Progress on low susceptibility mechanisms of transmissible spongiform encephalopathies

First report of a novel polymorphism and genetic characteristics of the leporine prion protein (PRNP) gene

Transmissible spongiform encephalopathies (TSEs) have been reported in a broad spectrum of hosts. The genetic polymorphisms and characteristics of the prion protein (PRNP) gene have a vital impact on the development of TSEs. Notably, natural TSE infection cases have never been reported in rabbits, and genetic variations of the leporine PRNP gene have not been investigated to date. To identify leporine PRNP gene polymorphism, we performed amplicon sequencing in 203 rabbits. We report a novel single nucleotide polymorphism on the leporine PRNP gene. In addition, we performed a comparative analysis of amino acid sequences of prion protein (PrP) across several hosts using ClustalW2. Furthermore, we evaluated the effect of changes of unique leporine PrP amino acids with those conserved among various species using Swiss-Pdb Viewer. Interestingly, we found seven unique leporine amino acids, and the change of unique leporine amino acids with those conserved among other species, including S175N, Q221K, Q221R, A226Y, A230G, and A230S, was predicted to reduce hydrogen bonds in leporine PrP.

Manufacturing Mesenchymal Stromal Cells for the Treatment of Osteoarthritis in Canine Patients: Challenges and Recommendations

The recent interest in advanced biologic therapies in veterinary medicine has opened up opportunities for new treatment modalities with considerable clinical potential. Studies with mesenchymal stromal cells (MSCs) from animal species have focused on in vitro characterization (mostly following protocols developed for human application), experimental testing in controlled studies and clinical use in veterinary patients. The ability of MSCs to interact with the inflammatory environment through immunomodulatory and paracrine mechanisms makes them a good candidate for treatment of inflammatory musculoskeletal conditions in canine species. Analysis of existing data shows promising results in the treatment of canine hip dysplasia, osteoarthritis and rupture of the cranial cruciate ligament in both sport and companion animals. Despite the absence of clear regulatory frameworks for veterinary advanced therapy medicinal products, there has been an increase in the number of commercial cell-based products that are available for clinical applications, and currently the commercial use of veterinary MSC products has outpaced basic research on characterization of the cell product. In the absence of quality standards for MSCs for use in canine patients, their safety, clinical efficacy and production standards are uncertain, leading to a risk of poor product consistency. To deliver high-quality MSC products for veterinary use in the future, there are critical issues that need to be addressed. By translating standards and strategies applied in human MSC manufacturing to products for veterinary use, in a collaborative effort between stem cell scientists and veterinary researchers and surgeons, we hope to facilitate the development of quality standards. We point out critical issues that need to be addressed, including a much higher level of attention to cell characterization, manufacturing standards and release criteria. We provide a set of recommendations that will contribute to the standardization of cell manufacturing methods and better quality assurance.

Novel Polymorphisms and Genetic Characteristics of the Prion Protein Gene (PRNP) in Dogs-A Resistant Animal of Prion Disease

Transmissible spongiform encephalopathies (TSEs) have been reported in a wide range of species. However, TSE infection in natural cases has never been reported in dogs. Previous studies have reported that polymorphisms of the prion protein gene (PRNP) have a direct impact on the susceptibility of TSE. However, studies on polymorphisms of the canine PRNP gene are very rare in dogs. We examined the genotype, allele, and haplotype frequencies of canine PRNP in 204 dogs using direct sequencing and analyzed linkage disequilibrium (LD) using Haploview version 4.2. In addition, to evaluate the impact of nonsynonymous polymorphisms on the function of prion protein (PrP), we carried out in silico analysis using PolyPhen-2, PROVEAN, and PANTHER. Furthermore, we analyzed the structure of PrP and hydrogen bonds according to alleles of nonsynonymous single nucleotide polymorphisms (SNPs) using the Swiss-Pdb Viewer program. Finally, we predicted the impact of the polymorphisms on the aggregation propensity of dog PrP using AMYCO. We identified a total of eight polymorphisms, including five novel SNPs and one insertion/deletion polymorphism, and found strong LDs and six major haplotypes among eight polymorphisms. In addition, we identified significantly different distribution of haplotypes among eight dog breeds, however, the kinds of identified polymorphisms were different among each dog breed. We predicted that p.64_71del HGGGWGQP, Asp182Gly, and Asp182Glu polymorphisms can impact the function and/or structure of dog PrP. Furthermore, the number of hydrogen bonds of dog PrP with the Glu182 and Gly182 alleles were predicted to be less than those with the Asp182 allele. Finally, Asp163Glu and Asp182Gly showed more aggregation propensity than wild-type dog PrP. These results suggest that nonsynonymous SNPs, Asp182Glu and Asp182Gly, can influence the stability of dog PrP and confer the possibility of TSE infection in dogs.

