DIFFERENTIAL RECOGNITION OF STEREOCHEMICALLY DEFINED BASE ADDUCTS BY ANTIBODIES AGAINST ANTI-BENZP[A]PYRENE DIOL-EPOXIDE-MODIFIED DNA

The configurational isomers of benzo[a] pyrene diol-epoxide exhibit a range of reactivity, adduct profiles, genotoxic, mutagenic and tumorig enic responses. Whilst the (+)-enantiomer of 7 beta,8 alpha-dihydroxy- 9 alpha,10 alpha-epoxy-7,8,9,10-tetra-hydrobenzo[a] pyrene (anti-BPDE) is the most potent genotoxic species, studies dealing with many criti cal aspects of BPDE genotoxicity have predominantly been done with the racemic mixture of anti-BPDE. By utilizing highly sensitive non-compe titive immunoassays, we have shown that both polyclonal and monoclonal antibodies developed against anti-BPDE-modified DNA exhibit a high de gree of stereospecific adduct selectivity with 11mer oligodeoxynucleot ides containing a single well-defined base adduct. The polyclonal anti body (PAb BP1) distinctly recognized the highly carcinogenic lesion ()-anti-BPDE-N-2-dG with a 40-fold preference over the (-)-anti-BPDE-N- 2-dG adduct. In contrast, the monoclonal antibody (MAB 5D2) bound avid ly to (-)-anti-BPDE-N-2-dG and exhibited very little affinity for the (+)-anti-BPDE-N-2-dG adduct. The overall sensitivity of detection of p olyclonal antibodies for adducts in (+/-)-anti-BPDE-modified DNA was a bout 90-fold higher than monoclonal antibodies. Neither antibody showe d any detectable reactivity with (+)- or (-)-anti-BPDE-N-6-dA and with unmodified DNA antigens. The distinct preference of antibodies for pa rticular enantiomeric adducts was observed in both single and duplexed oligomeric conformations. The demonstrated differential interaction o f antibodies with the established conformations of (+)- and (-)-enanti omer anti-BPDE-DNA adducts (de los Santos et al., Biochemistry, 31, 52 45-5252, 1992), has significant implications for in vitro and in vivo adduct processing and risk assessment biomonitoring studies.