Asthma in the inner city: Three Analyses of the APIC Study

Asthma is an incredibly variable disease with its impact on people and molecular and cellular mechanisms what it does to the lungs and rest of the body.  This month’s issue of JACI features three articles by Zoratti et al (J Allergy Clin Immunol 2016; 138(4): 1016-1029), Pongracic et al (J Allergy Clin Immunol 2016; 138(4): 1030-1041), and Liu et al (J Allergy Clin Immunol 2016; 138(4): 1042-1050), covering asthma among inner city children.  They examine factors that determine the phenotype, severity and disease control, based on data they obtained from the Asthma Phenotypes in the Inner City (APIC) study, which looked at children aged 6 to 17 years and examined them every 2 months for one year.  Even though their techniques are all slightly different, all three analyses determined that allergic inflammation was a very significant contributor to disease.  In addition to rhinitis, pulmonary physiology also influenced severity and ability to control asthma despite guideline-based therapy.  Body mass index and environmental tobacco exposure were also quite significant in explaining severity of and ability to control disease activity, respectively.  Interestingly, Vitamin D did not have a significant effect on the control of asthma.  Altogether, the results of the APIC study provide insights into what strategies can be implemented to bring asthma under better control in inner cities.  Identifying those who are most at risk through the results of these studies, and targeting allergic inflammation, both in the upper or the lower respiratory passages, may help to reduce the burden of asthma.

Early-life gut microbiome composition and milk allergy resolution

Allergy to cow’s milk affects roughly one in fifty children, rendering them at risk for potentially deadly allergic reactions as well as for poor nutrition that comes with avoiding cow’s milk. In this month’s issue of JACI, Bunyavanich and colleagues relay the results of their research on how gut bacteria might influence the course of this disease (J Allergy Clin Immunol 2016; 138(4): 1122-1130).  They looked at the stools of 234 milk allergic children ranging in age from 3 to 16 months. They used 16s rRNA sequencing to profile the different types of gut bacteria and followed the children up to age 8 years.

They found that among children age 3 to 6 months, bacteria in the Firmicutes phylum and Clostridia class were associated with resolution of milk allergy by age 8 years.  This is consistent with preliminary findings from mouse models that also show that Clostridia have a role in regulating sensitization to food allergens.  However, these bacteria appear to have a very short time window to exert their effect, because there was no association in children beyond 6 months of age.  It is possible that the immune systems of infants up to six months of age are easier to tolerize, or that the introduction of solid foods at around age 6 months obscures this association.

It is possible that the fatty acids produced by bacteria may have potent roles in reestablishing tolerance, but the study was not structured to answer that question.  Other questions left to answer include whether supplementation with probiotics can help reestablish tolerance and whether introducing these bacteria would be safe.