Virus World

The emergence of SARS-CoV-2 has led to a global health crisis that, in addition to vaccines and immunomodulatory therapies, calls for the identification of antiviral therapeutics. The papain-like protease (PLpro) activity of nsp3 is an attractive drug target as it is essential for viral polyprotein cleavage and for deconjugation of ISG15, an antiviral ubiquitin-like protein. We show here that 6-Thioguanine (6-TG), an orally available and widely available generic drug, inhibits SARS-CoV-2 replication in Vero-E6 cells with an EC50 of approximately 2 μM. 6-TG also inhibited PLpro-catalyzed polyprotein cleavage and de-ISGylation in cells and inhibited proteolytic activity of the purified PLpro domain in vitro. We therefore propose that 6-TG is a direct-acting antiviral that could potentially be repurposed and incorporated into the set of treatment and prevention options for COVID-19

Published in IScience (Oct. 2, 2021):

https://www.cell.com/action/showPdf?pii=S2589-0042%2821%2901181-0 

The aim of this study is to evaluate if the sweat produced by COVID-19 persons (SARS-CoV-2 PCR positive) has a different odour for trained detection dogs than the sweat produced by non COVID-19 persons. The study was conducted on 3 sites, following the same protocol procedures, and involved a total of 18 dogs. A total of 198 armpits sweat samples were obtained from different hospitals. For each involved dog, the acquisition of the specific odour of COVID-19 sweat samples required from one to four hours, with an amount of positive samples sniffing ranging from four to ten. For this proof of concept, we kept 8 dogs of the initial group (explosive detection dogs and colon cancer detection dogs), who performed a total of 368 trials, and will include the other dogs in our future studies as their adaptation to samples scenting takes more time.

The percentages of success of the dogs to find the positive sample in a line containing several other negative samples or mocks (2 to 6) were 100p100 for 4 dogs, and respectively 83p100, 84p100, 90p100 and 94p100 for the others, all significantly different from the percentage of success that would be obtained by chance alone. We conclude that there is a very high evidence that the armpits sweat odour of COVID-19+ persons is different, and that dogs can detect a person infected by the SARS-CoV-2 virus.

Preprint Available in bioRxiv (June 5, 2020):

https://doi.org/10.1101/2020.06.03.132134

University of Pittsburgh School of Medicine scientists have isolated the smallest biological molecule to date that completely and specifically neutralizes the SARS-CoV-2 virus, which is the cause of COVID-19. This antibody component, which is 10 times smaller than a full-sized antibody, has been used to construct a drug — known as Ab8 — for potential use as a therapeutic and prophylactic against SARS-CoV-2. The researchers report today (September 14, 2020) in the journal Cell that Ab8 is highly effective in preventing and treating SARS-CoV-2 infection in mice and hamsters. Its tiny size not only increases its potential for diffusion in tissues to better neutralize the virus, but also makes it possible to administer the drug by alternative routes, including inhalation. Importantly, it does not bind to human cells — a good sign that it won’t have negative side-effects in people. Ab8 was evaluated in conjunction with scientists from the University of North Carolina at Chapel Hill (UNC) and University of Texas Medical Branch (UTMB) at Galveston, as well as the University of British Columbia and University of Saskatchewan.

“Ab8 not only has potential as therapy for COVID-19, but it also could be used to keep people from getting SARS-CoV-2 infections,” said co-author John Mellors, M.D., chief of the Division of Infectious Diseases at UPMC and Pitt. “Antibodies of larger size have worked against other infectious diseases and have been well tolerated, giving us hope that it could be an effective treatment for patients with COVID-19 and for protection of those who have never had the infection and are not immune.” The tiny antibody component is the variable, heavy chain (VH) domain of an immunoglobulin, which is a type of antibody found in the blood. It was found by “fishing” in a pool of more than 100 billion potential candidates using the SARS-CoV-2 spike protein as bait. Ab8 is created when the VH domain is fused to part of the immunoglobulin tail region, adding the immune functions of a full-size antibody without the bulk. Abound Bio, a newly formed UPMC-backed company, has licensed Ab8 for worldwide development. Dimiter Dimitrov, Ph.D., senior author of the Cell publication and director of Pitt’s Center for Antibody Therapeutics, was one of the first to discover neutralizing antibodies for the original SARS coronavirus in 2003. In the ensuing years, his team discovered potent antibodies against many other infectious diseases, including those caused by MERS-CoV, dengue, Hendra and Nipah viruses. The antibody against Hendra and Nipah viruses has been evaluated in humans and approved for clinical use on a compassionate basis in Australia.

