ABSTRACT
BackgroundThe second wave of coronavirus disease 2019 (COVID-19) has been incessantly causing catastrophe worldwide, and the emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants causes further uncertainty regarding epidemic risk. Here, a novel strategy for the detection of SARS-CoV-2 variants using multiplex PCR coupled with MALDI-TOF MS was developed. MethodsPlasmids carrying gene sequences containing 9 mutation types in 7 mutated sites (HV6970del, N501Y, K417N, P681H, D614G, E484K, L452R, E484Q and P681R) in the receptor-binding domain of the spike protein of SARS-CoV-2 variants were synthesized. Using the nucleic acid sequence of SARS-CoV-2 nonvariant and a synthetic SARS-CoV-2-variant-carrying plasmid, a MALDI-TOF MS method based on the single-base mass probe extension of multiplex PCR amplification products was established to detect the above nine mutation types. The detection limit of this method was determined via the concentration gradient method. Twenty-one respiratory tract pathogens (9 bacteria, 11 respiratory viruses) and pharyngeal swab nucleic acid samples from healthy people were selected for specific validation. Sixteen samples from COVID-19 patients were used to verify the accuracy of this method. ResultsThe 9 mutation types could be detected simultaneously by triple PCR amplification coupled with MALDI-TOF MS. SARS-CoV-2 and all six variants (B.1.1.7, B.1.351, B.1.429, B.1.526, P.1 and B.1.617) could be identified. The detection limit for all 9 sites was 1.5x103 copies. The specificity of this method was 100%, and the accuracy of real-time PCR CT values less than 30 among positive samples was 100%. This method is open and extensible, and can be used in a high-throughput manner, easily allowing the addition of new mutation sites as needed to identify and track new SARS-CoV-2 variants as they emerge. ConclusionsMultiplex PCR-MALDI-TOF MS provides a new detection option with practical application value for SARS-CoV-2 and its variant infection. Key pointAn all-in-one SARS-CoV-2 variant identification method based on a multiplex PCR-MALDI-TOF MS system was developed. All of the SARS-CoV-2 variants can be identified based on 9 types of 7 mutated sites of RBD of spike protein using this method.
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Mutations of the coronavirus responsible for coronavirus disease 2019 (COVID-19) could impede drug development and reduce the efficacy of COVID-19 vaccines. Here, we developed a multiplexed Spike-ACE2 Inhibitor Screening (mSAIS) assay that can measure the neutralizing effect of antibodies across numerous variants of the coronaviruss Spike (S) protein simultaneously. By screening purified antibodies and serum from convalescent COVID-19 patients and vaccinees against 72 S variants with the mSAIS assay, we identified new S mutations that are sensitive and resistant to neutralization. Serum from both infected and vaccinated groups with a high titer of neutralizing antibodies (NAbs) displayed a broader capacity to neutralize S variants than serum with low titer NAbs. These data were validated using serum from a large vaccinated cohort (n=104) with a tiled S peptide microarray. In addition, similar results were obtained using a SARS-CoV-2 pseudovirus neutralization assay specific for wild-type S and four prevalent S variants (D614G, B.1.1.7, B.1.351, P.1), thus demonstrating that high antibody diversity is associated with high NAb titers. Our results demonstrate the utility of the mSAIS platform in screening NAbs. Moreover, we show that heterogeneous antibody populations provide a more protective effect against S variants, which may help direct COVID-19 vaccine and drug development. HighlightsO_LIDeveloped a high throughput assay to screen the neutralizing effect of antibodies across multiple SARS-CoV-2 Spike variants simultaneously. C_LIO_LICharacterized the heterogeneity of neutralizing antibodies produced in response to COVID-19 infection and vaccination. C_LIO_LIDemonstrated the capacity of Spike variants neutralization is associated with the diversity of anti-Spike antibodies. C_LI
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Strain-resource engineering is often considered as an important infrastructure of microbiology related research and industry. The western developed countries took the lead in establishing the classical microbial resource utilization method, and continuously improved the preservation system, species annotation technology and global sharing mechanism, which realized the expansion and reserve of biological resources since end of the 19th century. The rich and diversified germplasm resources, standard strains and production strains not only have important economic values, but also maintain the advantages of scientific research, bioeconomy (such as antimicrobial agents, vaccines, detection reagent development and standard development, etc.) and national security. Although there has been a lot of progress in related research in recent years, compared with developed countries, there is still a big gap in related fields in China. The investment and top-level design in this area lag far behind the western developed countries, and it is not commensurate with the current level of economic and social development in my country. Drawing lessons from the practice of WFCC and WDCM (World Data Center for Microorganisms, Global microbial data Center, affiliated to WFCC), for the purpose of collecting new clinical species/strains, this paper puts forward some suggestions on the identification, preservation and upload system of isolates.
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We constructed prokaryotic recombinant expression vector of P61 gene from Nocardia brasiliensis,expressing P61 protein with biological activity in E.coli,and lay a foundation for further studies related to P61.P61 gene was synthesized and cloned into an expression vector pET-30a(+).The recombinant vector was transformed into Escherichia coli BL21 and induced with IPTG.The production was analyzed with Western blot and the catalase activity of P61 was tested with Catalase Assay Kit.The protein of P61was successfully expressed in E.coli with solubility and high catalase activity,and could be identified by anti-N.brasiliensis sera from mice.The prokaryotic expression plasmid of protein P61 was constructed successfully and can be expressed efficiently in E.coli BL21 cells with higher catalase.
ABSTRACT
Objective To develop a one-step PCR assay for rapid discrimination of six Brucella species and some intraspecific biovars.Methods Using 6 pairs of primers in one-step PCR to differentiate six classical Brucella species and some biovar in ordinary PCR instrument.The tested strains including 27 reference strains of six Brucella species and 239 Brucella strains were estimated by the PCR assay and biological identification methods.Results The six Brucella species could be precisely differentiated by the onestep PCR assay from the tested strains.Five biovars and vaccine strain of B.suis species could be determined,and biovars 1,3,4 and biovars 2,5,6,7,9 of B.abortus species could be identified at the level of their biovar,moreover,biovars 1,2 and 3,and vaccine strain Rev 1 of B.melitensis species were also discriminated at the biovar and strain level.The accurate rates of the biological identification method and the PCR assay were 98.33％ and 100％ respectively.Conclusion One-step PCR assay was a rapid,specific,and low cost method for identification of Brucella species and discriminating biovars in ordinary PCR instrument.
