What to read after Ascaris: The Neglected Parasite?

In comparison with other helminths that afflict humans on a global scale, Ascaris lumbricoides and ascariasis are relatively under-researched in terms of the proteins and other products to which the parasites expose their hosts. The reputation of the parasite as a source of potent allergens, and the recognition that immune hypersensitivity in the lung caused by migrating larvae is a significant problem, has served to focus attention on immune responses to Ascaris. Research has increasingly focused on the parasite’s products and responses to them in experimental rodents, and in pigs as permissive hosts for the full life-cycle of Ascaris suum. In parallel, immunoepidemiology of ascariasis in humans has been developing, often aimed at understanding how the infection polarizes immune responses. This review deals with the antigens of the parasite, how the immune repertoire to them varies dramatically between infected humans, the genetic loci that are probably involved, and its unpredictability. New work on the molecular structure of the unusual proteins produced by Ascaris and other nematodes is also covered, including the well-known ABA-1 allergen. Emphasis is also placed on a poorly understood aspect of Ascaris immunobiology, prompted by a few tantalizing observations, namely the potential diversity of surface and secreted antigens of the human parasite, and how such polymorphisms could be crucial to understanding the chronicity of ascariasis in the face of continuous loss and recruitment of the parasites themselves.