Differential recognition of stereochemically defined base adducts by antibodies against anti-benzo[a]pyrene...

The configurational isomers of benzo[a]pyrene diol-epoxide exhibit a range of reactivity, adduct profiles, genotoxic, mutagenic and tumorigenic responses. Whilst the (+)-enantiomer of 7 beta,8 alpha-dihydroxy-9 alpha,10 alpha-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (anti-BPDE) is the most potent genotoxic species, studies dealing with many critical aspects of BPDE genotoxicity have predominantly been done with the racemic mixture of anti-BPDE. By utilizing highly sensitive non-competitive immunoassays, we have shown that both polyclonal and monoclonal antibodies developed against anti-BPDE-modified DNA exhibit a high degree of stereospecific adduct selectivity with 11mer oligodeoxynucleotides containing a single well-defined base adduct. The polyclonal antibody (PAb BP1) distinctly recognized the highly carcinogenic lesion (+)-anti-BPDE-N2-dG with a 40-fold preference over the (-)-anti-BPDE-N2-dG adduct. In contrast, the monoclonal antibody (MAb 5D2) bound avidly to (-)-anti-BPDE-N2-dG and exhibited very little affinity for the (+)-anti-BPDE-N2-dG adduct. The overall sensitivity of detection of polyclonal antibodies for adducts in (+/-)-anti-BPDE-modified DNA was about 90-fold higher than monoclonal antibodies. Neither antibody showed any detectable reactivity with (+)-or (-)-anti-BPDE-N6-dA and with unmodified DNA antigens. The distinct preference of antibodies for particular enantiomeric adducts was observed in both single and duplexed oligomeric conformations. The demonstrated differential interaction of antibodies with the established conformations of (+)- and (-)-enantiomer anti-BPDE-DNA adducts (de los Santos et al., Biochemistry, 31, 5245-5252, 1992), has significant implications for in vitro and in vivo adduct processing and risk assessment biomonitoring studies.