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Regulatory T cells (Tregs) control immune homeostasis by preventing inappropriate responses to self and non-harmful foreign antigens. Tregs use multiple mechanisms to control immune responses, all of which require Tregs to be near their targets of suppression, but how Treg-to-target proximity is controlled is unknown. We found that Tregs produce chemokines to attract CD4+ and CD8+ T cells close to their proximity in vitro and in vivo. Mouse and human lineage committed Tregs, as well as murine in vitro induced Tregs, produced CCL3 and CCL4 at message and protein level. Chemokine producing Tregs had an activated Treg phenotype with high expression of multiple proteins associated with suppressive function. Furthermore the human CCL3 and CCL4 promoter could be transactivated by FOXP3. In vitro and in vivo migration experiments indicated that CCR5 was the major receptor required by target cells. CCL3 and CCL4 deficient Tregs were impaired in their ability to prevent experimental autoimmune encephalomyelitis or islet allograft rejection, but suppressive in a standard in vitro assay. Moreover, Tregs from subjects with established type 1 were impaired in their ability to produce CCL3 and CCL4. These results demonstrate a previously unknown facet of Treg function and suggest that chemokine secretion by Tregs is a fundamental aspect of their in vivo function and therapeutic effect in autoimmunity and transplantation.

Mutations in SH2D1A gene that encodes SAP (SLAM-associated protein) result in X-linked lymphoproliferative disease (XLP), a rare primary immunodeficiency defined by exquisite sensitivity to the B-lymphotropic Epstein-Barr virus (EBV) and B cell lymphomas. However, the precise mechanism of how the loss of SAP function contributes to extreme vulnerability to EBV and the development of B cell lymphomas remains unclear. Here, we utilized SAP-deficient (Sh2d1a−/−) mice to investigate the hypothesis that SAP is critical for CD8 T cell immune surveillance of antigen-expressing B cells or B lymphoma cells. Sh2d1a−/− CD8 T cells exhibited greatly diminished proliferation relative to wild type when antigen-presenting-B cells or -B lymphoma cells served as the primary APC. By contrast, Sh2d1a−/− CD8 T cells responded equivalently to wild type CD8 T cells when B cell-depleted splenocytes, melanoma cells or breast carcinoma cells performed antigen presentation. Through application of SLAM family receptor blocking antibodies or SLAM family receptor-deficient CD8 T cells and APCs, we found that CD48 engagement on the B cell surface by 2B4 is crucial for initiating SAP-dependent signaling required for the antigen-driven CD8 T cell proliferation and differentiation. Altogether, a pivotal role for SAP in promoting the expansion and differentiation of B cell-primed viral-specific naïve CD8 T cells may explain the selective immune deficiency of XLP patients to EBV and B cell lymphomas.

The regulatory mechanisms involved in VEGF-C secretion by trophoblasts during placentation are poorly understood. We investigated whether or not decidual natural killer cell conditioned medium (dNK-CM) stimulated VEGF-C secretion in the extravillous cytotrophoblast (EVT) cell line HTR8/SVneo.The effects of dNK-CM and recombinant IFN-γ on VEGF-C induction by HTR8/SVneo were studied in the absence or presence of IFN-γ or its receptor blocking antibodies, p38 inhibitor (SB202190), JAK inhibitor (JAK inhibitor-1, JI-1), and on STAT1 knockdown HTR8/SVneo. VEGF-C was quantified by ELISA. FACS was used to investigate the phosphorylations of Tyr701 or Ser727 of STAT1 on stimulated HTR8/SVneo.dNK-CM facilitated VEGF-C secretion by HTR8/SVneo. IFN-γ and IFN-γR1 or IFN-γR2 blocking antibodies reduced both dNK-CM- and IFN-γ-induced VEGF-C secretion. Phosphorylations on Tyr701 or Ser727 of STAT1 were elevated upon stimulation. Secretion of VEGF-C was reduced by treatment with SB202190, JI-1, or STAT1 knockdown by siRNA.VEGF-C production by trophoblasts is regulated by soluble factors secreted by dNK through p38 and JAK-STAT1 pathways.

Summary The transport of calcium ions (Ca 2+ ) to the cytosol is essential for immunoreceptor signaling, regulating lymphocyte differentiation, activation, and effector function. Increases in cytosolic-free Ca 2+ concentrations are thought to be mediated through two interconnected and complementary mechanisms: the release of endoplasmic reticulum Ca 2+ "stores" and "store-operated" Ca 2+ entry via plasma membrane channels. However, the identity of molecular components conducting Ca 2+ currents within developing and mature T cells is unclear. Here, we have demonstrated that the L-type "voltage-dependent" Ca 2+ channel Ca V 1.4 plays a cell-intrinsic role in the function, development, and survival of naive T cells. Plasma membrane Ca V 1.4 was found to be essential for modulation of intracellular Ca 2+ stores and T cell receptor (TCR)-induced rises in cytosolic-free Ca 2+ , impacting activation of Ras-extracellular signal-regulated kinase (ERK) and nuclear factor of activated T cells (NFAT) pathways. Collectively, these studies revealed that Ca V 1.4 functions in controlling naive T cell homeostasis and antigen-driven T cell immune responses.

Autoimmune diabetes in NOD mice can be prevented by application of Ags derived from Mycobacterium tuberculosis in the form of bacillus Calmette-Guérin or CFA. Disease protection by CFA is associated with a reduction in the numbers of pathogenic β-cell specific, self-reactive CTLs, a phenomenon dependent on the presence and function of NK cells. However, the mechanisms by which NK cells are activated and recruited by heat-killed M. tuberculosis within CFA are unclear. In this study, we report that CFA-mediated NK cell activation and mobilization is dependent on CD1d expression. The administration of M. tuberculosis from CFA results in rapid NKT cell activation and IFN-γ secretion both in vitro and in vivo. CFA-induced NKT cell activation is intact in MyD88−/− mice suggesting that the mechanism is independent of TLR signaling. Furthermore, CD1d expression was found to be essential for both M. tuberculosis-triggered NKT cell activation and CFA-mediated protection of NOD mice from diabetes. Collectively, these findings reveal hitherto previously unidentified roles for NKT cells in the adjuvant-promoting effects of CFA on innate and adaptive immunity.

