Tunicamycin enhances neuroinvasion and pathogenicity in mice with Venezuelan equine encephalitis virus

Venezuelan equine encephalitis (VEE) virus infects horses and humans and is a potential biothreat pathogen. Agents that alter the blood-brain barrier (BBB) may enhance viral encephalitides. The current studies explored whether tunicamycin (TM) and other agents affect the pathogenesis of VEE.; A study with the molecularly-cloned virulent V3000 virus showed that TM-treated mice had significantly (p < .05) decreased mean survival time (MST) of 7.3 days versus 9.9 days in controls. Using plaque assay, V3000 reached nearly 107 pfu/gram in the brains of TM-treated mice at 48 hours post inoculation (PI) versus 103 pfu/gram in controls. The attenuated V3034 strain invaded the brains of TM-treated mice by 48 hours PI versus 72 hours for controls and TM-treated mice had 100-fold or more virus at all times. TM-treated and control mice had similar viremia profiles with both viruses and similar V3000 brain replication curves. Immunohistochemistry showed that V3000 invaded the brains of TM-treated mice by 24 hours, versus 48 hours for the controls. V3000 appeared to enter the brain via the olfactory tract, not via the BBB, in both groups. TM-treated mice with V3000 exhibited earlier clinical signs and greater weight loss than controls. The brains of TM-treated mice had earlier and more severe inflammation, neuronal damage, and extravascular fibrinogen and upregulation of several cytokines. Electron microscopy of the brains of uninfected, TM-treated mice revealed perivascular edema and swollen astrocyte endfeet.; Additional studies failed to show that pyridostigmine, LPS or TNF-α significantly altered VEE. Pyridostigmine and LPS-treated mice with V3034 showed similar neuroinvasion patterns as controls and those with V3000 showed similar MSTs as controls. Serum TNF-α was increased in V3000-infected mice (peak - 52.9 pg/ml at 24 hours). However, mice given antibodies to TNF-α had identical neuroinvasion patterns as controls.; These findings indicate that TM enhances neuroinvasion and pathogenicity in mice infected with VEE virus but fail to indicate that pyridostigmine, LPS and TNF-α affect VEE similarly, suggesting TM is unique in its effect on VEE virus. Tunicamycin could be a useful tool in further studies of VEE virus neuroinvasion.