Objective To optimize the PCR primer sets for Simian virus 40 (SV40) detection and establish an assay method for SV40 which is of high sensitivity, strong specificity, broad applicability. Methods Two pairs of PCR primers were designed of based on 21 different SV40 strains genome by Primer Premier 5.00 software, and the features of two pairs of PCR primers were analyzed by Oligo software (version 6.71), conservative nucleotide of two pairs of PCR primers and the PCR amplification product were analyzed by DNAMAN software (version 6.0.40). Two pairs of new-built PCR primers were compared with those derived from China pharmacopoeia (Clip) in these aspects. The detection sensitivity of four pairs of PCR primers were analyzed using different SV40 DNA diluent as PCR template. The detection specificity of four pairs of PCR primers were analyzed using sterile water, Vero cell DNA, SV40 DNA as PCR template, respectively. Results The sequences of the new PCR primer sets VP1 and T are conservative for 21 Strains. The sequences of PCR primer sets GCVP1 and GCT are conservative for SV40 strains whose accession No. is J02400, NC_001669, AF316139 and AF316141. As far as the same diluent SV40 DNA template is concerned, the PCR amplification efficiency of PCR primer set VP1 and T is higher than that of PCR primer set GCVP1 and GCT. There are non-specific band in nucleic acid electrophoresis for amplification products of PCR primer sets GCVP1 and GCT, whereas there are no non-specific band in nucleic acid electrophoresis for amplification products of PCR primer sets VP1 and T. Conclusion The new assay method for SV40 nucleic acid sequence has many better qualities than those in Chp such as high sensitivity, strong specificity, broad applicability, conservation of primers and their amplification products and so on.

【Objective】 To investigate the trend of neutralizing antibody level in plasma donors who received the 3rd shot of inactivated novel coronavirus vaccine. 【Methods】 Three commercial ELISA kits for novel coronavirus neutralization antibody detection, manufactured by Company A, B and C, were chosen and screened by Pseudotype Neutralization Test from December 2021 to June 2022. A total of 410 plasma samples from 64 plasma donors who received the 3rd shot of inactivated novel coronavirus vaccine and there after donated plasma within six months were detected by the selected ELISA kit from July to October, 2022. The data were analyzed by Excel 2013 and SPSS 26 software. 【Results】 The high-throughput ELISA kit for SARS-CoV-2 neutralizing antibody detection, manufactured by Company A, was selected for further antibody titer detection. The mixed plasma titers were 1 337.34, 1 148.89, 852.19, 681.38, 556.44 and 457.19 U/mL from 1 to 6 months, respectively, after the 3rd shot of vaccine. The neutralizing antibody titer level began to increase around 7 days after the 3rd shot of vaccine injection and peaked (peak range: 264.07-2 208.39 U/mL, median: 569.34 U/mL) at 1 month (range: 9-43 days, median: 22 days), and then gradually decreased (P<0.05). 【Conclusion】 The neutralizing antibody titer of plasma donors who received the 3rd shot of inactivated novel coronavirus vaccine began to rise around 7 days after vaccination, which reached the peak value at around 1 month and then gradually decreased.