PD-1/PD-L1 expression in human T-cell leukemia virus type 1 carriers and adult T-cell leukemia/lymphoma patients.

Adult T-cell leukemia/lymphoma (ATLL) develops after infection with human T-cell leukemia virus-1 (HTLV-1) after a long latency period. The negative regulatory programmed death-1/programmed death-1 ligand 1 (PD-1/PD-L1) pathway has been implicated in the induction of cytotoxic T-lymphocyte (CTL) exhaustion during chronic viral infection along with tumor escape from host immunity. To determine whether the PD-1/PD-L1 pathway could be involved in the establishment of persistent HTLV-1 infections and immune evasion of ATLL cells in patients, we examined PD-1/PD-L1 expression on cells from 27 asymptomatic HTLV-1 carriers (ACs) and 27 ATLL patients in comparison with cells from 18 healthy donors. PD-1 expression on HTLV-1-specific CTLs from ACs and ATLL patients was dramatically elevated. In addition, PD-1 expression was significantly higher on CD8+ T cells along with cytomegalovirus (CMV)- and Epstein-Barr virus (EBV)-specific CTLs in ATLL patients compared with ACs and control individuals. Primary ATLL cells in 21.7% of ATLL patients expressed PD-L1, whereas elevated expression was not observed in cells from ACs. Finally, in functional studies, we observed that an anti-PD-L1 antagonistic antibody upregulated HTLV-1-specific CD8+T-cell response. These observations suggest that the PD-1/PD-L1 pathway plays a role in fostering persistent HTLV-1 infections, which may further ATLL development and facilitate immune evasion by ATLL cells.

Efficient correction of Fabry mice and patient cells mediated by lentiviral transduction of hematopoietic stem/progenitor cells.

A deficiency in alpha-galactosidase A (alpha-gal A) activity causes Fabry disease. Virus-based delivery of genes can correct cells and establish a sustained supply of therapeutic proteins. Recombinant lentiviral vectors (LVs) show promise in this context. We first demonstrate LV-mediated marking of peripheral blood (PB) cells by transduction/transplantation of hematopoietic stem/progenitor cells. Stable enGFP expression was observed in PB for 37 weeks. Next, we transplanted Fabry mice with bone marrow mononuclear cells (BMMNCs) transduced a single time with a LV encoding the human alpha-gal A cDNA. Sustained expression of functional alpha-gal A in Fabry mice was observed over 24 weeks. Plasma alpha-gal A activity from treated Fabry mice was two-fold higher than wild-type controls. Increased alpha-gal A activity, often to supra-normal levels, and reduction of globotriaosylceramide, a glycolipid that accumulates in Fabry disease, was observed in all organs assessed. In secondary bone marrow transplantations, Fabry mice showed multilineage marking of PB, splenocytes and BMMNCs, along with therapeutic levels of alpha-gal A activity in plasma and organs over 20 weeks. Lastly, we transduced mobilized PB CD34(+) cells from a Fabry patient and observed corresponding enzymatic increases. Thus a single LV-mediated transduction of primitive hematopoietic cells can result in sustained correction for Fabry disease.