Predisposition of the asthmatic child to legionellosis?

The prevalence of seropositivity to Legionella spp. was studied in 184 children with bronchial asthma and in 80 control children, age- and sex-matched, without respiratory tract infections. The sera were examined by indirect immunofluorescence with antigens of six Legionella spp. The asthmatic children showed a significantly higher percentage of seroreactions to L. pneumophila than did the control children. In the asthmatic children, no association was found between age, sex, onset of asthmatic symptoms, living conditions, corticosteroid treatment, or exposure to aerosols and seropositivity to Legionella. No correlation could be found between the asthma severity score and the titer of serum antibodies to L. pneumophila. None of the 32 sera with titers of 256 or higher were reactive for Legionella-specific IgE antibodies. L. pneumophila antigen was detected in the urine of three children by an enzyme-linked immunosorbent assay (ELISA). The high prevalence of antibodies to L. pneumophila found in children with bronchial asthma, together with the detection of antigen in the urine of some of them, suggest that this group of children are highly susceptible to Legionnaires' Disease.