Objective To evaluate the immunogenicity of prototype strain,Beta strain,Gamma strain and Delta strain of SARS-CoV-2 inactivated vaccines in rats.Methods Five female Wistar rats were immunized with SARS-CoV-2 inactivated vaccines of prototype,Beta,Gamma and Delta strains through thigh muscle twice at an interval of 14 d,with an immunization dose of 3 μg virus protein/(0.5 mL per rat).Serum samples were collected and isolated by vein 14,28 and 42 d after the first immunization.The serum IgG antibody levels were detected by indirect ELISA,the titers of serum neutralizing antibody were measured by microneutralization,and the antigenic ratios of the serum neutralizing antibody titers were calculated to evaluate the antigenicity difference between different strains.Results at 14 d after the first immunization,IgG antibodies against four strains of virus were detected in all immunized serum samples.The levels of IgG antibodies increased by more than 10 times at 28 d compared with those at 14 d,and decreased slightly at 42 d.At 14 d after the first immunization,all the neutralizing antibodies against the four strains were positive in the serum of rats immunized with prototype strain or Delta strain vaccine;In the serum samples of rats immunized with Beta and Gamma strains,all the neutralizing antibodies against Beta and Gamma strains were positive,while some neutralizing antibodies against prototype or Delta strains were positive.At 28 d after the first immunization,the neutralizing antibodies in the immune serum of the four strains were positive,and the titers of neutralizing antibodies were significantly higher than those at 14 d;The neutralizing antibody titers were slightly lower at 42 d after the first immunization than 28 d.There was small difference in the antigenicity between Beta and Gamma,prototype and Gamma,but significant difference in the antigenicity between prototype and Beta strains.Conclusion The prototype strain,Beta strain,Gamma strain and Delta strain of SARS-CoV-2 inactivated vaccines can stimulate rats to produce neutralizing antibodies with high titer,while the immunogenicity has difference.

Objective To explore the factors affecting the stability of high concentration variable domain of heavy-chain antibody-Fc(VHH-Fc) fusion protein.Methods Three groups of forced degradation experiments,shaking,light and 40℃ high temperature were set up.Differential scanning fluorimetry,dynamic light scattering(DLS) and ultra performance liquid chromatography-mass spectrometry(UPLC-MS) were used to detect the effects of the three forced degradation conditions on the conformational stability,colloidal stability,average hydrodynamic diameter and post-translational modifications of high concentration VHH-Fc fusion protein.Results Under the light condition,the onset temperature of unfolding(T_(onset)),melting temperature(T_m) and aggregation onset temperature(T_(agg)) of high concentration VHH-Fc fusion protein decreased the most,and the oxidation ratio of Met160 and Met266 increased significantly.Under the condition of shaking,the variation of the diffusion interaction parameter(k_D) and the average hydrodynamic diameter was the largest.Conclusion Light can significantly reduce the conformational stability of high concentration VHH-Fc fusion protein and induce methionine oxidation.Shaking has the most significant effect on its colloidal stability and promotes aggregation.

Objective To compare the effects of different signal peptides on the secretion and expression of SARS-CoV-2S1,receptor binding domain(RBD) and RBD dimer proteins in Expisf9 insect cells.Methods The gene sequences of three proteins,SARS-CoV-2 S1(M1-E661),RBD(R319-P545) and RBD dimer(R319-K537 tandem),were selected and divided into 25 groups according to the different N-terminal signal peptide sequences(Endo,honeybee melittin(HBM),GP64,GP67,chitinase(Chi) and HIV-ENV) and C-terminal label sequences.25 recombinant baculoviruses were constructed by Bac-to-Bac system,and 25 groups of tertiary strain banks were prepared.B2 and C4 viruses were inoculated to logarithmic prestage cells(2.8 × 10~6 cells/mL) and logarithmic metaphase cells(1.2 × 10~7 cells/mL),respectively.The viruses of each group were cultured to 100 mL(500 mL shaker) for protein expression,and samples were taken for SDSPAGE electrophoresis,Western-blot and ELISA detection.Two groups with higher expression levels of S1,RBD and RBD dimer proteins were selected for repeated verification.Results When B2 and C4 were inoculated to high cell density,the secretion expression level showed no increase,while there were significant difference between 4 and 5 d after inoculation.The expression level of A7(Endo-S1-tag) was significantly lower than that of A9(HIV-ENV-S1-tag),the expression level of A4(Gp67-S1-tag) was the highest,and the secreted expression level of A1(Endo-Endo-Sl-tag) was significantly lower than that of A7(Endo-S1-tag).The secretion and expression of B6(HIV-ENV-RBD-tag) was signifi-cantly higher than that of B4(Gp67-RBD-tag) and other signal peptide groups,and C4(Gp67-RBD-dimer-tag) expression was significantly higher than that of C3(Gp64-RBD-dimer-tag).Two groups with high expression of each protein were selected separately for repeated verification(A4,A9;B4,B6;C3,C4) and the results showed that A4,B6 and C4 had the highest secretion expression levels.Conclusion The signal peptide for the highest secretion expression of S1 and RBD dimer proteins is the same,which is GP67 signal peptide,while the most suitable signal peptide for RBD protein is HIV-ENV,indicating that the N-terminal sequence can affect protein secretion,signal peptide sequence is universal to a certain extent,but is also related to the target protein sequence to be expressed.

