Pneumococcal serotype-specific IgG and opsonophagocytic activity in young Japanese patients with asplenia

Area of Science:

• Immunology
• Vaccinology
• Pediatrics

Background:

• Patients with asplenia face a high risk of severe infections from encapsulated bacteria, particularly Streptococcus pneumoniae.
• Pneumococcal conjugate vaccine (PCV13) and pneumococcal polysaccharide vaccine (PPSV23) are recommended for preventing invasive pneumococcal disease.
• Immune responses to pneumococcal vaccines in young asplenic patients remain understudied.

Purpose of the Study:

• To evaluate pneumococcal serotype-specific IgG levels and opsonophagocytic activity in young patients with asplenia.
• To compare immune responses between patients who received PCV13 and those who received only PPSV23.

Main Methods:

• Measurement of pneumococcal serotype-specific IgG (Pn-IgG) and opsonophagocytic activity (Pn-OPA) against selected PCV13 serotypes.
• Analysis of serum samples from 23 young patients with asplenia, some of whom had received PCV13 or PPSV23.
• Comparison of immune markers between vaccination groups, considering the time elapsed since the last vaccine dose.

Main Results:

• Overall Pn-IgG geometric mean concentrations (GMCs) were below those of healthy controls, despite being above cutoff levels.
• Patients vaccinated only with PPSV23 exhibited significantly lower Pn-IgG GMCs against four serotypes compared to those who received PCV13.
• Patients vaccinated only with PPSV23 showed significantly lower Pn-OPA geometric mean titers (GMTs) against three serotypes compared to those who received PCV13.

Conclusions:

• Young patients with asplenia may have insufficient immunity against certain PCV13 pneumococcal serotypes.
• Vaccination strategies involving PCV13 appear to elicit a more robust immune response than PPSV23 alone in this population.
• Further research and appropriate vaccination schedules are needed to ensure adequate protection in young asplenic patients in the post-PCV13 era.