Genotype of Immunologically Hot or Cold Tumors Determines the Antitumor Immune Response and Efficacy by Fully Virulent Retargeted oHSV

Abstract

We report on the efficacy of the non-attenuated HER2-retargeted oHSV named R-337 against the immunologically hot CT26-HER2 tumor, and an insight into the basis of the immune protection. Preliminarily, we conducted an RNA immune profiling and immune cell content characterization of CT26-HER2 tumor in comparison to the immunologically cold LLC1-HER2 tumor. CT26-HER2 tumor was implanted into HER2-transgenic BALB/c mice. Hallmarks of R-337 effects were the protection from primary tumor, long-term adaptive vaccination directed to both HER2 and CT26-wt cell neoantigens. The latter effect differentiated R-337 from OncoVEXGM-CSF. As to the basis of the immune protection, R-337 orchestrated several changes to the tumor immune profile, which cumulatively reversed the immunosuppression typical of this tumor (graphical abstract). Thus, Ido1 (inhibitor of T cell anticancer immunity) levels and T regulatory cell infiltration were decreased; Cd40 and Cd27 co-immunostimulatory markers were increased; the IFNγ cascade was activated. Of note was the dampening of IFN-I response, which we attribute to the fact that R-337 is fully equipped with genes that contrast the host innate response. The IFN-I shut-down likely favored viral replication and the expression of the mIL-12 payload, which, in turn, boosted the antitumor response. The results call for a characterization of tumor immune markers to employ oncolytic herpesviruses more precisely.

Efficacy of Systemically Administered Retargeted Oncolytic Herpes Simplex Viruses—Clearance and Biodistribution in Naïve and HSV-Preimmune Mice

“…CT26 tumors are syngeneic with BALB/c mice. To mimic the situation in humans more faithfully, we employed BALB/c-TG mice transgenic/tolerant to human HER2 that we had previously generated [ 40 ]. The mice were then treated IV with R-337, according to the schedule shown in Figure 1 A, and sacrificed at d 17.…”

“…In vivo experiments. BALB/c mice transgenic for and tolerant to human HER2 (BALB/c-TG) were previously described [ 40 ], and C57BL/6 mice were obtained from Charles River Laboratories (Wilmington, MA, USA); both mouse strains were bred in the facility of the Department of Veterinary Medical Sciences, University of Bologna. Male and female mice were used randomly for the experiments, in accordance with the request from the Ethics Committee.…”

“…Their specificity, safety profile, and anticancer efficacy upon i.t. administration have been extensively documented [ 30 , 39 , 40 , 41 ]. Given their ability to not cause off-tumor and off-target infections, in principle ReHVs are more suitable for systemic delivery than pantropic oHSVs.…”

Cancer immunotherapy strategies that target the cGAS-STING pathway

“…Due to the low mutational burden and low expression of antigen-presentation markers, "immune cold tumors" lack infiltration of CTLs both inside and at the margins of the tumor, which respond poorly to immune checkpoint inhibitors (ICIs) and are often associated with poor prognosis (88)(89)(90). Therefore, such combination therapies are essential to overcome the immune deficiency and convert cold tumors into hot tumors.…”

Decrease in Heparan Sulphate Binding in Tropism-Retargeted Oncolytic Herpes Simplex Virus (ReHV) Delays Blood Clearance and Improves Systemic Anticancer Efficacy

“…BALB/c mice transgenic for, and tolerant to, human HER2 (BALB/c-TG) were previously described [ 57 ] and bred in the facility of the Department of Veterinary Medical Sciences, University of Bologna. The animals were housed in individually ventilated cages measuring 500 cm² each (NexGen™ Mouse 500, Allentown Inc., Allentown, NJ, USA), with 50 air changes per hour via HEPA-filtered air and had access to feed and water ad libitum.…”