Procedures for discriminating scrapie from bovine spongiform encephalopathy (BSE) in sheep are relevant to ascertain whether BSE has entered the sheep population. This study was aimed at ...investigating whether the suitability of an official EU discriminative method is affected by the sheep PrP genotype and route of infection.
The susceptibility of sheep to scrapie is under the control of the host's prion protein (PrP gene and is also influenced by the strain of the agent. PrP polymorphisms at codons 136 (A/V), 15 (R/H) ...and 171 (Q/R/H) are the main determinants of susceptibility/resistance of sheep to classical scrapie. They are combined in four main variants of the wild-type ARQ allele: VRQ, AHQ, ARH and ARR. Breeding programmes have been undertaken on this basis in the European Union and th USA to increase the frequency of the resistant ARR allele in sheep populations. Herein, we report th results of a multi-flock study showing the protective effect of polymorphisms other than those a codons 136, 154 and 171 in Sarda breed sheep. All ARQ/ARQ affected sheep (n = 154) and 37 negative ARQ/ARQ controls from four scrapie outbreaks were submitted to sequencing of the Pr gene. The distribution of variations other than those at the standard three codons, between scrapie cases and negative controls, was statistically different in all flocks. In particular, the AT(137)RQ an ARQK(176) alleles showed a clear protective effect. This is the first study demonstrating a protective influence of alleles other than ARR under field conditions. If further investigations in other sheep breeds and with other scrapie sources confirm these findings, the availability of various protective alleles in breeding programmes of sheep for scrapie resistance could be useful in breeds with a low frequency of the ARR allele and would allow maintaining a wider variability of the PrP gene.
The bank vole is a rodent susceptible to different prion strains from humans and various animal species. We analyzed the transmission features of different prions in a panel of seven rodent species ...which showed various degrees of phylogenetic affinity and specific prion protein (PrP) sequence divergences in order to investigate the basis of vole susceptibility in comparison to other rodent models. At first, we found a differential susceptibility of bank and field voles compared to C57Bl/6 and wood mice. Voles showed high susceptibility to sheep scrapie but were resistant to bovine spongiform encephalopathy, whereas C57Bl/6 and wood mice displayed opposite features. Infection with mouse-adapted scrapie 139A was faster in voles than in C57Bl/6 and wood mice. Moreover, a glycoprofile change was observed in voles, which was reverted upon back passage to mice. All strains replicated much faster in voles than in mice after adapting to the new species. PrP sequence comparison indicated a correlation between the transmission patterns and amino acids at positions 154 and 169 (Y and S in mice, N and N in voles). This correlation was confirmed when inoculating three additional rodent species: gerbils, spiny mice and oldfield mice with sheep scrapie and 139A. These rodents were chosen because oldfield mice do have the 154N and 169N substitutions, whereas gerbil and spiny mice do not have them. Our results suggest that PrP residues 154 and 169 drive the susceptibility, molecular phenotype and replication rate of prion strains in rodents. This might have implications for the assessment of host range and molecular traceability of prion strains, as well as for the development of improved animal models for prion diseases.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The susceptibility of sheep to scrapie is under the control of the host’s prion protein (PrP) gene and is also influenced by the strain of the agent. PrP polymorphisms at codons 136 (A/V), 154 (R/H) ...and 171 (Q/R/H) are the main determinants of susceptibility/resistance of sheep to classical scrapie. They are combined in four main variants of the wild-type ARQ allele: VRQ, AHQ, ARH and ARR. Breeding programmes have been undertaken on this basis in the European Union and the USA to increase the frequency of the resistant ARR allele in sheep populations. Herein, we report the results of a multi-flock study showing the protective effect of polymorphisms other than those at codons 136, 154 and 171 in Sarda breed sheep. All ARQ/ARQ affected sheep (
n
= 154) and 378 negative ARQ/ARQ controls from four scrapie outbreaks were submitted to sequencing of the PrP gene. The distribution of variations other than those at the standard three codons, between scrapie cases and negative controls, was statistically different in all flocks. In particular, the AT
137
RQ and ARQK
176
alleles showed a clear protective effect. This is the first study demonstrating a protective influence of alleles other than ARR under field conditions. If further investigations in other sheep breeds and with other scrapie sources confirm these findings, the availability of various protective alleles in breeding programmes of sheep for scrapie resistance could be useful in breeds with a low frequency of the ARR allele and would allow maintaining a wider variability of the PrP gene.
