Advancing a multivalent ‘Pan-anthelmintic’ vaccine against soil-transmitted nematode infections

Zhan, Bin; Beaumier, Coreen M; Briggs, Neima; Jones, Kathryn M; Keegan, Brian P; Bottazzi, Maria Elena; Hotez, Peter J

Most of the work on ascariasis vaccine antigens has focused on the larval stages of the pig roundworm Ascaris suum. A. suum is found in pigs worldwide and is closely related to A. lumbricoides. They are morphologically and antigenically indistinguishable and differ by only 4% in their mitochondrial genome sequence [18] . There is controversy in the literature about whether A. lumbricoides and A. suum should be considered separate species or as part of the same complex, and the extent to which either parasite can jump between humans and pigs [19] . The genome of A. suum has been completed [20], with A. lumbricoides to follow soon [19] , which should help to illuminate their differences. While A. suum can complete its life cycle in pigs, their large size and the costs and complexities of animal husbandry have limited the use of pigs for purposes of vaccine development. As a convenient alternative, incomplete A. suum infections can be established in mice and other rodent hosts [21] [22] [23] . Following oral administration of A. suum eggs, the released larvae migrate from the small intestine to the liver (where they create characteristic 'white spots') and lungs. As described below, experimental vaccines have been successfully developed, which can reduce the number of migrating larvae following challenge infections [21, 24] . These animal studies complement epidemiological studies conducted in human populations indicating that A. lumbricoides worm burdens in endemic areas and areas of high transmission are lower in adults than children [25] . Such observations are suggestive of possible evidence for acquired immunity.