IL-7 unveils pathogen-specific T cells by enhancing antigen-recall responses

BACKGROUND: IL-7 promotes the generation, expansion and survival of memory T cells. Previous mouse and human studies showed that IL-7 can support immune cell reconstitution in lymphopenic conditions, expand tumor-reactive T cells for adoptive immunotherapy and enhance effector cytokine expression by autoreactive T cells. Whether pathogen-reactive T cells also benefit from IL-7 exposure remains unknown. METHODS: Here we investigated this issue in cultures of peripheral blood mononuclear cells (PBMCs) derived from patients infected with various endemic pathogens. After short-term exposure to IL-7, we measured PBMC responses to antigens (Ag) derived from pathogens, such as Mycobacterium tuberculosis (MTB), Candida albicans (Ca) and Cytomegalovirus (CMV), and to the superantigen Staphylococcus aureus enterotoxin B (SEB). RESULTS: We found that IL-7 favoured the expansion and, in some instances, the uncovering of pathogen-reactive CD4 T cells, by promoting pathogen-specific IFNɣ, IL-2 and TNF recall responses. CONCLUSIONS: Our findings indicate that IL-7 unveils and supports re-activation of pathogen-specific T cells with possible diagnostic, prognostic and therapeutic significance, of clinical value especially in conditions of pathogen persistence and chronic infectio

Gene Birth, Death, Modification, Poaching, Crippling, Dimorphism and Culling: The Challenge for Genomics

This brief survey covers the main events in the evolution of eukaryotic genes in broad brush style. It concentrates on regulatory DNA, an area that has been relatively neglected, and where we believe that the present case-by-case analysis is likely to be supplemented by more general, genomics-based methods. It is biased towards immunology, in part because the immune system relies heavily on polymorphism of regulatory DNA to provide flexibility and in part because of our own field of interest. It gives a central place to recent work that has shown how analysis of electronic genomes can be used to trace gene duplication and its consequences. It mentions cellular systems that offer models for the study of evolution of regulatory DNA on a small scale. It alludes to the unanswered question of how genomes adjust their overall size

Gender differences and age-specific associations between Body Mass Index and other cardiovascular risk factors in CMV infected and uninfected people

Recent studies have highlighted Body Mass Index (BMI) as an important parameter associated with cardiovascular risk and cancer. Here we have explored the relationship between BMI and other cardiovascular risk factors such as white blood count (WBC) and mean arterial blood pressure (MAP) in young (20-35 years) and older (60-85 years) healthy donors stratified by gender and CMV IgG serostatus. We found a positive correlation between BMI and WBC in young women, which was significant in CMV+ women. Interestingly, there was a non-significant opposite trend in young men. In older women the positive trend was preserved in the presence of CMVinfection, but no clear trend was seen in older men. Gender differences were also observed by opposite trends regarding an association between MAP and WBC (positive in young women, negative in young men). These associations were not observed at older ages. However, in CMV+ older men, there was a significant association between MAP and WBC as well as neutrophil count (NC). CRP values were only available in older participants, and interestingly, correlated with WBC and NC only in women, and more closely in CMVwomen. This study reveals that the correlations between common inflammatory markers/cardiovascular risk factors depend on age, gender, and CMV infection status in a complex fashion. Our findings support the need to evaluate risk factors independently in men and women and to take into account CMV infection status. More focused studies will be required to shed light on these novel findings

Interferon γ–independent Rejection of Interleukin 12–transduced Carcinoma Cells Requires CD4+T Cells and Granulocyte/Macrophage Colony– stimulating Factor

