Poster Presentation Lancefield International Symposium for Streptococci and Streptococcal Diseases 2025

Evaluation of a Total IgG Assay for Normalisation of Antigen Specific IgG Data from Variably Collected Capillary Blood Samples (#205)

Chantalia Tedja 1 2 3 , Anna Takahashi 1 2 3 , Michael Morici 1 2 3 , Christian Tjiam 2 3 4 , Zi Ying Ng 1 2 3 , Hannah Frost 1 5 , Serene Yeow 1 5 , Jill Gilmour 6 , Andrew Steer 1 5 , Jonathan Carapetis 1 2 3 7 8 , Alma Fulurija 1 2 3 7
  1. The Australian Strep A Vaccine Initiative, Nedlands, Western Australia
  2. Wesfarmers Centre for Vaccines and infectious Diseases, Nedlands, Western Australia
  3. The Kids Research Institute Australia, Nedlands, Western Australia, Australia
  4. PathWest Laboratory Medicine WA, Murdoch, Western Australia
  5. Murdoch Children's Research Institute, Parkville, Victoria
  6. JWG Global Lab Solution, Dumfries, Scotland
  7. The University of Western Australia, Nedlands, Western Australia
  8. Perth Children's Hospital, Nedlands, Western Australia

BACKGROUND: Capillary Blood Sample (CBS) collection is an alternative method to venepuncture to easily collect blood for a variety of tests, including serology. In cases where full volumetric CBS collection is not obtained, challenges arise in accurately quantifying circulating antigen-specific antibodies. The Australian Strep A Vaccine Initiative (ASAVI) undertook a paediatric urban pharyngitis study, the Sore Throat Melbourne and Perth Study (STAMPS), utilising at-home biospecimen collection with varying CBS volumes obtained. To resolve this issue, we established a Total IgG immunoassay and evaluated its utility to normalise antigen-specific IgG antibody levels in samples. METHODS: CBS on Neoteryx Mitra cartridges (2 x 20μl) were collected from the STAMPS study cohort, from children aged between 3-14 years of age, and eluted in a BSA-based buffer. CBS were collected at pre-determined timepoints and during convalescence from Strep A positive sore throat episodes.  Streptococcal antigen-specific IgG antibodies were quantified on a custom MesoScale Discovery (MSD) Strep A serology panel. In conjunction, Total IgG was quantified using a Total IgG Enzyme-Linked ImmunoSorbent Assay (ELISA) with methods developed in-house. Values obtained from each method were then used to generate a normalised ratio of antigen-specific IgG to the total IgG found in individual samples. RESULTS/CONCLUSION: Results are currently being analysed and will be presented at the conference. We have developed a Total IgG ELISA and evaluated its use normalisation of IgG in blood collected by methods prone to variability. This assay could help to facilitate reliable measurement of antigen-specific antibodies on the MSD platform.