Impaired pneumococcal immunity in children after treatment for acute lymphoblastic leukaemia

Area of Science:

• Immunology
• Pediatric Oncology
• Infectious Diseases

Background:

• Invasive pneumococcal disease poses a significant risk to children post-allogeneic stem cell transplantation.
• Specific immunity against pneumococci in children undergoing cytotoxic therapy for acute lymphoblastic leukemia (ALL) remains poorly understood.

Purpose of the Study:

• To assess the spontaneous reconstitution of humoral immunity against pneumococcal antigens in children treated for ALL.
• To evaluate total IgG, IgG2 subclass levels, and lymphocyte subsets in these patients.
• To compare immune reconstitution with age-matched unvaccinated healthy controls.

Main Methods:

• Studied 53 children treated for ALL who had not received pneumococcal vaccination.
• Assessed specific antibodies to pneumococcal antigens, total IgG, IgG2 subclass, and lymphocyte subsets.
• Measured immune parameters at 3 and 9 months post-chemotherapy completion.

Main Results:

• Most patients had antibody levels below the protective threshold at 3 and 9 months post-chemotherapy.
• Antibody levels were significantly lower than in unvaccinated healthy controls.
• At 9 months, most patients had normal immunoglobulin and lymphocyte subset counts, indicating selective antibody deficiency.

Conclusions:

• Unvaccinated patients with ALL exhibit a selective immunodeficiency with impaired pneumococcal antibody protection for up to 9 months post-therapy.
• Effective prevention strategies, including chemoprophylaxis and active immunization, are crucial for this vulnerable patient population.