Exploring JC polyomavirus sequences and human gene expression in brain tissue of patients with progressive multifocal leukoencephalopathy.

Progressive multifocal leukoencephalopathy (PML) is a rare neurological condition associated with reactivation of dormant JC polyomavirus (JCPyV). In this study, we characterized gene expression and JCPyV rearrangements in PML brain tissue. Infection of white matter astrocytes and oligodendrocytes as well as occasional brain cortex neurons was shown. PML brain harbored exclusively rearranged JCPyV variants. Viral transcripts covered the whole genome on both strands. Strong differential expression of human genes associated with neuroinflammation, blood-brain-barrier permeability and neurodegenerative diseases was shown. Pathway analysis revealed wide immune activation in PML brain. The study provides novel insights into the pathogenesis of PML.

Increased type 1 inflammation in gynecologic cervicovaginal samples in patients with APS-1.

BACKGROUND: Inborn errors of immunity offer important insights into mucosal immunity. In autoimmune polyendocrine syndrome type-1 (APS-1), chronic mucocutaneous candidiasis has been ascribed to neutralizing IL-17 autoantibodies. Recent evidence implicates excessive T-cell IFN-γ secretion and ensuing epithelial barrier disruption in predisposition to candidiasis, but these results remain to be replicated. Whether IL-17 paucity, increased type I inflammation, or their combination underlies susceptibility to chronic mucocutaneus candidiasis in APS-1 is debated. OBJECTIVE: Our aim was to characterize the immunologic features in the cervicovaginal mucosa of females with APS-1. METHODS: Vaginal fluid was collected with a flocked swab from 17 females with APS-1 and 18 controls, and cytokine composition was analyzed using Luminex (Luminex Corporation, Austin, Tex). Cervical cell samples were obtained with a cervix brush from 6 patients and 6 healthy controls and subjected to transcriptome analysis. RESULTS: The vaginal fluid samples from patients with APS-1 had IFN-γ concentrations comparable to those of the controls (2.6 vs 2.4 pg/mL) but high concentrations of the TH1 chemokines CXCL9 and CXCL10 (1094 vs 110 pg/mL [P < .001] and 4033 vs 273 pg/mL [P = .001], respectively), whereas the IL-17 levels in the samples from the 2 groups were comparable (28 vs 8.8 pg/mL). RNA sequencing of the cervical cells revealed upregulation of pathways related to mucosal inflammation and cell death in the patients with APS-1. CONCLUSION: Excessive TH1 cell response appears to underlie disruption of the mucosal immune responses in the genital tract of patients with APS-1 and may contribute to susceptibility to candidiasis in the genital tract as well.

Dysregulated germinal center reaction with expanded T follicular helper cells in autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy lymph nodes.

BACKGROUND: Autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED, also called APS-1) is an inborn error of immunity with clear signs of B-cell autoimmunity such as neutralizing anti-IFN antibodies. In APECED, mutations in the AIRE gene impair thymic negative selection of T cells. The resulting T-cell alterations may then cause dysregulation of B-cell responses. However, no analysis of interactions of T and B cells in the germinal centers (GCs) in patients' secondary lymphatic tissues has been reported. OBJECTIVE: This study examined the relationship between B cells and follicular T helper cells (TfH) in peripheral blood and lymph node (LN) GCs in patients with APECED. METHODS: Immunophenotyping of peripheral blood B cells and TfH was performed for 24 patients with APECED. Highly multiplexed fluorescent immunohistochemical staining was performed on 7 LN biopsy samples from the patients to study spatial interactions of lymphocytes in the GCs at the single-cell level. RESULTS: The patients' peripheral B-cell phenotype revealed skewing toward a mature B-cell phenotype with marked loss of transitional and naive B cells. The frequency of circulating TfH cells was diminished in the patients, while in the LNs the TfH population was expanded. In LNs the overall frequency of Treg cells and interactions of Treg cells with nonfollicular T cells were reduced, suggesting that aberrant Treg cell function might fail to restrain TfH differentiation. CONCLUSIONS: GC reactions are disrupted in APECED as a result of defective T-cell control.

Peripheral differentiation patterns of human T cells.