Objective To construct the recombinant adenovirus vector pAd-σC for the expression of avian reovirus(ARV)aC protein and to detect its effects on the proliferation of hepatocellular carcinoma cells,in order to build up a basis for the development of novel anti-tumor vaccines.Methods The recombinant shuttle vector pShuttle-σC was constructed by PCR amplification of ARV σC gene,and then transformed into competent BJ5183 cells containing the adenovirus vector pAdessy-1.The recombi-nant adenovirus vector pAd-σC was obtained by homologous recombination,and the virus was packaged in HEK293 cells.The virus titer was measured by TCID_(50),the expression of σC protein was determined by Western blot and ELISA,and the effect of virus on the proliferation of human hepatocellular carcinoma cells SMMC7721 was detected by CCK-8 assay.Results The recombinant shuttle vector pShuttle-σC was confirmed to be constructed correctly by double enzyme digestion and sequen-cing,and the recombinant adenovirus vector pAd-σC was constructed correctly as identified by colony PCR.σC protein was successfully expressed in hepatocellular carcinoma cells SMMC7721.The recombinant adenovirus Ad-σC had a titer of 10~(7.5)/0.1 mL,which inhibited the proliferation of hepatocellular carcinoma cells SMMC7721.Conclusion The recombinant adenovirus vector pAd-trC containing ARV σC gene was successfully constructed,and its inhibitory effect on tumor cell proliferation was preliminarily analyzed,which lays a foundation for revealing the molecular mechanism of ARV oncolytic effect and further developing novel anti-tumor biological preparation.

Objective To analyze the genetic characteristics of the entire VP1 gene of Coxsackievirus A16(CVA16) strains isolated from the feces of patients with hand,foot and mouth disease(HFMD) in Yunnan Province in 2019.Methods The virus was isolated from human embryonic lung diploid fibroblast(KMB-17) cells and African green monkey kidney(Vero)cells,and the primers for the complete VP1 gene sequence of CVA16 were designed.The target fragment was amplified by RT-PCR and sequenced;the complete VP1 sequence was analyzed by softwares such as MEGA 7.0 and Geneious 9.0.2.Results A total of 26 CVA16 strains were isolated,including eight KMB-17 isolates and 18 Vero isolates.Twenty CVA16isolates were randomly selected for analysis,and three isolates were found to have Bla and 17 B1b genotypes;the nucleotide and amino acid homology of 17 CVA16 B1b isolates were 93.8%—100% and 98.3%—100%,and the nucleotide and amino acid homology with other domestic isolates was 91.1 %—99.2% and 97.3%—99.0%,respectively;the nucleotide and amino acid homology of the three Bla isolates was 98.0%—98.1% and 99.3%,and those with other domestic Bla isolates was 88.7%—98.1% and 98.3%—99.7%,respectively;17 B1b isolates and other three Bla isolates showed the nucleotide and amino acid homology of 87.4%—88.4% and 97.3%—98.7%.Conclusion The CVA16 prevalent in Kunming in 2019 belonged to Bla and B1b genotypes,with B1b as the main strain,and all of them were prevalent strains in the mainland of China.

