Immune mechanisms and the impact of the disrupted lung microbiome in chronic bacterial lung infection and bronchiectasis.

Recent studies analysing immunogenetics and immune mechanisms controlling susceptibility to chronic bacterial infection in bronchiectasis implicate dysregulated immunity in conjunction with chronic bacterial infection. Bronchiectasis is a structural pathological end-point with many causes and disease associations. In about half of cases it is termed idiopathic, because it is of unknown aetiology. Bronchiectasis is proposed to result from a 'vicious cycle' of chronic bacterial infection and dysregulated inflammation. Paradoxically, both immune deficiency and excess immunity, either in the form of autoimmunity or excessive inflammatory activation, can predispose to disease. It appears to be a part of the spectrum of inflammatory, autoimmune and atopic conditions that have increased in prevalence through the 20th century, attributed variously to the hygiene hypothesis or the 'missing microbiota'. Immunogenetic studies showing a strong association with human leucocyte antigen (HLA)-Cw*03 and HLA-C group 1 homozygosity and combinational analysis of HLA-C and killer immunoglobulin-like receptors (KIR) genes suggests a shift towards activation of natural killer (NK) cells leading to lung damage. The association with HLA-DR1, DQ5 implicates a role for CD4 T cells, possibly operating through influence on susceptibility to specific pathogens. We hypothesize that disruption of the lung microbial ecosystem, by infection, inflammation and/or antibiotic therapy, creates a disturbed, simplified, microbial community ('disrupted microbiota') with downstream consequences for immune function. These events, acting with excessive NK cell activation, create a highly inflammatory lung environment that, in turn, permits the further establishment and maintenance of chronic infection dominated by microbial pathogens. This review discusses the implication of these concepts for the development of therapeutic interventions.

Effects of temporarily suspending low-dose methotrexate treatment for 2 weeks after SARS-CoV-2 vaccine booster on vaccine response in immunosuppressed adults with inflammatory conditions: protocol for a multicentre randomised controlled trial and nested mechanistic substudy (Vaccine Response On/Off Methotrexate (VROOM) study).

INTRODUCTION: It is unknown if a temporary break in long-term immune-suppressive treatment after vaccination against COVID-19 improves vaccine response. The objective of this study was to evaluate if a 2-week interruption in low-dose weekly methotrexate treatment after SARS-CoV-2 vaccine boosters enhances the immune response compared with continuing treatment in adults with autoimmune inflammatory conditions. METHODS AND ANALYSIS: An open-label, pragmatic, prospective, parallel group, randomised controlled superiority trial with internal feasibility assessment and nested mechanistic substudy will be conducted in rheumatology and dermatology clinics in approximately 25 UK hospitals. The sample size is 560, randomised 1:1 to intervention and usual care arms. The main outcome measure is anti-spike receptor-binding domain (RBD) antibody level, collected at prebooster (baseline), 4 weeks (primary outcome) and 12 weeks (secondary outcome) post booster vaccination. Other secondary outcome measures are patient global assessments of disease activity, disease flares and their treatment, EuroQol 5- dimention 5-level (EQ-5D-5L), self-reported adherence with advice to interrupt or continue methotrexate, neutralising antibody titre against SARS-CoV-2 (mechanistic substudy) and oral methotrexate biochemical adherence (mechanistic substudy). Analysis of B-cell memory and T-cell responses at baseline and weeks 4 and 12 will be investigated subject to obtaining additional funding. The principal analysis will be performed on the groups as randomised (ie, intention to treat). The difference between the study arms in anti-spike RBD antibody level will be estimated using mixed effects model, allowing for repeated measures clustered within participants. The models will be adjusted for randomisation factors and prior SARS-CoV-2 infection status. ETHICS AND DISSEMINATION: This study was approved by the Leeds West Research Ethics Committee and Health Research Authority (REC reference: 21/HRA/3483, IRAS 303827). Participants will be required to give written informed consent before taking part in the trial. Dissemination will be via peer review publications, newsletters and conferences. Results will be communicated to policymakers. TRIAL REGISTRATION NUMBER: ISRCTN11442263.

Regulation of immunity in bronchiectasis.

