HTLV-1 bZIP factor induces inflammation through labile Foxp3 expression.

Human T-cell leukemia virus type 1 (HTLV-1) causes both a neoplastic disease and inflammatory diseases, including HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). The HTLV-1 basic leucine zipper factor (HBZ) gene is encoded in the minus strand of the proviral DNA and is constitutively expressed in infected cells and ATL cells. HBZ increases the number of regulatory T (Treg) cells by inducing the Foxp3 gene transcription. Recent studies have revealed that some CD4⁺Foxp3⁺ T cells are not terminally differentiated but have a plasticity to convert to other T-cell subsets. Induced Treg (iTreg) cells tend to lose Foxp3 expression, and may acquire an effector phenotype accompanied by the production of inflammatory cytokines, such as interferon-γ (IFN-γ). In this study, we analyzed a pathogenic mechanism of chronic inflammation related with HTLV-1 infection via focusing on HBZ and Foxp3. Infiltration of lymphocytes was observed in the skin, lung and intestine of HBZ-Tg mice. As mechanisms, adhesion and migration of HBZ-expressing CD4⁺ T cells were enhanced in these mice. Foxp3⁻CD4⁺ T cells produced higher amounts of IFN-γ compared to those from non-Tg mice. Expression of Helios was reduced in Treg cells from HBZ-Tg mice and HAM/TSP patients, indicating that iTreg cells are predominant. Consistent with this finding, the conserved non-coding sequence 2 region of the Foxp3 gene was hypermethylated in Treg cells of HBZ-Tg mice, which is a characteristic of iTreg cells. Furthermore, Treg cells in the spleen of HBZ-transgenic mice tended to lose Foxp3 expression and produced an excessive amount of IFN-γ, while Foxp3 expression was stable in natural Treg cells of the thymus. HBZ enhances the generation of iTreg cells, which likely convert to Foxp3⁻T cells producing IFN-γ. The HBZ-mediated proinflammatory phenotype of CD4⁺ T cells is implicated in the pathogenesis of HTLV-1-associated inflammation.

Analysis of the variable factors influencing tacrolimus blood concentration during the switch from continuous intravenous infusion to oral administration after allogeneic hematopoietic stem cell transplantation.

The aim of this retrospective study was to identify variable factors affecting tacrolimus blood concentration during the switch from continuous intravenous infusion to twice-daily oral administration in allogeneic hematopoietic stem cell transplant recipients (n = 73). The blood concentration/dose ratio of tacrolimus immediately before the change from continuous infusion (C/Div) was compared with that between 3 and 5 days after the change to oral administration (C/Dpo). Median (C/Dpo)/(C/Div) was 0.21 (range 0.04-0.58). Multiple regression analysis showed that concomitant use of oral itraconazole or voriconazole significantly increased the (C/Dpo)/(C/Div) of tacrolimus (p = 0.002), probably owing to the inhibition of enterohepatic cytochrome P450 3A4. In addition, 5 of 18 (28%) patients who had the lowest quartile (C/Dpo)/(C/Div) values developed acute graft-versus-host-disease (GVHD), which was significantly higher than in others [5 of 55 (9%) patients, p = 0.045]. Although the switch from intravenous to oral administration at a ratio of 1:5 appeared to be appropriate, a lower conversion ratio was suitable in patients taking oral itraconazole or voriconazole. In patients whose blood concentration decreases after the switch, the development of GVHD should be monitored and tacrolimus dosage should be readjusted to maintain an appropriate blood concentration.