Carlo Antonio Nuzzolo

A Rapid Inhibition Micro ELISA for Detecting Antibodies to Plasmodium Falciparum Sporozoites in Human Blood

A sensitive and specific micro ELISA, named MONOPLATE ELISA, for the detection of antibodies against P. falciparum sporozoites was developed. It can be applied to many kinds of samples including serum, plasma, whole blood, eluted bloodspot and mosquito bloodmeal as well. The method makes use of a single microtiter plate and the chemically synthesized (Asn-Ala-Asn-Pro)20 (NANP20) antigen both as coating material and as competitive (binding) inhibitor in the samples. The specific value of each sample is obtained as the absorbance difference between the uninhibited and the fully inhibited sample. Using appropriate conditions, the results can be evaluated by simple visual inspection of the plate, without any instrument. A rapid procedure, where the incubation times for sample and conjugate are just 15 minutes, is also described. When unknown samples from a P. falciparum endemic area were tested, a close correlation was found between our results and those obtained with the only commercial ELISA kit now available (Sclavo S.p.A). For screening purposes, as many as 48 samples per plate can be tested by this method.