Comparison of isolates and species ofToxocaraandToxascarisby biosynthetic labelling of somatic and ES proteins from infective larvae

Abstract

Infective-stage larvae of three different isolates ofToxocara caniswere intrinsically ([35S]methionine) labelled in culture, to determine the presence of similarities or differences in the somatic and ES antigens expressed between larvae derived from different hosts and different geographical regions. Two other closely related ascaridids,Toxascaris leoninawhich infects cats and dogs, andToxocara vitulorum(Neoascaris vitulorum) which infects cattle, were also compared toT. canislarvae by this method. Overall comparisons were made by 1- and 2-dimensional electrophoresis, while immunological cross-reactivities between the different species were analysed by radio-immunoprecipitation. Our results show that extensive physicochemical characteristics are shared betweenT. canisisolates, both from different hosts and different geographical locations. A substantial overlap was revealed whenT. canisandT. vitulorumantigens were compared, whereasToxascariswas found to produce a distinct antigen profile: this result was independent of whether methionine- or Iodogen-labelled products were being considered. Antigen recognition by polyclonal antibodies raised to all three species and to the cat ascarididToxocara cati, revealed considerable cross-reactivities. The cross-reactions were especially prominent between theToxocaraspecies, a fact further substantiated when reactivity ofT. canisES-specific monoclonal antibodies were tested againstT. leoninaandT. vitulorumantigens. The ES antigens ofT. leoninawere not recognized by theT. canismonoclonals, whereas the majority of these antibodies precipitated antigens ofT. vitulorum. One which did not react withT. vitulorumwas monoclonal antibody Tcn 2, indicating its species-specific reactivity and therefore its potential for the specific diagnosis of human toxocariasis.