Identification of oligopeptides mimicking the receptor-binding domain of Hantaan virus envelope glycoprotein from a phage-displayed peptide library.

Attachment of enveloped viruses to cells is triggered by the receptor-binding domain (RBD) on envelope glycoproteins (GP) binding to receptors located on the cell surface. To date, recognized receptors and RBD of hantaan virus (HTNV) have not been exactly defined. In this study, one monoclonal antibody (MAb) 3G1 possessing high neutralizing activity, which is directed against HTNV envelope glycoprotein G2, was used to determine the crucial motif of RBD. Peptide ligands binding to MAb 3G1 were selected from a 12 amino acid peptide library displayed on filamentous phages. After 3 rounds of selection, the binding capacity between phages and MAb 3G1 was examined byELISA. Afterwards the positive phage clones with high binding activity to MAb 3G1 were chosen and sequenced. The peptide sequences of positive phage clones were compared with that of HTNV 76-118 strain G2. A motif Y/F/WPW(X)HX1-2HY, aligned to the primary sequences of G2 96YPWHTAKCHY105, was identified from the peptide inserts in the 9 positive clones. Positive phages and synthesized peptide containing the motif were bound significantly to virus-susceptible cell (Vero-E6) membranes by ELISA and immunofluorescence assay, respectively. Therefore, the sequence on G2 between amino acid 96 and 105 may be a key motif of HTNV RBD recognized by viral receptors on target cell membranes. Further characterization of the motif would provide useful information in understanding of the cellular entry of HTNV.

Sites that direct nuclear compartmentalization are near the 5' end of the mouse immunoglobulin heavy-chain locus.

VDJ rearrangement in the mouse immunoglobulin heavy chain (Igh) locus involves a combination of events, including a large change in its nuclear compartmentalization. Prior to rearrangement, Igh moves from its default peripheral location near the nuclear envelope to an interior compartment, and after rearrangement it returns to the periphery. To identify any sites in Igh responsible for its association with the periphery, we systematically analyzed the nuclear positions of the Igh locus in mouse non-B- and B-cell lines and, importantly, in primary splenic lipopolysaccharide-stimulated B cells and plasmablasts. We found that a broad approximately 1-Mb region in the 5' half of the variable-gene region heavy-chain (Vh) locus regularly colocalizes with the nuclear lamina. The 3' half of the Vh gene region is less frequently colocalized with the periphery, while sequences flanking the Vh gene region are infrequently so. Importantly, in plasmacytomas, VDJ rearrangements that delete most of the Vh locus, including part of the 5' half of the Vh gene region, result in loss of peripheral compartmentalization, while deletion of only the proximal half of the Vh gene region does not. In addition, when Igh-Myc translocations move the Vh genes to a new chromosome, the distal Vh gene region is still associated with the nuclear periphery. Thus, the Igh region that interacts with the nuclear periphery is localized but is likely comprised of multiple sites that are distributed over approximately 1 Mb in the 5' half of the Vh gene region. This 5' Vh gene region that produces peripheral compartmentalization is the same region that is distinguished by requirements for interleukin-7, Pax5, and Ezh2 for rearrangement of the Vh genes.

Progressive activation of DNA replication initiation in large domains of the immunoglobulin heavy chain locus during B cell development.

In mammalian cells, the replication of tissue-specific gene loci is believed to be under developmental control. Here, we provide direct evidence of the existence of developmentally regulated origins of replication in both cell lines and primary cells. By using single-molecule analysis of replicated DNA (SMARD), we identified various groups of coregulated origins that are activated within the Igh locus. These origin clusters can span hundreds of kilobases and are activated sequentially during B cell development, concomitantly with developmentally regulated changes in chromatin structure and transcriptional activity. Finally, we show that the changes in DNA replication initiation that take place during B cell development, within the D-J-C-3'RR region, occur on both alleles (expressed and nonexpressed).

[Identification of oligopeptides mimicking the virus attachment protein of hantaan virus].

OBJECTIVE: To identify and characterize the epitope associated with the virus attachment protein (VAP) of hantaan virus. METHODS: The monoclonal antibody 3G1 was used as the ligand to biospan from a phage-displayed 12-amino acid peptide library, then the positive phage clones were chosen and sequenced. The amino acid sequences of them were compared with that of hantaan virus G2 in homology. The characteristics of positive phage were studied by IFA and ELISA. A decapeptide combining to cell membrane was observed under laser scanning confocal microscope (LSCM). RESULTS: The conservative motif PX(1-2) HX(0-2) H displaying on positive clones shared homologous amino acid sequence with G2 96YPWHTAKCHY105. CONCLUSION: G2 96YPWHTAKCHY105 might play some roles in virus binding to host cell, and might be a possible key epitope of hantaan virus VAP.

Changes in replication, nuclear location, and expression of the Igh locus after fusion of a pre-B cell line with a T cell line.

