The Prevalence of IgE-Mediated Food Allergy and Other Allergic Diseases in the First 10 Years: The Population-Based, Longitudinal HealthNuts Study

BACKGROUND

There are limited longitudinal data on the population prevalence of allergic conditions during childhood, and few studies have incorporated the reference standard oral food challenge to confirm food allergy.

OBJECTIVE

To describe the population prevalence of IgE-mediated food allergy, eczema, asthma, and rhinitis at ages 6 and 10 years in Melbourne, Australia.

METHODS

The HealthNuts study recruited 5,276 1-year-old infants in Melbourne, Australia, with repeat assessments at ages 6 and 10 years. At ages 6 and 10 years, carers completed a questionnaire on symptoms and doctor diagnosis of allergic conditions (International Study of Asthma and Allergies in Children). Children were invited to attend a clinic assessment including skin prick test, lung function tests, and oral food challenges when indicated. To minimize the impact of attrition bias, prevalence estimates among participants at ages 6 and 10 years were weighted to reflect characteristics of the whole cohort at recruitment.

RESULTS

In total, 4,455 and 4,065 families participated at ages 6 and 10 years, respectively (84% and 77% of the original cohort). Of those, 73% and 55% of participants ages 6 and 10 years, respectively, completed clinical assessments. Overall, 36.5% (95% CI, 34.8-38.2) and 38.2% (95% CI, 36.5-40.1%) of 6- and 10-year-olds had at least one current allergic disease, and around one third of those had two or more allergic diseases. Food allergy occurred in 6.4% (95% CI, 5.6-7.2) of 6-year olds and 6.3% (95% CI, 5.5-7.2) of 10-year-olds. Among infants with challenge-confirmed food allergy in infancy, 45% had persistent disease at age 10 years. The prevalence of current diagnosed asthma at ages 6 and 10 years were 12.1% (95% CI, 10.9-13.3) and 13.1% (95% CI, 11.9-14.4), respectively, current eczema decreased slightly from 15.3% (95% CI, 14.1-19.7) at age 6 years to 12.9% (95% CI, 11.7-14.2) at age 10 years, and current rhinitis increased from 15.1% (95% CI, 13.9-16.5) at age 6 years to 25.0% (95% CI, 23.4-26.7) at age 10 years.

CONCLUSIONS

Allergic diseases affect 40% of primary school-age children; one third have multiple allergic diagnoses. Challenge-confirmed food allergy prevalence remains high, and 45% of infants with food allergy have persistent disease to age 10 years.

Interaction Between Baseline Participant Factors and Treatment Effects Following Peanut Oral Immunotherapy

BACKGROUND

The Probiotic Peanut Oral Immunotherapy-003 multicenter randomized trial found that both probiotic peanut oral immunotherapy (PPOIT) and peanut OIT alone (OIT) were effective compared with placebo in inducing clinical remission after 18 months of treatment, and improving health-related quality of life (HRQL) at 12 months after treatment. Understanding treatment effect modifiers can optimize outcomes through precision care.

OBJECTIVES

This post hoc study examined baseline clinical and demographic participant factors that modified treatment effects.

METHODS

The study sample included 201 children (aged 1-10 years) with challenge-confirmed peanut allergy. Exposure variables were baseline clinical and demographic factors. Outcomes were remission (double-blind, placebo-controlled food challenge, cumulative 4,950-mg peanut protein at 8 weeks after treatment) and HRQL (change in Food Allergy Quality of Life Questionnaire-Parent Form score). Interactions between baseline factors and treatment effects on remission and HRQL were explored with regression models.

RESULTS

A higher degree of peanut sensitivity (large peanut skin prick test, high peanut specific IgE, and low reaction-eliciting dose at study entry challenge) and other concurrent allergic conditions (multiple food allergies, asthma, or wheeze) were associated with the decreased likelihood of attaining remission after both PPOIT and OIT treatment. History of anaphylaxis was associated with the reduced likelihood of remission after PPOIT compared with OIT. For the HRQL outcome, there was evidence that sex, history of anaphylaxis, and age modified treatment effects.

CONCLUSIONS

Baseline participant factors modify PPOIT and OIT effects on remission and HRQL. Considering modifiers of treatment effect during participant selection may optimize treatment success and clinical trial design toward specific outcomes, such as the achievement of remission.

Associations between gender and health-related quality of life in people with IgE-mediated food allergy and their caregivers: A systematic review

OBJECTIVE

Understanding factors that impact health-related quality of life (HRQL) is essential to inform personalised food allergy management. However, there are inconsistencies about the impact of gender on HRQL in food allergy. This review aimed to collate all investigations of the association between gender and total or subdomain HRQL scores of individuals with food allergy and their caregivers.

DESIGN

This is a narrative systematic review. We descriptively synthesised and compared HRQL outcomes by participant and parent genders according to statistical and clinical significance. Study quality was assessed using the ROBINS-I, inclusive of all domains. Sensitivity analysis of non-interventional studies was conducted using the ROBINS-E.

DATA SOURCES

A systematic search of Medline and Embase databases was conducted on 4 April 2022 and updated on 5 December 2023.

ELIGIBILITY CRITERIA

Studies were eligible for inclusion if they reported original data on the association between any sex and/or gender and HRQL, as measured with any validated instrument, in populations with IgE-mediated food allergy. Interventional and non-interventional studies were eligible.

RESULTS

A comparison of 34 eligible studies (10 interventional and 24 non-interventional) indicated females with food allergy (62.5% of studies of children, 83.3% of studies of adults) and mothers of children with food allergy (50% of studies of caregivers) experienced poorer self-reported baseline HRQL than their counterparts, notably in domains of physical, emotional or food anxiety-related well-being. Gender differences in child HRQL after food allergen immunotherapy were observed. However, selective reporting in included interventional studies meant the direction of this association could not be determined. The proxy-reported total HRQL of participants was not affected by caregiver gender, nor was caregiver HRQL likely impacted by child gender.

CONCLUSIONS

Gender should be considered an important modifier of participant HRQL outcomes in food allergy studies. Purposeful exploration of HRQL in all genders is needed to fully understand the implications of this construct on the lived experience of food allergy.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO (CRD42022329901).

