Virus World

Michael Dahl walked into a UCSF clinic in San Francisco the other day, as he has done many times since the brain-sapping symptoms of long COVID changed his life nearly two years ago.

But this time, he and his doctors hoped it would be Dahl who will change long COVID. On Aug. 22, Dahl became the first person to receive an infusion of monoclonal antibodies aimed at treating the confounding condition that has impaired millions of people around the world. The clinical trial is one of only a small number testing a treatment or cure for the post-COVID condition, which is bafflingly complex, often robbing people of the ability to think clearly, wake up refreshed from sleep, exercise, or even breathe deeply. Yet, the repair that Dahl is testing is surprisingly simple. It rests on evidence that pieces of the coronavirus that causes COVID can linger in the body for years after infection. UCSF scientists want to see if annihilating those bits can improve or even erase the debilitating symptoms. “This is just hypothetical, but that is why we’re doing the study,” said Dr. Michael Peluso, principal investigator of the trial dubbed outSMART-LC. “We’re going to take the virus out of commission — we think — and see if people feel better.”

Researchers at four UC Health medical centers have begun recruiting participants for a Phase II clinical trial to test remdesivir. Physician-scientists at four University of California Health medical centers — UC San Diego Health, UC San Francisco, UC Irvine Health and UC Davis Health — have begun recruiting participants for a Phase II clinical trial to investigate the safety and efficacy of treating adult patients with COVID-19 with remdesivir, an antiviral drug that has shown activity in animal models and human clinical trials of SARS-CoV, MERS-CoV, Ebola, Marburg and other viruses.

Remdesivir is not approved by the U.S. Food and Drug Administration for treatment of any infection, but is undergoing clinical trials for treatment of multiple viral diseases, including COVID-19 (SARS-CoV-2) infections. The multicenter trial will be randomized, double-blind and placebo-controlled, with the capacity to enroll in up to 75 sites globally. The UC trial will begin with a small cohort of participants. All must be hospitalized patients with diagnosed COVID-19. All must be patients of UC San Diego Health or other participating UC Health systems.

Developed by Gilead Sciences, remdesivir belongs to a class of antiviral drugs that inhibit RNA-dependent RNA polymerase, an enzyme necessary for some RNA viruses like SARS-CoV-2 to replicate. Thus, inhibiting the enzyme may prevent viral replication in infected cells. The most commonly used antiviral drug in this class of drugs is acyclovir, used for the treatment of herpes simplex virus, chickenpox and shingles. The study will consist of a series of two-arm comparisons between different therapeutic agents and a placebo, with interim monitoring to introduce new arms as needed and to allow for early stoppage if any agents prove ineffective or unsafe. “Due to the evolving, fluid nature of this research and what we’re learning daily about the virus and about improving treatment, the trial is designed to be adaptive, to shift investigation to the most promising avenues,” said co-principal investigator Constance Benson, MD, professor of medicine at UC San Diego School of Medicine and an infectious disease specialist at UC San Diego Health.

Studies in living brain tissue found that specialized immune cells in the brain can harbor latent but replication-competent HIV.  As a part of its life cycle, human immunodeficiency virus-1 (HIV-1) inserts a copy of its DNA into human immune cells. Some of these newly infected immune cells can then transition into a dormant, latent state for a long period of time, which is known as HIV latency. Although current antiretroviral therapy (ART) against HIV can successfully block the virus from replicating further, it cannot eradicate latent HIV. If treatment is discontinued, the virus can rebound from latency and reignite the progression of HIV infection to AIDS. Scientists at the HIV Cure Center at the UNC School of Medicine, University of California, San Diego (UCSD), Emory University, and the University of Pennsylvania, have been searching for where exactly these latent cells are hiding in the body. Their newly reported studies indicate that brain microglial (BM)—specialized brain-resident immune cells with a decade-long lifespan—can serve as a stable viral reservoir for latent HIV. “We now know that microglial cells serve as a persistent brain reservoir,” said Yuyang Tang, PhD, assistant professor of medicine in the division of infectious diseases and member of the UNC HIV Cure Center. “This had been suspected in the past, but proof in humans was lacking. Our method for isolating viable brain cells provides a new framework for future studies on reservoirs of the central nervous system, and, ultimately, efforts towards the eradication of HIV.” Tang is first author of the team’s published paper in The Journal of Clinical Investigation, which is titled, “Brain microglia serve as persistent HIV reservoir despite durable antiretroviral therapy.”