We have previously observed that replication and nuclear location of the murine Igh locus are developmentally regulated during B cell differentiation. In non-B, B, and plasma cells, sequences near the 3' end of the Igh locus replicate early in S while upstream Vh sequences replicate late in S, and the Igh locus is located near the nuclear periphery. In fact, in MEL non-B cells, replication of a 500-kb segment containing Igh-C and flanking sequences occurs progressively later throughout S by 3' to 5' unidirectional fork movement. In contrast, in pro- and pre-B cells, the entire 3-Mb Igh locus is located away from the nuclear periphery and replicates early in S by forks progressing in both directions. In this study, using an 18-81 (pre-B) x BW5147 (T) cell fusion system in which Igh expression is extinguished, we found that in all Igh alleles, Vh sequences replicated later in S than 3' Igh sequences (similar to that detected in BW5147), but the Igh locus was situated away from the nuclear periphery (similar to that observed in 18-81). Thus, pre-B cell-derived Igh genes had changes in replication timing, but not in nuclear location, whereas T cell-derived Igh genes changed their nuclear location but not their replication timing. These data are consistent with the silencing of a pre-B cell-specific replication program in the fusion hybrid cells and independent regulation of the nuclear location of Igh loci.

[Purification and characterization of the fusion protein TGF-betaR II/Fc].

AIM: To express the fusion protein TGF-betaR II/Fc in large amounts by using recombinant Bac-TR II baculovirus expression system constructed by our laboratory and to purify and characterize it. Then, to verify whether the fusion protein TGF-betaR II/Fc can be able to block the biological activity of cytokine TGF-beta1. METHODS: The viral titer was determined by plaque forming test. The recombinant baculovirus was amplified by infecting sf9 cells. The fusion protein was purified by FPLC using protein G column. The purified product was analyzed by SDS-PAGE and the amount of target protein calculated by gray scanning. Western blot and sandwich ELISA were used to affirm the expression of the fusion protein. MTT colorimetry was used to test whether the fusion protein can block the inhibition effect of cytokine TGF-beta1 on the growth of L929 cells. It was to verify whether the fusion protein can reduce the fibronectin production in L929 cells accelerated by TGF-beta1 by western blot. RESULTS: The titer of recombinant Bac-TR II baculavirus in the primary culture fluid was 2x10(12) pfu/L. After electrophoresis, gray scanning analysis showed that the target protein accounted for 10 percent of the total protein. Western blot analysis and sandwich ELISA detection proved that the target protein has been expressed. The fusion protein could block the inhibitive effect of cytokine TGF-beta1 on the growth of L929 cells and fibronectin production in L929 cells. CONCLUSION: The fusion protein TGF-betaR II/Fc can inhibit the biological activity of TGF-beta1 in-vitro. This study will be helpful to the mass production of the fusion protein, and will facilitate its further use in the therapy of pulmonary fibrosis.

[Analysis on patial amino acid sequence of a novel glycoprotein binding to antiherpes simplex virus monoclonal antibody CHA9].

AIM: To acquire the characteristic amino acid sequence of a novel glycoprotein of herpes simplex virus (HSV), so as to localize gene encoding the novel glycoprotein accurately. METHODS: A 12-mer phage peptide library was screened for 3 rounds by using biotinylated mAb CHA9 against new glycoprotein g30k of HSV-2. Positive phage clones were detected by ELISA. 10 positive clones were selected randomly for sequencing. Sequence alignment and hydrophobic cluster analysis were carried out. RESULTS: Most of the sequences of 10 positive phage clones were highly homologous with a core-PH/KHXHXGS-. Phages containing this motif could react specifically with the mAb CHA9 and not cross-react with other IgG. Hydrophobic cluster analysis showed that the peptide was likely to form an epitope. CONCLUSION: We obtained a characteristic short peptide which shows some characters of g30K amino acid sequence. It provides valuable clue for prediction of the open reading frame of g30K gene and will be useful to explore biological characteristics of the new glycoprotein.

[Development and application of an indirect immunofluorescence assay for the detection of serum immunoglobulin G to human herpesvirus 6].

AIM: To establish an indirect immunofluorescence assay(IFA) for detection of serum IgG antibody against human herpesvirus 6(HHV-6). METHODS: Cord blood mononuclear cells infected by HHV-6 strain CN(5) were used to prepare cell antigen smear, so as to establish an IFA and make an epidemical investigation on serum specimens of child-bearing age, women. RESULTS: The specificity of the IFA for HHV-6 was confirmed by absorption assay(test). The IFA detection showed that in serum specimens from 116 cases of child-bearing age, women, the positive rate of anti-HHV-6 IgG was 72.4% and geometric mean titer(GMT) was 1:61. The positive rate and GMT of serum anti-HHV-6 IgG had no differences between pregnant women and unpregnant women, neither among pregnant women at different pregnant stages. CONCLUSION: A specific IFA has been developed successfully for epidemical investigation of HHV-6 infection rate in child-bearing women.