Immunocytochemical and ultrastructural studies on Dipetalonema viteae (Filarioidea)

The antigenic properties of adult male and female of Dipetalonema viteae were studied by immunocytochemistry. Using antisera of the rodents Meriones unguiculatus and Mastomys natalensis infected with D. viteae, the binding of antibodies to sections of filariae embedded in Epon was assayed by the peroxidase-antiperoxidase (PAP) technique and by electron microscopy. The optimal staining intensity was obtained with an antiserum dilution of 1:5000. Control sera were obtained from sex and age matched uninfected animals. Female D. viteae showed maximal antigen-antibody reactions within the uterus: in the inner uterus wall, in the "nutrient channels" between the maturing eggs and the differentiating microfilariae, on the eggshells, in the cuticula of microfilariae and in the spermatheca on the cell membrane of the mature spermatozoa. Male filariae showed binding of antibodies in the vesicula seminalis: in the nucleus and the nuclear membrane of primary spermatocytes and on maturing spermatids. Less pronounced antigen-antibody reactions in the cuticula, muscle and intestine were observed in both sexes. The PAP-technique offers significant improvements in comparison with other techniques, e.g., immunofluorescence, used to detect antigens on filariae: the PAP-technique has an increased sensitivity with a concomitant reduction in nonspecific background and can be used for both light and electron microscopy; moreover, PAP-treated tissues can be stored indefinitely at room temperature.