Human pegivirus persistence in human blood virome after allogeneic haematopoietic stem-cell transplantation.

OBJECTIVES: Because commensal viruses are defined by the immunologic tolerance afforded to them, any immunomodulation, such as is received during haematopoietic stem-cell transplantation, may shift the demarcation between innocuous viral resident and disease-causing pathogen. METHODS: We analysed by deep-sequencing the plasma virome of 40 allogeneic haematopoietic stem-cell transplantation patients 1 month after transplantation. Because human pegivirus (HPgV) was highly prevalent, we performed a 1-year screening of 122 plasma samples by specific real-time reverse transcription PCR assay. We used the log-rank test and the Gray test to assess association with outcomes, and the Mann-Whitney test and multivariable linear regression model to assess association with T-cell reconstitution. RESULTS: Polyomaviruses (PyV) (20/40 patients), anelloviruses (16/40), pegiviruses (14/40) and herpesviruses (14/40) were most frequently identified, including ten cytomegalovirus; three Epstein-Barr virus; two herpes simplex virus type 1; one human herpesvirus 6b and one human herpesvirus 7; 18 Merkel cell-PyV; two BK-PyV; three PyV-6; and one JC-PyV. Papillomavirus and adenovirus were identified in 11 and two patients, respectively. The HPgV specific real-time reverse transcription PCR screening identified 51 of 122 positive samples, high virus loads and persistent infections up to 1 year after transplantation. Comparison between patients with or without HPgV infection at time of transplantation did not reveal a significant difference in infections, engraftment, survival, graft vs. host disease, relapse or immune reconstitution. CONCLUSIONS: The blood virome after allogeneic haematopoietic stem-cell transplantation includes several DNA viruses, notably herpesviruses and PyV. Among RNA viruses, HPgV is highly prevalent and persists for several months, and it thus may deserve special attention in further research on immune reconstitution.

Outcome of hematopoietic stem cell transplantation is similar for patients with a partial in vitro T-cell-depleted graft compared with a non-T-cell-depleted graft when stratified by the refined disease risk index.

Comparisons of hematopoietic stem cell transplantation (HSCT) methods in retrospective studies are often hampered by the heterogeneity of comparison groups. The refined disease risk index (DRI) is a potentially interesting tool to compare HSCT protocols as it is based on the disease type and burden at transplant and stratifies patients into four prognostic groups for overall survival (OS). We included 265 patients with partial T-cell-depleted graft (TDEP) and 163 non-TDEP patients in a retrospective study and compared outcomes following stratification using the refined DRI. The 2-year OS rate for TDEP patients was 81.6, 60.9 and 43.3% for the low-, intermediate- and high-risk groups, respectively (P<0.001). For non-TDEP patients, the 2-year OS rate was 62.9, 48.8, 44.2 and 7.6% for the low-, intermediate-, high- and very-high-risk groups, respectively (P<0.001). There was no significant difference when comparing OS between TDEP and non-TDEP for the low-, intermediate- and high-risk groups, but TDEP patients had less acute GvHD grades II-IV. In conclusion, we confirm that the refined DRI is a valuable tool to compare the outcomes of different HSCT protocols. We demonstrate also that TDEP did not impact on the outcome of HSCT, but it did reduce the incidence of acute GvHD.

Activation of the phosphatidylinositol 3-kinase/Akt pathway protects against interleukin-3 starvation but not DNA damage-induced apoptosis.

Baf-3 cells are dependent on interleukin-3 (IL-3) for their survival and proliferation in culture. To identify anti-apoptotic pathways, we performed a retroviral-insertion mutagenesis on Baf-3 cells and selected mutants that have acquired a long term survival capacity. The phenotype of one mutant, which does not overexpress bcl-x and proliferates in the absence of IL-3, is described. We show that, in this mutant, Akt is constitutively activated leading to FKHRL1 phosphorylation and constitutive glycolytic activity. This pathway is necessary for the mutant to survive following IL-3 starvation but is not sufficient or necessary to protect cells from DNA damage-induced cell death. Indeed, inhibition of the phosphatidylinositol 3-kinase (PI3K)/Akt pathway in Baf-3 cells does not prevent the ability of IL-3 to protect cells against gamma-irradiation-induced DNA damage. This protective effect of IL-3 rather correlates with the expression of the anti-apoptotic Bcl-x protein. Taken together, these data demonstrate that the PI3K/Akt pathway is sufficient to protect cells from growth factor starvation-induced apoptosis but is not required for IL-3 inhibition of DNA damage-induced cell death.