Brugia malayi: resistance of cuticular lipids to oxidant-induced damage and detection of alpha-tocopherol in the neutral lipid fraction.

We have examined the susceptibility of cuticular membrane lipids of Brugia malayi to oxidants generated in vitro. Live parasites as well as extracted cuticular lipids were treated with hydrogen peroxide and hypochlorous acid and the extent of lipid peroxidation was quantified. The cuticular membranes of B. malayi were found to be resistant to lipid peroxidation at hydrogen peroxide concentrations which were lethal to the organism. This resistance was partly due to the inherently low unsaturation indices of the fatty acyl residues, but complete protection was afforded by lipid-soluble antioxidants present in the neutral lipid fraction of the parasites. We have identified alpha-tocopherol as a major antioxidant present in both adult and microfilarial B. malayi. In addition, we report that although hypochlorous acid chemically modifies isolated parasite lipids, the latter do not appear to be the primary substrate for the oxidant in live worms. The data are discussed in terms of the susceptibility of B. malayi to products of the respiratory burst from activated myeloid cells.