Mannose-binding lectin cord blood levels and respiratory symptoms during infancy: a prospective birth cohort study

Abstract

Respiratory infections cause considerable morbidity during infancy. The impact of innate immunity mechanisms, such as mannose-binding lectin (MBL), on respiratory symptoms remains unclear. The aims of this study were to investigate whether cord blood MBL levels are associated with respiratory symptoms during infancy and to determine the relative contribution of MBL when compared with known risk factors. This is a prospective birth cohort study including 185 healthy term infants. MBL was measured in cord blood and categorized into tertiles. Frequency and severity of respiratory symptoms were assessed weekly until age one. Association with MBL levels was analysed using multivariable random effects Poisson regression. We observed a trend towards an increased incidence rate of severe respiratory symptoms in infants in the low MBL tertile when compared with infants in the middle MBL tertile [incidence rate ratio (IRR) = 1.59; 95% confidence interval (CI): 0.95-2.66; p = 0.076]. Surprisingly, infants in the high MBL tertile suffered significantly more from severe and total respiratory symptoms than infants in the middle MBL tertile (IRR = 1.97; 95% CI: 1.20-3.25; p = 0.008). This association was pronounced in infants of parents with asthma (IRR = 3.64; 95% CI: 1.47-9.02; p = 0.005). The relative risk associated with high MBL was similar to the risk associated with well-known risk factors such as maternal smoking or childcare. In conclusion the association between low MBL levels and increased susceptibility to common respiratory infections during infancy was weaker than that previously reported. Instead, high cord blood MBL levels may represent a so far unrecognized risk factor for respiratory morbidity in infants of asthmatic parents.

Figure 1

Distribution of cord blood MBL levels in ng/ml among the 185 healthy term infants of our cohort.

Figure 2

Association between several risk factors and severe respiratory symptoms during infancy. The incidence rate ratio (number) and 95% CI for weeks with severe respiratory symptoms during the first year of life are given for the different risk factors, adjusted for all risk factors listed in the methods section.

Figure 3

Association between cord blood MBL levels and severe respiratory symptoms according to parental asthma. The incidence rate ratio (number) and 95% CI for weeks with severe respiratory symptoms during the first year of life are given stratified for parental (e.g. maternal and/or paternal) asthmatic disease, adjusted for all risk factors listed in the methods section.

Figure 4

Respiratory viruses isolated using nasal swab PCR at the time of the first acute respiratory tract infection are shown in relation to the infants MBL cord blood concentration and to the age at onset.