Full Inactivation of Human Influenza Virus by High Hydrostatic Pressure Preserves Virus Structure and Membrane Fusion While Conferring Protection to Mice against Infection

Abstract

Whole inactivated vaccines (WIVs) possess greater immunogenicity than split or subunit vaccines, and recent studies have demonstrated that WIVs with preserved fusogenic activity are more protective than non-fusogenic WIVs. In this work, we describe the inactivation of human influenza virus X-31 by high hydrostatic pressure (HHP) and analyze the effects on the structure by spectroscopic measurements, light scattering, and electron microscopy. We also investigated the effects of HHP on the glycoprotein activity and fusogenic activity of the viral particles. The electron microscopy data showed pore formation on the viral envelope, but the general morphology was preserved, and small variations were seen in the particle structure. The activity of hemagglutinin (HA) during the process of binding and fusion was affected in a time-dependent manner, but neuraminidase (NA) activity was not affected. Infectious activity ceased after 3 hours of pressurization, and mice were protected from infection after being vaccinated. Our results revealed full viral inactivation with overall preservation of viral structure and maintenance of fusogenic activity, thereby conferring protection against infection. A strong response consisting of serum immunoglobulin IgG1, IgG2a, and serum and mucosal IgA was also detected after vaccination. Thus, our data strongly suggest that applying hydrostatic pressure may be an effective method for developing new vaccines against influenza A as well as other viruses.

Intranasal Immunization with Pressure Inactivated Avian Influenza Elicits Cellular and Humoral Responses in Mice

“…It was also demonstrated that the pressurized particles were capable of fusing with the cell membrane but unable to cause an infection [ 43 ]. More recently, our group showed similar results with the human H3N2 influenza virus [ 44 ]. These previous studies indicate that the inactivation by pressure preserves, even partially, the viral structure because the virus is able to bind to the target cell but is unable to enter the replication cycle [ 45 ].…”

Inactivation of avian influenza viruses by hydrostatic pressure as a potential vaccine development approach

“…On the other hand, the fact that haemagglutination was impaired by pressurization agrees with other results previously reported for other subtypes of influenza A viruses (H3N2) [49] and H3N8 [50] suggests that the virus-binding activity promoted by HA is primordial for the virus infectious process. The long period of pressurization required for full inactivation of the influenza viruses agrees with findings reported by Silva et al [39], revealing that this procedure was also crucial to achieve the full inactivation of another enveloped virus as VSV.…”

“…Studies with pressure-inactivated particles of yellow fever virus [44], infectious bursal disease virus [22], vesicular stomatitis virus (VSV) [35], simian and bovine rotavirus [23] and human influenza virus [49, 50] demonstrate that they maintain their immunogenic properties as native particles. These interesting findings have generated the idea of applying hydrostatic pressure to prepare virus vaccines with high efficiency and safety.…”

Aspects of high hydrostatic pressure food processing: Perspectives on technology and food safety

“…The distinct mechanisms of virus inactivation by HHP are not completely known so far. A destruction or deformation of the viral capsid was demonstrated after HHP, which eliminated virus infectivity, whereas the antigenicity of the virus was largely maintained (Dumard et al., 2013; Lou et al., 2011). In contrast, the virus genome was obviously not, or only slightly damaged after HHP treatment (Lou et al., 2011; Sánchez et al., 2011).…”