Comparative Investigation of Cutting Devices on Bone Blocks: An SEM Morphological Analysis

Background: Bone regeneration is a reliable technique when the bone volume is insufficient to provide a functional and aesthetic outcome in surgery and implantoprosthesis procedures. When bone blocks are used but do not match the shape of the defect, the block must be adapted. The aim of our research was to evaluate, by Scanning Electron Microscopy (SEM) morphological observation, how different cutting devices modify the bone surface. Method: Four equine bone blocks were divided into 15 cubic shape samples with ultrasonic and sonic tips, as well as diamond, tungsten carbide, and Lindemann burs. The uncut surface of the obtained bone block was used as a control. Two observers independently analyzed the SEM observation recording, including cut precision, depth of incision, thermal damages, and presence of bone debris. For each group, sharpness, depth, carbonization, and bone debris were expressed as mean values. Results: The osteotomy performed with an ultrasonic tip shows the best results, preserving the bone morphology in both quantitative and qualitative analyses. The bone surface appeared sufficiently clean from debris and showed a reduced presence of carbonization. Conclusion: The shaping of the bone block as in vivo osteotomy respects the bone morphology and allows it to achieve the relevant biological and clinical outcome.

The first report of genetic variations in the chicken prion protein gene

Abnormal structural changes of the prion protein (PrP) are the cause of prion disease in a wide range of mammals. However, spontaneous infected cases have not been reported in chicken. Genetic variations of the prion protein gene (PRNP) may impact susceptibility to prion disease but have not been investigated thus far. Because an investigation of the chicken PRNP can improve the understanding of characteristics related to resistance to prion disease, research on the chicken PRNP is highly desirable. In this study, we investigated the genetic characteristics of the chicken PRNP gene. For this, we performed direct sequencing in 106 Dekalb White chickens and analyzed the genotype and allele frequencies of chicken PRNP gene. We found two insertion and deletion polymorphisms in the chicken PRNP: c.163_180delAACCCAGGGTACCCCCAT and c.268_269insC. The former is a U2 hexapeptide deletion polymorphism. Of the 106 samples, 13 (12.26%) were insertion homozygotes, 89 (83.96%) were heterozygotes, and 4 (3.77%) were deletion homozygotes in c.163_180delAACCCAGGGTACCCCCAT. In the c.268_269insC polymorphism, 102 (96.23%) were deletion homozygotes, and 4 (3.77%) were heterozygotes. Insertion homozygotes of c.268_269insC were not detected. Two polymorphisms were in perfect linkage disequilibrium (LD) with a D' value of 1.0, and three haplotypes were identified. Furthermore, PROVEAN evaluates 163_180delAACCCAGGGTACCCCCAT as 'deleterious' with a score of - 13.173. Furthermore, single nucleotide polymorphisms (SNPs) in the open reading frame (ORF) of the PRNP gene were not found in the chicken. To the best of our knowledge, this was the first report on the genetic variations of the chicken PRNP gene.

Fixed differences in the 3'UTR of buffalo PRNP gene provide binding sites for miRNAs post-transcriptional regulation

