Spencer Luong, University of Alberta

Spencer Luong (University of Alberta), Dirk Taal (University of Alberta), Dr. Heather Eaton (University of Alberta), Tim Footz (University of Alberta), Paris Brown (University of Alberta), Dr. Maya Shmulevitz (University of Alberta))

Discovering & Evolving

Mammalian orthoreovirus (reovirus) is an oncolytic virus being studied to be used as cancer therapy as it preferentially replicates in tumor microenvironments, directly kills tumor cells and promotes anti-tumor immunity. Reovirus begins the replication cycle by binding to cells through the outer capsid protein, σ1. The head domain of σ1 binds to junctional adhesion molecule A (JAM-A) and the tail domain of σ1 binds to sialic acids (Sia) on the cell surface. Being that some breast cancer cells lack JAM-A, we examined whether JAM-A was essential for reovirus attachment, using flow cytometry. At physiological temperatures, there was minimal attachment of reovirus to JAM-A deficient E0771 murine mammary cancer cells. However, expression of JAM-A in E0771 rescued attachment of reovirus. We identified two reovirus variants among our library of sequenced reovirus mutants that could bind to JAM-A deficient E0771 cells; these variants contained a truncation of the σ1 head and unique mutations in the Sia-binding region. To validate Sia-specific JAM-A-independent attachment by these two reovirus variants, we utilized human erythrocytes (RBCs). Flow cytometry was used to confirm that RBCs express minimal surface JAM-A but moderate levels of Sia. Both variants bound significantly stronger to RBCs than wild-type reovirus at physiological temperatures, suggesting that the mutations enhance Sia-mediated attachment. Our results support the possibility of using mutations in the Sia binding region of reovirus to help potentiate reovirus as a cancer therapeutic in JAM-A-deficient breast cancers.