Cost-effectiveness analysis of probiotic peanut oral immunotherapy (PPOIT) versus placebo in Australian children with peanut allergy alongside a randomised trial

OBJECTIVE

To compared the cost-effectiveness of coadministration of a probiotic adjuvant with peanut oral immunotherapy (PPOIT) with placebo (no treatment) in children with peanut allergy.

DESIGN

Prospectively planned cost-effectiveness analysis alongside a randomised control trial.

SETTING

The Royal Children's Hospital, Melbourne, Australia.

PARTICIPANTS

56 children with peanut allergy aged 1-10 years at recruitment.

INTERVENTION

A daily dose of probiotic Lactobacillus rhamnosus CGMCC 1.3724 (NCC4007) and peanut oral immunotherapy administered for 1.5 years.

MAIN OUTCOMES MEASURES

Costs were considered from a healthcare system perspective and included costs of treatment delivery and adverse events. Effectiveness outcomes included rate of sustained unresponsiveness (SU) and quality-adjusted life years (QALYs). The cost-effectiveness of PPOIT versus placebo was analysed using patient-level data. Time horizon was 10 years from commencement of PPOIT treatment, comprising 1.5 years of treatment (actual data), 4 years of post-treatment follow-up (actual data), and 4.5 years of extrapolation thereafter (modelling).

RESULTS

Healthcare cost per patient over 10 years was higher for PPOIT compared with placebo ($A9355 vs $A1031, p<0.001). Over half of the per patient healthcare cost (53%) in the PPOIT group was attributable to treatment delivery, while the remaining cost was attributable to adverse events. Both measures of effectiveness were superior in the PPOIT group: the average SU rate over 10 years was 54% for PPOIT versus 6% for placebo (p<0.001); QALYs over 10 years were 9.05 for PPOIT versus 8.63 for placebo (p<0.001). Overall, cost per year of SU achieved was $A1694 (range $A1678, $A1709) for PPOIT compared with placebo, and cost per additional QALY gained was $A19 386 (range $A19 024, $A19 774).

CONCLUSIONS

Cost per QALY gained using PPOIT compared with no treatment is approximately $A20 000 (£10 000) and is well below the conventional value judgement threshold of $A50 000 (£25 000) per QALY gained, thus deemed good value for money ($A1= £0.5 approximately).

TRIAL REGISTRATION NUMBER

Australian New Zealand Clinical Trials Registry ACTRN12608000594325; Post-results.

Inborn Errors of Immunity in Children With Invasive Pneumococcal Disease: A Multicenter Prospective Study

BACKGROUND

In settings with universal conjugate pneumococcal vaccination, invasive pneumococcal disease (IPD) can be a marker of an underlying inborn error of immunity. The aim of this study was to determine the prevalence and characterize the types of immunodeficiencies in children presenting with IPD.

METHODS

Multicenter prospective audit following the introduction of routinely recommended immunological screening in children presenting with IPD. The minimum immunological evaluation comprised a full blood examination and film, serum immunoglobulins (IgG, IgA and IgM), complement levels and function. Included participants were children in whom Streptococcus pneumoniae was isolated from a normally sterile site (cerebrospinal fluid, pleura, peritoneum and synovium). If isolated from blood, features of sepsis needed to be present. Children with predisposing factors for IPD (nephrotic syndrome, anatomical defect or malignancy) were excluded.

RESULTS

Overall, there were 379 episodes of IPD of which 313 (83%) were eligible for inclusion and 143/313 (46%) had an immunologic evaluation. Of these, 17/143 (12%) were diagnosed with a clinically significant abnormality: hypogammaglobulinemia (n = 4), IgA deficiency (n = 3), common variable immunodeficiency (n = 2), asplenia (n = 2), specific antibody deficiency (n = 2), incontinentia pigmenti with immunologic dysfunction (n = 1), alternative complement deficiency (n = 1), complement factor H deficiency (n = 1) and congenital disorder of glycosylation (n = 1). The number needed to investigate to identify 1 child presenting with IPD with an immunologic abnormality was 7 for children under 2 years and 9 for those 2 years old and over.

CONCLUSIONS

This study supports the routine immune evaluation of children presenting with IPD of any age, with consideration of referral to a pediatric immunologist.

Association of Reaction Symptoms and Eliciting Dose With Health-Related Quality of Life in Children With Peanut Allergy

BACKGROUND

Food allergy adversely affects the health-related quality of life (HRQoL) of patients. It is unclear whether factors such as the reaction eliciting dose (ED) and the nature of allergic reaction symptoms affect HRQoL.

OBJECTIVE

To explore associations between reaction ED or the nature of allergic symptoms and HRQoL among children with peanut allergy.

METHODS

This study was a secondary analysis of baseline data from the PPOIT-003 randomized trial in 212 children aged 1 to 10 years with challenge-confirmed peanut allergy. Children's past reaction symptoms were collected by clinicians during screening. Associations between variables of interest and parent-reported child-proxy HRQoL were examined by univariable and multivariable linear regression.

RESULTS

Mean age of study participants was 5.9 years; 63.2% were male. Children with a low reaction ED of 80 mg peanut protein had significantly poorer HRQoL (β = -0.81; 95% CI, -1.61 to -0.00; P = .049) compared with children with a high ED of 2,500 mg peanut protein. Gastrointestinal symptoms (β = 0.45; 95% CI, 0.03-0.87; P = .037), lower airway symptoms (β = 0.46; 95% CI, 0.05-0.87; P = .030), multisystem involvement (β = 0.71; 95% CI, 0.25-1.16; P = .003), or anaphylaxis (β = 0.46; 95% CI, 0.04-0.87; P = .031) during a previous reaction were associated with worse HRQoL.

CONCLUSIONS

Peanut-allergic children with a lower allergen reaction threshold experienced a greater negative HRQoL impact compared with children with higher reaction thresholds. In addition, specific past allergic reaction symptoms were associated with comparatively worse HRQoL. Children experiencing these symptoms and those with lower reaction ED require increased clinical support to manage the food allergy and are likely to benefit from interventions that can improve HRQoL.

