A potential peptide pathway from viruses to oral lichen planus.

Oral lichen planus is an idiopathic inflammatory disease of oral mucous membranes, characterized by an autoimmune epidermis attack by T cells. It remains unknown, however, how such aggressive T cells are activated in vivo to cause epidermal damage. This study analyzes the relationship at the peptide level between viruses and oral lichen planus disease. Four potentially immunogenic peptides (SSSSSSS, QEQLEKA, LLLLLLA, and MLSGNAG) are found to be shared between HCV, EBV, HHV-7, HSV-1, and CMV and three human proteins (namely pinin, desmoglein-3, and plectin). The described peptide sharing might be of help in deciphering the still unexplained immunopathogenic pathway that leads to oral lichen planus.

Human herpesvirus 7 U21 tetramerizes to associate with class I major histocompatibility complex molecules.

UNLABELLED: The U21 gene product from human herpesvirus 7 binds to and redirects class I major histocompatibility complex (MHC) molecules to a lysosomal compartment. The molecular mechanism by which U21 reroutes class I MHC molecules to lysosomes is not known. Here, we have reconstituted the interaction between purified soluble U21 and class I MHC molecules, suggesting that U21 does not require additional cellular proteins to interact with class I MHC molecules. Our results demonstrate that U21, itself predicted to contain an MHC class I-like protein fold, interacts tightly with class I MHC molecules as a tetramer, in a 4:2 stoichiometry. These observations have helped to elucidate a refined model describing the mechanism by which U21 escorts class I MHC molecules to the lysosomal compartment. IMPORTANCE: In this report, we show that the human herpesvirus 7 (HHV-7) immunoevasin U21, itself a class I MHC-like protein, binds with high affinity to class I MHC molecules as a tetramer and escorts them to lysosomes, where they are degraded. While many class I MHC-like molecules have been described in detail, this unusual viral class I-like protein functions as a tetramer, associating with class I MHC molecules in a 4:2 ratio, illuminating a functional significance of homooligomerization of a class I MHC-like protein.

Characterization of the lymphotropic amplicons-6 and tamplicon-7 vectors derived from HHV-6 and HHV-7.

Amplicon-6 and Tamplicon-7 are novel non-integrating vectors derived from the lymphotropic Human Herpesviruses 6 and 7 (HHV-6 and HHV-7). In the presence of helper viruses the amplicon vectors replicate to yield packaged defective genomes of size approximately 150 kb and consisting of multiple repeat units containing (i) the oriLyt DNA replication origin (ii) the pac-1 and pac-2 cleavage and packaging signals (iii) bacterial plasmid DNA sequences (iv) the chosen transgene(s). Employing CD46 as a receptor HHV-6 gains entry into varied cells, including lymphocytes and dendritic cells, whereas HHV-7 employs the CD4 receptor to target CD4+ cells. The amplicon-based vectors have facilitated the characterization of viral DNA replication and packaging. Following electroporation and helper virus superinfection, the vectors can be transmitted as cell associated and as cell-free virions secreted into the medium. Analyses by flow cytometry have shown good cell spread and efficient gene expression. Exemplary transgenes have included: (i) The Green Fluorescence Protein (GFP) (ii) Genes for potential use in anti-viral vaccination e.g., the HSV-1 glycoprotein D (gD) with and without the trans-membrane region, expressed intracellularly, at the cell membrane or as secreted proteins. (iii) Tumor cell antigens. (iv) Apoptotic genes for development of oncolytic vectors. Due to their cell tropism, their structure as concatemeric genomes, with less than 1.5 kb of viral DNA sequences, the HHV-6 and 7 amplicons have the potential to become unique vectors for immunization and lymphotropic gene therapy.

Human herpesvirus 7 U47 gene products are glycoproteins expressed in virions and associate with glycoprotein H.

