US Scientists Say Distinct Immune System Pattern in Severe Covid-19 Patients Identified

Researchers studying the immune responses of 125 hospitalised COVID-19 patients have identified distinct immune profiles, or "immunotypes", and showed how these were linked to disease severity, an advance which may aid in the development of novel therapeutics against the disease.

According to the study, published in the journal Science, whether there is a common profile of immune dysfunction in critically ill COVID-19 patients remains unknown.

"By localizing patients on an immune topology map, we can begin to infer which types of therapeutic interventions may be most useful in specific patients," said the scientists, including Divij Mathew from the University of Pennsylvania in the US.

To date, the researchers said studies investigating this are limited, reporting on single patients or small cohorts.

They said as the global COVID-19 pandemic continues, scientists worldwide continue to investigate the characteristics of the human immune response in fighting it.

Seeking to expand on findings reported so far, and also to better connect immune features in COVID-19 patients with clinical features of disease, Mathew and his colleagues assessed the cells of the immune system in 125 COVID-19 patients at two points during their first week of hospitalisation.

The researchers said they used a method called flow cytometry, which is a technique used to detect and measure physical and chemical characteristics of a population of cells, to assess the patient immune cells.

They said the study also collected clinical data on the patient cohort.

Combining the flow cytometric and clinical data, the study reported several key findings, including that a defining feature of COVID-19 disease in this group is variability in their own immune response.

It also noted that certain stable immune response signatures in subsets of their patients, which changed over time in consistent ways.

According to the researchers, some of these patterns, like impaired activation of a part of the immune system called the CD8 T cells, were associated with worse disease outcomes.

The scientists defined three of these immune response signatures, or immunotypes, associated in the patients with poor clinical trajectories versus improving health.

"These immunotypes may reflect fundamental differences in the ways patients respond to SARS-CoV2 infection," they said.

The scientists believe their findings "provoke the idea of the tailoring clinical treatments or future immune-based clinical trials to patients whose immunotype suggests greater potential benefit."