Poster Presentation 20th Lancefield International Symposium on Streptococci and Streptococcal Diseases 2017

Demonstration of Antibody Dependent Enhancement (ADE) like phenomenon in cases of pyoderma & pharyngitis caused by Group A Streptococci (GAS) & Streptococcus dysgalactiae subspecies equisimilis (SDSE) (#173)

Mohan Karmarkar 1 , Gouri Hule 1 , Nuzhat Surve 1 , Preeti Mehta 1 , Uday Khopkar 1 , Chandrahas Deshmukh 1 , Kadaba Sriprakash 2
  1. Seth G S Medical college and KEM Hospital, Mumbai, MAHARASHTRA, India
  2. QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia

Background: GAS & SDSE are significant human pathogens sharing similar disease spectra. Commonly seen infections like pyoderma & pharyngitis may lead to serious immune sequelae like RF/RHD & PSGN. Sreptococcal Inhibitor of complement (SIC) & its orthologue, distantly related to SIC (DRS) are virulence factors expressed by only 4 M types of GAS. DRSG (orthologue of DRS) is a virulence factor expressed by some strains of SDSE. In the past we had observed sero-positivity to these three antigens in chronic kidney disease (CKD) & end stage renal disease (ESRD) patients.

Methods: GAS & SDSE isolates recovered from pharyngitis & pyoderma cases were subjected to emm typing. Sero-positivity for SIC, DRS & DRSG was studied by ELISA test.  In this study, immune response against all the 3 antigens from above mentioned cases is compared with age & sex matched controls who had no history of streptococcal infections in last 6 months. The results were checked statistically by two-tailed P Test.

Results: We found positive association between the SIC/DRS antibodies and pyoderma with diverse M types. Similar observations were also seen in pharyngitis when compared with respective controls. The mechanism of increased predisposition to pyoderma & pharyngitis among SIC/DRS antibody-positive population by diverse isolates is not clear.

Conclusions: Although only 4 types express SIC/DRS antigens, they elicit persistent antibody response. Therefore, antibody prevalence in a population is cumulative result of past infections by one of these four “core” types.  Our observations could be explained by a phenomenon akin to ADE.