Epitopic mapping of linear and conformation-dependent antigenic determinants on GP5 of five U.S. bluetongue viruses

Isolation and characterization of Wad Medani virus obtained in the tuva Republic of Russia

Wad Medani virus (WMV) belongs to the genus Orbivirus and is a poorly studied arbovirus with unclear medical significance. Presently, a limited number of WMV strains are characterized and available in NCBI GenBank, some isolated many years ago. A new WMV strain was isolated in 2012 from Dermacentor nuttalli ticks collected from sheep in the Tuva Republic, Russia, and sequenced using high-throughput methods. Complete coding sequences were obtained revealing signs of multiple intersegment reassortments. These point to a high variability potential in WMV that may lead to the formation of strains with novel properties. These new data on WMV can promote better understanding of: ecological features of its circulation; relationships within the genus Orbivirus; and the medical significance of the virus.

Atomic model of a nonenveloped virus reveals pH sensors for a coordinated process of cell entry

Viruses sense environmental cues (such as pH) to engage in membrane interactions for cell entry during infection but how non-enveloped viruses sense pH is largely undefined. Here, we report the structures — at high and low pH conditions — of bluetongue virus (BTV), which enters cells via a two-stage endosomal process. The receptor-binding protein VP2 possesses a zinc-finger and a conserved His866, which may function to maintain VP2 in a metastable state and to sense early-endosomal pH, respectively. The membrane penetration protein VP5 has three domains: dagger, unfurling, and anchoring. Notably, the β-meander motif of the anchoring domain contains a histidine cluster that could sense the late-endosomal pH and four putative membrane-interaction elements. Exposing BTV to low pH detaches VP2 and dramatically refolds the dagger and unfurling domains of VP5. Our biochemical and structure-guided mutagenesis studies support these coordinated pH-sensing mechanisms.

Separation and isolation of BTV dsRNA segments and viral proteins

Bluetongue virus (BTV) genome contains ten double-stranded RNA segments. The sequence of the plus strand of each of the BTV genomic double-stranded RNAs is the same as that of its mRNA, which encodes for a single viral protein, except the smallest S4 segment which can encode for two nonstructural proteins, primarily for the release assistance of the viral progeny. The separation and isolation of each BTV dsRNA segment and viral protein have provided extensive data related to its viral infection, pathology, suppression of host cellular functions, and eventual apoptosis of the infected host cells. This cytoplasmic virus is also an animal killer that costs the U.S. livestock industry at least $125 million yearly. However, this virus has no known effect on humans. Thus, it is very safe to carry out investigation with the virus, preferably in a BSL-2 laboratory.

Oncolytic bluetongue viruses: promise, progress, and perspectives

Humans are sero-negative toward bluetongue viruses (BTVs) since BTVs do not infect normal human cells. Infection and selective degradation of several human cancer cell lines but not normal ones by five US BTV serotypes have been investigated. We determined the susceptibilities of many normal and human cancer cells to BTV infections and made comparative kinetic analyses of their cytopathic effects, survival rates, ultra-structural changes, cellular apoptosis and necrosis, cell cycle arrest, cytokine profiles, viral genome, mRNAs, and progeny titers. The wild-type US BTVs, without any genetic modifications, could preferentially infect and degrade several types of human cancer cells but not normal cells. Their selective and preferential BTV-degradation of human cancer cells is viral dose–dependent, leading to effective viral replication, and induced apoptosis. Xenograft tumors in mice were substantially reduced by a single intratumoral BTV injection in initial in vivo experiments. Thus, wild-type BTVs, without genetic modifications, have oncolytic potentials. They represent an attractive, next generation of oncolytic viral approach for potential human cancer therapy combined with current anti-cancer agents and irradiation.

Peptide dendrimers: applications and synthesis

Peptide dendrimers are radial or wedge-like branched macromolecules consisting of a peptidyl branching core and/or covalently attached surface functional units. The multimeric nature of these constructs, the unambiguous composition and ease of production make this type of dendrimer well suited to various biotechnological and biochemical applications. Applications include use as biomedical diagnostic reagents, protein mimetics, anticancer and antiviral agents, vaccines and drug and gene delivery vehicles. This review focuses on the different types of peptide dendrimers currently in use and the synthetic methods commonly employed to generate peptide dendrimers ranging from stepwise solid-phase synthesis to chemoselective and orthogonal ligation.

