Overproduction of detoxifying esterases in organophosphate-resistant Culex mosquitoes and their presence in other insects.

Antisera raised against the denatured polypeptide of two organophosphate-detoxifying esterases (B1 and A1) of Culex mosquitoes were used in an immunoblot method to quantify esterase production in resistant versus susceptible strains and to detect the presence of immunologically related proteins in other insects. It was demonstrated that esterase B1 of Culex quinquefasciatus and esterase A1 of Culex pipiens are overproduced in resistant strains by factors of at least 500-fold and 70-fold, respectively, as compared with the corresponding susceptible strains. These factors approximate the levels of resistance to the organophosphate chlorpyrifos determined by bioassay--i.e., about 800-fold and 100-fold, respectively. Antiesterase B1 antiserum was found to react with other type B esterases (B2 of C. quinquefasciatus and B3 of Culex tarsalis) but not with type A esterases (A1 of C. pipiens, A2 of C. quinquefasciatus, or A3 of C. tarsalis); similarly, antiesterase A1 antiserum was found to react with other type A esterases (A2 and A3) but not with type B esterases (B1, B2, and B3). Proteins immunologically related to esterase B1 were detected in Aedes aegypti L., Myzus persicae Sultzer, and Musca domestica L., although they were not overproduced in the organophosphate-resistant strains of these species. In none of these species were proteins immunologically related to esterase A1 found.