Immunological and pathological evaluation of rhesus macaques infected with Leishmania major

Abstract

Cutaneous leishmaniasis, a parasitic infection causing ulcerating skin lesions, is an important disease worldwide and urgently requires a vaccine. Animal models that closely mimic human disease are essential for designing preventive vaccines against Leishmania major. We have evaluated both biologic and immunologic parameters of cutaneous L. major infection in nonhuman primates. Naı̈ve rhesus macaques or monkeys previously exposed to L. major were infected with varying doses of L. major metacyclic promastigotes, and lesion size was assessed over a 10-week period. Monkeys previously infected with L. major had much smaller lesions that resolved faster compared with those of naı̈ve monkeys in response to the two higher doses of infection. Moreover, eight of nine naı̈ve monkeys had parasites detected in their lesions during the course of the infection. In addition, the cellular infiltrate within the lesions was qualitatively and quantitatively different in naı̈ve versus previously infected monkeys. Finally, an ELIspot assay determined that the magnitude and kinetics of responses differed between previously infected and naı̈ve monkeys. Index descriptors and abbreviations: Leishmania major; L. amazonensis; L. brasiliensis; parasitic infection; Th1 cells; cellular immunity; vaccines; CpG ODN, cytosine phosphate guanosine oligodeoxynucleotides; PBMC, peripheral blood mononuclear cells; PVI, perivascular inflammation; DI, dermal inflammation; SLA, soluble Leishmania antigen