Surface properties of developing stages of Trichuris muris.

Abstract

Surface properties of developing stages of Trichuris muris were investigated by analysis of binding affinities for specific anti-parasite antibodies present in a range of infection sera; in vitro eosinophil adherence studies; and binding of the fluorescent-labelled lectins, Con A, WGA, PNA and RCA. In general, larvae of any one particular stage did not bind anti-parasite antibodies present in serum collected at an earlier stage of the infection, thus indicating a considerable degree of antigenic stage-specificity. Forty day and older parasites displayed similar binding properties and it is suggested that no major changes in surface antigenicity occur after the final moult at day 25-30 after infection. Surface properties were also examined by means of complement and antibody-mediated eosinophil adherence assays. Attachment of eosinophils was maximal with day 5 larvae, although even at this stage not all of the parasite surface was covered with attached cells. Despite adherence, eosinophils were unable to effect parasite killing, even after 48 h of incubation. These studies showed that eosinophil adherence-promoting antibodies were present in immune sera; that the larval parasite surface was able to activate complement by the alternate pathway with subsequent generation of C3b molecules, and that the parasite was able to withstand eosinophil adherence and secretion by an as yet unidentified evasive stratagem. Studies with fluorescent-labelled lectins showed that all larval stages (days 5-25 after infection) were positive for Con A binding. Early larval stages (days 5-10 after infection) also bound PNA and WGA. Interestingly, recently moulted individuals rarely exhibited fluorescence, but cast cuticles fluoresced brightly.