Protective immunity to Nippostrongylus brasiliensis in the rat. 3. Modulation of worm acetylcholinesterase by antibodies.

Abstract

Antibodies to Nippostrongylus brasiliensis acetylcholinesterase were found in sera from infected rats and in one pooled sample were associated with IgG(1). Antibodies were formed against all three isoenzymes of worm acetylcholinesterase and antisera taken from animals which had experienced multiple infections had the strongest activity, in particular to isoenzyme A. No antibodies were found against the worms' non-specific esterases, aminopeptidases or acid phosphatases. It appeared that acetylcholinesterase production by the worms was increased in the presence of antibodies and decreased in their absence. The evidence for this conclusion is as follows. First, adapted worms, which are found in rats with high levels of antibodies to all three isoenzymes, had an increased production of these isoenzymes. However, when these adapted worms were transferred to non-immune rats, their production of isoenzyme A was rapidly reduced. Secondly, in rats passively immunized with antiserum containing antibodies to acetylcholinesterase, the worms had increased levels of this enzyme. Thirdly, cortisone treatment of immune rats completely prevented immunity from acting on the worms; the acetylcholinesterase production of these worms was low compared with adapted worms from untreated immune rats and was similar to that of normal worms from non-immune rats. These experiments provide evidence that antibodies to this enzyme are one factor which modulates acetylcholinesterase production by this nematode.