It’s a story of promise at a time of urgent need.
They proposed many theories on what might be driving long COVID. A role for a virus “cryptic reservoir” that could reactivate at any time, “viral remnants” that trigger chronic inflammation, and action by “autoimmune antibodies” that cause ongoing symptoms are possibilities.
In fact, it’s likely that research will show long COVID is a condition with more than one cause, the experts said during a recent webinar.
People might experience post-infection problems, including organ damage that takes time to heal after initial COVID-19 illness. Or they may be living with post-immune factors, including ongoing immune system responses triggered by autoantibodies.
Determining the cause or causes of long COVID is essential for treatment. For example, if one person’s symptoms persist because of an overactive immune system, “we need to provide immunosuppressant therapies,” Akiko Iwasaki, PhD, said. “But we don’t want to give that to someone who has a persistent virus reservoir,” meaning remnants of the virus remain in their bodies.
Interestingly, a study preprint, which has not been peer reviewed, found dogs were accurate more than half the time in sniffing out long COVID, said Dr. Iwasaki, professor of immunobiology and developmental biology at Yale University, New Haven, Conn.
The dogs were tasked with identifying 45 people with long COVID versus 188 people without it. The findings suggest the presence of a unique chemical in the sweat of people with long COVID that could someday lead to a diagnostic test.
Viral persistence possible
If one of the main theories holds, it could be that the coronavirus somehow remains in the body in some form for some people after COVID-19.
Mady Hornig, MD, agreed this is a possibility that needs to be investigated further.
“A weakened immune response to an infection may mean that you have cryptic reservoirs of virus that are continuing to cause symptoms,” she said during the briefing. Dr. Hornig is a doctor-scientist specializing in epidemiology at Columbia University, New York.
“That may explain why some patients with long COVID feel better after vaccination,” because the vaccine creates a strong antibody response to fight COVID-19, Dr. Iwasaki said.
Researchers are unearthing additional potential factors contributing to long COVID.
Viral persistence could also reactivate other dormant viruses in the body, such as Epstein-Barr virus (EBV), said Lawrence Purpura, MD, MPH, an infectious disease specialist at New York Presbyterian/Columbia University. Reactivation of Epstein-Barr is one of four identifying signs of long COVID revealed in a Jan. 25 study published in the journal Cell.
Immune overactivation also possible?
For other people with long COVID, it’s not the virus sticking around but the body’s reaction that’s the issue.
Investigators suggest autoimmunity plays a role, and they point to the presence of autoantibodies, for example.
When these autoantibodies persist, they can cause tissue and organ damage over time.
Other investigators are proposing “immune exhaustion” in long COVID because of similarities to chronic fatigue syndrome, Dr. Hornig said.
“It should be ‘all hands on deck’ for research into long COVID,” she said. “The number of disabled individuals who will likely qualify for a diagnosis of [chronic fatigue syndrome] is growing by the second.”