Systematic analysis of infectious disease outcomes by age shows lowest severity in school-age children

The COVID-19 pandemic has ignited interest in age-specific manifestations of infection but surprisingly little is known about relative severity of infectious disease between the extremes of age. In a systematic analysis we identified 142 datasets with information on severity of disease by age for 32 different infectious diseases, 19 viral and 13 bacterial. For almost all infections, school-age children have the least severe disease, and severity starts to rise long before old age. Indeed, for many infections even young adults have more severe disease than children, and dengue was the only infection that was most severe in school-age children. Together with data on vaccine response in children and young adults, the findings suggest peak immune function is reached around 5-14 years of age. Relative immune senescence may begin much earlier than assumed, before accelerating in older age groups. This has major implications for understanding resilience to infection, optimal vaccine scheduling, and appropriate health protection policies across the life course.

Asymptomatic Primary Infection with Epstein-Barr Virus: Observations on Young Adult Cases

Epstein-Barr virus (EBV) is typically acquired asymptomatically in childhood. In contrast, infection later in life often leads to infectious mononucleosis (IM), a febrile illness characterized by anti-EBV IgM antibody positivity, high loads of circulating latently infected B cells, and a marked lymphocytosis caused by hyperexpansion of EBV-specific CD8+ T cells plus a milder expansion of CD56dim NKG2A+ KIR- natural killer (NK) cells. How the two situations compare is unclear due to the paucity of studies on clinically silent infection. Here we describe five prospectively studied patients with asymptomatic infections identified in a seroepidemiologic survey of university entrants. In each case, the key blood sample had high cell-associated viral loads without a marked CD8 lymphocytosis or NK cell disturbance like those seen in patients during the acute phase of IM. Two of the cases with the highest viral loads showed a coincident expansion of activated EBV-specific CD8+ T cells, but overall CD8+ T cell numbers were either unaffected or only mildly increased. Two cases with slightly lower loads, in whom serology suggests the infection may have been caught earlier in the course of infection, also showed no T or NK cell expansion at the time. Interestingly, in another case with a higher viral load, in which T and NK cell responses were undetectable in the primary blood sample in which infection was detected, EBV-specific T cell responses did not appear until several months later, by which time the viral loads in the blood had already fallen. Thus, some patients with asymptomatic primary infections have very high circulating viral loads similar to those in patients during the acute phase of IM and a cell-mediated immune response that is qualitatively similar to that in IM patients but of a lower magnitude. However, other patients may have quite different immune responses that ultimately could reveal novel mechanisms of host control.IMPORTANCE Epstein-Barr virus (EBV) is transmitted orally, replicates in the throat, and then invades the B lymphocyte pool through a growth-transforming latent infection. While primary infection in childhood is usually asymptomatic, delayed infection is associated with infectious mononucleosis (IM), a febrile illness in which patients have high circulating viral loads and an exaggerated virus-induced immune response involving both CD8+ T cells and natural killer (NK) cells. Here we show that in five cases of asymptomatic infection, viral loads in the blood were as high as those in patients during the acute phase of IM, whereas the cell-mediated responses, even when they resembled those in patients during the acute phase of IM in timing and quality, were never as exaggerated. We infer that IM symptoms arise as a consequence not of the virus infection per se but of the hyperactivated immune response. Interestingly, there were idiosyncratic differences among asymptomatic cases in the relationship between the viral load and the response kinetics, emphasizing how much there is still to learn about primary EBV infection.

Sociodemographic factors associated with IgG and IgM seroprevalence for human cytomegalovirus infection in adult populations of Pakistan: a seroprevalence survey

Background

The seroprevalence of human cytomegalovirus (HCMV) infection ranges from 30 to 90 % in developed countries. Reliable estimates of HCMV seroprevalence are not available for Pakistan. This study determined the seroprevalence and sociodemographic factors associated with HCMV infection in adult populations of Karachi, Pakistan.

Methods

A seroprevalence survey was conducted on 1000 adults, including residents of two semi-urban communities, and visitors to a government and a private hospital. Questionnaire-based interviews were conducted. Sera were analysed for HCMV-specific IgG and IgM. Chi-square or Fisher’s exact test was used for comparing sociodemographic variables against seropositivity of HCMV-IgG or IgM. Multiple logistic regression modeling was performed for IgG seroprevalence and adjusted odds ratios were computed.

Results

The seroprevalence of HCMV-IgG and IgM was 93.2 and 4.3 % respectively. 95.3 % of individuals who were IgM seropositive were also seropositive for IgG. Around 6 % (15/250) of women of childbearing age remained uninfected and were therefore susceptible to primary infection. HCMV-IgG seroprevalence was associated with being female (p = 0.001), increasing age (p = 0.002) and crowding index (p = 0.003) and also with lower levels of both education (p < 0.001) and income (p = 0.008). Seroprevalence also differed significantly by marital status (p = 0.008) and sampling location (p < 0.001). A logistic regression model for HCMV-IgG seroprevalence showed associations with being female (OR = 1.89; 95 % CI: 1.10–3.25), increasing age (OR = 3.95; 95 % CI: 1.79–8.71) and decreasing income (OR = 0.72; 95 % CI: 0.54–0.96). A strong association was observed between increased seroprevalence of HCMV-IgM and decreasing household size (p = 0.008).

Conclusions

Seroprevalence of HCMV is very high in Pakistan, although 6 % of women of childbearing age remain at risk of primary infection. The IgM seropositivity observed in some individuals living in small household size (1–3 individuals) with persistent HCMV infection could have resulted from a recurrent HCMV infection. Future longitudinal research in pregnant women and neonates is required to study the trends in HCMV seroprevalence over time in Pakistan for the development of a potential HCMV prevention and vaccination programme.

Cytomegalovirus infection does not impact on survival or time to first treatment in patients with chronic lymphocytic leukemia

Human cytomegalovirus (HCMV) is a widely prevalent herpes virus which establishes a state of chronic infection. The establishment of CMV‐specific immunity controls viral reactivation and leads to the accumulation of very large numbers of virus‐specific T cells which come to dominate the immune repertoire. There is concern that this may reduce the immune response to heterologous infections and HCMV infection has been associated with reduced survival in elderly people. Patients with chronic lymphocytic leukemia (B‐CLL) suffer from a state of immune suppression but have a paradoxical increase in the magnitude of the CMV‐specific T cell and humoral immune response. As such, there is now considerable interest in how CMV infection impacts on the clinical outcome of patients with B‐CLL. Utilizing a large prospective cohort of patients with B‐CLL (n = 347) we evaluated the relationship between HCMV seropositivity and patient outcome. HCMV seropositive patients had significantly worse overall survival than HCMV negative patients in univariate analysis (HR = 2.28, 95% CI: 1.34–3.88; P = 0.002). However, CMV seropositive patients were 4 years older than seronegative donors and this survival difference was lost in multivariate modeling adjusted for age and other validated prognostic markers (P = 0.34). No significant difference was found in multivariate modeling between HCMV positive and negative patients in relation to the time to first treatment (HR = 1.12, 95% CI: 0.68–1.84; P = 0.65). These findings in a second independent cohort of 236 B‐CLL patients were validated. In conclusion no evidence that HCMV impacts on the clinical outcome of patients with B‐CLL was found. Am. J. Hematol. 91:776–781, 2016. © 2016 Wiley Periodicals, Inc.

