The severity of the neuroinflammatory reaction was assessed in groups of mice sacrificed at each time-point. At sacrifice the animals were perfused transcardially with approximately 120 mL sterile saline. The brains were then excised, fixed in 4% neutral buffered formalin, and paraffin-wax processed. Coronal sections, taken through the hippocampal brain region, were then prepared and stained with haematoxylin and eosin. The stained sections were assessed in a blinded fashion and the severity of the neuroinflammatory reaction graded using a previously described grading scale . Briefly, a score of 0 describes a normal brain, grade 1 describes sections where a mild meningitis is present while grade 2 shows a moderate meningitis with perivascular cuffing of some vessels. Grade 3 is characterised by more severe meningitis and perivascular cuffing with a few inflammatory cells infiltrating the neuropil, and grade 4 describes a severe meningoencephalitis with inflammatory cells throughout the brain parenchyma.