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. 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. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This research was supported through biorepository access by the University of Washington Center for AIDS Research (CFAR), an NIH funded program (P30 AI027757) which is supported by the following NIH Institutes and Centers (NIAID, NCI, NIMH, NIDA, NICHD, NHLBI, NIA). Study was primarily supported by NIH R01 AI 125119-01; "The role of non-broadly neutralizing antibodies targeting gp41 structural epitopes in long term nonprogression of HIV infection." ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Not Applicable The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Sample collection was done under approval from University at Buffalo State University of New York IRB ( UB IRB STUDY00000359). All necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived. Not Applicable I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Not Applicable I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Not Applicable All pertinent data is included in the manuscript. Raw data is available on request.