All patients were confirmed to be SARS-CoV-2-positive using RNA-PCR with nasopharyngeal swabs at the time of study enrollment. The dilution of highly-neutralizing plasmas with poorly-neutralizing Rabbit Polyclonal to Cytochrome P450 7B1 plasmas relatively readily reduced neutralizing activity. The presence of good amounts of SARS-CoV-2-S1-binding antibodies does not serve as a surrogate ensuring the presence of good neutralizing activity. In Cobimetinib (racemate) selecting good COVID-19-convalescent plasmas, quantification of neutralizing Cobimetinib (racemate) activity in each plasma sample before collection and use is required. Subject terms:SARS-CoV-2, Viral infection, Immunotherapy == Introduction == SARS-CoV-2 causes severe, acute, and often fatal diseases in humans and is considered a global public threat14. As of November 7, 2020, more than 48.5 million COVID-19 cases have been reported in over 200 countries and more than 1,230,000 people have died3. Moreover, SARS-CoV-2 may persist in some convalescent COVID-19 survivors for long periods of time so that it is possible that SARS-CoV-2 infection could continue to recur, leading to the persistence of the pandemic5. Thus, development of effective vaccine(s) and specific therapeutics active against SARS-CoV-2 is of high priority; however, it may take at least a year or more to develop such effective vaccines and specific therapeutics. Since passive transfer of antibodies has been shown to protect nonhuman primates from the lethal challenges with Ebola virus, such plasma therapy has been used to treat patients with Ebola virus disease, severe acute respiratory syndrome (SARS) and H1N1 influenza69. Some anecdotal studies suggest some successes in mitigating symptoms and decreasing the number of deaths from such diseases including COVID-198,1012, but its approaches and potential efficacy have not been examined in rigorous clinical trials. Moreover, the possible adverse effects with such plasma transfer regarding SARS-CoV-2 infection have not been elucidated. Nevertheless, on August 23, 2020, the Federal Food and Drug Administration of the United States issued an Emergency Use Authorization (EUA) for emergency use of COVID-19 convalescent plasma for the treatment of hospitalized patients with COVID-1913. Thus, in the present study, in order to examine the presence and persistence of neutralizing activity in the plasma or serum samples obtained from 43 COVID-19-convalescent cases employing cell-based Cobimetinib (racemate) assays and various virologic endpoints. We found that certain IgG fractions from convalescent plasma or serum samples completely inhibited the infectivity, replication, and cytopathicity of SARS-CoV-2; however, the strength of neutralization significantly varied from one case to another. Of the 43 COVID-19-convalescent patients, 16 (37.2%) had no detectable neutralizing activity throughout the clinical course. Sixteen (40.7%) of the 27 patients who had neutralizing antibodies with neutralizing activity lost the activity within ~ one month (range 27 weeks), which Cobimetinib (racemate) may be related to viral reactivation, re-infection, or else5,14. The present data strongly suggest that neutralizing activity of plasma should be titrated prior to plasma collection and neutralizing plasma should be collected soon after the determination of neutralizing activity and that only plasma that contains good amounts of neutralizing antibodies should be administered to patients with COVID-19. == Results == == Clinical characteristics == Forty-three patients, RNA-PCR-confirmed, diagnosed to have COVID-19, and admitted to the Center Hospital of the National Center for Global Health & Medicine, participated in the present study. The median age of the patients was 53 (ranging from 28 to 83 years old). Three of the 43 patients showed minor symptoms at the onset (shown to be RNA-PCR test positive) and recovered shortly. Of the 43 patients, 21 (48.8%) had hypoxia and were diagnosed with pneumonia. Seven patients with pneumonia required positive-pressure ventilation, two of whom were also treated with ECMO (extracorporeal membrane oxygenation). All patients except for the two ECMO-treated cases recovered after 2 to 6 weeks of oxygen administration. Clinical profiles of patients enrolled in this study are shown in Table1and Supplementary TableS1. == Table 1. == Summary of the patient characteristics. *1Disease severity definitions. Mild: febrile or fatigue but no pneumonia identified; Moderate: febrile, fatigue, moderate pneumonia identified, but no dyspnea and no oxygen inhalation required; Severe: febrile, fatigue, dyspnea, Cobimetinib (racemate) severe pneumonia identified, and oxygen inhalation required; Critical: febrile, fatigue, severe dyspnea, critical pneumonia identified, and positive pressure ventilation plus extracorporeal membrane oxygenation (ECMO*2) required. *3For the detail of neutralizing activity, see Fig.3A. == Neutralizing activity of IgG fractions from COVID-19-convalescent plasma == IgG fractions were.