[Comparison of immunoprotection between vaccination with meq-deleted Marek's disease virus and vaccine strain CVI988/Rispens].

Objective: To evaluate and compare the immunoprotection between a meq-deleted Marek's disease virus (MDV) and CVI988/Rispens against MDV very virulent strain GX0101.

Methods: In total 120 one-day-old SPF chickens were divided into 4 groups (30 each) and kept in 5 isolators with positive pressure-filtered air. At 1 day of age, 2000 PFU of SC9-1 was inoculated subcutaneously into each bird in group 1; 2000 PFU of commercial vaccine CVI988/ Rispens was inoculated subcutaneously into each bird in group 2.

A recombinant field strain of Marek's disease (MD) virus with reticuloendotheliosis virus long terminal repeat insert lacking the meq gene as a vaccine against MD.

Marek's disease virus (MDV) GX0101, which is a field strain with a naturally occurring insertion of the reticuloendotheliosis virus (REV) long terminal repeat (LTR) fragment, shows distinct biological activities. Deletion of the meq gene in GX0101 contributes to its complete loss of pathogenicity and oncogenicity in SPF chickens, but this virus has a kanamycin resistance gene (kan(r)) residual at the site of meq gene. In the present study, the kan(r) was knocked out and a meq-null virus with a good replicative ability termed SC9-1 was selected.

Transcriptional activity comparison of different sites in recombinant Marek's disease virus for the expression of the H9N2 avian influenza virus hemagglutinin gene.

Over the last two decades, much attention has been paid to MDV-vectored recombinant vaccines. Many factors have influenced their protective efficacy, and insertion site has been among the main influential factors for the expression of foreign genes in recombinant Marek's disease virus (rMDV). To compare the transcriptional activity of different sites of rMDV, an H9N2 avian influenza virus hemagglutinin gene (AIV-H9N2-HA) expression cassette that used the bi-directional promoter of serotype 1 MDV (MDV1) in the 1.

Comparative transcriptional activity of five promoters in BAC-cloned MDV for the expression of the hemagglutinin gene of H9N2 avian influenza virus.

On the basis of recent studies, much attention has been given to recombinant MDV (rMDV)-based vaccines. During the construction of rMDV, the activity of promoters to transcribe foreign genes is one of the major factors that can affect protective efficacy. To investigate the transcription activity and efficacy of five different promoters, the advantage of an existing rMDV BAC infectious clone that had been previously constructed was used to construct rMDVs.

Construction of recombinant Marek's disease virus (MDV) lacking the meq oncogene and co-expressing AIV-H9N2 HA and NA genes under control of exogenous promoters.

To develop a recombinant Marek's disease virus (rMDV1) co-expressing the hemagglutinin gene (HA) and neuramidinase gene (NA) from a low pathogenic avian influenza virus (LPAIV) H9N2 strain and lacking the meq oncogene that shares homology with the Jun/Fos family of transcriptional factors, a wild strain of MDV GX0101 was used as parental virus, the HA and NA genes co-expression cassette under control of the CMV and SV40 early promoters was inserted at two meq sites of GX0101 to form a new meq knock-out mutant MDV (MZC12HA/NA) through homologous recombination. MZC12HA/NA was reconstituted by transfection of recombinant BAC-MDV DNA into the secondary chicken embryo fibroblast (CEF) cells. Highly purified MZC12HA/NA was obtained after four rounds of plaque purification and proliferation.

Construction of recombinant Marek's disease virus (rMDV) co-expressing AIV-H9N2-NA and NDV-F genes under control of MDV's own bi-directional promoter.

To qualitatively analyze and evaluate a bi-directional promoter transcriptional function in both transient and transgenic systems, several different plasmids were constructed and recombinant MDV type 1 strain GX0101 was developed to co-express a Neuraminidase (NA) gene from Avian Influenza Virus H9N2 strain and a Fusion (F) gene from the Newcastle disease virus (NDV). The two foreign genes, NDV-F gene and AIV-NA gene, were inserted in the plasmid driven in each direction by the bi-directional promoter. To test whether the expression of pp38/pp24 heterodimers are the required activators for the expression of the foreign genes, the recombinant plasmid pPpp38-NA/1.