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Nitric oxide (NO) plays an important role in cardiovascular and immune systems. Quantification of blood nitrite and nitrate, two relatively stable metabolites of NO (generally as NO x ), has been acknowledged representing NO bioactivity partially. Dysregulation of NO x had been reported in SARS-CoV-2 infected populations, but whether patients recovered from COVID-19 disease present with restored NO x is unknown. In this study, serum NO 2 − and NO 3 − were quantified and analyzed among 109 recovered adults in comparison to a control group of 166 uninfected adults. Nitrite or nitrate levels were not significantly different among mild-, common-, severe- and critical-type patients. However, these recovered patients had dramatically lower NO 2 − and NO 2 − /NO 3 − than the uninfected group (p < 0.0001), with significantly higher NO 3 − levels (p = 0.0023) than the uninfected group. Nitrate and nitrite/nitrate were positively and negatively correlated with patient age, respectively, with age 65 being a turning point among recovered patients. These results indicate that low NO 2 − , low NO 2 − /NO 3 − and high NO 3 − may be a potential biomarker of long-term poor or irreversible outcomes after SARS-CoV-2 infection. It suggests that NO metabolites might serve as a predictor to track the health status of recovered COVID-19 patients, highlighting the need to elucidate the role of NO after SARS-CoV-2 infection.

Sera from a large cohort of COVID-19 convalescents in Wuhan were collected for evaluation of anti-SARS-CoV-2 humoral immunity -Anti-SARS-CoV-2 IgG was well maintained for 1 year in most convalescents and can potently neutralize the original strain and the B.1.1.7 variant -Varying degrees of immune escape was observed on the tested variants, especially on B.1.351 and B.1.617.2 variants -Sera from a few individuals showed remarkably broad neutralization potency against SARS-CoV-2 WT and variants ll www.cell.com/the-innovation