A closer look at prion strains

Prions are infectious proteins that are responsible for transmissible spongiform encephalopathies (TSEs) and consist primarily of scrapie prion protein (PrP^Sc), a pathogenic isoform of the host-encoded cellular prion protein (PrP^C). The absence of nucleic acids as essential components of the infectious prions is the most striking feature associated to these diseases. Additionally, different prion strains have been isolated from animal diseases despite the lack of DNA or RNA molecules. Mounting evidence suggests that prion-strain-specific features segregate with different PrP^Sc conformational and aggregation states.

Strains are of practical relevance in prion diseases as they can drastically differ in many aspects, such as incubation period, PrP^Sc biochemical profile (e.g., electrophoretic mobility and glycoform ratio) and distribution of brain lesions. Importantly, such different features are maintained after inoculation of a prion strain into genetically identical hosts and are relatively stable across serial passages.

This review focuses on the characterization of prion strains and on the wide range of important implications that the study of prion strains involves.     

Chikungunya Virus Infection Results in Higher and Persistent Viral Replication in Aged Rhesus Macaques Due to Defects in Anti-Viral Immunity

Chikungunya virus (CHIKV) is a re-emerging mosquito-borne Alphavirus that causes a clinical disease involving fever, myalgia, nausea and rash. The distinguishing feature of CHIKV infection is the severe debilitating poly-arthralgia that may persist for several months after viral clearance. Since its re-emergence in 2004, CHIKV has spread from the Indian Ocean region to new locations including metropolitan Europe, Japan, and even the United States. The risk of importing CHIKV to new areas of the world is increasing due to high levels of viremia in infected individuals as well as the recent adaptation of the virus to the mosquito species Aedes albopictus. CHIKV re-emergence is also associated with new clinical complications including severe morbidity and, for the first time, mortality. In this study, we characterized disease progression and host immune responses in adult and aged Rhesus macaques infected with either the recent CHIKV outbreak strain La Reunion (LR) or the West African strain 37997. Our results indicate that following intravenous infection and regardless of the virus used, Rhesus macaques become viremic between days 1–5 post infection. While adult animals are able to control viral infection, aged animals show persistent virus in the spleen. Virus-specific T cell responses in the aged animals were reduced compared to adult animals and the B cell responses were also delayed and reduced in aged animals. Interestingly, regardless of age, T cell and antibody responses were more robust in animals infected with LR compared to 37997 CHIKV strain. Taken together these data suggest that the reduced immune responses in the aged animals promotes long-term virus persistence in CHIKV-LR infected Rhesus monkeys.     

Animal Models In Mycology: What Have We Learned Over The Past 30 Years

Animal models have long been used to explore various pathophysiological, immunological and microbiological questions in the field of medical mycology. These models have been adapted and altered over time, yet their use has persisted. They remain valuable as research tools due to similarities to processes in human physiology and disease, and are evolving to include more fungal pathogens and infections that better mimic disease in humans. Animal availability, animal cost, housing requirements, the need for immunosuppression, the potential for tissue, fluid or blood samples, a researcher’s familiarity with the model, as well as governmental or institutional regulations, must all be considered when selecting an appropriate one to use. Although the questions of interest have changed over the past 30 years, one idea persists: animal models are valuable tools in research that span the gap between the bench and the clinic.     

Characterization of a surrogate murine antibody to model anti-human CD3 therapies

Fc-modified anti-human CD3ε monoclonal antibodies (mAbs) are in clinical development for the treatment of autoimmune diseases. These next generation mAbs have completed clinical trials in patients with type-1 diabetes and inflammatory bowel disease demonstrating a narrow therapeutic window. Lowered doses are ineffective, yet higher pharmacologically-active doses cause an undesirable level of adverse events. Thus, there is a critical need for a return to bench research to explore ways of improving clinical outcomes. Indeed, we recently reported that a short course of treatment affords synergy, providing long-term disease amelioration when combining anti-mouse CD3 and anti-mouse tumor necrosis factor mAbs in experimental arthritis. Such strategies may widen the window between risk and benefit; however, to more accurately assess experimentally the biology and pharmacology, reagents that mimic the current development candidates were required. Consequently, we engineered an Fc-modified anti-mouse CD3ε mAb, 2C11-Novi. Here, we report the functional characterization of 2C11-Novi demonstrating that it does not bind FcγR in vitro and elicits little cytokine release in vivo, while maintaining classical pharmacodynamic effects (CD3-TCR downregulation and T cell killing). Furthermore, we observed that oral administration of 2C11-Novi ameliorated progression of remitting-relapsing experimental autoimmune encephalitis in mice, significantly reducing the primary acute and subsequent relapse phase of the disease. With innovative approaches validated in two experimental models of human disease, 2C11-Novi represents a meaningful tool to conduct further mechanistic studies aiming at exploiting the immunoregulatory properties of Fc-modified anti-CD3 therapies via combination therapy using parenteral or oral routes of administration.     

