Construction and characterization of chimeric and humanized forms of a broadly neutralizing monoclonal antibody to HIV-1.

Murine monoclonal antibody (MAb) G3-5J9 has been shown to recognize a conserved neutralizing epitope in the fourth constant (C4) region of the external glycoprotein gpJ20 of HIV-J. Inasmuch as this antibody effectively neutralized the infectivity of diverse HIV-J isolates, it has been selected to be developedfor passive immunization against HIV-J infection in humans. In order to minimize the problem of immunogenicity of murine antibodies and to confer additional accessory immune functions, we have constructed mouse/human chimeric and humanized forms of the antibody. The chimeric antibody was constructed by cloning the murine variable regions and replacing the mouse constant regions with those from human IgyJ,K. The humanized antibody was constructed using the human KAS variable region framework sequences as template. Engineering was guided by a three dimensional model of the murine variable region. The murine, chimeric and humanized forms of the antibody exhibited similar reactivity with the peptidic antigen in ELISA, and comparably neutralized the infectivity of HIV-J in vitro. Taken together, our results show that the chimeric and humanized forms of G3-5J9 essentially retain the binding activity of the mouse parental antibody. Clinical development is planned to assess the prophylactic and therapeutic usefulness of these reshaped antibodies in humans. [Hum Antibod Hybridomas J994; 5: 9-17}