Direct DNA immunization of mice with plasmid DNA encoding the tegument protein pp65 (ppUL83) of human cytomegalovirus induces high levels of circulating antibody to the encoded protein.

The 65 kDa tegument protein (pp65 or rather ppUL83) of human cytomegalovirus (HCMV) has been shown to be a major cytotoxic T-lymphocyte target during natural infection, and thus appears to be an appropriate candidate to be evaluated as a component of a HCMV polynucleotide vaccine. We have constructed expression vectors pH beta-pp65, in which pp65 expression is under the control of human beta-actin promoter, and pCMVint-pp65, in which pp65 expression is driven by the HCMV immediate-early promoter along with the intron A. These construct DNAs were utilized for the intramuscular injection into the quadriceps of BALB/c mice. Approximately 60% of the mice showed the presence of anti-pp65 antibodies following the second DNA inoculation with 100 micrograms of plasmid DNA. The anti-pp65 antibody titer was higher in the group of mice that was injected with pCMVint-pp65 plasmid DNA compared to the group that was injected with pH beta-pp65 DNA, presumably due to a higher level of pp65 expression using the former plasmid.