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.

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 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.

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.

Chemokine-mediated tissue recruitment of CXCR3+ CD4+ T cells plays a major role in the pathogenesis of chronic GVHD.

Chemokines regulate the migration of hemopoietic cells and play an important role in the pathogenesis of many immune-mediated diseases. Intradermal recruitment of CD8(+) T cells by CXCL10 is a central feature of the pathogenesis of cutaneous acute GVHD (aGVHD), but very little is known about the pathogenesis of chronic GVHD (cGVHD). Serum concentrations of the 3 CXCR3-binding chemokines, CXCL9, CXCL10, and CXCL11, were found to be markedly increased in patients with active cGVHD of the skin (n = 8). An 80% decrease in CD4(+) cells expressing CXCR3 was seen in the blood of these patients (n = 5), whereas CD4(+) cells were increased in tissue biopsies and were clustered around the central arterioles of the dermis. The well-documented increase in expression of CXCL10 in aGVHD therefore diversifies in cGVHD to include additional members of the CXCR3-binding family and leads to preferential recruitment of CD4(+) T cells. These observations reveal a central role for chemokine-mediated recruitment of CXCR3(+) T cells in cGVHD.

Profile of maternal CD4 T-cell effector function during normal pregnancy and in women with a history of recurrent miscarriage.

The traditional paradigm suggests that during normal pregnancy maternal immunological tolerance of the allogenic fetus is association with a maternal T-lymphocyte shift from a Th1 to a Th2 phenotype, with the opposite effect reported in patients with recurrent miscarriage. However, studies on maternal peripheral blood are conflicting. In the present study, we characterized the maternal CD4 T-cell effector subsets, including the recently described Th17 subset, during normal pregnancy (cross-sectional cohort, n=71; longitudinal cohort, n=17) and contrasted this with women with recurrent miscarriage (n=24). Longitudinal analysis of peripheral blood from normal pregnancy demonstrated a fall in the percentage of Th17 cells between the first and second trimester (P≤0.05), but no significant changes were observed across gestation or the post-natal period in Th1 or Th2 subsets. In contrast, in women with a history of recurrent miscarriage, an elevated proportion of Th17 (0.314% compared with 0.097%; P=0.0009) and Th1 (12.4% compared with 5.3%; P=0.0002) cells was detected. The suggestion that Th17 cells may have a role in the normal events of implantation and early pregnancy requires further evaluation and mechanistic studies. The results of the present study, by conducting a careful longitudinal analysis, demonstrate that a peripheral Th1/Th2 shift is not a requirement for normal pregnancy. By contrast, the profound increase in Th1 and Th17 cells in women with recurrent miscarriage indicates that peripheral immunological dysfunction may be important in this group specifically, and these assays may be important in guiding therapeutic interventions in this group and warrant further investigation to determine whether they are predictive of outcome or responses to immunomodulatory therapy.

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.

Age differentially impacts adaptive immune responses induced by adenoviral versus mRNA vaccines against COVID-19.

Adenoviral and mRNA vaccines encoding the viral spike (S) protein have been deployed globally to contain severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Older individuals are particularly vulnerable to severe infection, probably reflecting age-related changes in the immune system, which can also compromise vaccine efficacy. It is nonetheless unclear to what extent different vaccine platforms are impacted by immunosenescence. Here, we evaluated S protein-specific immune responses elicited by vaccination with two doses of BNT162b2 or ChAdOx1-S and subsequently boosted with a single dose of BNT162b2 or mRNA-1273, comparing age-stratified participants with no evidence of previous infection with SARS-CoV-2. We found that aging profoundly compromised S protein-specific IgG titers and further limited S protein-specific CD4+ and CD8+ T cell immunity as a probable function of progressive erosion of the naive lymphocyte pool in individuals vaccinated initially with BNT162b2. Our results demonstrate that primary vaccination with ChAdOx1-S and subsequent boosting with BNT162b2 or mRNA-1273 promotes sustained immunological memory in older adults and potentially confers optimal protection against coronavirus disease 2019.

