Australian scientists identify immune mechanisms against COVID-19


  • Heather Mason
  • Univadis Medical News
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In a letter to the Editor in  Nature Medicine , Australian scientists report immune response kinetics in a 47-year old patient with mild-to-moderate coronavirus (COVID-19) disease, who required hospitalisation but not ventilation.

Increased antibody-secreting cells (ASCs), follicular helper T cells (TFH cells), activated CD4+ T cells, CD8+ T cells, and immunoglobulin M (IgM) and IgG antibodies that bound to the COVID-19 virus, were detected in blood before symptomatic recovery. This immunological response persisted for seven days following full resolution of symptoms.

Key findings;

  • ASCs appeared and peaked on Day 8.
  • Circulating TFH occurred on Day 7, increasing at Day 8/9. 
  • Both ASCs and circulating TFH cells were prominently present during convalescence. 
  • Co-expression of CD38 and HLA-DR is a key phenotype of CD8+ viral response, which rapidly increased from Day 7 to Day 8/9, decreasing at Day 20. 
  • Co-expression of CD38 and HLA-DR on CD4+ T cells also increased between Day 7 and Day 9.
  • Rapid increases in activated CD38+HLA-DR+ T cells preceded the resolution of symptoms.
  • Minimal pro-inflammatory cytokines, predictive of severe clinical outcomes for influenza, were present even while symptomatic.

Immune parameters should be characterised in larger cohorts of people with COVID-19 with different disease severities to predict disease outcome, evaluate new interventions, and inform on protective vaccine candidates.