The surface lipid of parasitic nematodes: organization, and modifications during transition to the mammalian host environment.

The biophysical properties of the surface lipid of a range of nematode species and their developmental stages were examined, using fluorescent lipid probes and fluorescence recovery after photobleaching (FRAP). These methods can be applied to living, intact parasites, and the analysis confined to lipid on the outermost surface. In all cases, surface lipid was unusual in its selectivity for the insertion of the lipid probes. In addition, a polar lipid probe was generally not free to diffuse in the plane of the surface, in contrast to a non-polar lipid probe which was free to diffuse. This is evidence that the surface lipid layer is heterogeneous, and possibly comprises lipid domains. The infective larvae of Acanthocheilonema viteae, Nippostrongylus brasiliensis, Trichinella spiralis and Ostertagia ostertagi were found to exhibit a rapid change in lipophilicity upon exposure to conditions simulating entry into a mammalian host environment. Parasitic nematodes, therefore, present their hosts not only with a highly unusual biological surface, but also one which can be rapidly re-organised upon a change of environment.