Surface IgM on DT40 cells may be a component of the putative receptor complex responsible for the binding of infectious bursal disease virus.

To investigate the host–pathogen interactions between infectious bursal disease virus (IBDV) and target B-lymphocytic cells, a cDNA T7 phage display library from the chicken bursa of Fabricius was constructed and screened for virus binding. Surface immunoglobulin M (sIgM) was isolated as a putative candidate binding site and its interactions with IBDV were further investigated using a chicken bursal lymphoma-derived cell line DT40. The results showed that the λ light chain of sIgM specifically interacted with IBDV in a virulence-independent manner in vitro, and most of the binding of IBDV to DT40 cells was inhibited by sIgM-specific monoclonal antibodies. Further, the infectivity of IBDV in vitro was reduced by sIgM-specific monoclonal antibodies. Our data provided evidence that sIgM may participate as one of the putative membrane binding sites responsible for IBDV infection.