Immunization of day-old chicks having maternally derived antibodies against infectious bronchitis: degree of protection as monitored by ciliary activity after intratracheal challenge.

One-day-old chicks with maternally derived antibodies were vaccinated against infectious bronchitis (IB) with 3000 EID50 of the IB vaccine virus designated H120. The degree of protection induced by intranasal-eye drop (IE) vaccination was compared to that achieved by spray (S) vaccination. The protection afforded by vaccination was monitored by intratracheal challenge with IBV strain M-41 (clinical signs, ciliary activity in tracheal explants, virus isolation) and by serological tests (ovoneutralization, microneutralization in cell culture, haemagglutination inhibition (HI) test, ELISA). Intranasal-eye drop vaccination provided protection against intratracheal challenge. Immunity developed around 31 days of age. Spray vaccination failed to give protection against challenge by the same route. No difference was demonstrable in effectiveness between the two routes of vaccination by serological tests. No elevation of the antibody level occurred in either group. The level of maternally derived antibodies declined with age.

Isolation and characterization of new infectious bronchitis virus variants in Hungary.

Two agents not agglutinating chicken erythrocytes were isolated, one in each of two flocks, from organ samples and tracheal swabs taken from 4- to 7-week-old chicks of 8 broiler flocks experiencing respiratory signs. Virus isolation was done in embryonated SPF hen's eggs. Morphological changes of the embryos, appearing as dwarfing or curling into a spherical form, usually occurred in the 3rd or 4th passage on postinoculation (PI) days 5-9. Some embryos had swollen kidneys covered with urate. Electron microscopy of ultrathin sections of these kidneys revealed the presence of virions reminiscent of coronaviruses. Similar viral particles were seen in resuspended pellets of isolates concentrated by ultracentrifugation. Based on embryo changes, cross-neutralization tests with type-specific antisera, physicochemical tests, results obtained in cell cultures, and electron microscopic findings the two isolates were identified as infectious bronchitis virus (IBV). By cross-neutralization tests the isolates differed from IBV reference strains M41 and H52 and can be considered distinct variants. Elucidation of their epizootiological role requires further investigations.

[Requirements of rabbit-adapted swine fever vaccine]. / Anforderungen an die kaninchenadaptierte Schweinepestvakzine.

Studies were conducted into the demands made on both harmlessness and effectiveness of SUVAC, a swine fever vaccine prepared from strain "C", a rabbit-adapted Chinese virus strain. The following findings were obtained: --The vaccine strain was attenuated to an extent by which it could be used without serum. --The vaccine was harmless even with immunodepressor action. Its immunogenicity was good, and live weight growth of the animals was not impaired. --The vaccine was harmless to the foetuses. --Very little virus was excreted by immunised pigs. --Vaccine attenuation was of high stability, and virulence was not even increased after six passages in pigs. --Between 50 and 100 immunising units were contained in one vaccine dose, and piglets immunised at the age of six weeks were protected after three months against an experimental infectino which was fatal to susceptible pigs. --Virus inoculated into PK 15-cell line proved negative in the first passage in response to immunofluorescence testing.