Key Points Autologous activated T cells can drive antigen-independent proliferation of CLL cells through CD40 and IL-21 signaling. An IL-21 gene induction signature, IL-21 mRNA, and protein can be found in CLL lymph node samples.

After exiting the thymus, Foxp3 regulatory T (Treg) cells undergo further differentiation in the periphery, resulting in the generation of mature, fully suppressive effector (e)Treg cells in a process dependent on TCR signaling and the transcription factor IRF4. Here, we show that tumor necrosis factor receptor superfamily (TNFRSF) signaling plays a crucial role in the development and maintenance of eTreg cells. TNFRSF signaling activated the NF-κB transcription factor RelA, which was required to maintain eTreg cells in lymphoid and non-lymphoid tissues, including RORγt Treg cells in the small intestine. In response to TNFRSF signaling, RelA regulated basic cellular processes, including cell survival and proliferation, but was dispensable for IRF4 expression or DNA binding, indicating that both pathways operated independently. Importantly, mutations in the RelA binding partner NF-κB1 compromised eTreg cells in humans, suggesting that the TNFRSF-NF-κB axis was required in a non-redundant manner to maintain eTreg cells in mice and humans.

The ability of the bone marrow (BM) to generate copious amounts of blood cells required on a daily basis depends on a highly orchestrated process of proliferation and differentiation of hematopoietic stem and progenitor cells (HSPCs). This process can be rapidly adapted under stress conditions, such as infections, to meet the specific cellular needs of the immune response and the ensuing physiological changes. This requires a tight regulation in order to prevent either hematopoietic failure or transformation. Although adaptation to bacterial infections or systemic inflammation has been studied and reviewed in depth, specific alterations of hematopoiesis to viral infections have received less attention so far. Viruses constantly pose a significant health risk and demand an adequate, balanced response from our immune system, which also affects the BM. In fact, both the virus itself and the ensuing immune response can have a tremendous impact on the hematopoietic process. On one hand, this can be beneficial: it helps to boost the cellular response of the body to resolve the viral infection. But on the other hand, when the virus and the resulting antiviral response persist, the inflammatory feedback to the hematopoietic system will become chronic, which can be detrimental for a balanced BM output. Chronic viral infections frequently have clinical manifestations at the level of blood cell formation, and we summarize which viruses can lead to BM pathologies, like aplastic anemia, pancytopenia, hemophagocytic lymphohistiocytosis, lymphoproliferative disorders, and malignancies. Regarding the underlying mechanisms, we address specific effects of acute and chronic viral infections on blood cell production. As such, we distinguish four different levels in which this can occur: (1) direct viral infection of HSPCs, (2) viral recognition by HSPCs, (3) indirect effects on HSPCs by inflammatory mediators, and (4) the role of the BM microenvironment on hematopoiesis upon virus infection. In conclusion, this review provides a comprehensive overview on how viral infections can affect the formation of new blood cells, aiming to advance our understanding of the underlying cellular and molecular mechanisms to improve the treatment of BM failure in patients.

BackgroundModified Vaccinia Ankara (MVA) is an attenuated strain of Vaccinia virus (VACV) currently employed in many clinical trials against HIV/AIDS and other diseases. MVA still retains genes involved in host immune response evasion, enabling its optimization by removing some of them. The aim of this study was to evaluate cellular immune responses (CIR) induced by an IL-18 binding protein gene (C12L) deleted vector (MVAΔC12L).Methodology/Principal FindingsBALB/c and C57BL/6 mice were immunized with different doses of MVAΔC12L or MVA wild type (MVAwt), then CIR to VACV epitopes in immunogenic proteins were evaluated in spleen and draining lymph nodes at acute and memory phases (7 and 40 days post-immunization respectively). Compared with parental MVAwt, MVAΔC12L immunization induced a significant increase of two to three-fold in CD8+ and CD4+ T-cell responses to different VACV epitopes, with increased percentage of anti-VACV cytotoxic CD8+ T-cells (CD107a/b+) during the acute phase of the response. Importantly, the immunogenicity enhancement was also observed after MVAΔC12L inoculation with different viral doses and by distinct routes (systemic and mucosal). Potentiation of MVA's CIR was also observed during the memory phase, in correlation with a higher protection against an intranasal challenge with VACV WR. Of note, we could also show a significant increase in the CIR against HIV antigens such as Env, Gag, Pol and Nef from different subtypes expressed from two recombinants of MVAΔC12L during heterologous DNA prime/MVA boost vaccination regimens.Conclusions/SignificanceThis study demonstrates the relevance of IL-18 bp contribution in the immune response evasion during MVA infection. Our findings clearly show that the deletion of the viral IL-18 bp gene is an effective approach to increase MVA vaccine efficacy, as immunogenicity improvements were observed against vector antigens and more importantly to HIV antigens.

