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The immunologic response to group A streptococcal upper respiratory tract infections in very young children
Insights
Very young children mount a robust antibody response to group A streptococcus infections, similar to older children. This suggests their low rates of acute rheumatic fever are not due to immune response differences.
Area of Science:
- Pediatrics
- Immunology
- Infectious Diseases
Background:
- Acute rheumatic fever (ARF) is rare in very young children.
- A leading hypothesis suggests a limited immunologic response to group A Streptococcus (GAS) may explain this rarity.
Purpose of the Study:
- To evaluate immunologic responses to streptolysin O (SLO) and streptococcal deoxyribonuclease B (DNase B) in children with GAS upper respiratory tract infections.
- To test the hypothesis that deficient antibody responses contribute to the low incidence of ARF in very young children.
Main Methods:
- Serial antibody titers (ASO and anti-DNase B) were measured in 301 children (52 ≤ 3 years, 249 > 3 years) with GAS upper respiratory tract infections.
- Immunologic responses were compared between age groups based on antibody rise magnitude and percentage with significant titer increases.
Main Results:
- Very young children showed a greater antibody rise to SLO than older children, comparable to older children's ASO response.
- Anti-DNase B responses in young children were comparable to those in older children.
- Clinical manifestations of GAS infections in young children have not changed significantly.
Conclusions:
- The infrequent occurrence of ARF in very young children is unlikely due to differences in antibody response to SLO or DNase B.
- The study refutes the hypothesis that a limited immunologic capacity explains the rarity of ARF in this age group.
Abstract:
The immunologic responses to streptolysin O and streptococcal deoxyribonuclease B were evaluated in children with group A streptococci recovered from the upper respiratory tract to re-examine the hypothesis that a limited capacity to respond to group A streptococcal infection may explain the rare occurrence of acute rheumatic fever in very young children. ASO and anti-DNase B titers were determined on serial bleedings from a total of 301 individuals (52 less than or equal to 3 years; 249 older than 3 years). Very young children with group A streptococcal upper respiratory tract infections had an immunologic response to SO greater than the response in older children as reflected by the magnitude of the antibody rise, and comparable to the ASO response in older children as measured by the percentage showing a significant titer rise. Similar analyses of the anti-DNase B responses showed the response in young children to be comparable to those of the older group. Clinical manifestations of group A streptococcal upper respiratory tract infection in very young children differ from those observed in older children and have not changed significantly in the past several decades. These data suggest that the infrequent occurrence of acute rheumatic fever in very young children is not due to a difference in antibody response to streptolysin O or streptococcal DNase B.