OBJECTIVE Natural killer (NK) cells from NOD mice have numeric and functional abnormalities, and restoration of NK cell function prevents autoimmune diabetes in NOD mice. However, little is known about the number and function of NK cells in humans affected by type 1 diabetes. Therefore, we evaluated the phenotype and function of NK cells in a large cohort of type 1 diabetic children. RESEARCH DESIGN AND METHODS Peripheral blood mononuclear blood cells were obtained from subjects whose duration of disease was between 6 months and 2 years. NK cells were characterized by flow cytometry, enzyme-linked immunosorbent spot assays, and cytotoxicity assays. Signaling through the activating NK cell receptor, NKG2D, was assessed by immunoblotting and reverse-phase phosphoprotein lysate microarray. RESULTS NK cells from type 1 diabetic subjects were present at reduced cell numbers compared with age-matched, nondiabetic control subjects and had diminished responses to the cytokines interleukin (IL)-2 and IL-15. Analysis before and after IL-2 stimulation revealed that unlike NK cells from nondiabetic control subjects, NK cells from type 1 diabetic subjects failed to downregulate the NKG2D ligands, major histocompatibility complex class I–related chains A and B, upon activation. Moreover, type 1 diabetic NK cells also exhibited decreased NKG2D-dependent cytotoxicity and interferon-γ secretion. Finally, type 1 diabetic NK cells showed clear defects in NKG2D-mediated activation of the phosphoinositide 3-kinase–AKT pathway. CONCLUSIONS These results are the first to demonstrate that type 1 diabetic subjects have aberrant signaling through the NKG2D receptor and suggest that NK cell dysfunction contributes to the autoimmune pathogenesis of type 1 diabetes.

CD4+FOXP3+ regulatory T cells are essential for immune tolerance, and murine studies suggest that their dysfunction can lead to type 1 diabetes (T1D). Human studies assessing regulatory T cell dysfunction in T1D have relied on analysis of FOXP3-expressing cells. Recently, distinct subsets of CD4+FOXP3+ T cells with differing function were identified. Notably, CD45RA−CD25intFOXP3low T cells lack suppressive function and secrete the proinflammatory cytokine IL-17. Therefore, we evaluated whether the relative fractions of CD4+FOXP3+ subsets are altered in new-onset T1D subjects. We report that children with new-onset T1D have an increased proportion of CD45RA−CD25intFOXP3low cells that are not suppressive and secrete significantly more IL-17 than other FOXP3+ subsets. Moreover, these T1D subjects had a higher proportion of both CD4+ and CD8+ T cells that secrete IL-17. The bias toward IL-17–secreting T cells in T1D suggests a role for this proinflammatory cytokine in the pathogenesis of disease.

Extravillous cytotrophoblast (EVT) migration, invasion and endovascular differentiation are regulated by a variety of growth factors, cytokines and adhesion molecules. Decidual natural killer cells (dNK) and their secreted cytokines probably modulate these processes. In this study, we used dNK-derived conditioned medium (dNK-CM) to investigate whether or not (i) dNK-CM was able to enhance capillary tube and network formation of an EVT cell line, HTR8/SVneo, on Matrigel, (ii) PI3K/AKT pathway and p38 MAPK pathway activation were involved, and (iii) HTR8/SVneo surface ICAM-1 played a role in the process of HTR8/SVneo endovascular differentiation. The results demonstrated that HTR8/SVneo constitutively form 'vascular' tubes and networks after culture on Matrigel. dNK-CM enhanced and maintained tube and network formation, acquiring an endothelium-like angiogenic morphology followed by increased VEGF-C production. HTR8/SVneo cell expression level of VE-cadherin, PECAM-1, VCAM-1 and alphavbeta3 was unaltered by dNK-CM, whereas ICAM-1 expression level was increased. Anti-human ICAM-1 blocking antibody inhibited HTR8/SVneo migration and partially reversed dNK-CM-mediated enhancement of HTR8/SVneo tube and network formation. PI3K/AKT and p38 MAPK pathways were activated in dNK-CM-mediated enhancement of HTR8/SVneo tube and network formation. The PI3K/AKT and p38 MAPK pathway inhibitors (LY294002 and SB202190, respectively) decreased dNK-CM-stimulated ICAM-1 induction, HTR8/SVneo migration, and reversed tube and network formation. The results suggest that dNK cell-secreted growth factors and cytokines participate in the regulation of HTR8/SVneo endothelium-like tube formation. Adhesion molecules, particularly ICAM-1, expressed on EVT may participate in the process. To our knowledge, this is the first report of a role for ICAM-1 in EVT angiogenesis, as previously reported for endothelial cells.

This FOCIS Centers of Excellence Short Analytical Review is based on the clinical vignette of two boys from the same family with very different outcomes following hematopoietic stem cell transplantation (HSCT) for X-linked severe combined immunodeficiency (SCID). We review the kinetics of immune reconstitution following HSCT in SCID and emphasize the latest information regarding optimizing transplant outcomes for this disorder. The cases illustrate the difficulties and controversies surrounding the optimal strategies for planning SCID transplants. Specifically, we will focus on 3 areas of current debate and investigation: (i) factors involved in donor selection; (ii) the role of pretransplant conditioning; and (iii) benefits of early HSCT for SCID.

