Antigen 43/Fcε3 chimeric protein expressed by a novel bacterial surface expression system as an effective asthma vaccine.

The IgE Fcε3 domain is an active immunotherapeutic target for asthma and other allergic diseases. However, previous methods for preparing IgE fusion protein vaccines are complex. Antigen 43 (Ag43) is a surface protein found in Escherichia coli that contains α and ß subunits (the α subunit contains multiple T epitopes). Here we constructed a novel Ag43 surface display system (Ag43 system) to express Ag43 chimeric proteins to disrupt immune tolerance against IgE. The Ag43 system was constructed from the E. coli strain Tan109, in which the Ag43 gene was deleted and a recombinant plasmid (pETAg43) expressing a partial Ag43 gene was introduced. The Fcε3 domain of the IgE gene was then subcloned into plasmid pETAg43, resulting in a recombinant plasmid pETAg43/Fcε3, which was used to transform Tan109 for Ag43/Fcε3 surface expression. Thereafter, Ag43/Fcε3 was investigated as an asthma vaccine in a mouse model. Ag43/Fcε3 was expressed on and could be separated from the bacterial surface by heating to 60° while retaining activity. Ag43/Fcε3, as a protein vaccine, produced neutralizing autoantibodies to murine IgE, induced significant anti-asthma effects, and regulated IgE and T helper cytokines in a murine asthma model. Data show that Ag43/Fcε3 chimeric protein is a potential model vaccine for asthma treatment, and that the Ag43 system may be an effective tool for novel vaccine preparation to break immune tolerance to other self-molecules.

Bacterial surface display of endoglin by antigen 43 induces antitumor effectiveness via bypassing immunotolerance and inhibition of angiogenesis.

Various angiogenesis-related self-molecules have been considered to be therapeutic targets. However, the direct use of self-molecules as vaccines is not recommended because of the inherent ability of the host to develop immune tolerance. Antigen 43 (Ag43) is a surface protein found in E. coli and contains an α and a ß subunits, which contains multiple T epitopes in α subunit. Here we construct a novel Ag43 surface display system (Ag43 system) to express Ag43 chimeric proteins to disrupt immune tolerance against self-molecules. The Ag43 system was constructed from an Escherichia coli strain Tan109, derived from JM109, in which the Ag43 gene was deleted and a recombinant plasmid (pETAg43') expressing a partial Ag43 gene was introduced. The extracellular domain of angiogenesis-related endoglin gene was then subcloned into plasmid pETAg43', resulting in a recombinant plasmid pETAg43'/END(e) which was then used to transform Tan109 for protein expression. We found that Ag43 and endoglin chimeric protein (Ag43'/END(e) ) was expressed on the bacterial surface. The chimeric protein could be separated from the bacterial surface by heating to 60°C and yet retain activity. We used Ag43'/END(e) as a protein vaccine and found that it could disrupt immune tolerance against endoglin by inducing significant antitumor activities and inhibit angiogenesis in several tumor models without significant side effects. These data suggest that Ag43'/END(e) chimeric protein is a potential model vaccine for active tumor immunotherapy, and that Ag43 system could be an effective tool for novel vaccine preparation to break immune tolerance to other angiogenesis-related self-molecules for cancer therapy.

Evaluation on the immune response induced by DNA vaccine encoding MIC8 co-immunized with IL-12 genetic adjuvant against Toxoplasma gondii infection.

OBJECTIVE: To examine the immunoprotection effect induced by MIC8 DNA vaccine co-immunized with a plasmid encoding murine IL-12 (pcIL-12) as an adjuvant in mice against the challenge of Toxoplasma gondii. METHODS: The gene sequence encoding MIC8 of T. gondii RH strain was inserted into eukaryotic expression vector pcDNA3.1 to construct the pcMIC8 expression plasmid. The recombinant plasmid was transfected into HeLa cells to test its expression and the recombinant protein was then characterized by Western blotting. Eighty Kunming mice were randomly divided into 5 groups (16 per group): 3 control groups (PBS, pcDNA3.1, and pcIL-12), pcMIC8 group, and pcMIC8 plus pcIL-12 group. Mice in the pcMIC8 plus pcIL-12 group were co-injected intramuscularly at a dosage of 100 microl each of pcMIC8 and pcIL-12 suspended in 100 microg sterile PBS. Mice in other groups were inoculated with PBS, pcDNA3.1, pcIL-12, and pcMIC8 respectively following the same protocol. All the mice received three immunizations at 2-week intervals. Serum samples were collected on day 0, 13, 27, 41, and 55 before each inoculation for determining antibody IgG, IgG subclass IgG2a. Four weeks after the final immunization, IFN-gamma and IL-4 levels in splenocytes cultures from immunized mice were detected by ELISA. The mice were challenged with 10(3) tachyzoites of the virulent T. gondii RH strain three weeks after the last immunization to observe the survival time. RESULTS: Western blotting showed that the protein extracts in HeLa cells upon transfection with pcMIC8 were effectively expressed in cells. The levels of IgG (0.51 +/- 0.028) and IgG2a (0.261 +/- 0.04)(on day 55) in mice immunized with pcMIC8 plus pcIL-12 were higher than pcMIC8 group (497.65 +/- 98.15) and control groups (PBS 47.18 +/- 2.73, pcDNA3.1 50.08 +/- 4.62, pcIL-12 118.15 +/- 12.73) (P < 0.05). There was no significant difference in the level of IgG 1 and IL-4 among the five groups (P > 0.05). After a lethal challenge of T. gondii RH strain, the survival time in mice immunized with pcMIC8 plus pcIL-12 (15d) was prolonged in comparison to that of pcMIC8 (10d) and control groups (PBS 5 d, pcDNA3.1 6d, pcIL-12 8 d) (P < 0.05). CONCLUSION: The immune responses induced by the combined use of the recombinant plasmid encoding MIC8 of T. gondii with murine IL-2 gene adjuvant can be enhanced.

