Expression of cross-reactive surface antigens by microfilariae and adult worms of Brugia pahangi during infections in cats

Microfilariae of Brugia pahangi were labelled with 125-Iodine using the reagent IODOGEN. Electron microscope autoradiographs of sections of iodinated microfilariae showed that the label was strictly confined to their sheath. Adult worms were also iodinated by the same procedure. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) analysis of detergent extracts of radio-labelled parasites revealed components of molecular weights 113, 81-71, 46 and 33 kDa in microfilariae, and of molecular weights 29, 20 and 16 kDa in adult worms. All but the 33 kDa component of microfilariae were immunoprecipitable with sera of infected cats and therefore antigenic. Antibodies to the 81-71 kDa and the 46 kDa microfilarial antigens were detected by immunoprecipitation before patency. Similarly, the 29 kDa antigen of adult worms was immunoprecipitable before the fourth moult. Therefore, during infection in cats, these antigens cross-react with epitopes present on earlier developmental stages.