The Cellular Localization of Human Cytomegalovirus Glycoprotein Expression Greatly Influences the Frequency and Functional Phenotype of Specific CD4+ T Cell Responses

CMV infection is a significant cause of morbidity and mortality in immunocompromised individuals, and the development of a vaccine is of high priority. Glycoprotein B (gB) is a leading vaccine candidate but the glycoprotein H (gH) pentameric complex is now recognized as the major target for neutralizing Abs. However, little is known about the T cell immune response against gH and glycoprotein L (gL) and this is likely to be an important attribute for vaccine immunogenicity. In this study, we examine and contrast the magnitude and phenotype of the T cell immune response against gB, gH, and gL within healthy donors. gB-specific CD4(+) T cells were found in 95% of donors, and 29 epitopes were defined with gB-specific response sizes ranging from 0.02 to 2.88% of the CD4(+) T cell pool. In contrast, only 20% of donors exhibited a T cell response against gH or gL. Additionally, gB-specific CD4(+) T cells exhibited a more cytotoxic phenotype, with high levels of granzyme B expression. Glycoproteins were effectively presented following delivery to APCs but only gB-derived epitopes were presented following endogenous synthesis. gB expression was observed exclusively within vesicular structures colocalizing with HLA-DM whereas gH was distributed evenly throughout the cytoplasm. Grafting of the C-terminal domain from gB onto gH could not transfer this pattern of presentation. These results reveal that gB is a uniquely immunogenic CMV glycoprotein and this is likely to reflect its unique pattern of endogenous Ag presentation. Consideration may be required toward mechanisms that boost cellular immunity to gH and gL within future subunit vaccines.

Progesterone promotes maternal-fetal tolerance by reducing human maternal T-cell polyfunctionality and inducing a specific cytokine profile

Progesterone is a steroid hormone essential for the maintenance of human pregnancy, and its actions are thought to include promoting maternal immune tolerance of the semiallogenic fetus. We report that exposure of maternal T cells to progesterone at physiological doses induced a unique skewing of the cytokine production profile of CD4⁺ and CD8⁺ T cells, with reductions not only in potentially deleterious IFN‐γ and TNF‐α production but also in IL‐10 and IL‐5. Conversely, production of IL‐4 was increased. Maternal T cells also became less polyfunctional, focussing cytokine production toward profiles including IL‐4. This was accompanied by reduced T‐cell proliferation. Using fetal and viral antigen‐specific CD8⁺ T‐cell clones, we confirmed that this as a direct, nonantigen‐specific effect. Yet human T cells lacked conventional nuclear progesterone receptors, implicating a membrane progesterone receptor. CD4⁺ and CD8⁺ T cells responded to progesterone in a dose‐dependent manner, with subtle effects at concentrations comparable to those in maternal blood, but profound effects at concentrations similar to those at the maternal–fetal interface. This characterization of how progesterone modulates T‐cell function is important in understanding the normal biology of pregnancy and informing the rational use of progesterone therapy in pregnancies at risk of fetal loss.

Cytomegalovirus drives Vδ2neg γδ T cell inflation in many healthy virus carriers with increasing age

Cytomegalovirus (CMV) usually causes lifelong asymptomatic infection, but over time can distort immune profiles. Recent reports describe selective expansion of Vδ2^neg γδ T cells in healthy and immunocompromised CMV carriers. Having shown previously that virus-specific CD8⁺ and CD4⁺ T cell responses are increased significantly in elderly CMV carriers, probably driven by chronic stimulation, we hypothesized that Vδ2^neg γδ T cells may also be expanded with age. Our results show that Vδ2^neg γδ T cells are increased significantly in CMV-seropositive healthy individuals compared to CMV-seronegative controls in all age groups. The differences were most significant in older age groups (P < 0·0001). Furthermore, while Vδ2^neg γδ T- cells comprise both naive and memory cells in CMV-seronegative donors, highly differentiated effector memory cells are the dominant phenotype in CMV carriers, with naive cells reduced significantly in numbers in CMV-seropositive elderly. Although phenotypically resembling conventional CMV-specific T cells, Vδ2^neg γδ T cells do not correlate with changes in magnitude of CMV-specific CD4⁺ or CD8⁺ T cell frequencies within those individuals, and do not possess ex-vivo immediate effector function as shown by CMV-specific CD4⁺ and CD8⁺ T cells. However, after short-term culture, Vδ2^neg γδ T cells demonstrate effector T cell functions, suggesting additional requirements for activation. In summary, Vδ2^neg γδ T cells are expanded in many older CMV carriers, demonstrating a further level of lymphocyte subset skewing by CMV in healthy individuals. As others have reported shared reactivity of Vδ2^neg γδ T cells towards tumour cells, the composition of γδ T cell subsets may also have implications for risk of developing cancer in elderly people.

Cytomegalovirus infection is associated with increased mortality in the older population

Cytomegalovirus (CMV) is a common herpesvirus infection and stimulates the expansion of very large numbers of CMV-specific T cells that reduce the CD4/CD8 ratio and suppress the number of naïve T cells. CMV infection has been associated with frailty and impaired survival. We investigated the correlates of CMV and the impact of the CMV infection on mortality within a cohort of 511 individuals aged at least 65 years who were followed up for 18 years. The mean age of the participants was 74 years of which 70% were CMV-seropositive. CMV was strongly linked to socio-economic status, and CMV infection increased the annual mortality rate by 42% (Hazard ratio = 1.42, 95% CI: 1.11-1.76 after adjusting for age, sex and baseline socio-economic and health variables) corresponding to 3.7 years lower life expectancy from age 65. Infection was associated with a near doubling of cardiovascular deaths, whereas there was no increase in mortality from other causes. These results show that CMV infection markedly increases the mortality rate in healthy older individuals due to an excess of vascular deaths. These findings may have significant implications for the study of immune senescence and if confirmed more generally could have important implications for measures to optimize the health of the elderly.

Fetal-specific CD8+ cytotoxic T cell responses develop during normal human pregnancy and exhibit broad functional capacity

Tolerance of the semiallogeneic fetus presents a significant challenge to the maternal immune system during human pregnancy. T cells with specificity for fetal epitopes have been detected in women with a history of previous pregnancy, but it has been thought that such fetal-specific cells were generally deleted during pregnancy as a mechanism to maintain maternal tolerance of the fetus. We used MHC-peptide dextramer multimers containing an immunodominant peptide derived from HY to identify fetal-specific T cells in women who were pregnant with a male fetus. Fetal-specific CD8(+) T lymphocytes were observed in half of all pregnancies and often became detectable from the first trimester. The fetal-specific immune response increased during pregnancy and persisted in the postnatal period. Fetal-specific cells demonstrated an effector memory phenotype and were broadly functional. They retained their ability to proliferate, secrete IFN-γ, and lyse target cells following recognition of naturally processed peptide on male cells. These data show that the development of a fetal-specific adaptive cellular immune response is a normal consequence of human pregnancy and that unlike reports from some murine models, fetal-specific T cells are not deleted during human pregnancy. This has broad implications for study of the natural physiology of pregnancy and for the understanding of pregnancy-related complications.