HIV is a tricky virus to study. During infection, the virus specifically targets CD4+ lymphocytes which are the key coordinators of the immune response. Over time, the virus kills enough CD4+ cells to cause immunodeficiency. Past research has shown that latent HIV can hide within a few of the surviving CD4+ T cells throughout the body and the bloodstream. However, it’s been suspected that there are other viral reservoirs hidden within the central nervous system (CNS) in people with HIV who are receiving effective ART. But as the authors noted, “… rigorous evidence of viral persistence in the CNS cells of humans on durable suppressive ART is incomplete … Brain microglia (MG) may serve as a human immunodeficiency virus 1 (HIV) reservoir and ignite rebound viremia following cessation of antiretroviral therapy (ART), but they have yet to be proven to harbor replication-competent HIV. Unlike peripheral blood cells, it is extremely difficult to access and analyze brain tissues for the study of HIV reservoirs. Since these types of cells cannot be safely sampled in people taking ART, the potential viral reservoir in the brain has remained an enigma for many years. For their reported research the team first studied the brains of macaques infected with simian immunodeficiency virus (SIV), a virus that is closely related to HIV, from the Yerkes National Primate Research Center at Emory University to get a better understanding of how to extract and purify viable cells from primate brain tissue. The researchers used physical separation techniques and antibodies to selectively remove cells that were expressing microglial surface markers. Then, they isolated and separated the highly pure brain myeloid cells (BrMCs) from the CD4+ cells that were passing through the brain tissue. Using these techniques, researchers then obtained samples that were donated by HIV+ people (people with HIV; PWH) who were enrolled in “The Last Gift” Study at UCSD. As a part of this unique and important effort, altruistic HIV+ people, who are taking ART but suffering from other terminal illnesses, will their bodies to further the HIV research project.

“ … we first developed protocols to isolate highly pure populations of BrMCs and MG from the tissues of nonhuman primates (NHPs),” the authors explained. “We then adapted these protocols to the study of human brain tissues containing large numbers of viable cells after rapid autopsy to explore whether human BrMCs produce replication-competent HIV.” Co-author David Margolis, MD, the Sarah Kenan distinguished professor of medicine, microbiology & immunology, and epidemiology, further noted, “The samples are from people living with HIV, who are on therapy but facing a fatal disease of some kind. They were willing to not just donate their bodies to science, but also participate in the research program in the months leading up to their death. It’s an extraordinary program that made this critical research possible.” The scientists’ findings confirmed that MGs from an individual with HIV, being treated using ART, harbored replication-competent HIV. They acknowledged that although their study was limited by the small number of available samples from human donors on ART, they believe that the findings are consistent with NHP studies. “Our observations support the concept that brain MG are a stable reservoir of quiescent infection and may be a source of viral rebound upon treatment interruption,” they concluded. “Future efforts to clear HIV infection will have to include assessments of the persistence of HIV within CNS MG.” Now that the researchers know that latent HIV can take refuge in microglial cells in the brain, they are now considering plans to target this type of reservoir. Since latent HIV in the brain is radically different from the virus in the periphery, researchers believe that it has adapted special characteristics to replicate in the brain.

