Replication and expression of oncolytic herpes simplex virus type Ⅱ in tumors

Abstract

This study aimed to measure the duration and replication level of oncolytic herpes simplex virus type 2 (oHSV2) at the tumor injection site in BALB/c mice. Additionally, the expression level of human granulocyte macrophage colony-stimulating factor (hGM-CSF) and HSV-2 antibody in the serum was also measured. High and low doses of oHSV2-Fluc (firefly luciferin, Fluc) were injected into the mice's tumors to track the change and duration of fluorescence expression. The copy number of oHSV2 gene in tumor tissues was determined using quantitative real-time polymerase chain reaction (qPCR). Enzyme linked immunosorbent assay (ELISA) was used to detect the expression of hGM-CSF and HSV-2 antibody in the serum. The tumor volume in the high-dose group was significantly lower than that in the control group (P < 0.01). Intratumor injection of oHSV2-Fluc showed that the carried Fluc could continue to express in the tumor, with fluorescence still detectable at day 11 and declining to undetectable level by day 18. The mRNA expression of oHSV2 was detected in tumor tissues of both high and low dose groups on day 9 using qPCR. ELISA results showed that the levels of HSV2 antibody and hGM-CSF in both high and low dose groups were significantly increased compared to the control group (P < 0.05) after collecting orbital blood. These findings suggest that oHSV2 can replicate in the tumor and sustainably express exogenous factors, thus effectively targeting and killing the tumor. Furthermore, intratumoral injection of oHSV2 resulted in higher levels of hGM-CSF and HSV-2 antibodies found in the mice's serum.