Structural and energetic evidence for highly peptide-specific tumor antigen targeting via allo-MHC restriction

Immunotherapies targeting peptides presented by allogeneic MHC molecules offer the prospect of circumventing tolerance to key tumor-associated self-antigens. However, the degree of antigen specificity mediated by alloreactive T cells, and their ability to discriminate normal tissues from transformed cells presenting elevated antigen levels, is poorly understood. We examined allorecognition of an HLA-A2-restricted Hodgkin's lymphoma-associated antigen and were able to isolate functionally antigen-specific allo-HLA-A2-restricted T cells from multiple donors. Binding and structural studies, focused on a prototypic allo-HLA-A2-restricted T-cell receptor (TCR) termed NB20 derived from an HLA-A3 homozygote, suggested highly peptide-specific allorecognition that was energetically focused on antigen, involving direct recognition of a distinct allopeptide presented within a conserved MHC recognition surface. Although NB20/HLA-A2 affinity was unremarkable, TCR/MHC complexes were very short-lived, consistent with suboptimal TCR triggering and tolerance to low antigen levels. These data provide strong molecular evidence that within the functionally heterogeneous alloreactive repertoire, there is the potential for highly antigen-specific "allo-MHC-restricted" recognition and suggest a kinetic mechanism whereby allo-MHC-restricted T cells may discriminate normal from transformed tissue, thereby outlining a suitable basis for broad-based therapeutic targeting of tolerizing tumor antigens.

Chronic lymphocytic leukaemia cells drive the global CD4+ T cell repertoire towards a regulatory phenotype and leads to the accumulation of CD4+ forkhead box P3+ T cells

Advanced chronic lymphocytic leukaemia (CLL) is associated with profound immunodeficiency, including changes in T regulatory cells (T(regs)). We determined the pattern of expression of forkhead box P3 (FoxP3), CD25, CD27 and CD127 and showed that the frequency of CD4+ FoxP3+ T cells was increased in CLL patients (12% versus 8% in controls). This increase was seen only in advanced disease, with selective expansion of FoxP3-expressing cells in the CD4+ CD25(low) population, whereas the number of CD4+ CD25(high) FoxP3+ cells was unchanged. CD4+ CD25(low) cells showed reduced expression of CD127 and increased CD27, and this regulatory phenotype was also seen on all CD4 T cells subsets in CLL patients, irrespective of CD25 or FoxP3 expression. Incubation of CD4+ T cells with primary CLL tumours led to a sixfold increase in the expression of FoxP3 in CD4+ CD25- T cells. Patients undergoing treatment with fludarabine demonstrated a transient increase in the percentage of CD4+ FoxP3+ T cells, but this reduced to normal levels post-treatment. This work demonstrates that patients with CLL exhibit a systemic T cell dysregulation leading to the accumulation of CD4+ FoxP3+ T cells. This appears to be driven by interaction with malignant cells, and increased understanding of the mechanisms that are involved could provide novel avenues for treatment.

Cytomegalovirus sero positivity dramatically alters the maternal CD8+ T cell repertoire and leads to the accumulation of highly differentiated memory cells during human pregnancy

BACKGROUND

Human pregnancy offers an immunological challenge for the immunocompetent women accommodating an allogenic fetus, while continuing to combat potentially infectious disease. Cytomegalovirus (CMV) infects the majority of the human population and establishes lifelong persistence, which can lead to the oligoclonal expansion of differentiated T cells. Primary CMV infection and, less commonly, secondary infection during pregnancy can cause fetal disease and morbidity. The balance between maternal immune competence and viral pathogenicity is thus delicately poised. Our objective was to investigate the influence of CMV serostatus on maternal CD8+ T-cell phenotype and cytokine profile in an apparently healthy cohort of pregnant women. Furthermore, we assessed if CMV serostatus modulated changes in CD8 T cells during gestation.

METHODS

CD8+ T-cell phenotype was investigated in 87 pregnant women with samples obtained both during pregnancy [CMV immunoglobulin G (IgG) + n = 39, CMV IgG- n = 21] and in the early post-natal period (IgG+ n = 16, IgG- n = 11). Multiparameter flow cytometry was used to study T-cell phenotype and HLA-peptide tetramers identified CD8 T cells specific for CMV. Levels of 26 plasma cytokines, chemokines and chemokine receptors were assessed in a separate cohort of 20 women (IgG+ n = 10, IgG- n = 10) followed longitudinally during and after pregnancy.

RESULTS

CMV seropositivity profoundly influenced the T cell repertoire and its dynamics during pregnancy. Naïve CD8+ T-cells (CCR7+CD45RA+) were reduced by 50% in CMV-seropositive women. The proportion of CD45RA effector cells was not increased in CMV-seropositive donors, although this population was more highly differentiated with reduced CD27 and CD28. However, there was a doubling in the proportion of CD45RA+ revertant memory cells (CCR7-CD45RA+) in seropositive donors. Moreover, seropositive women during late pregnancy demonstrated an accumulation of highly differentiated CMV-specific T-cells. T-cell activation independent of CMV was also seen in late pregnancy. No CMV-related changes in plasma cytokines, chemokines or their receptors were observed.

CONCLUSIONS

Thus, CMV serostatus is a crucial consideration in studies of T cell memory and differentiation during pregnancy. The reduction in maternal naïve T cells in CMV-seropositive donors could have implications for the maternal response to infections during pregnancy. These findings shed light on the delicate balance between host, fetus and chronic infection during healthy pregnancy and will inform studies in relation to the importance of CMV on maternal and fetal health.

Persistent viral infection in humans can drive high frequency low-affinity T-cell expansions

CD8 T cells that recognize cytomegalovirus (CMV) -encoded peptides can be readily detected by staining with human leucocyte antigen (HLA) -peptide tetramers. These cells are invariably highly differentiated effector memory cells with high avidity T-cell receptors (TCR). In this report we demonstrate an HLA-A*0201 restricted CMV-specific CD8 T-cell response (designated YVL) that represents several percent of the CD8 T-cell subset, yet fails to bind tetrameric major histocompatibility complex (MHC) ligands. However, these tetramer-negative cells are both phenotypically and functionally similar to other CMV-specific CD8 T cells. YVL peptide-specific CD8 T-cell clones were generated and found to be of high avidity in both cytotoxicity and interferon-γ (IFN-γ) assays, and comparable with other CMV peptide-specific CD8 T-cell clones. However, under conditions of CD8 blockade, the response was almost nullified even at very high ligand concentrations. This was also the case in IFN-γ experiments using peripheral blood mononuclear cells stimulated with peptide ex vivo. In contrast, all other CMV specificities (tetramer-positive) displayed minimal or only partial CD8 dependence. This suggests that YVL-specific responses depict a low-affinity TCR-MHC-peptide interaction, that is compensated by substantial CD8 involvement for functional purposes, yet cannot engage multivalent soluble ligands for ex vivo analysis. It is interesting that such a phenomenon is apparent in the face of a persistent virus infection such as CMV, where the responding cells represent an immunodominant response in that individual and may present a highly differentiated effector phenotype.

CD8(+) T-cell immunity against cancer-testis antigens develops following allogeneic stem cell transplantation and reveals a potential mechanism for the graft-versus-leukemia effect

BACKGROUND

Allogeneic stem cell transplantation is associated with a powerful 'graft-versus-leukemia' effect that is generally considered to result from an alloreactive T-cell immune response. However, disease remission can also be observed after syngeneic transplantation and we investigated whether a T-cell immune response to cancer-testis antigens can be detected in patients in the post-transplant period.

DESIGN AND METHODS

The T-cell immune response against cancer-testis antigens was studied in a cohort of 41 patients who underwent allogeneic stem cell transplantation for the management of acute myeloid leukemia or multiple myeloma. The cytokine secretion assay was combined with magnetic selection to allow detection of an interferon-gamma-secreting T-cell response to a panel of cancer-testis antigen peptides.

