title: Detection of antibody responses against Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis proteins in children with community-acquired pneumonia: effects of combining pneumococcal antigens, pre-existing antibody levels, sampling interval, age, and duration of illness.
abstract: We evaluated the effects of combining different numbers of pneumococcal antigens, pre-existing antibody levels, sampling interval, age, and duration of illness on the detection of IgG responses against eight Streptococcus pneumoniae proteins, three Haemophilus influenzae proteins, and five Moraxella catarrhalis proteins in 690 children aged <5 years with pneumonia. Serological tests were performed on acute and convalescent serum samples with a multiplexed bead-based immunoassay. The median sampling interval was 19 days, the median age was 26.7 months, and the median duration of illness was 5 days. The rate of antibody responses was 15.4 % for at least one pneumococcal antigen, 5.8 % for H. influenzae, and 2.3 % for M. catarrhalis. The rate of antibody responses against each pneumococcal antigen varied from 3.5 to 7.1 %. By multivariate analysis, pre-existing antibody levels showed a negative association with the detection of antibody responses against pneumococcal and H. influenzae antigens; the sampling interval was positively associated with the detection of antibody responses against pneumococcal and H. influenzae antigens. A sampling interval of 3 weeks was the optimal cut-off for the detection of antibody responses against pneumococcal and H. influenzae proteins. Duration of illness was negatively associated with antibody responses against PspA. Age did not influence antibody responses against the investigated antigens. In conclusion, serological assays using combinations of different pneumococcal proteins detect a higher rate of antibody responses against S. pneumoniae compared to assays using a single pneumococcal protein. Pre-existing antibody levels and sampling interval influence the detection of antibody responses against pneumococcal and H. influenzae proteins. These factors should be considered when determining pneumonia etiology by serological methods in children.
authors.affiliation: Postgraduate Programme in Health Sciences, Federal University of Bahia School of Medicine, Praça XV de Novembro, s/n - Largo do Terreiro de Jesus, Salvador, Bahia, 40025-010, Brazil, igorcms@gmail.com.
authors.forename: I C
authors.initials: IC
authors.lastname: Borges
authors.forename: D C
authors.initials: DC
authors.lastname: Andrade
authors.forename: A-L
authors.initials: AL
authors.lastname: Vilas-Boas
authors.forename: M-S H
authors.initials: MS
authors.lastname: Fontoura
authors.forename: H
authors.initials: H
authors.lastname: Laitinen
authors.forename: N
authors.initials: N
authors.lastname: Ekström
authors.forename: P V
authors.initials: PV
authors.lastname: Adrian
authors.forename: A
authors.initials: A
authors.lastname: Meinke
authors.forename: M-R A
authors.initials: MR
authors.lastname: Cardoso
authors.forename: A
authors.initials: A
authors.lastname: Barral
authors.forename: O
authors.initials: O
authors.lastname: Ruuskanen
authors.forename: H
authors.initials: H
authors.lastname: Käyhty
authors.forename: C M
authors.initials: CM
authors.lastname: Nascimento-Carvalho
mesh_terms: D000907:Antibodies, Bacterial / Q000097:blood*; D001426:Bacterial Proteins / Q000276:immunology; D002675:Child, Preschool; D017714:Community-Acquired Infections / Q000175:diagnosis*; D005260:Female; D006193:Haemophilus influenzae / Q000276:immunology*; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D007223:Infant; D008297:Male; D001936:Moraxella catarrhalis / Q000276:immunology*; D018410:Pneumonia, Bacterial / Q000175:diagnosis*; D012680:Sensitivity and Specificity; D012698:Serologic Tests / Q000379:methods*; D013296:Streptococcus pneumoniae / Q000276:immunology*
chemical_list: D000907:Antibodies, Bacterial; D001426:Bacterial Proteins; D007074:Immunoglobulin G