Discovery of novel DprE1 inhibitors via computational bioactivity fingerprints and structure-based virtual screening.

Decaprenylphosphoryl-ß-D-ribose oxidase (DprE1) plays important roles in the biosynthesis of mycobacterium cell wall. DprE1 inhibitors have shown great potentials in the development of new regimens for tuberculosis (TB) treatment. In this study, an integrated molecular modeling strategy, which combined computational bioactivity fingerprints and structure-based virtual screening, was employed to identify potential DprE1 inhibitors. Two lead compounds (B2 and H3) that could inhibit DprE1 and thus kill Mycobacterium smegmatis in vitro were identified. Moreover, compound H3 showed potent inhibitory activity against Mycobacterium tuberculosis in vitro (MICMtb = 1.25 µM) and low cytotoxicity against mouse embryo fibroblast NIH-3T3 cells. Our research provided an effective strategy to discover novel anti-TB lead compounds.

A Genetically Modified attenuated Listeria Vaccine Expressing HPV16 E7 Kill Tumor Cells in Direct and Antigen-Specific Manner.

Attenuated Listeria monocytogenes (L. monocytogenes, LM) induces specific CD8+ and CD4+ T cell responses, and has been identified as a promising cancer vaccine vector. Cervical cancer is the third most common cancer in women worldwide, with human papillomavirus (HPV), particularly type 16, being the main etiological factor. The therapeutic HPV vaccines are urgently needed. The E7 protein of HPV is necessary for maintaining malignancy in tumor cells. Here, a genetically modified attenuated LM expressing HPV16 E7 protein was constructed. Intraperitoneal vaccination of LM4Δhly::E7 significantly reduced tumor size and even resulted in complete regression of established tumors in a murine model of cervical cancer. We provided evidence that recombinant LM strains could enter the tumor tissue and induce non-specific tumor cell death, probably via activation of reactive oxygen species and increased intracellular Ca2+ levels. LM4Δhly::E7 effectively triggered a strong antigen-specific cellular immunity in tumor-bearing mice, and elicited significant infiltration of T cells in the intratumoral milieu. In summary, these data showed LM4Δhly::E7 to be effective in a cervical cancer model and LM4Δhly::E7 induced an antitumor effect by antigen-specific cellular immune responses and direct killing of tumor cells, indicating a potential application against cervical cancer.

Evaluation of Immunogenicity and Protective Efficacy Elicited by Mycobacterium bovis BCG Overexpressing Ag85A Protein against Mycobacterium tuberculosis Aerosol Infection.

Mycobacterium bovis bacillus Calmette-Guérin (BCG) is currently the only vaccine available for preventing tuberculosis (TB), however, BCG has varying success in preventing pulmonary TB. In this study, a recombinant BCG (rBCG::Ag85A) strain overexpressing the immunodominant Ag85A antigen was constructed, and its immunogenicity and protective efficacy were evaluated. Our results indicated that the Ag85A protein was successfully overexpressed in rBCG::Ag85A, and the Ag85A peptide-MHC complexes on draining lymph node dendritic cells of C57BL/6 mice infected with rBCG::Ag85A were detectable 4 h post-infection. The C57BL/6 mice infected with this strain had stronger antigen-specific interferon-gamma (IFN-γ) responses and higher antibody titers than those immunized with BCG, and the protective experiments showed that rBCG::Ag85A can enhance protection against Mycobacterium tuberculosis (M. tuberculosis) H37Rv infection compared to the BCG vaccine alone. Our results demonstrate the potential of rBCG::Ag85A as a candidate vaccine against TB.

[Prokaryotic expression and identification of HPV16 E7 protein].

HPV16 E7 fusion protein was expressed in E. coli BL21, and its applied value for HPV was evaluated. HPV16 E7 gene was amplified by PCR, and cloned into prokaryotic expression vector pGEX6p-1. The recombinant plasmid was transformed into E. coli BL21, and HPV16 E7 fusion was expressed through IPTG induction. The expressed product was analyzed by SDS-PAGE and Western blot, subsequently purified according to Glutathione Sepharose 4B purification procedure. An indirect ELISA with the purified fusion protein as the coating antigen was then established to detect E7 serum antibodies from mice immunized with recombinant Listeria monocytogenes delivering HPV16 E7. The results demonstrated that the soluble fusion protein was highly expressed at 25 degrees C after induction with 0.5 mM IPTG. Furthermore, the result of Western blot analysis showed that the fusion protein had good specific reaction with an anti-E7 monoclonal antibody. Indirect ELISA result confirmed that the fusion protein could detect the serum antibodies against E7 with a titer of 1:200. The expressed GST-E7 fusion protein was immunocompetent, which was useful in the research of E7 biological function and therapeutic vaccine.

[Preparation and characterization of monoclonal antibodies specific for CFP-10 protein of Mycobacterium tuberculosis.].