RESULTS

A cancer-testis antigen-specific CD8(+) T-cell immune response was observed in the peripheral blood of five patients with an average magnitude of 0.045% of the CD8(+) T-cell repertoire. Four of these patients had undergone reduced intensity conditioning transplantation with alemtuzumab for the treatment of acute myeloid leukemia and three remain in long-term remission. T-cell immunity was focused against peptides derived from MAGE proteins and was markedly increased within the bone marrow.

CONCLUSIONS

Functional cancer-testis antigen-specific CD8(+) T-cell immune responses develop in the early period following reduced intensity allogeneic stem cell transplantation and are preferentially localized to bone marrow. These immune responses are likely to contribute to the cellular basis of the graft-versus-leukemia effect.

Secondary anchor polymorphism in the HA-1 minor histocompatibility antigen critically affects MHC stability and TCR recognition

T cell recognition of minor histocompatibility antigens (mHags) underlies allogeneic immune responses that mediate graft-versus-host disease and the graft-versus-leukemia effect following stem cell transplantation. Many mHags derive from single amino acid polymorphisms in MHC-restricted epitopes, but our understanding of the molecular mechanisms governing mHag immunogenicity and recognition is incomplete. Here we examined antigenic presentation and T-cell recognition of HA-1, a prototypic autosomal mHag derived from single nucleotide dimorphism (HA-1(H) versus HA-1(R)) in the HMHA1 gene. The HA-1(H) peptide is restricted by HLA-A2 and is immunogenic in HA-1(R/R) into HA-1(H) transplants, while HA-1(R) has been suggested to be a "null allele" in terms of T cell reactivity. We found that proteasomal cleavage and TAP transport of the 2 peptides is similar and that both variants can bind to MHC. However, the His>Arg change substantially decreases the stability and affinity of HLA-A2 association, consistent with the reduced immunogenicity of the HA-1(R) variant. To understand these findings, we determined the structure of an HLA-A2-HA-1(H) complex to 1.3A resolution. Whereas His-3 is accommodated comfortably in the D pocket, incorporation of the lengthy Arg-3 is predicted to require local conformational changes. Moreover, a soluble TCR generated from HA-1(H)-specific T-cells bound HA-1(H) peptide with moderate affinity but failed to bind HA-1(R), indicating complete discrimination of HA-1 variants at the level of TCR/MHC interaction. Our results define the molecular mechanisms governing immunogenicity of HA-1, and highlight how single amino acid polymorphisms in mHags can critically affect both MHC association and TCR recognition.

Persistence of fetal cells in the mother: friend or foe?

There is increasing evidence that both circulating cells and free fetal DNA persist in the maternal circulation after delivery of the fetus. In some cases, this has been described many years after the end of the pregnancy. This article reviews the evidence for these cells being present, the potential methodologies used to identify such cells and the potential effects on maternal immunomodulation. Data relating to the potential beneficial and potentially harmful effects are discussed.

The CD4+ T-cell response to adenovirus is focused against conserved residues within the hexon protein

Adenovirus is a significant pathogen in immunocompromised patients and is widely utilized as a gene delivery vector, so a detailed understanding of the human immune response to adenovirus infection is critical. This study characterized the adenovirus-specific CD4+ T-cell response of healthy donors by incubation with whole virus or with individual hexon and fiber proteins. Adenovirus-specific CD4+ T cells averaged 0.26 % of the CD4+ T-cell pool and were detectable in all donors. T cells recognizing the highly conserved hexon protein accounted for 0.09 %, whereas no response was observed against the fiber protein. A panel of hexon-specific CD4+ T-cell clones was generated and shown to lyse targets infected with adenovirus from different serotypes and species. Three CD4 T-cell epitopes are described, which map to highly conserved regions of the hexon protein.

CXCL10-CXCR3 interactions play an important role in the pathogenesis of acute graft-versus-host disease in the skin following allogeneic stem-cell transplantation

Acute graft-versus-host disease (aGVHD) remains a serious complication following allogeneic stem-cell transplantation (SCT), and is mediated by infiltration of alloreactive donor T cells into recipient tissue. Chemokines and their receptors play a central role in controlling the recruitment of T cells into discrete tissue sites, and determine the clinical features of GVHD in murine models. In this study, we have analyzed the serum concentration of molecules that control leukocyte migration in serial samples from 34 patients following allogeneic SCT. The chemokine CXCL10 (IP-10) was significantly elevated (> 2-fold) in serum at the time of aGVHD. Because the ligand for CXCL10 is CXCR3, the number of CXCR3(+) T cells was determined in peripheral blood, but was not increased during episodes of GVHD. To investigate the role of chemokines in the recruitment of T cells to the anatomic site of GVHD, skin biopsies were stained for CXCL10 and CXCR3 expression. CXCL10 expression was observed in the basal keratinocytes of the epidermis in patients with GVHD together with positive staining for CXCR3 on cells in dermal infiltrates. These findings indicate that CXCL10 plays a central role in the pathogenesis of skin aGVHD by the recruitment of CXCR3(+) T cells to the sites of inflammation.

T cell recognition patterns of immunodominant cytomegalovirus antigens in primary and persistent infection

Replication of human cytomegalovirus is controlled by a vigorous CD8 T cell response. The persistent nature of infection is believed to periodically stimulate T cell responses resulting in considerable expansions of virus-specific CD8 T cells over time. In this study, we describe the magnitude and breadth of CD8 T cell responses against the immunodominant viral Ags, IE-1 and pp65, in acute and long-term infection using the IFN-gamma ELISPOT assay. Simultaneously, we have identified several novel MHC class I restricted CD8 T cell epitopes. Acute phase responses in immunocompetent donors appear to be extremely focused as early as 1 week post diagnosis with dominant peptide-specific responses observed against both proteins. These dominant responses remain detectable at all later time points over a 4-year follow-up. Interestingly the IE-1 responses show an increase over time whereas the pp65 responses do not, which contrasts with data showing that responses against both Ags are elevated in elderly individuals. We also observe the rapid emergence of an effector memory phenotype for virus-specific CD8 T cells as observed in persistent infection. Over time the revertant CD45RA(pos) effector cell population is also expanded, and this is more evident in the preferentially expanded IE-1 responses. We postulate that periodic low-level virus reactivation after the acute infection phase preferentially stimulates these responses whereas pp65-specific T cell expansions probably occur during the infrequent episodes of lytic viral replication or secondary infection.

The cytomegalovirus-specific CD4+ T-cell response expands with age and markedly alters the CD4+ T-cell repertoire

Immune function in the elderly is associated with a number of phenotypic and functional abnormalities, and this phenomenon of immune senescence is associated with increased susceptibility to infection. The immune response to pathogens frequently declines with age, but the CD8(+) T-cell response to cytomegalovirus (CMV) is unusual, as it demonstrates a significant expansion over time. Here we have documented the CD4(+) T-cell immune response to CMV in healthy donors of different ages. The magnitude of the CMV-specific CD4(+) T-cell immune response increases from a mean of 2.2% of the CD4(+) T-cell pool in donors below 50 years of age to 4.7% in donors aged over 65 years. In addition, CMV-specific CD4(+) T cells in elderly donors demonstrate decreased production of interleukin-2 and less dependence on costimulation. CMV seropositivity is associated with marked changes in the phenotype of the overall CD4(+) T-cell repertoire in healthy aged donors, including an increase in CD57(+) expression and a decrease in CD28 and CD27 expression, a phenotypic profile characteristic of immune senescence. This memory inflation of CMV-specific CD4(+) T cells contributes to evidence that CMV infection may be damaging to immune function in elderly individuals.

