REINFECTION IN AMERICAN CUTANEOUS LEISHMANIASIS - EVALUATION OF CLINICAL OUTCOMES IN THE HAMSTER MODEL

There is no clear understanding of the outcome of reinfection in New W orld cutaneous leishmaniasis, and its role in the relationship to the development of protection or secondary disease. For this reason, reinf ection experiments with homologous (Leishmania panamensis-L. panamensi s) and heterologous (L. major-L. panamensis) species of leishmaniae we re conducted in the hamster model. The different protocols for primary infections prior to the challenge with L. panamensis were as follows: (a) L. major, single promastigote injection, (b) L. major, three boos ter infections, (c) L. panamensis, followed by antimonial treatment to achieve subclinical infection, (d) L. panamensis, with active lesions , (e) sham infected, naive controls. Although all reinfected hamsters developed lesions upon challenge, animals with active primary lesions due to L. panamensis, and receiving booster infections of L. major had the most benign secondary lesions (58-91% and 69-76% smaller than con trols, respectively, P<0.05). Subclinically infected animals had inter mediate lesions (40-64% smaller than controls, P<0.05), while hamsters which received a single dose of L. major had no significant improveme nt over controls. Our results suggested that L. major could elicit a c ross protective response to L. panamensis, and that the presence and n umber of amastigotes persisting after a primary infection may influenc e the clinical outcome of reinfections.