title: Age-dependent differences in IgG isotype and avidity induced by measles vaccine received during the first year of life.
abstract: BACKGROUND
  Measles remains an important cause of death worldwide, and vaccinating individuals at an earlier age could lead to better control of the disease. However, persistence of maternal antibody and young age affect the quantity of vaccine-induced neutralizing antibody and may also affect antibody quality.
  
  
  METHODS
  Enzyme immunoassay was used to analyze measles virus-specific IgG levels, avidity maturation, and isotype changes, using serum samples from infants who received measles vaccine at 6 months of age and measles-mumps-rubella (MMR)-II at 12 months of age (n=26), measles vaccine at 9 months of age and measles-mumps-rubella (MMR)-II at 12 months of age (n=48), or only MMR-II at 12 months of age (n=27).
  
  
  RESULTS
  The median IgG level was lower among infants with maternal antibody than among those without maternal antibody. Compared with median avidity indices for infants aged 12 months, median values were lower for 6-month-old infants with maternal antibody (P=.0001), 6-month-old infants without maternal antibody (P=.001), 9-month-old infants with maternal antibody (P=.03), and 9-month-old infants without maternal antibody (P=.006). The median IgG3 level was highest at 6 months of age. IgG1 was predominant at 12 months. Low avidity responses at 6 or 9 months of age did not hinder higher avidity responses or the switch to IgG1 after secondary vaccination. The 2-dose regimen did not augment the response, compared with the response in infants who received 1 dose at 12 months of age.
  
  
  CONCLUSIONS
  Avidity and isotype maturation of measles vaccine-induced antibody are affected by age, providing insight into the ontogeny of the immune response to measles vaccine.
authors.affiliation: W Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA.
authors.forename: Nitya
authors.initials: N
authors.lastname: Nair
authors.forename: Hayley
authors.initials: H
authors.lastname: Gans
authors.forename: Linda
authors.initials: L
authors.lastname: Lew-Yasukawa
authors.forename: Andrea C
authors.initials: AC
authors.lastname: Long-Wagar
authors.forename: Ann
authors.initials: A
authors.lastname: Arvin
authors.forename: Diane E
authors.initials: DE
authors.lastname: Griffin
mesh_terms: D000375:Aging / Q000097:blood / Q000276:immunology*; D000915:Antibody Affinity; D005260:Female; D006801:Humans; D007115:Immunization Schedule; D007116:Immunization, Passive; D007074:Immunoglobulin G / Q000097:blood* / Q000145:classification; D007132:Immunoglobulin Isotypes / Q000097:blood*; D007223:Infant; D008297:Male; D008457:Measles / Q000517:prevention & control*; D008458:Measles Vaccine / Q000008:administration & dosage / Q000276:immunology*; D022542:Measles-Mumps-Rubella Vaccine / Q000008:administration & dosage / Q000276:immunology*
chemical_list: D007074:Immunoglobulin G; D007132:Immunoglobulin Isotypes; D008458:Measles Vaccine; D022542:Measles-Mumps-Rubella Vaccine