Melbourne experts uncover why COVID affects people differently

In a finding they hope will help ­refine vaccines against the mutating virus, University of Melbourne and Doherty Institute experts have produced one of the most detailed maps of how our immune system reacts.As well as revealing it takes multiple arms of the system to fight off COVID-19, the Melbourne team discovered the activation of one type of cell — known as T follicular helper cells — predicts whether a person will have strong immunity. By mapping the immune responses, it is hoped medical teams around the globe will not only be able to predict the effectiveness of current coronavirus vaccines, but also ­develop better jabs.Having analysed the complete responses in 85 Victorian cases, researchers found at least six key features dictated each case’s ­severity.One of the researchers, Oanh Nguyen, said of the team’s findings: “We know that all the cells, all the players, come together and work ­together to resolve this disease. That is really exciting.”

The researchers compared three levels of cases — where a person had a mild case and could recover at home, needed to be hospitalised, or had ­severe illness requiring intensive care.“When we compare the ­severe cases who were in ICU, to the mild and moderate, we found that the immune response — including innate cells, T-cells, B-cells as well as antibodies — everything was much heightened,” Dr Nguyen said.“We know what makes a good COVID-19 immune ­response to recover from mild, moderate or severe disease.“We will be using this knowledge to look at the vaccines and see how we respond to those.”In a stroke of luck, the Melbourne team led by Professor Katherine Kedzierska had since 2014 been undertaking one of world’s most in-depth studies into how the immune system responds to influenza. In a stroke of fortune, the Melbourne team led by Professor Katherine Kedzierska had been undertaking one of world’s most in-depth studies into the way the immune system responds to influenza since 2014 and was finalising its research when COVID-19 struck – meaning it was one of the only centres in the world already set up to examine the new virus.

Results published in the journal Cell Reports Medicine reveals overcoming SARS-CoV, as COVID-19 is officially known, is far more complex than beating a cold or the flu.Blood samples taken at different stages as patients battled and recovered from COVID-19 for up to 100 days showed innate cells, inflammatory cells, antibodies, T-cells, B-cells and T follicular helper cells must all come ­together to provide the best defence against the infection.Although the level of antibodies circulating after a person recovers from COVID-19 has been the focus for determining the protection offered by a vaccine, Dr Nguyen said the new insights could allow for more accurate predictions as well as targeted vaccines.“To recover from COVID-19 you need all these innate, adaptive antibodies, we need all these cells working together,” she said.“In the long term, you want those T-cells and B-cells, so that when you get infected again they are ready to fight. That is your long-term memory.“The antibody response is the hallmark of immunity to these viruses. And you also have to have these long-term T-cells and B-cells.“We think that with poor responses you see nothing. No antibodies, no activations of the acute cell populations. You might see elevated levels of cytokines, causing more damage to the tissue.”

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