Table 2.

The function of the identified motifs of gB of HSV.

Virus	Name	Mutations in gB	Conserved/variable region in gB	Motif in gB	Motif potential function	oHSV effect	Additional modification	References
HSV-1 strain KOS	Y179K, W174R A261D	Y179K, W174R A261D	Conserved region 4	2	Motif 2 may be necessary for virus–cell fusion.	Loss of fusion	None	(29)
HSV-1 (strain not mentioned)	T665i5, V667i5I671i5, L673i5 E187i5	MFKHT inserted after T665, MFKHV inserted after aa667, DLLNI inserted after aa671, NSLNI inserted after aa673, DSLNK inserted after aa187	Conserved region 22	2 and 4	Motif 2 is important for the conformation of the fusion loops.	Fusion deficient	None	(30)
HSV-1 strain KOS	I671A, H681A, F683A	I671A, H681A, F683A	Conserved region 22	4	Motif 4 may be required for virus–cell fusion possibly via interaction of the arm with coil regions of gB.	Decreased fusion	gH:lacked	(31)
HSV-1 strain F	T887A or truncated at residue 886.	T887A or truncated at residue 886.	Variable region 8	None		Reduced virus–cell fusion	gH:lacked	(32)
HSV-1 strain KOS	Y889A LL871AA	Disruption of YTQV motif (aa 889 to 892) and LL motif (aa 871 to 872)	Conserved region 28 and variable region 8	19 and 10	Motif 19 and 10 are involved in cell–cell fusion.	Disruption of YTQV and LL decrease and facilitate virus–cell fusion, respectively	None	(33)
HSV-1 strain KOS	gBΔ28, gBΔ36, A874P	gBΔ28, gBΔ36, A874P	Conserved region 28, variable region 8	10 and 19	Motifs 10 and 19 may participate in virus-induced fusion activity.	Increased cell fusion	None	(34)
HSV-1 strain F	syn3	R857H	Conserved region 26	10	Motif 10 may promote cell–cell fusion and this mutant effectively reduced primary and metastatic breast tumors in immunocompetent mice.	Effective in the treatment	gK: Ala-to-Val at position 40	(35)
HSV-1 strain KOS	Truncated at 863	Lacking the last 41 amino acids of the cytoplasmic domain	Conserved regions 27, 28, variable region 8	10 and 19	Deletion of the carboxy-terminal 41 amino acids had no influence on the function of gB.	No influence	None	(36)
HSV-1 strain F	R-903	Engineered the scFv to HER2 between AA 43 and 44	Variable region 1	15	Motif 15 may be either flexible or non-essential and oHSVs were capable to target Her2+ cancer cells	No influence	None	(22)
HSV-1	R-313, R-315, R-317, R-319	The GCN4 peptide inserted between aa 43 and 44, 81 and 82, 76 and 77, and 95 and 96	Conserved region 6	15 and 13	Motif 15 may be either flexible or non-essential and gB retargeted oHSV could cultivate in non-cancer cells.	No influence	gD: scFv-HER2 replaced aa 6 to 38	(37)
HSV-1 strain KOS	D285N/A549T	D285N/A549T	Conserved region 6 and 15	5 and 14	Motif 5 may regulate the interaction of gB with gH/gL, motif 14 may be essential for the conformational change of gB and the double mutant was effective in an orthotopic mouse model of primary human glioma.	Accelerate cells entry; facilitate cell fusion	gD: R222N/F223I gD: An scFv replaced aa 2–24	(38, 39)
HSV-1 strain KOS	S668N	S668N	Conserved region 21	None		gH/ gB formation	gH: Residues N753K and A778V in the H3 domain	(40)
HSV-1 strain F	T53A, T53/480A	T53A, T53/480A	Variable region 2, conserved region 13,	15 and 17	Motifs 15 and 17 may be required for the binding of gB to PILRα and virus–cell fusion.	Decreased virus–cell fusion and virus entry		(41)
HSV-1 strain S (a syncytial mutant from HSV-1strain F)	T787C	T787C of the cytoplasmic domain of mature gB, results in L to P substitution	Conserved region 24	12	Motif 12 may contribute to gB binding to heparan sulfate.	Decreased gB/heparan sulfate binding	None	(42)
HSV-1 strain KOS	gBpK−	Residues 68 to 76 (KPKKNKKPK) were deleted	Variable region 2	13	Motif 13 may be the heparan sulfate binding element of gB.		gC: gC coding sequence (UL44) deleted	(43)
HSV-1 strain 17	K76L K79L	Replace the aa 75PKPPKP80 with 75PLPPLP80	Variable region 8	13	Motif 13 may be involved in the interaction between gB and HLA-DR heterodimers.	Destroyed gB/HLA-DR heterodimers	None	(44)
HSV-1 strain KOS	C633S or C596S/C633S	Replace the aa 633C or both 633C and 596C with S	Conserved region 19, 24	6	Motif 6 may translocate gB to the cell surface.	Unable to translocate to the cell surface	None	(45)
HSV-2 strain G	N133Q	N133Q	Conserved region 4	7	Motif 7 may be required for gB trafficking from the ER to the Golgi.	Not transported from the ER to the Golgi	None	(46)
HSV-1 strain KOS	gBΔ(730–747), gBΔ(748–773), gBΔ(730–739), gBΔ(735–744), gBΔ(740–749), gBΔ(750–759), gBΔ(765–773)	gBΔ(730–747), gBΔ(748–773), gBΔ(730–739), gBΔ(735–744), gBΔ(740–749), gBΔ(750–759), gBΔ(765–773)	Conserved region 23,24	11	Motif 11 may be required for the interaction between gB and the cell membrane.	Cannot arrive at the cell surface	None	(47)