Chitin synthesis and sheath morphogenesis in Brugia malayi microfilariae

Brugia malayi microfilariae and gravid adult females were examined to determine whether chitin (poly beta(1----4)-linked N-acetylglucosamine) is a structural component of the microfilarial sheath. Two lectins which are specific for beta(1----4)-linked oligomers of N-acetylglucosamine bind to the sheaths of living microfilariae. Diflubenzuron, a potent inhibitor of chitin synthesis in insects and crustaceans, causes gravid female worms to shed progeny microfilariae with truncated sheaths. A chitin-like fraction (hot alkali-insoluble and chitinase-sensitive) can be isolated from gravid female (but not male) worms. This fraction can be metabolically labelled with radioactive glucosamine, but such labelling is inhibited by diflubenzuron. These data suggest that chitin synthesis is critical to microfilarial sheath morphogenesis in this parasitic nematode.