EBV-associated mononucleosis leads to long-term global deficit in T-cell responsiveness to IL-15

In mice, interleukin-7 (IL-7) and IL-15 are involved in T-cell homeostasis and the maintenance of immunologic memory. Here, we follow virus-induced responses in infectious mononucleosis (IM) patients from primary Epstein-Barr virus (EBV) infection into long-term virus carriage, monitoring IL-7 and IL-15 receptor (IL-R) expression by antibody staining and cytokine responsiveness by STAT5 phosphorylation and in vitro proliferation. Expression of IL-7Ralpha was lost from all CD8+ T cells, including EBV epitope-specific populations, during acute IM. Thereafter, expression recovered quickly on total CD8+ cells but slowly and incompletely on EBV-specific memory cells. Expression of IL-15Ralpha was also lost in acute IM and remained undetectable thereafter not just on EBV-specific CD8+ populations but on the whole peripheral T- and natural killer (NK)-cell pool. This deficit, correlating with defective IL-15 responsiveness in vitro, was consistently observed in patients up to 14 years after IM but not in patients after cytomegalovirus (CMV)-associated mononucleosis, or in healthy EBV carriers with no history of IM, or in EBV-naive individuals. By permanently scarring the immune system, symptomatic primary EBV infection provides a unique cohort of patients through which to study the effects of impaired IL-15 signaling on human lymphocyte functions in vitro and in vivo.

Adoptive transfer of cytomegalovirus-specific CTL to stem cell transplant patients after selection by HLA-peptide tetramers

Stem cell transplantation is used widely in the management of a range of diseases of the hemopoietic system. Patients are immunosuppressed profoundly in the early posttransplant period, and reactivation of cytomegalovirus (CMV) remains a significant cause of morbidity and mortality. Adoptive transfer of donor-derived CMV-specific CD8+ T cell clones has been shown to reduce the rate of viral reactivation; however, the complexity of this approach severely limits its clinical application. We have purified CMV-specific CD8+ T cells from the blood of stem cell transplant donors using staining with HLA-peptide tetramers followed by selection with magnetic beads. CMV-specific CD8+ cells were infused directly into nine patients within 4 h of selection. Median cell dosage was 8.6 x 10(3)/kg with a purity of 98% of all T cells. CMV-specific CD8+ T cells became detectable in all patients within 10 d of infusion, and TCR clonotype analysis showed persistence of infused cells in two patients studied. CMV viremia was reduced in every case and eight patients cleared the infection, including one patient who had a prolonged history of CMV infection that was refractory to antiviral therapy. This novel approach to adoptive transfer has considerable potential for antigen-specific T cell therapy.

A novel CDK inhibitor, CYC202 (R-roscovitine), overcomes the defect in p53-dependent apoptosis in B-CLL by down-regulation of genes involved in transcription regulation and survival

B-cell chronic lymphocytic leukemia (B-CLL) is a clinically variable disease where mutations in DNA damage response genes ATM or TP53 affect the response to standard therapeutic agents. The in vitro cytotoxicity of a novel cyclin-dependent kinase inhibitor, CYC202, was evaluated in 26 B-CLLs, 11 with mutations in either the ATM or TP53 genes, and compared with that induced by ionizing radiation and fludarabine. CYC202 induced apoptosis within 24 hours of treatment in all 26 analyzed tumor samples independently of ATM and TP53 gene status, whereas 6 of 26 B-CLLs, mostly ATM mutant, showed marked in vitro resistance to fludarabine-induced apoptosis. Compared with B-CLLs, normal T and B lymphocytes treated with CYC202 displayed reduced and delayed apoptosis. Using global gene expression profiling, we found that CYC202 caused a significant down-regulation of genes involved in regulation of transcription, translation, survival, and DNA repair. Furthermore, induction of apoptosis by CYC202 was preceded by inhibition of RNA polymerase II phosphorylation, leading to down-regulation of several prosurvival proteins. We conclude that CYC202 is a potent inducer of apoptosis in B-CLL regardless of the functional status of the p53 pathway, and may be considered as a therapeutic agent to improve the outcome of resistant B-CLL tumors.

Virus-specific cytotoxic T lymphocytes differentially express cell-surface leukocyte immunoglobulin-like receptor-1, an inhibitory receptor for class I major histocompatibility complex molecules

Leukocyte immunoglobulin-like receptor-1 (LIR-1) is an inhibitory receptor that negatively regulates T cell effector functions after interaction with host class I major histocompatibility complex molecules and, additionally, binds to UL18, a human cytomegalovirus (HCMV)-encoded class I homologue. Here, we demonstrate that virus-specific cytotoxic T lymphocytes (CTLs) differentially express LIR-1, with high frequencies of expression on HCMV-specific CD8+ T cells and intermediate and low frequencies of expression on influenza virus-specific and Epstein-Barr virus (EBV)-specific CTLs, respectively. Expression of LIR-1 was dependent on CTL-antigen specificity and was associated with a differentiated effector memory phenotype, as demonstrated by decreased expression of CD28 and increased expression of CD57. During primary HCMV and EBV infections, expression of LIR-1 on virus-specific CTLs was low and increased slowly. These results indicate that expression of LIR-1 increases during differentiation of virus-specific CD8+ effector T cells. Furthermore, they suggest that a potential immunoregulatory function of UL18 may be to preferentially target highly differentiated HCMV-specific effector memory T cells during persistent infection.

Identification of cytomegalovirus-specific cytotoxic T lymphocytes in vitro is greatly enhanced by the use of recombinant virus lacking the US2 to US11 region or modified vaccinia virus Ankara expressing individual viral genes

Cytomegalovirus (CMV) elicits a potent T-cell response in humans that appears to protect the host from virus-associated disease. Despite facing strong host defense mechanisms, CMV remains as a lifelong infection that may reactivate and cause life-threatening disease in immunocompromised individuals. This persistence is probably assisted by expression of immune subversion proteins of the virus encoded by genes belonging to the US gene family. These proteins modulate major histocompatibility complex expression in infected cells and bias in vitro experiments toward the detection of only certain specificities. We have combined the use of recombinant CMV, lacking the US2 to US11 region genes, and cytoplasmic gamma interferon staining to define a more accurate assessment of CMV-specific responses in vivo. Recombinant CMV stimulation reveals a CD8 response much larger than that of parental virus in all donors tested. In some cases, this represented up to 10-fold increases in the number of cells detected. Responses were directed mainly against pp65, IE-1, and pp50 in the majority of donors. In addition, previously unreported IE-2-specific T-cell responses could be detected in a minority of cases. Furthermore, we observed a less marked increase in the response to mutant CMV by CD4 T cells in some donors. This suggests that a much broader T-cell response to CMV exists in vivo than is revealed by restimulation with wild-type virus and adds to the evidence that the efficacy of immune evasion strategies may not be as absolute as previously believed.

