WUCHERERIA-BANCROFTI - IDENTIFICATION OF PARASITIC ACETYLCHOLINESTERASE IN MICROFILARIAE INFECTED HUMAN SERUM

An antigen with cholinesterase activity was detected in the sera of pa tients infected with Wuchereria bancrofti. The asymptomatic microfilar emic sera showed 3 to 4 times more cholinesterase activity for acetylt hiocholine (ATCh) as compared to sera of symptomatic amicrofilaremic, hookworm infected and endemic normals, whereas the activities for buty rylthiocholine (BTCh) did not significantly differ. The enzyme activit ies from both sources, namely from sera of microfilaremic cases and fr om endemic normals, were partially purified and according to substrate specificity for ATCh and BTCh as well as inhibition of the former act ivity by excess substrate classified as acetylcholinesterase (AChE; EC 3.1.1.7) and pseudocholinesterase (AChE; EC 3.1.1.8), respectively. T he K(m)-value for ATCh of the cholinesterase from the microfilaremic s era was determined to be 0.87 mM. Eserine competitively inhibited the AChE activity; the inhibition constant was found to be 1.3 muM. The BC hE from the normal sera had K(m)-values of 0.15 and 0.20 mM for BTCh a nd ATCh, respectively, and did not show significant inhibition by eser ine. These and other dissimilarities suggest a difference in nature of the cholinesterases in microfilaremic and normal sera and propose tha t the former enzyme, a true acetylcholinesterase, originates from the parasite. Additional evidence for the origin of the AChE-activity from the parasite was provided by ELISA-studies; anti-Brugia malayi AChE a ntibodies confirmed antigenecity and cross reactivity of the AChE in i nfected sera, whereas the antibodies did not show any cross reactivity with the BChE in normal sera.