Development and application of a real-time TaqMan RT-PCR assay for detection of duck hepatitis virus type 1 / 中国比较医学杂志

Objective To develop a real-time RT-PCR assay ( rRT-PCR) for efficient detection of duck hepatitis virus type 1 ( DHV-I) .Method According to the different gene sequences of DHV-I from different provinces download from NCBI and to find the conserved sequences.One pair of the specific primers and one TaqMan probe were designed. Then reaction parameters were optimized to develop a real-time RT-PCR assay ( rRT-PCR) .Results This developed rRT-PCR assay could detect 20 template copies of RNA, and its sensitivity was higher than that of the conventional RT-PCR. This rRT-PCR assay was found to be specific and able to detect DHV-I, and no positive results were observed when nucleic acid from Muscovy duck parvovirus, goose parvovims, Newcastle disease and avian influenza virus, egg drop syndrome virus, reticuloendotheliosis virus, duck Tembusu virus, poultry intestinal arc virus were used as rRT-PCR templates.The results of this developed rRT-PCR assay used for 100 duck clinical samples showed a positive rate of 92%, indicating that DHV exists in duck group of Jiangsu province in China.Conclusion This rRT-PCR assay can be used as a rapid tool for detection of DHV-I.

Cloning and antimicrobial activity of pigeon avian beta-defensin 5 / 生物工程学报

The objective of the study was to clone avian beta-defensin (AvBD) 5 gene from pigeon bone marrow tissues and liver tissues, to express the recombinant AvBD5 protein in E. coli, and to determine its antimicrobial activity. The mRNA of duck AvBD5 was cloned from pigeon bone marrow tissues and liver tissues by RT-PCR. In addition, phylogenetic relationships between amino acid sequence of the pigeon AvBD5, AvBDs from other avian species, and some mammalian beta-defensin-5 were analyzed. The cDNA of pigeon AvBD5 was sub-cloned into pGEX-6p-1 vector to construct recombinant plasmid pGEX-pigeon AvBD5. The recombinant protein was expressed into E. coli and purified. Antimicrobial activity and physical-chemical stability of the recombinant fusion protein were measured in vitro. The complete nucleotide sequence of both cDNAs contained 201 bp nucleotides, encoding a polypeptide of 66 amino acids. Both beta-defensins have six conserved cysteines. Phylogenetic relationships were analyzed. Both pigeon AvBDs shared the highest amino acid homology (87.9% and 78.8%) with duck AvBD5. So it was named as pigeon AvBD5alpha (bone marrow) and AvBD5beta (liver). Both recombinant plasmids were transformed into E. coli BL21 and the bacteria were induced with Isopropyl beta-D-1-Thiogalactopyranoside (IPTG). After purification, antibacterial activity of the purified was investigated. In addition, effect of ionic strength on the antibacterial activity, and hemolytic recombinant protein activity of the purified recombinant protein were investigated. A 32 kDa protein was highly expressed. Both purified recombinant pigeon AvBD5alpha and AvBD5beta exhibited extensive antimicrobial activities against 12 bacteria, including Gram-positive and Gram-negative. In high salt ions concentrations, antibacterial activity of both recombinant proteins was decreased. In addition, the hemolysis activity of recombinant protein was extremely low.

Isolation, identification and bioactivity characterization of goose avian beta-defensin 3 / 生物工程学报

The objective of the study was to clone avian beta-defensin (AvBD) 3 gene from goose tissues, express the recombinant AvBD3 protein in Escherichia coli, and determine its antimicrobial activity. The mRNA of goose AvBD3 was cloned from spleen and bursa of Fabricius of the gooses by RT-PCR. The sequence analysis showed that the genefragment of AvBD3 contained 182 bp, and encoded 60 amino acids. Homology analysis showed that goose AvBD3 shared the highest percentage of amino acid homology (100%) with chicken AvBD3. The cDNA of goose AvBD3 was sub-cloned into BamH I and Sal I sites of pGEX-6p-1 vector to construct recombinant plasmid pGEX-goose AvBD3. The recombinant plasmid was transformed into E. coli BL21 and the bacteria was induced with IPTG It was demonstrated by SDS-PAGE that a 31 kDa protein which was equal to goose AvBD3 protein in molecular weight was highly expressed. The purified recombinant goose AvBD3 exhibited extensive antimicrobial activity against twelve bacteria strains, including Gram-positive and Gram-negative investigated. At high salt ions conditions, antimicrobial activity of recombinant goose AvBD3 protein against both Staphylococcus aureus and Pasteurella multocida decreased significantly. In addition, hemolysis activity of the recombinant protein was extremely low, and the recombinant protein remained antimicrobial activity under different pH values.