Food Allergen Immunotherapy in Preschool Children: Do We Have the Evidence?

Standard care for the management of food allergies previously centered on allergen avoidance and the treatment of adverse reactions after allergen exposure. An increase in the development of immunotherapy treatments for food allergy has occurred over the past 2 decades, with many centers now offering immunotherapy. Previous studies mainly focused on school-age children in whom food allergies are likely to be persistent. However, there is increasing evidence that delivering immunotherapy for food allergy to preschool-age children may deliver higher rates of success, and that peanut allergen immunotherapy leads the way. Conversely, the natural resolution of food allergies occurs primarily in these younger age groups, resulting in challenges to selecting patients who will ultimately benefit from these treatments. Both immunotherapy and natural history studies reveal the inherent plasticity of the immune system in early life, which may be more amenable to intervention, but this raises a delicate yet unknown balance between the optimal timing of intervention versus waiting for natural resolution of the food allergy. Here we review the evidence for early food allergen immunotherapy in preschoolers, and present the pros and cons of this approach while acknowledging important research gaps in this age group.

Social association predicts immunological similarity in rewilded mice

Environmental influences on immune phenotypes are well-documented, but our understanding of which elements of the environment affect immune systems, and how, remains vague. Behaviors, including socializing with others, are central to an individual's interaction with its environment. We tracked behavior of rewilded laboratory mice of three inbred strains in outdoor enclosures and examined contributions of behavior, including social associations, to immune phenotypes. We found that the more associated two individuals were, the more similar their immune phenotypes were. Social association was particularly predictive of similar memory T and B cell profiles and was more influential than sibling relationships or worm infection status. These results highlight the importance of social networks for immune phenotype and reveal important immunological correlates of social life.

TreEAT trial: Protocol for a randomized controlled trial investigating the efficacy and safety of early introduction of tree nuts for the prevention of tree nut allergy in infants with peanut allergy

INTRODUCTION

Children with peanut allergy are at increased risk of developing tree nut allergies, which can be severe and for most lifelong. Introduction of peanut in the first year of life can reduce the risk of peanut allergy; however, prevention strategies for tree nut allergies have not been established. We aimed to test the efficacy and safety of a novel strategy, a supervised multi-nut oral food challenge (OFC) compared with standard care for tree nut allergy prevention in infants at high risk of developing tree nut allergy, TreEAT.

METHODS AND ANALYSIS

TreEAT is a 2-armed, open-label, randomized, controlled trial (RCT). Infants (n = 212) aged 4-11 months with peanut allergy will be randomized 1:1 at peanut allergy diagnosis to either a hospital-based multi-tree nut (almond, cashew, hazelnut, and walnut) OFC using multi-nut butter or standard care (home introduction of individual tree nuts). All infants will be assessed at age 18 months, with questionnaires and SPT to peanut and tree nuts. Peanut and tree nut OFCs will be performed as required to determine the allergy status for each nut. The primary outcome is tree nut allergy at age 18 months. Secondary outcomes include peanut allergy resolution, proportion, and severity of adverse events related to tree nut ingestion, number and frequency of tree nuts ingested, quality of life and parental anxiety, and allergy-related healthcare visits from randomization to 18 months of age. Analyses will be performed on an intention-to-treat basis.

ETHICS AND DISSEMINATION

TreEAT was approved by the Royal Children's Hospital Human Research Ethics Committee (#70489). Outcomes will be presented at scientific conferences and disseminated through publication.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov ID: NCT04801823.

Varying Approaches to Management of IgE-Mediated Food Allergy in Children Around the World

Food allergy is a chronic disease that affects individuals of all ages and is a significant public health problem globally. This narrative overview examines clinical management strategies for IgE-mediated food allergy in children around the world to understand variations in practice. Information was drawn from clinical practice guidelines, recent research, the websites of professional and governmental bodies with expertise in food allergy, and clinical experts from a broad cross-section of geographical regions. The structure and delivery of clinical services, allergen avoidance and food labeling, and resources to support the management of allergic reactions in the community are discussed in detail. The adoption of emerging food immunotherapies is also explored. Wide variations in clinical management of food allergy were apparent across the different countries. Common themes were continuing issues with access to specialist care and recognition of the need to balance risk reduction with dietary and social restrictions to avoid unnecessary detrimental impacts on the quality of life of food allergy sufferers. Findings highlight the need for standardized presentation of practice and priorities, and may assist clinicians and researchers when engaging with government and funding agencies to address gaps.

Probiotic peanut oral immunotherapy versus oral immunotherapy and placebo in children with peanut allergy in Australia (PPOIT-003): a multicentre, randomised, phase 2b trial

BACKGROUND

Oral immunotherapy is effective at inducing desensitisation to allergens and induces sustained unresponsiveness (ie, clinical remission) in a subset of patients, but causes frequent reactions. We aimed to investigate whether addition of a probiotic adjuvant improved the efficacy or safety of peanut oral immunotherapy.

METHODS

PPOIT-003, a multicentre, randomised, phase 2b trial, was conducted in three tertiary hospitals in Australia (Adelaide [SA], Melbourne [VIC], and Perth [WA]) in children aged 1-10 years, weighing more than 7 kg, with peanut allergy confirmed by a double-blind placebo-controlled food challenge (cumulative 4950 mg dose of peanut protein) and positive peanut skin prick test (≥3 mm) or peanut-specific IgE (≥0·35 kU/L). Children were randomly assigned (2:2:1) to receive probiotic and peanut oral immunotherapy (PPOIT), placebo probiotic and peanut oral immunotherapy (OIT), or placebo probiotic and placebo OIT (placebo) for 18 months, and were followed up until 12 months after completion of treatment. Oral immunotherapy consisted of increasing doses of peanut protein (commercially available food-grade 12% defatted peanut flour [50% peanut protein]) until a 2000 mg daily maintenance dose was reached. The probiotic adjuvant was a daily dose of 2 × 10¹⁰ colony-forming units of the probiotic Lactobacillus rhamnosus ATCC 53103. Placebo immunotherapy comprised maltodextrin, brown food colouring, and peanut essence, and placebo probiotic was maltodextrin. Dual primary outcomes were 8-week sustained unresponsiveness, defined as no reaction to a cumulative dose of 4950 mg peanut protein at treatment completion and 8 weeks after treatment completion, in the PPOIT versus placebo groups and the PPOIT versus OIT groups, analysed by intention to treat. Safety endpoints were adverse events during the treatment phase, and peanut ingestion and reactions in the 12-month post-treatment period. This study is registered with the Australian New Zealand Clinical Trials Registry, 12616000322437.

