Evaluation of the stability and immunogenicity of autoclaved and nonautoclaved preparations of a vaccine against American tegumentary leishmaniasis

This study was designed to evaluate the immunogenicity of autoclaved and no nautoclaved preparations of a vaccine composed of whole antigens from kille d promastigotes of Leishmania amazonensis. Leishmanin skin-test (LST)-negat ive volunteers were immunized with either autoclaved or nonautoclaved vacci ne preparations (32 and 36 subjects, respectively) that had been maintained at 4 degrees C for one year before the onset of this trial. Immunological tests were performed two days before and 40 days after vaccination. The LST conversion rates induced by the autoclaved and nonautoclaved vaccines were significantly different: 59% and 83%, respectively. Leishmania antigen-sti mulated proliferative responses of peripheral blood mononuclear cells (PBMC ) were significantly higher after vaccination than before vaccination in bo th groups. The CD8(+) subset was predominant over the CD4(+) subset among t he leishmania-reactive cells after vaccination in both groups. The producti on of IFN-gamma by the leishmania antigen-stimulated PBMC was significantly higher after vaccination than before vaccination in the group receiving th e nonautoclaved Vaccine but not in the autoclaved vaccine group. IL-2 was f ound both before and after vaccination with no differences between its leve ls in these time points in either group. IL-4 was not detected for either g roup during the study period. (C) 1999 Elsevier Science Ltd. All rights res erved.