Related Experiment Videos
Protective immunity to the group A Streptococcus may be only strain specific
1ESR Health: Communicable Disease Centre, Porirua, New Zealand.
Abstract:
M protein enables Group A streptococci to resist phagocytosis. Protective immunity is considered to be mediated by opsonic antibodies directed against this M protein. In recent studies we have shown that genetically distinct populations exist within an M-type. The question asked in this study was whether human and rabbit type specific M1 antibody was opsonic for all strains of M-type 1, irrespective of their restriction fragment length polymorphism type. When locating a blood donor from among our staff for use in the indirect bactericidal test, selective variation in opsonic ability was demonstrated by one person. Subsequent testing of 44 randomly selected human sera revealed that 11 (25%) had opsonic antibody. Of these 11, 6 opsonised all seven strains and 5 demonstrated selective opsonisation. We conclude that opsonic antibody is not necessarily type specific but may be strain specific.
Insights
Opsonic antibodies, crucial for immunity against Group A Streptococcus, may be strain-specific, not just type-specific. This finding impacts our understanding of protective immunity and vaccine development against M1 strains.
Area of Science:
- Microbiology
- Immunology
- Bacteriology
Background:
- M protein in Group A Streptococcus (GAS) facilitates resistance to phagocytosis.
- Opsonic antibodies targeting M protein are believed to mediate protective immunity.
- Recent findings indicate genetic diversity within M-types, suggesting potential strain-specific variations.
Purpose of the Study:
- To investigate if type-specific M1 antibodies exhibit opsonic activity against all M-type 1 strains, regardless of their genetic (restriction fragment length polymorphism) type.
- To determine the prevalence and specificity of opsonic antibodies in human sera against M1 strains.
Main Methods:
- Indirect bactericidal assays were employed to test the opsonic activity of human and rabbit M1 antibodies.
- Human sera were screened for opsonic antibodies against various M-type 1 strains with differing genetic profiles.
- Restriction fragment length polymorphism (RFLP) typing was used to characterize bacterial strains.
Main Results:
- Selective variation in opsonic ability was observed in human sera.
- Out of 44 randomly selected human sera, 11 (25%) possessed opsonic antibodies.
- Of the 11 sera with opsonic activity, 6 opsonised all tested M1 strains, while 5 showed selective opsonisation of specific strains.
Conclusions:
- Opsonic antibodies against M protein may not be strictly type-specific.
- Antibody specificity can be strain-specific within a given M-type.
- These findings suggest a more complex immune response to GAS than previously understood, with implications for vaccine design.