Antibody to Trypanosoma cruzi neuraminidase enhances infection in vitro and identifies a subpopulation of trypomastigotes
Cavallesco, R.; Pereira, M.E.
Journal of Immunology 140(2): 617-625
1988
ISSN/ISBN: 0022-1767 PMID: 3121750 Document Number: 322074
A rabbit antibody to the neuraminidase of the infective form of Trypanosoma cruzi identifies a subpopulation of trypomastigotes that expresses neuraminidase. Complement-mediated lysis by the antibody selectively destroys 30 to 40% of the trypomastigotes, supporting the conclusion that the immune antibody binds to a subset of parasites. The trypomastigotes that react with the immune antibody are the only ones expressing neuraminidase because the trypomastigotes that survive complement-mediated lysis are depleted of neuraminidase activity. The enzyme seems to negatively modulate infection in vitro, since infection of host cells by trypomastigotes is enhanced when neuraminidase activity is blocked by antineuraminidase antibody; infection is also enhanced when the infecting trypomastigotes have been depleted of parasites that express neuraminidase. Addition of exogenous neuraminidase (from Vibrio cholerae) to trypomastigotes treated with immune antibody, reverts the enhancement observed when infection takes place in the presence of antibody to T. cruzi neuraminidase only. Addition of V. cholerae neuraminidase in the absence of immune antibodies has no effect on infection. These results show that T. cruzi neuraminidase depresses infection and also suggest that sialic acid is involved in the parasite-host cell interaction. The antibody to T. cruzi neuraminidase recognizes on the surface of live trypomastigotes a set of proteins with high m.w. (165 000 to 200 000) and also two antigens of 79 000 to 82 000. The high m.w. proteins appear to be associated with neuraminidase activity as shown by renaturation experiments of released enzyme fractionated on a sodium dodecyl sulfate-polyacrylamide gel.AS/Wendy Gibson In vitro studies showed that a rabbit antibody to the neuraminidase of the infective form of T. cruzi identifies a subpopulation of trypomastigotes that expresses neuraminidase. Complement-mediated lysis by the antibody selectively destroyed 30 to 40% of the trypomastigotes, supporting the conclusion that the immune antibody binds to a subset of parasites. The trypomastigotes that reacted with the immune antibody were the only ones expressing neuraminidase because the trypomastigotes that survived complement-mediated lysis were depleted of neuraminidase activity. The enzyme seemed to negatively modulate infection in vitro, since infection of host cells by trypomastigotes was enhanced when neuraminidase activity was blocked by antineuraminidase antibody; infection was also enhanced when the infecting trypomastigotes were depleted of parasites that express neuraminidase. Addition of exogenous neuraminidase (from Vibrio cholerae) to trypomastigotes treated with immune antibody, reverted the enhancement observed when infection occurred in the presence of antibody to T. cruzi neuraminidase only. Addition of V. cholerae neuraminidase in the absence of immune antibodies had no effect on infection. These results show that T. cruzi neuraminidase depresses infection and also suggest that sialic acid is involved in the parasite-host cell interaction. The antibody to T. cruzi neuraminidase recognized on the surface of live trypomastigotes a set of proteins with high MW (165 000 to 200 000) and also 2 antigens with MWs of 79 000 to 82 000. The high MW proteins appear to be associated with neuraminidase activity as shown by renaturation experiments of released enzyme fractionated by SDS-PAGE.