<unk>  infections in humans can last for several years, and re-infection can occur very shortly after treatment, suggesting that<unk> s effectively evade—and may interrupt or modulate—the host immune system. Successful<unk> s have been developed for several animal species. On the basis of prior work, human vaccine development has targeted antigens from both the larval and adult stages of the<unk>  life cycle; a combined vaccine for humans that would provide more complete protection. Current targets of larval proteins attenuate larval migration through host tissue; targets of adult proteins have been demonstrated to block enzymes vital to<unk>  feeding. The function of Na-ASP-2 is not currently known (though it may function as a chemotaxin mimic), but it is a cysteine-rich secretory protein that is released during parasite entry into the host. It may have some function in the transition from the larval environment stage of the<unk>  life-cycle to an adult parasitic existence and tissue migration. The class of proteins that includes Na-ASP-2, ASPs, are promising vaccine candidates based on previous vaccine studies in sheep, guinea pigs, cattle, and mice, which have demonstrated inhibition of<unk>  larval migration. Furthermore, epidemiologic studies determined that high titers of circulating antibodies against ASPs are associated with lower<unk>  burdens in residents of Hainan Province, China, and Minas Gerais, Brazil. Ac-APR-1 is an aspartic protease, specifically a hemoglobinase, that participates in the<unk> 's digestion of hemoglobin from its blood meal and is present in the adult stage of the<unk>  life cycle. Animals immunized against Ac-APR-1 exhibited a reduction in worm burden, a reduction in hemoglobin loss, and a dramatic reduction in worm fecundity.
Hookworm vaccine
Schistosomiasis vaccine
Malaria vaccine
Trypanosomiasis vaccine
Leishmaniasis vaccine
Edible vaccines
Pipeline vaccine
Cholera vaccine