Antigenicity and immunogenicity of differentially glycosylated HCV E2 envelope proteins expressed in mammalian and insect cells

Urbanowicz, Richard A.; Wang, Ruixue; Schiel, John E.; Keck, Zhen-yong; Kerzic, Melissa C.; Lau, Patrick; Rangarajan, Sneha; Garagusi, Kyle J.; Tan, Lei; Guest, Johnathan D.; Ball, Jonathan K.; Pierce, Brian G.; Mariuzza, Roy A.; Foung, Steven K. H.; Fuerst, Thomas R.

Abstract

Development of a prophylactic vaccine for hepatitis C virus (HCV) remains a global health challenge. Cumulative evidence supports the importance of antibodies targeting the HCV E2 envelope glycoprotein to facilitate viral clearance. However, a significant challenge for a B cell-based vaccine is focusing the immune response on conserved E2 epitopes capable of eliciting neutralizing antibodies not associated with viral escape. We hypothesized that glycosylation might influence the antigenicity and immunogenicity of E2. Accordingly, we performed head-to-head molecular, antigenic and immunogenic comparisons of soluble E2 (sE2) produced in (i) mammalian (HEK293) cells, which confer mostly complex and high mannose type glycans; and (ii) insect (Sf9) cells, which impart mainly paucimannose type glycans. Mass spectrometry demonstrated that all 11 predicted N-glycosylation sites were utilized in both HEK293- and Sf9-derived sE2, but that N-glycans in insect sE2 were on average smaller and less complex. Both proteins bound CD81 and were recognized by conformation-dependent antibodies. Mouse immunogenicity studies revealed that similar polyclonal antibody responses were generated against antigenic domains A–E of E2. Although neutralizing antibody titers showed that Sf9-derived sE2 induced moderately stronger responses than HEK293-derived sE2 against the homologous HCV H77c isolate, the two proteins elicited comparable neutralization titers against heterologous isolates. Given that global alteration of HCV E2 glycosylation by expression in different hosts did not appreciably affect antigenicity or overall immunogenicity, a more productive approach to increasing the antibody response to neutralizing epitopes may be complete deletion, rather than just modification, of specific N-glycans proximal to these epitopes.

Citation

Urbanowicz, R. A., Wang, R., Schiel, J. E., Keck, Z., Kerzic, M. C., Lau, P., …Fuerst, T. R. (2019). Antigenicity and immunogenicity of differentially glycosylated HCV E2 envelope proteins expressed in mammalian and insect cells. Journal of Virology, 93(7), https://doi.org/10.1128/jvi.01403-18

• Journal Article Type: Article
• Acceptance Date: Dec 20, 2018
• Online Publication Date: Jan 16, 2019
• Publication Date: Jan 16, 2019
• Deposit Date: Jan 25, 2019
• Publicly Available Date: Jan 25, 2019
• Journal: Journal of Virology
• Print ISSN: 0022-538X
• Electronic ISSN: 1098-5514
• Publisher: American Society for Microbiology
• Peer Reviewed: Peer Reviewed
• Volume: 93
• Issue: 7
• DOI: https://doi.org/10.1128/jvi.01403-18
• Keywords: Immunology; Insect Science; Microbiology; Virology
• Public URL: https://nottingham-repository.worktribe.com/output/1496837
• Publisher URL: https://jvi.asm.org/content/early/2019/01/10/JVI.01403-18