Different Permeability of Potassium Salts across the Blood-Brain Barrier Follows the Hofmeister Series

The passage of ions across biological membranes is regulated by passive and active mechanisms. Passive ion diffusion into organs depends on the ion-pairing properties of salts present in the serum. Potassium ions could affect brain activity by crossing the blood-brain barrier (BBB) and its accumulation in the extracellular cerebral space could precipitate seizures. In the present study, we analyze passive diffusion of a series of potassium salts in the in vitro isolated guinea pig brain preparation. Different potassium counter-anions confer ion-pairing and lipophilicity properties that modulate membrane diffusion of the salt. Extracellular recordings in different cortical areas demonstrated the presence of epileptiform activities that strongly relate to anion identity, following the qualitative order of the Hofmeister series. Indeed, highly lipophilic salts that easily cross the BBB enhanced extracellular potassium concentration measured by ion-selective electrodes and were the most effective pro-epileptic species. This study constitutes a novel contribution for the understanding of the potential epileptogenicity of potassium salts and, more generally, of the role of counter-anions in the passive passage of salts through biological membranes.     

Exploring Leptin Antagonism in Ophthalmic Cell Models

Background

Emerging evidence suggests that angiogenic and pro-inflammatory cytokine leptin might be implicated in ocular neovascularization. However, the potential of inhibiting leptin function in ophthalmic cells has never been explored. Here we assessed mitogenic, angiogenic, and signaling leptin activities in retinal and corneal endothelial cells and examined the capability of a specific leptin receptor (ObR) antagonist, Allo-aca, to inhibit these functions.

Methods and Results

The experiments were carried out in monkey retinal (RF/6A) and bovine corneal (BCE) endothelial cells. Leptin at 50-250 ng/mL stimulated the growth of both cell lines in a dose-dependent manner. The maximal mitogenic response (35±7 and 27±3% in RF6A and BCE cells, respectively) was noted at 24 h of 250 ng/mL leptin treatments. Leptin-dependent proliferation was reduced to base levels with 10 and 100 nM Allo-aca in BCE and RF6A cells, respectively. In both cell lines, leptin promoted angiogenic responses, with the maximal increase in tube formation (163±10 and 133±8% in RF6A and BCE cultures, respectively) observed under a 250 ng/mL leptin treatment for 3 h. Furthermore, in both cell lines 250 ng/mL leptin modulated the activity or expression of several signaling molecules involved in proliferation, inflammatory activity and angiogenesis, such as STAT3, Akt, and ERK1/2, COX2, and NFκB. In both cell lines, leptin-induced angiogenic and signaling responses were significantly inhibited with 100 nM Allo-aca. We also found that leptin increased its own mRNA and protein expression in both cell lines, and this autocrine effect was abolished by 100-250 nM Allo-aca.

Conclusions

Our data provide new insights into the role of leptin in ocular endothelial cells and represent the first original report on targeting ObR in ophthalmic cell models.     

Steps to Take to Enhance Gait Stability: The Effect of Stride Frequency,Stride Length,and Walking Speed on Local Dynamic Stability and Margins of Stability

The purpose of the current study was to investigate whether adaptations of stride length, stride frequency, and walking speed, independently influence local dynamic stability and the size of the medio-lateral and backward margins of stability during walking. Nine healthy subjects walked 25 trials on a treadmill at different combinations of stride frequency, stride length, and consequently at different walking speeds. Visual feedback about the required and the actual combination of stride frequency and stride length was given during the trials. Generalized Estimating Equations were used to investigate the independent contribution of stride length, stride frequency, and walking speed on the measures of gait stability. Increasing stride frequency was found to enhance medio-lateral margins of stability. Backward margins of stability became larger as stride length decreased or walking speed increased. For local dynamic stability no significant effects of stride frequency, stride length or walking speed were found. We conclude that adaptations in stride frequency, stride length and/or walking speed can result in an increase of the medio-lateral and backward margins of stability, while these adaptations do not seem to affect local dynamic stability. Gait training focusing on the observed stepping strategies to enhance margins of stability might be a useful contribution to programs aimed at fall prevention.     

Geographic variation in the greater Japanese shrew-mole,Urotrichus talpoides: Combining morphological and chromosomal patterns

Although much information on the species dynamics of small mammals may be gleaned from the integration of morphological and molecular data sets, the two are not routinely combined when species boundaries and definitions are investigated. The greater Japanese shrew-mole (Urotrichus talpoides) presents a rare example of intraspecific and geographical euchromatic chromosomal variation. In this study a combination of 2D landmark-based and outline-based geometric morphometric methods were used to provide the first quantitative examination of variation in skull morphology occurring between populations of U. talpoides. Geographic variation was found to be most conspicuous in ventral and dorsal cranial morphology, and less evident for outline-based analyses of the dentary, thereby indicating differing magnitudes of skeletal plasticity associated with geographic variation in each system. Both ventral and dorsal cranial morphology differed significantly between shrew-moles from western and eastern Honshu, in agreement with previously identified chromosomal variation boundaries. Inclusion of other island populations revealed shape differences between shrew-moles in Kyushu, Tsushima and North Honshu. These results lend general support for the unification of morphological and chromosomal data when assessing species boundaries.