Lymphatic Type 1 Interferon Responses Are Critical for Control of Systemic Reovirus Dissemination.

Mammalian orthoreovirus (reovirus) spreads from the site of infection to every organ system in the body via the blood. However, mechanisms that underlie reovirus hematogenous spread remain undefined. Nonstructural protein σ1s is a critical determinant of reovirus bloodstream dissemination that is required for efficient viral replication in many types of cultured cells. Here, we used the specificity of the σ1s protein for promoting hematogenous spread as a platform to uncover a role for lymphatic type 1 interferon (IFN-1) responses in limiting reovirus systemic dissemination. We found that replication of a σ1s-deficient reovirus was restored to wild-type levels in cells with defective interferon-α receptor (IFNAR1) signaling. Reovirus spreads systemically following oral inoculation of neonatal mice, whereas the σ1s-null virus remains localized to the intestine. We found that σ1s enables reovirus spread in the presence of a functional IFN-1 response, as the σ1s-deficient reovirus disseminated comparably to wild-type virus in IFNAR1-/- mice. Lymphatics are hypothesized to mediate reovirus spread from the intestine to the bloodstream. IFNAR1 deletion from cells expressing lymphatic vessel endothelium receptor 1 (LYVE-1), a marker for lymphatic endothelial cells, enabled the σ1s-deficient reovirus to disseminate systemically. Together, our findings indicate that IFN-1 responses in lymphatics limit reovirus dissemination. Our data further suggest that the lymphatics are an important conduit for reovirus hematogenous spread.IMPORTANCE Type 1 interferons (IFN-1) are critical host responses to viral infection. However, the contribution of IFN-1 responses to control of viruses in specific cell and tissue types is not fully defined. Here, we identify IFN-1 responses in lymphatics as important for limiting reovirus dissemination. We found that nonstructural protein σ1s enhances reovirus resistance to IFN-1 responses, as a reovirus mutant lacking σ1s was more sensitive to IFN-1 than wild-type virus. In neonatal mice, σ1s is required for reovirus systemic spread. We used tissue-specific IFNAR1 deletion in combination with the IFN-1-sensitive σ1s-null reovirus as a tool to test how IFN-1 responses in lymphatics affect reovirus systemic spread. Deletion of IFNAR1 in lymphatic cells using Cre-lox technology enabled dissemination of the IFN-1-sensitive σ1s-deficient reovirus. Together, our results indicate that IFN-1 responses in lymphatics are critical for controlling reovirus systemic spread.

Serotype-Specific Killing of Large Cell Carcinoma Cells by Reovirus.

Reovirus is under development as a therapeutic for numerous types of cancer. In contrast to other oncolytic viruses, the safety and efficacy of reovirus have not been improved through genetic manipulation. Here, we tested the oncolytic capacity of recombinant strains (rs) of prototype reovirus laboratory strains T1L and T3D (rsT1L and rsT3D, respectively) in a panel of non-small cell lung cancer (NSCLC) cell lines. We found that rsT1L was markedly more cytolytic than rsT3D in the large cell carcinoma cell lines tested, whereas killing of adenocarcinoma cell lines was comparable between rsT1L and rsT3D. Importantly, non-recombinant T1L and T3D phenocopied the kinetics and magnitude of cell death induced by recombinant strains. We identified gene segments L2, L3, and M1 as viral determinants of strain-specific differences cell killing of the large cell carcinoma cell lines. Together, these results indicate that recombinant reoviruses recapitulate the cell killing properties of non-recombinant, tissue culture-passaged strains. These studies provide a baseline for the use of reverse genetics with the specific objective of engineering more effective reovirus oncolytics. This work raises the possibility that type 1 reoviruses may have the capacity to serve as more effective oncolytics than type 3 reoviruses in some tumor types.