CCL2 and infection: Additionally, we found that CCL2 was highly expressed in the in vitro BBB, with concentrations in mock peaking at 4.43 x 104 pg/ml at 72 hpi, but infection with USUV (p = 0.0368) and WNV (p < 0.0001) resulted in a significantly lower concentration at 24 hpi compared to mock (Fig. 5B).