Immunological parameters of visceral leishmaniasis of Leishmania major-infected golden hamsters.

We can consider the Leishmania major-infected hamster as an interesting model of visceral leishmaniasis. Every hamster infected with L. major strain 70 by peritoneal route developed visceral dissemination of the parasite. When immunological parameters were considered, we saw data quite similar to those presented by visceral leishmaniasis patients: negative leishmanin skin test and presence of anti-leishmania antibody. Histopathological analysis showed dissemination of the parasite mainly to liver and spleen. The former organ showed hypertrophy and hyperplasia of Kupffer cells with focal areas of inflammatory infiltration in nodular pattern. The spleen disclosed intense proliferation and enlargement of mononuclear phagocytic cells, sometimes revealing nodular configuration. Anti-leishmania antibodies were easily detected by indirect immunofluorescent technique in this model. Immunomodulation by Cyclophosphamide decreased the anti-leishmania antibody and delayed-type hypersensitivity test results suggested that hamster was able to develop reaction to leishmania antigen, although leishmanin skin test was negative in the L. major-infected animals. We consider the L. major-infected hamster a useful model for visceral leishmaniasis study because of the similarity of immunological reactions to parasite antigen in human disease.