Immunization against flu viruses is an established prophylactic tool against the life-threatening disease. However, the development of effective and universal vaccines remains a challenging area.
Most influenza vaccines, such as the annual flu shot, contain viral antigens, which are specific to one or several subtypes of influenza, but no live or inactivated virus particles. Unfortunately, flu viruses have the advantage of changing their antigens extremely quickly, and the resulting seasonal variation of subtypes prevents scientists from creating a universal vaccine.
A new study published at PLOS One describes a possible straightforward methodology for creating whole inactivated vaccines using high hydrostatic pressure (HPP) inactivation of flu viruses.
HHP, or pascalization, is a conventional technique for sterilizing processed food products, such as milk, juice, canned foods etc. The same methodology has been successfully used for inactivation of a number of viruses, including yellow fever virus, avian influenza viruses, Hepatitis A virus and others, and has influenced the overall understanding of viruses significantly. Inactivation by HHP has an advantage of maintaining a relatively unaffected collection of viral antigens, as well as exposing some internal antigens, which would otherwise be unavailable for the immune system. In this way, body’s defenses could tackle more universal, rather than subtype-specific viral antigens.
Inactivation of influenza with hydrostatic pressure proved to cause minimal structural changes within the virus, however the infectious capacity was lost completely, and immunized mice did not show any symptoms. Moreover, inactivated viruses were demonstrated to develop pores in their envelope, thus leaving their internal antigens susceptible to immune attack.
This way the whole virus vaccine could promote more universal immunity to influenza, and remain effective against multiple seasonal variants.
While proven effective in mice, the method requires further investigation concerning dosage, virulence and immunogenicity of the vaccine in humans. However, the HHP inactivation offers a simple, fast and cost-effective method for vaccine development, and since WIVs are more effective than split virus or antigen-containing vaccines, it could become a compelling alternative for conventional influenza vaccines.