Cellular and Histopathological Changes in BALB/c Mice Infected With Live Attenuated Leishmania major Parasite

Introduction: Cutaneous leishmaniasis is a common form of leishmaniasis caused by infection with the Leishmania major parasite in the world and in Iran. The lack of an effective vaccine and drug resistance prompted this study to investigate the invasive mechanisms caused by the live attenuated strain of L. major parasite in BALB/c mice. Materials & Methods: Leishmania promastigotes which have been attenuated after one, four, nine and twenty passages in a special culture medium were injected into the tail base of ۶-۸w BALB/c mice. The size of the wound was measured, the phagocytosis ability of macrophages in the peritoneal cavity was evaluated by NBT (nitroblue tetrazolium test), the proliferation of splenocytes was measured by the MTT ([۳-(۴,۵-dimethylthiazol-۲-yl)-۲,۵- diphenyl-tetrazoliumbromide] test and histopathologic changes of skin, spleen, lymph nodes and liver were examined at day ۱۵, ۳۰, and ۴۵ after inoculation. Results: The severity of tissue damage to the skin, spleen, and liver was higher at passages ۱, ۴ and ۹ of live attenuated parasite on days ۱۵ and ۳۰ and increased at passage ۱ of parasite on day ۴۵. However, the intensity of the cellular response was lower at passage ۲۰ of attenuated parasite, the size of the wound showed a significant decrease and a relative increase in phagocytosis on day ۳۰ of the infection period; despite the infiltration of mononuclear cells and macrophages in all organs, parasites were only visible in the skin on day ۴۵, and no Leishmania parasites were observed in the lymph nodes, spleen and liver tissue. Conclusion: The results of histopathologic changes, phagocytosis and proliferation of splenocytes showed that as the virulence of the L. major parasite were decreased, the invasive potency of the parasite also decreased, which will be useful as initial findings for the study to develop a live attenuated vaccine.

کلیدواژه ها:

Live attenuated parasite ، Leishmania major ، BALB/c Mice ، histopathological changes ، Phagocytosis