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Marek's disease virus (MDV) is an important oncogenic alphaherpesvirus that induces rapid-onset T-cell lymphomas in its natural hosts. The Meq-clustered miRNAs encoded by MDV have been suggested to play potentially critical roles in the induction of lymphomas. Using the technique of bacterial artificial chromosome mutagenesis, we have presently constructed a series of specific miRNA-deleted mutants and demonstrate that these miRNAs are not essential for replication of MDV and have no effects on the early cytolytic or latent phases of the developing disease. However, compared to the parental GX0101, mortality of birds infected with the mutants GXΔmiR-M2, GXΔmiR-M3, GXΔmiR-M5, GXΔmiR-M9 and GXΔmiR-M12 was reduced from 100 % to 18 %, 30 %, 48 %, 24 % and 14 %, coupled with gross tumour incidence reduction from 28 % to 8 %, 4 %, 12 %, 8 % and 0 %, respectively. Our data confirm that except for mdv1-miR-M4, the other Meq-clustered miRNAs also play critical roles in MDV oncogenesis. Further work will be needed to elucidate the miRNA-mediated regulatory mechanisms that trigger the development of MD lymphomas., (© 2015 The Authors.)

The microRNA (miRNA) mdv1-miR-M4, a functional miR-155 ortholog encoded by oncogenic Marek's disease virus (MDV), has previously been suggested to be involved in MDV pathogenesis. Using the technique of bacterial artificial chromosome mutagenesis, we have presently evaluated the potential role of mdv1-miR-M4 in the oncogenesis of the very virulent (vv) MDV strain GX0101. Unexpectedly, deletions of the Meq-cluster or mdv1-miR-M4 alone from the viral genome strongly decreased rather than abolished its oncogenicity. Compared to GX0101, mortalities of mutants GXΔmiR-M4 and GXΔMeq-miRs were reduced from 100% to 18% and 4%, coupled with the gross tumor incidence reduction from 28% to 22% and 8%, respectively. Our data suggests that the mdv1-miR-M4 is possibly an important regulator in the development of Marek's disease (MD) lymphomas but is not essential for the oncogenicity of vvMDV. In addition, some of the other Meq-clustered miRNAs may also play potentially critical roles in vvMDV induction of lymphomas., (© 2013 Published by Elsevier Inc.)

To study the correlation between ELISA and IFA tests in detection of ALV-A/B antibody in chicken sera, ELSA S/P values and IFA titers for different serum samples were measured and statistically analyzed. The results indicated that there was a strong positive correlation between ELISA S/P values and IFA titers (r = 0.97435, P < 0.001). Because the positive correlation between ELISA and IFA was so strong and antibody positive rates were identical in two tests, it suggested that IFA could be used as a alternative method to replace ELISA kit when only limited numbers of samples to be tested to reduce the cost and increase the sensitivity.

In order to clarify Avian leukosis virus (ALV) characteristics from Chinese native chicken breeds, three ALV JS11C1, JS11C2 and JS11C3 were isolated from Chinese native breed "luhua" by inoculation of DF1 cell culture and detection of p27 antigen. Using PCR amplification of env gene, the amplified gp85 genes were analyzed and compared to all six chicken ALV subgroups reported. The gp85 genes of these three viruses were 1 005bp in length and encoded 335 amino acids, and the gp37 genes were 609bp and encoded 203 amino acids. The homology of gp85 among these three isolated strains was 91.9%-97.0%. Comparing to 18 stains of subgroup A, B, C, D, E published in GenBank, the homology was only in the range of 77.7%-84.6%, significantly lower than the gp85 homology observed within the common chicken subgroups A (88.2%-98.5%), B (91.6%-98.8%), and E (97.9%-99.4%). The gp85 homology compared with subgroup J was only 34.2%-36.5%. These results suggested that three isolated strains from Chinese native breed "luhua" belong to a new subgroup different from all six known subgroups from Chickens, and thus designated as subgroup K.

The predominant field strains of Marek's disease virus in Guangxi were clearly different from the vaccine strain CVI988/Rispens based on sequencing of the envelope glycoprotein I (gI), glycoprotein E (gE) and oncogenic meq genes. These differences may be partly responsible for the most recent outbreaks in Guangxi.

By inoculation of blood samples in DF-1 (C/E) cell culture, an exogenous avian leukosis virus (ALV) strain SDAU09C2 was isolated from a breeder farm of Chinese native breed "Luhua" in Shandong province. Comparisons of the amino acid sequence of env gene gp85 from the isolate with those from other ALV reference strains of different subgroups indicated that SDAU09C2 had the highest gp85 identity to two reference strains of subgroup B of 92.5%. Its gp85 identity to other chicken ALV subgroups A, C, D, E was in the range of 73.2%-87.9%. The identity to subgroup J was only 30.3%-32.4%. This is the first report on isolation and identification of ALV-B and its gp85 from Chinese native breed chickens.

The influences of avian reovirus (ARV) infection at 1 day of age on bursa development, antibody responses after vaccinations to avian influenza virus (AIV), Newcastle disease virus (NDV) and infectious bursal disease virus (IBDV), and pathogenecity of virulent IBDV (v-IBDV) were studied in chickens of SPF-origin. The results indicated that LY strain ARV infection in 1-day-old chickens caused atrophy of the Bursa and decreased lymphocyte numbers in the bursa, but it gave no significant negative effects on growth rates and antibody titers to AIV and NDV after vaccination. LY strain ARV infection decreased antibody titers to IBDV in B87 vaccinated birds but all vaccinated birds infected with ARV were still full protected from death or clinical syndromes after v-IBDV challenge. Although all B87-vaccinated birds were full protected from death after v-IBDV challenges, the antibody titers to AIV or NDV after vaccinations with inactivated vaccines were significantly lower in v-IBDV challenged birds than controls. Supprisingly, ARV infection at ages of 1-7 days could compromise the immune suppression induced by v-IBDV in B87-vaccinated birds as HI antibody titers to AIV and NDV in ARV-infected groups were significantly higher than chicknes with no ARV infection. A discussion was made on the interactions between ARV infection and vaccine IBDV or v-IBDV to explain such sophisticated phenomena in the bird experiments.

An enzyme-linked immunosorbent assay (ELISA) is described for the detection of reticuloendotheliosis viruses (REVs). The assay uses a mixture of monoclonal antibodies (MCAs) prepared against a 62-kilodalton REV envelope glycoprotein (gp62) to capture antigen, rabbit anti-REV serum as detection antibody, and peroxidase-conjugated anti-rabbit IgG as indicator antibody. The MCAs were reactive with REV strain T, chick syncytial virus, and duck infectious anemia virus but unreactive against Marek's disease and avian leukosis viruses. The ELISA was compared with complement fixation test and REV immunofluorescent assay of infected fibroblasts, plasmas, and egg albumen from infected chickens. The lower limit of gp62 detection was about 120 ng of REV protein. Limit dilution of infectious REV was detected after 7-8 days of cultivation of infected fibroblasts.