Secondhand smoke increases inflammation risk in infants with RSV

SAN DIEGO — Exposing infants with respiratory syncytial virus bronchiolitis to secondhand smoke increases their risk of inflammation, while suppressing T and B cell responses, according to a recent presentation held at IDWeek 2017.

“Parents do not realize that babies breathe faster than adults and therefore their ability to inhale — in this case, tobacco smoke — increases exponentially,” M. Asuncion Mejias, MD, PhD, from the Center for Vaccines and Immunity at The Research Institute at Nationwide Children's Hospital, told Infectious Diseases in Children.

“We know that severe RSV infection is associated with an impaired immune response in infants— what we found is that, indeed, this modifiable risk factor enhanced the already impaired immune response to the infection and it should be avoided,” she added.

To determine the connection between secondhand smoke and RSV infection in infants, the researchers conducted a single-center, prospective study that included infants without prior health concerns who presented to an ED with RSV bronchiolitis. Infants (n=70) were enrolled into either secondhand smoke-exposed or non-exposed groups, determined by levels of nicotine found in their hair.

Additionally, Mejias and colleagues evaluated severity of the disease, as well as the impact of RSV infection on blood transcriptional immune profiles. Children were excluded from the study if they were premature, had chronic medical conditions or insufficient hair.

Mejias and colleagues used a clinical disease severity scoring system with a range of 0 to 15 to assess clinical outcomes and care provided, including hospitalization and intensive care. Gene expression profiling and variations in secondhand smoke exposure were analyzed for patients and healthy controls using blood samples collected at enrollment.

Detectable nicotine was observed in 64.2% of hair samples from 70 infants enrolled in the study with RSV (median age: 2.7 months; 62.8% male; 62.8% white); 25 of these infants had no detectable nicotine. Both those exposed and those not exposed to secondhand smoke demonstrated similar demographic variables.

“We found that parental questionnaires for smoke exposure had a sensitivity of 55%, while hair nicotine concentrations reliably showed which infant was indeed exposed to tobacco,” Mejias said. “Therefore, this applies also to other diseases and when looking for tobacco exposure, it should be measured rather than assessed only by a questionnaire.”

Infants with severe RSV disease (severity score = >10) had a median nicotine concentration of 5.3 ng/mg, whereas those with mild disease (severity score = <5) had a median score of 2.1 ng/mg (P = .49). Significantly greater overexpression of genes associated with inflammation, apoptosis and cell death were observed in the blood transcriptional profiles of infants with RSV who were exposed to secondhand smoke. The researchers also noted a greater suppression of T cell- and B cell- related genes in this cohort.

“Currently, there are no treatment options for RSV and therefore, prevention is key,” Mejias told Infectious Diseases in Children. “This holds true for transmission of the virus as well as factors that can make the disease worse, such as tobacco smoke.”–by Katherine Bortz

Reference:
Diaz A, et al. 1002. Respiratory syncytial virus bronchiolitis: impact of secondhand smoke exposure on immune profiles. Presented at: IDWeek 2017; Oct. 4-8; San Diego.

Disclosure: Please see the study for a full list of relevant financial disclosures.