Visceral leishmaniasis: resistance to reinfection in the liver following chemotherapy in the BALB/c mouse.

The ability of BALB/c mice to resist reinfection with Leishmania donovani following chemotherapy was studied. BALB/c mice, infected with L. donovani, were treated on Days 7 and 8 postinfection with free, niosomal, or liposomal sodium stibogluconate. It was found that all three drug treatments caused a dramatic reduction in liver parasite burdens as measured on Days 6 and 29 post-treatment. On Day 6 postdrug treatment infection with L. donovani amastigotes, of mice from infected, drug-treated groups, along with age- and sex-matched uninfected controls, showed that at 23 days later, significantly fewer parasites were recovered from the livers of reinfected animals compared with controls given their first infection. Treatment of mice with sodium stibogluconate 6 days prior to a primary infection significantly reduced the number of parasites recovered 14 days later, especially using the carrier form of the drug. In vivo macrophage activity in the liver, as measured by the uptake of radiolabeled horseradish peroxidase immune complex, was significantly raised following stibogluconate treatment of infected but not uninfected mice. These results suggest that a state of resistance persists in the liver of infected mice following chemotherapy which may in part be due to local macrophage activation but also to an unsuspected persistance of the drug.