M2 protein of influenza A virus is encoded by a spliced mRNA derived from RNA segment 7 and plays an important role in influenza virus replication. It is also a target molecule of anti-virus drugs. We extracted the viral genome RNAs from MDCK cells infected with swine influenza A virus (SIV) H3N2 subtype and amplified the SIV M2 gene by reverse transcriptase-polymerase chain reaction using the isloated viral genome RNAs as template. The amplified cDNA was cloned into a prokaryotic expression vector pET-28a(+) (designated pET-28a(+)-M2) and a eukaryotic expression vector p3xFLAG-CMV-7.1 (designated p3xFLAG-CMV-7.1-M2), respectively. The resulted constructs were confirmed by restriction enzyme digestion and DNA sequencing analysis. We then transformed the plasmid pET-28a(+)-M2 into Escherichia coli BL21 (DE3) strain and expressed it by adding 1 mmol/L of IPTG (isopropyl-beta-D-thiogalactopyranoside). The recombinant M2 protein was purified from the induced bacterial cells using Ni(2+) affinity chromatography. Wistar rats were immunized with the purified M2 protein for producing polyclonal antibodies specific for it. Western blotting analysis and immunofluorescence analysis showed that the produced antibodies were capable of reacting with M2 protein expressed in p3xFLAG-CMV-7.1-M2-transfected cells as well as that synthesized in SIV-infected cells. We also transfected plasmid p3xFLAG-CMV-7.1-M2 into Vero cells and analyzed its subcellular localization by immunofluorescence. The M2 protein expressed in the Vero cells was 20 kDa in size and dominantly localized in the cytoplasm, showing a similar distribution to that in SIV-infected cells. Western blotting analysis of SIV-infected cells suggested that M2 was a late phase protein, which was detectable 12 h post-infection, later than NS1, NP and M1 proteins. It would be a potential molecular indicator of late phases replication of virus. Our results would be useful for studying the biological function of M2 protein in SIV replication.
Animals ; Antibodies, Monoclonal ; biosynthesis ; Cercopithecus aethiops ; Cloning, Molecular ; Escherichia coli ; genetics ; metabolism ; Influenza A Virus, H3N2 Subtype ; genetics ; RNA ; biosynthesis ; genetics ; Rats ; Rats, Wistar ; Recombinant Proteins ; biosynthesis ; genetics ; immunology ; Swine ; Transfection ; Vero Cells ; Viral Matrix Proteins ; biosynthesis ; genetics ; Virus Replication ; genetics

Influenza A virus matrix protein (M1) is encoded by a spliced mRNA derived from RNA segment 7 and plays an important role in the virus life cycle. In the present study, we extracted the viral genome RNAs from allantoic fluid of 9-day-old embryonated chicken eggs infected with swine influenza A virus (SIV) H3N2 subtype and amplified the SIV M1 gene by reverse transcriptase-polymerase chain reaction using the isloated viral genome RNAs as template. The amplified cDNA was cloned into an expression vector pET-28a (+) (designated pET-28a-M1) and confirmed by DNA sequencing analysis. We then transformed the plasmid pET-28a-M1 into Escherichia coli BL21 strain for heterologous expression. The expression of M1 was induced by 1mM isopropyl-beta-D-thiogalactopyranoside. SDS-PAGE analysis of the induced bacterial cells revealed that the recombinant M1 protein was expressed in high yield level. Next, we purified the expressed recombinant M1 using Ni2+ affinity chromatography and immunized Wistar rat with the purified M1 protein for producing polyclonal antibodies specific for M1. Western blotting analysis showed that the produced antibodies were capable of reacting with M1 protein expressed in Escherichia coli as well as that synthesized in SIV-infected cells. We further cloned the amplified M1 cDNA into a eukaryotic expression plasmid p3xFLAG-CMV-7.1 to construct the recombinant plasmid p3xFLAG-CMV-M1 for expressing M1 in eukaryotic cells. Western blotting analysis revealed that the M1 protein was expressed in p3xFLAG-CMV-M1-transfected Vero cells and recognized by the produced anti-M1 antibodies. Using the produced anti-M1 antibodies, we analyzed the kinetics of M1 protein in the virus-infected cells during influenza virus infection and estimated the possibility of M1 as an indicator of influenza virus replication. The recombinant M1 protein, anti-M1 antibodies and recombinant expression plasmids would provide useful tools for studies of biological function of M1 protein and the basis of SIV replication.