Changes in the outer capsid proteins of bluetongue virus serotype ten that abrogate neutralization by monoclonal antibodies

Six neutralizing monoclonal antibodies (Mabs) and nine neutralization resistant viral variants (escape-mutant viruses (EMVs)) were used to further characterize the neutralization determinants of bluetongue virus serotype 10 (BTV10). The EMVs were produced by sequential passage of a highly cell culture adapted United States prototype strain of BTV10 in the presence of individual neutralizing Mabs. Mabs were characterized by neutralization and immune precipitation assays, and phenotypic properties of EMVs were characterized by neutralization assay. Sequencing of the gene segments encoding outer capsid proteins VP2 and VP5 identified mutations responsible for the altered phenotypic properties exhibited by individual EMVs. Amino acid substitutions in VP2 were responsible for neutralization resistance in most EMVs, whereas an amino acid substitution in VP5, without any change in VP2, was responsible for the neutralization resistance of one EMV. The data confirm that VP2 contains the major neutralization determinants of BTV, and that VP5 also can influence neutralization of the virus. The considerable plasticity of the neutralization determinants of BTV has significant implications for future development of non-replicating vaccines.

Antigenic profile of African horse sickness virus serotype 4 VP5 and identification of a neutralizing epitope shared with bluetongue virus and epizootic hemorrhagic disease virus

African horse sickness virus (AHSV) causes a fatal disease in horses. The virus capsid is composed of a double protein layer, the outermost of which is formed by two proteins: VP2 and VP5. VP2 is known to determine the serotype of the virus and to contain the neutralizing epitopes. The biological function of VP5, the other component of the capsid, is unknown. In this report, AHSV VP5, expressed in insect cells alone or together with VP2, was able to induce AHSV-specific neutralizing antibodies. Moreover, two VP5-specific monoclonal antibodies (MAbs) that were able to neutralize the virus in a plaque reduction assay were generated. To dissect the antigenic structure of AHSV VP5, the protein was cloned in Escherichia coli using the pET3 system. The immunoreactivity of both MAbs, and horse and rabbit polyclonal antisera, with 17 overlapping fragments from VP5 was analyzed. The most immunodominant region was found in the N-terminal 330 residues of VP5, defining two antigenic regions, I (residues 151-200) and II (residues 83-120). The epitopes were further defined by PEPSCAN analysis with 12mer peptides, which determined eight antigenic sites in the N-terminal half of the molecule. Neutralizing epitopes were defined at positions 85-92 (PDPLSPGE) for MAb 10AE12 and at 179-185 (EEDLRTR) for MAb 10AC6. Epitope 10AE12 is highly conserved between the different orbiviruses. MAb 10AE12 was able to recognize bluetongue virus VP5 and epizootic hemorrhagic disease virus VP5 by several techniques. These data will be especially useful for vaccine development and diagnostic purposes.

Recent advances in multiple antigen peptides

The goals for the development of multiple antigen peptides (MAP) are to provide a rational and unambiguous system to multimerize different types of synthetic peptide antigens and to attach immunomodulating molecules for targeting and delivery. These goals have been largely realized and new designs of MAPs now permit a broad range of immune responses including CTLs and mucosal IgAs. Furthermore, significant advances by the inventiveness of many laboratories have led to applications of MAPs for serodiagnostic and other biochemical uses including those for drug discovery. An important aspect to accomplish various goals of MAPs is chemistry. New methodologies using unprotected peptides as building blocks have been developed to accommodate new and sophisticated design of MAPs. This review is written based on the personal perspective of my laboratory and will focus on the recent progress in MAPs, together with the chemistry to achieve their synthesis.

Mapping and characterization of antigenic epitopes and the nucleic acid-binding domains of the VP6 protein of bluetongue viruses

Heterologously expressed VP6 and truncated VP6 proteins of bluetongue virus (BTV) serotype 11 purified to near homogeneity were used for structure and function analyses. The yield of the expressed VP6 was host cell dependent. Six antigenic epitopes of VP6 of BTV were identified and mapped by immunoblot analyses and enzyme-linked immunosorbent assay with oligoclonal antibodies. These determinants were surface accessible and conserved among the cognate VP6 proteins of five U.S. BTV serotypes. The amino acid sequences and sizes of these six antigenic epitopes were determined, and their precise locations were also mapped and confirmed by deletion analyses. The nucleic acid binding activities of VP6, confirmed by electrophoretic mobility shift assay, were concentration dependent. The binding activities and affinities of the purified expressed VP6 protein towards double-stranded RNA and double-stranded DNA were similar. Two domains of VP6, corresponding to three of the six antigenic epitopes, were responsible for the nucleic acid binding activities and have been mapped within 28 amino acids near the middle and 11 residues near the carboxyl terminus of VP6 by electrophoretic mobility shift assay and deletion mutant analyses. Synthetic oligopeptides corresponding to these three regions also exhibited similar concentration-dependent nucleic acid binding activities.