Screening and identification of B-cell epitopes on the gH protein of varicella-zoster virus

Varicella and herpes zoster are two clinically distinct diseases caused by varicella-zoster virus (VZV). The VZV envelope is enriched with multiple glycoproteins, among which glycoprotein H (gH) is a key envelope glycoprotein essential for viral entry into host cells and an important target of neutralizing antibodies. However, precise mapping of key protective epitopes on the gH protein remains incomplete. VZV gL functions as a molecular chaperone for gH and promotes its proper expression. In this study, the extracellular-domain sequence of gH and the full-length sequence of gL were co-cloned into the pCGS3 vector, and the VZV gH/gL heterodimer with native conformation was successfully expressed using a eukaryotic expression system. Using this heterodimer as the immunogen, five monoclonal antibodies (mAbs) specifically recognizing gH were obtained. Through overlapping peptide truncation assays, the linear B-cell epitopes targeted by these five mAbs were mapped to two regions of the gH protein: ⁴³¹SQLHDELSLLFGQVK⁴⁴⁵ and ⁷⁷⁵SKAVLLFPNGTVVTL⁷⁸⁹, and alanine scanning mutagenesis further identified the key amino acid residues recognized by each mAb. This study successfully identified linear B-cell epitopes on the VZV gH protein at single-residue resolution, and both epitopes were completely conserved among 40 VZV strains. The two linear epitopes identified in this study provide valuable experimental materials for further dissecting the molecular mechanisms of the host anti-VZV immune response and lay a sequence foundation for subsequent optimization and design of epitope-based immunogens.