Site-Specific Glycan-Masking/Unmasking Hemagglutinin Antigen Design to Elicit Broadly Neutralizing and Stem-Binding Antibodies Against Highly Pathogenic Avian Influenza H5N1 Virus Infections.

Ting-Hsuan Chen,Suh-Chin Wu,Jia-Tsrong Jan,Chung-Chu Chen,Ya-Lin Yang

doi:10.3389/fimmu.2021.692700

Abstract

The highly pathogenic avian influenza (HPAI) H5N1 viruses with the capability of transmission from birds to humans have a serious impact on public health. To date, HPAI H5N1 viruses have evolved into ten antigenically distinct clades that could cause a mismatch of vaccine strains and reduce vaccine efficacy. In this study, the glycan masking and unmasking strategies on hemagglutinin antigen were used for designing two antigens: H5-dm/st2 and H5-tm/st2, and investigated for their elicited immunity using two-dose recombinant H5 (rH5) immunization and a first-dose adenovirus vector prime, followed by a second-dose rH5 protein booster immunization. The H5-dm/st2 antigen was found to elicit broadly neutralizing antibodies against different H5N1 clade/subclade viruses, as well as more stem-binding antibodies to inhibit HA-facilitated membrane fusion activity. Mice immunized with the H5-dm/st2 antigen had a higher survival rate when challenged with homologous and heterologous clades of H5N1 viruses. Mutant influenza virus replaced with the H5-dm/st2 gene generated by reverse genetics (RG) technology amplified well in MDCK cells and embryonated chicken eggs. Again, the inactivated H5N1-dm/st2 RG virus elicited more potent cross-clade neutralizing and anti-fusion antibodies in sera. Therefore, the H5N1-dm/st2 RG virus with the site-specific glycan-masking on the globular head and the glycan-unmasking on the stem region of H5 antigen can be used for further development of cross-protective H5N1 vaccines.

Highlights

Pathogenic avian influenza (HPAI) H5N1 viruses, which are transmitted from birds to humans, have a serious impact on public health [1,2,3]
These purified H5 proteins were tested for red blood cell (RBC) hemagglutination, and the results indicated that recombinant H5 (rH5)-dm/st2 had an approximately 3-log increase in red blood cells (RBC) hemagglutination compared to that of rH5-wt and no hemagglutination for rH5-tm/st2 (Figure 1C)
In this study we investigated two antigen designs combining glycan-masking and glycan unmasking H5 (H5-dm/st2 and H5-tm/st2) using three types of immunization regimens: (i) two-dose protein immunization, (ii) adenovirus vector priming, followed by rH5

Summary

Introduction

Pathogenic avian influenza (HPAI) H5N1 viruses, which are transmitted from birds to humans, have a serious impact on public health [1,2,3]. Phylogenic analysis of H5 hemagglutinin (HA) revealed that HPAI H5N1 viruses have evolved into ten antigenically distinct clades that may cause antigenic mismatches for selecting the vaccine strain(s) [5, 6]. No vaccine strains have been shown to elicit cross-protective immunity against a wide range of H5N1 clades and subclades [7, 8]. The World Health Organization (WHO) has recommended 32 candidate vaccine viruses of H5N1 virus clades/subclades for vaccine preparation [9]. The development of broadly protective H5N1 vaccines is of particular interest to control these distinct antigenic H5N1 clade/subclade virus infections

Methods

Results

Conclusion