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Longitudinal Analysis of Group A Streptococcus emm Types and emm Clusters in a High-Prevalence Setting: Relationship
Patricia Therese Campbell1,2, Steven Y C Tong3,4,5, Nicholas Geard1,6
1Victorian Infectious Diseases Reference Laboratory Epidemiology Unit, The Peter Doherty Institute for Infection and Immunity, The Royal Melbourne Hospital and The University of Melbourne, Melbourne, Australia.
Abstract:
Group A Streptococcus is a pathogen of global importance, but despite the ubiquity of group A Streptococcus infections, the relationship between infection, colonization, and immunity is still not completely understood. The M protein, encoded by the emm gene, is a major virulence factor and vaccine candidate and forms the basis of a number of classification systems. Longitudinal patterns of emm types collected from 457 Fijian schoolchildren over a 10-month period were analyzed. No evidence of tissue tropism was observed, and there was no apparent selective pressure or constraint of emm types. Patterns of emm type acquisition suggest limited, if any, modification of future infection based on infection history. Where impetigo is the dominant mode of transmission, circulating emm types either may not be constrained by ecological niches or population immunity to the M protein, or they may require several infections over a longer period of time to induce such immunity.
Insights
Group A Streptococcus emm types in Fijian schoolchildren showed no signs of tissue tropism or constraints. Infection history appears to have limited impact on future Group A Streptococcus infections.
Area of Science:
- Microbiology
- Immunology
- Epidemiology
Background:
- Group A Streptococcus (GAS) is a significant global pathogen.
- The M protein (emm gene) is crucial for GAS virulence, classification, and vaccine development.
- Understanding GAS infection dynamics, colonization, and immunity is incomplete.
Purpose of the Study:
- To analyze longitudinal patterns of emm type acquisition in Fijian schoolchildren.
- To investigate potential tissue tropism, selective pressures, or constraints on emm types.
- To explore the influence of infection history on subsequent GAS infections.
Main Methods:
- Longitudinal collection of emm types from 457 schoolchildren over 10 months.
- Analysis of emm type acquisition patterns.
- Assessment for tissue tropism and selective pressures.
Main Results:
- No evidence of tissue tropism for specific emm types was observed.
- No apparent selective pressure or constraint on circulating emm types was detected.
- Patterns suggest limited modification of future infections based on prior infection history.
Conclusions:
- Circulating emm types may not be limited by ecological niches or population immunity in impetigo-dominant settings.
- Developing immunity to M protein may require multiple infections over an extended period.
- Further research is needed to fully understand GAS immunity and infection dynamics.
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