ENGINEERING HUMAN MONOCLONAL-ANTIBODY FRAGMENTS - A RECOMBINANT ENZYME-LINKED FAB

A new plasmid vector, pCRP, allowing the expression of human recombina nt monoclonal antibody Fab fragments fused with a bacterial acid phosp hatase has been constructed. pCRP can accept heavy- and light-chain cD NAs cloned from combinatorial antibody libraries displayed on filament ous phages with the pCombIII system and is able to direct expression o f soluble Fabs in which the carboxy-terminus of the heavy chain is fus ed to the amino-terminus of the mature PhoN nonspecific acid phosphata se of Providencia stuartii. Using the pCRP vector, we expressed two di fferent human recombinant Fabs cloned from combinatorial libraries (on e anti-tetenus toroid and the other anti-HTV-1 gp120) fused with the a cid phosphatase. In both cases chimeric antibodies were obtained which retained the antigen-binding ability and the enzymatic acitivity. Sim ilar Fab-enzyme fusions can be successfully used, even unpurified, in enzyme immunoassays.