Vaccination of the African White-Tailed Rat, Mystromys Albacaudatus, with Sonicated Leishmania Braziliensis Panamensis Promastigotes *

Abstract

The usefulness of sonicated Leishmania braziliensis panamensis promastigotes for vaccination was evaluated in Mystromys albacaudatus, the African white-tailed rat. Thirty-two animals received three intradermal injections of 2 × 106 sonicated promastigotes derived from L. braziliensis panamensis at weekly intervals. One month after completion of the immunization schedule, the experimental group of animals was challenged in vivo with 2 × 106 live L. braziliensis panamensis promastogotes. At the same time, a matched group of 40 control animals was similarly challenged. Within 2 months, 35 of the 40 animals (87.5%) the control group developed ulcers, while only 14 of 32 previously vaccinated animals (43.7%) developed ulcers at the site of challenge within this same time period. The remaining 18 vaccinated animals (56.2%) remain free from ulcers 7 months after challenge. When lymphoctes from the spleens of vaccinated and control animals were challenged in vitro with antigen derived from sonicates of varing numbers of promastigotes, only cells from immunized animals responded vigorously to the antigenic challenge, a response which was not enhanced by the addition of immune antiserum to the reaction.