C3 and herpes simplex encephalitis: In viral infections, we have reported that C3a, C3b, C5, and C5a increased intrathecally in the acute stage in patients with herpes simplex encephalitis (HSE) and that C3a and C5a remained increased in later stages, suggesting that complement activation may also be a part of a chronic neuroinflammation (Eriksson et al. 2016).