FIGURE 5.

The clinical samples of COVID-19 patients were tested by SP-NLISA. (A) 37 clinical serum samples from 4 severe and 16 mild COVID-19 patients were tested for NP antigen of SARS-CoV-2 by SP-NLISA. The result was represented as a mean of triplicate for each sample. (B) Correlation between SP-device and commercial microplate reader was analyzed by SPSS 18.0, which exhibited an excellent correlation and no significant difference (R² = 0.999, P < 0.001). (C) Identification of NP antigen in serum samples by Western blot. S1-D12, S2-D10, M11-D4 were COVID-19 patients’ samples collected at day 12, 10, or 4 post symptom onset. Positive control was a negative control sample with the addition of 1 μg/mL NP standard. Negative control 1 was the S4-D27 sample, while negative control 2 was a blood donor sample obtained from the Guangzhou blood center before the COVID-19 outbreak.