FINDINGS

Between July 4, 2016, and Sept 21, 2020, 201 participants were enrolled and included in the intention-to-treat analysis. 36 (46%) of 79 children in the PPOIT group and 42 (51%) of 83 children in the OIT group achieved sustained unresponsiveness compared with two (5%) of 39 children in the placebo group (risk difference 40·44% [95% CI 27·46 to 53·42] for PPOIT vs placebo, p<0·0001), with no difference between PPOIT and OIT (-5·03% [-20·40 to 10·34], p=0·52). Treatment-related adverse events were reported in 72 (91%) of 79 children in the PPOIT group, 73 (88%) of 83 children in the OIT group, and 28 (72%) of 39 children in the placebo group. Exposure-adjusted incidence of adverse events was 10·58 in the PPOIT group, 11·36 in the OIT, and 2·09 in the placebo group (ratio 0·92 [95% CI 0·85 to 0·99] for PPOIT vs OIT, p=0·042; 4·98 [4·11-6·03] for PPOIT vs placebo, p<0·0001; 5·42 [4·48-6·56] for OIT vs placebo, p<0·0001), with differences seen primarily in gastrointestinal symptoms and in children aged 1-5 years. During the 12-month post-treatment period, 60 (85%) of 71 participants in the PPOIT group, 60 (86%) of 70 participants in the OIT group, and six (18%) of 34 participants in the placebo group were eating peanut; rescue epinephrine use was infrequent (two [3%] of 71 in the PPOIT group, four [6%] of 70 in the OIT group, and none in the placebo group).

INTERPRETATION

Both PPOIT and OIT were effective at inducing sustained unresponsiveness. Addition of a probiotic did not improve efficacy of OIT, but might offer a safety benefit compared with OIT alone, particularly in preschool children.

FUNDING

National Health and Medical Research Council Australia and Prota Therapeutics.

Study protocol of a phase 2, dual-centre, randomised, controlled trial evaluating the effectiveness of probiotic and egg oral immunotherapy at inducing desensitisation or sustained unresponsiveness (remission) in participants with egg allergy compared with placebo (Probiotic Egg Allergen Oral Immunotherapy for Treatment of Egg Allergy: PEAT study)

INTRODUCTION

Egg allergy is the most common food allergy in children but recent studies have shown persistence or delayed resolution into adolescence. As there is currently no effective long-term treatment, definitive treatments that improve quality of life and prevent fatalities for food allergies are required. We have previously shown that a novel treatment comprising a combination of the probiotic Lactobacillus rhamnosus CGMCC 1.3724 with peanut oral immunotherapy (OIT) is highly effective at inducing sustained unresponsiveness, with benefit persisting to 4 years after treatment cessation in the majority of initial treatment responders. In this study, we plan to extend the probiotic food OIT platform to another allergen, namely egg. We describe the protocol for a phase 2, dual-centre, randomised, controlled trial evaluating the effectiveness of probiotic and egg OIT at inducing desensitisation or sustained unresponsiveness (remission) in participants with egg allergy compared with placebo.

METHODS AND ANALYSIS

80 participants aged 5-30 years of age with current egg allergy confirmed by double-blind placebo-controlled food challenge at study screening will be recruited from Australia and Singapore. There are two intervention arms-probiotic and egg OIT (active) or placebo. Interventions are administered once daily for 18 months. The primary outcome is the proportion of participants who attain 8-week sustained unresponsiveness in the active group versus placebo group.

ETHICS AND DISSEMINATION

This study has been approved by the Human Research Ethics Committees at the Royal Children's Hospital (HREC 2019.082) and the National Healthcare Group Domain Specific Review Board (2019/00029). Results will be published in peer-reviewed journals and disseminated via presentations at international conferences.

TRIAL REGISTRATION NUMBER

ACTRN12619000480189.

Study protocol of a multicentre, randomised, controlled trial evaluating the effectiveness of probiotic and peanut oral immunotherapy (PPOIT) in inducing desensitisation or tolerance in children with peanut allergy compared with oral immunotherapy (OIT) alone and with placebo (the PPOIT-003 study)

INTRODUCTION

Peanut allergy is the the most common cause of life-threatening food-induced anaphylaxis. There is currently no effective long-term treatment. There is a pressing need for definitive treatments that improve the quality of life and prevent fatalities. Allergen oral immunotherapy (OIT) is a promising approach, which is effective at inducing desensitisation; however, OIT has a limited ability to induce sustained unresponsiveness (SU). We have previously shown that a novel treatment comprising a combination of the probiotic Lactobacillus rhamnosus CGMCC 1.3724 with peanut OIT (Probiotic Peanut Oral ImmunoTherapy (PPOIT)) is highly effective at inducing SU, with benefit persisting to 4 years after treatment cessation in the majority of initial treatment responders. Here we describe the protocol for a Phase IIb multicentre, double-blind, randomised, controlled trial (PPOIT-003) with dual primary objectives to evaluate the effectiveness of PPOIT at inducing SU (assessed at 8 weeks after treatment cessation) compared with placebo treatment and peanut OIT alone, in children with peanut allergy.

METHODS AND ANALYSIS

200 children 1 to 10 years of age with current peanut allergy confirmed by failed double-blind placebo-controlled food challenge (DBPCFC) at study screening will be recruited from three tertiary paediatric hospitals in Australia. There are three intervention arms-PPOIT, peanut OIT alone or placebo. Interventions are administered once daily for 18 months. The dual primary outcomes are: (1) the proportion of children who attain 8-week SU in the PPOIT group versus placebo group and (2) the proportion of children who attain 8-week SU in the PPOIT group versus OIT group.

