Immune responses following experimental human hookworm infection

To characterize the immune response following primary human hookworm infection, an adult volunteer was infected with 50 L3 larvae of Necator americanus, reinfected 27 months later and followed for a further 6 months. Clinical signs, blood picture, ex-vivo peripheral blood cytokine production (IFN-gamma, IL-5, IL-13, IL-10 to mitogen and hookworm antigen), acute phase proteins (APP) (C-reactive protein, CRP and alpha 1-antitrypsin, alpha 1-AT) and antibody levels were determined. Dermatitis, oedema, mild nausea and abdominal discomfort followed the primary infection. Eosinophil counts peaked early during both infections but remained elevated (similar to 18%) throughout. Transient production of IL-5, IL-13 and APP also followed infection but there were negligible levels of IFN-gamma or IL-10. The onset of nausea, oedema and the initial rise in CRP, alpha 1-AT, eosinophilia and IL-5 coincided (days 13-27) with the late larval migration and early establishment of the preadult worms in the intestine. Apart from the eosinophilia these responses declined to baseline levels within 4 months and were less pronounced on re-infection.