McMaster University’s Schroeder Allergy and Immunology Research Institute (SAIRI) is supporting the world-leading allergy research of the CHILD Cohort Study (CHILD), now led by asthma and allergy clinician scientist Padmaja Subbarao.

CHILD is investigating the genetic and environmental determinants of atopic diseases including asthma, allergy, allergic rhinitis (or hay fever), and eczema. As the largest multidisciplinary, longitudinal, population-based birth cohort study in Canada, which began at McMaster in 2008, it is designed to be one of the most informative studies of its kind in the world.

CHILD has four research sites in Toronto, Winnipeg and environs, Edmonton and Vancouver. Its national headquarters is hosted by McMaster University, now under the auspices of SAIRI.

“SAIRI’s focus on allergy and immunology resonates with CHILD’s core pursuit of discovery in allergy, but the Institute’s support will also facilitate our broader promotion of precision health for Canadian children,” said Subbarao, who is director of CHILD and adjunct clinical professor of medicine at McMaster.

Padmaja Subbarao, director of CHILD and adjunct clinical professor of medicine
Padmaja Subbarao, director of CHILD and adjunct clinical professor of medicine


She holds the Canada Research Chair in Pediatric Asthma and Lung Health, and she is a professor of the Dalla Lana School of Public Health at the University of Toronto.

After the CHILD study was launched by now-professor emeritus Malcolm Sears, more than 3,500 pregnant mothers were recruited to participate, with their children born between 2009 and 2012. As a longitudinal study, CHILD has been gathering data and biological samples from the participating children and their families at specific points throughout their childhood and now into their teen years.

The data collected by CHILD includes information on childhood health and nutrition, family histories of allergies, and the results of clinical tests for such things as allergic sensitivity and lung health. Biological samples collected include dust from house inspections, breast milk, blood, urine, baby teeth and stools.

CHILD has generated numerous significant scientific insights into the developmental origins of asthma, allergy, and other diseases, including obesity and diabetes.

Subbarao said that as CHILD participants enter adolescence, the clinical focus of the study has further expanded to include neurodevelopment, and outcomes such as chronic obstructive disease and cardiovascular and metabolic disorders.

She said the insights gleaned from CHILD data will influence medical practice, parenting choices, consumer product regulation and policy development. This includes building codes, household purchasing behaviours, decisions about childbirth and delivery, diet, breastfeeding, home cleaning products, owning a pet and managing stress.

“With what we are learning through CHILD, in future we will be able to assess a child’s allergy risk at an individual level and tailor a preventative strategy to their individual circumstances, taking into account not only their physical and social environment, but their genetic make-up and biological information like the composition of their microbiome,” said Subbarao.

“CHILD was one of the first studies that really drilled into the gut microbiome, and with SAIRI’s support, our ongoing microbiome research will allow clinicians to discover ‘prevention windows’ for childhood allergies and intervene to stop them.”

The human microbiome is the community of microorganisms (such as bacteria, fungi, and viruses) that live in or on the human body. Thanks to the stool samples the study has collected form its participants since birth, CHILD has fueled numerous discoveries about the relationship of the gut microbiome—the microorganisms living in the digestive tract—to illness and health, she said.

Subbarao said that the gut microbiome, which helps prime the immune system to fight pathogens, plays a crucial role in childhood allergies and asthma. CHILD research has shown that various factors effect the composition of a child’s gut microbiome, and that these differences in the microbiome, in turn, influence a child’s risk of developing allergies or asthma. A depleted or dysfunctional microbiome can prime the immune system to react to allergens such as pollen or nuts, she said.

CHILD has found, for example, that a child’s gut microbiome is impacted by whether that child is born vaginally or by c-section, or whether that child is breastfed, or if that child is exposed to antibiotics, or even if there are furry pets or a high use of household cleansers in that child’s home.

CHILD research has also shown that specific gut bacteria play a critical role in protecting against asthma. To build on this finding, CHILD researchers received a major Canadian Institutes of Health Research (CIHR) grant to further investigate this relationship and replicate it in animal models.

“If you can replicate the infant microbiome and prevent the asthma trajectory in an animal model, you can then identify the triggers and develop preventative therapies for infants,” said Subbarao.

Other CHILD research has provided new clinical approaches to preventing asthma: CHILD has found that reducing the amount of antibiotics prescribed to babies under six months is stabilizing asthma rates, and that breastfeeding straight from the breast better protects against asthma than bottle-feeding.

“We have successfully moved the dial on this disease,” said Subbarao.

CHILD research, now with SAIRI’s support, is looking to reveal similar windows of opportunity when it comes to preventing the development of food allergy.

CHILD research has already confirmed, for example, that the early introduction of potentially allergenic foods, such as peanut and egg, has a protective effect. CHILD also found that the ‘triple exposure’ strategy of breastfeeding, maternal peanut consumption and feeding babies nuts before their first birthday may reduce a child’s nut allergy risk by age five.

According to CHILD research, other factors that may be driving up food allergy rates include air pollution, maternal depression and whether babies are delivered by caesarean section, Subbarao said.

“Every child has a unique set of genetic and environmental ‘drivers’ that influence allergy development,” she said.

“Understanding a child’s individual set of allergic triggers will allow clinicians to tailor interventions accordingly, and CHILD is helping to identify what those triggers are. This is the work that SAIRI is helping to advance.

“We are still at the very early stage of discovery and expect to unlock new therapeutic windows for more allergies as well as for other chronic, non-communicable diseases,” she added.

“It is an exciting time for allergy research and there is so much potential. We have only exposed the tip of the iceberg. With SAIRI’s support, however, CHILD will help uncover the whole thing.”





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