Serum cleaved Tau protein and neurobehavioral battery of tests as markers of brain injury in experimental bacterial meningitis.

Brain injury due to bacterial meningitis affects multiple areas of the brain with a heterogeneous distribution generating a challenge to assess severity. Tau proteins are microtubular binding proteins localized in the axonal compartment of neurons. Brain injury releases cleaved Tau proteins (C-tau) into the extracellular space where they are transported to the cerebral spinal fluid. We hypothesized that C-tau crosses the blood-brain barrier during inflammation and that it can be detected in serum. The correlation between serum C-tau levels and the extent of the meningitic insult was examined. Furthermore, we studied whether the use of a subset of neurobehavioral tasks can assess the extent of brain injury after meningitis. The tests were chosen primarily for their ability to detect deficits in the acoustic system, low brain, reflexive responding, as well as for impaired motor coordination and the higher brain functions of learning and memory. A rat model of group B streptococcal meningitis with variable severity was utilized. At five days after bacterial inoculation followed by antibiotic therapy neurobehavioral tests were performed and serum C-tau and histologic samples of the brain were obtained. Our study shows that during meningitis C-tau appears in serum and reflects the extent of neurologic damage. Neurobehavioral performance was altered after bacterial meningitis and could be correlated with histologic and biochemical markers of neurologic sequelae. We conclude that serum C-tau and a composite of neurobehavioral tests could become useful markers for assessing the severity of neurological damage in experimental bacterial meningitis.