Abstract
A novel avian influenza subtype, A/H7N9, emerged in 2013 and represents a public health threat with pandemic potential. We have previously shown that DNA vaccine priming increases the magnitude and quality of antibody responses to H5N1 monovalent inactivated boost. We now report the safety and immunogenicity of a H7 DNA-H7N9 monovalent inactivated vaccine prime-boost regimen. In this Phase 1, open label, randomized clinical trial, we evaluated three H7N9 vaccination regimens in healthy adults, with a prime-boost interval of 16 weeks. Group 1 received H7 DNA vaccine prime and H7N9 monovalent inactivated vaccine boost. Group 2 received H7 DNA and H7N9 monovalent inactivated vaccine as a prime and H7N9 monovalent inactivated vaccine as a boost. Group 3 received H7N9 monovalent inactivated vaccine in a homologous prime-boost regimen. Overall, 30 individuals between 20 to 60 years old enrolled and 28 completed both vaccinations. All injections were well tolerated with no serious adverse events. 2 weeks post-boost, 50% of Group 1 and 33% of Group 2 achieved a HAI titer ≥1:40 compared with 11% of Group 3. Also, at least a fourfold increase in neutralizing antibody responses was seen in 90% of Group 1, 100% of Group 2, and 78% of Group 3 subjects. Peak neutralizing antibody geometric mean titers were significantly greater for Group 1 (GMT = 440.61, p < 0.05) and Group 2 (GMT = 331, p = 0.02) when compared with Group 3 (GMT = 86.11). A novel H7 DNA vaccine was safe, well-tolerated, and immunogenic when boosted with H7N9 monovalent inactivated vaccine, while priming for higher HAI and neutralizing antibody titers than H7N9 monovalent inactivated vaccine alone.
Highlights
In February 2013, a novel avian influenza subtype, A/H7N9, appeared in China resulting in severe lower respiratory tract infections in humans.[1]
We evaluated the ability of this prime-boost regimen to improve hemagglutinin 7 (H7)-specific hemagglutination inhibition (HAI) titers and neutralizing antibody responses
In group 3 (MIV prime-monovalent inactivated vaccine (MIV) boost), peak HAI GMT was maintained until 12 weeks post-boost, the titer was lower than both groups 1 and 2 (Fig. S1)
Summary
In February 2013, a novel avian influenza subtype, A/H7N9, appeared in China resulting in severe lower respiratory tract infections in humans.[1]. Pandemic influenza can arise from a reassortment event in which two or more influenza viruses exchange genetic material and/or via direct spread from animals to humans of an influenza virus that has adapted to spread in humans.[6, 7] While sustained human-to-human transmission of H7N9 has not been reported, several factors suggest H7N9 has pandemic potential. These include the absence of baseline immunity to H7N9 in humans;[3, 8] presence of genetic markers associated with human adaptation such as Q226L in the HA gene and an E627K substitution in PB2
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