Long-term T-cell memory is dependent on the maintenance of memory T cells in the lymphoid tissues, and at the surface interfaces that provide entry routes for pathogens. However, much of the current information on human T-cell memory is based on analyzing circulating T cells. Here, we have studied the distribution and age-related changes of memory T-cell subsets in samples from blood, mesenteric LNs, spleen, and ileum, obtained from donors ranging in age from 5 days to 67 years of age. Our data show that the main reservoir of polyclonal naive cells is found in the LNs, and the resting memory subsets capable of self-renewal are also prominent there. In contrast, nondividing but functionally active memory subsets dominate the spleen, and especially the ileum. In general, the replacement of naive cells with memory subsets continues throughout our period of observation, with no apparent plateau. In conclusion, the analysis of lymphoid and nonlymphoid tissues reveals a dynamic pattern of changes distinct to each tissue, and with substantial differences between CD4+ and CD8+ compartments.

Loss-of-function mutation in IKZF2 leads to immunodeficiency with dysregulated germinal center reactions and reduction of MAIT cells.

The Ikaros family transcription factors regulate lymphocyte development. Loss-of-function variants in IKZF1 cause primary immunodeficiency, but Ikaros family members IKZF2 and IKZF3 have not yet been associated with immunodeficiency. Here, we describe a pedigree with a heterozygous truncating variant in IKZF2, encoding the transcriptional activator and repressor Helios, which is highly expressed in regulatory T cells and effector T cells, particularly of the CD8+ T cell lineage. Protein-protein interaction analysis revealed that the variant abolished heterodimerization of Helios with Ikaros and Aiolos and also prevented Helios binding to members of the Mi-2/NuRD chromatin remodeling complex. Patients carrying the IKZF2 variant presented with a combined immunodeficiency phenotype characterized by recurrent upper respiratory infections, thrush and mucosal ulcers, and chronic lymphadenopathy. With extensive immunophenotyping, functional assays, and transcriptional analysis, we show that reduced Helios expression was associated with chronic T cell activation and increased production of proinflammatory cytokines both in effector and regulatory T cells. Lymph node histology from patients indicated dysregulated germinal center reactions. Moreover, affected individuals displayed a profound reduction in circulating MAIT cell numbers. In summary, we show that this previously undescribed loss-of-function variant in Helios leads to an immunodeficiency with signs of immune overactivation.

Patients with autoimmune polyendocrine syndrome type 1 have an increased susceptibility to severe herpesvirus infections.

Almost all patients with autoimmune polyendocrine syndrome type 1 (APS-1) have neutralizing antibodies against type 1 interferons (IFN), important mediators of antiviral defense. Recently, neutralizing anti-IFN antibodies were shown to be a risk factor of severe COVID-19. Here we show in a cohort of 44 patients with APS-1 that higher titers of neutralizing anti-IFNα4 antibodies are associated with a higher and earlier incidence of VZV reactivation (herpes zoster). The patients also present with uncommonly severe clinical sequelae of herpetic infections. APS-1 patients had decreased humoral immune responses to varicella zoster virus, but cellular responses were comparable to healthy controls. These results suggest that blocking the type I interferon pathway in patients with APS-1 patients leads to a clinically significant immune deficiency, and susceptibility to herpesviruses should be taken into account when treating patients with APS-1.

Fecal Bacteria Implicated in Biofilm Production Are Enriched and Associate to Gastrointestinal Symptoms in Patients With APECED - A Pilot Study.

