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Highly pathogenic avian influenza A viruses of subtypes H5 and H7 are the causative agents of fowl plague in poultry. Influenza A viruses of subtype H5N1 also caused severe respiratory disease in humans in Hong Kong in 1997 and 2003, including at least seven fatal cases, posing a serious human pandemic threat. Between the end of February and the end of May(More)
A full-length cDNA clone of Newcastle disease virus (NDV) vaccine strain LaSota was assembled from subgenomic overlapping cDNA fragments and cloned in a transcription plasmid between the T7 RNA polymerase promoter and the autocatalytic hepatitis delta virus ribozyme. Transfection of this plasmid into cells that were infected with a recombinant fowlpoxvirus(More)
An epidemic of high-pathogenicity avian influenza (HPAI) A virus subtype H7N7 occurred in The Netherlands in 2003 that affected 255 flocks and led to the culling of 30 million birds. To evaluate the effectiveness of the control measures, we quantified between-flock transmission characteristics of the virus in 2 affected areas, using the reproduction ratio(More)
Despite considerable research efforts, little is yet known about key epidemiological parameters of H5N1 highly pathogenic influenza viruses in their avian hosts. Here we show how these parameters can be estimated using a limited number of birds in experimental transmission studies. Our quantitative estimates, based on Bayesian methods of inference, reveal(More)
Circular double-stranded replication intermediates were identified in low-molecular-weight DNA of cells of the avian leukemia virus-induced lymphoblastoid cell line 1104-X-5 infected with chicken anemia virus (CAV). To characterize the genome of CAV, we cloned linearized CAV DNA into the vector pIC20H. Transfection of the circularized cloned insert into(More)
Four UK strains of three different serotypes were found to differ by only 2-3% of their S1 amino acids. The S1 sequences were also very similar to those of three Dutch isolates (D207, D274 and D3896), the greatest difference between two of the seven isolates being 4.4%. The few amino acid differences between the seven isolates were located largely between(More)
Monoclonal antibodies (MAbs) directed against structural proteins of infectious bronchitis virus (IBV) were produced to analyse the antigenic structure of this virus. Competitive binding of enzyme-labelled and unlabelled MAbs to IBV peplomer protein was analysed in an antibody binding assay to test the relatedness of the epitopes defined by the MAbs. Based(More)
Chicken anaemia virus (CAV) is a small virus of a unique type with a particle diameter of 23 to 25 nm and a genome consisting of a circular single-stranded (minus-strand) DNA. This DNA multiplies in infected cells via a circular double-stranded replicative intermediate, which was recently cloned. DNA analysis of CAV strains isolated in different continents(More)
Fast diagnosis of Newcastle disease is a prerequisite for confining outbreaks. Diagnosis implies the differentation of virulent and non-virulent Newcastle disease viruses (NDV). However, conventional methods, i.e. isolation of the virus and determination of the intracerebal pathogenicity index, take at least 5 days. Therefore, we investigated whether(More)
Neutralizing monoclonal antibodies directed against five antigenic sites on the spike (S) S1 glycopolypeptide of avian infectious bronchitis virus (IBV) were used to select neutralization-resistant variants of the virus. By comparing the nucleotide sequence of such variants with the sequence of the IBV parent strain, we located five antigenic sites on the(More)