LIGHT AND ELECTRON IMMUNOHISTOCHEMICAL ASSAYS ON PARAMYXEAN PARASITES

An indirect fluorescent antibody test (IFAT) incorporating a polyclona l antibody to Marteilia sydneyi recognized sporulating stages of M. sy dneyi from Saccostrea commercialis but not those of Marteilia refringe ns, M. maurini, Marteilia sp. and Marteilioides branchialis from Ostre a edulis, Mytilus galloprovincialis, Mytilus edulis and Saccostrea com mercialis respectively. This indicates that the antibody had a high sp ecificity and that the other parasites were immunologically distinct f rom M. sydneyi. Immunoelectron microscopy was used to investigate back ground labelling and the specificity of the antibody to antigenic site s. It showed that though most immunoglobulins were specific to parasit e epitopes, some reacted to host tissue. IFAT's based on three monoclo nal antibodies raised against Marteilia sp. did not recognise spores o r other stages of M. sydneyi. An immunogold-silver staining technique using the polyclonal antibody to M. sydneyi failed to identify the pre sumed presporulation stage of M. sydneyi in the connective tissue of a recently infected host. This suggests the antigens were stage-specifi c. Thus a DNA probe rather than immunohistochemical tests may be more useful in investigating the life cycle of this parasite.