Marek's disease virus (MDV) causes an acute lymphoproliferative disease in chickens, resulting in T cell lymphomas in visceral organs and peripheral nerves. Earlier studies have determined that the repeat regions of oncogenic serotype 1 MDV encode a basic leucine zipper protein, Meq, which structurally resembles the Jun͞Fos family of transcriptional activators. Meq is consistently expressed in MDV-induced tumor cells and has been suggested as the MDVassociated oncogene. To study the function of Meq, we have generated an rMd5⌬Meq virus by deleting both copies of the meq gene from the genome of a very virulent strain of MDV. Growth curves in cultured fibroblasts indicated that Meq is dispensable for in vitro virus replication. In vivo replication in lymphoid organs and feather follicular epithelium was also not impaired, suggesting that Meq is dispensable for lytic infection in chickens. Reactivation of the rMd5⌬Meq virus from peripheral blood lymphocytes was reduced, suggesting that Meq is involved but not essential for latency. Pathogenesis experiments showed that the rMd5⌬Meq virus was fully attenuated in chickens because none of the infected chickens developed Marek's disease-associated lymphomas, suggesting that Meq is involved in lymphocyte transformation. A revertant virus that restored the expression of the meq gene, showed properties similar to those of the parental virus, confirming that Meq is involved in transformation but not in lytic replication in chickens.

The fulfillment of Koch’s postulates shows that the virus causes proventricular dilatation disease in parrots.

Marek's disease virus (MDV) is an acute transforming alphaherpesvirus that causes T-cell lymphomas in chickens.We previously reported the identification of a putative oncogene, meq, that is encoded only by the oncogenic serotype of MDV. The gene product, Meq, is a latent protein that is consistently expressed in MDV-transformed lymphoblastoid cells and tumor cells. Meq has a bZIP (basic leucine zipper) structure resembling the family of Jun/Fos. The mechanism whereby Meq transforms T cells remains poorly understood. In this study, we explored the properties of Meq as a transcriptional factor. We analyzed Meq's dimerization partners and its target genes in MSB-1, an MDV-transformed T-cell line. By using in vitro assays, we first demonstrated Meq's potential to dimerize with a variety of bZIP proteins. We then identified c-Jun as the primary dimerization partner of Meq. Both are found to be colocalized in the nucleus and corecruited to promoters with AP-1 sequences. By using chromatin immunoprecipitation (ChIP), we scanned the entire MDV genome for Meq binding sites and found three regions that were enriched with Meq binding: the MDV lytic replication origin, the promoter for Meq, and the promoter for ICP4. Transactivation assays using the above promoters showed that Meq/Meq homodimers exhibited repression activity, whereas Meq/Jun heterodimers showed activation. Finally, we were able to show by ChIP that Meq is recruited to the interleukin-2 promoter in a region encompassing an AP-1 site. Thus, in addition to providing general knowledge about the transcriptional properties of Meq, our studies revealed for the first time the ability of Meq to interact with the latent MDV and host genomes. Our data suggest, therefore, a role for Meq in viral genome regulation during latency, in addition to its putative causal role in T-cell transformation.Marek's disease (MD) is a communicable viral lymphoproliferative disease of chickens (13). The signs associated with MD are paralysis, depression, tremors, blindness, widespread T-cell lymphomas, and death. The costs of controlling MD and the associated loss make MD one of the most costly infectious diseases affecting the poultry industry. MD is caused by MD virus (MDV) (13). MDVs are composed of three antigenically related viruses, serotypes 1, 2, and 3, of which only serotype 1 MDVs are oncogenic. MDV is the only acute transforming alphaherpesvirus that causes tumors in its host. MDV was classified as an alphaherpesvirus on the basis of DNA sequence homology and genome organization (29, 55; P. Brunovskis, Z.

Background: MicroRNAs (miRNAs) play critical roles in a wide spectrum of biological processes and have been shown to be important effectors in the intricate host-pathogen interaction networks. Avian influenza virus (AIV) not only causes significant economic losses in poultry production, but also is of great concern to human health. The objective of this study was to identify miRNAs associated with AIV infections in chickens.