CD8A and Splenomegaly: This may be due to the following reasons: (1) The CD8+ T lymphocytes induced by oncolytic HSV1 may be mainly specific to the virus itself (a strong immunogen compared with 4T1 cells) and this was supported by marked splenomegaly observed after oncolytic virus alone treatment (data not shown), and (2) the hGM-CSF carried by oncolytic HSV1 was ineffective in mice due to species differences [61].