Localization of the putative HlyD peptide in Onchocerca flexuosa by immunohistochemical labeling. Polyclonal antibodies raised against a peptide from the HlyD protein of the Wolbachia endosymbiont of Culex quinquefasciatus labeled the intestine and hypodermis, lateral chords, and median chords in male worms (A, B, C). The antibodies also labeled spermatogonia (A) and spermatocytes (B) in the testis but not mature spermatozoa in the vas deferens (C). The intensity of labeling in the hypodermis, lateral chords and median chords appeared to decrease towards the posterior end of males in the vicinity of mature sperm (compare C to A and B). Likewise, antibodies also labeled the intestine, hypodermis, lateral chords, and median chords of sexually immature (D) and older, mf producing females (F). In the older females, intense labeling was seen in the oocytes within the ovaries (E) and in early embryos in the uterus (F, arrow). Labeling faded in later morulae (F, arrowhead) and pretzel stage embryos (G) but reappeared on particular regions of the outer surface of curled and stretched microfilariae (H, I). Abbreviations: cu, cuticle; hy, hypodermis; m, muscle; lc, lateral chords; mc, median chords; i, intestine; ut, uterus; utw, uterine wall; t, testis; vd, vas deferens. Scale bar = 5μm in panel I and 50μm in all other panels. Panels A-G shows results obtained with the alkaline phosphatase anti-alkaline phosphatase method. Panels H and I show results obtained with a fluorescein labeled secondary antibody (green); membranes labeled with wheat germ agglutinin appear red, and nuclei stained with DAPI are blue.