Murine T Cell-Dependent Response Affects Leishmania amazonensis Amastigote Survival and Virulence.

Our group has previously described the infection course of Leishmania amazonensis in BALB/c and BALB/cnu/nu mice, which have distinct T-cell dependent responses. In this study, lesion-derived amastigotes exhibited differential protein expression in a host-dependent manner. Herein, we evaluate the impact of the immune system of these two mouse strains on parasite survival and virulence. For this, BALB/c and BALB/cnu/nu mice were infected with promastigotes of the LV79 strain, and after 13-weeks of infection, amastigotes were isolated from the lesion footpads. The amastigotes recovered from BALB/c mice were more viable, generating cultures with a higher number of promastigotes than those from BALB/c nude mice. Accordingly, lesion-derived amastigotes from BALB/c mice displayed higher infectivity, induced larger parasitophorous vacuoles in vitro, and exhibited greater virulence in vivo than those from BALB/cnu/nu mice. These findings demonstrate that the mouse immune environment can shape the biological phenotype of the parasite, directly impacting its survival and virulence.