According to a new study, IgA monoclonal antibodies — antibodies that are made by identical immune cells which are all clones belonging to a unique parent cell — particularly specific for Covid, can be effective in immunising the respiratory system against coronavirus.

The study, carried by researchers at MassBiologics of the University of Massachusetts Medical School, was published in the journal Nature Communications.

Binding affinity

The authors of the study described the discovery and characterisation of a cross-reactive human monoclonal antibody (MAB) to SARS-CoV-2 spike proteins that block ACE2 receptor binding on the mucosal tissue of the respiratory tract. And, this potentially prevents or limits SARS-CoV-2 infection-causing Covid-19 disease by blocking the receptor.

The type of antibody to treat coronaviruses was developed by MassBiologics 16 years ago during the SARS-CoV infection, the first severe acute respiratory syndrome caused by a novel coronavirus.

When SARS-CoV-2 was recognised and began to spread, the researchers realised that the first MAB might help with this new infection.

Researchers then initiated the resurrection of an old study by retrieving frozen hybridoma cells that had been developed 16 years earlier.

Although there was a 90 per cent similarity between the two coronaviruses, the monoclonal antibody demonstrated no binding to the current coronavirus. The researchers then evaluated another MAB from that earlier work, which was also only weakly effective.

The researchers suspected that similar anti-SARS-CoV-2 sIgA produced passive mucosal immunity in the respiratory tract, where Covid-19 disease is incredibly damaging.

Their approach worked, producing an antibody with binding affinity and neutralisation activity that was designated MAb362.

The researchers also found during their experiments that MAb362 shared a highly similar framework with MAb 80R, another SARS-CoV antibody with a crystal structure in complex with SARS-CoV.

Mark Klempner, MD, executive vice chancellor for MassBiologics and professor of medicine. Said in a statement: “We were excited to learn that antibodies to SARS-CoV-2 are more effective in binding to and neutralising the virus when they are in the sIgA isotype of antibody, compared to the usual circulating IgG antibodies.”

“So our search — which started during a coffee break conversation — has resulted in a unique IgA antibody that could potentially be applied through mucosal administration, in combination with other systemically administrated therapeutics for direct mucosal protection,” added Klempner.