Evidence for a causal relationship between allergic sensitization and rhinovirus wheezing in early life

Abstract

Rationale: Aeroallergen sensitization and virus-induced wheezing are risk factors for asthma development during early childhood, but the temporal developmental sequence between them is incompletely understood.

Objective: To define the developmental relationship between aeroallergen sensitization and virus-induced wheezing.

Methods: A total of 285 children at high risk for allergic disease and asthma were followed prospectively from birth. The timing and etiology of viral respiratory wheezing illnesses were determined, and aeroallergen sensitization was assessed annually for the first 6 years of life. The relationships between these events were assessed using a longitudinal multistate Markov model.

Measurements and main results: Children who were sensitized to aeroallergens had greater risk of developing viral wheeze than nonsensitized children (hazard ratio [HR], 1.9; 95% confidence interval [CI], 1.2-3.1). Allergic sensitization led to an increased risk of wheezing illnesses caused by human rhinovirus (HRV) but not respiratory syncytial virus. The absolute risk of sensitized children developing viral wheeze was greatest at 1 year of age; however, the relative risk was consistently increased at every age assessed. In contrast, viral wheeze did not lead to increased risk of subsequent allergic sensitization (HR, 0.76; 95% CI, 0.50-1.1).

Conclusions: Prospective, repeated characterization of a birth cohort demonstrated that allergic sensitization precedes HRV wheezing and that the converse is not true. This sequential relationship and the plausible mechanisms by which allergic sensitization can lead to more severe HRV-induced lower respiratory illnesses support a causal role for allergic sensitization in this developmental pathway. Therefore, therapeutics aimed at preventing allergic sensitization may modify virus-induced wheezing and the development of asthma.

Figure 1.

Four-state longitudinal model assessing relationships between allergic sensitization and viral wheezing. At yearly intervals, children were classified in one of these four states. The relative probability of moving from one state to another identifies the sequence of and thereby the potential causal relationship between allergic sensitization and viral wheezing.

Figure 2.

(A) Cumulative rates of wheezing assessed prospectively in the cohort. (B) Cumulative rates of sensitization to aeroallergens assessed annually in the cohort. (C) Longitudinal rates of the four-state model combining wheezing and allergic sensitization at each annual assessment.