Preparation and evaluation of Escherichia coli-derived glycoprotein E for development of a subunit vaccine against varicella-zoster virus.

Glycoprotein E (gE) of varicella-zoster virus (VZV) is a validated target for subunit vaccine development. However, gE produced in Chinese hamster ovary (CHO) cells is associated with high manufacturing costs and glycosylation-related heterogeneity. Here, the ectodomain of gE (aa 25-539) was expressed in Escherichia coli, yielding a monomeric, non-glycosylated gE ectodomain (n-gE) that was efficiently prepared and comprehensively characterized. To recover properly folded protein from inclusion bodies, a two-stage refolding strategy was established, in which disulfide bond formation was promoted in 7 M urea during the first stage, followed by recovery of the native monomeric conformation through dilution to 2 M urea in the second stage, achieving a refolding yield of up to 90%. Purified n-gE exhibited secondary and tertiary structures highly similar to those of CHO-derived glycoprotein E (CgE). Functionally, n-gE exhibited comparable recognition by VZV-positive sera and enhanced binding to the gE-specific neutralizing monoclonal antibody 7H12. Immunization studies in mice demonstrated that aluminum-adjuvanted n-gE elicited robust gE-specific IgG responses and strong T-cell activation. All these findings indicate that E. coli-derived non-glycosylated gE represents a promising and cost-effective alternative antigen for VZV subunit vaccine development.