Models of RNA virus evolution and their roles in vaccine design

Ojosnegros, Samuel; Beerenwinkel, Niko

Inactivated vaccines (IVs). Viral stocks are susceptible to inactivation by some chemical and physical treatments. IVs consist of a concentrated viral stock that has been treated with a chemical reagent, such as binary ethylenimine or formaldehyde, which completely abolish virus replication [40] . Some viruses are difficult to attenuate because they may change their antigenic properties or they remain virulent after few passages in cell culture [41] . The latter is the case for FMDV, an animal virus from the picornavirus family. When a virus cannot be attenuated with sufficient reliability, inactivation has been proven to be a successful vaccination strategy, as documented for FMDV, influenza, or hepatitis A vaccines [41] [42] [43] [44] . Some security issues may arise however, if the chemical compound does not reach all virus particles, for example because some viral particles tend to form compact aggregates, and the preparation still contains a portion of live viruses. Inactivated viruses are usually not efficiently presented by MHC class I molecules, which stimulate the cellular immune response. IV preparations include adjuvants which are chemical compounds that act on antigen-presenting cells enhancing the immunogenicity of the vaccine [45, 46] . However, the strength and duration of the protection induced by IVs is usually lower than that obtained with LAVs.