Experimental Infections with Leishmania Aethiopica and Immune Response Analysis of Cercopithecus Aethiops

Background: Leishmania aethiopica (L. aethiopica) is the major cause of cutaneous leishmaniasis in Ethiopia. Only few studies are available on L. aethiopica infection in animal models. Therefore, the purpose of this study is to examine the possibility of establishing an African green monkey model and to describe the immunological consequences of L. aethiopica infection.

Methods: Eight monkeys were inoculated subcutaneously at the tip of the nose with 5 x 106 L. aethiopica promastigotes. Six of them were inoculated with isolates from a patient with localized cutaneous leishmaniasis (LCL) and two were inoculated with isolates from a patient with diffused cutaneous leishmaniasis (DCL). Four control animals received only a sham inoculation of culture medium. Lymphocyte stimulation test was done and IFN-g levels were measured using a sandwich enzyme-linked immunosorbent assay (ELISA).

Result: Three of the six monkeys infected with promastigotes from an LCL patient produced ulceration, one produced nodules that disappeared soon, and the other two lost hair at the infection site. One of the two monkeys infected with promastigotes from a DCL patient produced ulceration while the other lost hair at the infection site. The infection was further confirmed by the isolation of parasites from lesions of the animals. In the in vitro assay, Peripheral Blood Mononuclear Cell (PBMC) obtained from the infected and control animals showed comparable proliferative and IFN-g responses when stimulated with live or dead L. aethiopica parasites and soluble leishmanial antigen.

Conclusion: The development of lesions suggests a possibility of using African green monkeys as a model to establish L. aethiopica infection. The lack of specificity in the proliferative response indicates the need to develop new specific antigens.