Compararative evaluation of rK9, rK26 and rK39 antigens in the serodiagnosis of Indian visceral leishmaniasis.

Background: This study was designed for comparative evaluation of two relatively newer recombinant hydrophilic antigens, rK9 and rK26 of Leishmania chagasi along with rK39 (a 39-aminoacid-repetitive immunodominant B-cell epitope of kinesin-related antigen from L. chagasi) and crude soluble antigen (CSA) for the serodiagnosis of Indian visceral leishmaniasis (VL) patients by quantitative ELISA.

Methodology: In the present study a total of 80 subjects comprising of 55 confirmed VL cases and 25 endemic controls (EC) were subjected to ELISA using four different antigens, namely rK9, rK26, rK39 and CSA (derived from Leishmania donovani promastigotes).

Results: Sensitivity was as follows: 78% (95%CI 63-100%) for rK9, 38% (95%CI 28-59%) for rK26, 100% for rK39, and 80% (95% CI 65-100%) for CSA. The specificity of rK9, rK26, rK39 and CSA was found to be 84% (95%CI 61-100%), 80% (95%CI 56-100%), 96% (95%CI 75-100%) and 72% (95%CI 49-100%), respectively.

Conclusions: rK39 was observed to be the most suitable antigen as compared to rK26 and rK9 whereas rK9 performed better than rK26. Hence rK9 antigen may either be used as an adjunct to rK39 for accurate diagnosis of VL or may be used in the absence or non-availability of rK39 antigen for the serodiagnosis.