Objective To investigate the mechanism of anti-IL-17A monoclonal antibody(secukinumab) regulating autophagy and inflammation in gout.Methods The peripheral venous blood samples from 57 patients with acute gout(AG),57patients with intermittent gout(IG) and 82 healthy volunteers were collected and measured for the mRNA transcription levels of autophagy-related genes(ATGs) ATG4B,ATG7, A TG16L1,Beclin-1 and LC3B by RT-qPCR.The model of AG inflammation was established by adding monosodium urate(MSU) crystals into the peripheral venous blood samples of healthy volunteers,and the transcription and protein expression of IL-1β were detected by RT-qPCR and ELISA at 0,1,2,4,6 and8 h and different concentrations(0,100,200 and 400 μmol/L) of secukinumab.The peripheral blood samples of healthy volunteers were divided into control(without MSU treatment),MSU(100 μg/mL),MSU+colchicine(100 μg/mL+30 μg/mL) and MSU+secukinumab(100 μg/mL+400 μmol/L) groups,which were detected for the mRNA transcription and protein expression of IL-1 β and ATGs by RT-qPCR and Western blot,and for the expression of IL-1β,IL-12 and IL-35 by ELISA.Results The mRNA expression levels of ATG4B, Beclin-1 and LC3B in AG,IG and healthy control groups were significantly different(F=3.896,11.78 and 3.856,respectively,each P <0.05),among which the mRNA levels in AG were lower than those in IG and HC groups(t=2.692,3.234,2.231 and 2.085,4.795,2.748,respectively,each P <0.05);the expression levels of ATG16L1 mRNA were significantly different in the three groups(F=7.949,P <0.001),and was significantly lower in AG group than HC group(t=3.860,P <0.001).In AG inflammation model,the mRNA and protein expression of IL-1 β reached their peak in 2—4 h,and the anti-inflammation effect of secukinumab was the strongest at the concentration of 400 μmol/L.Compared with MSU group,the mRNA levels of ATG16L1 and LC3B(t=2.343 and 2.916,respectively,each P <0.05) as well as the expression levels of ATG4B,ATG7,Beclin-1,ATG16L1 and LC3B-Ⅱ proteins(t=28.84,11.6,8.402,4.124 and 2.458,respectively,each P <0.05) in MSU+secukinumab group decreased significantly.The expression levels of IL-12 and IL-35 in the control,MSU,MSU+colchicine and MSU+secukinumab groups showed significant difference(F=7.009 and 6.518,respectively,each P <0.01).Compared with MSU group,the expression level of IL-12 significantly decreased(t=2.604,P <0.05)in MSU+secukinumab group,and the expression level of IL-35 also decreased,while with no significant difference(t=1.928,P> 0.05).Conclusion Secukinumab can regulate the mRNA and protein expression of ATGs,reduce the levels of pro-inflammatory cytokines,and inhibit gout inflammation,which provides a reference for the treatment of gout.

Objective To analyze rash and fever illness(RFI) and other respiratory virus co-infection in some confirmed measles cases in Jilin Province from 2013 to 2022,and to provide scientific basis for measles co-infection and multi-pathogen diagnosis.Methods The throat swab specimens of 106 measles confirmed cases in Jilin Province from 2013 to 2022 were collected,of which nine kinds of RFI associated virus and respiratory virus with similar clinical symptoms were detected by fluorescence quantitative PCR,including varicella-zoster virus(VZV),Dengue virus(DENY),human parvovirus B19(HPV-B19),Epstein-Barr virus(EBV),human herpesvirus6(HHV6),human rhinovirus(HRV),respiratory syncytial virus(RSV),human adenovirus(HAdV) and human cytomegalovirus(HCMV),and statistical analysis was conducted by using SPSS 23.0 software.Results VZV and DENV were not detected in the 106 collected specimens,and the other 7viruses were detected.30.18% of the measles cases were co-infected with other viruses,of which only HCMV co-infection cases showed significant difference in the age groups(≤24 months old,24 months old to 15 years old,> 15 years old)(χ~2=9.941,P <0.05);there was no significant difference between the genders in cases co-infected with other viruses(χ~2=0.200—2.778,each P> 0.05).Conclusion Some confirmed cases of measles might be co-infected with one or more other viruses in Jilin Province from 2013 to 2022,and it is recommended to strengthen targeted surveillance and differential diagnosis,especially for infants and young children,women of childbearing age and pregnant women.

