CSF1 and viral encephalitis: Along with massive inflammatory cell infiltration, elevated proinflammatory cytokine and chemokine expression, called a cytokine storm, result in deleterious encephalitis that is caused by rapid virus replication.18,21 We found significantly higher levels of CCL2 and CSF1, myeloid cell-derived chemokines, in the brain supernatants and plasma from T403A/T403A mice, along with robust production of IFN-β (Fig. 5e and Supplementary information, Fig. S5h).