Backgrounds and Aims: APECED is a rare autoimmune disease caused by mutations in the Autoimmune Regulator gene. A significant proportion of patients also have gastrointestinal symptoms, including malabsorption, chronic diarrhea, and obstipation. The pathological background of the gastrointestinal symptoms remains incompletely understood and involves multiple factors, with autoimmunity being the most common underlying cause. Patients with APECED have increased immune responses against gut commensals. Our objective was to evaluate whether the intestinal microbiota composition, predicted functions or fungal abundance differ between Finnish patients with APECED and healthy controls, and whether these associate to the patients' clinical phenotype and gastrointestinal symptoms. Methods: DNA was isolated from fecal samples from 15 patients with APECED (median age 46.4 years) together with 15 samples from body mass index matched healthy controls. DNA samples were subjected to analysis of the gut microbiota using 16S rRNA gene amplicon sequencing, imputed metagenomics using the PICRUSt2 algorithm, and quantitative PCR for fungi. Extensive correlations of the microbiota with patient characteristics were determined. Results: Analysis of gut microbiota indicated that both alpha- and beta-diversity were altered in patients with APECED compared to healthy controls. The fraction of Faecalibacterium was reduced in patients with APECED while that of Atopobium spp. and several gram-negative genera previously implicated in biofilm formation, e.g. Veillonella, Prevotella, Megasphaera and Heamophilus, were increased in parallel to lipopolysaccharide (LPS) synthesis in imputed metagenomics. The differences in gut microbiota were linked to patient characteristics, especially the presence of anti-Saccharomyces cerevisiae antibodies (ASCA) and severity of gastrointestinal symptoms. Conclusions: Gut microbiota of patients with APECED is altered and enriched with predominantly gram-negative bacterial taxa that may promote biofilm formation and lead to increased exposure to LPS in the patients. The most pronounced alterations in the microbiota were associated with more severe gastrointestinal symptoms.

An outbreak caused by the SARS-CoV-2 Delta variant (B.1.617.2) in a secondary care hospital in Finland, May 2021.

An outbreak caused by the SARS-CoV-2 Delta variant (B.1.617.2) spread from one inpatient in a secondary care hospital to three primary care facilities, resulting in 58 infections including 18 deaths in patients and 45 infections in healthcare workers (HCW). Only one of the deceased cases was fully vaccinated. Transmission occurred despite the use of personal protective equipment by the HCW, as advised in national guidelines, and a high two-dose COVID-19 vaccination coverage among permanent staff members in the COVID-19 cohort ward.

Heterologous boosting of nonrelated toxoid immunity during acute Puumala hantavirus infection.

Persistence of immune memory in humans is a crucial yet poorly understood aspect of immunology. Here we have studied the effect of Puumala hantavirus infection on unrelated, pre-existing immune memory by studying T cell- and antibody responses against toxoid vaccine antigens of diphtheria, tetanus and pertussis in a cohort of 45 patients. We found that tetanus- and pertussis -specific IgG concentrations elevate during acute Puumala virus infection. Increase in vaccine IgG was associated with proliferation of heterologous T cells. Interestingly, increases in tetanus-specific IgG persisted a year after the infection while pertussis-specific IgG declined rapidly; a difference in IgG kinetics resembling the difference seen after vaccination against tetanus and pertussis. These results suggest that persistence of immune memory is facilitated by heterologous boosting of old memory during memory formation against newly encountered antigens. They also show that different toxoid antigens may be treated differently. Our study gives new insight into how immune memory formation may alter pre-existing immune memory, and also shows that heterologous immunity may have an impact on vaccination outcomes.

Indoleamine 2,3-dioxygenase activity is associated with regulatory T cell response in acute Puumala hantavirus infection.

High indoleamine 2,3-dioxygenase (IDO) activity is associated with clinically severe acute infection caused by Puumala hantavirus. The immunoregulatory effects of IDO can be mediated either through metabolic control of effector T cells, caused by depletion of the essential amino acid tryptophan, or intercellular signaling and activation of regulatory T cell responses. Here, we have studied 24 patients with acute Puumala hantavirus infection to distinguish between these possibilities. Maximum IDO activity showed a significant positive correlation with FOXP3 expression levels in regulatory T cells, a quantitative surrogate marker for suppressive capability. In contrast, IDO activity did not correlate with the frequency of CD8+ effector cells in cell cycle. The data suggest that in Puumala infection, the mechanism responsible for the suppressive effect of IDO is not metabolic control of effector cells but rather the signaling mediated by tryptophan breakdown products, such as kynurenine.

Anticommensal Responses Are Associated with Regulatory T Cell Defect in Autoimmune Polyendocrinopathy-Candidiasis-Ectodermal Dystrophy Patients.

Autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED) is a monogenic autoimmune disease caused by mutations in the AIRE gene. Although mainly an endocrine disease, a substantial fraction of patients have gastrointestinal manifestations. In this study, we have examined the role of anticommensal responses and their regulation. APECED patients had increased levels of Abs against Saccharomyces cerevisiae (p < 0.0001) and against several species of commensal gut bacteria, but not against species predominantly associated with other locations. The anticommensal Ab levels did not correlate with gastrointestinal autoantibodies, neutralizing anti-IL-17 or -IL-22 Abs, or gastrointestinal symptoms, although scarcity of the available clinical data suggests that further study is required. However, the anti-S. cerevisiae Ab levels showed a significant inverse correlation with FOXP3 expression levels in regulatory T cells (Treg), previously shown to be dysfunctional in APECED. The correlation was strongest in the activated CD45RO(+) population (ρ = -0.706; p < 0.01). APECED patients also had decreased numbers of FOXP3(+) cells in gut biopsies. These results show that APECED patients develop early and sustained responses to gut microbial Ags in a pattern reminiscent of Crohn's disease. This abnormal immune recognition of gut commensals is linked to a systemic Treg defect, which is also reflected as a local decrease of gut-associated Treg. To our knowledge, these data are the first to show dysregulated responses to non-self commensal Ags in APECED and indicate that AIRE contributes to the regulation of gut homeostasis, at least indirectly. The data also raise the possibility of persistent microbial stimulation as a contributing factor in the pathogenesis of APECED.

Regulatory T cell response correlates with the severity of human hantavirus infection.

OBJECTIVES: Hantaviruses are an important group of emerging zoonotic pathogens, with significant mortality rates. Immunopathology is thought to be important in hantaviral disease, but the balance between protective and harmful responses is unknown. We studied Puumala hantavirus (PUUV) infection, which causes hemorrhagic fever with renal syndrome (HFRS) with a generally mild but highly variable clinical course. METHODS: Clinical data and blood samples were collected from 24 patients with acute PUUV infection, and analyzed by flow cytometry and quantitative PCR. RESULTS: The patients had a significantly increased frequency of CD4(+) and CD8(+) cells expressing the cell cycle marker Ki-67, but the magnitude of the effector T cell response did not correlate with disease severity. The frequency of FOXP3(+) regulatory T (Treg) cells expressing Ki-67 was also increased, and likewise did not correlate with disease outcome. In contrast, the level of FOXP3 expression, a surrogate of the suppressive phenotype, had a strong positive correlation with disease severity. This correlation was also found in samples taken 6-12 months after the HFRS. CONCLUSIONS: The best predictor of a severe disease course in HFRS was the FOXP3(+) Treg cell response, suggesting that the role of Treg cells in acute human hantaviral infections may be deleterious.

Impaired intestinal tolerance in the absence of a functional complement system.

BACKGROUND: Cells of the innate immune system regulate both adaptive immune responses and the maintenance of tolerance, especially in the gut. However, relatively little is known about the effects of complement on lymphocyte homeostasis. OBJECTIVE: This study explored complement C3 deficiency in mice and human subjects for its effect on intestinal tolerance. METHODS: C3-deficient mice and control C57BL/6 mice were fed ovalbumin (OVA) by means of gavage, and subsequent response to immunization with OVA in Freund's adjuvant was monitored. Serum antibodies against commensal microbes were measured, and the activation status of peripheral blood lymphocytes bearing mucosal homing markers was determined from 2 rare cases of C3-deficient patients. RESULTS: We show in C3-deficient mice and human patients that intestinal tolerance fails in the absence of functional complement. In contrast to wild-type control animals, in which oral tolerance was induced, intragastric administration of OVA did not result in a significantly decreased response to subsequent subcutaneous OVA challenge in C3-deficient mice. In the jejunum of C3-deficient mice the cytokine ratio between IL-10 and IFN-γ or IL-17 levels was decreased, indicating a shift in favor of proinflammatory cytokines. In 2 C3-deficient children the frequency of gut-homing T cells expressing activation markers was increased, and the patients had increased serum IgG levels against gut commensal microbes. The data also suggest that the impaired oral tolerance was at least partly caused by the absence of signaling through C3-binding complement regulators in T cells. CONCLUSIONS: Taken together, our results identify complement as an important and nonredundant regulator of intestinal tolerance.