Modern Approaches to Live Virus Vaccines

Abstract

This chapter discusses the different approaches to the development of live virus vaccines. Virus vaccines can mobilize all the different arms of the immune system. Furthermore, when the primary replication of vaccine virus occurs in a mucosal membrane, attractive conditions for establishment of a local immunity are obtained. This appreciation has given the incentive for development of live vaccines to protect against local infections in the respiratory and enteric tracts. There are certain situations that would seem less amenable for the exploitation of the use of live vaccines. This is the case when the vaccine virus genome can integrate into cellular genomes, possibly leading to alterations in the properties of cells. This applies to infections with, for example, herpesviruses and retroviruses. There are three different approaches to the identification of attenuated virus that can be considered for use in the development of live vaccines: spontaneously occurring attenuated virus strains, experimentally produced or selected attenuated virus variants with genomic point mutations, deletions or insertions, and attenuation by formation of chimeric constructs of different types or strains of picornaviruses.