Feb. 8, 2022 -- It's a story of promise at a time of urgent need.
Scientists are optimistic about new evidence into what is causing long COVID, a panel of research experts brought together by the New York State Department of Health said.
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Interestingly, a study pre-print, which has not been peer reviewed, found dogs were accurate more than half the time in sniffing out long COVID, said Iwasaki, professor of immunobiology and developmental biology at Yale University.
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. Hornig is a doctor-scientist specializing in epidemiology at Columbia University in New York City.
"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, 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 in New York City. Reactivation of Epstein-Barr is one of four identifying signs of long COVID revealed in a Jan. 24 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, 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."
Forging Ahead on Future Research
It's clear there is more work to do. There are investigators working on banking tissue samples from people with long COVID to learn more, for example.
Also, finding a biomarker unique to long COVID could vastly improve the precision of diagnosing long COVID, especially if the dog sniffing option does not pan out.
Of the thousands of biomarker possibilities, Hornig said, "maybe that's one or two that ultimately make a real impact on patient care. So it's going to be critical to find those quickly, translate them, and make them available."
In the meantime, some answers might come from a large study sponsored by the National Institutes of Health. The NIH is funding this “Researching COVID to Enhance Recovery” project using $470 million from the American Rescue Plan. Investigators at NYU Langone Health are leading the effort and plan to share the wealth by funding more than 100 researchers at more than 30 institutions to create a "meta-cohort" to study long COVID. More information is available at recovercovid.org.
"Fortunately, through the global research effort, we are now really starting to expand our understanding of how long COVID manifests, how common it is and what the underlying mechanisms may be," Purpura said.