Toll-like receptor 2 as a regulator of oral tolerance in the gastrointestinal tract.

Food allergy, other adverse immune responses to foods, inflammatory bowel disease, and eosinophilic esophagitis have become increasingly common in the last 30 years. It has been proposed in the "hygiene hypothesis" that dysregulated immune responses to environmental microbial stimuli may modify the balance between tolerance and sensitization in some patients. Of the pattern recognition receptors that respond to microbial signals, toll-like receptors (TLRs) represent the most investigated group. The relationship between allergy and TLR activation is currently at the frontier of immunology research. Although TLR2 is abundant in the mucosal environment, little is known about the complex relationship between bystander TLR2 activation by the commensal microflora and the processing of oral antigens. This review focuses on recent advances in our understanding of the relationship between TLR2 and oral tolerance, with an emphasis on regulatory T cells, eosinophils, B cells, IgA, intestinal regulation, and commensal microbes.

Mast cells and IgE activation do not alter the development of oral tolerance in a murine model.

BACKGROUND: In addition to their well-known role as potent effector cells in patients with allergic disease, mast cells have important immunomodulatory roles regulating tolerance in allograft rejection models. The roles of mast cells in oral tolerance development have not previously been examined. OBJECTIVE: We sought to evaluate the importance of mast cells, IgE-mediated mast cell activation, and histamine receptor 1 or 2 blockade on oral tolerance development in mice. METHODS: Oral tolerance was assessed in 2 mast cell-deficient murine strains (Kit(W-sh/W-sh) and Kit(W/W-v) mice) and control mice. Mice were fed ovalbumin (OVA) or peanut butter for 1 week and then immunized and boosted with relevant protein antigens. Antibody responses were assessed by using ELISA. The oral antihistamines pyrilamine and ranitidine were administered during tolerance induction to OVA. IgE-mediated mast cell activation was initiated during oral tolerance induction or OVA immunization. OVA-specific regulatory T cells were assessed in the Peyer patches, mesenteric lymph nodes, and spleens by using flow cytometry after adoptive transfer. RESULTS: Oral tolerance was successfully induced to OVA and peanut butter in mast cell-deficient mice. Kit(W-sh/W-sh) mice had higher proportions of antigen-specific regulatory T cells in the mesenteric lymph nodes than mast cell-containing control mice. However, mast cell reconstitution studies suggested this effect was mast cell independent. Oral antihistamine treatments with pyrilamine or ranitidine did not impair tolerance and neither did IgE-mediated activation. CONCLUSIONS: Mast cells are not necessary for the induction of oral tolerance, and allergic activation of mast cells does not impair tolerance to OVA. Oral antihistamine treatments do not disrupt the development of oral tolerance.

Use of existing systematic reviews for the development of evidence-based vaccination recommendations: Guidance from the SYSVAC expert panel.

National immunization technical advisory groups (NITAGs) develop immunization-related recommendations and assist policy-makers in making evidence informed decisions. Systematic reviews (SRs) that summarize the available evidence on a specific topic are a valuable source of evidence in the development of such recommendations. However, conducting SRs requires significant human, time, and financial resources, which many NITAGs lack. Given that SRs already exist for many immunization-related topics, and to prevent duplication and overlap of reviews, a more practical approach may be for NITAGs to use existing SRs. Nevertheless, it can be challenging to identify relevant SRs, to select one SR from among multiple SRs, or to critically assess and effectively use them. To support NITAGs, the London School of Hygiene and Tropical Medicine, Robert Koch Institute and collaborators developed the SYSVAC project, which consists of an online registry of systematic reviews on immunization-related topics and an e-learning course, that supports the use of them (both freely accessible at https://www.nitag-resource.org/sysvac-systematic-reviews). Drawing from the e-learning course and recommendations from an expert panel, this paper outlines methods for using existing systematic reviews when making immunization-related recommendations. With specific examples and reference to the SYSVAC registry and other resources, it offers guidance on locating existing systematic reviews; assessing their relevance to a research question, up-to-dateness, and methodological quality and/or risk of bias; and considering the transferability and applicability of their findings to other populations or settings.

IL-7Rα and L-selectin, but not CD103 or CD34, are required for murine peanut-induced anaphylaxis.

