CFH and viral infectious disease: An increase of IAV binding in presence of factor H and VCP was seen at the concentration of 10 μg/ml for both H1N1 and H3N2 IAV subtypes, and the binding occurred in a dose and calcium dependent manner (Figure 4), suggesting that factor H and VCP enhance binding of IAV to target cells, which in turn interferes with viral infection in a complement-independent manner.