ETHICS AND DISSEMINATION

This study has been approved by the Human Research Ethics Committees at the Royal Children's Hospital (HREC 35246) and the Child and Adolescent Health Service (RGS 2543). Results will be published in peer-reviewed journals and disseminated via presentations at international conferences.

TRIAL REGISTRATION NUMBER

ACTRN12616000322437.

Helminths and the microbiota: parts of the hygiene hypothesis

In modern societies, diseases that are driven by dysregulated immune responses are increasing at an alarming pace, such as inflammatory bowel diseases and diabetes. There is an urgent need to understand these epidemiological trends, which are likely to be driven by the changing environment of the last few decades. There are complex interactions between human genetic factors and this changing environment that is leading to the increasing prevalence of metabolic and inflammatory diseases. Alterations to human gut bacterial communities (the microbiota) and lowered prevalence of helminth infections are potential environmental factors contributing to immune dysregulation. Helminths have co-evolved with the gut microbiota and their mammalian hosts. This three-way interaction is beginning to be characterized, and the knowledge gained may enable the design of new therapeutic strategies to treat metabolic and inflammatory diseases. However, these complex interactions need to be carefully investigated in the context of host genetic backgrounds to identify optimal treatment strategies. The complex nature of these interactions raises the possibility that only with highly personalized treatment, with knowledge of individual genetic and microbiota communities, will therapeutic interventions be successful for a majority of the individuals suffering from these complex diseases of immune dysregulation.

Systemic impact of intestinal helminth infections

In this review, we examine the evidence that intestinal helminths can control harmful inflammatory responses and promote homeostasis by triggering systemic immune responses. Induction of separable components of immunity by helminths, which includes type 2 and immune regulatory responses, can both contribute toward the reduction in harmful type 1 immune responses that drive certain inflammatory diseases. Despite inducing type 2 responses, intestinal helminths may also downregulate harmful type 2 immune responses including allergic responses. We consider the possibility that intestinal helminth infection may indirectly affect inflammation by influencing the composition of the intestinal microbiome. Taken together, the studies reviewed herein suggest that intestinal helminth-induced responses have potent systemic effects on the immune system, raising the possibility that whole parasites or specific molecules produced by these metazoans may be an important resource for the development of future immunotherapies to control inflammatory diseases.

IL-22-producing CD4+ cells are depleted in actively inflamed colitis tissue

T helper type (Th17) cytokines such as interleukin (IL)-17A and IL-22 are important in maintaining mucosal barrier function and may be important in the pathogenesis of inflammatory bowel diseases (IBDs). Here, we analyzed cells from the colon of IBD patients and show that Crohn's disease (CD) patients had significantly elevated numbers of IL-17+, CD4+ cells compared with healthy controls and ulcerative colitis (UC) patients, but these numbers did not vary based on the inflammatory status of the mucosa. By contrast, UC patients had significantly reduced numbers of IL-22+ cells in actively inflamed tissues compared with both normal tissue and healthy controls. There was a selective increase in mono-IL-17-producing cells from the mucosa of UC patients with active inflammation together with increased expression of transforming growth factor (TGF)-β and c-Maf. Increasing concentrations of TGF-β in lamina propria mononuclear cell cultures significantly depleted Th22 cells, whereas anti-TGF-β antibodies increased IL-22 production. When mucosal microbiota was examined, depletion of Th22 cells in actively inflamed tissue was associated with reduced populations of Clostridiales and increased populations of Proteobacteria. These results suggest that increased TGF-β during active inflammation in UC may lead to the loss of Th22 cells in the human intestinal mucosa.

The effect of antigen targeting sequences on antibody responses to hepatitis E virus DNA vaccines in rats and sheep

Expression of the capsid (PORF2) protein of hepatitis E virus (HEV) in mammalian cells results in heterogeneous intracellular processing with a mixture of stable and rapidly degraded forms, which might be expected to influence immune responses to DNA immunisation. Plasmids encoding the N-terminal 22 or 50 amino acids of PORF2 (Sig1 or Sig3, respectively) fused at the N-terminus of the ORF2.1 antigen of HEV (amino acids 394-660 of PORF2) were examined for processing in vitro and antibody responses in vivo, in both rats and sheep. Unmodified ORF2.1 is an unstable cytosolic protein and Sig1-ORF2.1 is a stable membrane-associated protein, whereas Sig3-ORF2.1 demonstrated heterogeneous processing analogous to that of full-length PORF2. After DNA immunisation, Sig1-ORF2.1 demonstrated a 30-fold enhancement of antibody responses in rats compared to untargeted ORF2.1, increasing to more than 200-fold after boosting with recombinant protein, but was ineffective in sheep. In contrast, Sig3-ORF2.1 did not give a significant effect in rats, but demonstrated 4-5-fold enhancement of antibody responses in sheep, and this enhancement was maintained after boosting with recombinant protein. These results suggest that Sig3 in particular may have promise as a targeting molecule for DNA vaccines in large animals.

Soluble expression of a functionally active Plasmodium falciparum falcipain-2 fused to maltose-binding protein in Escherichia coli

Falcipain-2 (fp2) is a hemoglobinase required for supplying peptides and amino acids for the proliferation of Plasmodium falciparum in blood. The prospect of circumventing its activity thereby serves as a potential strategy for mining drugs for anti-malarial therapy. However, to date, efforts to express soluble and active fp2 in Escherichia coli have been futile. To overcome this problem, fp2 was expressed under an array of conditions including the exploitation of multiple gene constructs in eukaryotic and prokaryotic hosts. A series of experiments led to the finding that the placement of maltose-binding protein (MBP) before the fp2 mature domain was best in availing the soluble expression of the protease. The results also indicate that the prodomain impaired the bacterial expression of the protease and the amino acid residues at the N-terminal segment of mature fp2 can have a significant effect on the folding and solubility of the enzyme. The overexpressed MBP-fp2 fusion protein was purified and shown to be functionally active, providing a very useful alternative to the use of resolubilized enzyme for future study of structure and function of fp2.

