Vitamin D has long been recognized as essential to the skeletal system. Newer evidence suggests that it also plays a major role regulating the immune system, perhaps including immune responses to viral infection. Interventional and observational epidemiological studies provide evidence that vitamin D deficiency may confer increased risk of influenza and respiratory tract infection. Vitamin D deficiency is also prevalent among patients with HIV infection. Cell culture experiments support the thesis that vitamin D has direct anti-viral effects particularly against enveloped viruses. Though vitamin D’s anti-viral mechanism has not been fully established, it may be linked to vitamin D’s ability to up-regulate the anti-microbial peptides LL-37 and human beta defensin 2. Additional studies are necessary to fully elucidate the efficacy and mechanism of vitamin D as an anti-viral agent.

P pili are highly ordered composite structures consisting of thin fibrillar tips joined end-to-end to rigid helical rods. The production of these virulence-associated structures requires a periplasmic chaperone (PapD) and an outer membrane protein (PapC) that is the prototype member of a newly recognized class of proteins that we have named "molecular ushers." Two in vitro assays showed that the preassembly complexes that PapD forms with the three most distal tip fibrillar proteins (PapG, PapF, and PapE) bound to PapC. The relative afimity of each complex for PapC was found to

Large-scale multi-ethnic cohorts offer unprecedented opportunities to elucidate the genetic factors influencing complex traits related to health and disease among minority populations. At the same time, the genetic diversity in these cohorts presents new challenges for analysis and interpretation. We consider the utility of race and/or ethnicity categories in genome-wide association studies (GWASs) of multi-ethnic cohorts. We demonstrate that race/ethnicity information enhances the ability to understand population-specific genetic architecture. To address the practical issue that self-identified racial/ethnic information may be incomplete, we propose a machine learning algorithm that produces a surrogate variable, termed HARE. We use height as a model trait to demonstrate the utility of HARE and ethnicity-specific GWASs.

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HCV reoccurs after liver transplantation and increases mortality. Cyclosporine, but not tacrolimus, has potent antiviral effects against HCV replication in cell culture. To determine the conditions, if any, under which HCV is susceptible to cyclosporine in vivo, we selected for cyclosporine-resistant mutant HCV in vitro. The resulting mutations were mapped to x-ray crystallographic structures and sequence databases. Mutations selected by cyclosporine were clustered in the nonstructural (NS) proteins NS5A and NS5B. Different sets of mutations in NS5A, paired with the same 2 NS5B mutations, conferred different levels of cyclosporine resistance when engineered back into the HCV replicon. Mutations in NS5B are structurally consistent with a proposed model of regulation of RNA binding by cyclophilin B (CyPB). These mutations also highlight a natural polymorphism between different HCV genotypes that correlates with the variation in response to cyclosporine A (CsA) noted in some clinical trials. Replicons engineered to have mutations in only NS5A (P < 0.0001) or only NS5B (P ‫؍‬ 0.002) suggest that while both NS5A or NS5B variants alter cyclosporine susceptibility, NS5A has the largest effect. Conclusion: Preexisting sequence variation could alter the effect of cyclosporine on HCV in vivo. (HEPATOLOGY

Adhesive P pili of uropathogenic Escherichia coli were not assembled by a strain that lacks the periplasmic dulfide isomerase DsbA. This defect was mostly attributed to the immunoglobulin-like pilus chaperone PapD, which possesses an unusual Intrasheet disulfide bond between the last two (.strands of its CD4-like carboxyl-terminal domain. The DsbA-dependent formation of this disulfide bond was critical for PapD's proper folding in vivo. Interestingly, the absence of the disuifide bond did not prevent PapD from folding in vito or from forming a complex with the pilus adhesin in vitro. We suggest that DsbA maintains nascently translocated PapD in a folding-competent conformation prior to catalyzing disulfide bond formation, acting both as an oxidant and in a chaperonelike fashion. Disulfide bond formation in pilus subunits was also mediated by DsbA even in the absence of PapD. However, the ability ofpilus subunits to achieve native-like conformations in vivo depended on PapD. These results suggest that a productive folding pathway for subunits requires sequential interactions with DsbA and the PapD chaperone.

Obstacles to bacterial survival and replication in the cytosol of host cells, and the mechanisms used by bacterial pathogens to adapt to this niche are not well understood. Listeria monocytogenes is a well-studied Gram-positive foodborne pathogen that has evolved to invade and replicate within the host cell cytosol; yet the mechanisms by which it senses and responds to stress to survive in the cytosol are largely unknown. To assess the role of the L. monocytogenes penicillin-binding-protein and serine/threonine associated (PASTA) kinase PrkA in stress responses, cytosolic survival and virulence, we constructed a ΔprkA deletion mutant. PrkA was required for resistance to cell wall stress, growth on cytosolic carbon sources, intracellular replication, cytosolic survival, inflammasome avoidance and ultimately virulence in a murine model of Listeriosis. In Bacillus subtilis and Mycobacterium tuberculosis, homologues of PrkA phosphorylate a highly conserved protein of unknown function, YvcK. We found that, similar to PrkA, YvcK is also required for cell wall stress responses, metabolism of glycerol, cytosolic survival, inflammasome avoidance and virulence. We further demonstrate that similar to other organisms, YvcK is directly phosphorylated by PrkA, although the specific site(s) of phosphorylation are not highly conserved. Finally, analysis of phosphoablative and phosphomimetic mutants of YvcK in vitro and in vivo demonstrate that while phosphorylation of YvcK is irrelevant to metabolism and cell wall stress responses, surprisingly, a phosphomimetic, nonreversible negative charge of YvcK is detrimental to cytosolic survival and virulence in vivo. Taken together our data identify two novel virulence factors essential for cytosolic survival and virulence of L. monocytogenes. Furthermore, our data demonstrate that regulation of YvcK phosphorylation is tightly controlled and is critical for virulence. Finally, our data suggest that yet to be identified substrates of PrkA are essential for cytosolic survival and virulence of L. monocytogenes and illustrate the importance of studying protein phosphorylation in the context of infection.

BackgroundHepatitis C Virus (HCV) infection is a leading indication for liver transplantation. HCV infection reoccurs almost universally post transplant, decreasing both graft longevity and patient survival. The immunosuppressant, cyclosporine A (CsA) has potent anti-HCV activity towards both HCV replicons and the genotype 2a cell culture infectious virus. Previously, we isolated mutations in the 1bN replicon with less sensitivity to CsA that mapped to both NS5A and NS5B regions of the virus. Mutations in NS5A alone conferred decreased CsA susceptibility regardless of NS5B mutations.Methodology/Principal FindingsWe examined the mechanisms by which NS5A mutations contribute to CsA resistance and if they are strain dependent. Using in vitro mutagenesis, the amino acid position 321 mutation of NS5A was restored to the wild-type tyrosine residue conferring partial CsA susceptibility on the mutant replicon. The 321 mutation also alters CsA susceptibility of the JFH cell culture virus. Additionally, we demonstrated a novel CsA-sensitive interaction between NS5A and both cyclophilin A and B. Both the mutant NS5A and wild type NS5A bind cyclophilin in vitro. The NS5A: cyclophilin interaction requires both the NS5A region identified by the resistance mutants and cyclophilin catalytic residues. In cell culture, NS5A from CsA resistant mutant has an enhanced interaction with cyclophilin B. Additionally; NS5B facilitates a stronger binding of mutant NS5A to endogenous cyclophilin B than wild-type in cell culture.Conclusions/SignificanceCollectively, this data suggests direct interactions between cyclophilins and NS5A are critical to understand for optimal use of cyclophilin inhibitors in anti-HCV therapy.