Pathogenicity of fowl enteroviruses.

&lt;p&gt;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&#039;s entero-like particles, entero PV2 and entero 3. Those lesions were present from 3 days post inoculation but were most prominent on the 7th day post inoculation. Variable histological lesions of the pancreas, proventriculus or kidneys were observed 14 days post inoculation with McNulty&#039;s entero-like particles, entero PV2 or entero 3. Avian nephritis virus principally induced kidney lesions. This demonstrates that members of a same species of fowl enteroviruses may have different tropisms and could induce different clinical signs and pathology as nephritis or malabsorption syndrome.&lt;/p&gt;</p

Evolution of pigeon Newcastle disease virus strains.

&lt;p&gt;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. Most of the nucleotide changes observed were silent mutations as only six amino acid changes were observed. Three amino acid substitutions were observed in the F2/F1 cleavage site. The sequence of the F2/F1 cleavage site of all isolates was typical for pathogenic paramyxovirus 1 viruses. Amino acids at the F2/F1 cleavage site changed from (112)GRQKRF(117) to (112)RRQKRF(117), (112)RRKKRF(117) or (112)RRRKRF(117). The motif (112)RRQKRF(117) was present in the majority of the isolates but the intracerebral pathogenicity indexes of PPMV-1 isolates having this motif was highly variable but largely lower (mean, 0.69) than that reported for PPMV-1 viruses isolated in the years 1983 and 1984 (mean, 1.44).&lt;/p&gt;</p

Phylogenetic analysis of fowl adenoviruses.

&lt;p&gt;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. In addition, new insights into the relationships among FAdV strains are presented and discussed on the basis of phylogenetic analysis of the L1 loops sequences. Six clusters of strains that are supported by high bootstrap values were identified. Three of them are clearly independent, forming groups A, B and C, whereas the three others are clustered in a single &#039;supergroup&#039;, denominated D. Interestingly, the Japanese strain TR22 that is presently classified as European type 5 (species B) could not be assigned to any of the aforementioned clusters and might therefore constitute the sole representative of a seventh cluster.&lt;/p&gt;</p

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

&lt;p&gt;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.&lt;/p&gt;</p

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

&lt;p&gt;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. Because antibody responses and protection of in ovo vaccinated chicks were similar to controls vaccinated at hatch with the La Sota strain, immunoselection appears a valuable technique to produce attenuated NDV strains, which are candidate in ovo vaccines.&lt;/p&gt;</p