Vaccination of chicken embryos with escape mutants of La Sota Newcastle disease virus induces a protective immune response.

To reduce the embryonic pathogenicity of Newcastle disease virus (NDV), escape mutants of the La Sota strain were produced with selected monoclonal antibodies. Immunoselection resulted in the elimination of an epitope by single amino acid substitution (F and HN molecule) or in a conformational change (HN molecule). The embryonic pathogenicity of these escape mutants was reduced and their dose was optimised for in ovo vaccination.

Phylogenetic analysis of fowl adenoviruses.

The sequences of the L1 loop of the hexon protein from representative fowl adenovirus (FAdV) strains of the different European and American collections were determined and compared. This study highlighted the lack of consensus in the numbering of the individual serotypes between the American and the European classifications. An identification system is proposed based on restriction fragment length polymorphism of the hexonA/hexonB polymerase chain reaction product.

Evolution of pigeon Newcastle disease virus strains.

Twenty-seven Newcastle disease virus isolates obtained during the years 1998 and 1999 from racing pigeons were shown to be antigenically indistinguishable from the pigeon paramyxovirus type 1 (PPMV-1) viruses isolated in the years 1983 and 1984. Partial sequencing of 240 base pairs of the F gene demonstrated at least 94.7% identity at the nucleotide level between isolates from 1983 and 1984, and more recent viruses isolated in 1998 and 1999.

Polymerase chain reaction combined with restriction enzyme analysis for detection and differentiation of fowl adenoviruses.

A polymerase chain reaction combined with restriction enzyme analysis was developed for detection and differentiation of all 12 fowl adenovirus (FAdV) serotypes representing the five fowl adenovirus (A to E) species. For primer design, the published sequences of the hexon proteins of FAdV1, FAdV8 and FAdV9 were aligned and conserved regions in the two pedestal regions adjacent to the L1 loop region were determined. A primer pair (hexon A/hexon B) was constructed and was shown to amplify approximately 900 bp of the hexon gene including the L1 loop region.

Epidemiology of infectious bronchitis virus in Belgian broilers: a retrospective study, 1986 to 1995.

Infectious bronchitis virus (IBV) was isolated from each of 236 broiler flocks that had respiratory infection (86%), impaired growth, enteritis and/or nephritis (14%), over a 10-year period from 1986 to 1995 in Belgium. Among them, 65% of the investigated flocks had not been vaccinated against infectious bronchitis. Type-specific reverse transcriptase polymerase chain reactions (RT-PCRs) were used after propagation of the isolates in embryonated eggs in order to detect and differentiate Massachusetts, D274, B1648 and 793/B types.

Acute pancreatitis in chickens due to non-virulent Newcastle disease virus.

A non-virulent Newcastle disease virus (strain APMV-1 96/89 VB) was isolated from a broiler chicken from a backyard flock. Using monoclonal antibodies, the virus was shown to be different from the vaccinal virus strains Hitchner, La Sota and Ulster. The virus was shown to replicate in the pancreas of one-day-old specific pathogen-free chickens infected orally, and the histological lesions observed in the pancreas of chickens inoculated with the fourth chicken passage of the virus five to nine days after infection were consistent with an acute pancreatitis.

An ELISA for the detection of antibodies to avian nephritis virus and related entero-like viruses.

An ELISA for the detection of antibodies against avian nephritis virus (ANV) and related entero-like viruses was developed. Different antigenic preparations made from chicken kidney cells infected with the G-4260 strain of ANV were compared. Crude antigen obtained by fluorocarbon treatment of infected cells was found to be appropriate and to give reproducible results with antisera directed against ANV and three entero-like particles (ELPs): the Belgian entero PV2 and entero 3, and the Irish ELP-1.

Antigenic relationships between fowl enteroviruses.

An antigenical cross-relationship was observed by immunofluorescence and seroneutralisation tests between the G-4260 strain of avian nephritis virus and three other entero-like particles, one isolated by McNulty et al. (Avian Pathology, 13: 429) and the entero PV2 and entero 3 both isolated in our laboratory. No cross reactions were observed between those viruses and the avian encephalomyelitis virus.

Pathogenicity of fowl enteroviruses.

The pathogenicity of avian nephritis virus, entero-like particles described by McNulty et al. (Avian Pathology, 13: 429), the entero PV2 and entero 3 isolated in our laboratory, was studied by oral inoculation of one-day-old specific pathogen-free chickens. All viruses were shown by immunofluorescence and transmission electron microscopy to multiply in the cytoplasm of enterocytes but histological lesions of the intestine were only observed in chickens infected with McNulty's entero-like particles, entero PV2 and entero 3.

Epidemiological study of enteric viruses in broiler chickens: comparison of tissue culture and direct electron microscopy.

The intestinal and caecal contents of chickens from 102 broiler flocks affected by enteric and associated problems were analysed. The second week of life was found to be the most important in the onset of clinical signs of malabsorption shown by the presence of uneven flocks, growth retardation and enteritis problems, but one-week-old flocks frequently presented similar problems. Some cases of feather aberration were observed, mainly in flocks of two weeks of age.

Significance of parvoviruses, entero-like viruses and reoviruses in the aetiology of the chicken malabsorption syndrome.

Specific-pathogen-free White Leghorn chickens and commercial broilers were inoculated orally at 1 day of age with different intestinal preparations containing a chicken parvovirus, an entero-like virus associated with a reovirus from field materials, or the entero-like viruses and reovirus alone. Despite viral multiplication in inoculated birds, no clinical signs or growth retardation were observed in SPF and broiler chickens infected with the reo or parvoviruses. Abnormal faeces and reduction in weight gains were observed after infection with the field materials and the entero-like viruses.

Differential effect of ultraviolet light on the induction of simian virus 40 and a cellular mutator phenotype in transformed mammalian cells.

UV irradiation of simian virus 40 (SV40)-transformed human and hamster cells induced them both to express a mutator phenotype and to produce SV40. The mutator could also be activated indirectly by transfecting unirradiated cells with UV-damaged calf thymus DNA. In contrast, UV-damaged exogenous DNA failed to rescue SV40 from unirradiated transformed cells.