Hazard Characterization of Modified Vaccinia Virus Ankara Vector: What Are the Knowledge Gaps?

Okeke, Malachy I.; Okoli, Arinze S.; Diaz, Diana; Offor, Collins; Oludotun, Taiwo G.; Tryland, Morten; Bøhn, Thomas; Moens, Ugo

Persistence of viral particles and DNA in the environment can be affected by several factors (reviewed in [163] ), including the presence or absence of proteolytic microorganisms, lipid and protein materials serving as protective shields for the virus particles, pH and temperature (freeze-thaw cycles). Further, presence or absence of DNases, pH and the length of the DNA polymer may affect nucleic acid persistence. There is dearth of information on persistence of virus-vectored vaccine such as recombinant MVA outside the host although persistence in different materials of wild-type viruses commonly employed as vectors is available [163] . Thus, it is often assumed that persistence of GM viruses/vectors is not different from that of the wild-type strains. This ignores the fact that genetic manipulation may have affected some biological properties of the GM virus/vector resulting in a persistence that is different from the corresponding parental virus. An example is where inserted sequences can influence the genome stability of the viral vector, which can result in an improperly packaged, enlarged and unstable genome prone to re-arrangement.