Improved high-affinity monoclonal antibody to lododeoxyuridine

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Abstract
Three monoclonal antibodies (Mabs), IU‐1, IU‐4, and B‐44 were evaluated in enzyme immunoassays (ELISA) and by flow cytometry for their abilities to recognize bromodeoxyuridine (BrdUrd)‐ and iododeoxyuridine (IdUrd)‐substituted DNA's, nucleotides, and nucleosides. IU‐4 is a new Mab, derived from mice immunized with 5‐iodo‐2′‐deoxyuridine‐5′‐monophosphate (IdUMP) conjugated through the phosphate group to albumin. This immunogen was selected to resemble IdUMP in DNA. In competition ELISA assays, IU‐4 prefers IdUrd to BrdUrd and prefers halogenated nucleotides over the corresponding nucleosides. In both ELISA and flow analysis, IU‐4 recognizes IdUrd in DNA at substitution frequencies at least as low as one IdUrd one per 1,000 normal bases. The high affinity of IU‐4 for IdUrd‐DNA contrasts with IU‐1 and B‐44, which show a strong binding dependency on the frequency of base substitution and require DNA that is essentially fully substituted with BrdUrd for binding in both flow and ELISA assays. The high affinity of IU‐4 for IdUrd in DNA and its independence of IdUrd residue spacing make it a superior reagent for the quantitative labeling of halogenated thymidine analogues in whole cells.