Date: 23 June 2021
News Source: www.reuters.com
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.
Even mild cases of COVID-19 may lead to loss of brain tissue, according to findings from a long-term study involving 782 volunteers. As part of the ongoing UK Biobank study, participants underwent brain scans before the pandemic. For a before-and-after comparison, researchers invited 394 COVID-19 survivors to come back for follow-up scans as well as 388 healthy volunteers. Most of the COVID-19 survivors had only mild-to-moderate symptoms, or no symptoms at all, while 15 had been hospitalized. Among the COVID-19 survivors, researchers saw "significant" loss of gray matter in regions of the brain related to smell and taste - the left parahippocampal gyrus, left orbitofrontal cortex and left insula. Some of the affected brain regions are also involved in the memory of experiences that evoke emotional reactions, the researchers noted in a report posted on medRxiv on Tuesday ahead of peer review. The changes were not seen in the group that had not been infected. The authors said more research is needed to determine whether COVID-19 survivors will have issues in the longer term with their ability to remember emotion-evoking events. They also do not yet know whether the loss of gray matter is a result of the virus spreading into the brain, or some other effect of the illness.
The rapid spread of the extremely contagious Delta coronavirus variant, first identified in India, has driven a 50% rise in COVID-19 cases in England since May, researchers at Imperial College London said on Wednesday in their latest report from the REACT-1 prevalence survey. COVID-19 prevalence "is increasing exponentially, driven by younger ages ... and it appears to be doubling every 11 days. Clearly, that is bad news," Steven Riley, lead author of the report, told reporters. At the beginning of May, according to the researchers’ estimates, around 60% of positive COVID-19 swab tests were due to the Delta variant. By June 7, that had climbed to around 90%. Although the Delta variant has been shown to substantially reduce the effectiveness of one dose of vaccine against mild infection, two doses still provide good protection against severe disease, according to early evidence. On Friday, the World Health Organization said the Delta variant is becoming the globally dominant variant of the disease.
Instead of targeting the coronavirus with experimental drugs, UK researchers are trying a new approach. They are targeting infected cells to attempt to repair damage inflicted by the virus and prevent it from spreading. To make copies of itself, or replicate, inside infected cells, the virus activates a cellular response called the "unfolded protein response," explained Nerea Irigoyen of the University of Cambridge. In laboratory experiments, the researchers inhibited activation of this cellular response using experimental drugs. As a result, virus replication was prevented, according to a report published on Thursday in PLoS Pathogens. The unfolded protein response in infected cells "might be responsible at least to some extent" for some of the complications associated with COVID-19, such as respiratory distress and thickening and scarring of lung tissues, Irigoyen said. The approach must still be tested in animals and humans. But the research team is hoping that drugs that block the unfolded-protein response will not only reduce patients' viral burden but also relieve some of the symptoms associated with the infection. "This means that patients might have a better outcome and recover in less time," Irigoyen said.
Organ transplant recipients may not respond adequately to two-dose COVID-19 vaccines, but a third shot can sometimes be the charm, researchers said. While antibody responses after two doses of the mRNA vaccines from Pfizer/BioNTech (PFE.N), and Moderna (MRNA.O) are generally excellent, responses in transplant recipients may be "markedly" reduced, according to a report published on Monday in Annals of Internal Medicine. At Johns Hopkins Hospital in Baltimore, researchers gave a third dose to 30 organ transplant patients who had few or no antibodies after receiving the standard two vaccine doses. The third shot was given on average 67 days after the second, often from a different vaccine manufacturer. Two weeks after the third dose, 6 patients had gone from low antibody levels to high levels, another 6 had gone from having no detectable antibodies to having high levels, 2 had gone from no antibodies to low levels, and 16 still had no evidence of response to the vaccine. "This sets the stage for larger studies, where we can better understand which patients will respond well to this approach and who might need a different approach, as well as studies of B cells and T cells that will inform what is happening deeper than just measurable antibodies," said coauthor Dr. Dorry Segev.