Virolysis and in vitro neutralization of HIV-1 by humanized monoclonal antibody hNM-01

Antibody humanization by transplanting the complimentarity determining regi on (CDR) to a human framework aims to reduce the response of the human immu ne system against a foreign molecule during passive immunization. We transf erred the CDR from the murine monoclonal antibody (MAb) NM-01 to a human Ig G frame. The humanized NM-01 (hNM-01) recognizes the same epitope on Human Immunodeficiency Virus type 1 (HIV-1) envelope as its murine progenitor, bu t with greater efficiency, and shows enhanced neutralization of HIV-1. We h ave shown that this increase in reactivity may be attributed to residue 4 o f the humanized kappa chain, where the presence of a methionine residue rat her than the murine leucine appears to promote a more advantageous conforma tion of the antigen-binding site, perhaps via packing interactions with the V-kappa CDR1. The capacity of humanized NM-01 to neutralize direct clinica l isolates was also examined with the expectation that hNM-01 will prove su itable for development as a therapeutic agent. This reshaped antibody react ed with several clinical isolates of HIV-1 tested. Moreover, we proved the ability of this antibody of its activation of complement by flow cytometry and electron microscopy analysis. Although hNM-01 alone was capable of neut ralizing HIV-1, the presence of complement enhanced neutralization. The enh ancement of complement activation was also observed in hNM-01 than murine p rogenitor. This finding supports a potential role for antibody-dependent co mplement-mediated virolysis and more effective neutralization in HIV-1 ther apy.