A double antibody sandwich ELISA for the diagnosis of vivax malaria: a tool for further researc

Abstract

A diagnostic assay for Plasmodium ohtaxbased on a double antibody sandwich enzyme-linked immunosorbent assay (DAS ELISA) was established to detect the merozoite surface protein L (PvMSPl) in wild isolates. This assay was based on the recombinant protein p19, a C-terminal processing product of PvMSPL. Of the two anti-P. zzbar monoclonal antibodies (MAbs) selected, A21 was used as the capture antibodywhile horse radish peroxidase labelled A8 served as the probing second antibody. Optimized conditions established for p19 based DAS ELISA with the exception of a lower concentration of Tween-20 in buffers were suitable to screen lysed whole blood of malaria patients. This assay had a specificity of t00% for P. aiaax and all the isolates of P. falciparumtested negative. Of the P. aiaax-infected blood samples, only those containing both compact and schizont stages were diagnosed positive. The rest of the isolates tested negative either due to stage specificity of this assay or to the antigenic diversity of PvMSPI in wild isolates. This test demonstrated a sensitivity of 27.58% and an accuracy of 63.1,5oh. The positive and negative predicted values of this ELISA were 100% and 57.1,4"/", respectively. Therefore, the P. uiaax speci-fic DAS ELISA developed and tested in the present study is not sufficiently sensitive to be used as a diagnostic tool for vivax malaria. Nevertheless, a baseline was established for development of diagnostic ELISA for future use with a more appropriate antigen.