Mucosal immune response to specific outer membrane proteins of Moraxella catarrhalis in young children.
BACKGROUND
Moraxella catarrhalis is an important cause of otitis media. A number of candidate antigens for a future infant otitis media vaccine have been identified, but their mucosal immunogenicity induced by nasopharyngeal M. catarrhalis colonization has not been characterized. The aim of this study was to determine the salivary IgA response to M. catarrhalis outer membrane proteins (OMP) in young children.


METHODS
Children ages 1 to 24 months evaluated for acute respiratory tract infection were prospectively enrolled. M. catarrhalis nasopharyngeal colonization was determined by (1) selective culture and (2) detection by reverse transcription-PCR of messenger RNA specific for the OMP UspA1 and UspA2. Salivary IgA responses were detected by immunoblot analysis of M. catarrhalis OMP. Isogenic knockout mutants for UspA1, UspA2, hemagglutinin (Hag), transferrin-binding protein B (TbpB) and CopB were constructed for identification of specific target OMP.


RESULTS
Sixty-six patients were studied. The rates of M. catarrhalis colonization by culture, reverse transcription-PCR for messenger RNA and mRNA were 40, 94 and 58%, respectively. Anti-M. catarrhalis salivary IgA was detected in 62 patients (94%). IgA directed against a >250-kDa antigen (assigned to UspA1/UspA2 by mutant analysis) and a 200-kDa antigen (Hag) were detected in 65 and 70% of patients, respectively. Bands at 80 to 85 kDa (82%) consisted of IgA directed against monomeric UspA2, TbpB and CopB.


CONCLUSIONS
colonization occurring in early infancy is associated with a consistent mucosal immune response directed against the UspA proteins, Hag and other OMP. The data suggest that several M. catarrhalis OMP are immunogens of the nasopharyngeal mucosal immune system of infants.
Meier
Patricia Stutzmann
PS
Institute for Infectious Diseases, University of Bern, Switzerland.
Freiburghaus
Simone
S
Martin
Andrea
A
Heiniger
Nadja
N
Troller
Rolf
R
Aebi
Christoph
C
D017677:Age Distribution; D001425:Bacterial Outer Membrane Proteins / Q000276:immunology*; D002675:Child, Preschool; D015331:Cohort Studies; D015169:Colony Count, Microbial; D005260:Female; D006801:Humans; D018928:Immunity, Mucosal; D015151:Immunoblotting; D007074:Immunoglobulin G / Q000032:analysis*; D015994:Incidence; D007223:Infant; D008297:Male; D001936:Moraxella catarrhalis / Q000276:immunology* / Q000302:isolation & purification; D009305:Nasopharynx / Q000276:immunology / Q000382:microbiology; D011336:Probability; D011446:Prospective Studies; D012329:RNA, Bacterial / Q000032:analysis / Q000276:immunology; D012141:Respiratory Tract Infections / Q000453:epidemiology / Q000276:immunology* / Q000382:microbiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D017678:Sex Distribution; D018709:Statistics, Nonparametric
D001425:Bacterial Outer Membrane Proteins; D007074:Immunoglobulin G; D012329:RNA, Bacterial