Infect Chemother.  2017 Jun;49(2):117-122. 10.3947/ic.2017.49.2.117.

Humoral and Cellular Immunogenicity Induced by Avian Influenza A (H7N9) DNA Vaccine in Mice

• Choi EJ
• Lee HS
• Noh JY
• Song JY
• Cheong HJ
• Shin OS
• Lee H
• Jeong M
• Kim WJ

• KMID: 2383932
• DOI: http://doi.org/10.3947/ic.2017.49.2.117

Abstract

BACKGROUND
In March 2013, human infection with avian influenza A (H7N9) virus emerged in China, causing serious public health concerns and raising the possibility of avian-source pandemic influenza. Thus, the development of an effective vaccine for preventing and rapidly controlling avian influenza A (H7N9) virus is needed. In this study, we evaluated the immunogenicity of a synthetic DNA vaccine against H7 HA antigens in mice.
MATERIALS AND METHODS
The synthetic consensus H7 HA DNA vaccine (25 or 50 µg) was administered to BALB/c mice at 0, 14, and 28 days by intramuscular injection followed by electroporation. Humoral and cellular immune responses were analyzed in a hemagglutination inhibition test and interferon-gamma enzyme-linked immunospot (ELISpot) assay, respectively.
RESULTS
H7 HA-vaccinated mice showed 100% seroprotection and seroconversion rate against H7N9 reassortant influenza virus after both second and third immunizations. The geometric mean titer by the hemagglutination inhibition test increased with an increasing number of immunizations. However, there was no significant difference in geometric titer between the two groups injected with 25 and 50 µg of H7 HA DNA vaccine after two (79.98 vs. 107.65, P = 0.39) and three (159.96 vs. 215.28, P = 0.18) doses. In addition, the ELISpot assay revealed that administration of H7 HA DNA vaccine induced potent interferon-gamma production from mouse splenocytes.
CONCLUSIONS
This study demonstrated the humoral and cellular immunogenicity of synthetic consensus H7 HA DNA vaccine in mice. This work demonstrates the potential of the H7 HA DNA vaccine as an efficient tool for the rapid control of emerging influenza A (H7N9) virus.

Keyword

Influenza A(H7N9) virus; DNA vaccine; Cellular immunity

MeSH Terms

Animals
China
Consensus
DNA*
Electroporation
Enzyme-Linked Immunospot Assay
Hemagglutination Inhibition Tests
Humans
Immunity, Cellular
Immunization
Influenza in Birds*
Influenza, Human
Injections, Intramuscular
Interferon-gamma
Mice*
Orthomyxoviridae
Pandemics
Public Health
Seroconversion
DNA
Interferon-gamma

Figure

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  Figure 1 Schema of the study design imm, immunization.

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  Figure 2 Induction of HA-specific humoral immune responses in mice immunized with H7 HA DNA vaccine BALB/c mice were immunized with vector (50 µg) or H7 HA DNA vaccine (25 or 50 µg) at one to three doses and blood was isolated 2 weeks after the last immunization. Seroprotection rate (A), seroconversion rate (B), and geometric mean titer (GMT) (C and D) against H7N9 reassortant influenza virus were determined by hemagglutination inhibition (HI) test. The values are the means ± standard error of the means. Experiments were performed in duplicate and the values are the means ± standard error of the means. GMT, geometric mean titer; CI, confidence interval

• 

  Figure 3 Induction of HA-specific cellular immune responses in mice immunized with H7 HA DNA vaccine. BALB/c mice were immunized with vector (50 µg) or H7 HA DNA vaccine (25 or 50 µg) at one to three doses and spleens were isolated 2 weeks after the last immunization. Mouse splenocytes were stimulated with H7 HA peptide pools for 16 h followed by IFN-γ ELISpot assay. IFN-γ production was determined by calculating the number of spot-forming cells per 1 × 106 splenocytes. Naïve mice (N) were used as a negative control. Experiments were performed in triplicate and the values are the means ± standard error of the means. SFU; spot-forming unit.

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