Animals ; Antibodies, Monoclonal ; biosynthesis ; Chick Embryo ; Cloning, Molecular ; Escherichia coli ; genetics ; metabolism ; Influenza A Virus, H3N2 Subtype ; genetics ; physiology ; Rats ; Rats, Wistar ; Recombinant Proteins ; genetics ; immunology ; metabolism ; Swine ; Viral Matrix Proteins ; genetics ; immunology ; metabolism ; Virus Replication ; genetics

Objective:To investigate urinary microalbumin to creatinine ratio (ACR) and α1-microglobulin to creatinine ratio (MCR) of people aged 40 years old and above in Shanxi province, and analyze the influencing factors of abnormal ACR and MCR, and to provide evidence for the prevention and control of chronic kidney diseases.Methods:It was a cross-sectional study. The data came from a screening study of chronic kidney diseases conducted by Shanxi Provincial People's Hospital from April to November 2019, involving aged 40 years old and above from 10 counties (Ningwu county, Yu county, Yangqu county, Lin county, Shouyang county, Zezhou county, Huozhou city, Hejin city, Linyi county and Ruicheng county) in Shanxi province. The related data were collected through questionnaire surveys, physical examinations, and blood and urine sample collection. Urinary α1-microglobulin, creatinine, and microalbuminuria were measured. Urinary ACR and MCR were calculated using urinary creatinine correction. ACR abnormality was defined as ≥30 mg/g, and MCR abnormality was defined as >23 mg/g. Covariate analysis was used to control confounding factors, and adjusted urinary ACR and MCR of 10 counties were calculated. Spearman correlation analysis and chi-square test were performed to analyze the factors associated with abnormal urinary ACR and MCR. Logistic regression analysis model was used to identify the influencing factors of abnormal urinary ACR and MCR.Results:A total of 12 285 residents were enrolled in the study, including 5 206 males (42.4%) and 7 079 females (57.6%). The median age was 58.0 (51.0, 66.0) years old. The median urinary ACR was 7.5 (4.5, 15.7) mg/g, and the median urinary MCR was 10.2 (6.4, 16.2) mg/g. A total of 1 572 individuals (12.80%) had urinary ACR abnormality and 1 450 individuals (11.80%) had urinary MCR abnormality. Yangqu county, Yuxian county, and Ningwu county had higher urinary ACR with (35.58±3.04) mg/g, (34.08±4.50) mg/g and (32.09±3.19) mg/g, respectively. The urinary MCR was generally similar among the 10 counties and Yangqu county had higher urinary MCR with (13.86±0.41) mg/g. In addition to Yu county, female individuals had higher urinary ACR compared to males in other counties, whereas female individuals had lower urinary MCR compared to males in 10 counties. Multivariate logistic regression analysis results showed that elevated triglyceride, fasting blood glucose, glycated hemoglobin, systolic blood pressure, diastolic blood pressure, age, body mass index and gender were independent influencing factors of abnormal urinary ACR and MCR (all P<0.05). Elevated blood homocysteine and low educational level were independent influencing factors of urinary MCR abnormality (both P<0.05). Conclusions:There are differences of gender and region in urinary ACR and MCR among individuals aged 40 years old and above in the 10 counties of Shanxi province. Triglyceride, fasting blood glucose, glycated hemoglobin, systolic blood pressure, diastolic blood pressure, age, gender, and body mass index are independent related factors of abnormal urinary ACR and MCR. Blood homocysteine and education level are independent related factors of abnormal urinary MCR.