Thermostable malate synthase of Streptomyces thermovulgaris

The gene, encoding malate synthase (MS), aceB, was cloned from the thermophilic bacterium Streptomyces thermovulgaris by homology-based PCR. The 1,626-bp cloned fragment encodes a protein consisting of 541 amino acids. S. thermovulgaris malate synthase (stMS) gene was over-expressed in Escherichia coli using a glutathione-S transferase (GST) fusion vector (pGEX-6P-1), purified by affinity chromatography, and subsequently cleaved from its GST fusion partner. The purified stMS was characterized and compared to a mesophilic malate synthase (scMS) from Streptomyces coelicolor. stMS exhibited higher temperature optima (40-60 degrees C) than those of scMS (28-37 degrees C). It was more thermostable and very resistant to the chemical denaturant urea. Amino acid sequence comparison of stMS with four mesophilic streptomycete MSs indicated that they share 70.9-91.4% amino acid identities, with stMS possessing slightly more charged residues (approximately 31%) than its mesophilic counterparts (approximately 28-29%). Seven charged residues (E85, R187, R209, H239, H364, R382 and K520) that were unique to stMS may be selectively and strategically placed to support its peculiar characteristics.

Purification and characterization of recombinant malate synthase enzymes from Streptomyces coelicolor A3(2) and S. clavuligerus NRRL3585

Malate synthases (MS) from Streptomyces coelicolor A3(2) and S. clavuligerus NRRL3585 were cloned by polymerase chain reaction into a glutathione S-transferase (GST) fusion expression vector and heterologously expressed in Escherichia coli. The fusion GST-MS construct improved the soluble expression of MS by approximately 10-fold compared to the soluble expression of nonfusion MS. With the significant improvement in levels of soluble MS, purification and subsequent cleavage of recombinant MS from GST were facilitated in this study. Using purified enzymes, optimized parameters, which achieved maximal specific activity, were established in the enzymatic assay for streptomycete MS. The average purified specific activities of S. coelicolor and S. clavuligerus MS were 26199 and 11821 nmol/mg min, respectively. Furthermore, enzymatic analysis revealed that the two streptomycete MS displayed a similar Km value for acetyl-CoA, but S. coelicolor MS had a Km value for glyoxylate that is approximately sixfold higher than S. clavuligerus MS.

Molecular cloning and functional characterisation of VanX, a D-alanyl-D-alanine dipeptidase from Streptomyces coelicolor A3(2)

The vanX gene which encodes a D-alanyl-D-alanine dipeptidase is critical for vancomycin resistance in enterococci. A putative vanX gene from Streptomyces coelicolor A3(2), which is not known for vancomycin production, was identified by homology-based analysis and cloned by polymerase chain reaction. The S. coelicolor vanX gene was heterologously expressed in Escherichia coli BL21(DE3) and enzymatic assays of soluble protein fractions of VanX revealed a 93-fold increase in dipeptidase activity as compared to the nonrecombinant control, thus confirming its functionality. Interestingly, S. coelicolor was also found to be of intermediate resistance to vancomycin although it does not produce vancomycin, thus suggesting the role of VanX in defence or immunity. As such, the prevalence of vanX genes in the environment may be more common than previously thought.

Cloning, heterologous expression and purification of an isocitrate lyase from Streptomyces clavuligerus NRRL 3585

The glyoxylate cycle comprising isocitrate lyase (ICL) and malate synthase (MS) is an anaplerotic pathway essential for growth on acetate as the sole carbon source. The aceB gene, which encodes malate synthase has been previously cloned from Streptomyces clavuligerus NRRL 3585 and characterized. In this study, the aceA gene, encoding ICL from S. clavuligerus NRRL 3585, was obtained via genome walking experiments and PCR. The fully sequenced open reading frame encodes 436 amino acids with a deduced M(r) of 47.5 kDa, consistent with the observed M(r) (49-67.5 kDa) of most ICL enzymes reported so far. The cloned aceA gene was expressed in Escherichia coli BL21(lambdaDE3) cells, from which ICL was purified as a His-tagged product and its functionality demonstrated. Furthermore, the relationship between the carbon sources, growth and ICL activity in S. clavuligerus were investigated. Rapid growth was observed when the cells were cultured on 0.5% (w/v) glycerol, while delayed growth was observed when cells were grown on 0.5% (w/v) acetate. However, in both cases, high levels of ICL activity coincided with a cessation of growth, suggesting a late physiological role played by ICL in the natural host, S. clavuligerus.

A Brugia malayi homolog of macrophage migration inhibitory factor reveals an important link between macrophages and eosinophil recruitment during nematode infection

Infections with the helminth parasite Brugia malayi share many key features with Th2-mediated allergic diseases, including recruitment of eosinophils. We have investigated the dynamics of inflammatory cell recruitment under type 2 cytokine conditions in mice infected with B. malayi. Among the cells recruited to the site of infection is a novel population of "alternatively activated" macrophages that ablate cell proliferation and enhance Th2 differentiation. By profiling gene expression in this macrophage population, we found a dramatic up-regulation of a recently described eosinophil chemotactic factor, eosinophil chemotactic factor-L/Ym1, representing over 9% of clones randomly selected from a cDNA library. Because B. malayi is known to secrete homologs (Bm macrophage migration inhibitory factor (MIF)-1 and -2) of the human cytokine MIF, we chose to investigate the role this cytokine mimic may play in the development of the novel macrophage phenotype observed during infection. Strikingly, administration of soluble recombinant Bm-MIF-1 was able to reproduce the effects of live parasites, leading both to the up-regulation of Ym1 by macrophages and a marked recruitment of eosinophils in vivo. Because activity of Bm-MIF-1 is dependent upon an amino-terminal proline, this residue was mutated to glycine; the resultant recombinant (Bm-MIF-1G) was unable to induce Ym1 transcription in macrophages or to mediate the recruitment of eosinophils. These data suggest that macrophages may provide a crucial link between helminth parasites, their active cytokine mimics, and the recruitment of eosinophils in infection.

