Gamma-Chain Receptor Cytokines & PD-1 Manipulation to Restore HCV-Specific CD8+ T Cell Response during Chronic Hepatitis C

Hepatitis C virus (HCV)-specific CD8⁺ T cell response is essential in natural HCV infection control, but it becomes exhausted during persistent infection. Nowadays, chronic HCV infection can be resolved by direct acting anti-viral treatment, but there are still some non-responders that could benefit from CD8⁺ T cell response restoration. To become fully reactive, T cell needs the complete release of T cell receptor (TCR) signalling but, during exhaustion this is blocked by the PD-1 effect on CD28 triggering. The T cell pool sensitive to PD-1 modulation is the progenitor subset but not the terminally differentiated effector population. Nevertheless, the blockade of PD-1/PD-L1 checkpoint cannot be always enough to restore this pool. This is due to the HCV ability to impair other co-stimulatory mechanisms and metabolic pathways and to induce a pro-apoptotic state besides the TCR signalling impairment. In this sense, gamma-chain receptor cytokines involved in memory generation and maintenance, such as low-level IL-2, IL-7, IL-15, and IL-21, might carry out a positive effect on metabolic reprogramming, apoptosis blockade and restoration of co-stimulatory signalling. This review sheds light on the role of combinatory immunotherapeutic strategies to restore a reactive anti-HCV T cell response based on the mixture of PD-1 blocking plus IL-2/IL-7/IL-15/IL-21 treatment.

Efficacy of JAK/STAT pathway inhibition in murine xenograft models of early T-cell precursor (ETP) acute lymphoblastic leukemia

Early T-cell precursor (ETP) acute lymphoblastic leukemia (ALL) is a recently described subtype of T-ALL characterized by a unique immunophenotype and genomic profile, as well as a high rate of induction failure. Frequent mutations in cytokine receptor and Janus kinase (JAK)/signal transducer and activator of transcription (STAT) signaling pathways led us to hypothesize that ETP-ALL is dependent on JAK/STAT signaling. Here we demonstrate aberrant activation of the JAK/STAT pathway in ETP-ALL blasts relative to non-ETP T-ALL. Moreover, ETP-ALL showed hyperactivation of STAT5 in response to interleukin-7, an effect that was abrogated by the JAK1/2 inhibitor ruxolitinib. In vivo, ruxolitinib displayed activity in 6 of 6 patient-derived murine xenograft models of ETP-ALL, with profound single-agent efficacy in 5 models. Ruxolitinib treatment decreased peripheral blast counts relative to pretreatment levels and compared with control (P < .01) in 5 of 6 ETP-ALL xenografts, with marked reduction in mean splenic blast counts (P < .01) in 6 of 6 samples. Surprisingly, both JAK/STAT pathway activation and ruxolitinib efficacy were independent of the presence of JAK/STAT pathway mutations, raising the possibility that the therapeutic potential of ruxolitinib in ETP-ALL extends beyond those cases with JAK mutations. These findings establish the preclinical in vivo efficacy of ruxolitinib in ETP-ALL, a biologically distinct subtype for which novel therapies are needed.

Successful vaccination induces multifunctional memory T-cell precursors associated with early control of hepatitis C virus

BACKGROUND & AIMS

T cells are an important component for development of a vaccine against hepatitis C virus (HCV), but little is known about the features of successful vaccine-induced T cells.

METHODS

We compared the phenotype, function, and kinetics of vaccine-induced and infection-induced T cells in chimpanzees with HCV infection using multicolor flow cytometry and real-time polymerase chain reaction.

RESULTS

In chimpanzees successfully vaccinated with recombinant adenovirus and DNA against HCV NS3-5, HCV-specific T cells appeared earlier, maintained better functionality, and persisted at higher frequencies for a longer time after HCV challenge, than those of mock-vaccinated chimpanzees. Vaccine-induced T cells displayed higher levels of CD127, a marker of memory precursors, and lower levels of programmed death-1 (PD-1) than infection-induced T cells. Vaccine-induced, but not infection-induced, T cells were multifunctional; their ability to secrete interferon gamma and tumor necrosis factor α correlated with early expression of CD127 but not PD-1. Based on a comparison of vaccine-induced and infection-induced T cells from the same chimpanzee, the CD127(+) memory precursor phenotype was induced by the vaccine itself rather than by low viremia. In contrast, induction of PD-1 correlated with viremia, and levels of intrahepatic PD-1, PD-L1, and 2,5-OAS-1 messenger RNAs correlated with peak titers of HCV.

CONCLUSIONS

Compared with infection, vaccination-induced HCV-specific CD127(+) T cells with high functionality that persisted at higher levels for a longer time. Control of viremia prevented up-regulation of PD-1 on T cells and induction of PD-1, PD-L1, and 2,5-OAS-1 in the liver. Early development of a memory T-cell phenotype and, via control of viremia, attenuation of the inhibitory PD1-PD-L1 pathway might be necessary components of successful vaccine-induced protection against HCV.

Differential IL-7 responses in developing human thymocytes

Interleukin (IL)-7 is a factor essential for mouse and human thymopoiesis. Mouse thymocytes have altered sensitivities to IL-7 at different developmental stages. CD4/CD8 double positive (DP) mouse thymocytes are shielded from the influence of IL-7 because of loss of CD127 (IL-7Ralpha). In this study, we assessed IL-7 receptor expression and IL-7 signaling in human thymocytes. We found human DP cells to be severely limited in their ability to phosphorylate STAT-5 in response to IL-7. The relative expression levels of the IL-7-inducible proteins Bcl-2 and Mcl-1 were also lower in human DP cells, consistent with a stage-specific decrease in IL-7 responsiveness. IL-7 responses were restored in a subset of cells that matured past the DP stage. Unlike the regulation of IL-7 signaling in mouse thymocytes, loss of IL-7 signaling in human DP cells was not due to absence of CD127, but instead correlated with downregulation of CD132 (common gamma chain).

[Effect of rapamycin in inducing naïve murine effector T cell convert to regulatory T cell]

OBJECTIVE

To study the effect of rapamycin in inducing naïve murine effector T cell (Teff) convert to regulatory T cell (Treg) in vitro.

METHODS

The forkhead box protein 3 (FoxP3) negative Teff were isolated and purified from the spleen and lymph node of C57 BL/6 murines aged 6-8 weeks, then Teff were cultured in three groups with mature dendritic cells (mDC), B cells, and plate coated Anti-CD3. In addition, the control wells and the test wells were prepared in each group, rapamycin were not added in the control wells but added in the test wells with concentrations of 1, 10, 50, and 100 nmol/L. Percentages of FoxP3 positive Treg were examined by flow cytometry after 4 days in Anti-CD3 group and after 6 days in the other two groups.

RESULTS

As shown by the flow cytometry, the percentages of FoxP3 positive Treg were as follows in three group: in the mDC group, it was 0.01% in the control well and 0.39%, 0.47%, 0.34%, and 0.26% in test wells; in B cell group, it was 0.01% in the control wells and 5.56%, 5.89%, 7.15%, and 4.72% in the test wells; in Anti-CD3 group, it was 0.93% in the control wells and 1.35%, 1.07%, 1.02%, and 1.19% in test wells. No significant difference was found between the test wells and control wells in the mDC group and Anti-CD3 group; however, the percentages of FoxP3 positive Treg was significantly different between the test wells and control wells in the B cell group (P < 0.01).

CONCLUSION

When B cell is acted as the antigen-presenting cell, rapamycin can effectively induce Teff convert to Treg in vitro.