Objective To prepare a national reference standard for the quantification of HEK293 cell DNA content,so as to provide a support for the determination of residual DNA in HEK293 cells in the industry.Methods HEK293 cell DNA prepared using Genomic-tip 500/G and genomic DNA purification reagents was used as source materials,and the purity and content were assessed using ultraviolet spectrophotometry and agarose gel electrophoresis.After dilution to approximately 100 ng/μL,the DNA was aliquoted at 160 μL/tube.Five different laboratories were organized for collaborative calibration by using ultraviolet spectrophotometry, and the stability and applicability were evaluated.Results The HEK293 cell DNA national reference standard exhibited A_(260)/A_(280) ratios between 1.8 and 2.0 and displayed a single band on electrophoresis,meeting the specified criteria.Collaborative calibration across five laboratories yielded 78 valid data points with an average content of 104.8 ng/μL,a relative standard deviation(RSD) of 4.2%.The 95% confidence interval for the mean was 103.8—105.8 ng/μL,and the 95% reference range for single measurements was 96.0—113.6 ng/μL.The average confidence limit rate was 1.0%,and the recommended storage condition was-80 ℃.Applicability studies were conducted using two different models of fluorescence quantitative PCR instruments.The reference standard exhibited good applicability within the range of 0.3—3 000 pg/reaction,with amplification efficiencies of 101% and 95%,and R~2 values of 0.999 2 and 0.999 5 for the standard curves,respectively.Conclusion This batch of HEK293 cell DNA national reference standard meets all required specifications and can be utilized as a national reference standard for fluorescence quantitative PCR detection,with a certified content of 104.8 ng/μL,assigned batch number 270039-202301.

Objective To establish and verify a universal and stable potency test method in vitro for SARS-CoV-2 mRNA vaccine,so as to use it for the quality control of SARS-CoV-2 mRNA vaccine.Methods ELISA kits that could bind well to S protein of SARS-CoV-2 variants,as well as transfected cells,cell plating concentrations and doses for transfection were screened,and then a potency test method for SARS-CoV-2 mRNA vaccine in vitro was established and verified.Results An ELISA kit was found with good binding ability to S protein of each variant,and HEK293T cells were determined as the transfection cells,with the plating concentration of 2.5 × 10~5 cells/mL and the transfection dose of 4 μg/well in the 6-well plate.An universal and stable potency test method for SARS-CoV-2 mRNA vaccine in vitro was established.The verification results showed that the method met the quality control needs.Conclusion The established potency test method in vitro for SARS-CoV-2 mRNA vaccine has good relative accuracy,linearity,intermediate precision and range,and can be applied to the quality control of SARS-CoV-2 mRNA vaccines.

Objective To develop and verify a multiplex fluorescent quantitative PCR method for detection of common bacterial and fungal contaminants in cell culture medium.Methods According to NUC gene of Staphylococcus aureus,COLA gene of Clostridium spore,ITS-2 segment sequence of Candida albicans,a set of primers and probes were designed for each respectively,and using UBI3 gene of capsicum introduced as external standard gene,a triple reaction system of Staphylococcus aureus,Clostridium spore and external standard gene and a double reaction system of Candida albicans and external standard gene were established.The primer specificity,linear range,limit of detection,specificity,anti-interference performance and precision of the method were verified.Finally,100 samples of 293T cell culture medium were detected by using the developed method,which was compared with the common PCR method.Results Three pairs of primers all amplified about 100 bp specific gene bands corresponding to the three strains at different annealing temperatures(56,57,58 and59 ℃),and the size was consistent with the expected.In the range of 5.80 × 10~6 — 5.80 × 10~2 copies/μL,the standard plasmids of the three strains showed a good linear relationship with the Ct values.The standard curve equations were:Y=-3.373 X+37.48,Y=-3.557X+36.59 and Y=-3.536 X+39.78,each R~2> 0.99,respectively,and the amplification efficiency was in the range of 90%—110%.All the limits of detection of the three strains were 10~1 CFU/mL.The primers and probes of the three strains showed no specific amplification on the genomic DNA of six kinds of cells that were prone to cross-reaction.The genomic DNA of 293T cells,Yeast,Escherichia coli and Mycoplasma sp.had no effect on the detection.The CVs of repeatability and intermediate precision verification were both less than 15%.Among 100 cell culture medium samples,14 positive and 86 negative samples were detected,and the results of common PCR method for three positive and two negative samples randomly selected were consistent with the developed method.Conclusion The multiplex fluorescent quantitative PCR method developed in this study for the detection of bacteria and fungi in cell culture medium has good specificity,anti-interference performance and precision,and is simple to operate with low cost and high sensitivity,which can quickly detect the contaminants during cell culture.