TABLE 2.

Evasion strategies adopted by RNA viruses against the complement system.

S.No.	Complement evasion strategy	Virus family and examples
1.	Recruitment of membrane-associated regulators of complement activation	Rhabdoviridae Vesicular stomatitis virus (CD46, CD55) Paramyxoviridae Parainfluenza virus 5 (CD46, CD55) Newcastle disease virus (CD55, CD46) Flaviviridae Hepatitis C virus (CD59) Retroviridae Human immunodeficiency virus type 1 (CD46,CD55,CD59) Human T-cell leukemia virus type 1 (CD55,CD59)
2.	Incorporation of soluble regulators of complement activation	Flaviviridae Dengue virus (C4BP, Clusterin, Vitronectin) West Nile virus (fH, C4BP) Yellow fever virus (C4BP) Retroviridae Human immunodeficiency virus type 1 (fH)
3.	Virion-associated protease activity (FI-like activity)	Paramyxoviridae Nipah virus Togaviridae Chikungunya virus
4.	Exploitation of complement proteins as entry receptors	Paramyxoviridae Measles virus – Edmonston strain (CD46) Picornaviridae Echoviruses (CD55) Group B coxsackieviruses (CD55)
5.	Transcriptional regulation of complement proteins	Flaviviridae Hepatitis C virus (HCV down regulation of C2, C3 and C9) Paramyxoviridae Parainfluenza virus 5 (up regulation of CD59 and CD55) Retroviridae Human immunodeficiency virus type 1 (down regulation of CD59 and up regulation of C3 and C1q in the brain) Pneumoviridae Human respiratory syncytial virus (Up regulation of CD59 and CD55)
6.	Viral proteins as complement inhibitors	Astroviridae Human astrovirus 1 (Coat protein binds to C1q and arrests C1s) Orthomyxoviridae Influenza virus (A/WSN/33) M1 protein binds to C1q and blocks its interaction with IgG Flaviviridae Bovine viral diarrhea virus (E2 protein) Hepatitis C virus (NS3/4A binds to C4, cleaves γ subunit)