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Key Points• Expression of exhaustion markers is decreased on CMV-specific CD8 1 T cells from CLL patients as compared with those from age-matched HCs.• Functionality of CMV-specific CD8 1 T cells in CLL with respect to cytokine production, cytotoxicity, and immune synapse formation is preserved. T cells display lower expression of exhaustion markers and are functionally intact. These data indicate that the changes in the T-cell compartment in CLL may be more heterogeneous than presently assumed. (Blood. 2014;123(5):717-724)

Bone marrow (BM) plays an important role in the long-term maintenance of memory T cells. Yet, BM is found in numerous bones throughout the body, which are not equal in structure, as they differ in their ratio of cortical and trabecular bone. This implies that BM cells within different bones are subjected to different microenvironments, possibly leading to differences in their frequencies and function. To address this, we examined BM from murine tibia, femur, pelvis, sternum, radius, humerus, calvarium, and the vertebrae and analyzed the presence of effector memory (TEM), central memory (TCM), and naïve (TNV) CD8+ T cells. During steady-state conditions, the frequency of the total CD8+ T cell population was comparable between all bones. Interestingly, most CD8+ T cells were located in the vertebrae, as it contained the highest amount of BM cells. Furthermore, the frequencies of TEM, TCM, and TNV cells were similar between all bones, with a majority of TNV cells. Additionally, CD8+ T cells collected from different bones similarly expressed the key survival receptors IL-7Rα and IL-15Rβ. We also examined BM for memory CD8+ T cells with a tissue-resident memory phenotype and observed that approximately half of all TEM cells expressed the retention marker CD69. Remarkably, in the memory phase of acute infection with the lymphocytic choriomeningitis virus (LCMV), we found a massive compositional change in the BM CD8+ T cell population, as the TEM cells became the dominant subset at the cost of TNV cells. Analysis of Ki-67 expression established that these TEM cells were in a quiescent state. Finally, we detected higher frequencies of LCMV-specific CD8+ T cells in BM compared to spleen and found that BM in its entirety contained fivefold more LCMV-specific CD8+ T cells. In conclusion, although infection with LCMV caused a dramatic change in the BM CD8+ T cell population, this did not result in noticeable differences between BM collected from different bones. Our findings suggest that in respect to CD8+ T cells, BM harvested from a single bone is a fair reflection of the rest of the BM present in the murine body.

Modified vaccinia virus Ankara (MVA) is an attenuated poxvirus strain, currently under evaluation as a vaccine vector in various clinical settings. It has been reported that human dendritic cells (DCs) mature after infection with MVA, but reports on the functionality of DCs have so far been controversial. In this work, we studied the phenotype and functionality of MVA-infected DCs. As previously reported, we found that human monocyte-derived DCs upregulated CD86 and HLA-DR in response to MVA infection. Moreover, infected DCs produced a broad array of chemokines and cytokines and were able to activate and induce gamma interferon (IFN-␥) production both in CD4؉ and in CD8 ؉ allogeneic T cells and in specific autologous peripheral blood lymphocytes (PBLs). Analysis of DC maturation following infection with a recombinant green fluorescent protein (GFP)-expressing MVA revealed that upregulation of CD86 expression was mainly observed in GFP neg (bystander) cells. While GFP pos (infected) DCs produced tumor necrosis factor alpha (TNF-␣), they were unable to produce CXCL10 and were less efficient at inducing IFN-␥ production in CEF-specific autologous PBLs. Maturation of bystander DCs could be achieved by incubation with supernatant from infected cultures or with apoptotic infected cells. Type I IFNs were partially responsible for the induction of CXCL10 on bystander DCs. Our findings demonstrate for the first time that, in MVA-infected DC cultures, the leading role with respect to functionality and maturation characteristics is achieved by the bystander DCs.