In March 2013, the Chinese Centre for Disease Control and Prevention confirmed the first reported case of human
infection with an
avian influenza A H7N9 virus.
Infection with this virus often caused severe
pneumonia and
acute respiratory distress syndrome resulting in a case fatality rate >35%. The risk of pandemic highlighted, once again, the need for a more rapid and scalable
vaccine response capability. Here, we describe the rapid (19 days) development of a plant-derived VLP
vaccine based on the
hemagglutinin sequence of
influenza H7N9 A/Hangzhou/1/2013. The immunogenicity of the H7 VLP
vaccine was assessed in mice and ferrets after one or two intramuscular dose(s) with and without adjuvant (
alum or GLA-SE™). In ferrets, we also measured H7-specific cell-mediated immunity. The mice and ferrets were then challenged with H7N9 A/Anhui/1/2013 influenza virus. A single immunization with the adjuvanted
vaccine elicited a strong humoral response and protected mice against an otherwise lethal challenge. Two doses of unadjuvanted
vaccine significantly increased humoral response and resulted in 100% protection with significant reduction of clinical signs leading to nearly
asymptomatic infections. In ferrets, a single immunization with the
alum-adjuvanted H7 VLP
vaccine induced strong humoral and CMI responses with
antigen-specific activation of CD3(+) T cells. Compared to animals injected with placebo, ferrets vaccinated with
alum-adjuvanted
vaccine displayed no
weight loss during the challenge. Moreover, the vaccination significantly reduced the viral load in lungs and nasal washes 3 days after the
infection. This candidate plant-made H7
vaccine therefore induced protective responses after either one adjuvanted or two unadjuvanted doses. Studies are currently ongoing to better characterize the immune response elicited by the plant-derived VLP
vaccines. Regardless, these data are very promising for the rapid production of an immunogenic and protective
vaccine against this potentially pandemic virus.