Early Oral Ovalbumin Exposure during Maternal Milk Feeding Prevents Spontaneous Allergic Sensitization in Allergy-Prone Rat Pups

There are conflicting data to support the practice of delaying the introduction of allergenic foods into the infant diet to prevent allergy development. This study investigated immune response development after early oral egg antigen (Ovalbumin; OVA) exposure in a rat pup model. Brown Norway (BN) rat pups were randomly allocated into groups: dam reared (DR), DR pups challenged daily (days 4–13) with oral OVA (DR + OVAc), DR pups challenged intermittently (on day 4, 10, 12, and 13) with oral OVA (DR + OVAi), formula-fed pups (FF), and FF pups challenged daily with oral OVA (FF + OVA). Immune parameters assessed included OVA-specific serum IgE, IgG1, and IgA. Ileal and splenic messenger ribonucleic acid (mRNA) expression of transforming growth factor-beta (TGF-β1), mothers against decapentaplegic (Smad) 2/4/7, and forkhead box P3 (Foxp3) were determined. Ileum was stained for TGF-β1 and Smad4. Results. Feeding OVA daily to DR pups maintained systemic and local gut antibody and immunoregulatory marker mRNA responses. Systemic TGF-β1 was lower in DR + OVAi pups compared to DR and DR + OVAc pups. Feeding OVA to FF pups resulted in significantly greater OVA-specific IgE and IgG1, and lower IgA and TGF-β1 and Smad expression compared to DR pups. Conclusions. Early daily OVA exposure in the presence of maternal milk maintains immune markers associated with a regulated immune response, preventing early allergic sensitization

Randomised controlled trial of a baked egg intervention in young children allergic to raw egg but not baked egg

Consumption of baked egg by raw egg allergic children is associated with immune changes suggesting development of tolerance. However, causation has not been tested using a double blind randomized controlled trial (RCT). We aimed to compare clinical and immunological outcomes after baked egg (BE) consumption in young BE tolerant egg allergic children.In a double blind RCT, BE tolerant egg allergic children consumed 10 g BE (1.3 g protein) 2 to 3 times per week for 6 months (n = 21 intervention group) or similar egg free baked goods (n = 22 control group) while maintaining an otherwise egg free diet. The final assessment was a raw egg oral food challenge (OFC) 1 month after ceasing the intervention product. Egg specific IgE and IgG4 were assessed at baseline and 7 months.After the intervention there was no difference in raw egg tolerance between groups, (23.5% (4/17) intervention group and 33.3% (6/18) control group). This was independent of age and amount of BE consumed (aOR 0.50 CI 0.11-2.40 p = 0.39). Both groups demonstrated decreased egg specific serum IgE titres and decreased whole egg specific IgE/IgG4 ratios.We conducted this trial because inclusion of baked egg protein in the diet of egg allergic children appears to move children towards a more tolerant immune profile. Strengths of our study include design of the blinded intervention, the consistent dosing protocol and the regular monitoring of symptoms and intake. However, the study was limited by small sample size resulting in insufficient power to show statistically significant results.Our study suggests that short term, regular consumption of BE by BE tolerant 1 to 5 year old children with IgE mediated raw egg allergy may not induce, accelerate or slow development of tolerance to raw egg in this selected population. Trials with larger sample sizes are required to further test this hypothesis.The trial was registered on 7th February 2012 with the Australian New Zealand Clinical Trials Registry (ACTRN 12612000173897).Merryn Netting, Michael Gold, Patrick Quinn, Adaweyah El-Merhibi, Irmeli Penttila and Maria Makride

