Localization of the predicted peptide from isotigs12596 in Onchocerca flexuosa by immunohistochemical labeling. Polyclonal antibodies raised against a predicted peptide from O. flexuosa with sequence similarity to aminopeptidase P from the Wolbachia endosymbiont of Muscidifurax uniraptor labeled the intestine, hypodermis, and basal layers of the muscle in male worms (A, D). Spermatogonia were labeled (see arrow in panel A, shown magnified in panel B), but spermatocytes (see arrowhead in panel A, shown magnified in panel C) and mature spermatozoa were not. The hypodermis was also intensely labeled in sexually immature (E) and older, mf producing females (G). The older females also showed labeling in the intestine (G), oocytes (F), uterus branches (G, H, I) and early embryos (G, arrow). Lighter labeling was observed in morulae (G, arrowhead) and pretzel stage embryos (H), but labeling intensity increased in curled and stretched microfilariae (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 = 25μm in panel F and 50μm in all other panels.