AIM: To prepare monoclonal antibodies (mAb) against CFP-10 protein of Mycobacterium tuberculosis. METHODS: BALB/c mice were immunized with the purified His-CFP-10 expressed in BL21 (DE3)-pET-30a(+)-lhp. With the purified GST-CFP-10 as detecting antigen, mAb-produced hybridoma cells against CFP-10 were screened by indirect ELISA. The specificity of the mAbs were characterized by indirect ELISA, Dot-ELISA and Western blot. RESULTS: Two hyridoma cell lines secreting mAbs against CFP-10 named 6E8, 2E7 were obtained. The immunoglobulin subclasses of 2 mAbs were IgG1 and IgG2b respectively, and the ELISA titers of 2 mAbs ascitic fluids were 1:1 000 000, 1:1 024 000 respectively. In Dot-ELISA test, the 2 mAbs could only react with BL21 (DE3)-pET-30a(+)-lhp, BL21-pGEX-6P-1-lhp, which expressed His-CFP-10, GST-CFP-10, respectively. Western blot analysis confirmed that the 2 mAbs could only react with CFP-10 protein. CONCLUSION: Two mAbs specific to CFP-10 protein of Mycobacterium tuberculosis were obtained, which may have important application value in further studies on diagnosis and pathogenesis.

[Perparation and characterization of the monoclonal antibodies against listeriolysin O].

AIM: To prepare the monoclonal antibodies (mAbs) against listeriolysin O (LLO), which is the major virulence factor of Listeria monocytogenes. METHODS: The BALB/c mice were immunized with the SDS-PAGE product of BL21(pGEX-6p-1-hly). The purified LLO-GST protein was used as antigen for detection. mAbs against LLO were prepared by using the lymphocyte hybridoma technique. The specificity of mAbs was characterized by Dot-ELISA and Western blot. RESULTS: Three hybridoma cell lines named 3B6, 4D1 and 5D10 secreting mAbs against LLO were obtained. The immunoglobulin subclasses of the mAbs were IgG1. The ELISA titer of the ascitic fluids of 3B6, 4D1 and 5D10 was 1:200,000, 1:200,000 and 1:100,000, respectively. Western blot analysis confirmed the three mAbs reacted on fusion protein LLO-GST but didn't react on protein GST. Dot-ELISA proved the three mAbs only react on the bacteria expressing LLO. CONCLUSION: The successful preparation of three mAbs specific to protein LLO lays a foundation for further study of the biological characteristics of LLO and the pathogenesis of Listeria monocytogenes.

[Immunogenicity of S1 gene DNA vaccine of mouse hepatitis virus delivered by attenuated Salmonella typhimurium].

The complete S1 gene from mouse hepatitis virus (MHV) was amplified by RT-PCR and cloned into the pMD18-T vector. After confirmed by the restriction endonuclease analysis and PCR amplification, the positive clone of S1 gene was sequenced and then was transferred into eukaryotic expressing vector pVAXI. The recombinant plasmid pVAX1-S1 was transfected into COS-7 cells. The expressed S1 protein was successfully detected with indirect immunofluorescent assay. Finally, The recombinant plasmid pVAX1-S1 was transformed by electroporation into attenuated Salmonella typhimurium strain SL7207 and confirmed by PCR and Salmonella agglutination test. The recombinant was named as SL7207(pVAX1-S1). 6-week-old BALB/c mice were inoculated orally with SL7207 (pVAX1-S1) at dosage of 5 x 10 (8) CFU, 1 x 10(9) CFU and 2 x 10(9) CFU respectively. The immunized mice showed no clinic symptom. The results suggested that SL7207 (pVAX1-S1) was safe for mice after oral immunization at dosage of 2 x 10(9) CFU or below. BALB/c mice were immunized orally with SL7207 harboring recombinant plasmid at the dosage of 109 and boosted two weeks later with the same dose, for a total of three times. The recombinant Salmonella SL7207 ( pVAX1-S1 ) could induce significant humoral immune response in mice compared with the control (P < 0.05 or 0.01) at 2 w post-boosting and 2 w post-three immunization. The antibodies against MHV were also detected in small intestinal mucosal samples from immunized mice at 2 w post-three immunization. These results indicated that recombinant SL7207(pVAX1-S1) induced both systemic and local mucosal immunity.

[Expression of actA gene of Listeria monocytogenes in Escherichia coli and preparation of ActA monoclonal antibodies].

The actA gene was amplified from Lm-4 strain of Listeria monocytogenes serotype 1/2a by PCR and inserted into T vector. Sequencing showed actA gene was 1833bp long and nucleotide homology was 100% compared with actA gene of Listeria monocytogenes EGD strain in GenBank. The cloned actA gene was then inserted into prokaryotic expression vector pGEX-6P-1 and pET respectively. The predicted fusion protein was detected by SDS-PAGE after IPTG induction of recombinant bacteria. The fusion protein expressed in both vectors showed approximate molecular weight of 120kDa and 97kDa. The expressed fusion protein His-ActA was purified and used as antigen to immunize BALB/c mice, hybridomas were generated with traditional hybridoma techniques. McAbs were screened by ELISA, four hybridoma cell lines secreting antibodies against ActA protein were established and the ELISA titer of these ascitic McAbs were around 1 :5 x 10(4) - 1: 1 x 10(5) . The subtype and specifity of McAbs were identified by kit and Western blot. The McAb 1A5 reacted with the expressed fusion protein GST-ActA and His-ActA in Western blot, consistent with that of mouse anti-Lm-4 polyclonal antibodies. The successful expression of ActA protein in E. coli and preparation of its monoclonal antibodies has provided useful tools for studies on the biological activity of ActA protein and its role in listerial pathogenesis.