Autoimmune diabetes in nonobese diabetic (NOD) mice can be prevented by a single injection of complete Freund's adjuvant (CFA), but the mechanisms mediating protection remains unclear. We previously showed that NOD mice immunized with CFA have a markedly reduced incidence of diabetes that is associated with a significant decrease in the number of beta-cell-specific, autoreactive cytotoxic T lymphocytes and, furthermore, that the effect of CFA is mediated by natural killer (NK) cells. In this study, we report one mechanism by which NK cells regulate the onset of diabetes. Administration of CFA produced a rapid increase in NK cell frequency and function, including cytotoxicity and IFN-gamma secretion. By co-transferring NK cells from IFN-gamma-deficient (or wild-type) NOD mice and spleen cells from diabetic NOD mice to NOD/SCID recipients, we show that IFN-gamma secretion by NK cells significantly influences the effect of CFA protection. In contrast, NK cytotoxicity does not appear to participate in CFA-mediated protection from diabetes. Our findings demonstrate that NK cells mediate the protective effects of CFA through secretion of IFN-gamma.

Epstein-Barr virus (EBV) poses serious health consequences for immunocompromised individuals, such as patients undergoing transplant or chemotherapeutic regimens, and is strongly associated with an expanding list of human cancers. To gain insight into immunity against EBV, a rare congenital immunodeficiency defined by exquisite sensitivity to EBV but not other pathogens called X-linked lymphoproliferative disease, a syndrome caused by mutations in the SH2D1A gene that encodes SLAM-associated protein (SAP), has been the subject of intense investigation. The unique B cell tropism of EBV led us to speculate that SAP and SLAM family receptors are especially critical for optimal CD8 T cell immunity against antigen-expressing B cells and B lymphoma cells. Consistent with this hypothesis, Sh2d1a-/- CD8 T cells exhibited greatly diminished proliferation and effector functions relative to wild type CD8 T cells when cultured with antigen-coated B cells or B lymphoma cells in vitro. By contrast, both wild type and Sh2d1a-/- CD8 T cells responded robustly when stimulated with either antigen-coated B cell-depleted splenocytes or antigen-presenting tumor cells lacking SLAM family receptor expression. Collectively, these observations suggest that the recognition of SLAM family receptors on the surface of antigen presenting-B cells and -B lymphoma cells are essential for antigen priming and immunosurveillance by CD8 T cells.

Cytotoxic T-lymphocytes (CTLs) are considered to be essential for β-cell destruction in type 1 diabetes. However, few islet-associated peptides have been demonstrated to activate autoreactive CTLs from type 1 diabetic subjects. In an effort to identify novel epitopes, we used matrix-assisted algorithms to predict peptides of glial fibrillary acidic protein (GFAP), prepro-islet amyloid polypeptide (ppIAPP), and islet-specific glucose-6-phosphatase catalytic subunit–related protein (IGRP) that likely bind to HLA-A*0201 with a strong affinity and contain a COOH-terminal proteasomal cleavage site. Seven peptides stabilized HLA-A*0201 expression in binding assays and were used to stimulate peripheral blood mononuclear cells and were evaluated for granzyme B secretion. We found that 5 of 13 type 1 diabetic subjects and 4 of 6 antibody-positive relatives exhibited greater numbers of granzyme B–secreting cells in response to at least one putative epitope compared with healthy control subjects. The most prevalent responses in antibody-positive and type 1 diabetic subjects were to ppIAPP(9-17). Other peptides recognized by type 1 diabetic or antibody-positive subjects included GFAP(143-151), IGRP(152-160), and GFAP(214-222). These data implicate peptides of ppIAPP, GFAP, and IGRP as CTL epitopes for a heterogenous CD8+ T-cell response in type 1 subjects and antibody-positive relatives.

community has followed the period of excitement created by the identification of members of the chemokine receptor family as essential co-receptors for the en- try of HIV into CD4+T cells. This in- formation has now been absorbed and is prompting new insights into HIV pathogenesis and potential for new treatment. One key area of research has been to examine how expression of the principal co- receptors [CCR5 for macrophage- tropic (M-tropic), non-syncytium- inducing (NSI) virus; CXCR4 for T cell line-tropic, syncytium-inducing (SI) strains] might be regulated. At first, studies were limited to mRNA expression, but the use of an emerging armoury of specific mono- clonal antibodies, in combination with other T-cell markers, has

Allotransplantation of pancreatic islets represents a promising approach to treat type 1 diabetes. Destruction of beta-cells in islet allografts involves multiple immune mechanisms that lead to activation of caspases and apoptotic cell death. The X-linked inhibitor of apoptosis (XIAP) inhibits apoptosis induced by a variety of triggers, primarily by preventing the activation of caspases. To determine whether XIAP would protect beta-cells from apoptosis, we used a recombinant adenovirus to overexpress XIAP in transformed murine beta-cells and in freshly isolated islets. In vitro cytokine-induced beta-cell death was decreased to baseline levels in XIAP-transduced MIN-6 and NIT-1 cell lines compared with controls. To evaluate the potential of XIAP overexpression to prevent in vivo allogeneic graft rejection, we transduced Balb/c islets ex vivo with XIAP before transplantation into CBA mice with streptozotocin-induced diabetes. We observed that almost all mice receiving allografts of XIAP-expressing islets maintained normoglycemia until the experiment was terminated (45-72 days posttransplant), whereas control mice receiving islets transduced with adenovirus expressing LacZ were hyperglycemic by approximately 17 days posttransplantation due to graft rejection. Immunohistochemistry revealed preservation of beta-cells and clearance of infiltrating immune cells in the XIAP-expressing islet grafts. The in vitro allogeneic response of splenocytes isolated from recipients of XIAP-expressing grafts 8 weeks posttransplant was similar to that seen in nonprimed allogeneic mice, suggesting that XIAP overexpression may lead to the acceptance of islet allografts in diabetic recipients. Long-term protection of islet allografts by XIAP overexpression may enhance the survival of islet transplants in diabetes.