Mutational analysis of conserved glycines 42 and 256 in Cephalosporium acremonium isopenicillin N synthase

Isopenicillin N synthase (IPNS) is critical for the catalytic conversion of delta-(L-alpha-aminoadipoyl)-L-cysteinyl-D-valine to isopenicillin N in the penicillin and cephalosporin biosynthetic pathway. Two conserved glycine residues in Cephalosporium acremonium IPNS (cIPNS), namely glycine-42 and glycine-256, were identified by multiple sequence alignment and investigated by site-directed mutagenesis to study the effect of the substitution on catalysis. Our study showed that both the mutations from glycine to alanine or to serine reduced the catalytic activity of cIPNS and affected its soluble expression in a heterologous host at 37 degrees C. Soluble expression was restored at a reduced temperature of 25 degrees C, and thus, it is possible that these glycine residues may have a role in maintaining the local protein structure and are critical for the soluble expression of cIPNS.

Replacement of arginine-171 and aspartate-453 in Streptomyces coelicolor malate synthase A by site-directed mutagenesis inactivates the enzyme

Malate synthase, a key enzyme of the glyoxylate cycle, catalyzes the condensation of glyoxylate and acetyl-CoA to yield malate and CoA. Escherichia coli is known to possess two forms of malate synthase, A and G respectively. The recent elucidation of the E. coli malate synthase G crystal structure suggested two residues, Arg338 and Asp631, are essential for catalysis. Multiple sequence alignment of 26 known malate synthase enzymes revealed that the two proposed sites are highly conserved, despite the low homologies between the two distinct forms of the enzyme (13-18%). The conservation of these residues in both forms of malate synthase suggests that they possess a similar catalytic strategy. Thus, despite the absence of a three-dimensional structure for malate synthase A, the significance of this enzyme in the primary metabolic pathway has prompted the investigation of the involvement of the corresponding residues, Arg171 and Asp453, in Streptomyces coelicolor malate synthase A by site-directed mutagenesis. Heterologous expression in E. coli followed by purification of the constructed mutant proteins, Arg171Leu and Asp453Ala, were performed and subsequent enzyme assays of the purified mutant proteins indicated a significant loss of catalytic activity, thus attesting to the need for the corresponding conserved residues to maintain malate synthase functionality.

A comparison of three site-directed mutagenesis kits

In this comparative study, three different mutagenesis kits, namely the MutaGene phagemid in vitro mutagenesis kit (Bio-Rad), the Transformerä Site-Directed mutagenesis kit (Clontech) and the Quik-change site-directed mutagenesis kit (Stratagene) were used for the mutagenesis of IPNS genes. However, a large difference in mutation efficiencies among these kits was encountered. Furthermore, these kits employ different strategies with its own individual strengths and weaknesses. Thus, a comparison among these three kits to evaluate their usefulness and improvements on the strategy adopted by the Quik-change site-directed mutagenesis kit, which was the kit of choice for our work, are presented for the benefit of research work.

Cloning and sequence characterisation of falcipain-2 from Plasmodium falciparum Gombak A strain (Malaysia)

In this study, the genome of the Plasmodium falciparum Gombak A strain was examined for the presence of a gene encoding falcipain-2, a cysteine protease, using homology-based polymerase chain reaction cloning. The nucleotide sequence obtained from the gene cloned (designated pFG1) is approximately 99% homologous to other falcipain-2 genes from different strains. Comparatively, it is 69% homologous to falcipain-3 genes. Direct cloning of the falcipain-2 gene and its resemblance to the reported corresponding mRNA transcript suggests the absence of introns in this gene. Sequence alignment and comparison revealed four amino acid differences at positions 15, 51, 59 and 414 in the falcipain-2 from P. falciparum Gombak A as compared to other falcipain-2 proteins from different strains.

Replacement of tyrosine-197 and the corresponding tyrosine-195 to isoleucine in Cephalosporium acremonium and Streptomyces clavuligerus isopenicillin N synthase

Isopenicillin N synthase (IPNS) is one of the key enzymes in the penicillin and cephalosporin biosynthetic pathway which catalyses the conversion of delta-(L-alpha-aminoadipyl)-L-cysteinyl-D-valine to isopenicillin N. The IPNS from Penicillium chrysogenum 23X-80-269-37-2, a high penicillin V-producer, was found to possess an isoleucine residue instead of tyrosine at position 195. An attempt to increase the specific activity of IPNS from Cephalosporium acremonium and Streptomyces clavuligerus was undertaken by altering the corresponding tyrosine residue to an isoleucine at the corresponding location. Unfortunately, no apparent increase in specific activity was encountered when the purified mutant enzymes were analysed and thus, this amino acid difference is likely not responsible for high specific activity in IPNS.

Divergent roles for macrophages in lymphatic filariasis

Macrophages have long been recognized as important cells associated with filarial infection but their function as effectors and/or suppressors has not been elucidated. Recent advances in our understanding of the role that macrophages may play in lymphatic filariasis have come from in vitro studies and mouse models of filarial infection. Based on these new findings, we hypothesize that while dead or dying worms induce the 'classical' activation of macrophages and a subsequent pro-inflammatory response, live and healthy worms secrete products that induce type 2 cytokines and the differentiation of 'alternatively' activated macrophages that downregulate an inflammatory response. Thus, the balance between the 'classical' and 'alternative' activation pathways of macrophages could be an important factor in inflammatory pathology associated with filariasis.

Site-directed mutagenesis of proline-285 to leucine in Cephalosporium acremonium isopenicillin-N-synthase affects catalysis and increases soluble expression at higher temperatures

The conversion of delta-(L-alpha-aminoadipyl)-L-cysteinyl-D-valine (ACV) to isopenicillin N is dependant on the catalytic action of isopenicillin N-synthase (IPNS), an important enzyme in the penicillin and cephalosporin biosynthetic pathway. One of the amino acid residues suggested by the Aspergillus nidulans IPNS crystal structure for interaction with the valine isopropyl group of ACV is proline-283. Site-directed mutagenesis of the corresponding proline-285 to leucine in Cephalosporium acremonium IPNS resulted in non-measurable activity but an increased soluble expression at higher temperatures in a heterologous E. coli host.

