Miniature organs help test potential coronavirus drugs; GI symptoms linked to severe Covid-19

The following is a roundup of some of the latest scientific studies on the novel coronavirus and efforts to find treatments and vaccines for Covid-19, the illness caused by the virus.

Miniature lungs, colons help test Covid-19 treatments

Tiny organ-like structures grown in the laboratory to behave like human lungs and colons can be used to rapidly screen drugs and identify those with potential as Covid-19 treatments, researchers reported on Wednesday in Nature.

Compared with traditional pre-clinical approaches, in which drugs are tested in cells from monkeys or from human cancer patients, these so-called organoids more faithfully mimic the complex cell types and structure of human tissues, according to Dr Shuibing Chen and Dr Robert Schwartz of Weill Cornell Medicine in New York.

Their team developed organoids containing types of lung and colon cells that are known to become infected in people with Covid-19.

In collaboration with teams at Columbia University and Icahn School of Medicine at Mount Sinai, they screened 1,200 FDA-approved drugs and found three that showed activity against the novel coronavirus, including the cancer drug imatinib, sold as Gleevec by Novartis. It is currently being tested in four different Covid-19 clinical trials.

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GI symptoms linked with more severe Covid-19

Gastrointestinal (GI) symptoms are associated with more severe Covid-19 and worse outcomes, two research teams reported on Monday, a reversal of earlier data that suggested the opposite was true.

One team reviewed 38 earlier studies of a total of more than 8,400 patients and found those with diarrhea were 63% more likely to develop severe Covid-19. Dr Subash Ghimire of Guthrie Robert Packer Hospital in Pennsylvania suggested that patients with diarrhea may have higher viral loads, which can potentially lead the body to fight back with more severe responses.

The other team studied 921 patients and found that the roughly 22% with at least one GI symptom had higher rates of hospital and intensive-care unit admissions and greater need for mechanical breathing assistance.

The more GI symptoms patients had, the more their risk for these outcomes increased, Dr Darbaz Adnan of Rush University Medical Center in Chicago reported. He said doctors evaluating Covid-19 patients need to bear in mind that GI symptoms may signal a markedly higher risk of a worsened disease course.

Both studies were presented at the American College of Gastroenterology virtual annual meeting.

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UK population with Covid-19 antibodies is shrinking

A new wave of coronavirus infections has been spreading in the UK, but the proportion of the population there with antibodies to the virus has been shrinking, potentially leaving more people vulnerable, new data show. In a report posted on Tuesday on medRxiv ahead of peer review, scientists at Imperial College London say that while 6% of the population had Covid-19 antibodies around the end of June, that rate fell to just 4.4% in September.

Antibodies are not the body's only line of defense. Also important are immune cells called T cells and B cells that stimulate antibody production.

"On the balance of evidence I would say, with what we know for other coronaviruses, it would look as if immunity declines away at the same rate as antibodies decline away, and that this is an indication of waning immunity at the population level," said study coauthor Wendy Barclay in a news briefing.

World Health Organisation spokesman Tarik Jasarevic said uncertainty over how long immunity would last and the fact most people had never had antibodies against this coronavirus shows the need to break transmission chains.

"Acquiring this collective immunity just by letting virus run through the population is not really an option," he told a UN briefing in Geneva.