NK cells from individuals with X-linked lymphoproliferative (XLP) disease exhibit functional defects when stimulated through the NK receptor, 2B4 (CD244). These defects are likely a consequence of aberrant intracellular signaling initiated by mutations of the adaptor molecule SLAM-associated protein. In this report, we show that NK cells from individuals with XLP but not healthy individuals fail to phosphorylate and thereby inactivate glycogen synthase kinase-3 (GSK-3) following 2B4 stimulation. Lack of GSK-3 phosphorylation prevented the accumulation of the transcriptional coactivator β-catenin in the cytoplasm and its subsequent translocation to the nucleus. Potential signaling pathways leading from 2B4 stimulation to GSK-3 phosphorylation were also investigated. Ligation of 2B4 resulted in the phosphorylation of the guanine nucleotide exchange factor, Vav-1, and subsequent activation of the GTP-binding protein Rac-1 (but not Ras) and the serine-threonine kinase Raf-1 in healthy but not XLP-derived NK cells. In addition, the activity of MEK-2 (but not MEK-1) was up-regulated, and Erk1/2 was phosphorylated in normal NK cells but not those from an individual with XLP suggesting that these proteins relay SLAM-associated protein-dependent signals from 2B4. Finally, inactivation of GSK-3 using a specific inhibitor of GSK-3β increased the cytotoxicity and cytokine secretion of both healthy and XLP NK cells. These data indicate that the signaling of 2B4 in NK cells is mediated by GSK-3 and β-catenin, possibly through a signal transduction pathway that involves Vav-1, Rac-1, Raf-1, MEK-2, and Erk1/2 and that this pathway is aberrant in individuals with XLP.

X-linked lymphoproliferative disease (XLP) is a fatal immunological disorder that typically manifests following EBV infection. XLP patients exhibit a number of immune defects including abnormal T, B, and NK lymphocyte function. These defects have been attributed to mutations of Src homology 2 domain-containing gene 1A (SH2D1A), the gene encoding signaling lymphocytic activation molecule-associated protein (SAP), an intracellular adaptor molecule expressed in lymphocytes. We have observed that SAP knockout (SAPKO) mice and humans with XLP have a complete lack of CD1d-restricted NKT cells. As expected, SAPKO mice injected with the NKT cell agonist, alpha-galactosylceramide failed to generate NKT cell IFN-gamma or IL-4. Furthermore, in contrast to wild-type littermates, SAPKO mice coinjected with OVA and alpha-galactosylceramide failed to mount OVA-specific CTL responses. These data suggest that an absence of NKT cells may underlie part of the immune dysregulation seen in SAPKO mice and in XLP patients.

Background. Neisseria meningitidis continues to be an important cause of invasive bacterial disease among children and young adults worldwide. In Canada, N. meningitidis strains that bear serogroups B and C polysaccharide capsules predominate. We report the first documented case of invasive meningococcal disease in an immunocompetent host caused by an acapsular strain of N. meningitidis containing the capsule null locus (cnl). Methods. Analysis of the isolate was performed with use of serological and molecular methods, including multilocus sequence typing and cnl gene identification. Analysis of 16S ribosomal RNA (rRNA) and porA genes was also performed to confirm the identity of the bacterium. Results. The patient was a healthy, immunocompetent 13-year-old child, and N. meningitidis was recovered from a sample of her cerebrospinal fluid before death. The isolate was nontypeable by both conventional antisera and indirect whole-cell enzyme-linked immuosorbent assay methods using antibodies to serogroups B, C, Y, and W135. The isolate was further identified as a cnl strain, serotype 15 (ST-198). N. meningitidis–specific DNA was identified in the isolate and in the pre- and postmortem specimens by 16S rRNA and porA gene analysis. Conclusions. This is the first reported case of fatal meningococcal disease caused by an acapsular cnl strain of N. meningitidis that was isolated from an immunocompetent host. Routine molecular diagnostic methods targeted at the cnl locus failed to detect this organism, indicating a need to determine the incidence of infection with cnl strains among patients with culture-negative invasive disease.

Autoimmune (type 1) diabetes mellitus results from the destruction of insulin-producing pancreatic beta-cells by T lymphocytes. Beta-cell death that is induced by autoreactive CTL in diabetes involves both Fas/Fas ligand (FasL)- and perforin/granzyme-mediated pathways, although their relative contributions during the progression of the disease remain unknown. We demonstrate here that despite the preferential use of the Fas/FasL pathway for cytolysis of beta-cell targets, transgenic beta-cell-specific CTL were able to kill targets via the perforin pathway when triggered by a higher affinity stimulus. In addition, we show that the killing mechanism used by islet-associated CD8(+) T cells from non-obese diabetic mice changed as the mice aged and correspondingly, with the stage of diabetes. These results provide direct evidence for age-related changes in the cytotoxic pathways used by diabetogenic T cells during the progression of autoimmune diabetes.

A proportion of individuals vaccinated with live attenuated Oka varicella-zoster virus (VZV) vaccine subsequently develop attenuated chicken pox and/or herpes zoster. To determine whether postvaccination varicella infections are caused by vaccine or wild-type virus, a simple method for distinguishing the vaccine strain from wild-type virus is required. We have developed a TaqMan real-time PCR assay to detect and differentiate wild-type virus from Oka vaccine strains of VZV. The assay utilized two fluorogenic, minor groove binding probes targeted to a single nucleotide polymorphism in open reading frame 62 that distinguishes the Oka vaccine from wild-type strains. VZV DNA could be genotyped and quantified within minutes of thermocycling completion due to real-time monitoring of PCR product formation and allelic discrimination analysis. The allelic discrimination assay was performed in parallel with two standard PCR-restriction fragment length polymorphism (RFLP) methods on 136 clinical and laboratory VZV strains from Canada, Australia, and Japan. The TaqMan assay exhibited a genotyping accuracy of 100% and, when compared to both PCR-RFLP methods, was 100 times more sensitive. In addition, the method was technically simpler and more rapid. The TaqMan assay also allows for high-throughput genotyping, making it ideal for epidemiologic study of the live attenuated varicella vaccine.

