Total and serotype-specific pneumococcal antibody titres in children with normal and abnormal humoral immunity

Area of Science:

• Immunology
• Vaccinology
• Pediatrics

Background:

• Invasive pneumococcal disease poses a significant threat to children.
• Understanding antibody responses to pneumococcal vaccines is crucial for assessing efficacy.
• Children with recurrent or severe infections may have altered immune responses.

Purpose of the Study:

• To evaluate immunoglobulin subclass and serotype-specific antibody responses to PCV-7 vaccination in children with a history of recurrent or severe bacterial infections.
• To compare antibody responses after PCV-7 and 23-valent pneumococcal polysaccharide vaccine (PPV-23) administration.
• To determine the protective capacity against specific pneumococcal serotypes.

Main Methods:

• Assay of pneumococcal IgG, IgG1, and IgG2 titres using ELISA in 145 children.
• Measurement of nine serotype concentrations via a nonaplex bead assay.
• Analysis of antibody responses following two doses of PCV-7 and one dose of PPV-23.

Main Results:

• Vaccination with PCV-7 and PPV-23 elicited an exclusively IgG1 subclass response.
• Pneumococcal IgG2 antibody titres remained low to negligible post-vaccination.
• While PCV-7 specific responses increased, IgG against non-PCV-7 serotypes remained low, indicating PPV-23 did not broaden protection.

Conclusions:

• Antibody responses to PCV-7 in children are primarily of the IgG1 subclass, unlike responses to natural infection or PPV-23 which often involve IgG2.
• Serotype-specific IgG measurements are valuable for assessing protection against specific pneumococcal strains.
• PPV-23 did not enhance protection against pneumococcal serotypes not included in PCV-7.