Preparation of a K39sub Recombinant Antigen for the Detection of Leishmania infantum Antibodies in Human: a Comparative Study with an Immunochromatographic Test and Direct Agglu-tina¬tion

Background: The Mediterranean type of kala-azar is occurred in different parts of Iran and caused by Leishmania infan¬tum. A rapid and valid test for early detection of visceral leishmaniasis in human would be highly desirable because it could de¬crease mortality rate of the disease. In this study, we aimed to compare the results of K39sub antigen with an commercial immu¬nochromatographic dipstick rk39 test (Cypress Diagnostic Company, Belgium) for early detection of L. infantum infec¬tion in human. Methods: K39sub recombinant antigen of L. infantum LON49 was expressed in prokaryotic system and evaluated for the diagno¬sis of human visceral leishmaniasis. This study evaluated the performance of recombinant K39sub antigen by ELISA and an commercial immunochromatographic dipstick rk39 test for the detection of L. infantum antibodies in 43 clinically in¬fected patients with direct agglutination test (DAT) at a 1: 3200 cut off titer and higher. Controls included 69 healthy volun¬teers and 28 patients with other diseases including malaria (n=5), tuberculosis (n= 3), toxoplasmosis (n= 4), cystic hydatido¬sis (n= 5) and cutaneous leishmaniasis (n= 11). Results: The sensitivity of the K39sub antigen and an immunochromatographic dipstick rk39 test was 90.7%, and 97.7%, respec¬tively, while the specificity was 95.6% and 97.9%, correspondingly. A good concordance was found between k39sub anti¬gen and commercial dipstick rk39 strips (k= 96.4%). Conclusion: The accuracy of the K39sub antigen in the detection of L. infantum antibodies in human infecetion is confirmed