Immune response to opiates: New findings in heroin addicts investigated by means of an original enzyme immunoassay and morphine determination in hair

Abstract

In the early 1970's, some papers appeared reporting an immune response to opiates in animals treated with morphine and in heroin addicts, but further researches failed to confirm these results in humans. The aim of the present work is investigating with a newly developed enzyme immunoassay the existence of specific antibodies to morphine in a group of opiate chronic users, controlled by means of the toxicological analysis of hair. Twenty five opiate addicts inpatients for detoxication treatments were investigated for the presence of morphine specific antibodies and for the morphine content in hair, as a marker of addiction to opiates. Antibodies to morphine were investigated using an original ELISA method using a morphine-human serum albumin conjugate immobilized into the wells of polystyrene microtiter plates. Morphine determinations in hair were accomplished by a radioimmunologic screening followed by HPLC confirmation of positive results. The group of opiate users, in which all the subjects resulted positive for morphine content in hair, showed in the ELISA test an average D OD% value significantly higher than the control group (p<0.001); in particular, 16 out of 25 addicts could be classified positive for anti-morphine antibodies, which were identified as IgM. Inhibition studies demonstrated Ka's for morphine ranging from 10 4 to 10 10 M −1 and a high cross reactivity for codeine. The presence of circulating antibodies specific to morphine in chronic users of opiates is strongly supported by the present findings.