Heated allergens and induction of tolerance in food allergic children

Food allergies are one of the first manifestations of allergic disease and have been shown to significantly impact on general health perception, parental emotional distress and family activities. It is estimated that in the Western world, almost one in ten children have an IgE-mediated allergy. Cow’s milk and egg allergy are common childhood allergies. Until recently, children with food allergy were advised to avoid all dietary exposure to the allergen to which they were sensitive, in the thought that consumption would exacerbate their allergy. However, recent publications indicate that up to 70% of children with egg allergy can tolerate egg baked in a cake or muffin without apparent reaction. Likewise, up to 75% of children can tolerate baked goods containing cow’s milk, and these children demonstrate IgE and IgG4 profiles indicative of tolerance development. This article will review the current literature regarding the use of heated food allergens as immunotherapy for children with cow’s milk and egg allergy.Merryn Netting, Maria Makrides, Michael Gold, Patrick Quinn and Irmeli Penttil

Hepatic cytochrome P450 enzymes belonging to the CYP2C subfamily from an Australian marsupial, the koala (Phascolarctos cinereus)

Cytochromes P450 (CYPs) are critically important in the oxidative metabolism of a diverse array of xenobiotics and endogenous substrates. We have previously reported that the obligate Eucalyptus feeder koala (Phascolarctos cinereus) exhibits a higher hepatic CYP2C activity as compared to non-Eucalyptus feeders human or rat, with stimulation of CYP2C activity by cineole. In the present study, we examine CYP2C expression by immunohistochemistry and describe the identification and cloning of koala CYP2Cs. Utilising anti-rat CYP2C6 antibody, the expression of CYP2C was found to be uniform across the hepatic sections, being consistent with that observed in human and rat. Two 1647 and 1638 bp koala liver CYP2C complete cDNAs, designated CYP2C47 and CYP2C48 respectively, were cloned by cDNA library screening. The koala CYP2C cDNAs encode a protein of 495 amino acids. Three additional partial CYP2C sequences were also identified from the koala, indicating the multiplicity of the CYP2C subfamily in this unique marsupial species. The results of this study demonstrate the presence of koala hepatic CYP2Cs that share several common features with other published CYP2Cs; however CYP2C47 and CYP2C48 contain four extra amino acid residues at the NH2-terminal, a transmembrane anchor which was reported being a fundamentally conserved structure core of all eukaryote CYP enzymes.Brett R. Jones, Adaweyah El-Merhibi, Suong N.T. Ngo, Ieva Stupans, Ross A. McKinno

Molecular insights into xenobiotic disposition in Australian marsupials

During the past two decades, studies of xenobiotic detoxification by molecular biology in diverse organisms have identified many novel environmental adaptations, providing valuable insight into habitat, dietary preferences and general physiology. While xenobiotic detoxification has been extensively studied in eutherian mammals, metabolic data concerning detoxification in Australian marsupials are limited, particularly at the molecular level of the enzymes involved. At present Australia relies heavily on overseas data to determine the possible outcomes of xenobiotic exposure in Australian native fauna. Unlike eutherian mammals, many marsupial herbivores ingest and absorb large amounts of dietary Eucalyptus terpenes. Such quantities would be toxic, even potentially fatal, to human and many other mammalian species. Specialist Eucalyptus herbivores, such as koalas and brushtail possums, have been hypothesised to utilise highly efficient enzyme systems to metabolise terpenes to non-toxic substances that can be readily excreted in the urine. Enzymes that carry out the biotransformation of Eucalyptus terpenes have been partially identified to be the cytochromes P450 (CYP). The aim of this review is to provide a summary of work being undertaken over several years in our laboratories that has provided unique insights into marsupial biology. The focuses of this study are phase I and phase II metabolisms in these unique animals, the multiplicity of metabolising enzymes/pathways involved, induction/inhibition of CYPs/other enzymes by dietary Eucalyptus terpenes and to update current knowledge of xenobiotic metabolism in Australian marsupials. The important role of marsupial genome studies in identifying evolutionary relationships and functions for mammalian genes as well as in conservation, ecology and pest management of marsupial species is also briefly highlighted

