Poster Presentation Asia-Pacific Vaccine and Immunotherapy Congress 2024

Dimeric IgA as an effective therapeutic strategy (#119)

Annemarie Laumaea 1 2 , Charley McKenzie-Kludas 3 , Laura D’Andrea 1 , Hor Hor 1 , Smitha Georgy 4 , Peter Newman 1 , Ewa Michalek 1 , Kanta Subbarao 3 5 , David Anderson 1 6 , Jennifer Barnes 1 , Heidi Drummer 1 7 8
  1. Burnet Diagnostics Initiative, Burnet Institute, Melbourne, Victoria, Australia
  2. Immunology, Monash University, Clayton, Victoria, Australia
  3. Peter Doherty Institute for Infection and Immunity, The University of Melbourne, Melbourne, VIC, Australia
  4. Melbourne Veterinary School, , The University of Melbourne, Werribee, VIC, Australia
  5. The Peter Doherty Institute for Infection and Immunity, WHO Collaborating Centre for Reference and Research on Influenza, Melbourne, VIC, Australia
  6. Walter and Eliza Hall Institute, Melbourne, VIC, Australia
  7. Department of Microbiology, Monash University, Clayton, VIC, Australia
  8. Department of Microbiology and Immunology, The University of Melbourne, Melbourne, VIC, Australia

There exists a paucity of effective immunotherapies targeting the mucosa that block entry of pathogens that invade through these sites. Immunoglobulin A (IgA), the second most abundant Ig class in circulation, after IgG, is an important antibody at the mucosa and can exist as monomeric and dimeric forms (dIgA) that predominate in systemic circulation, or secretory IgA (SIgA) found within secretions.  SIgA, a complex formed between dIgA and the secretory component of the polymeric Ig receptor (pIgR), primarily functions to immobilize and trap pathogens for various immune clearance mechanisms. Conversion of dIgA to SIgA confers dimeric IgA structural stability, protection from degradation within the harsh acidic environment at mucosal surfaces and importantly prevents transmission of mucosal pathogens. However, IgA has been underutilized as a therapeutic due to difficulty with generating sufficient yields.

 

Using recombinant technology, sequences of a potent SARS-CoV-2 IgG antibody were re-engineered from IgG into IgAs (dIgA and SIgA) and Immunoglobulins were expressed in high yields in Expi293 cells. RBD-ELISAs were performed to confirm antigen binding. In addition, flow cytometry and fluorescence microscopy were used to assess recognition of cell surface expressed pIgR. Transcytosis assays using polarized intestinal Caco-2 epithelial cells, stably expressing  pIgR, were performed to confirm transcytosis of dIgA in a transwell assay. Finally, pilot animal challenge studies were conducted in mice to ascertain the in vivo efficacy of dIgA. We demonstrate here recombinant dIgA’s specificity for its cognate receptor, pIgR, and its subsequent transcytosis across an intestinal epithelial cell transwell model. Furthermore, conversion of IgG to dIgA/SIgA was shown to improve neutralization potency against different SARS-CoV-2 variants of concern.  Importantly, preliminary mice challenge studies showed that recombinant dIgA delivered intravenously is able to significantly reduce virus titres in mice infected with SARS-CoV-2 compared to a control group, as well as reduce immune cell infiltration in the interstitial space of lungs from dIgA-treated animals, confirming protection and thus the feasibility of this approach.