Vaccine potential of a murine gammaherpesvirus-68 mutant deficient for ORF73.

A murine gammaherpesvirus (MHV-68) containing a deletion of the putative plasmid maintenance protein ORF73 exhibits a severe latency deficit. In this study the ability of an ORF73 deletion mutant (Delta73) to confer in vivo protection against subsequent challenge with wild-type virus has been examined. Vaccination studies have shown that Delta73 vaccination reduced latent infection of wild-type challenge virus to a level below the limit of detection. These results indicate that a live-attenuated gammaherpesvirus that cannot persist is an effective vaccine.