The immune system of the skin has recently been exploited for the development of non-invasive vaccine technologies. However, one of the limitations of current vaccine protocols is the inefficient priming of cytotoxic T lymphocytes (CTL). In this study, we report that the application of either an immunodominant class I MHC restricted ovalbumin peptide or whole ovalbumin protein, to tape-stripped skin together with the co-application of the bacterial enterotoxin cholera toxin (CT) induces antigen-specific CTL. Tape-stripping (TS) was found to enhance the magnitude of antibody responses to co-administered protein and to promote the generation of antigen-specific IgG 2a responses. As well, both cholera toxin and tape-stripping enhanced epidermal dendritic cell (DC) immigration into draining lymph nodes. The adjuvant effect of co-administered cholera toxin and tape-stripping in promoting CTL priming was not dependent on IL-12. Epicutaneous immunization has previously been shown to induce robust antibody responses to administered protein antigen. We now demonstrate the induction of robust and persistent CTL responses to epicutaneously administered protein antigen. Epicutaneous immunization is cheap, simple and effective. These findings suggest the potential use of the skin for the generation of protective immune responses to both viral and tumor challenge.

Chronic active Epstein-Barr virus (CAEBV) infection is an uncommon and severe manifestation of EBV infection that frequently leads to the development of natural killer (NK) or T cell lymphomas. We report here that NK cells derived from a boy with CAEBV showed decreased cytotoxic function and impaired interferon-gamma secretion against a variety of transformed target cell lines. In addition, NK cells from the patient lacked expression of the broadly expressed NK receptor, leukocyte-associated immunoglobulin-like receptor-1 (LAIR-1). These data suggest that CAEBV is associated with low expression of LAIR-1 on NK cells.

Context.—Meningococcal infection has a high public profile because of its dramatic presentation, high fatality rate, and propensity to occur in outbreaks and clusters of cases. Use of a diagnostic polymerase chain reaction (PCR) assay could enhance laboratory confirmation of cases and guide the public health response in North America.Objective.—To assess the performance of a PCR assay for the diagnosis of meningococcal disease after its implementation in a North American setting and to evaluate sensitivity and specificity of the assay for the detection of prevalent bacterial isolates.Design.—Laboratory evaluation of the sensitivity and specificity of a PCR assay for Neisseria meningitidis and observational study of a series of cases comparing molecular diagnosis against the criterion standard of conventional laboratory diagnostic tests.Setting.—A Canadian province with a population of 4 million people.Patients.—Children and adults presenting with suspected meningococcal disease in British Columbia.Main Outcome Measures.—The sensitivity and specificity of the PCR assay when compared against standard laboratory methods.Results.—The PCR assay correctly identified all of 38 Canadian isolates of Neisseria meningitidis and correctly assigned the serogroup to each isolate. None of 57 other gram-positive or gram-negative bacteria or yeasts were detected by the PCR assay. In a clinical evaluation, for diagnosis of meningococcal disease, the PCR assay had a sensitivity and specificity of 91% and 76%, respectively, against conventional methods of diagnosis. Use of the PCR assay increased the laboratory confirmation of clinically suspected cases by 36%. During an outbreak, the PCR assay allowed serogroup determination in 3 of 7 cases, aiding in the public health decision to launch an immunization campaign.Conclusions.—The PCR assay is more sensitive than conventional methods for the diagnosis of meningococcal disease, and enhanced surveillance may help direct the public health response to the changing epidemiology of disease in North America.

CTLs are important mediators of pancreatic β cell destruction in the nonobese diabetic mouse model of type 1 diabetes. Cross-presentation of Ag is one means of priming CTLs. The death of Ag-bearing cells has been implicated in facilitating this mode of priming. The role of β cell death in facilitating the onset of spontaneous autoimmune diabetes is unknown. Here, we used an adoptive transfer system to determine the time course of islet-derived Ag presentation to naive β cell-specific CD8 T cells in nonobese diabetic mice and to test the hypothesis that β cell death enhances the presentation of β cell autoantigen. We have determined that β cell death enhances autoantigen presentation. Priming of diabetogenic CD8 T cells in the pancreatic lymph nodes was negligible before 4 wk, progressively increased until 8 wk of age, and was not influenced by gender. Administration of multiple low doses of the β cell toxin streptozotocin augmented in situ β cell apoptosis and accelerated the onset and magnitude of autoantigen presentation to naive CD8 T cells. Increasing doses of streptozotocin resulted in both increased pancreatic β cell death and significantly enhanced T cell priming. These results indicate that in situ β cell death facilitates autoantigen-specific CD8 T cell priming and can contribute to both the initiation and the ongoing amplification of an autoimmune response.

