Bioinformatic identification of tandem repeat antigens of the Leishmania donovani complex

With large amounts of parasite gene sequence available, additional bioinformatic tools to screen these sequences for identifying genes encoding antigens are needed. Proteins containing tandem repeat (TR) domains are often B-cell antigens, and antibody responses toward TR domains of the proteins are dominant in human infected with certain parasites. We hypothesized that antigens of serological significance could be identified with a search for TR domains. Here we show the result of bioinformatic screening of the gene sequence database of the parasitic protozoan Leishmania infantum. Of 8,191 genes scanned, 64 genes contained TR domains. Of the 64 genes, 22 encoded previously characterized antigens; the remaining 42 genes were previously uncharacterized. By using sera from Sudanese visceral leishmaniasis patients, we confirmed that the TR domains of LinJ11.0070, Linj25.1100, Linj27.0400, and Linj29.0110, which were from the 42 uncharacterized proteins, are also antigenic. The results suggest the validity of this approach for identifying leishmanial antigens of serological significance.