Herpes and pox viral complement control proteins: ‘the mask of self’

The complement system is an integral participant in the innate mechanisms of immunity and thus has the burden of performing surveillance in the host. The complement system achieves this effectively by covalently attaching C3b, the activated form of complement protein C3, to the surface of foreign pathogens and labeling them as non-self. Although viruses are small and have relatively simple structure, both acute and latent viruses can be efficiently recognized and neutralized by the complement system. However, to combat the complement system of the host and succeed as pathogens, viruses have developed principles to avoid being ‘labeled’ as non-self by complement and thus are considered as self by the complement system.