Activity Description: 
During the last decade, there has been a major change in our understanding of the pathogenesis of wheezing lower respiratory illnesses (WLRI) in early childhood, which are often the first manifestations of asthma. Until recently, these illnesses were considered to be due to viral infections, and bacteria were thought to have no role in their etiology. New data suggest that children who have recurrent WLRI have an alteration in the composition of the bacterial communities that inhabit their gut and their airways. It has been shown, for example, that the airways of these children are more likely to be colonized with pathogenic bacteria such as H influenzae, M catarrhalis, or S pneumonia, and these 3 species are more often isolated from the nasopharynx of children having an acute WLRI than from unaffected children.  A potential explanation for these findings is a modification of the so-called hygiene hypothesis. In its current form, this hypothesis postulates that the developing immune system needs to be trained by progressive exposure to environmental microbes in order to develop the capacity to distinguish friend from foe. In the absence of such training, the normal balance between commensal bacteria and local immune responses fails to develop, and this imbalance, called dysbiosis, predisposes the young child to overact to viral infections and allergen exposures, both of which are major triggers of early wheezing and predisposing factors for the development of asthma.  

During this session, clinicians will learn about the basics of the Hygiene Hypothesis, and how measures to modify a child’s environmental exposures might change the course of their “allergic march.”

Learning Objectives:  

1. Understand and describe the basics of the “hygiene hypothesis.”  
2. Discuss how measures to modify a child’s environmental exposures might change the course of their “allergic march.” 
3. Describe current research being conducted to evaluate the safety and efficacy of new biologics that could change a child’s Th1/Th2 immunologic development by conditioning the body to pathogenic bacteria and the potential mechanism underlying the use of these products.