Prenatal exposure to RSV season influences first-year risk of RSV lower respiratory illness and RSV-specific immune responses assessed at birth

Maternal-to-fetal transmission of respiratory syncytial virus (RSV) has been shown to occur but whether late prenatal exposure to RSV season influences offspring postnatal RSV-lower respiratory illness (LRI) risk in early life or RSV immune status at birth is unclear. In this study, the duration of third trimester RSV season exposure was determined for 1,094 newborns of the Tucson Children's Respiratory Study (TCRS) and found to show an inverse relation to risk for first RSV-LRI in the first year. Cord blood anti-RSV antibody is related to third trimester RSV season exposure but not to first year RSV-LRI risk. In a separate birth cohort (the Infant Immune Study), supernatants from cord blood mononuclear cells stimulated with the recall antigen, UV-inactivated RSV, were assayed for IFN-γ and IL-4. The frequency of detectable IFN-γ (but not IL-4) was increased for those with at least 2 mo of third trimester RSV season exposure, suggestive of a fetal immune response to RSV. IMPORTANCE Our study found that duration of third trimester exposure to RSV season related inversely to subsequent risk of postnatal RSV-LRI in the first year, thus implicating this exposure as an important factor in reducing risk of postnatal RSV-LRIs, a risk reduction that appears to be independent of maternally transferred anti-RSV antibody level. The increase in frequency of detectable IFN-γ and not IL-4 in response to UV-inactivated RSV in cord blood immune cells for infants with greater third trimester exposure to RSV season is suggestive of a Type-1 immune response to RSV occurring in utero.

Risk factors for symptom onset in PI*Z alpha-1 antitrypsin deficiency

BACKGROUND

In an early study of highly symptomatic patients with PI*Z alpha-1 antitrypsin deficiency (AAT), tobacco smoking was identified as a risk factor by comparing the age of symptom onset in smokers and nonsmokers. Age of symptom onset has not been well studied in relationship to other environmental exposures.

METHODS

Environmental exposures were assessed in 313 PI*Z adults through retrospective self-administered questionnaire. Age of onset of symptoms with and without these exposures were analyzed through survival analysis.

RESULTS

Personal smoking was the most important risk factor, associated with earlier onset of cough and wheeze, and showed a dose-dependent relationship with the onset of dyspnea. Childhood environmental tobacco smoke (ETS) exposure was independently associated with younger age of onset of cough. Earlier onset of wheeze was also associated with childhood respiratory infections and family history of emphysema. The report of childhood respiratory infections was associated with childhood ETS exposure, but no statistically significant interactions were noted.

CONCLUSIONS

We conclude that both personal and secondhand exposure to tobacco smoke in childhood are likely to accelerate the onset of symptoms in AAT deficient patients. Respiratory infections in childhood may also contribute to this risk.