Background & Aims Type 1 diabetes is caused by an aberrant response against pancreatic β cells. Intestinal K cells are glucose-responsive endocrine cells that might be engineered to secrete insulin. We generated diabetes-prone non-obese diabetic (NOD) mice that express insulin, via a transgene, in K cells. We assessed the effects on immunogenicity and diabetes development. Methods Diabetes incidence and glucose homeostasis were assessed in NOD mice that expressed mouse preproinsulin II from a transgene in K cells and nontransgenic NOD mice (controls); pancreas and duodenum tissues were collected and analyzed by histology. We evaluated T cell responses to insulin, levels of circulating autoantibodies against insulin, and the percentage of circulating antigen-specific T cells. Inflammation of mesenteric and pancreatic lymph node cells was also evaluated. Results The transgenic mice tended to have lower blood levels of glucose than control mice, associated with increased plasma levels of immunoreactive insulin and proinsulin. Fewer transgenic mice developed diabetes than controls. In analyses of pancreas and intestine tissues from the transgenic mice, insulin-producing K cells were not affected by the immune response and the mice had reduced destruction of endogenous β cells. Fewer transgenic mice were positive for insulin autoantibodies compared with controls. Cells isolated from mesenteric lymph nodes of the transgenic mice had significantly lower rates of proliferation and T cells from transgenic mice tended to secrete lower levels of inflammatory cytokines than from controls. At 15 weeks, transgenic mice had fewer peripheral CD8 + T cells specific for NRP-V7 than control mice. Conclusions NOD mice with intestinal K cells engineered to express insulin have reduced blood levels of glucose, are less likely to develop diabetes, and have reduced immunity against pancreatic β cells compared with control NOD mice. This approach might be developed to treat patients with type 1 diabetes.

In GWA studies, CLEC16A has been identified as a risk gene for several major autoimmune diseases, including multiple sclerosis (MS). We show that CLEC16A is increased in MS and functionally links to HLA-II, and uncovered the molecular mechanism of CLEC16A as key regulator of HLA-II antigen presentation. We used the human melanoma cell line MelJuSo and primary moDC as APC models to silence CLEC16A with different siRNA and lentiviral shRNA. CLEC16A knockdown in MelJuSo cells and moDC resulted in cytoplasmic dispersion and strong accumulation of HLA-II+ late endosomes, suggesting impaired formation of multivesicular late endosomal compartments, i.e. MIIC. Indeed, in CLEC16A shRNA transductants, MIIC contained no or a few abnormally enlarged internal vesicles and showed an increased number of HLA-II molecules as compared to scrambled shRNA transductants of MelJuSo cells. CLEC16A associated with Rab7-interacting lysosomal protein (RILP) and the homotypic fusion and protein sorting (HOPS) complex, two members of the dynein motor complex regulating late endosomal trafficking and maturation. In addition, CLEC16A silencing disrupted RILP-mediated recruitment of HLA-II+ late endosomes to perinuclear regions. We reveal direct involvement of CLEC16A in the machinery regulating late endosomal processing of HLA-II. This novel C-type lectin function supports a pathogenic role of CLEC16A in autoimmune disease by promoting HLA-II antigen presentation via the formation of MIIC.

Mutations in the SH2D1A gene, that encodes SLAM-associated protein (SAP), cause X-linked lymphoproliferative disease (XLP), a rare congenital immunodeficiency defined by exquisite sensitivity to Epstein-Barr virus (EBV). The inability of boys with XLP to control EBV infection results in fulminant, often fatal, infectious mononucleosis, massive expansions of EBV-infected B cells and malignant B cell lymphomas. However, the precise mechanism of how SAP loss contributes to susceptibility to EBV remains unclear. Given the unique B cell tropism of EBV and the purported role of SAP in regulating lymphocyte/lymphocyte interactions, we hypothesized that SAP expression within CD8 T cells is critical for T cells to mount responses towards antigen-expressing B cells. Wild type and Sh2d1a-/- CD8 T cells responded strongly when stimulated in vitro with cognate antigen-coated whole splenocytes. However, Sh2d1a-/- CD8 T cells exhibited greatly diminished proliferation and effector functions relative to wild type CD8 T cells when cultured with antigen-coated B cells in vitro or challenged with antigen-expressing B cell lymphoma in vivo. These results demonstrate that SAP is required for the priming of CD8 T cells when B cells act as the primary APC. Together, our findings suggest that the susceptibility of XLP patients to EBV infection may at least in part be a consequence of an inability of their naïve CD8 T cells to differentiate into effectors upon encountering virally-infected B cells.

Epstein-Barr virus (EBV) infection results in rapid loss of CD1d expression from the surface of infected B cells, thus enabling the virus to evade immune recognition by natural killer T (NKT) cells. Using pharmacologic means to boost CD1d expression, potent NKT cell effector functions can be elicited toward EBV-infected B cells, suggesting the promise of novel strategies to target EBV-associated diseases such as some B-cell malignancies.

An assessment was made of the utilization and impact of a diagnostic polymerase chain reaction (PCR) assay for the diagnosis of herpes simplex viruses (HSV) 1 and 2 in cerebrospinal fluid of children who attended a Canadian pediatric referral centre. One hundred and three assays were performed on specimens from 103 patients during the period August 1997 to September 1998. Patient ages ranged from newborn to 16 years. Indications for HSV PCR included seizures with or without fever (56.3%), aseptic meningitis (16.5%), and encephalopathy with or without fever (10.7%). Only 2 of 103 (1.9%) assays were positive, including one each for HSV1 and HSV2. Control specimens that were seeded with virus indicated inhibition for 24.3, 8.8, and 6.8% of assays for HSV1, HSV2, and both HSV1 and HSV2, respectively. The mean turn-around time for HSV PCR was 2.5 days, and 90.3% were completed in less than 5 days. Acyclovir was administered to 78.6% of the patients overall; the results of the HSV PCR impacted on the treatment courses for 36 individuals. Nevertheless, 16.5% of patients continued to receive extended courses of antiviral therapy despite negative HSV PCR assays. Although it is desirable to decrease the frequency of PCR inhibitions and to further decrease the interval to assay completion, HSV PCR does have a significant impact on antiviral use in this setting.Key words: herpes simplex, polymerase chain reaction, central nervous system.