The function of the human herpesvirus 7 (HHV-7) U47 gene, which is a positional homologue of the genes encoding glycoprotein O (gO) in human cytomegalovirus (HCMV) and human herpesvirus 6 (HHV-6), was analysed. A monoclonal antibody (mAb) against the U47 gene product reacted in immunoblots with proteins migrating at 49 and 51 kDa in lysates of HHV-7-infected cells and with 49 and 51 kDa proteins in partially purified virions. Digestion of the 49 and 51 kDa proteins with endoglycosidase H and peptide N-glycosidase F indicated that the U47-encoded proteins were modified with N-linked oligosaccharides. Therefore, the U47 gene and its product were named gO, as in HCMV and HHV-6. In addition, the anti-gO mAb co-immunoprecipitated glycoprotein H (gH) in HHV-7-infected cells, indicating an association between HHV-7 gO and gH. The results suggest that the HHV-7 gO-gH complex might have a similar function to that in HCMV or HHV-6, such as cell-cell fusion in virus infection.

Characterization of human herpesvirus 7 U27 gene product and identification of its nuclear localization signal.

A monoclonal antibody, 5H4, that recognizes human herpesvirus 7 (HHV-7) was used in Western analysis to probe HHV-7-infected SupT1 cells. This antibody recognizes a 40-kDa virus-specific polypeptide that is expressed in the absence of viral DNA synthesis. By screening a lambdagt11 HHV-7 cDNA library, the gene encoding the protein was identified as the U27 open reading frame previously reported [J. Virol. (1996) 70, 5975-5989]. Immunofluorescent studies showed a punctate nuclear localization of the protein in both HHV-7-infected cells and transfected cells. A computer program predicted two classic nuclear localization signals (NLSs) in the middle and C-terminal regions of the protein. A C-terminal deletion mutant of the protein could not enter the nucleus, whereas green fluorescent protein or maltose binding protein fused to the C-terminal region of the protein was transported into the nucleus. These findings demonstrate that the predicted C-terminal, but not middle, NLS of the protein actually function as NLS. In addition, nuclear transport of a maltose binding protein-fusion protein containing the C-terminal NLS of the U27 protein was inhibited by both wheat germ agglutinin and a Q69L Ran-GTP mutant, indicating that the U27 protein is transported into the nucleus from the cytoplasm by means of classic nuclear transport machinery. Interestingly, this NLS motif is highly conserved at the C-termini of all herpesvirus DNA polymerase processivity factors that have been examined.

Identification and analyses of glycoprotein B of human herpesvirus 7.

The gene for the human herpes virus 7 (HHV-7) glycoprotein B (gB) has been identified by sequencing a molecularly cloned HHV-7 DNA fragment. A 2.5-kb open reading frame (ORF) encoded a protein of 822 amino acids with characteristics of a transmembrane glycoprotein, and showed the strongest similarity (56.5%) with the human herpesvirus 6 (HHV-6) gB. The genes for the transport/capsid assembly protein (tp/cap) and the DNA polymerase (pol) existed upstream and downstream of the gB gene, respectively. This arrangement was the same as that of HHV-6. Antisera were generated by immunizing mice with a glutathione S-transferase-carboxy terminal gB fusion protein. Immunofluorescent tests demonstrated that the antisera reacted specifically with HHV-7 antigens in cytoplasm of infected cells. The antisera immunoprecipitated proteins with apparent molecular masses of 51, 63 and 112 kDa from HHV-7 infected cells by pulse-chase analysis. In the presence of tunicamycin, the protein with a molecular mass of 112 kDa was replaced by a protein with a molecular mass of 88 kDa, and this size was consistent with the predicted size of the primary translation product of the HHV-7 gB gene. These results suggested that the protein with a molecular mass of 112 kDa was a glycoprotein synthesized by addition of N-linked oligosaccharides to a non-glycosylated precursor of the protein with a molecular mass of 88 kDa and then cleaved into the proteins with molecular masses of 51 and 63 kDa in HHV-7 infected cells.