Alternatively activated macrophages induced by nematode infection inhibit proliferation via cell-to-cell contact

The cytokine microenvironment is thought to play an important role in the generation of immunoregulatory cells. Nematode infections are commonly associated with Th2 cytokines and hyporesponsive T cells. Here we show that IL-4-dependent macrophages recruited in vivo by the nematode parasite Brugia malayi actively suppress the proliferation of lymphocytes on co-culture in vitro. These alternatively activated macrophages block proliferation by cell-to-cell contact, implicating a receptor-mediated mechanism. Further, the proliferative block is reversible and is not a result of apoptosis. Suppressed cells accumulate in the G1 and G2/M phase of the cell cycle. Interestingly, the G1 and G2/M block correlates with increased levels of Ki-67 protein, suggesting a mechanism that affects degradation of cell cycle proteins. We also show that, in addition to lymphocyte cell lines of murine origin, these suppressive cells can inhibit proliferation of a wide range of transformed human carcinoma lines. Our data reveal a novel mechanism of proliferative suppression induced by a parasitic nematode that acts via IL-4-dependent macrophages. These macrophages may function as important immune regulatory cells in both infectious and noninfectious disease contexts.

Molecular cloning, heterologous expression, and functional characterisation of a malate synthase gene from Streptomyces coelicolor A3(2)

With the rapid generation of genetic information from the Streptomyces coelicolor genome project, deciphering the relevant gene products is critical for understanding the genetics of this model streptomycete. A putative malate synthase gene (aceB) from S. coelicolor A3(2) was identified by homology-based analysis, cloned by polymerase chain reaction, and fully sequenced on both strands. The putative malate synthase from S. coelicolor has an amino acid identity of 77% with the malate synthase of S. clavuligerus, and possesses an open reading frame which codes for a protein of 540 amino acids. In order to establish the identity of this gene, the putative aceB clones were subcloned into the expression vector pET24a, and heterologously expressed in Escherichia coli BL21(DE3). Soluble cell-free extracts containing the recombinant putative malate synthase exhibited a specific activity of 1623 (nmol.mg-1.min-1), which is an increment of 92-fold compared to the non-recombinant control. Thus, the gene product was confirmed to be a malate synthase. Interestingly, the specific activity of S. coelicolor malate synthase was found to be almost 8-fold higher than the specific activity of S. clavuligerus malate synthase under similar expression conditions. Furthermore, the genomic organisation of the three Streptomyces aceB genes cloned thus far is different from that of other bacterial malate synthases, and warrants further investigation.

Molecular cloning, heterologous expression, and functional characterisation of a malate synthase gene fromStreptomyces coelicolorA3(2)

With the rapid generation of genetic information from the Streptomyces coelicolor genome project, deciphering the relevant gene products is critical for understanding the genetics of this model streptomycete. A putative malate synthase gene (aceB) from S. coelicolor A3(2) was identified by homology-based analysis, cloned by polymerase chain reaction, and fully sequenced on both strands. The putative malate synthase from S. coelicolor has an amino acid identity of 77% with the malate synthase of S. clavuligerus, and possesses an open reading frame which codes for a protein of 540 amino acids. In order to establish the identity of this gene, the putative aceB clones were subcloned into the expression vector pET24a, and heterologously expressed in Escherichia coli BL21(DE3). Soluble cell-free extracts containing the recombinant putative malate synthase exhibited a specific activity of 1623 (nmol·mg-1·min-1), which is an increment of 92-fold compared to the non-recombinant control. Thus, the gene product was confirmed to be a malate synthase. Interestingly, the specific activity of S. coelicolor malate synthase was found to be almost 8-fold higher than the specific activity of S. clavuligerus malate synthase under similar expression conditions. Furthermore, the genomic organisation of the three Streptomyces aceB genes cloned thus far is different from that of other bacterial malate synthases, and warrants further investigation.Key words: primary metabolism, polymerase chain reaction, glyoxylate pathway.

Molecular studies on isopenicillin N synthases

The isopenicillin N synthases isolated thus far are related to oxidases from other microorganisms and plants. These enzymes maintain a non-heme monoferrous-dependent catalytic centre comprising a HisXAsp(53-57)XHis motif and a crucial substrate-binding pocket with an ArgXSer motif for their functionality. The elucidation of these motifs was dependent on information collated from studies on structural chemistry, structural biology, site-directed engineered mutations and biochemical experiments. It is envisaged that these enzymes can potentially be improved through molecular breeding and protein engineering.

Suppressive antigen-presenting cells in Helminth infection

Infection with filarial nematodes is commonly associated with a failure of T cells to proliferate in response to parasite antigen. We have investigated the possibility that antigen-presenting cells recruited during filarial infection are responsible for impairment of T cell function. We have found that the human filarial parasite Brugia malayi, when implanted into the peritoneal cavity of mice, recruits a population of adherent cells that actively block the proliferation of T cells. Phenotypic analysis of the recruited cells reveals large numbers of both macrophages and eosinophils and cell sorting experiments demonstrate that these antiproliferative cells are Mac-1-positive. Studies in gene-deficient mice have demonstrated that proliferative suppression is dependent on the in vivo production of IL-4 but not IL-5 or IL-10, while suppression in vitro is not mediated by any known antiproliferative factor. Our results suggest that helminth infection can lead to the development and/or recruitment of an IL-4-dependent macrophage population that mediates suppression via a novel mechanism.

Interleukin-5 is essential for vaccine-mediated immunity but not innate resistance to a filarial parasite

The study of protective immune mechanisms effective against filarial nematodes has been hampered by the inability of these important human pathogens to infect laboratory mice. Recently, Litomosoides sigmodontis, a natural parasite of rats, has been developed as a valuable model for the study of filarial infection. BALB/c mice are fully susceptible to infection with L. sigmodontis third-stage larvae and develop patent infection. In contrast, mice on the C57BL background are resistant, and parasites undergo only a single molt and do not mature to adulthood. We used interleukin-5 (IL-5)-deficient mice on the C57BL/6 background to address the role of IL-5 and eosinophils in the innate resistance of C57BL/6 mice. We found no differences in parasite survival between IL-5-deficient and C57BL/6 mice. However, when these mice were used for the analysis of vaccine-mediated immunity, a critical role for IL-5 was elucidated. Mice genetically deficient in IL-5 were unable to generate a protective immune response when vaccinated with irradiated larvae, whereas C57BL/6 mice were fully protected from challenge infection. These studies help to clarify the highly controversial role of eosinophils in filarial infection.