TABLE II.

Viral Factors that Alter Host Immune Functions and Subsequently Result in Increased Virus Survival

Host defense	Virus(es)	Viral factor	Activity	Fitnessa	References
Interleukins	Vaccinia/Cowpox	B15R	Binds to IL-1 & prevents normal function	Population	Spriggs et al. (1992), Alcami & Smith (1992)
	Cowpox	crmA	Prevents IL-1β maturation	Population	Ray et al. (1992)
	EBV	BCRF-1	Blocks IL-10 synthesis	Population	Moore et al. (1993)
	Tanapox	38 kDa	Binds 1L-2 and IL-5	Population	Essani et al. (1994)
Interferons	Adenoviruses	VA RNA	Block IFN-induced autophosphorylation of DAI	Individual	Matthews & Shenk (1991)
		E1A	Block IFN transcriptional signaling	Individual	Ackrill et al (1991), Kalvakolanu et al (1991), Gutch & Reich (1991)
	EBV	EBER RNA	DAI function inhibition	Individual	Bhat & Thimmappaya (1983)
		IL-10 homologue	Downregulates IFNγ synthesis	Individual	Moore et al. (1990)
	HIV-I	Tat	Decreases PKR expression	Individual	Roy et al. (1990)
	Reoviruses	σ3	Blocks activation of IFN-induced PKR	Individual	Imani & Jacobs (1988), Lloyd & Shatkin (1992)
	HBV	Terminal protein	Blocks IFN transcriptional signaling	Population	Foster et al. (1991)
	HSV-I	2-5(A) analogues	Blocks activation of IFN-induced PKR	Individual	Katze (1992), Sen & Ransohoff (1993)
	Myxoma	M-T7	Binds to and neutralizes IFNγ	Population	Upton et al. (1992)
	Influenza	Cellular P58	Inhibits IFN-induced PKR via cell protein activation	Individual	Lee et al. (1990)
	Vaccinia	E3L	Blocks activation of IFN induced PKR	Individual	Chang et al. (1992)
		K3L	PKR decoy substrate	Individual	Davies et al. (1993)
Complement	Vaccinia	C21L	Blocks alternative & classical complement activation	Population	Kotwal et al (1990), Isaacs et al (1992)
components	Herpesvirus saimiri	ORF 4	Blocks alternative & classical complement activation	Population	Albrecht & Fleckenstein (1992)
		ORF 15	Inhibits membrane attack complex	Individual	Albrecht et al. (1992)
	Herpes simplex	Glycoprotein C	Blocks alternative & classical complement activation	Individual	Fries et al. (1986), McNeamey et al. (1987), Harris et al. (1990)
	EBV	Whole virion	Inhibits alternative pathway function	Population	Mold et al. (1988)
TNF	Shope fibroma virus	T2	Binds to TNF and inhibits function	Population	Smith et al. (1991), Upton et at. (1991), Pickup et at. (1993)
	Adenoviruses	E1B	Increase resistance of cells to TNF- induced lysis & apoptosis	Individual	Gooding et al. (1991), White et al. (1992)
		E3	Increase resistance of cells to TNF-induced lysis	Individual	Gooding et al. (1988)
MHC-I	Adenoviruses	E3 (19kDa gp)	Sequesters MHC proteins within ER	Individual	Anderson et al. (1987), Pääbo et al. (1987), Rawle et al. (1989)
	Adenovirus 12	E1A	Inhibits MHC-I transcription	Individual	Schrier et al. (1983), Ackrill & Blair (1988). Ge et al. (1992)
	MCMV	Early protein(s)	Prevents peptide-bound MHC-I transport to surface	Individual	del Val et al. (1992)
Other	HCMV	US28	Binds to and sequesters C—C chemokines	Population	Neote (1993)
	Myxoma	T2	Binds to & sequesters serpins	Population	Lomas et al. (1993), Upton et al. (1990), Macen et al. (1993)
	Poxviruses	EGF-like proteins	Stimulates regional cell growth to enhance progeny virus replication	Population	Brown et al. (1985), Chang et al. (1987)
	MMTV	LTR ORF	Stimulates T- & B-cell proliferation to enhance progeny virus replication	Population	Choi et al. (1991), Korman et al. (1992), Held et al. (1993), Golovkina et al. (1992)
	EBV	LMP-1, LMP-2	B-cell activation & latent-to-lytic infection switch	Population	Miller et al. (1993), Burkhardt et al. (1992)

^a“Fitness” refers to whether the factor contributes to viral population or individual viral fitness.