* / Q000821:virology; D013744:Tetanus Toxin / Q000276:immunology
chemical_list: D015704:CD4 Antigens; D018984:Epitopes, T-Lymphocyte; D015789:HLA-A2 Antigen; D010446:Peptide Fragments; D018449:SAIDS Vaccines; D013744:Tetanus Toxin