Tissues were homogenized in TRNzol universal reagent by TGrinder H24(TIANGEN, China) and RNA was extracted using
Direct-Zol RNA Miniprep kit (ZYMO RESEARCH). Viral gRNA was reverse transcribed and amplified by
One Step PrimerScript RT-PCR Kit (TakaRa) using Ligtcycler 480II Real-Time PCR System (Roche) according to manufacturer’s instructions. Viral loads were calculated as viral RNA copies per mL or per mg tissue and the assay sensitivity was 100 copies. The target for amplification was SARS-CoV2 N (nucleocapsid) gene. The primers and probes for the targets were: N-F:5’- GGGGAACTTCTCCTGCTAGAAT-3’; N-R: 5’- CAGACATTTTGCTCTCAAGCTG -3’; N-P: 5’-VIC-TTGCTGCTTGACAGATT-BHQ1-3’
For quantification of viral loads by RT-PCR, a standard curve of Ct values to the copy number of viral RNA is generated with serial 10-fold dilutions of RNA transcribed from recombinant plasmid pcDNA3.1-nCoV N in vitro with a known copy number. The viral loads of each sample were converted with Ct value and the standard curve. Statistical analysis was performed by LightCycler 480 Software.
Li Y., Bi Y., Xiao H., Yao Y., Liu X., Hu Z., Duan J., Yang Y., Li Z., Li Y., Zhang H., Ding C., Yang J., Li H., He Z., Liu L., Hu G., Liu S., Che Y., Wang S., Li Q., Lu S, & Cun W. (2021). A novel DNA and protein combination COVID-19 vaccine formulation provides full protection against SARS-CoV-2 in rhesus macaques. Emerging Microbes & Infections, 10(1), 342-355.