Clinical trials are testing convalescent plasma — which contains antibodies from people who already had COVID-19 — as a treatment for those battling the infection, but there isn’t enough plasma for those who might need it, and it isn’t proven to work. That’s why Dimitrov and his team set out to isolate the gene for one or more antibodies that block the SARS-CoV-2 virus, which would allow for mass production. In February, Wei Li, Ph.D., assistant director of Pitt’s Center for Therapeutic Antibodies and co-lead author of the research, began sifting through large libraries of antibody components made using human blood samples and found multiple therapeutic antibody candidates, including Ab8, in record time. Then a team at UTMB’s Center for Biodefense and Emerging Diseases and Galveston National Laboratory, led by Chien-Te Kent Tseng, Ph.D., tested Ab8 using live SARS-CoV-2 virus. At very low concentrations, Ab8 completely blocked the virus from entering cells. With those results in hand, Ralph Baric, Ph.D., and his UNC colleagues tested Ab8 at varying concentrations in mice using a modified version of SARS-CoV-2. Even at the lowest dose, Ab8 decreased by 10-fold the amount of infectious virus in those mice compared to their untreated counterparts. Ab8 also was effective in treating and preventing SARS-CoV-2 infection in hamsters, as evaluated by Darryl Falzarano, Ph.D., and colleagues at the University of Saskatchewan. Sriram Subramaniam, Ph.D., and his colleagues at the University of British Columbia uncovered the unique way Ab8 neutralizes the virus so effectively by using sophisticated electron microscopic techniques.

Original study published in Cell (August 31, 2020):

https://doi.org/10.1016/j.cell.2020.09.007

The fast-growing list of possible treatments for the novel coronavirus includes an unlikely candidate: famotidine, the active compound in the over-the-counter heartburn drug Pepcid. On 7 April, the first COVID-19 patients at Northwell Health in the New York City area began receiving famotidine intravenously, at nine times the heartburn dose. Unlike other drugs the 23-hospital system is testing, including Regeneron’s sarilumab and Gilead Science’s remdesivir, Northwell kept the famotidine study under wraps to secure a research stockpile before other hospitals, or even the federal government, started buying it. “If we talked about this to the wrong people or too soon, the drug supply would be gone,” says Kevin Tracey, a former neurosurgeon in charge of the hospital system’s research.

As of Saturday, 187 COVID-19 patients in critical status, including many on ventilators, have been enrolled in the trial, which aims for a total of 1174 people. Reports from China and molecular modeling results suggest that the drug, which seems to bind to a key enzyme in the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), could make a difference. But the hype surrounding hydroxychloroquine and chloroquine—the unproven antimalarial drugs touted by President Donald Trump and some physicians and scientists—has made Tracey wary of sparking premature enthusiasm. He is tight-lipped about famotidine’s prospects, at least until interim results from the first 391 patients are in. “If it does work, we’ll know in a few weeks,” he says.

A globe-trotting infectious disease doctor named Michael Callahan was the first to call attention to the drug in the United States. Callahan, who is based at Massachusetts General Hospital in Boston and has extensive connections in the biodefense world, has spent time in disease hot zones around the world, including the 2003 outbreak of another coronavirus disease, SARS, in Hong Kong. In mid-January, he was in Nanjing, China, working on an avian flu project. As the COVID-19 epidemic began exploding in Wuhan, he followed his Chinese colleagues to the increasingly desperate city.