The cross-reactivity spectrum of a polyclonal antiserum raised against the native amplified a2 esterase involved in insecticide resistance

Broad-spectrum insecticide resistance in the mosquito Culex quinquefasciatus is usually due to the overproduction of A- and B-type carboxylesterases (EC 3.1.1.1). Antiserum was raised against the carboxylesterase A2 purified from an organophosphate-resistant Culex strain. This antiserum was used to show that, contrary to earlier reports, the A(2) esterase is immunologically related to other A- and B-type carboxylesterases from resistant and susceptible Culex strains. Dot-blot immunoassays revealed that the purified esterase B2 is about 50-fold less reactive with the antiserum than the purified esterase A2. A strong immunological relationship was observed between the A2 antiserum and the organophosphate and carbamate target site acetylcholinesterase. A lower cross-reactivity with Anopheles stephensi esterases and no reactivity with resistance-associated esterases from grain beetles, planthoppers, and cockroaches were observed. The antiserum cross-reacted with some commercially available vertebrate esterases indicating its affinities with these enzymes. The observed cross-reactivity is not due to the antiserum cross-reacting with glycosylated residues, as the A2 esterase to which the antiserum was raised is unglycosylated. The utility of this antiserum in future esterase cDNA cloning programs is discussed.