Adenovirus infections in stem cell transplant recipients: recent developments in understanding of pathogenesis, diagnosis and management

Adenovirus is increasingly recognized as an important pathogen in stem cell transplant recipients, reflecting increased awareness about the virus, together with changes in transplant practice such as the performance of more high-risk transplants, and improvements in diagnostic methods. In retrospective studies, the reported incidence of adenovirus infections ranged between 4-20% with a similar variation in the proportion of patients developing invasive disease. In contrast, the incidence of adenovirus infection varies between 20-30% in recent prospective studies on T-cell depleted or mismatched allografts and about 30-40% of these patients develop invasive disease. These prospective studies have established a relationship between the risk of invasive adenovirus disease and a number of factors such as the extent of T-cell depletion, the intensity of immunosuppressive therapy and the kinetics of lymphocyte recovery post-transplant. Polymerase chain reaction (PCR) assays to detect adenovirus DNA in peripheral blood have shown a strong correlation between viremia and the risk of disseminated adenovirus disease. These developments have led to the possibility of a preemptive antiviral treatment strategy for asymptomatic adenovirus infections. In addition, a better understanding of the interactions between adenovirus and host immune system in the post-transplant setting might enable development of effective immunotherapeutic strategies against adenovirus infections.

Herpesvirus-Specific CD8 T Cell Immunity in Old Age: Cytomegalovirus Impairs the Response to a Coresident EBV Infection

Aging in humans is associated with increased infections and the reduced proliferative capacity of T cells, part of the more global phenomenon termed immune senescence. The etiology of immune senescence is unknown but the accumulation of virus-specific memory T cells may be a contributory factor. We have examined CD8 T cell responses to two persistent herpesvirus infections, CMV and EBV, and to a recurrent virus infection, influenza, in different age cohorts of healthy donors using HLA-peptide tetramers and intracellular cytokine detection. Of these, CMV appears to be the most immunogenic, with the CD8 T cell response representing over 10% of the CD8 pool in many elderly donors. Interestingly, the effect of age upon EBV-specific responses depends upon donor CMV sero-status. In CMV seropositive donors, the magnitude of the EBV-specific immune response is stable with age, but in CMV seronegative donors, the response to EBV increases significantly with age. By contrast, the influenza-specific CD8 T cell immune response decreases with age, independent of CMV status. The functional activity of the herpesvirus-specific immune response decreases in elderly donors, although the characteristic phenotypes of CMV- and EBV-specific memory populations are retained. This demonstrates that aging is associated with a marked accumulation of CMV-specific CD8 T cells together with a decrease in immediate effector function. Moreover, infection with CMV can reduce prevailing levels of immunity to EBV, another persistent virus. These results suggest that carriage of CMV may be detrimental to the immunocompetent host by suppressing heterologous virus-specific immunity during aging.

Apoptotic resistance to ionizing radiation in pediatric B-precursor acute lymphoblastic leukemia frequently involves increased NF-kappaB survival pathway signaling

To investigate possible causes of the variable response to treatment in pediatric B-precursor acute lymphoblastic leukemia (ALL) and to establish potential novel therapeutic targets, we used ionizing radiation (IR) exposure as a model of DNA damage formation to identify tumors with resistance to p53-dependent apoptosis. Twenty-one of 40 ALL tumors responded normally to IR, exhibiting accumulation of p53 and p21 proteins and cleavage of caspases 3, 7, and 9 and of PARP1. Nineteen tumors exhibited apoptotic resistance and lacked PARP1 and caspase cleavage; although 15 of these tumors had normal accumulation of p53 and p21 proteins, examples exhibited abnormal expression of TRAF5, TRAF6, and cIAP1 after IR, suggesting increased NF-kappaB prosurvival signaling as the mechanism of apoptotic resistance. The presence of a hyperactive PARP1 mutation in one tumor was consistent with such increased NF-kappaB activity. PARP1 inhibition restored p53-dependent apoptosis after IR in these leukemias by reducing NF-kappaB DNA binding and transcriptional activity. In the remaining 4 ALL tumors, apoptotic resistance was associated with a TP53 mutation or with defective activation of p53. We conclude that increased NF-kappaB prosurvival signaling is a frequent mechanism by which B-precursor ALL tumors develop apoptotic resistance to IR and that PARP1 inhibition may improve the DNA damage response of these leukemias.

Microarray analysis reveals that TP53- and ATM-mutant B-CLLs share a defect in activating proapoptotic responses after DNA damage but are distinguished by major differences in activating prosurvival responses

The ATM/p53-dependent DNA damage response pathway plays an important role in the progression of lymphoid tumors. Inactivation of the ATM or TP53 gene is frequent in B-cell lymphocytic leukemia (B-CLL) and leads to aggressive disease. Although the ATM and p53 pathways overlap, they are not congruent, and it is unclear how the mechanism of tumor progression differs between ATM- and p53-deficient tumors. Using microarray analysis of ATM-mutant, TP53-mutant, and ATM/TP53 wild-type B-CLLs, we show that after exposure to DNA damage transcriptional responses are entirely dependent on ATM function. The p53 proapoptotic responses comprise only a part of ATM-regulated transcription; additionally, ATM regulates prosurvival responses independently of p53. Consequently, the greater severity of the TP53-mutant B-CLLs compared with ATM-mutant B-CLLs is consistent with the additive effect of defective apoptotic and elevated survival responses after DNA damage in these tumors. We also show that transcription expression profiles of ATM-deficient, TP53-deficient, and wild-type B-CLLs are indistinguishable before irradiation. Therefore, damage-induced transcriptional fingerprinting can be used to stratify tumors according to their biologic differences and simultaneously identify potential targets for treating refractory tumors.

The cellular immunotherapy of viral infection

Viral infections remain a major problem for the patient who has undergone a stem cell transplant and the introduction of increasingly more intensive SCT regimens suggests that this will remain a significant concern for the immediate future. Advances in basic immunology have led to an improved understanding of how immune responses control individual viral infections and this information is now being directly applied to patient care with encouraging results. The application of cellular immunotherapy to the immunocompromised patient is one of the most exciting areas of clinical medicine and offers the prospect of significant clinical impact.

The impact of donor KIR and patient HLA-C genotypes on outcome following HLA-identical sibling hematopoietic stem cell transplantation for myeloid leukemia

Killer immunoglobulin-like receptors (KIRs) regulate cell activity of natural killer (NK) cells and some T cells. The predominant ligand for inhibitory KIRs is HLA-C, which subdivides into 2 groups based on the specificity of inhibitory KIRs. The ligands for activatory KIRs are unknown. Following hematopoietic stem cell transplantation (HSCT), recipient tissues may not express a ligand for KIRs present within the graft, and the combination of donor KIR and recipient HLA-C types could influence outcome. HLA and KIR genotypes were determined in 220 donor-recipient pairs from HLA-matched sibling HSCTs performed for myeloid (n = 112) and lymphoid (n = 108) diseases. In HSCTs performed for myeloid disease, overall survival was worse in patients homozygous for group 2 HLA-C (C2) than in patients who carried a group 1 HLA-C (C1) allele (P <.005). Moreover, this effect is seen only when the donor additionally carries the activating KIR gene KIR2DS2 (P =.045). No effect was seen in patients with lymphoid disease. Thus, in HLA-matched sibling HSCT for myeloid leukemia, patients homozygous for C2 alleles receiving a graft from a donor carrying the KIR gene KIR2DS2 have a significantly reduced chance of survival.

