Researchers have mapped immune responses from one of Australia's first COVID-19 patients, showing the body's ability to fight the virus and recover from the infection. The study shows how the immune system of an otherwise healthy person was able to fight the virus, within days.
Published in Nature Medicine, researchers, from the University of Melbourne at the Peter Doherty Institute for Infection and Immunity in Australia, have found that while some people who have contracted COVID-19 experience serious symptoms, others are able to recover after a fairly short period of time.
Using information about one of Australia’s first COVID-19 patients, they were able to conduct a comprehensive case study. The female patient was experiencing mild-to-moderate symptoms of the infection when she sought care; but was noted to be healthy in all other respects. This was the reason researchers first became interested in finding out how an otherwise healthy adult’s immune system is able to react to an infection with new virus.
“We showed that even though COVID-19 is caused by a new virus, in an otherwise healthy person, a robust immune response across different cell types was associated with clinical recovery, similar to what we see in influenza,” says the study’s co-author Prof Katherine Kedzierska.
“This is an incredible step forward in understanding what drives recovery of COVID-19. People can use our methods to understand the immune responses in larger COVID-19 cohorts, and also understand what’s lacking in those who have fatal outcomes,” she adds.
The patient had sought specialised care four days after the onset of viral infection symptoms. These symptoms included lethargy, a sore throat, a dry cough, pleuritic chest pain, some shortness of breath and a fever. She was discharged from the hospital and entered herself into self-isolation for 11 days, after the onset of symptoms, and was found to be symptom-free by day 13.
For the study, researchers analysed blood samples that healthcare professionals had collected from the patient on four different occasions—on days 7, 8, 9 and 20, following the onset of symptoms.
“We looked at the whole breadth of the immune response in this patient using the knowledge we have built over many years of looking at immune responses in patients hospitalised with influenza,” explains the study’s co-author Dr Oanh Nguyen.
They found that during day-7 to day-9 following the onset of symptoms, there was an increase in immunoglobulins, the most common type of antibodies, rushing to fight the virus. This increase in immunoglobulins persisted up to day-20 after the onset of symptoms, according to the analysis.
At day-7 today-9 following the symptom onset, a large number of specialised helper T-cells, killer T-cells and B-cells—all of which are crucial immune cells -- were also active in the patient’s blood samples. This suggested that the patient’s body had been using many different ‘weapons’ effectively against the virus.
“Three days after the patient was admitted, we saw large populations of several immune cells, which are often a tell-tale sign of recovery during seasonal influenza infection, so we predicted that the patient would recover in 3 days, which is what happened,” notes Dr Nguyen.
The researchers also report that their investigation’s efficient timelines are much owed to the fact that the patient had enrolled into Sentinel Travellers and Research Preparedness for Emerging Infectious Disease (SETREP-ID). This is a research platform from the Peter Doherty Institute for Infection and Immunity.
“When COVID-19 emerged, we already had ethics and protocols in place so we could rapidly start looking at the virus and immune system in great detail,” says study’s co-author Dr Irani Thevarajan, praising the importance of SETREP-ID. It has already been established at a number of Melbourne hospitals and the researchers are now planning to roll out SETREP-ID as a national study.
“We hope to now expand our work nationally and internationally to understand why some people die from COVID-19, and build further knowledge to assist in the rapid response of COVID-19 and future emerging viruses,” Dr Thevarajan added.