Recombinant H7 hemagglutinin forms subviral particles that protect mice and ferrets from challenge with H7N9 influenza virus

Abstract

A novel avian-origin influenza A H7N9 virus emerged in China in 2013 and continues to cause sporadic human infections with mortality rates approaching 35%. Currently there are no approved human vaccines for H7N9 virus. Recombinant approaches including hemagglutinin (HA) and virus-like particles (VLPs) have resulted in experimental vaccines with advantageous safety and manufacturing characteristics. While high immunogenicity of VLP vaccines has been attributed to the native conformation of HA arranged in the regular repeated patterns within virus-like structures, there is limited data regarding molecular organization of HA within recombinant HA vaccine preparations. In this study, the full-length recombinant H7 protein (rH7) of A/Anhui/1/2013 (H7N9) virus was expressed in Sf9 cells. We showed that purified full-length rH7 retained functional ability to agglutinate red blood cells and formed oligomeric pleomorphic subviral particles (SVPs) of ~20 nm in diameter composed of approximately 10 HA0 molecules. No significant quantities of free monomeric HA0 were observed in rH7 preparation by size exclusion chromatography. Immunogenicity and protective efficacy of rH7 SVPs was confirmed in the mouse and ferret challenge models suggesting that SVPs can be used for vaccination against H7N9 virus.

Plant-derived H7 VLP vaccine elicits protective immune response against H7N9 influenza virus in mice and ferrets

“…However, mice immunized with two doses of the unadjuvanted baculovirus VLP vaccine still lost 10−15% of their initial body weight after challenge with 3.6 LD50 A/Anhui/1/2013. More recently, weight lost and partial (80%) protection after challenge with 10 LD50 A/Anhui/1/2013 was observed in mice vaccinated IN with two doses of 5 g of unadjuvanted recombinant baculovirus-origin H7 subviral particles 3 weeks apart [25].…”

Mono- and quadri-subtype virus-like particles (VLPs) containing H10 subtype elicit protective immunity to H10 influenza in a ferret challenge model

“…In some cases, retrovirus gag was used in place of M1 [15]. The HA antigen is the major vaccine component, which induces neutralizing antibodies preventing infectious virus from entering cells [4, 16, 17]. Expression within VLPs increases immunogenicity of the HA antigen [12, 18].…”

Recombinant Hemagglutinin and Virus-Like Particle Vaccines for H7N9 Influenza virus

“…A previous study has shown that purified rH3 HA forms rosette-shaped subviral particles (SVPs) of approximately 30–50 nm in diameter [66]. We recently prepared the full-length H7 rHA from A/Anhui/1/2013 (H7N9) using a modified purification conditions for rH7 HA [67]. Similarly to a previous study [40], we found that purified rHA is arranged into particulate structures, or subviral particles (SVP), with approximately 20 nm in diameter (Figure 4).…”

“…Thus, it is likely that formation of SVP mimics to some extent the conformational epitopes of the virus, which can explain the high immunogenicity of influenza rH7 HA. Recent data demonstrated that SVPs comprised of the full-length rHA from A/Anhui/1/2013 (H7N9) are immunogenic and protective in animal models [67]. …”