Diagnostic potential of GLP recombinant antigens in whole blood assays for Leishmania infantum infection.

Abstract

Background: The whole blood stimulation assay (WBA) is a valuable tool for detecting asymptomatic Leishmania infection and monitoring the treatment of visceral leishmaniasis (VL). This study sought to identify specific recombinant proteins to replace the nonspecific soluble Leishmania antigen in this assay, which could be useful for developing a standardized diagnostic test that complies with good manufacturing practice. Methods: Employing a cell lymphoproliferative assay, we here assessed the behaviour of 11 recombinant antigens in 61 subjects who had either been successfully treated for or had spontaneously recovered from Leishmania infantum infection. We then selected those antigens showing significant differences in immune cell stimulation indices and cytokine secretion between a responder and non-responder group, respectively, showing a cellular response to L. infantum or not. The three best candidate antigens, ΔCpB, NSC and ENSC, were then used in a WBA conducted on peripheral blood from 53 subjects stratified according to leishmaniasis status [cured VL, cured cutaneous leishmaniasis (CL), asymptomatic leishmaniasis (AS) and healthy controls]. Results: ENSC was found to be the most effective antigen to detect cured VL by measuring specific IP-10 production (90% recognition) and TNF induced by ΔCpB to detect cured CL (71.4% recognition). Although the cytokines IL-2 and IP-10 elicited by NSC and ENSC were able to detect AS, this capacity was only moderate (60%). Conclusions: We propose that, once validated in larger studies, these GLP Leishmania antigens might help improve the accuracy of treatment monitoring and diagnosing cure.