[Construction and characterization of Salmonella typhimurium SL7207 SifA- mutant strain].

One characteristic of Salmonella typhimurium SifA- mutant strain is to enter the cytosol of eukaryotic cells. The SifA- mutation of S. typhimurium P3H6 was transferred into S. typhimurium vaccine vector SL7207 by P22 phage transduction and the new strain was named as SL7207*. SL7207* had similar growth curve in LB medium and similar invasiveness for eukaryotic cells. It was found that SL7207* replicates within MDCK cells at a higher rate than SL7207, but is defective for replication in macrophage cell line RAW264.7. SL7207* was more attenuated than SL7207 in BALB/c mice when innoculated intraperitoneally or intravenously. SL7207*, but not SL7207, could transfer eukaryotic expression plasmid into RAW264.7 cells. These results showed that SL7207* could be a promising candidate vaccine vector to express foreign antigen or act as a eukaryotic expression plasmid carrier.

[Safety and efficacy of attenuated Salmonella typhimurium harbouring DNA vaccine against Newcastle disease virus].

A pair of primers were designed and synthesized according to the previously published sequence of fusion protein (F) gene of Newcastle disease virus (NDV) and used to amplify F gene by reverse-transcription polymerase chain reaction (RT-PCR) from the genomic RNA of a NDV strain JS5 isolated from goose. The PCR product was identified by sequencing. Then recombinant eukaryotic expression vector pVAX1-F was constructed through inserting F gene into MCS of pVAX1. The recombinant plasmid pVAX1-F was transfected in COS-7 cells, and identified for the transient expression of F gene by indirect immunofluorescent assay. Finally, the recombinant plasmid was transformed into attenuated Salmonella typhimurium SL7207, and the recombinant was screened and designated as SL7207 (pVAX1-F). It was verified that SL7207 (pVAX1-F) as the oral NDV DNA vaccine was safe for chickens after oral immunization at dosage of 10(10) CFU or below. 1-day-old commercial ISA brown chickens were immunized orally with SL7207 (pVAX1-F) at two different dosages (10(9) CFU and 10(8) CFU) on day 1, 14 and 28. On day 7 after the last immunization, no significant difference was observed in the body weight between these two groups (p > 0.05), and also no significant difference between those two groups and negative control group (p > 0.05). Since there were maternal antibodies, high ELISA titers of serum antibodies against NDV were detected in the chickens of all groups on day 14. However, the levels of serum antibodies were decreased in the chickens of all groups on day 28, but the anti-NDV antibody response detected in the sera of chickens immunized with SL7207 (pVAX1-F) at the dosage of 10(9) CFU were increased and significantly higher than the response induced by immunization with SL7207 (pVAX1) on day 35 (p < 0.05). Intestinal mucosal immune response was observed in chickens immunized with SL7207 (pVAX1-F) at the dosage of 10(9) CFU or 10(8) CFU. The high ELISA titers of antibodies against NDV in small intestinal mucosal samples from immunized chickens were on day 28 and 35. After challenged intranasally with virulent NDV strain F48E8, the chickens immunized with SL7207 (pVAX1-F) at the dosage of 10(9) CFU could be protected with the protective rate of 77.27%, significantly higher than those with SL7207 (pVAX1) (p < 0.05). In summary, the DNA vaccine delivered by attenuated Salmonella typhimurium was safe and has good immunogenicity for chickens. A novel mucosal DNA vaccine was developed and could be useful for controlling the infection and epidemic of ND in the poultry.

[Prokaryotic expression and bioactivity of the Listeria monocytogenes listeriolysin O].

To express the Listeria monocytogenes hly gene in Escherichia coli and study its primary biological characteristics, hly gene without signal peptide sequence was amplified from Listeria monocytogenes serotype 4b by PCR and inserted into T-easy vector. Sequencing showed this hly gene was 1518 bp and nucleotide homology was more than 99.8% compared with three Listeria monocytogenes hly genes in GenBank. The cloned hly gene was then inserted into prokaryotic expression vector pGEX-6P-1 and transformed into E. coli BL21. The predicted fusion protein was detected by SDS-PAGE after IPTG inducion, which had molecular weight approximately 82 kD. Hemolytic experiment demonstrated the expressed fusion protein can lyse human red cell and its hemolytic titer attained 2.26 x 10(4) HU/mg. Conclusively, the Listeria monocytogenes hly gene was successfully cloned and expressed in E. coli. The successful expression of LLO in E. coli BL21 constituted a solid foundation for further researches such as pathogenesis and immune mechanism, MAb and vaccine development.