Repetitive Immunization Enhances the Susceptibility of Mice to Peripherally Administered Prions

The susceptibility of humans and animals to prion infections is determined by the virulence of the infectious agent, by genetic modifiers, and by hitherto unknown host and environmental risk factors. While little is known about the latter two, the activation state of the immune system was surmised to influence prion susceptibility. Here we administered prions to mice that were repeatedly immunized by two initial injections of CpG oligodeoxynucleotides followed by repeated injections of bovine serum albumin/alum. Immunization greatly reduced the required dosage of peripherally administered prion inoculum necessary to induce scrapie in 50% of mice. No difference in susceptibility was observed following intracerebral prion challenge. Due to its profound impact onto scrapie susceptibility, the host immune status may determine disease penetrance after low-dose prion exposure, including those that may give rise to iatrogenic and variant Creutzfeldt-Jakob disease

Using Selectively Applied Accelerated Molecular Dynamics to Enhance Free Energy Calculations

Accelerated molecular dynamics (aMD) has been shown to enhance conformational space sampling relative to classical molecular dynamics; however, the exponential reweighting of aMD trajectories, which is necessary for the calculation of free energies relating to the classical system, is oftentimes problematic, especially for systems larger than small poly peptides. Here, we propose a method of accelerating only the degrees of freedom most pertinent to sampling, thereby reducing the total acceleration added to the system and improving the convergence of calculated ensemble averages, which we term selective aMD. Its application is highlighted in two biomolecular cases. First, the model system alanine dipeptide is simulated with classical MD, all-dihedral aMD, and selective aMD, and these results are compared to the infinite sampling limit as calculated with metadynamics. We show that both forms of aMD enhance the convergence of the underlying free energy landscape by 5-fold relative to classical MD; however, selective aMD can produce improved statistics over all-dihedral aMD due to the improved reweighting. Then we focus on the pharmaceutically relevant case of computing the free energy of the decoupling of oseltamivir in the active site of neuraminidase. Results show that selective aMD greatly reduces the cost of this alchemical free energy transformation, whereas all-dihedral aMD produces unreliable free energy estimates

Jagged1 Ablation Results in Cerebellar Granule Cell Migration Defects and Depletion of Bergmann Glia

Jagged1 is a ligand for members of the Notch family of receptors. Mutations in the human JAG1 gene are the major cause of Alagille syndrome, an autosomal dominant disorder affecting the liver, heart, eye, skeleton, kidneys, and craniofacial structures. Although expressed throughout mammalian embryonic development and in the adult, the function of Jagged1 in the central nervous system is not clear. Jagged1 is broadly expressed in the cerebellum suggesting an important role in Notch signaling. In order to address the function of Jagged1 in the mouse central nervous system, we have inactivated the Jag1 gene in the cerebellar primordium at mid-embryogenesis. Loss of Jagged1 results in aberrant granule cell migration and ectopic differentiation in the external germinal layer and molecular layer of the early postnatal cerebellum. We show that Bergmann glia in the cerebellum lose contact to the pial surface and have stunted processes. In vitro analysis revealed a depletion of Bergmann glia in the Jagged1 mutant mice. Our findings suggest that Jagged1 plays a role in cell fate specification and survival in the cerebellum

Clusterin Is a Potential Lymphotoxin Beta Receptor Target That Is Upregulated and Accumulates in Germinal Centers of Mouse Spleen during Immune Response

<div><p>Clusterin is a multifunctional protein that participates in tissue remodeling, apoptosis, lipid transport, complement-mediated cell lysis and serves as an extracellular chaperone. The role of clusterin in cancer and neurodegeneration has been extensively studied, however little is known about its functions in the immune system. Using expression profiling we found that clusterin mRNA is considerably down-regulated in mouse spleen stroma upon knock-out of lymphotoxin β receptor which plays pivotal role in secondary lymphoid organ development, maintenance and function. Using immunohistochemistry and western blot we studied clusterin protein level and distribution in mouse spleen and mesenteric lymph nodes in steady state and upon immunization with sheep red blood cells. We showed that clusterin protein, represented mainly by the secreted heterodimeric form, is present in all stromal compartments of secondary lymphoid organs except for marginal reticular cells. Clusterin protein level rose after immunization and accumulated in light zones of germinal centers in spleen - the effect that was not observed in lymph nodes. Regulation of clusterin expression by the lymphotoxin beta signaling pathway and its protein dynamics during immune response suggest a specific role of this enigmatic protein in the immune system that needs further study.</p></div