Specific HIV gp120-cleaving Antibodies Induced by Covalently Reactive Analog of gp120

Sudhir Paul, Stephanie Planque, Yong-Xin Zhou, Hiroaki Taguchi, Gita Bhatia, Sangeeta Karle, Carl Hanson, Yasuhiro Nishiyama
2003 Journal of Biological Chemistry  
We report the results of efforts to strengthen and direct the natural nucleophilic activity of antibodies (Abs) for the purpose of specific cleavage of the human immunodeficiency virus-1 coat protein gp120. Phosphonate diester groups previously reported to form a covalent bond with the active site nucleophile of serine proteases ) were placed on Lys side chains of gp120. Seven monoclonal Abs raised by immunization with the covalently reactive analog of gp120 displayed irreversible binding to
more » ... sible binding to this compound (binding resistant to dissociation with the denaturant SDS). Catalytic cleavage of biotinylated gp120 by three monoclonal antibodies was observed. No cleavage of albumin and the extracellular domain of the epidermal growth factor receptor was detected. Cleavage of model peptide substrates occurred on the C-terminal side of basic amino acids, and K m for this reaction was ϳ200-fold greater than that for gp120 cleavage, indicating Ab specialization for the gp120 substrate. A hapten phosphonate diester devoid of gp120 inhibited the catalytic activity with exceptional potency, confirming that the reaction proceeds via a serine protease mechanism. Irreversible binding of the hapten phosphonate diester by polyclonal IgG from mice immunized with gp120 covalently reactive analog was increased compared with similar preparations from animals immunized with control gp120, indicating induction of Ab nucleophilicity. These findings suggest the feasibility of raising antigen-specific proteolytic antibodies on demand by covalent immunization.
doi:10.1074/jbc.m300870200 pmid:12665517 fatcat:fealm6h5dnaopoqfvfx6czhfre