Vaccinia virus as a tool for immunologic studies.

Studies that involve antigen processing and presentation often require de novo biosynthesis of the antigen both in vitro and in vivo. Additionally, biosynthesis of the antigen or engineered variants within the antigen-presenting cells is usually simpler than providing purified recombinant proteins from bacteria, yeast, or insect cells. For these purposes, recombinant vaccinia virus-based expression has several advantages over other expression systems employed in the field. Insertion of large pieces of recombinant DNA into the vaccinia virus genome, easy recombination and selection of vaccinia viruses, and the ability of these viruses to infect a variety of cells are some key aspects that have made this system popular. Although their efficacy is proven in studies of major histocompatibility complex (MHC) class I-restricted antigen processing and presentation, it is challenging to use them in MHC class II-restricted antigen processing and presentation owing to many reasons specified in this chapter. This chapter aims to describe the commonly used procedures in this field that employ vaccinia virus systems, particularly troubleshooting common problems encountered during experiments.