Variations in ATM protein expression during normal lymphoid differentiation and among B-cell-derived neoplasias

The ataxia telangiectasia mutated (ATM) protein plays a central role in the cellular response to DNA double-strand breaks (DSBs). Developmentally programmed DSBs are restricted to cellular subsets within lymphoid tissues and we asked whether ATM expression is differentially regulated during lymphoid differentiation. We showed that immature B cells in bone marrow and immature T cells of the thymic cortex were negative or weakly ATM-positive. T cells of thymic medulla and peripheral tissues strongly expressed ATM. High levels of ATM were present in the B lymphocytes of the mantle zone and in plasma cells, while the majority of germinal center B cells were negative or weakly labeled. Therefore, ATM expression appears to be down-regulated at those stages of lymphoid development where physiological DNA DSBs occur. In B-chronic lymphocytic leukemia and mantle cell lymphoma we observed two categories: ATM-negative tumors, most likely reflecting the presence of ATM mutation, and tumors with abundant ATM expression. Most follicular center-cell lymphomas and diffuse large B-cell lymphomas, which rarely show inactivation of the ATM gene, were negative or weakly ATM-positive. Tumor cells from most cases of Hodgkin's disease were ATM-negative. Therefore, unless ATM inactivation occurs, ATM expression in lymphoid tumors is likely to reflect their cellular origin. As a result, immunostaining to identify lymphoid neoplasias with ATM inactivation might only be feasible for tumors derived from the stages where ATM is constitutively highly expressed.

Differential regulation of vitamin D receptor and its ligand in human monocyte-derived dendritic cells

The functions of dendritic cells (DCs) are tightly regulated such that protective immune responses are elicited and unwanted immune responses are prevented. 1 alpha 25-dihydroxyvitamin D(3) (1 alpha 25(OH)(2)D(3)) has been identified as a major factor that inhibits the differentiation and maturation of DCs, an effect dependent upon its binding to the nuclear vitamin D receptor (VDR). Physiological control of 1 alpha 25(OH)(2)D(3) levels is critically dependent upon 25-hydroxyvitamin D(3)-1 alpha-hydroxylase (1 alpha OHase), a mitochondrial cytochrome P450 enzyme that catalyzes the conversion of inactive precursor 25-hydroxyvitamin D(3) (25(OH)D(3)) to the active metabolite 1 alpha 25(OH)(2)D(3). Using a human monocyte-derived DC (moDC) model, we have examined the relationship between DC VDR expression and the impact of exposure to its ligand, 1 alpha 25(OH)(2)D(3). We show for the first time that moDCs are able to synthesize 1 alpha 25(OH)(2)D(3) in vitro as a consequence of increased 1 alpha OHase expression. Following terminal differentiation induced by a diverse set of maturation stimuli, there is marked transcriptional up-regulation of 1 alpha OHase leading to increased 1 alpha OHase enzyme activity. Consistent with this finding is the observation that the development and function of moDCs is inhibited at physiological concentrations of the inactive metabolite 25(OH)D(3). In contrast to 1 alpha OHase, VDR expression is down-regulated as monocytes differentiate into immature DCs. Addition of 1 alpha 25(OH)(2)D(3) to moDC cultures at different time points indicates that its inhibitory effects are greater in monocyte precursors than in immature DCs. In conclusion, differential regulation of endogenous 1 alpha 25(OH)(2)D(3) ligand and its nuclear receptor appear to be important regulators of DC biology and represent potential targets for the manipulation of DC function.

The distribution of 13 killer-cell immunoglobulin-like receptor loci in UK blood donors from three ethnic groups

Killer-cell immunoglobulin-like receptors (KIRs) can inhibit the killing activity of natural killer (NK) cells if they interact with their ligand, class I HLA. Using a modified polymerase chain reaction-sequence-specific primers (PCR-SSP) method for typing KIRs using genomic DNA, we compared KIR frequencies in three ethnic populations drawn from UK blood donors. We found a significantly lower frequency of the inhibitory KIRs KIR2DS1 and 3DS1 in Afro-Caribbean blood donors. Despite this, there was a (non-significant) increase in the B haplotype in Afro-Caribbean and Indian Asian donors. Some donors from each group tested negative for all non-inhibitory KIRs. In addition, we describe several new KIR profiles. Analysis of linkage disequilibrium was consistent with previously published findings.

Human CD34+ hematopoietic progenitor cells hyperacetylate core histones in response to sodium butyrate, but not trichostatin A

Cells positive for the cell surface marker CD34 from bone marrow or umbilical cord blood form a subset of quiescent, hematopoetic precursors that can establish human hematopoesis in immunodeficient mice and can progress down various differentiation pathways in vitro. They provide a valuable model system in which progression from quiescent to cycling to differentiated states can be linked to changes in chromatin and histone modification. We have used the deacetylase inhibitor sodium butyrate to show that turnover of histone H4 acetates is rapid and comparable in quiescent and cycling CD34+ cells from human umbilical cord blood (CD34+ UBC). Surprisingly, the widely used inhibitor trichostatin A (TSA) had little (cycling cells) or no (quiescent cells) effect on H4 acetylation in CD34+ UBC. Among five cell types examined, CD34+ UBC were unique in expressing all (putative) deacetylases tested (HDAC1, -2, -3, -4, -6, -7, and -8 and SIRT1-4), but no single deacetylase correlated with their TSA resistance. Also, HDAC1, -2, -3, and -6 complexes isolated from CD34+ UBC by immunoprecipitation were all inhibited by TSA in vitro. Thus, TSA resistance of CD34+ UBC is not due to acquired or intrinsic TSA resistance of their deacetylases and may reflect an enhanced ability to process the drug.

Adenovirus infections following allogeneic stem cell transplantation: incidence and outcome in relation to graft manipulation, immunosuppression, and immune recovery

Adenovirus infections occur in 5% to 21% of patients following stem cell transplantation (SCT), with an associated mortality of up to 50%. However, a lack of prospective studies has hampered further developments in the understanding and management of this infection in the posttransplantation setting. We prospectively studied the incidence and outcome of adenovirus infections after SCT using preemptive screening and a policy of reduction or withdrawal of immunosuppressive therapy if the virus was isolated. The incidence of adenovirus infection was 19.7% (15 of 76), and the virus was isolated exclusively in recipients of T-cell-depleted grafts. Patients receiving 50 or 100 mg alemtuzumab in vivo were at the greatest risk of adenovirus infection (45% probability) regardless of donor type, and this was related to the slower lymphocyte recovery. Six (40%) of the 15 adenovirus-infected patients developed adenovirus disease. Severe lymphocytopenia (less than 300/microL) at the time of first detection of adenovirus was a major risk factor for development of adenovirus disease (P =.001). In addition, failure to reduce immunosuppression (P =.04) and a positive result of adenovirus polymerase chain reaction (PCR) in blood at diagnosis (P =.01) were both associated with fatal adenovirus disease. On the basis of this study, we recommend active surveillance for adenovirus infection in T-cell-depleted SCT and withdrawal or reduction of immunosuppressive treatment, if possible, in patients with adenovirus infection. Preemptive antiviral therapy is warranted for patients with severe lymphocytopenia or positive blood PCR, and in those in whom immunosuppressive therapy cannot be reduced.

