Specific antibody responses as indicators of treatment efficacy for visceral leishmaniasis.

Acute visceral leishmaniasis (VL) is caused by infection with parasites of the Leishmania donovani complex and may be fatal if not treated. Early diagnosis and efficacious treatment are the keys to effective VL management and control. Novel regimens are being developed to overcome limitations in VL treatment options, which are currently restricted by high costs, severe systemic side effects, and unresponsiveness. Although simple and accurate serological tests are available to help confirm VL, none are suitable to monitor treatment efficacy and cure. Here, we confirm that serum antibody responses to the diagnostic antigens rK39 and rK28 are unaltered by treatment, but demonstrate that antibodies produced against two antigens, rK26 and rK18, can be used as an indirect measure of parasite clearance. The levels of anti-rK18 and -rK26 antibodies were high in patients at initial diagnosis but declined in patients treated with either SSG (Ethiopia) or AmBisome (Bangladesh). Taken together, we propose that serological tests which measure antibodies to rK26 and rK18 merit consideration as potential markers of treatment success and cure.