Toll-like receptor-mediated innate immunity against herpesviridae infection: a current perspective on viral infection signaling pathways

Table 1 Properties of toll-like receptors

TLRs	Localization	Ligands
TLR1/2 [33,34,35]	Cell surface	Triacylated lipopeptides
TLR2/6 [36,37,38,39,40,41]	Cell surface	Diacylated lipopeptides (Mycoplasma), Lipoteichoic acid (Streptococcus), Zymosan (Saccharomyces cerevisiae)
TLR2 [38, 42,43,44,45,46,47,48]	Cell surface	Peptidoglycan (Gram-positive bacteria), Lipoarabinomannan (Mycobacteria), Hemagglutinin (measles virus), phosphatidylinositol mannoside 6 (Mycobacteria), Glycosylphosphatidylinositol (Trypanosoma)
TLR3 [49,50,51,52]	Endosome	ssRNA virus (West Nile virus), dsRNA virus (Respiratory syncytial virus, murine cytomegalovirus)
TLR4 [43, 53,54,55,56,57,58,59]	Cell surface	Lipopolysaccharide (Gram-negative bacteria), Mannan-binding lectin (Candida albicans), glycoinositol- phospholipids (Trypanosoma cruzi), Envelope proteins (respiratory syncytial virus, mouse mammary tumor)
TLR5 [60, 61]	Cell surface	Flagellin (flagellated bacteria)
TLR7 [62, 63]	Endosome	ssRNA viruses (vesicular stomatitis virus, influenza virus)
TLR8 [64,65,66]	Endosome	ssRNA from RNA viruses
TLR9 [67,68,69,70,71]	Endosome	dsRNA viruses (herpes simplex virus, murine cytomegalovirus), CpG motifs from bacteria and viruses, Hemozoin (Plasmodium)

ISSN: 1743-422X