Reporting in their paper, the team noted, “Phenotyping studies characterized brain-derived virus as macrophage tropic based on the ability of the virus to infect cells expressing low levels of CD4. The lack of genetic diversity in virus from the brain suggests that this macrophage-tropic lineage quickly colonized brain regions.” NF-κB signaling is one of the critical signaling pathways that control HIV expression elsewhere in the body. When NF-κB signaling is “turned off,” HIV enters latency in the peripheral blood. However, latent HIV in the brain is not impacted by the activation of NF-κB signaling. Researchers are unsure why that is, but once an answer is found, they will be one step closer to knowing how to selectively target and eradicate the virus in the brain or peripheral blood. In addition to understanding the inner workings of the brain reservoir, the researchers are also trying to determine the true size of the latent HIV brain reservoir. “HIV is very smart,” said senior author Guochun Jiang, PhD, assistant professor in the UNC department of biochemistry and biophysics and member of the UNC HIV Cure Center. “Over time, it has evolved to have epigenetic control of its expression, silencing the virus to hide in the brain from immune clearance. We are starting to unravel the unique mechanism that allows latency of HIV in brain microglia”. Added Margolis, who is also the director of the UNC HIV Cure Center, “It is very hard to know how big the reservoir is. The problem with trying to eradicate HIV is like trying to eradicate cancer. You want to be able to get it all, so it won’t come back.”

Original research published in The Journal of Clin. Investigation (June 15, 2023):

https://doi.org/10.1172/JCI167417 

Novel spinal therapy/delivery approach prevented disease onset in neurodegenerative ALS disease model in adult mice and blocked progression in animals already showing disease symptoms. Writing in Nature Medicine, an international team headed by researchers at University of California San Diego School of Medicine describe a new way to effectively deliver a gene-silencing vector to adult amyotrophic lateral sclerosis (ALS) mice, resulting in long-term suppression of the degenerative motor neuron disorder if treatment vector is delivered prior to disease onset, and blockage of disease progression in adult animals if treatment is initiated when symptoms have already appeared.

Writing in Nature Medicine, an international team headed by researchers at University of California San Diego School of Medicine describe a new way to effectively deliver a gene-silencing vector to adult amyotrophic lateral sclerosis (ALS) mice, resulting in long-term suppression of the degenerative motor neuron disorder if treatment vector is delivered prior to disease onset, and blockage of disease progression in adult animals if treatment is initiated when symptoms have already appeared. The findings are published in the December 23, 2019 online issue of the journal Nature Medicine. Martin Marsala, MD, professor in the Department of Anesthesiology at UC San Diego School of Medicine and a member of the Sanford Consortium for Regenerative Medicine, is senior author of the study. 

ALS is a neurodegenerative disease that affects nerve cells in the brain and spinal cord. Motor neurons responsible for communicating movement are specifically harmed, with subsequent, progressive loss of muscle control affecting the ability to speak, eat, move and breathe. More than 5,000 Americans are diagnosed with ALS each year, with an estimated 30,000 persons currently living with the disease. While there are symptomatic treatments for ALS, there is currently no cure. The majority of patients succumb to the disease two to five years after diagnosis. There are two types of ALS, sporadic and familial. Sporadic is the most common form, accounting for 90 to 95 percent of all cases. It may affect anyone. Familial ALS accounts for 5 to 10 percent of all cases in the United States, and is inherited. Previous studies show that at least 200 mutations of a gene called SOD1 are linked to ALS. The SOD1 gene normally serves to provide instructions for making an enzyme called superoxide dismutase, which is widely used to break down superoxide radicals — toxic oxygen molecules produced as a byproduct of normal cell processes. Previous research has suggested that SOD1 gene mutations may result in ineffective removal of superoxide radicals or create other toxicities that cause motor neuron cell death, resulting in ALS.

The new approach involves injecting shRNA — an artificial RNA molecule capable of silencing or turning off a targeted gene — that is delivered to cells via a harmless adeno-associated virus. In the new research, single injections of the shRNA-carrying virus were placed at two sites in the spinal cord of adult mice expressing an ALS-causing mutation of the SOD1 gene, either just before disease onset or when the animals had begun showing symptoms....

Published in Nature Medicine (23 Dec. 2019):

https://doi.org/10.1038/s41591-019-0674-1