Antibody Production Remains Intact Despite Loss of Bone Marrow B cells in Murine Norovirus InfectedStat1–/–Mice

Murine norovirus (MNV), which can be used as a model system to study human noroviruses, can infect macrophages/ monocytes, neutrophils, dendritic, intestinal epithelial, T and B cells, and is highly prevalent in laboratory mice. We previously showed that MNV infection significantly reduces bone marrow B cell populations in a Stat1 -dependent manner. We show here that while MNV-infected Stat1 -/- mice have significant losses of bone marrow B cells, splenic B cells capable of mounting an antibody response to novel antigens retain the ability to expand. We also investigated whether increased granulopoiesis after MNV infection was causing B cell loss. We found that administration of anti-G-CSF antibody inhibits the pronounced bone marrow granulopoiesis induced by MNV infection of Stat1 -/- mice, but this inhibition did not rescue bone marrow B cell losses. Therefore, MNV-infected Stat1 -/- mice can still mount a robust humoral immune response despite decreased bone marrow B cells. This suggests that further investigation will be needed to identify other indirect factors or mechanisms that are responsible for the bone marrow B cell losses seen after MNV infection. In addition, this work contributes to our understanding of the potential physiologic effects of Stat1- related disruptions in research mouse colonies that may be endemically infected with MNV.