Dissection and integration of the autophagy signaling network initiated by bluetongue virus infection: crucial candidates ERK1/2, Akt and AMPK.

Bluetongue virus (BTV), a complex double-stranded segmented RNA virus, has been found to initiate cellular autophagy for its own benefit. Here, with a view to understanding the underlying mechanisms, we first systematically dissected the exact signaling network in BTV-induced autophagy. We found that the activity of mTOR, a crucial pivot, was inhibited by BTV1 infection, subsequently leading to downstream p70S6K suppression and autophagy initiation. We then explored the upstream regulators of mTOR and analyzed their activities via a series of assays. We found BTV1-induced autophagy to be independent of the ERK1/2 signaling pathway. However, the BTV1-induced inhibition of PI3K/Akt was found to be partially responsible for mTOR inactivation and subsequent autophagy initiation. Furthermore, we found unexpectedly that AMPK seemed to play a more important role in BTV1-induced autophagy. Elevated [Ca(2+)]cyto-mediated activation of CaMKKß exactly managed the activation of AMPK, which then positively regulated autophagy through suppressing mTOR. We must emphasize that TSC2 is a fatal mediator between upstream Akt or AMPK and downstream mTOR through its phosphorylation. Taken together, our data suggested that the BTV1-induced inhibition of the Akt-TSC2-mTOR pathway and the upregulation of the AMPK-TSC2-mTOR pathway both contributed to autophagy initiation and further favored virus replication.

Identification of three novel linear B-cell epitopes on the VP5 protein of BTV16.

Bluetongue virus (BTV) VP5 protein is an important antigenic protein which is centrally involved in serotype determination and the virus entry process. Very little is known about the B-cell epitopes on the BTV VP5 protein recognized by humoral immune responses. In this study, we generated five BTV16 VP5 protein-specific monoclonal antibodies (MAbs), named 3B11, 2B10, 1H7, 4A6 and 3G9, and defined the linear epitopes recognized by MAbs using a series of peptides expressed as maltose-binding protein (MBP)-fusion polypeptides. Three novel linear B-cell epitopes were identified: 3B11 and 3G9 recognized the motif ITANTREIQHIKEE; 2B10 recognized the motif LSGID; and 4A6 recognized the motif STMVKEYRQKIDALKA. Exact sequences corresponding to the three motifs identified were found in the BTV16 VP5 protein ((310)ITANTREIQHIKEE(323), (265)LSGID(269) and (188)STMVKEYRQKIDALKA(203)). These motifs represent the minimal linear peptide sequence required for MAb reactivity, as binding of each MAb was abolished when additional amino acids were removed from the amino and carboxy termini of the peptide. Amino acid sequence alignment indicated that three epitopes were totally conserved among different BTV16 strains. The MAbs generated along with identified epitopes will be useful for examining VP5 protein function and the development of epitope-based marker vaccines against BTV.

Monoclonal antibodies against VP7 of bluetongue virus.

VP7 is a major group-specific protein of the bluetongue virus (BTV), and is therefore a candidate for use as a diagnostic reagent. In this study, BALB/c mice were immunized with BTV16, and the lymphocyte hybridoma technique and indirect ELISA screening method were employed to obtain two strains of hybridoma cells secreting specific monoclonal antibodies (MAbs) to BTV16. Eukaryotic recombinant plasmids coding for 10 segments of BTV16 separately were transfected into BHK-21 cells, respectively, followed by immunofluorescence, showing that two MAbs only reacted with BTV-VP7. Western blot analysis showed the same result. Indirect immunofluorescence results indicated that two of the MAbs present different response spectrums with BTV1~24 serotypes. These results indicate that these MAbs may be good candidates for a specific diagnostic method and functional exploration of the VP7 protein.

Identification of two linear B-cell epitopes from West Nile virus NS1 by screening a phage-displayed random peptide library.

