title: Pertussis antibodies in postpartum women and their newborns.
abstract: OBJECTIVE
  To (1) determine the proportion of mothers and infants who had levels of IgG antibody to pertussis antigens predicted to be potentially protective at delivery; (2) evaluate the efficiency of maternal-infant antibody transport; (3) extrapolate infant antibody titers at 6 weeks; and (4) identify maternal factors associated with potentially protective infant antibodies.
  
  
  METHODS
  Sera from mother-infant pairs from February 2006 through to April 2007 were tested for antibody to pertussis antigens by standardized ELISA (enzyme-linked immunosorbent assay). Potentially protective antibody levels were defined as >5 ELISA units (EU) for pertussis toxin (PT), and >10 EU for fimbriae (FIM) and pertactin (PRN). Serological evidence of previous maternal infection was defined from antibody to four antigens by k-means cluster analysis.
  
  
  RESULTS
  In total, 21% (17/81) of mothers and 26% (21/81) of infants had potentially protective antibody levels at delivery. Mean infant-maternal antibody ratios for PT, FIM and PRN were 1.26, 1.36 and 1.31, respectively. At 6 weeks, 11% (9/81) of infants were predicted to have potentially protective antibody levels. Using cluster analysis, 9% (7/81) of mothers had evidence of previous pertussis infection. Infants born to these mothers were predicted to be more likely to have potentially protective antibodies at 6 weeks (43%) than those born to mothers without previous infection (8%) (P=0.03).
  
  
  CONCLUSIONS
  Approximately 75% of infants were born with pertussis antibody levels lower than the modest levels associated with potential protection. Despite effective antibody transfer, nearly 90% of infants were predicted to have little antibody by 6 weeks. Maternal immunization before or during pregnancy might simulate previous pertussis infection and help protect infants through the first months of life.
authors.affiliation: General Pediatric Division, Department of Pediatrics, University of Utah, Salt Lake City, UT 84158, USA. julie.shakib@hsc.utah.edu
authors.forename: J H
authors.initials: JH
authors.lastname: Shakib
authors.forename: S
authors.initials: S
authors.lastname: Ralston
authors.forename: H H
authors.initials: HH
authors.lastname: Raissy
authors.forename: G J
authors.initials: GJ
authors.lastname: Stoddard
authors.forename: K M
authors.initials: KM
authors.lastname: Edwards
authors.forename: C L
authors.initials: CL
authors.lastname: Byington
mesh_terms: D000293:Adolescent; D000328:Adult; D000907:Antibodies, Bacterial / Q000097:blood*; D001425:Bacterial Outer Membrane Proteins / Q000276:immunology; D001886:Bordetella pertussis / Q000276:immunology*; D005260:Female; D010861:Fimbriae, Bacterial / Q000276:immunology; D006801:Humans; D007112:Immunity, Maternally-Acquired; D007231:Infant, Newborn; D037342:Pertussis Toxin / Q000276:immunology; D011247:Pregnancy; D010566:Virulence Factors, Bordetella / Q000276:immunology; D055815:Young Adult
chemical_list: D000907:Antibodies, Bacterial; D001425:Bacterial Outer Membrane Proteins; D010566:Virulence Factors, Bordetella; C068929:pertactin; D037342:Pertussis Toxin