Leukotrienes play protective roles early during experimental VSV encephalitis

Leukotrienes (LT) are potent lipid mediators of inflammation. 5-Lipoxygenase (5-LO) is the key enzyme in the conversion of arachidonic acid to LT. There are four LT: LTB₄, LTC₄, LTD₄ and LTE₄. LT have been extensively studied in airway inflammation but little is known about their roles in viral infection in the CNS. LTB₄ is a chemoattractant for neutrophils. In this work, we studied the roles of LT in acute vesicular stomatitis virus (VSV) encephalitis. Two methods were used to disrupt 5-LO activity: mice were treated with Zileuton™, an enzyme antagonist, or 5-LO genetic knockout mice were used. We found that inhibition or deletion of 5-LO resulted in: (a) impaired process of neutrophil infiltration into the CNS early during viral infection; (b) fewer neurons expressed nitric oxide synthase-1 (NOS-1); (c) higher viral titers 1 day after viral infection; and (d) increased disruption of blood brain barrier (BBB). Our studies suggest that LT are important innate immune players during VSV pathogenesis and are beneficial to the host in early control of viral replication in the CNS.