ABSTRACT
Ebola virus (EBOV) causes highly lethal hemorrhagic fever in humans and nonhuman primates and has a significant impact on public health. The nucleoprotein (NP) of EBOV (EBOV-NP) plays a central role in virus replication and has been used as a target molecule for disease diagnosis. In this study, we generated a monoclonal antibody (MAb) against EBOV-NP and mapped the epitope motif required for recognition by the MAb. The MAb generated via immunization of mice with prokaryotically expressed recombinant NP of the Zaire Ebola virus (ZEBOV-NP) was specific to ZEBOV-NP and able to recognize ZEBOV-NP expressed in prokaryotic and eukaryotic cells. The MAb cross-reacted with the NP of the Reston Ebola virus (REBOV), the Cote-d'Ivoire Ebola virus (CIEBOV) and the Bundibugyo Ebola virus (BEBOV) but not with the NP of the Sudan Ebola virus (SEBOV) or the Marburg virus (MARV). The minimal epitope sequence required for recognition by the MAb was the motif PPLESD, which is located between amino acid residues 583 and 588 at the C-terminus of ZEBOV-NP and well conserved among all 16 strains of ZEBOV, CIEBOV and BEBOV deposited in GenBank. The epitope motif is conserved in four out of five strains of REBOV.
Subject(s)
Animals , Mice , Antibodies, Monoclonal , Allergy and Immunology , Ebolavirus , Chemistry , Allergy and Immunology , Epitope Mapping , Methods , Escherichia coli , Genetics , Metabolism , Mice, Inbred BALB C , Nucleoproteins , Allergy and Immunology , Recombinant Proteins , Genetics , Allergy and ImmunologyABSTRACT
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.