No abstract

There are nine serotypes of avian paramyxovirus (APMV). Only the genome of APMV type 1 (APMV-1), also called Newcastle disease virus (NDV), has been completely sequenced. In this study, the complete nucleotide sequence of an APMV-6 serotype isolated from ducks is reported. The 16 236 nt genome encodes eight proteins, nucleocapsid protein (NP), phosphoprotein (P), V protein, matrix protein (M), fusion protein (F), small hydrophobic (SH) protein, haemagglutininneuraminidase (HN) protein and large (L) protein, which are flanked by a 55 nt leader sequence and a 54 nt trailer sequence. Sequence comparison reveals that the protein sequences of APMV-6 are most closely related to those of APMV-1 (NDV) and -2, with sequence identities ranging from 22 to 44 %. However, APMV-6 contains a gene that might encode the SH protein, which is absent in APMV-1, but present in the rubulaviruses simian virus type 5 and mumps virus. The presence of an SH gene in APMV-6 might provide a link between the evolution of APMV and rubulaviruses. Phylogenetic analysis demonstrates that APMV-6, -1, -2 (only the F and HN sequences were available for analysis) and -4 (only the HN sequences were available for analysis) all cluster into a single lineage that is distinct from other paramyxoviruses. This result suggests that APMV should constitute a new genus within the subfamily Paramyxovirinae.

This article reports the genetic and pathogenic characteristics of 34 isolates of H6N1 avian influenza viruses isolated in Taiwan between 1972 and 2005. Genetic analyses showed that a unique lineage of H6N1 viruses has been established in domestic chickens in Taiwan since 1997, and this lineage of viruses differs from the H6N1 viruses circulating in Hong Kong and Southeastern China. Pathogenicity tests showed that all Taiwanese H6N1 viruses were of low pathogenicity but might lead to economic loss when associated with other diseases. Hemagglutination inhibition tests showed that antigenic drift has occurred in Taiwanese H6N1 viruses, and sequence comparison has identified a total of five possible antigenic sites on the hemagglutinin molecule of the H6N1 viruses. Some Taiwanese H6N 1 viruses could replicate in mice without preadaptation, indicating that these viruses have the potential to cause cross-species infection into mammals.

We have identified a new phoX gene encoding the monomeric alkaline phosphatase from Pasteurella multocida X-73. This gene was not found in the published genome sequence of Pasteurella multocida pm70. Characterization of the recombinant PhoX of Pasteurella multocida X-73 showed that it is a monomeric enzyme, activated by Ca(2+) and possibly secreted by the Tat pathway. These features distinguish phosphatases of the PhoX family from those of the PhoA family. All proteins of the PhoX family were found to contain a conserved motif that shares significant sequence homology with the calcium-binding site of a phosphotriesterase known as diisopropylfluorophosphatase. Site-directed mutagenesis revealed that D527 of PhoX might be the ligand bound to the catalytic calcium. This is the first report on identification of homologous sequences between PhoX and the phosphotriesterase and on the potential calcium-binding site of PhoX.

Three major outbreaks of Newcastle disease (ND) occurred in Taiwan in the last three decades (in 1969, 1984, and 1995). Newcastle disease viruses (NDVs) isolated in the three outbreaks, together with those isolated in 1998, were sequenced between nucleotides 47 and 435 of the fusion gene. A phylogenetic tree based on sequences obtained showed that the NDV isolated in 1969 was similar to the genotype III viruses. In contrast, all isolates in 1984 and seven of the eight isolates in 1995, together with all isolates in 1998, fell into the genotype VII. These results suggest that the 1969 outbreak of ND in Taiwan was caused by the genotype III virus, whereas the 1984 and 1995 outbreaks were caused by the genotype VII viruses. To date, the genotype VII viruses have caused many outbreaks in east Asia and western Europe. We suspect that these outbreaks have constituted the fourth panzootic of ND, which is distinct from the third panzootic caused by the "pigeon PMV-1 viruses." NDV isolated in Taiwan in 1984 was the earliest isolation of the genotype VII virus.