Accumulating evidence demonstrates that the intestinal microbiota enhance mammalian enteric virus infections. For example, we and others have previously reported that commensal bacteria stimulate acute and persistent murine norovirus infections. In apparent contradiction to these results however, the virulence of murine norovirus infection was unaffected by antibiotic treatment. This prompted us to perform a detailed investigation of murine norovirus infection in microbially deplete mice, revealing a more complex picture whereby commensal bacteria inhibit viral infection of the proximal small intestine while simultaneously stimulating infection of distal regions of the gut. Thus, commensal bacteria can regulate viral regionalization along the intestinal tract. We further show that the mechanism underlying bacteria-dependent inhibition of norovirus infection in the proximal gut is bile acid priming of type III interferon. Finally, the regional effects of the microbiota on norovirus infection may result from distinct regional expression profiles of key bile acid receptors which regulate the type III interferon response. Overall, these findings reveal that biotransformation of host metabolites by the intestinal microbiota directly and regionally impacts infection by a pathogenic enteric virus.

Pure nicotine impairs macrophage killing of Mycobacterium tuberculosis (MTB), but it is not known whether the nicotine component in cigarette smoke (CS) plays a role. Moreover, the mechanisms by which nicotine impairs macrophage immunity against MTB have not been explored. To neutralize the effects of nicotine in CS extract, we used a competitive inhibitor to the nicotinic acetylcholine receptor (nAChR)-mecamylamine-as well as macrophages derived from mice with genetic disruption of specific subunits of nAChR. We also determined whether nicotine impaired macrophage autophagy and whether nicotine-exposed T regulatory cells (Tregs) could subvert macrophage anti-MTB immunity. Mecamylamine reduced the CS extract increase in MTB burden by 43%. CS extract increase in MTB was also significantly attenuated in macrophages from mice with genetic disruption of either the α7, β2, or β4 subunit of nAChR. Nicotine inhibited autophagosome formation in MTB-infected THP-1 cells and primary murine alveolar macrophages, as well as increased the intracellular MTB burden. Nicotine increased migration of THP-1 cells, consistent with the increased number of macrophages found in the lungs of smokers. Nicotine induced Tregs to produce transforming growth factor-β. Naive mouse macrophages co-cultured with nicotine-exposed Tregs had significantly greater numbers of viable MTB recovered with increased IL-10 production and urea production, but no difference in secreted nitric oxide as compared with macrophages cocultured with unexposed Tregs. We conclude that nicotine in CS plays an important role in subverting macrophage control of MTB infection.

Mammalian orthoreovirus (reovirus) is under development as a cancer virotherapy. Clinical trials demonstrate that reovirus-based therapies are safe and tolerated in patients with a wide variety of cancers. Although reovirus monotherapy has proven largely ineffective, reovirus sensitizes cancer cells to existing chemotherapeutic agents and radiation. Clinical trials are underway to test the efficacy of reovirus in combination with chemotherapeutic and radiation regimens and to evaluate the effectiveness of reovirus in conjunction with immunotherapies. Central to the use of reovirus to treat cancer is its capacity to directly kill cancer cells and alter the cellular environment to augment other therapies. Apoptotic cell death is a prominent mechanism of reovirus cancer cell killing. However, reoviruses can also kill cancer cells through nonapoptotic mechanisms. Here, we describe mechanisms of reovirus cancer cell killing, highlight how reovirus is used in combination with existing cancer treatments, and discuss what is known as to how reovirus modulates cancer immunotherapy.

The NMDA receptor (NMDAR) is inhibited by synaptically released zinc. This inhibition is thought to be the result of zinc diffusion across the synaptic cleft and subsequent binding to the extracellular domain of the NMDAR. However, this model fails to incorporate the observed association of the highly zinc-sensitive NMDAR subunit GluN2A with the postsynaptic zinc transporter ZnT1, which moves intracellular zinc to the extracellular space. Here, we report that disruption of ZnT1-GluN2A association by a cell-permeant peptide strongly reduced NMDAR inhibition by synaptic zinc in mouse dorsal cochlear nucleus synapses. Moreover, synaptic zinc inhibition of NMDARs required postsynaptic intracellular zinc, suggesting that cytoplasmic zinc is transported by ZnT1 to the extracellular space in close proximity to the NMDAR. These results challenge a decades-old dogma on how zinc inhibits synaptic NMDARs and demonstrate that presynaptic release and a postsynaptic transporter organize zinc into distinct microdomains to modulate NMDAR neurotransmission.

