Alterations in the immune response of golden hamsters during the course of Leishmania donovani infection and after treatment with sodium stibogluconate

The immune response of golden hamsters was monitored following experimental infection with Leishmania donovani and subsequent treatment with sodium stibogluconate (Stibanate Sb^v) taking macrophage migration index (MMI), phagocytic activity of peritoneal macrophages, blastogenic response of splenocytes in presence of phytohaemagglutinin (PHA) and specific antibodies to Leishmania antigen, as parameters. MMI, a correlate of macrophage activation and cellular immune response (CMI) decreased to a value of 0.46 ± 0.09 (in infected hamsters) from the normal control value of 1.0 on day 21 post infection (p.i.). The value remained suppressed during the course of observation up to day 54 p.i. in untreated animals. Following stibanate treatment from day 21 p.i. the MMI started rising and was restored to slightly above the normal value (1.20 ± 0.12) on day 54 p.i. The phagocytic activity of peritoneal macrophages using ¹⁴4c leucine labelled Escherichia coli and blastogenic response of splenocytes to PHA did not alter during the infection or after stibanate treatment. The specific humoral response to promastigote antigen as assessed by enzyme-linked immunosorbent assay (ELISA) revealed the appearance of antileishmanial antibodies on day 14 p.i., which gradually reached a peak titre of 1 :3200 on day 34 p.i. On stibanate treatment the antileishmanial antibodies started declining after day 7 post treatment (p.t.) and reached almost normal level on day 28 p.t. These observations strengthen the claim that hamsters can be used as a useful model for the study of the immune response in human visceral leishmaniasis.