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1 Phys.org,2月21日,Why natural killer cells react to COVID-19 2022-03-03

Little has been known to date about how the immune system's natural killer(NK)cells detect which cells have been infected with SARS-CoV-2.An international team of scientist led by researchers from Karolinska Institutet now shows that NK cells respond to acertain peptide on the surface of infected cells.The study,which is published in Cell Reports,is an important piece of the puzzle in our understanding of how the immune system reacts to COVID-19. NK cells are white blood cells that are part of the innate immune system.Unlike cells in the adaptive immune defense,they are able to recognize and kill cancer cells and virus-infected cells immediately without having encountered them before.This ability is controlled by abalance between the NK cells'activating and inhibiting receptors,which can react to different molecules on the surface of other cells. The virus is revealed by apeptide A new study shows why certain NK cells are activated when encountering acell infected with SARS-CoV-2.The infected cells contain apeptide from the virus that triggers areaction in NK cells that carry aparticular receptor,NKG2A,able to detect the peptide. "Our study shows that SARS-CoV-2 contains apeptide that is displayed by molecules on the cell surface,"says Quirin Hammer,researcher at the Center for Infectious Medicine(CIM),Karolinska Institutet."The activation of NK cells is acomplex reaction,and here the peptide blocks the inhibition of the NK cells,which allows them to be activated.This new knowledge is an important piece of the puzzle in our understanding of how our immune system reacts in the presence of this viral infection." The study was amajor collaboration between Karolinska Institutet,Karolinska University Hospital and research laboratories and universities in Italy,Germany,Norway and the U.S.The first phase was to test their hypothesis using computer simulations that were then confirmed in the laboratory.The decisive phase was the infection of human lung cells with SARS-CoV-2 in acontrolled environment,whereupon the researchers could show that NK cells with the receptor in question are activated to agreater degree than the NK cells without it. 查看详细>>

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2 ScienceDaily,2月18日,T-cell responses may help predict protection against SARS-CoV-2 infection in individuals with and without cancer 2022-03-03

The efficacy of COVID-19 vaccines has been typically measured by antibody levels,but this may not be areliable metric,explained Laurence Zitvogel,MD,PhD,a professor at the Gustave Roussy Institute in Villejuif,France."Humoral immune responses monitored by antibody titers are only transiently helpful and not well correlated with protection,"she said."Antibodies do not last more than acouple of weeks in agiven individual post-infection or post-vaccination.Data show that antibodies against the SARS-CoV-2 spike protein have failed to predict actual protection against reinfection or breakthrough infection." Measuring antibody levels is away to monitor the presence and the activity of memory Bcells,which are immune cells that produce antibodies and represent the first arm of adaptive immunity.T cells,another type of immune cell,represent the second arm of long-term immunity and can be amplified during infection to kill infected cells directly. In this study,Zitvogel and colleagues examined whether T-cell responses could be areliable indicator of protection against SARS-CoV-2 infection in healthy individuals and in patients with cancer who had not been exposed to the virus during the first wave of the pandemic.Using blood samples collected prior to infection with SARS-CoV-2,they performed various in vitro experiments to assess how the polarity and repertoire of T-cell responses correlated with susceptibility to infection with SARS-CoV-2 during subsequent waves of the pandemic. T-cell polarity was assessed by identifying the types of cytokines--which are immune-stimulating proteins--released by the Tcells of each individual when exposed to aviral antigen.The release of the IL-2 cytokine was indicative of Th1 Tcells,whereas the release of the IL-5 cytokine indicated Th2 Tcells.Zitvogel and colleagues examined the makeup of each individual's T-cell pool to determine the proportion of Th1 and Th2 Tcells. They found pre-existing SARS-CoV-2-specific Tcell responses in about 20-25 percent of the population,both in healthy individuals and in cancer patients.In addition,they observed that the types of cytokines released by memory Tcells were associated with protection against SARS-CoV-2 infection.An imbalance between the IL-2 and IL-5 cytokines was associated with ahigher susceptibility to SARS-CoV-2 infection,with an IL-2/IL-5 ratio less than 1predicting infection,regardless of cancer status.This suggests that the relative levels of cytokines released by Tcells may provide insight into susceptibility to SARS-CoV-2 infection,explained Zitvogel. Further analysis revealed that Tcells from individuals who had developed aprimary infection,breakthrough infection post-vaccination,or reinfection with SARS-CoV-2 did not react to the receptor-binding domain of the spike protein,despite having immune responses against other regions of the viral genome.Zitvogel and colleagues proposed that the lack of reactivity to the spike receptor-binding domain may have made these individuals more susceptible to infection.Additionally,Zitvogel proposed that T-cell reactivity to the receptor-binding domain could even drive evolution of the spike protein,potentially contributing to the emergence of new viral variants. 查看详细>>

