Construction and characterization of 3A-epitope-tagged foot-and-mouth disease virus

Cellular Vimentin Interacts with Foot-and-Mouth Disease Virus Nonstructural Protein 3A and Negatively Modulates Viral Replication

Nonstructural protein 3A of foot-and-mouth disease virus (FMDV) is a partially conserved protein of 153 amino acids that is in most FMDVs examined to date, and it plays important roles in virus replication, virulence, and host range. To better understand the role of 3A during FMDV infection, we used coimmunoprecipitation followed by mass spectrometry to identify host proteins that interact with 3A in FMDV-infected cells. Here, we report that cellular vimentin is a host binding partner for 3A. The 3A-vimentin interaction was further confirmed by coimmunoprecipitation, glutathione S-transferase (GST) pull down, and immunofluorescence assays. Alanine-scanning mutagenesis indicated that amino acid residues 15 to 21 at the N-terminal region of the FMDV 3A are responsible for the interaction between 3A and vimentin. Using reverse genetics, we demonstrate that mutations in 3A that disrupt the interaction between 3A and vimentin are also critical for virus growth. Overexpression of vimentin significantly suppressed the replication of FMDV, whereas knockdown of vimentin significantly enhanced FMDV replication. However, chemical disruption of the vimentin network by acrylamide resulted in a significant decrease in viral yield, suggesting that an intact vimentin network is needed for FMDV replication. These results indicate that vimentin interacts with FMDV 3A and negatively regulates FMDV replication and that the vimentin-3A interaction is essential for FMDV replication. This study provides information that should be helpful for understanding the molecular mechanism of FMDV replication.IMPORTANCE Foot-and-mouth disease virus (FMDV) nonstructural protein 3A plays important roles in virus replication, host range, and virulence. To further understand the role of 3A during FMDV infection, identification of host cell factors that interact with FMDV 3A is needed. Here, we found that vimentin is a direct binding partner of FMDV 3A, and manipulation of vimentin has a negative effect on virus replication. We also demonstrated that amino acid residues 15 to 21 at the N-terminal region of the FMDV 3A are responsible for the interaction between 3A and vimentin and that the 3A-vimentin interaction is critical for viral replication since the full-length cDNA clone harboring mutations in 3A, which were disrupt 3A-vimentin reactivity, could not produce viable virus progeny. This study provides information that not only provides us a better understanding of the mechanism of FMDV replication but also helps in the development of novel antiviral strategies in the future.

Rescue and characterization of a recombinant HY12 bovine enterovirus carrying a foreign HA epitope in the 3A nonstructural protein

Full-length infectious cDNA clones for recombinant HY12 bovine enteroviruses designated as rHY12-3A-2-HA, rHY12-3A-3-HA, and rHY12-3A-9-HA were constructed by the insertion of an epitope from influenza virus hemagglutinin (HA) at the N-terminus of the HY12-encoded 3A protein at amino acid positions 2, 3, and 9. The recombinant HY12 viruses expressing the HA epitope were rescued and characterized using immunoperoxidase monolayer assay, western blotting, and electron microscopy. The three rescued recombinant marker viruses showed similar characteristics, such as TCID₅₀ titer, plaque size, and growth properties, to those of parental rHY12 virus. Comparative analysis of the nucleotide sequences demonstrated the three recombinant marker viruses remained stable for 15 passages with no genetic changes. The recombinant viruses remained viable in various permissive cell lines, including BHK-21, Vero, and PK15 cells, suggesting that the insertion of the HA epitope tag had no effect on virus infectivity. Mice infected with the recombinant marker viruses and the parental virus produced anti-HY12-virus antibodies, while the recombinant marker viruses also produced anti-HA-epitope-tag antibodies. Taken together, these results demonstrate that HY12 viruses containing genetic markers may be useful tools for future investigations of the mechanisms of viral pathogenesis and virus replication, as well as for vaccine development.

Expression of vitamin D receptor in bronchial asthma and its bioinformatics prediction

Vitamin D receptors (VDRs) are associated with the occurrence and development of asthma. The aim of the present study was to analyze the secondary structure and B‑cell and T‑cell epitopes of VDR using online prediction software and aid in the future development of a highly efficient epitope‑based vaccine against asthma. Blood samples were collected from peripheral blood of asthmatic children. Reverse transcription quantitative‑polymerase chain reaction (RT‑qPCR) was performed to detect the expression of VDR in the peripheral blood. Mouse models of asthma were established. Hematoxylin and eosin staining was performed to observe the pathological alterations of the lungs of mice. Immunohistochemistry, western blot analysis and RT‑qPCR were performed to detect the expression of VDR in the lungs of asthmatic mice. Online prediction software immune epitope database and analysis resource, SYFPEITHI and linear epitope prediction based on propensity scale and support vector machines were used to predict the B‑cell and T‑cell epitopes and the RasMol and 3DLigandSite were used to analyze the tertiary structure of VDR. RT‑qPCR demonstrated that VDR expression in the peripheral blood of asthmatic children was decreased. Immunohistochemistry, western blotting and RT‑qPCR demonstrated that VDR expression also decreased in the lungs of mouse models of asthma. VDR B‑cell epitopes were identified at 37‑45, 88‑94, 123‑131, 231‑239, 286‑294 and 342‑350 positions of the amino acid sequence and VDR T‑cell epitopes were identified at 125‑130, 231‑239 and 265‑272 positions. A total of six B‑cell epitopes and three T‑cell epitopes for VDR were predicted by bioinformatics, which when validated, may in the future aid in immunological diagnosis and development of a targeted drug therapy for clinical asthma.

Employing transposon mutagenesis to investigate foot-and-mouth disease virus replication

Probing the molecular interactions within the foot-and-mouth disease virus (FMDV) RNA replication complex has been restricted in part by the lack of suitable reagents. Random insertional mutagenesis has proven an excellent method to reveal domains of proteins essential for virus replication as well as locations that can tolerate small genetic insertions. Such insertion sites can subsequently be adapted by the incorporation of commonly used epitope tags, facilitating their detection with commercially available reagents. In this study, we used random transposon-mediated mutagenesis to produce a library of 15 nt insertions in the FMDV nonstructural polyprotein. Using a replicon-based assay, we isolated multiple replication-competent as well as replication-defective insertions. We adapted the replication-competent insertion sites for the successful incorporation of epitope tags within FMDV non-structural proteins for use in a variety of downstream assays. Additionally, we showed that replication of some of the replication-defective insertion mutants could be rescued by co-transfection of a ‘helper’ replicon, demonstrating a novel use of random mutagenesis to identify intergenomic trans-complementation. Both the epitope tags and replication-defective insertions identified here will be valuable tools for probing interactions within picornavirus replication complexes.