New research suggests that instead of rapidly infecting large regions of the lung, severe acute respiratory coronavirus 2 (SARS-CoV-2) establishes itself in multiple smaller areas of the lung, hijacking the immune cells and using them to spread over a period of days or even weeks. The study authors said the severe complications of coronavirus disease 2019 (COVID-19) pneumonia may be related to the long course of the disease, rather than the severity.

Viruses that cause pneumonia, such as influenza, typically spread across large regions of the lung over a few hours, according to the study authors at Northwestern University. These bacteria are typically controlled either with antibiotics or by the body’s immune system within the first few days of illness, but the authors said COVID-19 pneumonia operates differently.

By slowly moving across the lung, they found that it leaves damage in its wake and continuously fuels the fever, low blood pressure, and damage to organs exhibited in patients with COVID-19.

The new study is unique because the authors had studied pneumonia for years before conducting this research, making them prepared to quickly collect fluid from the lungs of patients with COVID-19 and compare it with fluid collected from other ICU patients with pneumonia collected before the pandemic. Through this research, they demonstrated that pneumonia in patients with COVID-19 is different from other cases of pneumonia, according to a press release.

The investigators took cells from patients’ lung fluid and examined the RNA and the proteins expressed by those cells, which allowed them to identify how these immune cells drive inflammation.

“This level of resolution could never be achieved without directly sampling lung fluid,” said co-senior author Alexander Misharin, MD, PhD, in a press release.

Based on this analysis, the investigators identified important targets to treat severe SARS-CoV-2 pneumonia and minimize damage. Macrophages and T cells could be 2 critical targets because the study suggests that macrophages could be infected by SARS-CoV-2 and can contribute to spreading the infection through the lung.

Researchers at Northwestern Medicine plan to test an experimental drug to treat these targets in patients with COVID-19 pneumonia in a clinical trial early in 2021. According to a press release, the experimental drug quiets the inflammatory response of these immune cells and enabled initiation of the repair process.

The researchers said their ultimate goal is to make COVID-19 a mild disease, similar to a bad cold, although they cautioned that the virus is unlikely to completely disappear. Even with widespread vaccination, the study authors said it is likely to be similar to the influenza virus.

“Already, researchers at Northwestern and elsewhere are anticipating mechanisms by which this RNA virus, which mutates quickly, will evade current vaccines,” said senior co-author Ben Singer, MD, in a press release. “This study will help us develop treatments to reduce the severity of COVID-19 in those who develop it.”

REFERENCE
Why COVID-19 Pneumonia Lasts Longer, Causes More Damage Than Typical Pneumonia [news release]. EurekAlert; January 11, 2021. https://www.eurekalert.org/pub_releases/2021-01/nu-wcp011121.php. Accessed January 13, 2021.