planned process TK from Equid herpesvirus Oliver He process Rebecca Racz A thymidine kinase-deficient mutant (PR1) is attenuated in mice and induced significant protection from challenge with wild type EHV-1 5 weeks after vaccination. In foals, PR1 also showed attenuation; however, the mutant induced only partial protection from challenge with EHV-1 NCBI_Protein_ID: 59214; PMID: 16930871