Bovine spongiform encephalopathy, a member of transmissible spongiform encephalopathies, has not been reported in buffaloes, Bubalus bubalis. Prion protein (PrP), encoded by the prion protein gene (PRNP), is fundamental in the pathogenesis of transmissible spongiform encephalopathies. We previously showed that buffaloes express more PrP proteins but lower PRNP mRNA than cattle in several pivotal tissues like the obex. Therefore, we sought to establish whether genetic variability in PRNP 3'UTR, mediated by miRNA down-regulation, causes PrP expression differences between cattle and buffaloes. We annotated the 3'UTR of buffalo PRNP gene by 3'RACE experiment. A total of 92 fixed differences in the complete 3'UTR (~ 3 kb) were identified between 13 cattle and 13 buffaloes. Resequencing of UTR-C (g.786-1436) and UTR-B (g.778-1456) fragments confirmed that all mutations except g.1022T in cattle are fixed differences between 147 cattle and 146 buffaloes. In addition, analysis of the variation of ΔG between cattle and buffalo sequences reveals four remarkable differences. Two buffalo-specific insertion sites (a 28-bp insertion and an AG insertion in buffalo 3'UTR of PRNP g.970-997 and g. 1088-1089, respectively) and two mutants (g. 1007-1008 TG→CC) create compatible binding sites for miRNAs in buffalo 3'UTR. This was validated through luciferase reporter assays which demonstrated that miR-125b-5p, miR-132-3p, miR-145-5p, miR-331-3p, and miR-338-3p directly act on the fixed difference sites in buffalo 3'UTR. Additional expressional analyses show that these five miRNAs are coexpressed with PRNP in bovine obex tissues. Our study reveals a miRNAs regulated mechanism explaining the differences in prion expression between cattle and buffalo.

Unraveling the key to the resistance of canids to prion diseases

One of the characteristics of prions is their ability to infect some species but not others and prion resistant species have been of special interest because of their potential in deciphering the determinants for susceptibility. Previously, we developed different in vitro and in vivo models to assess the susceptibility of species that were erroneously considered resistant to prion infection, such as members of the Leporidae and Equidae families. Here we undertake in vitro and in vivo approaches to understand the unresolved low prion susceptibility of canids. Studies based on the amino acid sequence of the canine prion protein (PrP), together with a structural analysis in silico, identified unique key amino acids whose characteristics could orchestrate its high resistance to prion disease. Cell- and brain-based PMCA studies were performed highlighting the relevance of the D163 amino acid in proneness to protein misfolding. This was also investigated by the generation of a novel transgenic mouse model carrying this substitution and these mice showed complete resistance to disease despite intracerebral challenge with three different mouse prion strains (RML, 22L and 301C) known to cause disease in wild-type mice. These findings suggest that dog D163 amino acid is primarily, if not totally, responsible for the prion resistance of canids.

Detection of individuals or whole species resistant to any infectious disease is vital to understand the determinants of susceptibility and to develop appropriate therapeutic and preventative strategies. Canids have long been considered resistant to prion infection given the absence of clinical disease despite exposure to the causal agent. Through extensive analysis of the canine prion protein we have detected a key amino acid that might be responsible for their universal resistance to prion disease. Using in vitro and in vivo models we demonstrated that the presence of this residue confers resistance to prion infection when introduced to susceptible animals, opening the way to develop a new therapeutic approach against these, at present, untreatable disorders.

Transgenic Rabbits Expressing Ovine PrP Are Susceptible to Scrapie

Transmissible spongiform encephalopathies (TSEs) are a group of neurodegenerative diseases affecting a wide range of mammalian species. They are caused by prions, a proteinaceous pathogen essentially composed of PrPSc, an abnormal isoform of the host encoded cellular prion protein PrPC. Constrained steric interactions between PrPSc and PrPC are thought to provide prions with species specificity, and to control cross-species transmission into other host populations, including humans. Transgenetic expression of foreign PrP genes has been successfully and widely used to overcome the recognized resistance of mouse to foreign TSE sources. Rabbit is one of the species that exhibit a pronounced resistance to TSEs. Most attempts to infect experimentally rabbit have failed, except after inoculation with cell-free generated rabbit prions. To gain insights on the molecular determinants of the relative resistance of rabbits to prions, we generated transgenic rabbits expressing the susceptible V136R154Q171 allele of the ovine PRNP gene on a rabbit wild type PRNP New Zealand background and assessed their experimental susceptibility to scrapie prions. All transgenic animals developed a typical TSE 6-8 months after intracerebral inoculation, whereas wild type rabbits remained healthy more than 700 days after inoculation. Despite the endogenous presence of rabbit PrPC, only ovine PrPSc was detectable in the brains of diseased animals. Collectively these data indicate that the low susceptibility of rabbits to prion infection is not enciphered within their non-PrP genetic background.