B cells immortalized by a mini-Epstein-Barr virus encoding a foreign antigen efficiently reactivate specific cytotoxic T cells

Lymphoblastoid cell lines (LCLs) are human B cells latently infected and immortalized by Epstein-Barr virus (EBV). Presenting viral antigens, they efficiently induce EBV-specific T-cell responses in vitro. Analogous ways to generate T-cell cultures specific for other antigens of interest are highly desirable. Previously, we constructed a mini-EBV plasmid that consists of less than half the EBV genome, is unable to cause virus production, but still immortalizes B cells in vitro. Mini-EBV-immortalized B-cell lines (mini-LCLs) are efficiently produced by infection of B cells with viruslike particles carrying only mini-EBV DNA. Mini-EBV plasmids can be engineered to express an additional gene in immortalized B cells. Here we present a mini-EBV coding for a potent CD8(+) T-cell antigen, the matrix phosphoprotein pp65 of human cytomegalovirus (CMV). By means of this pp65 mini-EBV, pp65-expressing mini-LCLs could be readily established from healthy donors in a one-step procedure. We used these pp65 mini-LCLs to reactivate and expand effector T cells from autologous peripheral blood cells in vitro. When generated from cytomegalovirus (CMV)-seropositive donors, these effector T-cell cultures displayed strong pp65-specific HLA-restricted cytotoxicity. A large fraction of CD8(+) T cells with pp65 epitope specificity was present in such cultures, as demonstrated by direct staining with HLA/peptide tetramers. We conclude that the pp65 mini-EBV is an attractive tool for CMV-specific adoptive immunotherapy. Mini-EBVs could also facilitate the generation of T cells specific for various other antigens of interest.

Cytomegalovirus seropositivity drives the CD8 T cell repertoire toward greater clonality in healthy elderly individuals

The deterioration in immune function with aging is thought to make a major contribution to the increased morbidity and mortality from infectious disease in old age. One aspect of immune senescence is the reduction in CD8 T cell repertoire as due to the accumulation of oligoclonal, memory T cells and a reduction in the naive T cell pool. CD8 T cell clonal expansions accumulate with age, but their antigenic specificity remains unknown. In this study, we show that in elderly individuals seropositivity for human CMV leads to the development of oligoclonal populations of CMV-specific CTL that can constitute up to one-quarter of the total CD8 T cell population. Furthermore, CMV-specific CTL have a highly polarized membrane phenotype that is typical of effector memory cells (CD28(-), CD57(+), CCR7(-)). TCR analyses show that CMV-specific CTL have highly restricted clonality with greater restriction in the larger expansions. Clonal analysis of the total CD8 T cell repertoire was compared between CMV-seropositive and CMV-seronegative donors. Thirty-three percent more clonal expansions were observed in CMV-seropositive donors in comparison with seronegative individuals. These data implicate CMV as a major factor in driving oligoclonal expansions in old age. Such a dramatic accumulation of virus-specific effector CTL might impair the ability to respond to heterologous infection and may underlie the negative influence of CMV seropositivity on survival in the very elderly.

ATM mutations in sporadic lymphoid tumours

Patients with the autosomal recessive disorder ataxia telangiectasia (A-T) show the biallelic inactivation of the ataxia telangiectasia mutated (ATM) gene. A-T patients exhibit a predisposition to the development of a wide range of lymphoid tumours, suggesting that the ATM protein normally plays an important role in the prevention of both T and B cell malignancies. The ATM protein is a 370 kDa protein kinase implicated in the integration of different cellular responses to particular forms of DNA damage. Several recent studies have reported the possibility that the ATM gene can act as a tumour suppressor gene in non A-T individuals. Frequent ATM inactivation was confirmed in three sporadic lymphoid tumours of mature phenotype: T cell prolymphocytic leukaemia (T-PLL), B-cell chronic lymphocytic leukaemia (B-CLL) and mantle cell lymphoma (MCL). Here, we provide a summary of the published ATM mutations in sporadic lymphoid tumours, including our own study on the role of ATM mutations in the pathogenesis of sporadic B-CLL. The published results suggest possible differences in the origin, the nature and distribution of ATM mutations between sporadic B-CLL, MCL and T-PLL. While ATM mutations in mature B cell tumours (B-CLL and MCL) represent a mixture of missense and truncating errors distributed across the whole of the ATM coding sequence, mutations in sporadic T-PLL appear to be predominantly missense, clustering in the region encoding the PI-3 kinase catalytic domain of the protein. The reason for this difference is unclear, but the difference itself supports the notion that the pathogenesis of B and T cell tumours on an ATM deficient background might be different. In addition, in both B-CLL and MCL ATM mutation carriers have been reported, raising the possibility that ATM mutation carriers may have an increased risk of developing these tumours. The existence as well as magnitude of the risk, however, remains to be established. Furthermore, our own studies indicate that the presence of ATM mutations in sporadic B-CLL causes a distinctive defect in response to DNA damaging agents, offering a possible explanation for the poor response of ATM mutant tumours to standard treatment. Therefore, one of the future challenges will be to devise strategies to bypass the existing defect in response to DNA damage and activate apoptosis in ATM mutant sporadic lymphoid tumours.

Comparative analysis of CD8+ T cell responses against human cytomegalovirus proteins pp65 and immediate early 1 shows similarities in precursor frequency, oligoclonality, and phenotype

CD8+ T cells are key effectors of the immune response against human cytomegalovirus (HCMV). A number of HCMV-derived CD8+ T cell epitopes are known. Using epitope prediction and subsequent testing for interferon-gamma responses by the ELISPOT assay, we identified an optimal human leukocyte antigen (HLA)-A*0201-restricted CD8+ T cell epitope derived from the major immediate early 1 (IE-1) gene product. As many as one-third of HLA-A*0201-positive, HCMV-seropositive donors make responses to this peptide (residues 316-324 [VLEETSVML]), which can exceed responses against a published immunodominant pp65 epitope (residues 495-503 [NLVPMVATV]). Major histocompatibility complex peptide tetramer staining facilitated detailed phenotypic analyses and revealed populations that resemble terminally differentiated effector cells (CD57+ and CD28-), with considerable restriction in T cell receptor beta-chain variable region use. The results confirm that, although pp65 is a major target for CD8+ T cells, the IE-1 protein may itself stimulate comparable responses in some persons.

Ataxia telangiectasia mutated-deficient B-cell chronic lymphocytic leukemia occurs in pregerminal center cells and results in defective damage response and unrepaired chromosome damage

B-cell chronic lymphocytic leukemia (B-CLL) is a heterogeneous disease involving more than one molecular mechanism that leads to the transformation of CD5(+) B cells at either the pregerminal or postgerminal center stage of differentiation. It was previously demonstrated that ataxia telangiectasia mutated (ATM) gene mutations can occur in B-CLL and cause a defect in the p53 pathway. Here the role of ATM mutations in the pathogenesis of B-CLL is addressed. Of 50 B-CLL tumors with fully analyzed ATM and TP53, 16 had ATM mutations. Six of 50 B-CLLs showed mutations in TP53 and the remaining 28 tumors had wild-type ATM or TP53. No tumor had both ATM and TP53 mutations. Remarkably, all 16 ATM mutant B-CLLs showed the absence of somatic variable region heavy chain hypermutation indicating a pregerminal center cell origin and a common pathogenesis for these tumors. Furthermore, in 5 of the 16 B-CLLs, ATM mutation preceded the transformation stage of differentiation. At the cellular level, ATM mutant tumors exhibited a deficient ATM-dependent p53 response to gamma irradiation, failure to up-regulate TRAIL-R2, a downstream target that links irradiation-induced p53 response with apoptosis, and an inability to repair induced chromosome breaks. Mantle cell lymphoma (MCL) is also of pregerminal center origin and ATM mutations are frequent in this malignancy. It is concluded that ATM is likely to play an important role at the pregerminal center stage and a model is proposed where loss of ATM function during B-cell ontogeny drives B-CLL tumorigenesis in pregerminal B cells by a dual defect in p53 damage response and repair of chromosome breaks.