Molecular and biochemical analyses of combining sites of monoclonal anti-morphine antibodies

Systematic Structure-Based Virtual Screening Approach to Antibody Selection and Design of a Humanized Antibody against Multiple Addictive Opioids without Affecting Treatment Agents Naloxone and Naltrexone

Opioid drug use, especially heroin, is known as a growing national crisis in America. Heroin itself is a prodrug and is converted to the most active metabolite 6-monoacetylmorphine (6-MAM) responsible for the acute toxicity of heroin and then to a relatively less-active metabolite morphine responsible for the long-term toxicity of heroin. Monoclonal antibodies (mAbs) are recognized as a potentially promising therapeutic approach in the treatment of opioid use disorders (OUDs). Due to the intrinsic challenges of discovering an mAb against multiple ligands, here we describe a general, systematic structure-based virtual screening and design approach which has been used to identify a known anti-morphine antibody 9B1 and a humanized antibody h9B1 capable of binding to multiple addictive opioids (including 6-MAM, morphine, heroin, and hydrocodone) without significant binding with currently available OUD treatment agents naloxone, naltrexone, and buprenorphine. The humanized antibody may serve as a promising candidate for the treatment of OUDs. The experimental binding affinities reasonably correlate with the computationally predicted binding free energies. The experimental activity data strongly support the computational predictions, suggesting that the systematic structure-based virtual screening and humanization design protocol is reliable. The general, systematic structure-based virtual screening and design approach will be useful for many other antibody selection and design efforts in the future.

Four different clones of mouse anti-acetyllysine monoclonal antibodies having different recognition properties share a common immunoglobulin framework structure

By employing two different immunogens and two different antibody-screening strategies, we established four mouse hybridoma clones producing monoclonal antibodies against N epsilon -acetyllysine. Three different protocols were used in this study; i.e., mice were (1) immunized with an N epsilon -acetyllysine-containing peptide, Gly-Lys(Ac)- epsilon -aminocaproic acid (Aca)-Cys, conjugated to KLH, and the hybridoma clones were screened for their reactivity to a histone H3 peptide containing five acetyllysines; (2) immunized as in "1" and screened with chemically acetylated bovine serum albumin (BSA); (3) immunized with chemically acetylated keyhole limpet hemocyanin (KLH) and screened with chemically acetylated BSA. Antibodies produced by the four different hybridomas established here all reacted with acetyllysine residues, but their reactivity was not the same when evaluated with enzyme-linked immunosorbent assay (ELISA), Western blotting, and resonant mirror sensor analyses. Among the three protocols examined, protocol "3" was especially useful to obtain hybridomas producing anti-N epsilon -acetyllysine antibodies that could detect not only the acetylated histones but also other acetylated proteins. By cloning and sequencing the cDNAs encoding the variable regions of the antibodies, we found that their framework sequences were almost the same, which suggests that some framework amino acids in addition to their complementarity determining regions (CDRs) directly contribute to their recognition function.

Specificity and VH sequence of two monoclonal antibodies against the N-terminus of dystrophin

We have used a random library of 15-mer peptides expressed on phage to show that two monoclonal antibodies (mAbs) require only the first three amino acids of dystrophin (Leu-Trp-Trp) for binding. Since the mAbs recognize dystrophin in frozen muscle sections, the results suggest that this hydrophobic N-terminus of dystrophin is accessible to antibody in situ. Quantitative binding studies suggested minor differences in specificity between the two mAbs, so the Ig heavy-chain variable region (VH) sequences of the two hybridomas were determined by RT-PCR and cDNA sequencing. After elimination of PCR errors, the two cDNA sequences were found to be identical except for five somatic mutations which resulted in three amino acid changes in the second hypervariable region (CDR2). The results suggest that the two hybridomas originated from the same lymphocyte clone in a germinal centre of the spleen, but underwent different point mutations and subtype switches during clonal expansion to form blast cells.

Mimics of the binding sites of opioid receptors obtained by molecular imprinting of enkephalin and morphine

Molecular imprinting of morphine and the endogenous neuropeptide [Leu5]enkephalin (Leu-enkephalin) in methacrylic acid-ethylene glycol dimethacrylate copolymers is described. Such molecular imprints possess the capacity to mimic the binding activity of opioid receptors. The recognition properties of the resultant imprints were analyzed by radioactive ligand binding analysis. We demonstrate that imprinted polymers also show high binding affinity and selectivity in aqueous buffers. This is a major breakthrough for molecular imprinting technology, since the binding reaction occurs under conditions relevant to biological systems. The antimorphine imprints showed high binding affinity for morphine, with Kd values as low as 10(-7) M, and levels of selectivity similar to those of antibodies. Preparation of imprints against Leu-enkephalin was greatly facilitated by the use of the anilide derivative rather than the free peptide as the print molecule, due to improved solubility in the polymerization mixture. Free Leu-enkephalin was efficiently recognized by this polymer (Kd values as low as 10(-7) M were observed). Four tetra- and pentapeptides, with unrelated amino acid sequences, were not bound. The imprints showed only weak affinity for two D-amino acid-containing analogues of Leu-enkephalin. Enantioselective recognition of the L-enantiomer of phenylalanylglycine anilide, a truncated analogue of the N-terminal end of enkephalin, was observed.