The neuraminidases of Trypanosoma cruzi and Acanthamoeba castellanii are immunologically related.

We have recently reported the presence of neuraminidase (NA) activity in Acanthamoeba castellanii. We now show that the NAs of T. cruzi and A. castellanii share cross-reactive determinants using TCN-2, a monoclonal antibody (mAb) against the T. cruzi NA and a mouse polyclonal Ab (anti-TR) raised against a tandemly repeated dodecapeptide which contains the epitope recognized by TCN-2 (Prioli et al., submitted). This cross-reactivity was demonstrated by the reaction of TCN-2 and anti-TR with A. castellanii parasites using immunofluorescence, immunoblotting and ELISA. Inhibition and immunoprecipitation of enzyme activity confirmed that the A. castellanii antigen recognized by TCN-2 was the NA. Immunoprecipitation of [35S] labeled trophozoite lysates showed the A. castellanii NA to have a molecular weight of 115 kDa. In addition, immunoblot analysis of subcellular fractions obtained by ultracentrifugation showed the A. castellanii NA to be associated with the parasite membrane but not with the cytosol or cytoskeleton fractions. These results suggest that the TCN-2 epitope, contained within a dodecamer tandem repeat unit, is present in T. cruzi and A. castellanii NAs.