Fig. 1: Screening of human serum metabolites against SARS-CoV-2 infection.

a,b, Roles of human serum metabolites in SARS-CoV-2 infection. Schematic diagram of the study design (a). Incubation with human serum-derived filtrates impaired SARS-CoV-2 replication (b). Negative control: cells incubated with cell medium without SARS-CoV-2 infection. For the upper liquid group and lower liquid group, each dot represents one donor (n = 8 healthy donors). P = 0.0001 for upper liquid versus lower liquid, P < 0.0001 for cell medium versus upper liquid, cell medium versus lower liquid. c,d, Identification of the human serum metabolite(s) that prevent SARS-CoV-2 infection. Schematic diagram of the screening experimental design (c). The role of human serum metabolite(s) in SARS-CoV-2 infection (d). The amount of viral RNA was normalized to human GAPDH. The dot is the mean value. e, Assessing the antiviral activities of six metabolites from human serum by immunofluorescence staining. The nucleocapsid was stained with Alexa Fluor 546-conjugated anti-rabbit IgG (red). The nuclei were stained with To-Pro-3 iodide (blue). The stained cells were examined using a Zeiss LSM 880 meta confocal microscope in multitrack mode (i). Representative of three confocal immunofluorescence images from three biological replicates was shown. Scale bars, 20 μm. (ii) Mean fluorescence intensity in differently treated cells. Three images stained with nucleocapsid and Alexa Fluor 546-conjugated anti-rabbit IgG individually selected from three biological replicates were used to determine the mean fluorescence intensity with ImageJ (National Institutes of Health). AU, arbitrary units. P < 0.0001 for vehicle versus 1,5-AG, vehicle versus 1-napthol, vehicle versus 4-HA, vehicle versus 5-MT, vehicle versus CDCA, vehicle versus ellagic acid. f,g, Measurement of the half maximal inhibitory concentration (IC₅₀) of these candidate metabolites. Half maximal inhibitory concentrations of these metabolites (f). The viral loads in the cell supernatant were detected with a plaque-formation assay at 40 h post-infection. The gray dotted line represents the 50% inhibition ratio (n = 3 biological independent samples). Biological characterizations of candidate metabolic component(s) (g). Data are presented as the mean ± s.e.m. (b,e,f). Data were analyzed using a two-tailed Student’s t-test. P values were adjusted using Dunnett’s test. ^***P < 0.001, ^****P < 0.0001. Experiments were performed independently at least three biological replicates with comparable results.

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