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. 2022 Oct 9;10(10):1683.
doi: 10.3390/vaccines10101683.

AddaVax-Adjuvanted H5N8 Inactivated Vaccine Induces Robust Humoral Immune Response against Different Clades of H5 Viruses

Feixia Gao  1 , Xueying Liu  1 , Yudong Dang  1 , Peng Duan  1 , Wenting Xu  1 , Xin Zhang  1 , Shilei Wang  1 , Jian Luo  1 , Xiuling Li  1
Affiliations

AddaVax-Adjuvanted H5N8 Inactivated Vaccine Induces Robust Humoral Immune Response against Different Clades of H5 Viruses

Feixia Gao et al. Vaccines (Basel). .

Abstract

Since some cases of human infections with H5N8 avian influenza virus have been reported and caused great concern in recent years, it is important to develop an effective vaccine for human use to prevent a potential H5N8 pandemic. In the present study, a vaccine candidate virus based on newly human-infected A/Astrakhan/3212/2020 H5N8 virus was constructed by reverse genetics (RG) technology. The immunogenicity of H5N8 whole virion inactivated vaccine was evaluated by various doses of vaccine antigen formulated with squalene-based adjuvant (AddaVax), aluminum hydroxide (Al(OH)3) or without adjuvant in mice. The results showed AddaVax-adjuvanted H5N8 inactivated vaccine could stimulate the mice to produce a stronger protective immune response with higher titers of IgG antibodies, hemagglutination inhibition (HI), neuraminidase inhibition (NI) and microneutralization (MN) antibodies than vaccine formulations with Al(OH)3 adjuvant or without adjuvant, and achieve a dose-sparing effect. Moreover, the AddaVax-adjuvanted formulation also exhibited potent cross-reactive response in HI antibodies against different clades of H5 viruses. A significant correlation and a curve fitting among HI, NI and MN were found by the correlation analysis to predict the protective effect of the vaccine. With these findings, our study demonstrates that AddaVax adjuvant can enhance the immunogenicity of H5N8 inactivated vaccine remarkably, and proposes an effective strategy for dealing with a potential H5N8 virus pandemic.

Keywords: AddaVax; H5N8 vaccine; hemagglutination inhibition; immunogenicity; microneutralization; neuraminidase inhibition.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Characterization and identification of the inactivated whole-virus vaccine. (A) The electron micrograph of H5N8 inactivated whole viruses. (B) SDS-PAGE analysis of 3μg total protein in H5N8 virus vaccines with or without PNGase F treating (1:50 or 1:100 ratio). Purified HA protein of indicated amount was loaded to calibrate the HA content; the gel was stained with colloidal blue; images of SDS-PAGE were acquired by Bio-RAD software (ChemiDoc XRS+, 1708265). Each sample was tested in triplicate.
Figure 2
Figure 2
Humoral immune response elicited by H5N8 inactivated vaccine with or without adjuvants. BALB/c mice (n = 5) were immunized twice with various doses of H5N8 inactivated vaccines with or without adjuvants. The titers of virus specific IgG were detected by ELISA at day 21 post the first or last immunization. An amount of 2 μg/mL of H5N8 inactivated vaccine was used for plate coating. Comparing the vaccination effect among various formulations, an asterisk * indicates a significant difference (p < 0.05) detected by one-way ANOVA.
Figure 3
Figure 3
HI titers elicited by H5N8 inactivated vaccine with or without adjuvants. BALB/c mice (n = 5) were immunized twice with various doses of H5N8 inactivated vaccines with or without adjuvants, or with PBS as a control. (A) Serum HI antibodies against H5N8 virus at day 21 post the first immunization were determined by HI assay. (B) Serum HI antibodies against H5N8 virus at day 21 post the last immunization were determined by HI assay. Comparing the vaccination effect among various formulations, the asterisk * indicates a significant difference (p < 0.05) detected by one-way ANOVA.
Figure 4
Figure 4
MN and NI titers elicited by H5N8 inactivated vaccine with or without adjuvants. BALB/c mice (n = 5) were immunized twice with various doses of H5N8 inactivated vaccines with or without adjuvants. (A) The MN titers against H5N8 virus in serum were analyzed by MN assay at day 21 post the last immunization. (B) The NI titers against H5N8 virus in serum were analyzed by NI assay at day 21 post the last immunization. The H5N8 whole-virus inactivated vaccine acted as the source of antigen. Comparing the vaccination effect among various formulations, an asterisk * indicates a significant difference (p < 0.05), by one-way ANOVA.
Figure 5
Figure 5
Cross-reactive neutralizing antibody against different clades of H5 viruses. Cross-reactive neutralizing antibody responses were determined by HI assay. (A) Antisera were analyzed for HI titers against H5N1 virus. (B) Antisera were analyzed for HI titers against H5N6 virus. Comparing the vaccination effect among various formulations, an asterisk * indicates a significant difference (p < 0.05) detected by one-way ANOVA.
Figure 6
Figure 6
Correlation analysis among different antibody titers at day 21 post the last immunization. Correlation among HI/NI/MN antibody titers using the fitted curves. R2 indicates the goodness of the fit.
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