We analyzed the ability of interferon (IFN)- γ knockout mice (GKO) to reject a colon carcinoma transduced with interleukin (IL)-12 genes (C26/IL-12). Although the absence of IFN-γ impaired the early response and reduced the time to tumor onset in GKO mice, the overall tumor take rate was similar to that of BALB/c mice. In GKO mice, C26/IL-12 tumors had a reduced number of infiltrating leukocytes, especially CD8 and natural killer cells. Analysis of the tumor site, draining nodes, and spleens of GKO mice revealed reduced expression of IFNinducible protein 10 and monokine induced by γ-IFN. Despite these defects, GKO mice that rejected C26/IL-12 tumor, and mice that were primed in vivo with irradiated C26/IL-12 cells, showed the same cytotoxic T lymphocyte activity but higher production of granulocyte/macrophage colony–stimulating factor (GM-CSF) as compared with control BALB/c mice. Treatment with monoclonal antibodies against GM-CSF abrogated tumor regression in GKO but not in BALB/c mice. CD4 T lymphocytes, which proved unnecessary or suppressive during rejection of C26/IL-12 cells in BALB/c mice, were required for tumor rejection in GKO mice. CD4 T cell depletion was coupled with a decline in GM-CSF expression by lymphocytes infiltrating the tumors or in the draining nodes, and with the reduction and disappearance of granulocytes and CD8 T cells, respectively, in tumor nodules. These results suggest that GM-CSF can substitute for IFN-γ in maintaining the CD8–polymorphonuclear leukocyte cross-talk that is a hallmark of tumor rejection

Cytomegalovirus infection modulates the phenotype and functional profile of the T-cell immune response to mycobacterial antigens in older life

Infection with Cytomegalovirus is associated with accelerated immunosenescence. Expansions of CMV-specific T cell responses have previously been demonstrated to affect the ability of T cells to respond to other infections. Most people above 60 years of age display M. tuberculosis-specific immunity because of vaccination, exposure, or both. T-cell responses can be assessed by measuring intracellular IFN-γ in vitro after tuberculin stimulation. Here we investigated tuberculin-specific CD4 T-cell responses in independently living healthy older people in the South of England using flow-cytometry. Individuals were investigated for tuberculin and CMV-specific T-cell immunity using in vitro antigen stimulation followed by intracellular staining for IFN-γ, TNF-α, IL2, as well as degranulation and CD154 upregulation. We also examined a control group of younger individuals (20–35 years of age). There was no significant difference between older and young people in regards to tuberculin responsiveness of CD4 T-cells; however, older people seemed to show more outliers. Increased responsiveness to tuberculin was significantly correlated to CMV responsiveness but not age. In older donors, the memory phenotype of tuberculin-induced T-cells was significantly skewed towards a more terminal differentiation phenotype in CMV-infected compared to uninfected individuals and the degree of skewing correlated quantitatively with the size of the CMV-specific CD4 T-cell response. This is a fundamental advance over previous reports of changes of the tuberculin-specific CD4 T-cell response with CMV serostatus. Our results show that how the immune system responds to CMV has a fundamental impact on the phenotype and function of the immune response to mycobacterial antigens in older life

CMV-specific T-cell responses at older ages: broad responses with a large central memory component may be key to long-term survival

Cytomegalovirus (CMV) infection sometimes causes large expansions of CMV-specific T-cells, particularly in older people. This is believed to undermine immunity to other pathogens and to accelerate immunosenescence. While multiple different CMV proteins are recognized, most publications on age-related T-cell expansions have focused on dominant target proteins, UL83 or UL123, and the T-cell activation marker, IFN-γ. We were concerned that this narrow approach might have skewed our understanding of CMV-specific immunity at older ages. We have, therefore, widened the scope of analysis to include in vitro-induced T-cell responses to 19 frequently recognized CMV proteins in young and older healthy volunteers and a group of oldest old, long-term survivors (>85 years of age). Polychromatic flow-cytometry was used to analyze T-cell activation markers (CD107, CD154, IL-2, TNF, IFN-γ) and memory phenotype (CD27, CD45RA). The older had on average larger T-cell responses than the young, but, interestingly, response size differences were relatively smaller when all activation markers were considered rather than IFN-γ or TNF alone. The oldest old recognized more proteins on average than the other groups and had even bigger T-cell responses than the older with a significantly larger central memory CD4 T-cell component

Functional diversity of CMV-specific T-cells is maintained in older people and significantly associated with protein specificity and response size

Background: Parallel up-regulation of several T-cell effector functions (‘polyfunctionality’) is believed to be critical for the protection against viruses but thought to decrease in large T-cell expansions, in particular at older ages. The factors determining T-cell polyfunctionality are incompletely understood. Here we revisit the question of CMV-specific T-cell polyfunctionality, including a wide range of T-cell target proteins, response sizes, and participant ages. Methods: Polychromatic flow-cytometry was used to analyze the functional diversity (CD107, CD154, IL-2, TNF, IFN-) of CD4 and CD8 T-cell responses to 19 CMV proteins in a large group of young and older UK participants. A group of oldest old people (>85years) was included to explore these parameters in exceptional ‘survivors’. Polyfunctionality was assessed for each proteinspecific response subset by subset and in aggregate across all proteins using the novel polyfunctionality index (PI). Results: Polyfunctionality was not reduced in healthy older compared to young people. However, it was significantly related to target protein specificity. For each protein it increased with response size. In the oldest old overall T-cell polyfunctionality was significantly lower. Discussion: Our results give a new perspective on T-cell polyfunctionality and raise the question if maintaining polyfunctionality of CMV-specific T-cells at older ages is necessarily beneficial

