Distinct courses of infection withLeishmania(L.)amazonensisare observed in BALB/c, BALB/c nude and C57BL/6 mice

Abstract

SUMMARYLeishmania(L.)amazonensis[L.(L.)amazonensis] is widely distributed in Brazil and its symptomatic infections usually lead to few localized lesions and sometimes to diffuse cutaneous form, with nodules throughout the body, anergy to parasite antigens and poor therapeutic response. The variability of these manifestations draws attention to the need for studies on the pathophysiology of infection by this species. In this study, we analysed the course and immunological aspects ofL.(L.)amazonensisinfection in BALB/c and C57BL/6 strains, both susceptible, but displaying different clinical courses, and athymic BALB/c nude, to illustrate the role of T cell dependent responses. We analysed footpad thickness and parasite burden byin vivoimaging. Furthermore, we evaluated the cellular profile and cytokine production in lymph nodes and the inflammatory infiltrates of lesions. Nude mice showed delayed lesion development and less inflammatory cells in lesions, but higher parasite burden than BALB/c and C57BL/6. BALB/c and C57BL/6 mice had similar parasite burdens, lesion sizes and infiltrates until 6 weeks after infection, and after that C57BL/6 mice controlled the infection. Small differences in parasite numbers were observed in C57BL/6 macrophagesin vitro, indicating thatin vivomilieu accounts for most differences in infection. We believe our results shed light on the role of host immune system in the course ofL.(L.)amazonensisinfection by comparing three mouse strains that differ in parasitaemia and inflammatory cells.