The similarity between the level of CD80 expression in TG of latently infected KOS and ICP22 null viruses is expected, since previously we have reported that the suppression of CD80 by ICP22 is dependent on the presence of active virus replication.22 These results show a direct correlation between lower replication in the eye, lower latency, lower reactivation, lower PD-1, and lower T-cell transcripts in D22 (ICP22 null) virus infections. Here, CD80 is linked to viral infectious disease.