Studies on the immunology and serology of leishmaniasis II. Cross-immunity experiments among different forms of American cutaneous leishmaniasis in monkeys

The rhesus monkey (Macaca mulatta) was found to be readily infected with either L. mexicana or L. braziliensis, and cross immunity between the two parasites has been studied in these animals. Monkeys recovered from L. mexicana lesions were completely resistant to re-infection with the same parasite. Monkeys recovered from L. braziliensis infection were immune to further infection with the same strain of parasite. Monkeys recovered from L. mexicana infection were completely resistant to challenge with a strain of L. braziliensis isolated from a patient with espundia, to which they were normally susceptible. On the other hand, monkeys immune to L. braziliensis could be infected with L. mexicana but the resultant infection was milder and short-lived. The question of possible immunization of forest workers against muco-cutaneous leishmaniasis by vaccination with living leptomonads of L. mexicana is discussed. In areas where espundia is a common hazard it might be considered that a prior, self-limiting and single lesion of the chiclero's ulcer type is a preferable alternative.