Research on Ebola survivors has documented long-lasting inflammation and severe immune dysfunction 2 years after infection, for instance. And it’s well known that HIV-1 leads to aberrant immune responses, inflammation, and organ damage despite antiretroviral therapy, said Dr. Henrich, who leads a laboratory/research group that studies approaches to HIV-1 cure and PET-based imaging approaches to characterize viral reservoirs and immune sequelae.
Viral persistence, which can be difficult to measure, has also been documented in Ebola survivors. And in patients living with HIV-1, HIV-1 RNA and protein expression have been shown to persist, again despite antiretroviral therapy. The UCSF Long-Term Immunological Impact of Novel Coronavirus (LIINC) study, for which Dr. Henrich is the principal investigator, found spike RNA in colorectal tissue more than 22 months post COVID, and other research documented viral protein in gut tissue for up to 6 months, he said.
“I think we’re appreciating now, in at least the scientific and treatment community, that there’s a potential for ‘acute’ infections to exhibit some degree of persistence leading to clinical morbidity,” said Dr. Henrich, one of several speakers to describe reports of pathogen persistence. Regarding long COVID, its “etiology is likely heterogeneous,” he said, but persistence of SARS-CoV-2 “may lay behind” other described mechanisms, from clotting/microvascular dysfunction to inflammation and tissue damage to immune dysregulation.
Reactivation of existing latent viral infections in the setting of new acute microbial illness may also play an etiologic role in chronic illnesses, Dr. Henrich said. Epstein-Barr virus (EBV) reactivation has been shown in some studies, including their UCSF COVID-19 cohort, to be associated with long COVID.
“Physicians have been trained to be skeptical about the role [of latent viral infections],” Michael Peluso, MD, an infectious disease physician and assistant professor at UCSF, said during a talk on viral reactivation. This skepticism needs to be “reexamined and overcome,” he said.
Herpesviruses have frequently been associated with ME/CFS, he noted. And evidence of a strong association between EBV and multiple sclerosis came recently from a prospective study of 10 million military recruits that found a 32-fold increased risk of MS after EBV infection but no increase after infection with other viruses, Dr. Peluso and Dr. Henrich both noted.
Research needs, treatment trials
Research needs are vast: The need to learn more about the mechanisms of pathogen persistence and immune evasion, for instance, and the need for more biomarker studies, more imaging studies and tissue analyses, more study of microbiome composition and activity, and continued development and application of metagenomic next-generation sequencing.
Workshop participants also spoke of the need to better understand the molecular mimicry that can occur between pathogen-produced proteins and self-antigens, for instance, and the effects of inflammation and infection-related immune changes on neuronal and microglial function in the brain.
“We should perform similar forms of analysis [across] patients with different infection-associated chronic conditions,” said Amy Proal, PhD, president of the PolyBio Research Foundation, which funds research on infection-associated chronic infections. And within individual conditions and well-characterized study groups “we should perform many different forms of analysis … so we can define endotypes and get more solid biomarkers so that industry [will have more confidence] to run clinical trials.”
In the meantime, patients need fast-moving treatment trials for long COVID, long Lyme, and other infection-associated chronic illnesses, speakers emphasized. “We all agree that treatment trials are overdue,” said the NINDS’ Dr. Nath. “We can’t afford to wait for another decade until we understand all the mechanisms, but rather we can do clinical trials based on what we understand now and study the pathophysiology in the context of the clinical trials.”
Just as was done with HIV, said Steven G. Deeks, MD, professor of medicine at UCSF, researchers must “practice experimental medicine” and select pathways and mechanisms of interest, interrupt those pathways in a controlled manner, and assess impact. “Much of this can be done by repurposing existing drugs,” he said, like antivirals for persistent viral infection, EBV-directed therapies for EBV reactivation, anti-inflammatory drugs for inflammation, B–cell-directed therapies for autoantibodies, and antiplatelet drugs for microvascular disease.
When done correctly, he said, such “probe” studies can deepen mechanistic understandings, lead to biomarkers, and provide proof-of-concept that “will encourage massive investment in developing new therapies” for long COVID and other infection-associated chronic illnesses.
Trials of treatments for long COVID “are starting, so I’m optimistic,” said Dr. Deeks, an expert on HIV pathogenesis and treatment and a principal investigator of the Researching COVID to Enhance Recovery (RECOVER) study. Among the trials: A study of intravenous immunoglobulin (IVIG) for neurologic long COVID; a study of an anti-SARS-CoV-2 monoclonal antibody that can deplete tissue/cellular reservoirs of viral particles (replicating or not); and a study evaluating baricitinib (Olumiant), a Janus kinase inhibitor, for neurocognitive impairment and cardiopulmonary symptoms of long COVID.
Alessio Fasano, MD, professor of pediatrics at Harvard Medical School and professor of nutrition at the Harvard T.H. Chan School of Public Health, Boston, described at the workshop how he began investigating the use of larazotide acetate – an inhibitor of the protein zonulin, which increases intestinal permeability – in children with COVID-19 Multisystem Inflammatory Syndrome (MIS-C) after learning that SARS-CoV-2 viral particles persist in the gastrointestinal tract, causing dysbiosis and zonulin upregulation.
In an ongoing phase 2, double-blind, placebo-controlled trial, the agent thus far has expedited the resolution of gastrointestinal symptoms and clearance of spike protein from the circulation, he said. A phase 2 trial of the agent for pediatric patients with long COVID and SARS-CoV-2 antigenemia is underway. “What if we were to stop [chains of events] by stopping the passage of elements from the virus into circulation?’ he said.
In the realm of Lyme disease, a recently launched Clinical Trials Network for Lyme and Other Tick-Borne Diseases has awarded pilot study grants to evaluate treatments aimed at a variety of possible disease mechanisms that, notably, are similar to those of other chronic illnesses: persistence of infection or remnants of infection, immune dysregulation and autoimmune reactions, neural dysfunction, and gut microbiome changes. (Microclots and mitochondrial dysfunction have not been as well studied in Lyme.)
Current and upcoming studies include evaluations of transcutaneous auricular vagus nerve stimulation for those with persistent Lyme fatigue, transcranial direct current stimulation with cognitive retraining for Lyme brain fog, and tetracycline for PTLD, said Brian Fallon, MD, MPH, professor of clinical psychiatry at Columbia University, New York, who directs the Lyme & Tick-Borne Diseases Research Center and the coordinating center of the new network.
Columbia University Irving Medical Center
Dr. Brian Fallon
Moving forward, he said, it is important to loosen exclusion criteria and include patients with “probable or possible” Lyme and those with suspected infections with other tick-borne pathogens. All told, these patients comprise a large portion of those with chronic symptoms and have been neglected in an already thin research space, Dr. Fallon said, noting that “there haven’t been any clinical trials of posttreatment Lyme disease in ages – in 10-15 years.”
(PTLD refers to symptoms lasting for more than 6 months after the completion of standard Infectious Diseases Society of America–recommended antibiotic protocols. It occurs in about 15% of patients, said John Aucott, MD, director of the Johns Hopkins Lyme Disease Research Center, Baltimore, a member of the new clinical trials network.)