The unmutated common ancestor of Gp41 conformational epitope targeting variable heavy chain 1-02 utilizing antibodies maintains antibody dependent cell cytotoxicity

In studies on monoclonal Abs (mAbs) from long-term non-progressors (LTNPs), our laboratory has previously described highly mutated Abs against a complex conformational epitope with contributions from both gp41 heptad repeat regions. Despite using the VH1-02 gene segment, known to contribute to some of the broadest neutralizing Abs against HIV, members of these Abs, termed group 76C Abs, did not exhibit broad neutralization.<br />Because of the excessive mutations and use of VH1-02, our goal was to characterize the non-neutralizing functions of Abs of group 76C, to assess targeting of the epitope in various clinical presentations, and to assess the development of these Abs by comparison to their predicted common ancestor. Serum competition assays showed group 76C Abs were enriched in LTNPs, in comparison to VRC-01. Specific group 76C clones 6F5 and 6F11, expressed as recombinant Abs, both have robust ADCC activity, despite their sequence disparity. Sequence analysis predicted the common ancestor of this clonal group would utilize the germline non-mutated variable gene. We produced a recombinant ancestor Ab (76Canc) with a heavy chain utilizing the germline variable gene sequence paired to the 6F5 light chain. Competition with group 76C recombinant Ab 6F5 confirms 76Canc binds HIV envelope constructs near the original group C epitope. 76Canc demonstrates comparable ADCC to 6F5 and 6F11 when targeting both clade B and C HIV constructs. The functional capability of Abs utilizing germline VH1-02 has implications for disease control and vaccine development.