BACKGROUND: Allergy to peanuts results in severe anaphylactic responses in affected individuals, and has dramatic effects on society and public policy. Despite the health impacts of peanut-induced anaphylaxis (PIA), relatively little is known about immune mechanisms underlying the disease. Using a mouse model of PIA, we evaluated mice with deletions in four distinct immune molecules (IL7Rα, L-selectin, CD34, CD103), for perturbed responses. METHODS: PIA was induced by intragastric sensitization with peanut antigen and cholera toxin adjuvant, followed by intraperitoneal challenge with crude peanut extract (CPE). Disease outcome was assessed by monitoring body temperature, clinical symptoms, and serum histamine levels. Resistant mice were evaluated for total and antigen specific serum IgE, as well as susceptibility to passive systemic anaphylaxis. RESULTS: PIA responses were dramatically reduced in IL7Rα-/- and L-selectin-/- mice, despite normal peanut-specific IgE production and susceptibility to passive systemic anaphylaxis. In contrast, CD34-/- and CD103-/- mice exhibited robust PIA responses, indistinguishable from wild type controls. CONCLUSIONS: Loss of L-selectin or IL7Rα function is sufficient to impair PIA, while CD34 or CD103 ablation has no effect on disease severity. More broadly, our findings suggest that future food allergy interventions should focus on disrupting sensitization to food allergens and limiting antigen-specific late-phase responses. Conversely, therapies targeting immune cell migration following antigen challenge are unlikely to have significant benefits, particularly considering the rapid kinetics of PIA.

Ranking the relative importance of COVID-19 vaccination strategies in Canada: a priority-setting exercise.

BACKGROUND: When vaccine supplies are anticipated to be limited, necessitating the vaccination of certain groups earlier than others, the assessment of values and preferences of stakeholders is an important component of an ethically sound vaccine prioritization framework. The objective of this study was to conduct a priority-setting exercise to establish an expert stakeholder perspective on the relative importance of COVID-19 vaccination strategies in Canada. METHODS: The priority-setting exercise included a survey of stakeholders that was conducted from July 22 to Aug. 14, 2020. Stakeholders included clinical and public health expert groups, provincial and territorial committees and national Indigenous groups, patient and community advocacy representatives and experts, health professional associations and federal government departments. Survey results were analyzed to identify trends. RESULTS: Of 155 stakeholders contacted, 76 surveys were received for a participation rate of 49%. During a period of anticipated initial vaccine scarcity for all pandemic scenarios, stakeholders generally considered the most important vaccination strategy to be protecting those who are most vulnerable to severe illness and death from COVID-19. This was followed in importance by strategies to protect health care capacity, minimize transmission of SARS-CoV-2 and protect critical infrastructure. INTERPRETATION: This priority-setting exercise established that there is general alignment in the values and preferences across stakeholder groups: the most important vaccination strategy at the time of limited initial vaccine availability is to protect those who are most vulnerable. The findings of this priority-setting exercise provided a timely expert perspective to guide early public health planning for COVID-19 vaccines.

Navigating inequities: a roadmap out of the pandemic.

The COVID-19 pandemic has exposed social inequities that rival biological inequities in disease exposure and severity. Merely identifying some inequities without understanding all of them can lead to harmful misrepresentations and deepening disparities. Applying an 'equity lens' to bring inequities into focus without a vision to extinguish them is short-sighted. Interventions to address inequities should be as diverse as the pluralistic populations experiencing them. We present the first validated equity framework applied to COVID-19 that sheds light on the full spectrum of health inequities, navigates their sources and intersections, and directs ethically just interventions. The Equity Matrix also provides a comprehensive map to guide surveillance and research in order to unveil epidemiological uncertainties of novel diseases like COVID-19, recognising that inequities may exist where evidence is currently insufficient. Successfully applied to vaccines in recent years, this tool has resulted in the development of clear, timely and transparent guidance with positive stakeholder feedback on its comprehensiveness, relevance and appropriateness. Informed by evidence and experience from other vaccine-preventable diseases, this Equity Matrix could be valuable to countries across the social gradient to slow the spread of SARS-CoV-2 by abating the spread of inequities. In the race to SARS-CoV-2 vaccines, this urgently needed roadmap can effectively and efficiently steer global leadership towards equitable allocation with diverse strategies for diverse inequities. Such a roadmap has been absent from discussions on managing the COVID-19 pandemic, and is critical for our passage out of it.

Health inequities related to vaccination: An evidence map of potentially influential factors and systematic review of interventions.

