Class- and subclass-specific pneumococcal antibody levels and response to immunization after bone marrow...

Area of Science:

• Immunology
• Transplantation Medicine
• Vaccinology

Background:

• Bone marrow transplantation (BMT) is a curative therapy for genetic disorders.
• Patients undergoing BMT often experience impaired immune function, increasing susceptibility to infections.
• Pneumococcal infections are a significant concern in immunocompromised individuals, including BMT recipients.

Purpose of the Study:

• To assess immunoglobulin class- and subclass-specific antibody responses to pneumococcal vaccination in children post-BMT.
• To compare antibody levels and vaccine responses in BMT recipients with age-matched healthy children.
• To identify factors influencing antibody production after BMT.

Main Methods:

• Measurement of specific antibody titers (IgG, IgG1, IgG2) to pneumococcal polysaccharide vaccine (Pneumovax II) before and after immunization.
• Comparison of antibody levels and responses between children 1 year or more post-BMT and healthy controls.
• Analysis of the impact of splenectomy, graft-versus-host disease, and donor immunization on antibody levels.

Main Results:

• Median titers of specific IgG, IgG1, and IgG2 antibodies were significantly lower in BMT recipients than pre-transplant levels.
• Pre-immunization antibody levels were markedly lower in BMT patients compared to controls across all measured immunoglobulin classes (IgM, IgG, IgG1, IgG2).
• While the response to Pneumovax II was not significantly different for most subclasses (except IgG2), lower baseline levels prevented BMT patients from reaching protective antibody titers.

Conclusions:

• Children 1 year or more after BMT exhibit diminished pneumococcal antibody levels, particularly IgG subclasses.
• The impaired antibody production, especially the poor IgG2 response, may contribute to the increased risk of Streptococcus pneumoniae infections in the late post-transplant period.
• These findings highlight the need for strategies to improve humoral immunity and reduce infection risk in pediatric BMT survivors.