Is this why some people get sicker than others with Covid-19?

How come some people seem to be more sensitive to infections like Covid? It’s a question that’s perplexed scientists but now they think they know part of the answer at least: autoantibodies.

They may help us avoid infection and other conditions like diabetes and rheumatoid.

‘Proteins that attack us from within’ sounds more like a description for a new sci-fi film than a very real threat to humankind. But autoantibodies — also known as ‘rogue’ antibodies — are just that.

These immune cells are not good for us. Instead of protecting our bodies from infection, they attack healthy tissue and vital organs.

It is the cause of many autoimmune conditions, including rheumatoid and lupus. 

In each case the immune system misfires, mistaking a part of the body as foreign, and releases autoantibodies to go ‘on the attack’ — in the case of rheumatoid arthritis, it results in joint inflammation.

What is the reason why some people are more affected by Covid and other infections? It’s a question that’s perplexed scientists but now they think they know part of the answer at least: autoantibodies. Above is a stock photo [File photo]

Healthy immune systems can also make auto-antibodies. They were thought to be eliminated until around 20 years ago. However, scientists now know that certain autoantibodies can remain low in numbers among some individuals.

But as we age, their number increases (it’s thought they have some role in the ageing process).

Today immunologists are especially interested in how autoantibodies could play in Covid-19, and longer Covid.

As part of an international research project, Dr Jean-Laurent Casanova (an expert in human genetics) and his Rockefeller University team in the U.S. investigated the factors that can increase your risk of severe Covid-19.

The researchers found that Covid-19-infected patients had a higher rate of autoantibodies that those not. They also estimated that about a fifth of Covid-19 deaths could be attributed to autoantibodies.

The researchers found that antibodies can increase the severity of viral infections by blocking certain proteins that fight them.

They also believe that low levels of autoantibodies could help explain why some people suffer no — or mild — symptoms of Covid.

Another recent study has identified autoantibodies that are harmful in patients suffering from severe Covid-19. These include attacking blood clotting proteins and causing other harm.

This is what causes a variety of autoimmune diseases, including rheumatoid. In each case the immune system misfires, mistaking a part of the body as foreign, and releases autoantibodies to go ‘on the attack’ — in the case of rheumatoid arthritis, it results in joint inflammation

And since autoantibodies can be detected in blood tests, screening could help identify people with high levels who, therefore, may need preventive treatment — or spot the infected people who need early aggressive treatment.

Professor Adrian Liston (a Babraham Institute group leader) leads a program of research to study the immune responses of Covid-19-infected patients.

Although it’s too soon to know if autoantibodies are involved in long-term Covid or acute illness, he says that their presence is important.

‘It is certainly a very plausible pathway because we have evidence that autoantibodies can stick around for years or decades, unlike the virus, so it provides a good explanation for why long Covid symptoms persist after the virus is gone,’ he says.

But another possible explanation is that the virus ‘could initiate an inflammatory circuit, where inflammation breeds inflammation, which breeds more inflammation, even after the virus has gone — and we just don’t have enough research to say for sure’.

But it’s hoped that such research will pave the way for innovations in diagnostics and treatments. Professor Liston believes that within six months, a long-term diagnostic tool will be available for Covid using autoantibodies. After that, a long-term treatment will likely use autoantibodies to treat Covid.

Covid certainly sparked more interest in autoantibodies. However, these were also the focus of intensive research before the pandemic. This was partly due to concerns over the alarming rise in autoimmune disease.

There are four million people in the UK known to be living with at least one autoimmune condition but, according to Dr Louisa James, a senior lecturer in immunology at Queen Mary University of London, the prevalence is set to rise, partly because there are ‘probably more syndromes and conditions out there where our immune system is playing a role that was previously unrecognised’.

According to her, one recent study suggested that the autoimmune condition Fibromyalgia (which causes severe pain) may have been caused by antibodies that reduce pain tolerance.

Paul Morgan is a Cardiff University professor of immunology and excited about the potential future of autoantibody researchers. He believes that applying the knowledge gained from studying autoimmune diseases could lead to new treatment options for Covid-19 or long Covid.

If autoantibodies are indeed responsible for many of the symptoms of long Covid, ‘then you could use the sorts of approaches developed for autoimmune diseases — drugs that reduce the levels of harmful antibodies — to treat long Covid.

‘That’s why it’s important, it might give us a way of actually treating the disease — by targeting autoantibodies.’