Introduction
Exposure to respiratory viruses is a significant cause of morbidity worldwide both in children and adults. Among children, respiratory syncytial virus (RSV) causes bronchiolitis and is the most common cause of respiratory hospitalization and the second biggest cause of lower respiratory infection mortality worldwide (1). Other respiratory viruses, especially rhinovirus (RV) strains, are also major risk factors of respiratory morbidity because they are known to trigger severe asthma exacerbations in children (2). Longitudinal studies showed that RSV and RV-induced bronchiolitis and wheezing illness in early childhood are associated with subsequent development of asthma (3–8). In healthy adults, RSV and RV are responsible of common colds, with frequent reinfections; and in frail elderly persons, they cause insidious deteriorations of respiratory health with high mortality (2). Additionally, RV can trigger symptoms of asthma and asthma exacerbations in allergic patients and individuals susceptible to viral-induced attacks (9).
Infections of RSV and RV viruses are more common during childhood. Virulence and persistence of specific immune responses to these respiratory viruses differ between individuals. To date, the studies identifying determinants, in particular personal factors (age, sex, body mass index (BMI), tobacco smoking) and season of blood sampling, of RSV and RV-specific antibody response remains scarce and often conflicting results are reported, especially related to passive and active tobacco exposure (10–12). Moreover, none of these studies focused on population including both children and adults.
Using the novel micro-array technology, it is possible to measure RSV-specific antibody response as well as RV-specific antibody responses to different RV species (13). Accordingly, cumulative levels of RV-specific antibody levels may be considered as an immunological imprint of previous RV infections and their severity. However, there may be also differences regarding the severity of RV infections depending on the RV-species involved. For example, among the three RV species, RV-A and RV-C were associated with more severe illness and RV-B with mild symptoms or asymptomatic infections, especially in children (14,15).
In the present study, we performed a comprehensive analysis to assess RSV and RV-specific IgG responses in a large cohort of well characterized children and adults by using a micro-array technology to identify factors associated with RSV and RV-specific antibody responses.