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Eight monoclonal antibodies directed against the hog cholera virus (HCV) strain Alfort/187 and displaying broad cross-reactivity with other HCV strains were characterized. An enzyme immunoassay on fixed monolayers of porcine or bovine cells infected with 14 different strains and isolates of HCV and 12 bovine viral diarrhea viruses (BVDV), respectively, showed that all antibodies reacted with HCV only. Seven antibodies recognized all HCV tested, thus indicating that they were directed against conserved epitopes. All antibodies neutralized the homologous strain and different patterns of the other HCV tested. Radioimmunoprecipitation analysis showed that the monoclonal antibodies were directed against a doublet of 56-60 kDa, presumably representing the major envelope glycoprotein of HCV. The results of reciprocal antibody blocking assays allowed the mapping of two distinct conserved antigenic domains on this protein.

Summary Pigs infected with bovine virus diarrhea (BVD) virus may develop a high antibody titre after challenge with hog cholera (HC) virus. In the present study weaners were inoculated intranasally first with the cytopathogenic BVD virus strain “Osloss” and a non‐cytopathogenic BVD virus isolate, respectively, followed 6–8 weeks later by challenge with the virulent hog cholera virus strain “Alfort”. In the first transmission experiment clinical signs did not develop except for slight transient fever in one of the animals. Antibody titres against the homologous strain rose quickly within the first 4 weeks, whereas the titres against the heterologous strains NADL, “Alfort” and “331” increased more slowly but increased rapidly after challenge. The highest mean antibody titres after challenge developed against the homologous BVD virus strain used for primary inoculation. Curves showing the antibody kinetics against the heterologous strains were very similar, due to the relationship between BVD and HC virus strains. In another experiment a group of 10 weaners received a non‐cytopathogenic BVD field strain by the same route and was challenged with HC strain “Alfort/187” six weeks later. Fourteen days after challenge in pigs showed mean neutralizing antibody titres against the homologous BVD strain of more than 1:10,000 with peak titres of 1:30,000. The heterologous mean neutralizing antibody titre against strain NADL did not exceed 1:2,000 and the mean antibody titres against HC strains “Alfort/187” and “331” remained below 1:640. Zusammenfassung Ausbildung neutralisierender Antikörper bei Schweinen nach aufeinander folgender Verabreichung von bovinem Virusdiarrhoe‐Virus und Europäischem Schweinepest‐Virus Schweine, die mit bovinem Virusdiarrhoe (BVD)‐Virus infiziert wurden, können hohe Antikörper‐Titer nach Belastung mit dem Europäischen Schweinepest (ESP)‐Virus ausbilden. Bei den vorliegenden Untersuchungen wurden junge Schweine intranasal zuerst mit dem zytopathogenen BVD‐Stamm “Osloss” oder einem nicht zytopathogenem BVD‐Virusisolat inokuliert und 6–8 Wochen später mit dem virulenten Schweinepest‐Virusstamm “Alfort” belastet. Beim ersten Übertragungs‐Experiment entwickelten sich keine klinischen Krankheitszeichen, außer leichtem vorübergehendem Fieber bei einem der Tiere. Die Antikörpertiter gegen den homologen Virusstamm stiegen schnell innerhalb der ersten 4 Wochen an, wogegen die Titer gegen die heterologen Virusstämme “NADL”, “Alfort” und “331” insgesamt langsamer, aber äußerst schnell nach der Belastung anstiegen. Die höchsten mittleren Antikörpertiter nach der Belastung waren gegen den homologen BVD‐Virus‐stamm, der initial zur Inokulation verwendet wurde, ausgebildet. Die Verlaufskurven zur Demonstration der Antikörper‐Kinetik gegen die heterologen Virusstämme waren sich ähnlich auf Grund der Verwandtschaft zwischen BVD‐ und ESP‐Virusstämmen. In einem anderen Versuch erhielten 10 Läufer einen nicht zytopathogenen BVD‐Feldstamm gleichermaßen appliziert und wurden mit dem ESP‐Stamm “Alfort/187” 6 Wochen später...

The clinical course, post mortem lesions as well as virological and serological results after simultaneous intranasal inoculation of pigs with bovine viral diarrhoea virus (BVDV) and hog cholera virus (HCV) are described. Five groups of four weaners received constant doses of BVDV strain OSLOSS/2482 and tenfold decreasing doses of HCV strain ALFORT/187. Doses of 1,000 and 100 TCIDso of HCV in groups A and I3 of pigs led to fever and severe clinical signs in all animals of two groups, whereas at higher dilution of inoculum two, three or four animals survived without any clinical signs in the respective groups (C-E). Leucocyte samples taken from febrile animals and from normal pigs on five consecutive days were inoculated into both fetal calf kidney (FCK) and PK(15) cell cultures. Virus isolates were differentiated with BVDV and HCV specific monoclonal antibodies. HCV viraemia was detected in febrile animals exclusively, and BVDV viraemia occurred in not affected animals on days 3 to 7 post inoculation. Neutralizing antibodies (nab) against BVDV appeared before HCV nab in surviving animals of groups C and D after receiving low doses of H C V (10 or 1 TCIDS0). No BVDV nab were detected in group E that had received such a high dilution of HCV in addition to BVDV that theoretically no HCV was applied.

Summary Five groups of weaner pigs were intranasally inoculated with constant doses of bovine viral diarrhoea virus (BVDV) strain OSLOSS/2482. Four weeks post primary inoculation (p. p. i.) the animals were intranasally challenged with decreasing doses of hog cholera virus (HCV) strain Alfort/ 187. Clinical signs were not observed apart from a short febrile period (2 days, > 40 °C) in one animal. Another animal died intercurrently without showing any pathological signs. Virus isolation from leucocyte samples taken regularly during one week post challenge detected HC viraemia in most animals that had received HCV doses > 100 TCID50 per animal. Using monoclonal antibody (mab) analysis all isolates obtained were proven to be HCV. Serological investigations using the virus neutralization test (VNT) yielded HC neutralizing antibodies in all groups with higher titres in those animals having received HCV doses > 100 TCID50. However, HCV specific neutralizing antibodies never exceeded the BVDV antibody titre. A complex trapping blocking (CTB) ELISA applying a HCV specific mab detected HCV specific antibodies in animals that had gone through HC viraemia while discriminating BVDV specific antibodies.