The PARP inhibitor olaparib induces significant killing of ATM-deficient lymphoid tumor cells in vitro and in vivo.

The Ataxia Telangiectasia Mutated (ATM) gene is frequently inactivated in lymphoid malignancies such as chronic lymphocytic leukemia (CLL), T-prolymphocytic leukemia (T-PLL), and mantle cell lymphoma (MCL) and is associated with defective apoptosis in response to alkylating agents and purine analogues. ATM mutant cells exhibit impaired DNA double strand break repair. Poly (ADP-ribose) polymerase (PARP) inhibition that imposes the requirement for DNA double strand break repair should selectively sensitize ATM-deficient tumor cells to killing. We investigated in vitro sensitivity to the poly (ADP-ribose) polymerase inhibitor olaparib (AZD2281) of 5 ATM mutant lymphoblastoid cell lines (LCL), an ATM mutant MCL cell line, an ATM knockdown PGA CLL cell line, and 9 ATM-deficient primary CLLs induced to cycle and observed differential killing compared with ATM wildtype counterparts. Pharmacologic inhibition of ATM and ATM knockdown confirmed the effect was ATM-dependent and mediated through mitotic catastrophe independently of apoptosis. A nonobese diabetic/severe combined immunodeficient (NOD/SCID) murine xenograft model of an ATM mutant MCL cell line demonstrated significantly reduced tumor load and an increased survival of animals after olaparib treatment in vivo. Addition of olaparib sensitized ATM null tumor cells to DNA-damaging agents. We suggest that olaparib would be an appropriate agent for treating refractory ATM mutant lymphoid tumors.

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.

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.

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.

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.

Fetal microchimerism: the cellular and immunological legacy of pregnancy.

During pregnancy there is transplacental traffic of fetal cells into the maternal circulation. Remarkably, cells of fetal origin can then persist for decades in the mother and are detectable in the circulation and in a wide range of tissues. Maternal CD8 T cell responses directed against fetal antigens can also be detected following pregnancy. However, the impact that the persistence of allogenic cells of fetal origin and the maternal immune response towards them has on the mother's health remains unclear and is the subject of considerable investigation. The potentially harmful effects of fetal microchimerism include an association with autoimmune disease and recurrent miscarriage. Beneficial effects that have been explored include the contribution of persistent fetal cells to maternal tissue repair. A link between fetal microchimerism and cancer has also been proposed, with some results supporting a protective role and others, conversely, suggesting a role in tumour development. The phenomenon of fetal microchimerism thus provokes many questions and promises to offer further insights not only into the biology of pregnancy but fields such as autoimmunity, transplantation biology and oncology.

Ageing is associated with a decline in peripheral blood CD56bright NK cells.

BACKGROUND: Natural killer (NK) cells are cytotoxic lymphocytes that lack CD3 and express variable levels of CD16, CD56 and CD57. In recent years NK cells have been categorised into two major groups based on the level of CD56 expression. This phenotypic classification correlates with functional activity as CD56bright NK cells are the major cytokine producing subset whereas CD56dim NK cells exhibit greater cytotoxic activity. Previous studies have revealed a reduction in total NK cell numbers in association with ageing and this study sought to determine the potential influence of ageing on the number of NK cell subsets within peripheral blood. RESULTS: The number of NK (CD56+CD3-) cells within peripheral blood did not change with increasing age. The number of CD56dim NK cells also remained stable with ageing. In contrast the absolute number of CD56bright NK cells within peripheral blood declined by 48% with ageing from a mean of 15.6/microl in individuals aged 20-40 years to 8.1/microl in those aged 60+ years (p = 0.0004). CONCLUSION: The number of CD56bright NK cells within peripheral blood declines with age. As this population plays a central role in cytokine secretion during the innate immune response this decline may contribute to impaired immune regulation in elderly individuals.