Oral Presentation 21st Lancefield International Symposium for Streptococci and Streptococcal Diseases 2022

Serological responses following colonisation with Streptococcus pyogenes among children aged 2 to 4 years in The Gambia (#20)

Alexander J Keeley 1 2 3 , Danielle Groves 2 , Edwin Armitage 1 3 , Elina Senghore 3 , Ya Jankey Jagne 3 , Hailey Hornsby 2 , Adri Angyal 2 , Beate Kampmann 1 3 , Michael Marks 1 , Alexandra Shaw 4 , Claire Turner 5 , Thushan de Silva 2 3
  1. London School of Hygiene & Tropical Medicine, London, LONDON, United Kingdom
  2. Infection, Immunity and Cardiovascular Disease, University of Sheffield, Sheffield, United Kingdom
  3. Vaccines and Immunity, MRC Unit The Gambia at LSHTM, Fajara, The Gambia
  4. Division of Bacteriology, National Institute for Biological Standards and Control, London, United Kingdom
  5. School of Biosciences, University of Sheffield, Sheffield, United Kingdom

Background:

Understanding natural immunity in settings with high Streptococcus pyogenes burden is important for developing safe and effective vaccines.

 

Methods:

We performed a post-hoc investigation of participants enrolled in a randomised controlled trial of a live-attenuated influenza vaccine. S. pyogenes colonisation was determined with quantitative polymerase chain reaction (qPCR) to SpeB from nasopharyngeal swabs taken at baseline, day 7 and 21 amongst 201 children who received vaccination and 108 controls. Serum IgG to Cpa, M1, Mac, SpyAD and SpyCEP was quantified by ELISA.

 

Results:

Colonisation was detected in 71 children (22%) at any point in the study period. Only 19 (6%) were colonised on more than one occasion. 21/26 who were colonised at baseline were not colonised at day 7, and 13/23 were colonised at day 7 but not at day 21. Between vaccine and control groups, no significant difference in overall colonisation rates (23% vs 21%, p=0.8), incident colonisation (18 vs 11%, p=0.12), or qPCR-defined colonisation density was demonstrated. IgG titres to M1, SpyCEP, Mac, and SpyAD were significantly higher in colonised vs non-colonised controls (n=101, figure 1A). A significant rise in IgG was seen to M1 and SpyCEP following new colonisation between day 0 and 21(n=18, figure 1B).

 

Conclusion

S. pyogenes colonisation assessed by qPCR was prevalent, and frequently transient, over a 21-day period. Colonisation was associated with increased serum responses to S. pyogenes antigens. Further studies are needed to characterise the role of colonisation-induced natural immunity in the reduction of S. pyogenes disease incidence with age.

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Figure 1: Serum IgG titres to S. pyogenes antigens