The susceptibility of sheep to scrapie is under the control of the host's prion protein (PrP) gene and is also influenced by the strain of the agent. PrP polymorphisms at codons 136 (A/V), 154 (R/H) ...and 171 (Q/R/H) are the main determinants of susceptibility/resistance of sheep to classical scrapie. They are combined in four main variants of the wild-type ARQ allele: VRQ, AHQ, ARH and ARR. Breeding programmes have been undertaken on this basis in the European Union and the USA to increase the frequency of the resistant ARR allele in sheep populations. Herein, we report the results of a multi-flock study showing the protective effect of polymorphisms other than those at codons 136, 154 and 171 in Sarda breed sheep. All ARQ/ARQ affected sheep (n = 154) and 378 negative ARQ/ARQ controls from four scrapie outbreaks were submitted to sequencing of the PrP gene. The distribution of variations other than those at the standard three codons, between scrapie cases and negative controls, was statistically different in all flocks. In particular, the AT137RQ and ARQK176 alleles showed a clear protective effect. This is the first study demonstrating a protective influence of alleles other than ARR under field conditions. If further investigations in other sheep breeds and with other scrapie sources confirm these findings, the availability of various protective alleles in breeding programmes of sheep for scrapie resistance could be useful in breeds with a low frequency of the ARR allele and would allow maintaining a wider variability of the PrP gene.
ABSTRACT Streptolysin O is a potent pore-forming toxin produced by group A Streptococcus. The aims of the present study were to dissect the relative contributions of different structural domains of ...the protein to hemolytic activity, to obtain a detoxified form of streptolysin O amenable to human vaccine formulation, and to investigate the role of streptolysin O-specific antibodies in protection against group A Streptococcus infection. On the basis of in silico structural predictions, we introduced two amino acid substitutions, one in the proline-rich domain 1 and the other in the conserved undecapeptide loop in domain 4. The resulting streptolysin O derivative showed no toxicity, was highly impaired in binding to eukaryotic cells, and was unable to form organized oligomeric structures on the cell surface. However, it was fully capable of conferring consistent protection in a murine model of group A Streptococcus infection. When we engineered a streptococcal strain to express the double-mutated streptolysin O, a drastic reduction in virulence as well as a diminished capacity to kill immune cells recruited at the infection site was observed. Furthermore, when mice immunized with the toxoid were challenged with the wild-type and mutant strains, protection only against the wild-type strain, not against the strain expressing the double-mutated streptolysin O, was obtained. We conclude that protection occurs by antibody-mediated neutralization of active toxin. IMPORTANCE We present a novel example of structural design of a vaccine antigen optimized for human vaccine use. Having previously demonstrated that immunization of mice with streptolysin O elicits a protective immune response against infection with group A Streptococcus strains of different serotypes, we developed in this study a double-mutated nontoxic derivative that represents a novel tool for the development of protective vaccine formulations against this important human pathogen. Furthermore, the innovative construction of an isogenic strain expressing a functionally inactive toxin and its use in infection and opsonophagocytosis experiments allowed us to investigate the mechanism by which streptolysin O mediates protection against group A Streptococcus. Finally, the ability of this toxin to directly attack and kill host immune cells during infection was studied in an air pouch model, which allowed parallel quantification of cellular recruitment, vitality, and cytokine release at the infection site.
The next decade affords tremendous opportunity to achieve the goals of Galactic archaeology. That is, to reconstruct the evolutionary narrative of the Milky Way, based on the empirical data that ...describes its current morphological, dynamical, temporal and chemical structures. Here, we describe a path to achieving this goal. The critical observational objective is a Galaxy-scale, contiguous, comprehensive mapping of the disk's phase space, tracing where the majority of the stellar mass resides. An ensemble of recent, ongoing, and imminent surveys are working to deliver such a transformative stellar map. Once this empirical description of the dust-obscured disk is assembled, we will no longer be operationally limited by the observational data. The primary and significant challenge within stellar astronomy and Galactic archaeology will then be in fully utilizing these data. We outline the next-decade framework for obtaining and then realizing the potential of the data to chart the Galactic disk via its stars. One way to support the investment in the massive data assemblage will be to establish a Galactic Archaeology Consortium across the ensemble of stellar missions. This would reflect a long-term commitment to build and support a network of personnel in a dedicated effort to aggregate, engineer, and transform stellar measurements into a comprehensive perspective of our Galaxy.
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