Cytolytic T lymphocyte recognition of the murine cytomegalovirus nonstructural immediate-early protein pp89 expressed by recombinant vaccinia virus

The murine immediate-early (IE) protein pp89 is a nonstructural
virus- encoded phosphoprotein residing in the nucleus of infected
cells, where it acts as transcriptional activator. Frequency
analysis has shown that in BALB/c mice the majority of
virus-specific CTL recognize IE antigens. The present study was
performed to assess whether pp89 causes membrane antigen expression
detected by IE-specific CTL. Site-directed mutagenesis has been
used to delete the introns from gene ieI, encoding pp89, for
subsequent integration of the continuous coding sequence into the
vaccinia virus genome. After infection with the vaccinia
recombinant, the authentic pp89 was expressed in cells that became
susceptible to lysis by an IE-specific CTL clone. Priming of mice
with the vaccinia recombinant sensitized polyclonal CTL that
recognized MCMV- infected cells and transfected cells expressing
pp89. Thus, a herpesviral IE polypeptide with essential function in
viral transcriptional regulation can also serve as a dominant
antigen for the specific CTL response of the host.