Camelid Ig V genes reveal significant human homology not seen in therapeutic target genes, providing for a powerful therapeutic antibody platform

Abstract

de Haard & Ikbel Achour (2015) Camelid Ig V genes reveal significant human homology not seen in therapeutic target genes, providing for a powerful therapeutic antibody platform, mAbs, 7:4, 693-706, DOI: 10.1080/19420862.2015 To link to this article: https://doi.org/10. 1080/19420862.2015 Camelid immunoglobulin variable (IGV) regions were found homologous to their human counterparts; however, the germline V repertoires of camelid heavy and light chains are still incomplete and their therapeutic potential is only beginning to be appreciated. We therefore leveraged the publicly available HTG and WGS databases of Lama pacos and Camelus ferus to retrieve the germline repertoire of V genes using human IGV genes as reference. In addition, we amplified IGKV and IGLV genes to uncover the V germline repertoire of Lama glama and sequenced BAC clones covering part of the Lama pacos IGK and IGL loci. Our in silico analysis showed that camelid counterparts of all human IGKV and IGLV families and most IGHV families could be identified, based on canonical structure and sequence homology. Interestingly, this sequence homology seemed largely restricted to the Ig V genes and was far less apparent in other genes: 6 therapeutically relevant target genes differed significantly from their human orthologs. This contributed to efficient immunization of llamas with the human proteins CD70, MET, interleukin (IL)-1b and IL-6, resulting in large panels of functional antibodies. The in silico predicted human-homologous canonical folds of camelidderived antibodies were confirmed by X-ray crystallography solving the structure of 2 selected camelid anti-CD70 and anti-MET antibodies. These antibodies showed identical fold combinations as found in the corresponding human germline V families, yielding binding site structures closely similar to those occurring in human antibodies. In conclusion, our results indicate that active immunization of camelids can be a powerful therapeutic antibody platform.

The Therapeutic Potential of Nanobodies

“…The sequence identity between nanobodies and the V H of human immunoglobulins of family III is above 80% [59]. In their extensive analysis, Klarenbeek et al assessed the homology between the camelid germline IgV gene repertoire and their human counterparts and found 95% sequence identity of the camelid IGHV family 3 with its human FR counterpart [60]. This means that nanobodies will have a low immunogenic profile and are thus suitable for human administration [61].…”

Antibody Structure and Function: The Basis for Engineering Therapeutics

“…Recently, Caplacizumab (ALX-0081), an anti-von Willebrand factor humanized VHH, was launched in 2018 for the treatment of thrombotic thrombocytopenic purpura and thrombosis [303]. Since in silico analysis showed that camelid VHH sequences could be aligned to human IGKV and IGLV families based on canonical structure and sequence homology, optimization of primary sequence is possible to minimize the potential of the development of anti-drug antibodies (ADAs) [304].…”

Antigen recognition by single-domain antibodies: structural latitudes and constraints

“…The CDR1 and CDR2 loops of V H Hs depart from the typical canonical structures of conventional antibodies (Figure 2A), potentially through somatic mutation since germline human V H and camelid V H H repertoires appear to have similar canonical structures. 18 Only a handful of V NAR s have been crystallized, and several showed a structural class of CDR1 (H1-13–9) that is more common in V H Hs than in conventional antibodies, although others had CDR1 canonical structures closer to those of V L domains. The CDR3 length distributions of both V H Hs and V NAR s (Figure 2B) are broader than those of conventional antibodies and biased towards longer lengths; the long CDR loops of sdAbs may be structurally constrained by non-canonical disulfide linkages (see Box 2).…”