[34] Vaccinia virus as an expression vector

The chapter describes vaccinia virus as an expression vector. It describes the methodology for using vaccinia virus to express foreign genes. These recombinant vaccinia viruses can be used for several purposes:(1)understanding the genetic regulation involved in the expression of endogenous vaccinia functions, (2) determining the fate of foreign gene products in a background free of native influences, (3) producing biologically active molecules, (4) elucidating the roles of pertinent antigens in eliciting defined immunological responses, (5) producing live recombinant vaccines, and (6) potentially using gene replacement therapy. The chapter discusses the biology of poxviruses stating that they comprise a large group of complex animal viruses, whose genetic information is contained within a double-standed DNA molecule and whose replication is confined to the cytoplasm of the infected cell. The chapter describes the principle of the method regarding the general protocol for the insertion of foreign genes into vaccinia virus. Vaccinia displays a number of characteristics, which make it an ideal expression vector. Some of these are as follows:(1) the ability to incorporate large amounts of exogenous DNA, (2) the faithful transcription of the exogenous genes such that the RNAs are translated into protein, which resemble the native product in structure, function, and localization, (3) the cytoplasmic site of vaccinia replication, allowing gene expression to proceed without interference by the host genome, and (4) the potentiality as a live recombinant vaccine as a target against human and veterinary pathogens. The future research efforts will focus on the manipulation of the vaccinia genome with respect to defining the genetic parameters, which control the expression of both endogenous and exogenous genes.