Marek’s disease virus (MDV) is highly contagious and causes a deadly cancer of the lymph nodes (lymphoma) and immunosuppression in poultry. The virus’s ability to supress immune responses of birds is one of the reasons MDV is such a major threat to the poultry industry, as it prevents recovery and makes birds susceptible to secondary infections.

In their most recent study published in PLOS Pathogens, researchers from the Avian Immunology group demonstrated an association between the number of the new immune cells, known as suppressor lymphocytes, and susceptibility to lymphoma formation. Their findings also show that infection with Marek’s disease virus increases the number of suppressor lymphocytes, which are able to suppress the chicken immune response.

Dr Shahriar Behboudi, Head of the Avian Immunology group at Pirbright, said: "Some viruses exploit host immune cells for their own purpose to evade normal host defences. We found that MDV can modulate immune responses by activating suppressor lymphocytes, contributing to immunosuppression and lymphoma formation."

The scientists also noted that lymphoma cells have similar characteristics to suppressor lymphocytes, meaning they too can suppress immune responses. Combined, these findings identify new pathways that are involved in the development of the disease, which can help identify chicken lines that are more resistant to MDV.

Losses relating to MDV are estimated to be up to $2 billion worldwide. Nearly 22 billion vaccine doses a year are used in an attempt to control the disease, but the virus continues to evolve and form increasingly virulent strains. Understanding how MDV causes immunosuppression is therefore a vital area of research that Pirbright scientists are working on.

This study was funded by the Biotechnology and Biological Sciences Research Council, grant number BBS/N002598/1.

Further Reading

Find out more information on Marek’s disease by clicking here.