Detection of Immunoglobulin G1 against rK39 Improves Monitoring of Treatment Outcomes in Visceral Leishmaniasis

Abstract

Background: Visceral leishmaniasis (VL), caused by the Leishmania donovani complex, is a fatal, neglected tropical disease that is targeted for elimination in India, Nepal, and Bangladesh. Improved diagnostic tests are required for early case detection and for monitoring the outcomes of treatments. Previous investigations using Leishmania lysate antigen demonstrated that the immunoglobulin (Ig) G1 response is a potential indicator of a patient's clinical status after chemotherapy. Methods: IgG1 or IgG enzyme-linked immunosorbent assays (ELISAs) with rK39 or lysate antigens and novel IgG1 rK39 rapid diagnostic tests (RDTs) were assessed with Indian VL serum samples from the following clinical groups: paired pre-and postchemotherapy (deemed cured); relapsed; other infectious diseases; and endemic, healthy controls. Results: With paired pre-and post-treatment samples (n = 37 pairs), ELISAs with rK39-and IgG1-specific conjugates gave a far more discriminative decrease in post-treatment antibody responses when compared to IgG (P