Vigorous HIV-1-specific CD8(+) cytotoxic T lymphocyte (CTL) responses play an important role in the control of HIV-1 replication and the induction of a strong, broadly cross-reactive CTL response remains an important goal of HIV vaccine development. It is known that the display of high levels of class I MHC-viral peptide complexes at the cell surface of target cells is necessary to elicit a strong CTL response. We now report two strategies to enhance the presentation of defined HIV-1 epitope-specific CTL target structures, by incorporating subdominant HIV-1 reverse transcriptase (RT) CTL epitope sequences into the human class I MHC molecule HLA-A2. We show that either incorporation of HIV-1 CTL epitopes into the signal sequence of HLA or tethering of epitopes to the HLA-A2 heavy chain provide simple ways to create effective CTL target structures that can be recognized and lysed by human HLA-A2-restricted RT-specific CD8(+) CTL. Moreover, cells expressing these epitope-containing HLA-A2 constructs stimulated the generation of primary epitope-specific CTL in vitro. These strategies offer new options in the design of plasmid DNA-based vaccines or immunotherapeutics for the induction of CTL responses against subdominant HIV-1 epitopes.

For unknown reasons, autoimmune diseases such as type 1 diabetes develop after prolonged periods of inflammation of mononuclear cells in target tissues. Here we show that progression of pancreatic islet inflammation to overt diabetes in nonobese diabetic (NOD) mice is driven by the 'avidity maturation' of a prevailing, pancreatic beta-cell-specific T-lymphocyte population carrying the CD8 antigen. This T-lymphocyte population recognizes two related peptides (NRP and NRP-A7) in the context of H-2Kd class I molecules of the major histocompatibility complex (MHC). As pre-diabetic NOD mice age, their islet-associated CD8+ T lymphocytes contain increasing numbers of NRP-A7-reactive cells, and these cells bind NRP-A7/H-2Kd tetramers with increased specificity, increased avidity and longer half-lives. Repeated treatment of pre-diabetic NOD mice with soluble NRP-A7 peptide blunts the avidity maturation of the NRP-A7-reactive CD8+ T-cell population by selectively deleting those clonotypes expressing T-cell receptors with the highest affinity and lowest dissociation rates for peptide-MHC binding. This inhibits the local production of T cells that are cytotoxic to beta cells, and halts the progression from severe insulitis to diabetes. We conclude that avidity maturation of pathogenic T-cell populations may be the key event in the progression of benign inflammation to overt disease in autoimmunity.

Rationale . Human herpesvirus 6 (HHV-6) has been demonstrated to be the causative agent in roseola infantum. It has been suggested that HHV-6 may have neurotropic properties and be involved in the pathogenesis of febrile seizures in infants. We describe a case-control study to examine the hypothesis that acute HHV-6 infection occurs more commonly in children with febrile seizures than in controls. Methods . Patients presenting with a first or second febrile seizure between 6 months and 2 years of age were entered in the study. Control patients did not have a seizure but had similar inclusion and exclusion criteria. Specimens were obtained for HHV-6 viral serology and polymerase chain reaction in the acute stage and approximately 2 weeks later. A diagnosis of HHV-6 infection was based on HHV-6-specific IgM and IgG serology and HHV-6 polymerase chain reaction of peripheral blood mononuclear cells and saliva. Results . Eighty-six patients (45 with febrile seizures; 41 controls) were enrolled. The HHV-6 infection status could be determined in only 68 patients (35 with febrile seizures; 33 controls). Acute HHV-6 infection was identified in 15 of 35 febrile seizure patients and in 15 of 33 controls. Evidence of past HHV-6 infection was demonstrated in 13 febrile seizure patients and in 8 controls. Conclusions . The incidence of primary HHV-6 infection is similar in patients with febrile seizures and age-matched controls. HHV-6 does not seem to be a major factor in the pathogenesis of first and second febrile seizures.

FOXP3+ T regulatory cells (Tregs) function to restrain immune responses. Accumulating evidence has shown that Tregs mediate their suppression by migrating to tissues based on their distinct expression of chemokine receptors. Yet how Tregs ensure they are close to their targets is unknown. Using ELISA and intracellular staining we discovered that both human and mouse Tregs produce CCL3 and CCL4, ligands for CCR5. Since chemokines recruit immune cells and the broad suppressive activities of Tregs require intimate cell proximity, we hypothesized that the secretion of the pro-inflammatory chemokines may bring immune cells closer to Tregs to be suppressed. To determine whether Tregs can recruit CD4+ and CD8+ cells via a CCR5-dependent mechanism, we performed migration assays and showed CCL3- and CCL4- containing-supernatants from Tregs attracted both subsets of T cells as well Tregs. Additionally, CCR5-/- T cells had a significantly reduced capacity to migrate towards Tregs in vitro and in vivo, supporting that chemokine signalling through CCR5 is critical. Furthermore, decreased proportion of FOXP3+CCL3+ Tregs was observed in patients with type 1 diabetes compared to healthy controls, implying that the altered chemokine secretion could contribute to the inadequate Treg function. These results suggest that active recruitment of their targets of suppression may be a novel mechanism of action by Tregs and that this pathway could be a potential therapeutic target in autoimmunity.