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3 Sciencedaily,2月17日,Study strengthens case that vitamins cannot treat COVID-19 2022-03-02

A new review of COVID-19 hospitalization data by researchers at The University of Toledo has found that taking immune-boosting supplements such as vitamin C,vitamin Dand zinc do not lessen your chance of dying from COVID-19. Early in the pandemic,healthcare providers tried avariety of micronutrients as potential therapies for the new illness.More recently,supplements have been promoted by some as an alternative to the safe and proven vaccines. However,Dr.Azizullah Beran said there's been little evidence those strategies work,despite the enduring interest in them. "A lot of people have this misconception that if you load up on zinc,vitamin Dor vitamin C,it can help the clinical outcome of COVID-19,"said Beran,an internal medicine resident at The University of Toledo College of Medicine and Life Sciences."That hasn't been shown to be true." Beran is the lead author on anew paper that significantly strengthens the emerging medical consensus that micronutrient supplements are not an effective treatment for COVID-19. He and his collaborators reviewed 26 peer-reviewed studies from around the globe that included more than 5,600 hospitalized COVID-19 patients.Their analysis found no reduction in mortality for those being treated with vitamin D,vitamin Cor zinc compared to patients who did not receive one of those three supplements. Their analysis did find that treatment with vitamin Dmay be associated with lower rates of intubation and shorter hospital stays,but the researchers say more rigorous study is needed to validate that finding. Vitamin Cand zinc were not associated with shorter hospital stays or lowering the chance apatient would be put on aventilator. While the study predominately looked at patients who were already sick and hospitalized with COVID-19 when given the supplements,researchers did analyze asmaller subset of individuals who had been taking vitamin Dprior to contracting the virus.They found no significant difference in the mortality rate of that population either. The paper is published in the journal Clinical Nutrition ESPEN. "It's important for people to understand that taking alot of these supplements does not translate into better outcomes,"said Dr.Ragheb Assaly,a UToledo professor of medicine and the paper's senior author."The other important message is that the answer to this disease is the vaccine.Micronutrient supplements will not offset the lack of vaccination or make you not need the vaccine." Researchers caution that the study shouldn't be interpreted as saying vitamin and mineral supplements are bad or should be avoided,but rather make it clear that they are not effective at preventing COVID-19 deaths. Beran and Assaly say it's possible that some COVID-19 patients who are malnourished or otherwise deficient in micronutrients may benefit from taking supplements,but that's because their bodies already lack essential nutrients--not because vitamin Dor vitamin Care effective against the virus. "What we're saying is this:If you don't medically need these supplements,don't take them thinking they're protective against COVID-19,"Beran said."They're not going to prevent you from getting it and they're not going to prevent you from dying." 查看详细>>

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4 Medicalxpress,2月16日,Study suggests increased risk of mental health disorders after COVID-19 infection 2022-03-02

A study published by The BMJ today finds that COVID-19 is associated with an increased risk of mental health disorders,including anxiety,depression,substance use,and sleep disorders,up to one year after initial infection. The findings suggest that tackling mental health disorders among survivors of COVID-19 should be apriority. Some studies have suggested that people with COVID-19 might be at increased risk of anxiety and depression,but they included only asmall selection of mental health outcomes and tracked patients over amaximum of six months. A comprehensive assessment of the mental health manifestations in people with COVID-19 at one year has not yet been undertaken. To address this,researchers used data from the US Department of Veterans Affairs national healthcare databases to estimate the risks of mental health outcomes in people who survived at least 30 days after apositive polymerase chain reaction(PCR)test result between March 2020 and January 2021. They identified data for 153,848 individuals and matched them to two control groups without COVID-19:5,637,840 contemporary controls and 5,859,251 historical controls who predated the pandemic. Participants were mostly white men with an average age of 63 years. The COVID-19 group was further divided into those who were or were not admitted to hospital during the acute phase of infection,and information was collected on potentially influential factors including age,race,sex,lifestyle,and medical history. The researchers then followed all three groups for one year to estimate the risks of aset of prespecified mental health outcomes,including anxiety,depression and stress disorders,substance use disorders,neurocognitive decline,and sleep disorders. Compared with the non-infected control group,people with COVID-19 showed a60%higher risk of any mental health diagnosis or prescription at one year(equivalent to an additional 64 per 1,000 people). When the researchers examined mental health disorders separately,they found that COVID-19 was associated with an additional 24 per 1,000 people with sleep disorders at one year,15 per 1,000 with depressive disorders,11 per 1,000 with neurocognitive decline,and 4per 1,000 with any(non-opioid)substance use disorders. 查看详细>>

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