Oral Presentation Asia-Pacific Vaccine and Immunotherapy Congress 2023

Tissue homing Regulatory T cell FOXP3 downregulation and associated transcriptomic disruptions are biomarkers for predicting Long-COVID. (#52)

Christopher M Hope 1 2 , Sarah M Battersby 2 , Ying Wong 1 2 , James D Brown 3 , Catherine Ferguson 4 , Jason Gummow 5 , Holly Withers 2 , David Shaw 4 , Michael R Beard 6 , Cheryl Y Brown 2 , Branka Grubor-Bauk 7 , Simon C Barry 1 2 5
  1. Women's and Children's Hospital, North Adelaide, SA, Australia
  2. Molecular Immunology, Robinson Research Institute, Adelaide, SA, Australia
  3. Roberson Research Institute , University of Adelaide, Adelaide, SA, Australia
  4. Infectious Diseases Department, Royal Adelaide Hospital, Central Adelaide Local Health Network, Adelaide, SA, Australia
  5. Gene Silencing and Expression Core Facility, Adelaide Health and Medical Sciences, Robinson Research Institute, Adelaide, SA, Australia
  6. Research Centre for Infectious Diseases, School of Biological Sciences, University of Adelaide, Adelaide, SA, Australia
  7. Viral Immunology Group, Adelaide Medical School, University of Adelaide and Basil Hetzel Institute for Translational Health Research, Adelaide, SA, Australia

Background: COVID-19 has long-lasting impacts on the immune system, during convalescence there can be disease persistence and/or de novo symptoms arising 4-12 weeks post infection (wpi) which cannot be explained with an alternative diagnosis. This clinical sequalae is known colloquially as Long-COVID. Without definitive criteria for diagnoses, there are inconsistencies in detecting, reporting, and treating Long-COVID, therefore, biomarkers for Long-COVID are needed. Regulatory T cells (Tregs) are a key player in immune homeostasis as Tregs control immune responses by multiple mechanisms coordinated by the transcription factor Forkhead Box P3 (FOXP3). Previously, we have shown specific T-helper Regs (ThR) are reduced at 16wpi. Here, we report discovery of biomarkers for Long-COVID linked to FOXP3 and ThR, using immunophenotyping and genomics in Tregs. 

Methods: Flow cytometry was used to immunophenotype Treg maturation status, lineage commitment, and FOXP3 expression in 16wpi samples from those who had mild or moderate COVID-19. Samples were from: 11 convalescent subjects self-diagnosed with Long-COVID (LC), 11 convalescent subjects (CC) and 10 unvaccinated and uninfected Healthy Controls (HC). Transcriptomics was performed on two Treg subsets: ThR2 and ThR22. 

Results: Memory and ThR22 proportions were lower, and FOXP3 expression was lower in the Treg compartment, memory compartments, as well as multiple ThR subsets, including ThR2 and ThR22, in LC compared with CC. Area Under Receiver Operator Characteristics curve (AUROC) analysis revealed ThR22 FOXP3 levels as a biomarker of Long-COVID (Area=0.86, p-value=0.0049). The ThR2 transcriptome consisted of elevated genes associated with leukocyte migration and cell signalling. ThR22 transcriptome had alterations in heme binding, serotonin transport and reduced chemotaxis. 

Conclusion: We observed significant deficiencies in ThR22 and to a lesser extent ThR2 in Long-COVID. Reduced FOXP3 expression and corresponding transcriptomics changes suggests ThR22 may be involved in cardiovascular and hormonal perturbations in Long-COVID, with ThR22 FOXP3 levels a strong biomarker of Long-COVID.