Didier Guillemot and colleagues describe the evaluation of a nationwide programme in France aimed at decreasing unnecessary outpatient prescriptions for antibiotics. The campaign was successful, particularly in reducing prescriptions for children.

A key feature of prion encephalopathies is the accumulation of a misfolded form of the host glycoprotein PrP. Cell-free and cell culture studies have shown that the efficiency of conversion of PrP into the disease-associated form is influenced by its amino acid sequence and also by its carbohydrate moiety. Here, we characterize four novel glycoform-dependent monoclonal antibodies raised against prokaryotic recombinant sheep PrP. We demonstrate that these antibodies discriminate the PrP monoglycosylated species, since two of them recognize molecules that have the first Asn glycosylation site occupied (mono1) while the other two recognize molecules glycosylated at the second site (mono2). Remarkably, the recognition of PrP by the anti-mono2 antibodies was strongly influenced by the amino acid present at position 171, i.e., either Gln or Arg. This polymorphism is known to be the main determinant of susceptibility and resistance to scrapie in sheep. Altogether, our findings lead us to propose that each glycan chain controls the accessibility of PrP determinants located close upstream from their attachment site. The monoglycoform-assigned and the allotype-restricted antibodies described here, the first to date, should provide further opportunities to investigate the involvement of each glycan chain in PrP conversion in relation to prion strain diversity and the basis of the resistance conferred by the Arg-171 amino acid.

Prion diseases are fatal neurodegenerative disorders of animals and humans that are characterized by the conversion of the host-encoded prion protein (PrP) to an abnormal isoform. In several species, including humans, polymorphisms in the gene encoding the PrP protein tightly control susceptibility of individuals toward this disease. In the present study we show that Rov cells expressing an ovine PrP allele ( VRQ PrP) associated with high susceptibility of sheep to scrapie were very sensitive to sheep prion transmission and replicated the agent to high titers. In contrast, we did not find any evidence of infection when Rov cells expressed similar levels of a PrP variant ( ARR PrP) linked to resistance. Our data provide the first direct evidence that natural PrP polymorphisms may affect prion susceptibility by controlling prion replication at the cell level. The study of how PrP polymorphisms influence the genetic control of prion propagation in cultured Rov cells may help elucidate basic mechanisms of prion replication.Transmissible spongiform encephalopathies (TSEs) are fatal degenerative disorders of the central nervous system, which naturally affect animals and humans (for a review, see reference 8). TSEs are associated with the posttranslational conversion of the host-encoded prion protein (PrP) to a conformationally altered form (PrPsc). The causative infectious agents, or prions, are thought to be PrPsc itself or a precursor of it (for reviews, see references 22 and 30).In several species, including mice, sheep, and humans, susceptibility to prion diseases is tightly controlled by the host. The major genetic determinants controlling the length of the incubation period are polymorphisms of Prnp, the PrP-encoding gene. In humans, homozygosity for methionine at the polymorphic residue 129 is associated with high susceptibility to the new variant form of Creutzfeldt-Jakob disease (14), whereas homozygosity for valine is overrepresented among early cases of iatrogenic Creutzfeldt-Jakob disease in the United Kingdom (7). In sheep, variations at three amino acid positions of PrP are predominantly linked to scrapie susceptibility (for a review, see reference 17). The 136 V 154 R 171 Q allele (V, R, and Q stand for valine, arginine, and glutamine, respectively) is associated with extremely high susceptibility to scrapie: in naturally infected flocks, sheep homozygous for VRQ PrP are almost always affected with scrapie. In contrast, the 136 A 154 R 171 R variant (A for alanine) is associated with resistance to the clinical disease. No clinical scrapie case has been reported in hundreds of sheep homozygous for ARR PrP from naturally infected flocks in Europe and the United States, and a single case was reported in Japan (12). Experimental challenge of VRQ-and ARR-encoding sheep with ovine and bovine prions further substantiated the dramatic opposite effects of these two alleles on disease susceptibility, since sheep homozygous for ARR PrP could not be infected by either agent (11). Although the link between specific ...

During prion infections, the cellular glycosylphosphatidylinositol-anchored glycoprotein PrP is converted into a conformational isoform. This abnormal conformer is thought to recruit and convert the normal cellular PrP into a likeness of itself and is proposed to be the infectious agent. We investigated the distribution of the PrP protein on the surface of Rov cells, an epithelial cell line highly permissive to prion multiplication, and we found that PrP is primarily expressed on the apical side. We further show that prion transmission to Rov cells is much more efficient if infectivity contacts the apical side, indicating that the apical and basolateral sides of Rov cells are not equally competent for prion infection and adding prions to the list of the conventional infectious agents (viruses and bacteria) that infect epithelial cells in a polarized manner. These data raise the possibility that apically expressed PrP may be involved in this polarized process of infection. This would add further support for a crucial role of PrP at the cell surface in prion infection of target cells.The host-encoded PrP protein is essential for prion multiplication. Inhibiting its expression renders susceptible tissues or cells incapable of replicating prions (10,33). PrP is a glycoprotein of unknown function anchored to the external leaflet of the plasma membrane through a glycosylphosphatidylinositol (GPI) anchor (38). Like other membrane proteins, PrP is synthesized and translocated into the rough endoplasmic reticulum and then transits through the Golgi before being delivered to the plasma membrane (reviewed in references 13 and 14). In contrast to other GPI proteins, however, PrP does not remain at the cell surface for long periods. It is rapidly endocytosed and constitutively cycles between endocytic compartments and the plasma membrane (21,28,35,40). PrP undergoes numerous posttranslational modifications, including cleavage of the signal peptide, addition of the GPI anchor, formation of a single intrachain disulfide bond, N-glycosylation on two possible glycosylation sites, and also posttranslational cleavages during endocytosis and recycling of the protein (13,14).During prion pathogenesis, multiplication of the infectious agent occurs concomitantly with the conversion of the PrP protein into a detergent-insoluble, protease-resistant isoform called PrPsc (reviewed in reference 30). The most widely accepted hypothesis is that PrPsc, or a precursor of it, is the infective agent (29); introduced into the organism, the abnormal conformer is thought to recruit and convert the cellular PrP into a likeness of itself. However, the molecular details of PrP conversion, including possible cofactor requirements, are unclear (8). At the cellular level, too, a number of uncertainties remain. Analysis by immunotechniques indicates that accumulated abnormal PrP is widely distributed in cultured infected cells (13, 14); however, the initial interaction of exogenous abnormal PrP with a target cell is poorly characterized, and the subcellul...