Protection of chickens from infectious laryngotracheitis with a recombinant fowlpox virus expressing glycoprotein B of infectious laryngotracheitis virus

Infectious laryngotracheitis (ILT) is an economically important disease of chickens caused by a type I gallid herpesvirus, infectious laryngotracheitis virus (ILTV). The vaccines currently available are modified live viruses, which are effective in preventing disease outbreaks. However, they have often been associated with a variety of adverse effects including spread of vaccine virus to non-vaccinates, inadequate attenuation, production of latently infected carriers, and increased virulence as a result of in vivo passage. In this study, a recombinant fowlpox virus expressing glycoprotein B (gB) of ILTV (rFPV-ILTVgB) was constructed. Protection of specific pathogen free (SPF) and commercial chickens from ILT with the rFPV-ILTVgB and commercial ILTV vaccine (Nobilis ILT) were compared after challenge with a lethal dose of virulent ILTV.Both the rFPV-ILTVgB- and the Nobilis ILT-vaccinated SPF chickens were completely protected from death, while 90% of the unvaccinated chickens died after challenge. The immunized commercial chickens were also 100% protected with rFPV-ILTVgB, compared with 85% protected with Nobilis ILT. The protective efficacy was also measured by the antibody response to ILTV gB, isolation of challenge virus and polymerase chain reaction amplification of the ILTV thymidine kinase gene after challenge. The results showed that rFPV-ILTVgB could be a potential safe vaccine to replace current modified live vaccines for preventing ILT.

Isolation and molecular characterization of a porcine teschovirus 1 isolate from China

Porcine teschovirus 1 (PTV-1) (Swine/CH/IMH/03) was isolated from piglets in a farm in Inner Mongolia Province, P.R. China. It was confirmed by electron microscopy, RT-PCR, and sequencing. Comparison of the sequences of the amino acid and nucleotides and phylogenetic analysis of the polyprotein showed that PTV Swine/CH/IMH/03 strain is PTV-1. The isolated virus has closest relationship with Talfan strain, they shared 98.9% and 99.5% homology of amino acids and nucleotides, respectively, in the ORF of polyprotein. To our knowledge, this is the first report about isolation and identification of a PTV in China.

Genetic diversity of avian infectious bronchitis coronavirus strains isolated in China between 1995 and 2004

Twenty-six avian infectious bronchitis (IB) viruses (IBV) were isolated from outbreaks in chickens in China between 1995 and 2004. They were characterized by comparison with twenty-six Chinese reference strains and five other IBV strains. Chinese IBVs, which were mainly nephropathogenic, were placed into seven genotypes. Fourteen Chinese IBV isolates were placed in genotype I, having small evolutionary distances from each other. Genotype II included 6 strains that were isolated in the 1990s in China. Genotype III consisted of eight Chinese isolates that showed close relationship with Korean IBV isolates. Another eight IBV isolates clustered in genotype IV and showed larger evolutionary distances. The Massachusetts serotype was present in China in 1990s and was in a separate genotype. Two isolates, HN99 and CK/CH/LHN/00I, which might be a reisolation of vaccine strains, clustered into genotype VI. Four Chinese IBV isolates formed another genotype and showed larger evolutionary distances from other Chinese IBV genotypes (genotype VII). IBVs in same genotypes showed more than 90% amino acid sequence similarities, whereas most of the viruses in different genotypes showed less than 90%. The results showed that IBVs in China came from genetic changes both in IBV populations that existed before the advent of vaccination and in the viruses that were introduced through live vaccines. IBVs showing various genetic differences are cocirculating in China.

Molecular cloning and physical mapping of bovine herpesvirus 4 strain DN 599 and comparison with two American field-isolates

Ninety four percent of the genome of bovine herpesvirus 4 (BHV-4) strain DN 599 was cloned and a physical map was constructed by Southern blot analysis using a library of cloned fragments cleaved with the 3 restriction enzymes (Eco RI, Bam HI, and Hin dIII). The genome length was estimated to be 156.5 kbp +/- 0.7. The genome comprises a region of unique segment (114 kbp) and two flanking segments containing tandem repeats. The size of each repeat was approximately 2.35 kbp and each repeat contained one Eco RI site and two Bam HI sites. We also examined two recent American field-isolates of BHV-4 and compared the Eco RI maps of the two isolates with that of DN 599. We observed the following: (1) insertions or deletions of restriction sites at the periphery of the unique segment; (2) variation in the lengths of junction fragments; (3) variations in the lengths of hypermolar Eco RI fragments containing the repeats; and (4) the Eco RI map of one of the American field-isolates resembles the BHV-4 "Movar type" of Europe.