A paper published in this week's PLoS Medicine shows thatvaccination against a protein secreted by the dog hookworm can protectagainst blood loss and anaemia caused by the same hookworm in dogs. Theresearchers, led by Alex Loukas and Peter Hotez, showed thatvaccination of dogs with recombinant Ac-APR-1, an enzyme that startsthe digestion of hemoglobin in hookworms, induced an immune responseand resulted in significantly reduced hookworm burdens and fecal eggcounts in vaccinated dogs compared to control dogs after challenge withinfective larvae of the hookworm Ancylostoma caninum. Most importantly,vaccinated dogs were protected against blood loss and most did notdevelop anemia, the major result of hookworm disease.
Hookwormsare intestinal parasites of mammals, including humans, dogs, and cats;in humans these infections are a leading cause of intestinal blood lossand iron-deficiency anemia. Hookworm infections occur mostly intropical and subtropical climates and are estimated to infect about 1billion people worldwide-- about one-fifth of the world's population.People who have direct contact with soil that contains human feces inareas where hookworm is common are at high risk of infection; becausechildren play in dirt, they are at the highest risk.
Theseresults set the stage for the next stage of vaccine development inhumans. Loukas and colleagues suggest that the ideal hookworm vaccinewould be a mixture of two recombinant proteins, targeting both theinfective larva and the blood-feeding adult stage (as targeted here) ofthe parasite. Such a vaccine would limit the amount of blood losscaused by feeding worms and maintain normal levels of hemoglobin.
Citation:Loukas A, Bethony JM, Mendez S, Fujiwara RT, Goud GN, et al. (2005)Vaccination with recombinant aspartic hemoglobinase reduces parasiteload and blood loss after hookworm infection. PLoS Med 2(10): e295.
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