BACKGROUND: The West Nile virus (WNV) nonstructural protein 1 (NS1) is an important antigenic protein that elicits protective antibody responses in animals and can be used for the serological diagnosis of WNV infection. Although previous work has demonstrated the vital role of WNV NS1-specific antibody responses, the specific epitopes in the NS1 have not been identified. RESULTS: The present study describes the identification of two linear B-cell epitopes in WNV NS1 through screening a phage-displayed random 12-mer peptide library with two monoclonal antibodies (mAbs) 3C7 and 4D1 that directed against the NS1. The mAbs 3C7 and 4D1 recognized phages displaying peptides with the consensus motifs LTATTEK and VVDGPETKEC, respectively. Exact sequences of both motifs were found in the NS1 ((895)LTATTEK(901) and (925)VVDGPETKEC(934)). Further identification of the displayed B cell epitopes were conducted using a set of truncated peptides expressed as MBP fusion proteins. The data indicated that (896)TATTEK(901) and (925)VVDGPETKEC(934) are minimal determinants of the linear B cell epitopes recognized by the mAbs 3C7 and 4D1, respectively. Antibodies present in the serum of WNV-positive horses recognized the minimal linear epitopes in Western blot analysis, indicating that the two peptides are antigenic in horses during infection. Furthermore, we found that the epitope recognized by 3C7 is conserved only among WNV strains, whereas the epitope recognized by 4D1 is a common motif shared among WNV and other members of Japanese encephalitis virus (JEV) serocomplex. CONCLUSIONS: We identified TATTEK and VVDGPETKEC as NS1-specific linear B-cell epitopes recognized by the mAbs 3C7 and 4D1, respectively. The knowledge and reagents generated in this study may have potential applications in differential diagnosis and the development of epitope-based marker vaccines against WNV and other viruses of JEV serocomplex.

A rat model for studying neural stem cell transplantation.

AIM: The goal of this project was to develop a rat model for neural stem cell (NSC) transplantation studies in which NSCs were modified with brain-derived neurotrophic factor (BDNF) genes that may permit extensive and reliable analysis of the transplants. METHODS: NSCs were cultured and purified by limiting dilution assay in vitro and infected with recombinant retrovirus pLXSN-BDNF (BDNF-NSCs) and retrovirus pLXSN (p-NSCs). The expression of BDNF genes in transgenic and control NSC groups was measured by FQ-PCR and ELISA assays. NSCs were then transplanted into the subretinal space of normal rat retinas in four groups, which included NSCs alone, BDNF-NSCs, phosphate buffered saline (PBS) control, and normal control. Survival, migration, and differentiation of donor cells in host retinas were observed with optical coherence tomography (OCT), Heidelberg retina angiograph (HRA), and immunohistochemistry, respectively. RESULTS: The results obtained by FQ-PCR demonstrated that the copy numbers of BDNF gene templates from BDNF-NSCs were the highest among the four groups (P<0.05). Consistent with the results of FQ-PCR, BDNF protein level from the supernatant of the BDNF-NSCs group was much higher than that of the other two groups (P<0.05) as suggested by the ELISA assays. HRA and OCT showed that graft cells could successfully survive. Immunohistochemical analysis revealed that transplanted BDNF-NSCs could migrate in the host retinas and differentiate into glial cells and neurons three months after transplantation. CONCLUSION: BDNF promotes NSCs to migrate and differentiate into neural cells in the normal host retinas.

Study of brain-derived neurotrophic factor gene transgenic neural stem cells in the rat retina.

BACKGROUND: Neural stem cells (NSCs) transplantation and gene therapy have been widely investigated for treating the cerebullar and myelonic injuries, however, studies on the ophthalmology are rare. The aim of this study was to investigate the migration and differentiation of brain-derived neurotrophic factor (BDNF) gene transgenic NSCs transplanted into the normal rat retinas. METHODS: NSCs were cultured and purified in vitro and infected with recombinant retrovirus pLXSN-BDNF and pLXSN respectively, to obtain the BDNF overexpressed NSCs (BDNF-NSCs) and control cells (p-NSCs). The expression of BDNF genes in two transgenic NSCs and untreated NSCs were measured by fluorescent quantitative polymerase chain reaction (FQ-PCR) and enzyme-linked immunosorbent assay (ELISA). BDNF-NSCs and NSCs were infected with adeno-associated viruses-enhanced green fluorescent protein (AAV-EGFP) to track them in vivo and served as donor cells for transplantation into the subretinal space of normal rat retinas, phosphated buffer solution (PBS) served as pseudo transplantation for a negative control. Survival, migration, and differentiation of donor cells in host retinas were observed and analyzed with Heidelberg retina angiograph (HRA) and immunohistochemistry, respectively. RESULTS: NSCs were purified successfully by limiting dilution assay. The expression of BDNF gene in BDNF-NSCs was the highest among three groups both at mRNA level tested by FQ-PCR (P < 0.05) and at protein level measured by ELISA (P < 0.05), which showed that BDNF was overexpressed in BDNF-NSCs. The results of HRA demonstrated that graft cells could survive well and migrate into the host retinas, while the immunohistochemical analysis revealed that transplanted BDNF-NSCs differentiated into neuron more efficiently compared with the control NSCs 2 months after transplantation. CONCLUSIONS: The seed cells of NSCs highly secreting BDNF were established. BDNF can promote NSCs to migrate and differentiate into neural cells in the normal host retinas.

