Isolation and identification of three Marek's disease virus strains and sequence comparison of genes involved in pathogenesis / 中国兽医学报

To understand epidemiological characteristics of Marek's disease virus (MDV) prevalent in china currently,3 Marek's disease (MD) strains were isolated and identified from white feather meat chickens vaccined with MDV CVI988 or 814 through necropsy,histopathological observation,virus isolation and IFA detection,named SDAU1501,SDAU1502 and SDAU1503,respectively.vIL8,pp38,MEQ gene of the three strains of MDV were amplified using PCR,and compared with reference strains.The homology between SDAU1501 and SDAU1502 and virulent strains was above 97％,suggesting some features of virulent strains;while meq gene of SDAU1503 lost P amino acid at the 194 th site as that in CVI988,But the distinctive 177 nucleotide insertion mutations was not existed,predicting that it may be a attenuated vaccine strain.New variations of MDV continued and different types of variants emerged,therefore,prevalence and genetic monitoring of MD should be proceeded;meanwhile,more attentions should be given to MDV vaccine development.

Effect of Low Dose of Chicken Infectious Anemia Virus in Attenuated Vaccine on SPF Chicken Body Weight and Vaccine Immune Antibody / 病毒学报

In order to observe the effect of the immune and weight of chickens after use the attenuated vaccine with low dose of chicken infectious anemia virus (CIAV). In this study, the effects of low dose of CIAV on the weight of SPF chickens and NDV antibody production were observed by simulated experiments. The results showed that 10 EID50 and 5 EID50 CIAV per plume attenuated NDV vaccines were used to cause the weight loss of SPF chickens. Compared with the use of the non contaminated vaccine group, it has significant difference. And NDV antibody levels compared with the use of the non contaminated groups also decreased after use the vaccine with two doses of CIAV contaminated. It has significant difference. A certain proportion of CIAV antibody positive was detected at the beginning of the second week after use the NDV vaccine with two doses of CIAV contaminated. The detection of a high proportion of CIAV nucleic acid was detected in the first week after the use of a contaminated vaccine. The results of the study demonstrate the effects of CIAV pollution on the production and immune function of SPF chickens, and it is suggested that increasing the detection of viral nucleic acid can help save time and improve the detection rate in the detection of exogenous virus contamination by SPF chicken test method.

Genomic diversity of the Avian leukosis virus subgroup J gp85 gene in different organs of an infected chicken

The genomic diversity of Avian leukosis virus subgroup J (ALV-J) was investigated in an experimentally infected chicken. ALV-J variants in tissues from four different organs of the same bird were re-isolated in DF-1 cells, and their gp85 gene was amplified and cloned. Ten clones from each organ were sequenced and compared with the original inoculum strain, NX0101. The minimum homology of each organ ranged from 96.7 to 97.6%, and the lowest homology between organs was only 94.9%, which was much lower than the 99.1% homology of inoculum NX0101, indicating high diversity of ALV-J, even within the same bird. The gp85 mutations from the left kidney, which contained tumors, and the right kidney, which was tumor-free, had higher non-synonymous to synonymous mutation ratios than those in the tumor-bearing liver and lungs. Additionally, the mutational sites of gp85 gene in the kidney were similar, and they differed from those in the liver and lung, implying that organ- or tissue-specific selective pressure had a greater influence on the evolution of ALV-J diversity. These results suggest that more ALV-J clones from different organs and tissues should be sequenced and compared to better understand viral evolution and molecular epidemiology in the field.

Construction of Recombinant Marek's Disease Virus Expressing the NDV-F gene and its Replication in Chickens and in Vitro / 病毒学报

We used a meq-deleted attenuated MDV-I strain GX0101Δmeq as a vector to construct a recombinant virus expressing the exogenous gene NDV-F. The ORF of exogenous gene NDV-F was inserted into the eukaryotic expression vector pcDNA3.1(-). Then, the expression cassette of NDV-F which contains the CMV promoter was amplified. Simultaneously, we amplified the selected gene Kan+ expression cassette and inserted them into the PMD18-T vector. Tandem expression cassettes were amplified using primers containing the 50-bp homologous arm of MDV-US2. The PCR product was electroporated into EL250 host bacteria containing GX0101Δmeq. Then, the Kan+ expression cassette was deleted from the recombinant virus genome using 1% arabinose. The plasmid of the positive clone which the Kan+ expression cassette was deleted was extracted and transfected into CEFs to rescue the recombinant virus. The recombinant virus was injected into chickens to observe its growth and replication. The recombinant virus rMDV-F containing the exogenous gene NDV-F was rescued successfully. The recombinant virus could duplicate and express well in CEFs, and grow and replicate well in chickens. Using GX0101Δmeq as a vector, combined with a recombinant system of Red E/T and FLP/FRT, we constructed a recombinant virus that expressed the exogenous gene NDV-F. This study could lay the foundation for further study of recombinant viruses.

Isolation and Identification of a Subgroup A Avian Leukosis Virus from Imported Meat-type Grand-parent Chickens / 中国病毒学·英文版

An exogenous avian leukosis virus (ALV) strain SDAU09C1 was isolated in DF-1 cells from one of 240 imported 1-day-old white meat-type grand parent breeder chicks. Inoculation of SDAU09C1 in ALV-free chickens induced antibody reactions specific to subgroup A or B. But gp85 amino acid sequence comparisons indicated that SDAU09C1 fell into subgroup A; it had homology of 88.8% - 90.3% to 6 reference strains of subgroup A, much higher compared to other subgroups including subgroup B. This is the first report for ALV of subgroup A isolated from imported breeders.