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Epidemiological studies of Streptococcus pneumoniae in infants: development of antibody to phosphocholine
Insights
Infants develop antibodies to phosphocholine (PC) in response to pneumococcal carriage and infection. Antibody levels increase with age and are highest after exposure to multiple pneumococcal types.
Area of Science:
- Immunology
- Microbiology
- Pediatrics
Background:
- Pneumococci have species-common antigens, including phosphocholine (PC), a determinant of the C-carbohydrate.
- Antibodies to PC protect mice from pneumococcal infection, but their role in humans is less understood.
- The impact of pneumococcal carriage and infection on human anti-PC antibody levels requires further investigation.
Purpose of the Study:
- To investigate the development of immunoglobulin M antibody to phosphocholine (anti-PC) in infants.
- To determine how pneumococcal carriage and infection influence anti-PC antibody levels throughout early childhood.
- To explore the relationship between age, pneumococcal exposure, and anti-PC antibody titers.
Main Methods:
- Prospective study of 30 infants from birth to 4 years of age.
- Analysis of 115 serum samples using a solid-phase radioimmunoassay for immunoglobulin M antibody to PC.
- Regression modeling to assess the influence of age and pneumococcal carriage on anti-PC levels.
Main Results:
- Infants developed anti-PC antibodies in response to pneumococcal carriage and infection.
- Nearly all infants exhibited some level of anti-PC antibody, with levels increasing with age.
- Anti-PC levels were highest following exposure to two or three different pneumococcal types and peaked shortly after acquisition, declining thereafter.
Conclusions:
- Infant immune responses include the development of anti-PC antibodies following pneumococcal exposure.
- Age and the diversity of pneumococcal encounters significantly modulate anti-PC antibody levels in early childhood.
- These findings highlight the dynamic interplay between pneumococcal colonization and the developing human immune system.
Abstract:
The pneumococci possess, in addition to type-specific capsular polysaccharides, a number of antigens common to the species. Antibodies to phosphocholine (PC), a major determinant of the C-carbohydrate, have been shown to protect mice from experimental pneumococcal infection, but little is known of the role of anti-PC antibodies in humans or the extent to which anti-PC levels are affected by carriage or infection. We examined 115 sera from 30 infants, who were followed prospectively from birth through 4 years of age, for the presence of immunoglobulin M antibody to PC, using a solid-phase radioimmunoassay method. Infants were found to develop antibody to PC in response to pneumococcal carriage and infection, and nearly all infants developed some antibody. Antibody levels increased with age. By using a regression model including both age and nasopharyngeal carriage of pneumococci, anti-PC levels were found to be highest after exposure to two or three different types of pneumococci; levels were highest soon after acquisition of pneumococci and declined thereafter.