Serological reactions to infection with Necator americanus

Abstract

Experimental human infection with larvae of Necator americanus gave rise to immediate antibody responses, demonstrable by fluorescent antibody, complement fixation and Prausnitz-Küstner reactions, which recurred after subsequent challenges. Haemagglutinating antibodies were detected 2 years after, first infection. No protective immunity developed, and titres of these reactions in naturally infected subjects were not related to worm loads. Larvae of N. americanus incubated in sera positive to the fluorescent antibody reaction showed precipitates on their surfaces when examined by electron microscopy. The sera of English subjects usually gave a negative fluorescent antibody reaction with larvae of N. americanus, but a positive reaction with various strongyloid larvae normally parasitic in animals.