Mohammad A. Sabsabi Ahmed Kheimar Dominik von La Roche Sonja Härtle Dusan Kunec Yulin Cong Lisa Kossak Theresa von Heyl Benjamin Schusser Benedikt B. Kaufer 
Vaccine, 2025, doi: 10.1016/j.vaccine.2025.128048 

• Before this study, research on vaccines against Marek’s disease virus (MDV) focused largely on T cell mediated immune responses, while the role of B cells in vaccine mediated protection remained poorly understood and largely underappreciated. The prevailing assumption was that cellular immunity, particularly T cells, was the main driver of vaccine efficacy against MDV.
• Our study demonstrates that B cells play a significant functional role in the protective immunity induced by HVT vaccination. This provides a novel insight showing that B cells contribute actively to the immune defense post HVT vaccination.
• This study provides the first direct evidence that B cells are essential for full HVT mediated protection. Although tumour prevention remained intact in the absence of  B cells, the marked increase in clinical disease and early viral shedding shows that humoral immunity is crucial for controlling early replication and transmission. Overall, our study provides the first clear evidence that B cells and/or antibodies play an important role in the vaccine protection against MDV provided by the HVT vaccine, which is used to protect billions of chickens worldwide.