title: Increased bovine Tim-3 and its ligand expressions during bovine leukemia virus infection.
abstract: The immunoinhibitory receptor T cell immunoglobulin domain and mucin domain-3 (Tim-3) and its ligand, galectin-9 (Gal-9), are involved in the immune evasion mechanisms for several pathogens causing chronic infections. However, there is no report concerning the role of Tim-3 in diseases of domestic animals. In this study, cDNA encoding for bovine Tim-3 and Gal-9 were cloned and sequenced, and their expression and role in immune reactivation were analyzed in bovine leukemia virus (BLV)-infected cattle. Predicted amino acid sequences of Tim-3 and Gal-9 shared high homologies with human and mouse homologues. Functional domains, including tyrosine kinase phosphorylation motif in the intracellular domain of Tim-3 were highly conserved among cattle and other species. Quantitative real-time PCR analysis showed that bovine Tim-3 mRNA is mainly expressed in T cells such as CD4+ and CD8+ cells, while Gal-9 mRNA is mainly expressed in monocyte and T cells. Tim-3 mRNA expression in CD4+ and CD8+ cells was upregulated during disease progression of BLV infection. Interestingly, expression levels for Tim-3 and Gal-9 correlated positively with viral load in infected cattle. Furthermore, Tim-3 expression level closely correlated with up-regulation of IL-10 in infected cattle. The expression of IFN-γ and IL-2 mRNA was upregulated when PBMC from BLV-infected cattle were cultured with Cos-7 cells expressing Tim-3 to inhibit the Tim-3/Gal-9 pathway. Moreover, combined blockade of the Tim-3/Gal-9 and PD-1/PD-L1 pathways significantly promoted IFN-γ mRNA expression compared with blockade of the PD-1/PD-L1 pathway alone. These results suggest that Tim-3 is involved in the suppression of T cell function during BLV infection.
authors.affiliation: Department of Disease Control, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, 060-0818, Japan. okazu@vetmed.hokudai.ac.jp.
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Okagawa
authors.forename: Satoru
authors.initials: S
authors.lastname: Konnai
authors.forename: Ryoyo
authors.initials: R
authors.lastname: Ikebuchi
authors.forename: Saori
authors.initials: S
authors.lastname: Suzuki
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Shirai
authors.forename: Yuji
authors.initials: Y
authors.lastname: Sunden
authors.forename: Misao
authors.initials: M
authors.lastname: Onuma
authors.forename: Shiro
authors.initials: S
authors.lastname: Murata
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Ohashi
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000235:genetics* / Q000378:metabolism / Q000821:virology; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics / Q000378:metabolism; D016583:Enzootic Bovine Leukosis / Q000235:genetics* / Q000378:metabolism / Q000821:virology; D037161:Galectins / Q000235:genetics* / Q000378:metabolism; D005786:Gene Expression Regulation; D001909:Leukemia Virus, Bovine / Q000502:physiology*; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D010802:Phylogeny; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D019562:Viral Load / Q000662:veterinary
chemical_list: D018076:DNA, Complementary; D037161:Galectins; D008565:Membrane Proteins; D012333:RNA, Messenger