Cytochrome P450 CYP3A in marsupials: Cloning and characterisation of the second identified CYP3A subfamily member, isoform 3A78 from koala (Phascolarctos cinereus)

Cytochromes P450 (CYPs) are critically important in the oxidative metabolism of a diverse array of xenobiotics and endogenous substrates. Previously, we cloned and characterised the CYP2C, CYP4A, and CYP4B gene subfamilies from marsupials and demonstrated important species-differences in both activity and tissue expression of these CYP enzymes. Recently, we isolated the Eastern grey kangaroo CYP3A70. Here we have cloned and characterised the second identified member of marsupial CYP3A gene subfamily, CYP3A78 from the koala (Phascolarctos cinereus). In addition, we have examined the gender-differences in microsomal erythromycin N-demethylation activity (a CYP3A marker) and CYP3A protein expression across test marsupial species. Significant differences in hepatic erythromycin N-demethylation activity were observed between male and female koalas, with the activity detected in female koalas being 2.5-fold higher compared to that in male koalas (p<0.01). No gender-differences were observed in tammar wallaby or Eastern grey kangaroo. Immunoblot analysis utilising anti-human CYP3A4 antibody detected immunoreactive proteins in liver microsomes from all test male and female marsupials including the koala, tammar wallaby, and Eastern grey kangaroo, with no gender-differences detected across test marsupials. A 1610 bp koala hepatic CYP3A complete cDNA, designated CYP3A78, was cloned by reverse transcription-polymerase chain reaction approaches. It displays 64% nucleotide and 57% amino acid sequence identity to the Eastern grey kangaroo CYP3A70. The CYP3A78 cDNA encodes a protein of 515 amino acids, shares approximately 68% nucleotide and 56% amino acid sequence identity to human CYP3A4, and displays high sequence similarity to other published mammalian CYP3As from human, monkey, cow, pig, dog, rat, rabbit, mouse, hamster, and guinea pig. Collectively, this study provides primary molecular data regarding koala hepatic CYP3A78 gene and enables further functional analyses of CYP3A enzymes in marsupials. Given the significant role that CYP3A enzymes play in the metabolism of both endogenous and exogenous compounds, the clone provides an important step in elucidating the metabolic capacity of marsupials.Adaweyah El-Merhibi, Suong N.T. Ngo, Tamara A. Crittenden, Ceilidh L. Marchant, Ieva Stupans and Ross A. McKinnonhttp://www.journals.elsevier.com/comparative-biochemistry-and-physiology-part-c-toxicology-and-pharmacology

Molecular insights into xenobiotic disposition in Australian marsupials

During the past two decades, studies of xenobiotic detoxification by molecular biology in diverse organisms have identified many novel environmental adaptations, providing valuable insight into habitat, dietary preferences and general physiology. While xenobiotic detoxification has been extensively studied in eutherian mammals, metabolic data concerning detoxification in Australian marsupials are limited, particularly at the molecular level of the enzymes involved. At present Australia relies heavily on overseas data to determine the possible outcomes of xenobiotic exposure in Australian native fauna. Unlike eutherian mammals, many marsupial herbivores ingest and absorb large amounts of dietary Eucalyptus terpenes. Such quantities would be toxic, even potentially fatal, to human and many other mammalian species. Specialist Eucalyptus herbivores, such as koalas and brushtail possums, have been hypothesised to utilise highly efficient enzyme systems to metabolise terpenes to non-toxic substances that can be readily excreted in the urine. Enzymes that carry out the biotransformation of Eucalyptus terpenes have been partially identified to be the cytochromes P450 (CYP). The aim of this review is to provide a summary of work being undertaken over several years in our laboratories that has provided unique insights into marsupial biology. The focuses of this study are phase I and phase II metabolisms in these unique animals, the multiplicity of metabolising enzymes/pathways involved, induction/inhibition of CYPs/other enzymes by dietary Eucalyptus terpenes and to update current knowledge of xenobiotic metabolism in Australian marsupials. The important role of marsupial genome studies in identifying evolutionary relationships and functions for mammalian genes as well as in conservation, ecology and pest management of marsupial species is also briefly highlighted.A El-Merhibi, SNT Ngo, BR Jones, NL Milic, I Stupans and RA McKinno

