An immunodominant antigen on theDictyocaulus viviparusL3 sheath surface coat and a related molecule in other strongylid nematodes

Abstract

Monoclonal antibody 2A6 binds to the surface of the Dictyocaulus viviparus L3 sheath and identifies a molecule which is highly antigenic in both infected and vaccinated cattle. Immunogold electron microscopy reveals that the antibody binds to a highly stable surface coat overlying the epicuticle of the L3 sheath. The binding to the cuticular surface is stage specific, being restricted to the surface of the L3 sheath, although the antigen can be detected on Western blots of parasite homogenates from the L1 stage. Immunofluorescence on live parasites demonstrates that the antibodies also bind to the L3 sheath surface of many other strongylid nematodes. The antigen detected by 2A6 differs in molecular weight between the species; in D. viviparus the antigen is poorly resolved between 29 and 40 kDa by SDS-PAGE whereas in nematodes from the family Trichostrongyloidea a single band or doublet of approximately 20 kDa is detected, suggesting that a related molecule is present in these species. Although infection and vaccination with D. viviparus elicits a strong immune response to the L3 sheath antigen this does not appear to be the case following infection with other strongylid nematodes.