Detection of specific IgM antibodies to toxocaral ES antigen: effect of absorption of sera with protein A sepharose.

The activity of both the IgG and IgM antibodies to ES antigen from Toxocara canis larvae was tested before and after absorption of sera by protein A Sepharose 4B (PASB). For this purpose, the ELISA technique was applied to the sera from 12 dogs and 6 infants. The effect of absorption of sera by PASB was as follows. The average values before and after absorption in dog sera were 0.11 and 0.02, respectively. The same effect was observed in the infant sera. Of the 12 dog sera tested, four had a elevated IgM activity and three were considered to be false positive. Also, two adult dogs in chronic infection had a IgM antibody. Of the six infant sera tested, one had a slightly elevated IgM activity and no false positive and negative readings were found. The results of this work indicated that the absorption of sera with protein A might be useful in detecting the IgM antibodies to ES antigen. Although the false positive readings appeared without absorption of sera, misreadings hampered by the amount of IgG be eliminated after absorption.