Changing proteins on the surface of a parasitic nematode.

Most of the organisms of the phylum Nematoda are free living, but some are animal or plant parasites of major importance to man. During their life cycle all nematodes undergo a series of moults in which they shed an external cuticle, consisting of an outermost membrane-like layer of unknown composition and a series of fibrillar layers similar to collagens. Because of this structure, the cuticle has been viewed as an acellular exoskeleton with rather inert molecular components. However, observations have shown that it contains enzymes and sometimes haemoglobin, and that nutrients are absorbed through it in the infective larvae and adut stages of Brugia pahangi. It is bound by complement and antibody, resulting in the adherence of leukocytes, and antibody-dependent cell-mediated reactions damage the cuticle of newborn larvae of Trichinella spiralis and the microfilariae of Dipetalonema viteae and Litomosoides carinii. We report here that the surface of the cuticle of the parasitic nematode Trichinella spiralis expresses protein molecules which change qualitatively following the moulting process, and quantitatively during growth of the worms within one stage. Also, surface proteins are released in vitro at a rate which depends on the conditions of culture of the worms.