Intestinal commensal bacteria contribute to maintaining gut homeostasis. Disruptions to the commensal flora are linked to the development and persistence of disease. The importance of these organisms is further demonstrated by the widespread ability of enteric viruses to exploit commensal bacteria to enhance viral infection. These viruses interact directly with commensal bacteria, and while the impact of this interaction on viral infection is well described for several viruses, the impact on the commensal bacteria has yet to be explored. In this article, we demonstrate, for the first time, that enteric viruses alter the gene expression and phenotype of individual commensal bacteria. Human and murine norovirus interaction with bacteria resulted in genome‐wide differential gene expression and marked changes in the surface architecture of the bacterial cells. Furthermore, the interaction of the virus with bacteria led to increased production of smaller outer membrane vesicles (OMVs). Enhanced production of smaller vesicles was also observed when noroviruses were incubated with other commensal bacteria, indicating a potentially broad impact of norovirus interaction. The vesicle production observed in the in vivo model followed a similar trend where an increased quantity of smaller bacterial vesicles was observed in stool collected from virus‐infected mice compared to mock‐infected mice. Furthermore, changes in vesicle size were linked to changes in protein content and abundance, indicating that viral binding induced a shift in the mechanism of the OMV biogenesis. Collectively, these data demonstrate that enteric viruses induce specific changes in bacterial gene expression, leading to changes in bacterial extracellular vesicle production that can potentially impact host responses to infection.

Lipiophilic dyes such as Laurdan and Prodan are widely used in membrane biology due to a strong bathochromic shift in emission that reports structural parameters of the membrane such as area per molecule. Disentangling the factors which control the spectral shift is complicated by the stabilization of a charge-transfer-like excitation of the dye in polar environments. Predicting the emission therefore requires modeling both the relaxation of the environment and the corresponding evolution of the excited state. Here an approach is presented in which (i) the local environment is sampled by classical molecular dynamics (MD) simulation of the dye and solvent; (ii) the electronically excited state of Prodan upon light absorption is predicted by numerical quantum mechanics (QM); (iii) iterative relaxation of the environment around the excited dye by MD coupled with evolution of the excited state is performed; (iv) the emission properties are predicted by QM. The QM steps are computed using many-body Green's functions theory in the GW approximation and the Bethe-Salpeter Equation with the environment modeled as fixed point charges, sampled in the MD simulation steps. Comparison to ultrafast time resolved transient absorption measurements demonstrates that the iterative MM/QM approach agrees quantitatively with both the polarity dependent shift in emission and the timescale over which the charge transfer state is stabilized. Together the simulations and experimental measurements suggest that evolution into the charge-transfer state is slower in amphiphilic solvents. File list (2) download file view on ChemRxiv maintext.pdf (3.25 MiB) download file view on ChemRxiv SI.pdf (7.99 MiB) Ultrafast formation of the charge-transfer state of prodan reveals unique aspects of the chromophore environment

Reovirus non-structural protein σ1s is required for the establishment of viremia and hematogenous viral dissemination. However, the function of the σ1s protein during the reovirus replication cycle is not known. In this study, we found that σ1s was required for efficient reovirus replication in SV40-immortalized endothelial cells (SVECs), mouse embryonic fibroblasts, human umbilical vein endothelial cells (HUVECs), and T84 human colonic epithelial cells. In each of these cell lines, wild type reovirus produced substantially higher viral titers than a σ1s-deficient mutant. The σ1s protein was not required for early events in the reovirus infection, as no difference in infectivity between the wild type and σ1s-null viruses was observed. However, wild type virus produced markedly higher viral protein levels than the σ1s-deficient strain. The disparity in viral replication did not result from differences in viral transcription or protein stability. We further found that the σ1s protein was dispensable for cell killing and induction of type-1 interferon responses. In the absence of σ1s, viral factory (VF) maturation was impaired, but sufficient to support low levels of reovirus replication. Together, our results indicate that σ1s is not absolutely essential for viral protein production, but rather potentiates reovirus protein expression to facilitate reovirus replication. Our findings suggest that σ1s enables hematogenous reovirus dissemination by promoting efficient viral protein synthesis, and thereby reovirus replication, in cells that are required for reovirus spread to the blood.Hematogenous dissemination is critical a step in the pathogenesis of many viruses. For reovirus, nonstructural protein σ1s is required for viral spread via the blood. However, the mechanism by σ1s promotes reovirus dissemination is unknown. Here, we identified σ1s as a viral mediator of reovirus protein expression. We found several cultured cell lines in which σ1s is required for efficient reovirus replication. In these cells, wild type virus produced substantially higher levels of viral protein than a σ1s-deficient mutant. The σ1s protein was not required for viral mRNA transcription or viral protein stability. Owing to reduced levels of viral protein synthesized in the absence of σ1s, maturation of viral factories was impaired and significantly fewer viral progeny were produced. Taken together, our findings indicate that σ1s is required for optimal reovirus protein production, and thereby viral replication, in cells required hematogenous reovirus dissemination.

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