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Class-specific antibody response to Haemophilus influenzae type b capsular polysaccharide vaccine
Insights
Infants under 18 months show varied antibody responses to Haemophilus influenzae type b (Hib) polysaccharide vaccines. These findings do not support a specific defect in IgG antibody production in young children.
Area of Science:
- Immunology
- Pediatrics
- Vaccinology
Background:
- Haemophilus influenzae type b (Hib) infections peak in infants around one year old.
- Hib capsular polysaccharide vaccines are effective in children over 18 months.
- Previous studies suggested a defective IgG antibody response in younger children due to immune system immaturity.
Purpose of the Study:
- To investigate the class-specific antibody responses to Hib capsular polysaccharide vaccine in infants and children.
- To determine if there is a specific defect in IgG antibody production in response to the vaccine in young children.
Main Methods:
- Used a solid-phase ELISA to measure class-specific antibody responses (IgG, IgM, IgA).
- Analyzed antibody responses in 14 infants and children vaccinated with the Hib capsular polysaccharide vaccine.
Main Results:
- Younger children (<18 months) showed low and varied responses: IgG-specific, IgM-specific, or no response.
- Older children (>18 months) demonstrated increased IgG antibodies, with some also showing increased IgM.
- IgA antibodies were not detected pre-vaccination but appeared after 15 months of age.
Conclusions:
- The antibody response to Hib capsular polysaccharide vaccine in young children is not specifically defective in IgG production.
- The immune response matures with age, leading to broader immunoglobulin class responses, including IgA, later in infancy.
Abstract:
Bacteremic infections caused by H influenzae type b have their peak incidence in children around one year of age, at a time when the serum antibody response to the capsular polysaccharide is very low [1, 3]. The capsular polysaccharide vaccine has in fact been shown to be efficacious in preventing the disease above but not below the age of 18 months [1]. Preliminary observations supported the notion that slow maturation of cells that synthesize antibody to H influenzae type b altered immunoglobulin class distribution of the response and resulted specifically in a defective IgG antibody response [1]. We have used a solid-phase ELISA to measure the class-specific antibody responses in 14 infants and children vaccinated with the capsular polysaccharide vaccine. We found that, among the infants who were less than 18 months old and whose antibody response was generally low, the response was only IgG-specific in two children and only IgM-specific in two others. In one child an IgG and IgM response was detected, and in two no response was detected. Among the older children, all children showed an increase in IgG antibody; only two also had an increase of IgM antibody. IgA antibodies were not detectable in any preimmune sera. The first IgA antibody responses were seen at the age of 15 months but were common thereafter. These data do not indicate a specific defect of IgG-class antibodies in the antibody response to the capsular polysaccharide vaccine.