Peptides from heptad repeat (HR1 and HR2) regions of gp41 are effective inhibitors of HIV-1 entry that block the fusion of viral and cellular membranes, but the generation of antibodies highly specific for these peptides is challenging. We have previously described a mouse hybridoma that recognizes MT-C34-related peptides derived from HR2. It was used for the selection of HIV-1-resistant CD4 lymphocytes engineered to express the MT-C34 peptide via a CRISPR/Cas9-mediated knock-in into the CXCR4 locus. In this study, we cloned variable domains of this antibody and generated a recombinant chimeric antibody (chAb) by combining it with the constant regions of the humanized antibody Trastuzumab. The new chAb displayed a high specificity and two-fold higher level of affinity than the parental mouse monoclonal antibody. In addition, chAb mediated up to 27–43% of the antibody-dependent cellular cytotoxicity towards cells expressing MT-C34 on their surface. The anti-MT-C34 chAb can be easily generated using plasmids available for the research community and can serve as a valuable tool for the detection, purification, and even subsequent elimination of HIV-1-resistant CD4 cells or CAR cells engineered to fight HIV-1 infection.

The vertebrate transcription factor Kaiso binds specifically to methylated DNA sequences using C2H2-type zinc fingers. In addition to C2H2-domains, the BTB/POZ domain, which forms homodimers, is located at the N-terminus of Kaiso. Kaiso, like several other well-studied BTB/POZ proteins, including BCL6, interacts with the NCoR (nuclear co-repressor) protein, which determines the landing of transcriptional repressive complexes on chromatin. Using the yeast two-hybrid system, we have shown that the N-terminal domain of NCoR interacts with the C-terminal zinc fingers of Kaiso, and not with its BTB/POZ domain, as previously assumed. The results obtained demonstrate that NCoR interacts with various transcription factor domains, which can increase the efficiency of attracting NCoR-dependent repressor complexes to regulatory regions of the genome.