Surface proteins of a filarial nematode: a major soluble antigen and a host component on the cuticle of Litomosoides carinii

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Abstract
The surface composition of 3 stages in the life cycle of L. carinii, a filarial parasite of rodents, was studied using radioiodination techniques. Confirmation that radiolabeled components were confined to the parasite surface was achieved using light microscope and EM autoradiography. Biochemical analysis of extracts of radiolabeled parasites by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) revealed that one major component (MW 55,000) could be solubilized with the aid of detergents. This component, which was present on male and female adult worms, and on postparasitic 3rd stage larvae, accounted for .apprx. 1/3 of the total proteins available for surface iodination, and was antigenic in infected hosts. The remaining surface components could be solubilized only with urea and SDS under reducing conditions. The 55,000 MW surface antigens of male and female adult worms exhibited identical 2-dimensional tryptic maps, but the similar 55,000 MW antigen of postparasitic 3rd stage larvae was different. There was some sharing of antigenic determinants between adult and larval surface components. The principal protein present in detergent extracts of surface-radiolabeled blood microfilariae was host serum albumin.