INTRODUCTION: The National Advisory Committee on Immunization (NACI) makes recommendations for vaccines in Canada. To inform considerations for equity when making recommendations, the NACI Secretariat developed a matrix of factors that may influence vaccine equity. To inform the matrix we mapped the evidence for P2ROGRESS And Other factors potentially associated with unequal levels of illness or death from vaccine-preventable diseases (VPDs) and systematically reviewed the evidence for interventions aimed at reducing inequities. METHODS: In October 2019 we searched Medline, Embase, and CINAHL. Two reviewers agreed on the included studies. Our primary outcomes were VPD-related hospitalizations and deaths. Secondary outcomes were differential vaccine access, and exposure, susceptibility, severity, and consequences of VPDs. Two reviewers appraised the certainty of evidence. We mapped the evidence for P2ROGRESS And Other factors and summarized the findings descriptively. We summarized the interventions narratively. RESULTS: We identified 413 studies reporting on P2ROGRESS And Other factors. The most commonly investigated factors included age (n = 374, 89%), pre-existing conditions (n = 179, 42%), and gender identity or sex (n = 144, 34%). We identified 2 trials investigating the effects of interventions. One (n = 1249) provided very low certainty evidence that staff vaccination policies may reduce hospitalizations and deaths from influenza among private care home residents. The other (n not reported) provided very low certainty evidence that universal vaccination by nurses in clinics may reduce hospitalizations for rotavirus gastroenteritis compared with vaccination by physicians or no intervention. CONCLUSIONS: There is a large body of studies reporting on hospitalizations and deaths from VPDs stratified by P2ROGRESS And Other factors. We found only two trials examining the effects of interventions on hospitalization for or mortality from VPDs. This review has been helpful to NACI and will be helpful to similar organizations aiming to systematically identify and target health inequities through the development of vaccine program recommendations.

A systematic review of factors that influence the acceptability of vaccines among Canadians.

BACKGROUND: Canada's National Advisory Committee on Immunization (NACI) provides guidance on the use of vaccines in Canada. To support the expansion of its mandate to include considerations for vaccine acceptability when making recommendations, the NACI Secretariat developed a matrix of factors that influence acceptability. To inform and validate the matrix, we systematically reviewed evidence for factors that influence vaccine acceptability, and for interventions aimed at improving acceptability. METHODS: On 10-11 October 2018 we searched four bibliographic databases, the Theses Canada Portal, and ClinicalTrials.gov. Two reviewers agreed on the included studies. From each study, we extracted information about the participants, intervention or exposure, comparator, and relevant outcomes. Due to heterogeneity in the reported factors and acceptability indicators we synthesized the findings narratively. We appraised the certainty of evidence using GRADE. For each vaccine-preventable disease we populated a matrix of factors for which there was evidence of an influence on acceptability. RESULTS: One hundred studies (>1 million participants) contributed data relevant to the public, 16 (6191 participants) to healthcare providers, and three (84 participants) to policymakers. There were 43 intervention studies (~2 million participants). Across vaccines, we identified low certainty evidence for 70 factors relevant to the general population, 56 to high-risk groups, and 30 to healthcare providers. The perceived safety and importance of the vaccine, vaccination history, and receiving a recommendation from a healthcare provider were common influential factors. We found low certainty evidence that reminders for childhood vaccines and policies or delivery models for rotavirus vaccines could improve uptake and coverage. Evidence for other interventions was of very low certainty. CONCLUSIONS: The NACI vaccine acceptability matrix is useful for categorizing acceptability factors for the general public. Reminder systems may improve the uptake of childhood vaccines. Policies that make the rotavirus vaccine universally available and easily accessible may improve coverage. FUNDING: This systematic review was completed under contract to the Public Health Agency of Canada, Contract #4600001536.

Using existing systematic reviews for developing vaccination recommendations: Results of an international expert workshop.

National immunization technical advisory groups (NITAGs) develop immunization-related recommendations. Systematic reviews are recommended to be used in this process, but conducting them requires significant resources, which many NITAGs lack. Using existing systematic reviews could help address this problem. The Robert Koch Institute and collaborators set up the SYSVAC2 project to facilitate the retrieval of existing systematic reviews and offer guidance on using them. This will include an online registry of systematic reviews relevant to immunization policy and an online course on how to use existing reviews. This report describes an international expert workshop held in December 2019 to develop consensus on methods for using existing reviews and other relevant factors for the registry and course. Members from NITAGs representing different regions of the world presented their experiences of using systematic reviews and reflected on challenges inhibiting use. Three methodologists considered different aspects of using systematic reviews. Interactive sessions followed, where implications for SYSVAC2 were discussed. Participants supported having critical appraisal ratings, plain language summaries, keyword search, and data visualization functions in the registry. They suggested tailoring course content to different audiences and including overviews of reviews as a topic and examples of how NITAGs have used or could use existing reviews. Participants agreed that whether a review is out-of-date should be decided by those using the review rather than registry staff. The registry could help by highlighting the date of literature search or included primary studies. Participants recommended a visualization function to highlight overlap across reviews and guidance on handling challenges to using reviews, ideally, involving a practical element. No consensus was reached on which critical appraisal tool to use for reviews in the registry, but a majority of participants wanted registry staff to perform appraisals. Formative research is planned before the registry and online course are launched in 2020.

