There is no clear understanding of the outcome of reinfection in New
World cutaneous leishmaniasis, and its role in the relationship to the
development of protection or secondary disease. For this reason,
reinfection experiments with homologous (Leishmania panamensis-L.
panamensis) and heterologous (L. major-L. panamensis) species of
leishmaniae were 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 booster 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 controls, respectively, P
{ 0.05). Subclinically infected animals had intermediate lesions (40-64%
smaller than controls, P { 0.05), while hamsters which received a single
dose of L. major had no significant improvement over controls. Our
results suggested that L. major could elicit a cross protective
response to L. panamensis, and that the presence and number of
amastigotes persisting after a primary infection may influence the clinical
outcome of reinfections.
