SUMMARYThe ultrastructure of feline infectious peritonitis virus in cultured feline embryonic lung cells is reported. Feline embryonic lung cells were infected with feline infectious peritonitis virus and studied by transmission electron microscopy. The virus was not apparent in the cultured cells until 24 h after infection when it occurred in the endoplasmic reticulum, perinuclear space, Golgi apparatus, free in the cytoplasm, in large vacuoles in the cytoplasm and outside the cell membrane. The virus possessed typical coronavirus morphology and was produced by budding into the endoplasmic reticulum. There was no evidence to indicate that this virus budded through the cell membrane. Multinucleate giant cells were formed by infection of the cultured cells with the virus. The host cells were destroyed by the virus and phagocytosed by apparently healthy cells.
Significant antibody response to feline panleucopaenia virus was present 2 months after vaccination with modified live virus vaccine and persisted for 4 years.
Seventy‐two hours after the administration of a single dose of high passage living attenuated feline panleucopaenia vaccine, cats were protected against experimental challenge and even at 48 hours the effects of challenge were reduced. The antibody response persisted at high titre for at least 23 months. Antibody titres following vaccination were better than those associated with virulent virus. The attenuation of virulent feline panleucopaenia virus by serial passage in feline embryonic cell culture has produced a living vaccine which is both antigenic and immunogenic.
Résumé. Soixante‐douze heures après l'administration d'une seule dose du vaccin pour maladie des jeunes chats, vaccin vivant atténué à passage élévé, les chats étaient protégés contre des tests expérimentaux et les effets des tests étaient même réduits à 48 heures. La réponse anticorps a persisté à titre élévé pendant au moins 23 mois. Des titres anticorps suivant la vaccination étaient meilleurs que ceux associés avec le virus virulent. L'atténuation du virus virulent pour la maladie des jeunes chats, par passage en série dans la culture des cellules embryonnaires chez les félins, a produit un vaccin vivant qui est à la fois antisomatogtne et immunogène.
Zusammenfassung. Zweiundsiebzig Stunden nach der Darreichung von hoher Passage leben‐derattenuierter Katzenfieber‐ (Agranulozytose) Vakzine waren Katzen gegen experimentale Immunitätsteste geschützt und selbst nach 48 Stunden waren die Auswirkungen des Immunitätsteste reduziert. Die Schutzstoffreaktion hielt bei hohem Titer für wenigstens 23 Monate an. Schutzstofftiter die einer Impfung folgten waren besser als jene die mit virulentem Virus verbunden sind. Die Verminderung von virulentem Katzenfieber‐ (Agranulozytose) Virus durch Reihenpassage in katzenembryonaler Zellenkultur hat eine lebende Vakzine produziert, die antigen sowohl wie immunisierend ist.
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