An antiviral vaccine that encodes costimulation molecules for increasing immune response to the particular virus at issue is provided herein. In an illustrative embodiment, in mice lacking both B7-1 and B7-2 (B7KO), the increased severity of HSV infection has confirmed the importance of these molecules in generation of HSV-specific immunity. To test the concept that B7-1 or B7-2 expression by replication-defective HSV could augment its immunogenicity and protective capacity, the present inventors constructed replication-defective HSV-2 encoding B7-1 or B7-2. Both viruses partially reconstituted immune responses to HSV compared with replication-defective virus alone when used to immunize B7KO mice, indicating that the increased responsiveness to virus could be attributed to virus-encoded B7 molecules.