No abstract

A novel porcine deltacoronavirus (PdCV) was first discovered in Ohio and Indiana in February 2014, rapidly spread to other states in the United States and Canada, and caused significant economic loss in the swine industry. The origin and virulence of this novel porcine coronavirus are not known. Here, we characterized U.S. PdCV isolates and determined their virulence in gnotobiotic and conventional piglets. Genome analyses revealed that U.S. PdCV isolates possess unique genetic characteristics and share a close relationship with Hong Kong and South Korean PdCV strains and coronaviruses (CoVs) of Asian leopard cats and Chinese ferret-badgers. The PdCV-positive intestinal content (Ohio CVM1) and the cell culture-adapted PdCV Michigan (MI) strain were orally inoculated into gnotobiotic and/or conventional piglets. Within 1 to 3 days postinfection, profuse watery diarrhea, vomiting, and dehydration were observed. Clinical signs were associated with epithelial necrosis in the gastric pits and small intestine, the latter resulting in severe villous atrophy. Mild interstitial pneumonia was identified in the lungs of PdCV-infected piglets. High levels of viral RNA (8 to 11 log RNA copies/g) were detected in intestinal tissues/luminal contents and feces of infected piglets, whereas moderate RNA levels (2 to 5 log RNA copies/g) were detected in blood, lung, liver, and kidney, indicating multisystemic dissemination of the virus. Polyclonal immune serum against PdCV but not immune serum against porcine epidemic diarrhea virus (PEDV) reacted with PdCV-infected small-intestinal epithelial cells, indicating that PdCV is antigenically distinct from PEDV. Collectively, we demonstrate for the first time that PdCV caused severe gastrointestinal diseases in swine.

Abstract. One-day-old gnotobiotic piglets were inoculated intranasally with in vitro passaged porcine circovirus 1 (PCV-1), PCV-2, and porcine parvovirus (PPV) alone or in combination (PCV-1/PCV-2, PCV-1/PPV, and PCV-2/PPV). Piglets were evaluated for 1) the development of porcine postweaning multisystemic wasting syndrome (PMWS), 2) distribution of viral antigens by immunochemistry, and 3) viremia and the presence of viral DNA in nasal and ocular secretions and feces. All single agent-infected piglets and piglets infected with PCV-1/PCV-2 or PCV-1/PPV were clinically asymptomatic. They were transiently viremic and seroconverted to homologous virus(es). At termination of the study on postinfection day (PID) 35, microscopic lesions were restricted to focal inflammatory cell infiltrates in livers and myocardia. One piglet given PCV-1/PPV was PPV viremic for 2 weeks after infection and had lymphangiectasia of the spiral and descending colon associated with granulomatous inflammation. All four PCV-2/PPV-inoculated piglets developed PMWS, characterized by sudden onset of depression and anorexia, icterus, and submucosal edema. One piglet became moribund on PID 27, and the remaining three piglets were euthanatized between PID 27 and PID 30 because of severe disease. Lymph nodes were small and the livers were mottled. Disseminated angiocentric granulomatous inflammation was present in all tissues examined except the brain. Multiple lightly basophilic intracytoplasmic inclusion bodies were identified in macrophages and histiocytes. PCV-2 antigen was widely distributed within macrophages; PPV antigen was sparse. Hepatocellular necrosis and bile retention were prominent. PCV-2 DNA was identified in ocular, fecal, and nasal secretions. Terminal sera contained antibodies to PPV (4/4) and PCV-2 (3/ 4). Production of PMWS in gnotobiotic swine appears to require PCV-2 and additional infectious agents such as PPV for full disease expression in gnotobiotic piglets.

Abstract. Neonatal gnotobiotic piglets were inoculated with tissue homogenates and low-and highpassage cell culture material to determine if the lesions of the newly described porcine postweaning multisystemic wasting syndrome (PMWS) could be reproduced. For this, 17 3-day-old gnotobiotic piglets were inoculated intranasally with pelleted chloroform-treated, filtered extracts from cell cultures, filter-sterilized homogenates of lymphoid tissue from PMWS-affected piglets, or control materials. Piglets were maintained in germ-free isolators for up to 5 weeks after infection prior to euthanasia and collection of samples for analysis. All piglets inoculated with the viral inocula developed lesions typical of PMWS, including generalized lymphadenopathy, hepatitis, nephritis, interstitial pneumonia, myocarditis, and gastritis. Porcine circovirus (PCV), as well as porcine parvovirus (PPV), was detected in tissues by virus reisolation, polymerase chain reaction analysis, or immunohistochemistry. All infected piglets developed moderate to high titers of antibody to PCV and moderate titers to PPV. No lesions, virus, or virus-specific antibodies were detected in sham-inoculated or uninoculated control piglets. These studies demonstrate that the lesions of PMWS can be experimentally reproduced in gnotobiotic piglets using filterable viral agents derived from pigs with PMWS and provide an experimental basis for further investigation into the pathogenesis and control of this emerging infectious disease in swine.

Summary. Non-motile variants of Helicobacterpylori (strain 26695) occurred with a frequency of 1.6 (SD 0.4) x lo-* variants/cell/division cycle, and reversion to the motile form occurred with a frequency of < lo-' variants/cell/division cycle. The two forms remained > 90 YO pure for up to 50 cell divisions and differed only in the presence or absence of motility and flagella. Bacteria were recovered from nine of 10 gnotobiotic piglets inoculated orally with motile H. pylori, but from only two of eight inoculated with the non-motile variant. The motile form survived for 21 days in infected piglets, but the non-motile variant survived for only 6 days. Bacteria recovered from piglets inoculated with the non-motile variant were non-motile. These data support the hypothesis that motility is a colonisation factor for H . pylori.