Type 1 diabetes (T1D) results from the destruction of beta cells by autoreactive lymphocytes. Regulatory T cells (Tregs) maintain self-tolerance in part by suppressing the effector functions of self-reactive lymphocytes. Tregs require the cytokine interleukin-2 (IL-2) for survival and maintenance of their suppressive function. IL-2 binds to the high-affinity IL-2 receptor (IL-2R), leading to phosphorylation of signal transducer and activator of transcription 5 (STAT5) and downstream transcription of effector proteins.The IL-2 receptor gene has single nucleotide polymorphisms (SNPs), which are associated with T1D incidence. We hypothesized that T1D subjects with SNPs in the IL-2R gene possess Tregs that respond aberrantly to IL-2 and do not optimally induce signaling in the STAT5 pathway. PBMC from T1D subjects with a homozygous susceptible (GG), heterozygous (AG) and homozygous wild-type (AA) genotype for a SNP located in the rs3118470 locus of the IL-2R gene were stimulated with IL-2. Our results indicate that Tregs from individuals with the homozygous susceptible GG genotype have reduced levels of pSTAT5 compared to those with the AA genotype (p=0.0133). This provides evidence that Tregs from T1D subjects with SNPs in the rs3118470 locus of the IL-2R gene have diminished STAT5 phosphorylation in response to IL-2. This is a potential mechanism of defective Treg function in a genetically identifiable subset of children with T1D.

Individuals with X-linked lymphoproliferative disease (XLP) lack invariant natural killer T (iNKT) cells and are uniquely susceptible to Epstein-Barr virus (EBV). To determine whether iNKT cells recognize or regulate EBV replication, human B cells were infected with GFP+ EBV 95.8 in the presence or absence of iNKT cells. We observed that iNKT cells significantly reduced early EBV titres and GFP+ B cell expansion but that within 72 hours of infection, B cells transformed into lymphoblastoid cell lines (LCL) by EBV had downregulated the iNKT antigen receptor CD1d, completely abrogating iNKT recognition of the lipid agonist α-galactosylceramide (αGalCer). To determine whether ectopic CD1d expression could restore iNKT recognition, LCL were treated with a synthetic retinoic acid receptor-α agonist AM580 known to modulate CD1d expression by regulating the nuclear protein lymphoid enhancer-binding factor-1 (LEF-1). AM580 treatment significantly reduced LEF-1 at the CD1d promoter, induced surface CD1d expression and enabled iNKT recognition of LCL loaded with αGalCer. Unexpectedly, AM580-treated LCL also activated iNKT function even in the absence of αGalCer suggesting that EBV infection and transformation triggers endogenous iNKT antigen expression. These observations indicate that iNKT cells may be important for the early recognition and control of EBV-infected B cells prior to CD1d downregulation and the loss of CD1d may allow EBV to circumvent iNKT-mediated immunosurveillance.

s / Can J Diabetes 36 (2012) S24eS76 S76 injection into the pancreatic duct of C57Bl/6 mice, resulting in beta beta cell specific expression throughout the pancreas. When XIAPexpressing mouse islets were isolated from C57 Bl/6 donors and transplanted into streptozotocin-diabetic, MHC-mismatched (Balb/ c) mice, all recipients were protected from allograft rejection and return of hyperglycemia for more than 125 days. Histological analysis of the islet graft confirmed numerous insulin-positive cells within XIAP-expressing islets and a progressive lost of immune infiltration cells. Diminished alloantibodies and non-proliferation of splenocytes after exposure to alloantigens suggested that tolerance was induced in the recipients. These findings indicate that dsAAV8-mediated expression of XIAP in islets may induce tolerance to islet allograft recipients, thereby preventing recurrence of diabetes. Manipulation of islets for long-term expression of XIAP may be a novel therapeutic strategy for diabetes.

Mutations in SAP (SLAM-associated protein) underlie the majority of cases of X-linked lymphoproliferative disease (XLP), a rare congenital disorder that often leads to fatal complications upon infection with Epstein-Barr virus. The small SH2-containing adaptor SAP transmits signaling via SLAM (signaling lymphocytic activation molecule) family receptors and has been shown to be critical for development and function of multiple immune cell types. Here, we have investigated the role of SLAM and SAP signaling in regulating the differentiation of naïve CD4 T cells into IL-17 secreting effectors (TH17 cells), a pro-inflammatory lineage implicated in host defense as well as autoimmune diseases. T cell receptor activation along with co-stimulating SLAM antibodies was found to augment TH17 cell differentiation in wild type but not SAP-deficient splenic T cells under IL-17 polarizing conditions. Furthermore, SAP-/- mice were protected from experimental autoimmune encephalomyelitis (EAE), exhibiting greatly decreased numbers of CNS-infiltrating TH17 cells and dramatically reduced disease severity. Collectively, these results suggest that SLAM-SAP interactions promote the differentiation of IL-17 secreting effector CD4 T cells both in vitro and in vivo.

CD4+CD25+ T regulatory (Treg) cells prevent spontaneous development of autoimmune diabetes and may delay islet allograft rejection. Tumour cells attract Treg cells to foster immune privilege by producing the chemokine CCL22, which promotes trafficking of Treg cells to the tumour. Therefore, manipulating Treg migration with CCL22 may provide a means of preventing islet transplant rejection in autoimmune diabetes. To drive islet-specific expression of CCL22 we created an adenovirus (Ad-CCL22) in which a mouse CCL22 cDNA is expressed downstream of the CMV promoter. Isolated islets transduced with Ad-CCL22 (10 MOI) produced and secreted high levels of CCL22 in vitro whereas CCL22 production by non-transduced islets was undetectable. To determine whether CCL22 expression prevents islet allograft rejection, donor Balb/c islets were isolated and transduced overnight with Ad-CCL22 (n = 6) or Ad-lacZ (n = 5). Islets (300 per recipient) were then transplanted into the left renal subcapsular space of age-matched female C57/BL6 diabetic recipients. By 5 weeks post-transplant, only 1 of 7 CCL22-expressing islet grafts had been rejected whereas 4 of 5 Ad-LacZ-transduced grafts were rejected. Induced expression of CCL22 by transplanted islets thus delays islet allograft rejection. Manipulation of Tregs cells by CCL-22 in transplanted islets may be a novel therapeutic strategy for diabetes.