[Expression of human Id-2 gene in Escherichia coli and preparation of the antisera against human Id-2].

OBJECTIVE: To express the fusion protein of glutathione S-transferase (GST) and human Id-2 in E. coli and prepare the polyclonal antibodies against Id-2. METHODS: The coding sequence of Id-2 gene was amplified by RT-PCR from the total RNA of breast cancer tissue. The recombinant plasmid was identified by PCR, restriction endonuclease digestion analysis and sequencing. The fusion protein GST-Id-2 expressed in E. coli following IPTG induction was purified by glutathione-agarose affinity chromatography and used to immunize rabbits to prepare the polyclonal antibodies against GST-Id-2. RESULTS: PCR, restriction endonuclease digestion and sequence analyses showed that the Id-2 gene had been correctly inserted into pGEX-6P-1 vector, and the GST-Id-2 fusion protein expressed had a relative molecular mass of approximately 40,000 as shown by SDS-PAGE. The polyclonal antibodies obtained from the rabbit sera were found to specifically react with purified Id-2 by Western blotting, ELISA and agar gel immunodiffusion (AGP). CONCLUSION: The prepared polyclonal antibodies against Id-2 allow effective Id-2 detection and facilitate further investigation of the structure and antigen epitope of Id-2.

Long terminal repeat sequences from virulent and attenuated equine infectious anemia virus demonstrate distinct promoter activities.

In the early 1970s, the Chinese Equine Infectious Anemia Virus (EIAV) vaccine, EIAV(DLA), was developed through successive passages of a wild-type virulent virus (EIAV(L)) in donkeys in vivo and then in donkey macrophages in vitro. EIAV attenuation and cell tropism adaptation are associated with changes in both envelope and long terminal repeat (LTR). However, specific LTR changes during Chinese EIAV attenuation have not been demonstrated. In this study, we compared LTR sequences from both virulent and attenuated EIAV strains and documented the diversities of LTR sequence from in vivo and in vitro infections. We found that EIAV LTRs of virulent strains were homologous, while EIAV vaccine have variable LTRs. Interestingly, experimental inoculation of EIAV(DLA) into a horse resulted in a restriction of the LTR variation. Furthermore, LTRs from EIAV(DLA) showed higher Tat transactivated activity than LTRs from virulent strains. By using chimeric clones of wild-type LTR and vaccine LTR, the main difference of activity was mapped to the changes of R region, rather than U3 region.

[Identification of mimotope peptides which bind to the SARS-CoV spike protein specific monoclonal antibody 2C5 with phage-displayed peptides library].

To identify the epitope of SARS-CoV spike protein specific neutralizing monoclonal antibody (MAb) 2C5. The antibody was used as target and three rounds of bio-panning were conducted with phage-display peptide library. After the third panning, 20 phage-plague clones were randomly picked and analyzed for the binding ability with the MAb 2C5 by ELISA. The display sequence analysis demonstrated that among the twenty phage clones, eight clones displayed the same seven-peptide TPEQQFT. All these eight phage-clones showed strongest binding activity with 2C5 in phage ELISA analysis. Furthermore, phages displaying peptide TPEQQFT could specifically inhibit the binding of MAb 2C5 with SARS-CoV spike protein. The results demonstrated that TPEQQFT is a mimic epitope peptide containing neutralizing MAb 2C5. This study may provide information for further structural and functional analysis of spike protein and development vaccine for severe acute respiratory syndrome.