Bronchiectasis is a chronic, progressive lung disease where there is irreversible, abnormal dilatation of one or more bronchi, with chronic airway inflammation, associated chronic cough and sputum production, recurrent chest infections, and airflow obstruction. As such it is essentially a pathological endpoint with several underlying causes. Allergic bronchopulmonary aspergillosis (ABPA) is an important cause of bronchiectasis and aspergillus related lung disease sometimes complicates established bronchiectasis. A diagnosis of bronchiectasis is made clinically and confirmed with high-resolution computed tomography (HRCT) of the thorax. Progressive lung damage results from a 'vicious cycle' of recurrent bacterial infection and a poorly regulated inflammatory response. There appear to be two stages to the disease process: the initial insult that sets off the disease and then the ongoing, inflammatory process encompassing recurrent infection and progressive lung damage. Abnormalities in innate and adaptive immunity may predispose to bronchiectasis at both stages. Recent immunogenetic evidence suggests that there may be a link between the level of natural killer (NK) cell activation and disease susceptibility, implicating a predisposing role for innate immune mechanisms. A role for adaptive immune mechanisms is suggested by the genetic association of HLA-DR1, DQ5 with increased susceptibility to idiopathic bronchiectasis.

Human leucocyte antigen class II association in idiopathic bronchiectasis, a disease of chronic lung infection, implicates a role for adaptive immunity.

The aetiology of idiopathic bronchiectasis, a lung disease where chronic inflammation and bacterial infection leads to progressive lung damage, is unknown. A possible role for natural killer cells has been highlighted previously. However, a role for adaptive immunity is suggested by the presence of CD4 and CD8 T cells in diseased lung tissue. Evidence of a human leucocyte antigen (HLA) class II disease association would further implicate a role for adaptive immunity. To establish if there is any HLA association, we analysed HLA-A, HLA-B, HLA-DQA1, HLA-DQB1 and HLA-DRB1 alleles in patients with idiopathic bronchiectasis and controls. Genomic DNA from 92 adults with idiopathic bronchiectasis and 101 healthy controls was analysed by polymerase chain reaction with sequence-specific primers. We found an increase in the prevalence of HLA-DRB1*01 DQA1*01/DQB1*05 genes in idiopathic bronchiectasis; that is, the HLA-DR1, DQ5 haplotype (odds ratio 2.19, 95% confidence interval 1.15-4.16, P = 0.0152) compared with control subjects. The association with HLA-DR1, DQ5 implicates a role for CD4 T cells restricted by these molecules in susceptibility to the progressive lung damage seen in this disease. This may operate either through influencing susceptibility to specific pathogens or to self-reactivity and requires further investigation.

T cell immunity to Zika virus targets immunodominant epitopes that show cross-reactivity with other Flaviviruses.

Zika virus (ZIKV) Infection has several outcomes from asymptomatic exposure to rash, conjunctivitis, Guillain-Barré syndrome or congenital Zika syndrome. Analysis of ZIKV immunity is confounded by the fact that several related Flaviviruses infect humans, including Dengue virus 1-4, West Nile virus and Yellow Fever virus. HLA class II restricted T cell cross-reactivity between ZIKV and other Flaviviruses infection(s) or vaccination may contribute to protection or to enhanced immunopathology. We mapped immunodominant, HLA class II restricted, CD4 epitopes from ZIKV Envelope (Env), and Non-structural (NS) NS1, NS3 and NS5 antigens in HLA class II transgenic mice. In several cases, ZIKV primed CD4 cells responded to homologous sequences from other viruses, including DENV1-4, WNV or YFV. However, cross-reactive responses could confer immune deviation - the response to the Env DENV4 p1 epitope in HLA-DR1 resulted in IL-17A immunity, often associated with exacerbated immunopathogenesis. This conservation of recognition across Flaviviruses, may encompass protective and/or pathogenic components and poses challenges to characterization of ZIKV protective immunity.

An audit of the BMJ's correspondence columns.

