Study on Marek’s disease
Marek’s disease virus (MDV: family, Herpesviridae; subfamily, Alphaherpesvirinae; genus, Mardivirus; species, Gallid alphaherpesvirus 2) is the causative agent of Marek’s disease (MD), which manifests as malignant lymphomas in infected chickens. After MDV enters through the respiratory tract, an early cytolytic infection is induced. Then, T cells are activated, and latent infection is established in these activated T cells. MDV transforms a few latently infected cells, which develop into malignant lymphomas. Although formerly caused serious economic losses to the poultry industry, MD is currently well controlled by vaccination using attenuated strains of MDV. To date, a few vaccines used for the prevention of tumor progression can be available, and therefore, MD vaccines have been studied and discussed as a model of vaccines against tumor progression.
We started researches on MD in 1970s, and have been conducted many research activities over time: search for tumor-associated antigens using MD-derived cell lines, mechanism(s) of tumor development, biological/genetic difference(s) between pathogenic and attenuated (vaccine) strains, mechanism(s) of vaccine-induced protection, immunosuppression in MD pathogenesis, and so on. Furthermore, we surveyed and clarified the prevalence of MDV in wild birds, since the first report of an MD case in white-fronted goose found in Japan, 2001.
MD can be prevented by vaccination as described above. However, there are still some problems, and these problems are called as “vaccine breaks”; MD is developed even in vaccinated chickens due to greater virulence of field strains, and the vaccine breaks are reported worldwide. In Japan, MD cases are sporadically reported. To solve these problems, we investigate the influence of genomic polymorphism(s) among MDV strains on the pathogenicity and the characteristics of MDV strains isolated in Japan, and our final goal is to develop vaccines which can more effectively control MD.