The causative agents of foot-and-mouth disease (FMD) are small icosahedral viruses of theAphthovirus group within the Picornaviridae family. There is no evidence that these viruses infect cells of the immune system or otherwise interfere detrimentally with their function; additionally, it has not been possible to relate cytotoxicity reactions against virus-infected cells to the efficacy of the immune response against FMD virus infection. In contrast, there is a close association between FMD virus antibody and the protective immune response (10, 14, 15, 20, 24, 25, 29-32). Induction of this antibody is dependent on the structure of the viral antigenic sites (7-9, 11, 18) and on the concomitant presence of Tb-lymphocyte epitopes (4, 5, 7, 8), although a Ti-lymphocyteindependent response has been reported (2). Recent work by Piatti et al. (26) showed that the immune response induced by FMD virus was only Th-lymphocyte dependent when low doses of antigen were used. This latter

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Viral proteins of porcine epidemic diarrhoea virus (PEDV) were extracted from the cytoplasm of infected Vero cells using hypotonic conditions and a non-ionic detergent. Both the pH and the NaCl concentration of the extraction buffer were varied in attempts to increase the solubility of the virion spike glycoproteins (S-protein) and of the nucleocapsid proteins (N-protein). Monoclonal antibodies, hyperimmune sera and convalescent pig sera were used to identify and monitor these proteins by immunoprecipitation and Western blots. The solubility of the S-protein was optimal at pH 4, whereas that of the N-protein was optimal at pH 9. Consequently, it was possible to enrich for either S-protein or N-protein; increases in the NaCl concentration of the buffer were of no advantage in this respect. Enriched preparations of the S-protein and N-protein were used as ELISA antigen for the S-ELISA and N-ELISA, respectively. The S-ELISA proved to be the more effective of the two immunoassays. Antibodies against S-protein remained detectable for longer periods of time than anti-N-protein antibodies in the sera of PEDV-infected pigs. Using this ELISA of increased sensitivity, it was observed that only a small number of farms in Switzerland had been infected with PEDV.

Abstract. Different types of transmissible spongiform encephalopathies (TSEs) affect sheep and goats. In addition to the classical form of scrapie, both species are susceptible to experimental infections with the bovine spongiform encephalopathy (BSE) agent, and in recent years atypical scrapie cases have been reported in sheep from different European countries. Atypical scrapie in sheep is characterized by distinct histopathologic lesions and molecular characteristics of the abnormal scrapie prion protein (PrP sc ). Characteristics of atypical scrapie have not yet been described in detail in goats. A goat presenting features of atypical scrapie was identified in Switzerland. Although there was no difference between the molecular characteristics of PrP sc in this animal and those of atypical scrapie in sheep, differences in the distribution of histopathologic lesions and PrP sc deposition were observed. In particular the cerebellar cortex, a major site of PrP sc deposition in atypical scrapie in sheep, was found to be virtually unaffected in this goat. In contrast, severe lesions and PrP sc deposition were detected in more rostral brain structures, such as thalamus and midbrain. Two TSE screening tests and PrP sc immunohistochemistry were either negative or barely positive when applied to cerebellum and obex tissues, the target samples for TSE surveillance in sheep and goats. These findings suggest that such cases may have been missed in the past and could be overlooked in the future if sampling and testing procedures are not adapted. The epidemiological and veterinary public health implications of these atypical cases, however, are not yet known.