OBJECTIVE: To see whether some sections of the BMJ attract more comment than others, whether letters submitted in response to different sections of the journal are rejected at different rates, and whether the balance between letters that agree and disagree with articles in the published correspondence reflects that in submitted letters. DESIGN: Retrospective audit of letters submitted for publication in the correspondence columns of the BMJ in response to articles published between 1 January and 21 May 1989. SUBJECTS: A total of 1319 letters received by the journal, 974 submitted in response to the 1501 published articles and a further 345 raising new issues. MAIN OUTCOME MEASURES: The total numbers of letters submitted in response to the four main sections of the journal--editorials, news, papers, and middles--and the numbers published. Submitted and published letters were analysed according to whether they agreed or disagreed with articles. RESULTS: The overall rejection rate was 63% (831/1319), but among letters relating to articles it was 56% (543/974). Editorials and middles attracted proportionately more letters than papers, but letters relating to papers had a lower rejection rate (43% v 57% for editorials and 43% v 66% for middles). For all sections more letters disagreed than agreed, but a higher proportion of letters in response to editorials and middles disagreed than those submitted in response to papers (64% and 72% v 53%). Among the published letters, however, broadly equal numbers of letters agreed and disagreed with articles, irrespective of section. CONCLUSION: Those sections of the journal that aim at stimulating debate succeeded in attracting the most comment. The relative importance of original scientific research papers was reflected by the priority given to letters submitted in response to papers, and the final correspondence column was a balanced platform of debate despite an unequal submitted response in terms of letters that agreed and disagreed with different sections of the journal.

Diverse approaches to analysing the history of human and pathogen evolution: how to tell the story of the past 70 000 years.

The meeting 'Human evolution, migration and history revealed by genetics, immunity and infection', along with the follow-on satellite meeting at the Kavli Centre over the subsequent two days, brought together diverse talents. The aim was to see if new insights could be gained by bringing together those who have interests in the past 50-100 000 years of human history, overlaying the perspectives of palaeogeneticists, anthropologists, human geneticists, pathogen geneticists, immunologists, disease modellers, linguists, immunogeneticists, historians and archaeologists. It rapidly became clear that while all may agree on the broad brush-strokes including 'out-of-Africa' and the general approximations of timelines, diverse approaches may often suggest somewhat different ways of telling the story.

Natural killer cells, killer immunoglobulin-like receptors and human leucocyte antigen class I in disease.

Natural killer cells constitute a potent, rapid part of the innate immune response to infection or transformation, and also generate a link to priming of adaptive immunity. Their function can encompass direct cytotoxicity as well as the release of cytokines and chemokines. In humans, a major component of natural killer (NK) cell target recognition depends mainly on the surveillance of human leucocyte antigen (HLA) class I molecules by killer immunoglobulin-like receptors (KIR). Different KIR can transmit inhibitory or activatory signals to the cell, and effector function is considered to result from the balance of these contributing signals. The regulation of NK cell responses depends on a number of variables: KIR genotype, HLA genotype, heterozygosity versus homozygosity for these, whether there is cognate recognition between the HLA and KIR products carried by an individual, clonal variation between individual NK cells in KIR expression, and the specific modulation of HLA expression by infection, transformation or peptide binding. Different HLA/KIR genotypes can impart different thresholds of activation to the NK cell repertoire and such genotypic variation has been found to confer altered risk in a number of diseases including human immunodeficiency virus (HIV) susceptibility and progression, hepatitis C virus clearance, idiopathic bronchiectasis, autoimmunity and cancer.

Effect of tolerance induction to immunodominant T-cell epitopes of Sendai virus on gene expression following repeat administration to lung.

Sendai virus (SeV) is able to transfect airway epithelial cells efficiently in vivo. However, as with other viral vectors, repeated administration leads to reduced gene expression. We have investigated the impact of inducing immunological tolerance to immunodominant T-cell epitopes on gene expression following repeated administration. Immunodominant CD4 and CD8 T-cell peptide epitopes of SeV were administered to C57BL/6 mice intranasally 10 days before the first virus administration with transmission-incompetent F-protein-deleted DeltaF/SeV-GFP. At 21 days after the first virus administration, mice were again transfected with DeltaF/SeV. To avoid interference of anti-GFP antibodies, the second transfection was carried out with DeltaF/SeV-lacZ. At 2 days after the final transfection lung beta-galactosidase expression, T-cell proliferation and antibody responses were measured. A state of 'split tolerance' was achieved with reduced T-cell proliferation, but no impact on antiviral antibody production. There was no enhancement of expression on repeat administration; instead, T-cell tolerance was, paradoxically, associated with a more profound extinction of viral expression. Multiple immune mechanisms operate to eradicate viruses from the lung, and these findings indicate that impeding the adaptive T-cell response to the immunodominant viral epitope is not sufficient to prevent the process.

