（論文要様 式 ３）

旨Reduced Tim-3 expression on human T-lymphotropic virus type I(HTLV-I) Tax-specific cytotoxic T lymphocytes in HTLV-I infection
HTLV-I 感染症における HTLV-I Tax 特異的細胞傷害性
T リンパ球上の Tim-3 発現の低下
ナシュワ ハゼイン アブデルバリー リスク【Introduction and Objectives】
Human T-lymphotropic virus type I (HTLV-I) is a retrovirus that preferentially infects CD4 + lymphocytes invivo. Although HTLV-I infection is life long, less than 1% of infected individuals develop HTLV-I-associatedmyelopathy/tropical spastic paraparesis (HAM/TSP), a neurologic disease. HTLV-I proviral load and frequency
of HTLV-I-speciﬁc CD8+ cytotoxic T lymphocytes (CTLs) are increased in the peripheral blood of patients withHAM/TSP as compared to asymptomatic carriers. Although increasing evidence supports the hypothesis thatsuch a strong CTL response could certainly contribute to the control of viral replication and diseasedevelopment, the exact pathogenic role of the CTL responses remains unclear. T-cell immunoglobulin andmucin domain-containing molecule-3 (Tim-3) and programmed cell death-1 (PD-1) are T-cell exhaustion
molecules and it remains unclear whether CTL function is impaired in HAM/TSP patients. In this study, weinvestigated Tim-3 and PD-1 expression in HTLV-I infection. In particular, we studied HTLV-I-specific CTLs
and their degranulation activity in HAM/TSP patients and asymptomatic carriers as well as the role of Tim-3and PD-1 in regulating their function.
【Materials and Methods】
Using the PBMCs of 32 HAM/TSP patients, 31 asymptomatic carriers (ACs) and 11 healthy controls (HCs),by the flow cytometer, we detected:•Tim-3 or PD-1expression on CD3+CD4+, CD3+CD8+ and CD8+Tax tetramer+ cells.

•IFN-γ production in Tim-3+ and Tim-3– or in PD-1+ and PD-1– cells in both CD8+ and Tax tetramer+cells.

•CTL cytolytic activity measured by CD107a degranulation assay in Tim-3+ and Tim-3– or in PD-1+and PD-1– cells in Tax tetramer+ cells.

•Tim-3 or PD-1 expression on HTLV-I-infected CD4+ or CD8+ cells.

The quantitative PCR of HTLV-I proviral load for infected cases was done.
【Results】•Low expression of Tim-3 on CD4+ and CD8+ T cells in HTLV-I infected individuals in comparison tohealthy controls.
•Low expression of Tim-3 on HTLV-I Tax-specific CTLs compared with CMV-specific CTLs in HTLV-Iinfection.

•There is no significant difference in frequency of Tim-3+ cells in HTLV-I Tax-specific CTLs in both
HAM/TSP patients and asymptomatic carriers, although the mean fluorescence intensity (MFI) is higher inasymptomatic carriers than in HAM/TSP patients.

•There is no significant difference in PD-1 expression (neither frequency nor MFI) between HAM/TSPpatients, asymptomatic carriers and healthy controls in either CD4+ or CD8+cells.

•Significant higher expression of PD-1 on HTLV-I Tax-specific CTLs compared with CMV-specific CTLs
in HAM/TSP patients, and on Tax-specific CTLs in asymptomatic carriers than in HAM/TSP patients.

•

Reduced IFN- production and cytolytic activity (CD107a expression) in Tim-3+, but not PD-1+, HTLV-I
Tax-specific CTLs.

•No difference in the expression of Tim-3 or cytolytic activity between Tax-specific CTLs of HAM/TSPpatients or asymptomatic carriers.

•The frequencies of Tim-3+ or PD-1+ cells in Tax-specific CTLs did not correlate with HTLV-I proviralloads, duration of illness, disease activity, age of the patients or serum HTLV-1 antibody titer in HAM/TSPpatients.

•Low expression of Tim-3 on CD4+ and CD8+ HTLV-I-infected cells. Low expression of PD-1 on CD8+HTLV-I infected cells.

【Discussion and Conclusions】
The decreased expression of Tim-3 in HTLV-I infection is a marked contrast to other chronic viral infections
such as HIV and HCV infection, where Tim-3 expression is increased in T cells, including the virus-specificCTLs. As our and others’ results proved that Tim-3 identifies a subset of CTLs with impaired production ofcytokines and cytolytic activity. It strongly suggests that the Th1/Tc1 immune response is not negatively
regulated by Tim-3 in HTLV-I infection. Rather, immune cells such as HTLV-I-specific CTLs may be resistantto cell death through the Tim-3/galectin-9 pathway. IFN- production was higher in CD8+ cells and HTLV-I
Tax-specific CTLs that expressed PD-1, which also show higher CD107a expression as compared to their PD-1counterparts in HAM/TSP patients. These results indicate that PD-1+ HTLV-I Tax-specific CTLs are capable ofproducing proinflammatory cytokines and have high cytolytic activity during HTLV-I infection. These results
suggest that PD-1 and Tim-3 may have a distinct function in regulating immune responses in HTLV-1 infection.
Tim-3 and CD107a expression in HTLV-I Tax-specific CTLs are not significantly different between HAM/TSPpatients and asymptomatic carriers. Therefore, we concluded that Tim-3, but not PD-1, expression is reduced inHTLV-I infection and that the expression levels on HTLV-I Tax-specific CTLs are not different between
HAM/TSP patients and HTLV-I carries. These results suggest that HTLV-I Tax-specific CTLs preserve theircytolytic activity, thereby controlling viral replication.

（The Journal of Infectious Diseases ,in press）