Hookworm vaccine

Hookworm vaccine is a vaccine against hookworm. No effective vaccine for the disease in humans has yet been developed. Hookworms, parasitic nematodes transmitted in soil, infect approximately 700 million humans, particularly in tropical regions of the world where endemic hookworms include Ancylostoma duodenale and Necator americanus. Hookworms feed on blood and those infected with hookworms may suffer from chronic anaemia and malnutrition. Helminth infection can be effectively treated with benzimidazole drugs (such as mebendazole or albendazole), and efforts led by the World Health Organization have focused on one to three yearly de-worming doses in schools because hookworm infections with the heaviest intensities are most common in school-age children. However, these drugs only eliminate existing adult parasites and re-infection can occur soon after treatment, school-based de-worming efforts do not treat adults or pre-school children, and concerns exist about drug resistance developing in hookworms against the commonly used treatments, thus a vaccine against hookworm disease is sought to provide more permanent resistance to infection.Hookworm infections in humans can last for several years, and re-infection can occur very shortly after treatment, suggesting that hookworms effectively evade—and may interrupt or modulate—the host immune system. Successful hookworm vaccines 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 hookworm 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 hookworm feeding.Examples of antigenic targets of hookworm vaccines currently in clinical trials include Na-ASP-2 from N. americanus, Ac-APR-1 from Ancylostoma caninum, Ac'-APR-1 and Na-GST-1/Alhydroge. In a clinical trial a vaccine containing recombinant Na-ASP-2 with Alhydrogel as an adjuvant was found to increase Th2 helper cells and IgE. Both the Th2 helper cells and IgE antibody are important players in recognition and immunoregulation against parasites. The vaccine containing recombinant Na-ASP-2 resulted in significantly decreased risk of a hookworm infection.