Outbreak response in action: Centers for Disease Control and Prevention (CDC) staff support the COVID-19 response in the CDC’s Emergency Operations Center (EOC). [CDC; photo credit James Gathany]

Researchers at the Peter Doherty Institute for Infection and Immunity in Australia have mapped immune responses in a patient in response to COVID-19 infection, demonstrating the body’s ability to fight the virus and recover from the infection. The team tested blood samples taken from one of Australia’s first cases of COVID-19, at four different time points during the infection. “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 hospitalized with influenza,” said Oanh Nguyen, PhD, co-author of the researchers report, which is published in Nature Medicine.

“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,” added University of Melbourne Professor Katherine Kedzierska, PhD, a laboratory head at the Doherty Institute. Nguyen said the report is the first to describe broad immune responses to COVID-19. The researchers’s findings are reported in a paper titled, “Breadth of concomitant immune responses prior to patient recovery: a case report of non-severe COVID-19.”

The patient was an otherwise healthy, non-smoking woman, aged 47 years, from Wuhan, Hubei province, in China, who had travelled to Australia 11 days previously, and presented to an emergency department in Melbourne, Australia. Her symptoms, which had started four days before she went to hospital, included lethargy, sore throat, dry cough, pleuritic chest pain, mild dyspnea and subjective fevers.

“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 three days, which is what happened,” Nguyen said. The SARS-CoV-2 virus was detected in nasopharyngeal, sputum and fecal samples from the patient on presentation at the hospital on day four, and again on days 5–6, but was undetectable from day 7. She was discharged to home isolation on day 11. Her symptoms resolved completely by day 13, and she remained well at day 20, “with progressive increases in plasma SARS-CoV-2-binding IgM and IgG antibodies from day 7 until day 20.”

“We have provided evidence on the recruitment of immune cell populations (ASCs, TFH cells and activated CD4+ and CD8+ T cells), together with IgM and IgG SARS-CoV-2-binding antibodies, in the patient’s blood before the resolution of symptoms,” the authors wrote. “Collectively, our study provides novel contributions to the understanding of the breadth and kinetics of immune responses during a non-severe case of COVID-19 … We propose that these immune parameters should be characterized in larger cohorts of people with COVID-19 with different disease severities to determine whether they could be used to predict disease outcome and evaluate new interventions that might minimize severity and/or to inform protective vaccine candidates.”

The patient was enrolled for testing through a coronavirus substudy that is part of the Sentinel Travelers and Research Preparedness for Emerging Infectious Disease (SETREP-ID) initiative, which is led by Royal Melbourne Hospital Infectious Diseases physician Irani Thevarajan, MD, at the Doherty Institute. SETREP-ID is a platform that enables a broad range of biological sampling to take place in returned travelers in the event of a new and unexpected infectious disease outbreak, which is exactly how COVID-19 started in Australia. “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,” Thevarajan said. “Already established at a number of Melbourne hospitals, we now plan to roll out SETREP-ID as a national study.”

Thevarajan commented that according to current estimates more than 80% of COVID-19 cases are mild-to-moderate, and understanding the immune response in these mild cases represents key research. “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,” she stated.

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