IFN gamma and CXCR-1 gene polymorphisms in idiopathic bronchiectasis.

Idiopathic bronchiectasis is a disease of chronic, bacterial lung infection, unresolving inflammation and progressive lung damage. Bronchiectasis can be associated with autoimmune diseases including ulcerative colitis. Defects of both innate and adaptive immunity have been proposed. The airway inflammation is characterized by interleukin-8 (IL-8) expression and infiltration by neutrophils and T cells. Here we investigated two candidate gene polymorphisms that may contribute to disease susceptibility: a CXCR-1 (+2607 G/C) gene polymorphism that is implicated in IL-8 binding and neutrophil trafficking as well as the interferon-gamma (IFNgamma) (+874 T/A) polymorphism which is linked to levels of IFNgamma production. These polymorphisms were distributed similarly in the idiopathic bronchiectasis group and controls, suggesting that these two candidate gene polymorphisms are not associated with disease susceptibility.

Transgenic models of autoimmune disease.

Transgenic and knockout mouse models have been invaluable for the elucidation of basic mechanisms in autoimmunity and have contributed new experimental models of human autoimmune diseases. Transgenic models of self tolerance have helped to change our view of this state from a process mediated purely by thymic deletion to a more complex process encompassing deletion, peripheral anergy, down-regulation of receptors and modulation by regulatory cells. Experiments in which the genes for the candidate target antigens in autoimmune disease are over-expressed or under-expressed have helped to clarify the targets of attack. Several examples of T cell receptor transgenic mice have been described in which T cells carry the receptor derived from a human or mouse autoimmune T cell clone. Such mice allow the characterization of T cell specificities contributing to disease and of the additional factors and checkpoints influencing disease development. In addition, the expression of disease associated HLA alleles in 'humanised' transgenic lines allows the mapping of HLA-restricted T cell epitopes and investigation of the mechanisms underlying these genetic associations. These approaches are leading to the generation of new disease models, offering hope for the design and testing of novel immunotherapeutic strategies.

Glutamic acid decarboxylase T lymphocyte responses associated with susceptibility or resistance to type I diabetes: analysis in disease discordant human twins, non-obese diabetic mice and HLA-DQ transgenic mice.

Glutamic acid decarboxylase (GAD65) has been implicated as a targeted self antigen in the immune destruction of pancreatic beta cells. T cell responses to GAD65 peptides have been detected in both patients with type I diabetes and in the non-obese diabetic (NOD) mouse. To establish which GAD65 epitopes are important in the immunopathogenesis of disease we initially compared T cell responses to GAD65 epitopes in conditions of disease susceptibility and protection. T cell responses to GAD65 peptides were measured in monozygotic twin pairs selected on the basis of disease discordance and T cell recognition of immunogenic regions of GAD65. Peptides of interest were then used to immunize susceptible NOD mice and H2-E transgenic NOD mice which are protected from diabetes. A differential response to the epitope GAD65 521-535 discriminated diabetic from non-diabetic human twins as well as susceptible from protected mice. This epitope as well as GAD 505-519 induces T cell responses despite binding the type I diabetes associated HLA-DQA1*0301/DQB1*0302 product with low affinity. Since DQ-restricted T cell responses are difficult to study in humans, HLA-DQ8 transgenic mice were then used: GAD epitopes 521-535 and 505-519 induced responses in DQ8 transgenic mice and T cell lines were established. Long-term T cell lines against GAD 505-519 were HLA-DQ restricted, and responded to peptide with a strong IFN-gamma and IL-10 response. The findings implicate GAD 521-535 as a possible target peptide in pathogenesis and are compatible with a model whereby self-reactive T cells specific for low-affinity peptide-MHC complexes may escape thymic negative selection.