Early allergen sensitization is associated with an increased risk of viral infections and the development of childhood asthma.
Tina V. Hartert, MD
Early development sensitization, combined with viruses, can strongly influence the likelihood of asthma by 6 years of age.
In a presentation of early childhood asthma drivers, and the several interventions shown to provide clinical benefit in preventing the condition or preserving lung function, a distinguished panel of speakers at the 2018 American Academy of Allergy, Asthma, and Immunology (AAAAI)/World Allergy Organization (WAO) Joint Congress in Orlando, Florida, drove home the importance of addressing pediatric asthma causes.
Augusto A. Litonjua, MD, MPH, a professor in the department of Pediatrics at the University of Rochester, described the current understanding of the fetal origins of asthma and what modifiable factors would appear to be most important in causing childhood onset asthma.
He highlighted nutritional modulations that have demonstrated clinically significant positive benefit in correcting otherwise poor lung function. While most clinical trials produced negative data, there were 3 interventions that have yielded positive data in multiple independent clinical trials, according to Litonjua.
Supplementation with vitamin D (4,000-6,000 iu) or polyunsaturated fatty acid (PUFA; 4g) supplementation during pregnancy clearly reduces the risk of developing childhood asthma. Mothers with lower initial EPA/DHEA were the most responsive to PUFA administration. Moreover, clinical trials have proven that supplementation with 500 mg of vitamin C daily to pregnant smokers can prevent the maternal smoking-associated reduced lung function at birth and wheezing through 1-year post-birth.
Early allergen sensitization is associated with an increased risk of viral infections and the development of childhood asthma. James E. Gern, MD, a pediatrician and professor at the University of Wisconsin school of medicine described studies clearly demonstrating that early sensitization occurring before 3 years of age, is highly correlated with a greater likelihood for developing asthma by school age of 7 years. Moreover, according to Gern, atopy may be may be considered a quantitative concept where IgE predicts asthma and preschool wheeze.
In the PROSE clinical trials study, Gern described how treatment with antibodies against IgE (omalizumab; n=259) versus placebo (n=89) caused a reduction in rhinovirus infection. He explained how this study helps to elucidate the mechanism by which allergen-mediated IgE cross-linking interferes with plasmocytoid dendritic cell interferon-α anti-viral activities.
"The prevention of atopic dermatitis and food allergy that could lead to a respiratory allergy with multiple sensitization could interrupt this process and perhaps lessen the burden of asthma in childhood,” Gern said.
The predominant viral pathogens during infancy and early childhood that are strongly associated with future asthma are respiratory syncitial virus (RSV) and human rhinovirus (HRV). Tina V. Hartert, MD, the Director for the Center for Asthma Research at the Vanderbilt Institute for Medicine & Public Health described her studies examining how these two viruses are different and how these are modifiable risk factors for asthma. She pointed out that studies indicate that RSV is one of the strongest known risk factors for asthma and there is a clear dose-response relationship with the likelihood for asthma and disease severity.
Hartert stressed that these viruses represent early life insults that are common, but that they represent significant disease burdens under certain circumstances and that we need acceptable interventions in pregnant women. Her studies have revealed RSV disease severity depends on the strain of virus and the microbiota.
During the Q&A, Hartert pointed out that RSV can cause a tremendous amount of lung destruction and mortality, particularly in the low income countries. Most of the management is supportive care. She stressed that prevention of allergic sensitization could help prevent susceptibility to viral infection and ultimately prevention of asthma.
The field prosed questions about vitamins and what can be done for prevention of RSV infections. DHartert said they are particularly interested in and studying vitamin E and diet right now, but do not have anything unequivocal.
As far as prophylactic prevention of RSV infection, this is currently invasive and costly as a once monthly injection, but she stressed that it does reduce wheezing dramatically by 12 months after birth and it reduces asthma risk by 40-60% at 6 years of age.