Hepatic cytochrome P450 enzymes belonging to the CYP2C subfamily from an Australian marsupial, the koala ('Phascolarctos cinereus')

Cytochromes P450 (CYPs) are critically important in the oxidative metabolism of a diverse array of xenobiotics and endogenous substrates. We have previously reported that the obligate 'Eucalyptus' feeder koala ('Phascolarctos cinereus') exhibits a higher hepatic CYP2C activity as compared to non-Eucalyptus feeders human or rat, with stimulation of CYP2C activity by cineole. In the present study, we examine CYP2C expression by immunohistochemistry and describe the identification and cloning of koala CYP2Cs. Utilising anti-rat CYP2C6 antibody, the expression of CYP2C was found to be uniform across the hepatic sections, being consistent with that observed in human and rat. Two 1647 and 1638 bp koala liver CYP2C complete cDNAs, designated CYP2C47 and CYP2C48 respectively, were cloned by cDNA library screening. The koala CYP2C cDNAs encode a protein of 495 amino acids. Three additional partial CYP2C sequences were also identified from the koala, indicating the multiplicity of the CYP2C subfamily in this unique marsupial species. The results of this study demonstrate the presence of koala hepatic CYP2Cs that share several common features with other published CYP2Cs; however CYP2C47 and CYP2C48 contain four extra amino acid residues at the NH2-terminal, a transmembrane anchor which was reported being a fundamentally conserved structure core of all eukaryote CYP enzymes

Cytochrome P450 CYP3A in marsupials: cloning and identification of the first CYP3A subfamily member, isoform 3A70 from Eastern gray kangaroo (Macropus giganteus)

Australian marsupials are unique fauna that have evolved and adapted to unique environments and thus it is likely that their detoxification systems differ considerably from those of well-studied eutherian mammals. Knowledge of these processes in marsupials is therefore vital to understanding the consequences of exposure to xenobiotics. Cytochromes P450 (CYPs) are critically important in the oxidative metabolism of a diverse array of both xenobiotics and endogenous substrates. In this study we have cloned and characterized CYP3A70, the first identified member of the CYP3A gene subfamily from Eastern gray kangaroo (Macropus giganteus). A 1665 base pair kangaroo hepatic CYP3A complete cDNA, designated CYP3A70, was cloned by reverse transcription-polymerase chain reaction approaches, which encodes a protein of 506 amino acids. The CYP3A70 cDNA shares approximately 71% nucleotide and 65% amino acid sequence homology to human CYP3A4 and displays high sequence similarity to other published mammalian CYP3As from human, monkey, cow, pig, dog, rat, rabbit, mouse, hamster, and guinea pig. Transfection of the CYP3A70 cDNAs into 293T cells resulted in stable cell lines expressing a CYP3A immuno-reactive protein that was recognized by a goat anti-human CYP3A4 polyclonal antibody. The anti-human CYP3A4 antibody also detected immunoreactive proteins in liver microsomes from all test marsupials, including the kangaroo, koala, wallaby, and wombat, with multiple CYP3A immunoreactive bands observed in kangaroo and wallaby tissues. Relatively, very low CYP catalytic activity was detected for the kangaroo CYP3A70 cDNA-expressed proteins (19.6 relative luminescent units/μg protein), which may be due to low protein expression levels. Collectively, this study provides primary molecular data regarding the Eastern kangaroo hepatic CYP3A70 gene and enables further functional analyses of CYP3A enzymes in marsupials.Adaweyah El-Merhibi, Suong N.T. Ngo, Ceilidh L. Marchant, Tamara A. Height, Ieva Stupans and Ross A. McKinno