A Novel Cytomegalovirus-Induced Regulatory-Type T-Cell Subset Increases in Size During Older Life and Links Virus-Specific Immunity to Vascular Pathology

Background. Cytomegalovirus (CMV) infection directly targets vascular endothelium and smooth muscle and at older ages is associated with accelerated vascular pathology and mortality. CMV-specific cellular immunity might directly contribute to this process. Methods. Conventional ex vivo activation–induced T-cell responses to 19 dominant CMV antigens, along with CMV-specific inducible regulatory-type CD4+ T cells (iTregs), were measured in healthy older people, using a novel protocol that included classic Treg markers alongside the activation marker CD134. Measurements were correlated with diastolic, systolic, and mean arterial blood pressure, a surrogate marker for arterial stiffness. Results. CMV-specific iTregs recognized the same antigens as conventional CD4+ T cells and were significantly more frequent at older ages. They suppressed antigen-specific and nonspecific proliferation and in large part expressed Foxp3. Frequencies of CMV-specific iTregs and CD8+ T cells (summated response) were significantly associated with diastolic and mean arterial pressures. Confounders, including age, body mass index, smoking, antihypertensive medication use, or C-reactive protein levels, did not explain these observations. Conclusions. A novel CMV-induced regulatory-type CD4+ T-cell subset is readily detectable in CMV-infected people and, like the aggregate CD8+ T-cell response to the most dominant CMV antigens, is quantitatively associated with arterial stiffness in older life. Whereas CD8+ effector T cells might directly cause vascular injury, iTregs may attenuate this response

CD28null pro-atherogenic CD4 T-cells explain the link between CMV infection and an increased risk of Cardiovascular death

An increased risk of cardiovascular death in Cytomegalovirus (CMV)-infected individuals remains unexplained, although it might partly result from the fact that CMV infection is closely associated with the accumulation of CD28null T-cells, in particular CD28null CD4 T-cells. These cells can directly damage endothelium and precipitate cardiovascular events. However, the current paradigm holds that the accumulation of CD28null T-cells is a normal consequence of aging, whereas the link between these T-cell populations and CMV infection is explained by the increased prevalence of this infection in older people. Resolving whether CMV infection or aging triggers CD28null T-cell expansions is of critical importance because, unlike aging, CMV infection can be treated. Methods: We used multi-color flow-cytometry, antigen-specific activation assays, and HLA-typing to dissect the contributions of CMV infection and aging to the accumulation of CD28null CD4 and CD8 T-cells in CMV+ and CMV− individuals aged 19 to 94 years. Linear/logistic regression was used to test the effect of sex, age, CMV infection, and HLA-type on CD28null T-cell frequencies. Results: The median frequencies of CD28null CD4 T-cells and CD28null CD8 T-cells were >12-fold (p=0.000) but only approximately 2-fold higher (p=0.000), respectively, in CMV+ (n=136) compared with CMV− individuals (n=106). The effect of CMV infection on these T-cell subsets was confirmed by linear regression. Unexpectedly, aging contributed only marginally to an increase in CD28null T-cell frequencies, and only in CMV+ individuals. Interestingly, the presence of HLA-DRB1*0301 led to an approximately 9-fold reduction of the risk of having CD28null CD4 T-cell expansions (OR=0.108, p=0.003). Over 75% of CMV-reactive CD4 T-cells were CD28null. Conclusion: CMV infection and HLA type are major risk factors for CD28null CD4 T-cell-associated cardiovascular pathology. Increased numbers of CD28null CD8 T-cells are also associated with CMV infection, but to a lesser extent. Aging, however, makes only a negligible contribution to the expansion of these T-cell subsets, and only in the presence of CMV infection. Our results open up new avenues for risk assessment, prevention, and treatment