Cristi, F. | Search bioRxiv

bioRxiv2024

Mathematical Modelling of Reoviruses in Cancer Cell Cultures

Oncolytic virotherapy has emerged as a potential cancer therapy, utilizing viruses to selectively target and replicate within cancer cells while preserving normal cells. In this paper, we investigate the oncolytic potential of unmodified reovirus T3wt relative to a mutated variant SV5. In animal cancer cell monolayer experiments it was found that SV5 was more oncolytic relative to T3wt. SV5 forms larger sized plaques on cancer cell monolayers and spreads to farther distances from the initial site of infection as compared to T3wt. Paradoxically, SV5 attaches to cancer cells less efficiently than T3wt, which lead us to hypothesize that there might be an optimal binding affinity with maximal oncolytic activity. To understand the relationship between the binding process and virus spread for T3wt and SV5, we employ mathematical modelling. A reaction-diffusion model is applied, which is fit to the available data and then validated on data that were not used for the fit. Analysis of our model shows that there is an optimal binding rate that leads to maximum viral infection of the cancer monolayer, and we estimate this value for T3wt and SV5. Moreover, we find that the viral burst size is an important parameter for viral spread, and that a combination of efficient binding and large burst sizes is a promising direction to further develop anti-cancer viruses.

cancer biology↗

bioRxiv2019

Breast tumor-associated metalloproteases restrict reovirus oncolysis by cleaving the σ1 cell-attachment protein, and can be overcome by mutation of σ1

Reovirus is undergoing clinical testing as an oncolytic therapy for breast cancer. Given that reovirus naturally evolved to thrive in enteric environments, we sought to better understand how breast tumor microenvironments impinge on reovirus infection. Reovirus was treated with extracellular extracts generated from polyoma virus middle T-antigen-derived mouse breast tumors. Unexpectedly, these breast tumor extracellular extracts inactivated reovirus, reducing infectivity of reovirus particles by 100-fold. Mechanistically, inactivation was attributed to proteolytic cleavage of the viral cell attachment protein {sigma}1, which diminished virus binding to sialic acid-low tumor cells. Among various specific protease class inhibitors and metal ions, EDTA and ZnCl2 effectively modulated {sigma}1 cleavage, indicating that breast tumor-associated zinc-dependent metalloproteases are responsible for reovirus inactivation. Moreover, media from MCF7, MB468, MD-MB-231 and HS578T breast cancer cell lines recapitulated {sigma}1 cleavage and reovirus inactivation, suggesting that inactivation of reovirus is shared among mouse and human breast cancers, and that breast cancer cells in by themselves can be a source of reovirus-inactivating proteases. Binding assays and quantification of sialic acid (SA) levels on a panel of cancer cells showed that truncated {sigma}1 reduced virus binding to cells with low surface SA. To overcome this restriction, we generated a reovirus mutant with a mutation (T249I) in {sigma}1 that prevents {sigma}1 cleavage and inactivation by breast tumor-associated proteases. The mutant reovirus showed similar replication kinetics in tumorigenic cells, equivalent toxicity as wild-type reovirus in a severely compromised mouse model, and increased tumor titers. Overall, the data shows that tumor microenvironments have the potential to reduce infectivity of reovirus.\n\nSIGNIFICANCEWe demonstrate that metalloproteases in breast tumor microenvironments can inactivate reovirus. Our findings expose that tumor microenvironment proteases could have negative impact on proteinaceous cancer therapies such as reovirus, and that modification of such therapies to circumvent inactivation by tumor metalloproteases merits consideration.

microbiology↗