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M-associated protein antibodies in patients with rheumatic fever
Abstract:
Sequential serum samples obtained from 50 rheumatic fever subjects and from control individuals matched for time, age and geographical location were tested for antibodies against the M-associated protein antigens, MAP I and MAP II. Antibody titres were determined by the complement fixation test with a partially-purified extract of Streptococcus pyogenes serotype M30 as the MAP I antigen and an acid extract of serotype M48 as the MAP II antigen. Titres of MAP I antibody exceeded those of MAP II antibody in all but six rheumatic fever subjects. Anti-MAP I titres in excess of 40 were significantly more common in rheumatic fever subjects than in matched controls (p less than 0.001) or matched subjects with a diagnosis of acute post-streptococcal glomerulonephritis (p less than 0.01). Peak MAP I titres were present at the time of admission to hospital in the sera of 40 of the 50 rheumatic fever subjects. In the remainder peak titres occurred within 10 days. Antibody titres were maintained for a mean of 10.3 weeks before declining. Changes in MAP antibody titres were independent of changes in antistreptolysin O and anti-DNAase B titres. Normal children aged between 6 and 15 had higher MAP antibody titres than 2-5-year-old children. Rheumatic fever subjects had significantly higher mean titres of MAP I antibody than matched controls in each age group.
Insights
Rheumatic fever patients show significantly higher M-associated protein (MAP) I antibody levels compared to controls. These elevated MAP I antibody titres, detected via complement fixation tests, are a potential biomarker for rheumatic fever.
Area of Science:
- Immunology
- Microbiology
- Rheumatology
Background:
- Rheumatic fever is an inflammatory disease that can follow Streptococcus pyogenes infection.
- M-associated proteins (MAPs) are virulence factors of Streptococcus pyogenes, and antibodies against them may play a role in disease pathogenesis.
- Previous studies have suggested a link between MAP antibodies and rheumatic fever, but further investigation is needed.
Purpose of the Study:
- To investigate the association between antibodies against M-associated protein I (MAP I) and MAP II and rheumatic fever.
- To compare MAP antibody titres in rheumatic fever subjects with those in matched controls and patients with acute post-streptococcal glomerulonephritis.
Main Methods:
- Sequential serum samples from 50 rheumatic fever subjects and matched controls were analyzed.
- Antibody titres against MAP I and MAP II were determined using complement fixation tests with specific Streptococcus pyogenes extracts.
- Comparison of antibody titres was made between different groups and correlated with clinical presentation.
Main Results:
- Rheumatic fever subjects exhibited significantly higher titres of MAP I antibody compared to matched controls (p < 0.001).
- Elevated anti-MAP I titres were also more common in rheumatic fever patients than in those with acute post-streptococcal glomerulonephritis (p < 0.01).
- MAP I antibody titres peaked around the time of hospital admission in most rheumatic fever patients and remained elevated for over 10 weeks.
Conclusions:
- Elevated MAP I antibody titres are strongly associated with rheumatic fever.
- MAP I antibodies may serve as a valuable diagnostic marker for rheumatic fever.
- The immune response to MAP I appears distinct from responses to other streptococcal antigens like antistreptolysin O and anti-DNAase B.