A framework for the systematic consideration of ethics, equity, feasibility, and acceptability in vaccine program recommendations.

For the successful implementation of population-level recommendations, it is critical to consider the full spectrum of public health science, including clinical and programmatic factors. Current frameworks may identify various factors that should be examined when making evidence-informed vaccine-related recommendations. However, while most immunization guidelines systematically assess clinical factors, such as efficacy and safety of vaccines, there is no published framework outlining how to systematically assess programmatic factors, such as the ethics, equity, feasibility, and acceptability of recommendations. We have addressed this gap with the development of the EEFA (Ethics, Equity Feasibility, Acceptability) Framework, supported by evidence-informed tools, including Ethics Integrated Filters, Equity Matrix, Feasibility Matrix, and an Acceptability Matrix. The Framework and tools are based on five years of environmental scans, systematic reviews and surveys, and refined by expert and stakeholder consultations and feedback. For each programmatic factor, the EEFA Framework summarizes the minimum threshold for consideration and when further in-depth analysis may be required, which aspects of the factor should be considered, how to assess the factor using the supporting evidence-informed tools, and who should be consulted to complete the assessment. Research, particularly in the fields of vaccine acceptability and equity, has validated the utility and comprehensiveness of the tools. The Framework has been successfully used in Canada for clear, timely, transparent vaccine guidance with positive stakeholder feedback on its comprehensiveness, relevance and appropriateness. Applying the EEFA Framework allows for the systematic consideration of the spectrum of public health science without a delay in recommendations, complementing existing decision-making frameworks. This Framework will therefore be useful for advisory groups worldwide to integrate critical factors that could impact the successful and timely implementation of comprehensive, transparent recommendations, and will further the global objective of developing practical and evidence-informed immunization policies.

Risk of bias tools in systematic reviews of health interventions: an analysis of PROSPERO-registered protocols.

BACKGROUND: Systematic reviews of health interventions are increasingly incorporating evidence outside of randomized controlled trials (RCT). While non-randomized study (NRS) types may be more prone to bias compared to RCT, the tools used to evaluate risk of bias (RoB) in NRS are less straightforward and no gold standard tool exists. The objective of this study was to evaluate the planned use of RoB tools in systematic reviews of health interventions, specifically for reviews that planned to incorporate evidence from RCT and/or NRS. METHODS: We evaluated a random sample of non-Cochrane protocols for systematic reviews of interventions registered in PROSPERO between January 1 and October 12, 2018. For each protocol, we extracted data on the types of studies to be included (RCT and/or NRS) as well as the name and number of RoB tools planned to be used according to study design. We then conducted a longitudinal analysis of the most commonly reported tools in the random sample. Using keywords and name variants for each tool, we searched PROSPERO records by year since the inception of the database (2011 to December 7, 2018), restricting the keyword search to the "Risk of bias (quality) assessment" field. RESULTS: In total, 471 randomly sampled PROSPERO protocols from 2018 were included in the analysis. About two-thirds (63%) of these planned to include NRS, while 37% restricted study design to RCT or quasi-RCT. Over half of the protocols that planned to include NRS listed only a single RoB tool, most frequently the Cochrane RoB Tool. The Newcastle-Ottawa Scale and ROBINS-I were the most commonly reported tools for NRS (39% and 33% respectively) for systematic reviews that planned to use multiple RoB tools. Looking at trends over time, the planned use of the Cochrane RoB Tool and ROBINS-I seems to be increasing. CONCLUSIONS: While RoB tool selection for RCT was consistent, with the Cochrane RoB Tool being the most frequently reported in PROSPERO protocols, RoB tools for NRS varied widely. Results suggest a need for more education and awareness on the appropriate use of RoB tools for NRS. Given the heterogeneity of study designs comprising NRS, multiple RoB tools tailored to specific designs may be required.