[Immune response in mice induced by complex gene vaccine pcSAG1-ROP5 of Toxoplasma gondii].

OBJECTIVE: To observe the immune response induced by complex gene vaccine pcSAG1-ROP5 of Toxoplasma gondii in mice. METHODS: The recombinant eukaryotic expression plasmids pcSAG1, pcROP5 and pcSAG1-ROP5 were constructed and identified by PCR, restriction enzyme digestion, and sequencing. The three recombinant plasmids were transfected into HeLa cells to express in vitro and identified by Western blotting analysis. Seventy Kunming mice were randomly divided into 5 groups with 14 each, i.e. pcSAG1 group, pcROP5 group, pcSAG1-ROP5 group, blank plasmid group and PBS control group. The mice were immunized intramuscularly with pcSAG1, pcROP5, pcSAG1-ROP5, pcDNA3.1, and PBS, respectively, every two weeks for three times. Sera were collected before each injection and 2 weeks after the last immunization. The titer of mice serum in pcSAG1-ROP5 group combined with recombinant protein SAG1, ROP5 and SAG1-ROP5 and the level of IgG against T. gondii in 5 groups were determined by ELISA. Three weeks after the last immunization, ten mice of each group were challenged with 10(3) tachyzoites of the virulent T. gondii RH strain to observe the survival time. One week later, the rest four mice in each group were sacrificed and the supernatant of cultured splenocytes was collected for the detection of IFN-gamma and IL-4. RESULTS: Western blotting showed that the recombinant plasmids pcSAG1, pcROP5 and pcSAG1-ROP5 were expressed in HeLa cells with M(r) 31 000, 57 000, and 88 000, respectively. The serum titer in pcSAG1-ROP5 group combined with SAG1, ROP5 and SAG1-ROP5 was 1:320, 1:160, and 1:2560, respectively. The IgG level kept rising in pcSAG1, pcROP5 and pcSAG1-ROP5 groups. Two weeks after the last immunization, the IgG level in pcSAG1-ROP5 group was higher than those in other groups (P<0.05). After a lethal challenge of T. gondii RH strain, the survival time of the mice in pcSAG1-ROP5 group was (288 +/- 7) h, which was 48 h and 96h longer than the groups of pcSAG1 and pcROP5, respectively (P< 0.05). Four weeks after the last immunization, IFN-gamma in splenocyte culture of pcSAG1-ROP5 group [(908.52 +/- 6.31) pg/ml] was higher than other groups (P<0.05), with no significant difference in IL-4 (P>0.05). CONCLUSION: Compared with the single gene vaccines pcSAG1 and pcROP5, higher levels of IgG and IFN-gamma and longer survival time are observed in mice immunized with pcSAG1-ROP5.

[Antitumor effect of adriamycin conjugated with downsized anti-endoglin monclonal antibody].

OBJECTIVE: To study the antitumor efficacy of an immunoconjugate composed of adriamycin (ADM) and downsized Fab fragment of mouse anti-Endoglin monoclonal antibody. METHODS: The Fab fragment of mouse anti-Endoglin monoclonal antibody was downsized and conjugated with ADM by m-Maleimidobenzoyl-N-hydroxysuccinimide ester (MBS). The antitumor effect of the conjugate was tested in mice bearing subcutaneous injection of H22 tumor in vivo. RESULTS: The molecular ratio of Fab:ADM in conjugate was approximately 1:2. The Fab-ADM conjugate inhibited the growth of H22 by 91.94% on day 14 after injection at the dose of 0.4 mg/ kg, much higher the inhibition rate of 25.00% by the equivalent dose of free ADM. The median survival time of the mice treated with the conjugate was longer than those treated with free ADM. The Fab-ADM conjugate was significantly more effective than free ADM in tumor suppression and life span prolongation. CONCLUSION: Fab -ADM displayed more significant antitumor efficacy than free ADM in vivo and might be a novel candidate for cancer treatment.

Toxicarioside N induces apoptosis in human gastric cancer SGC-7901 cell by activating the p38MAPK pathway.

Natural plant compounds with potent proliferation inhibition and apoptosis induction properties have been screened as novel anticancer drugs. Toxicarioside N (Tox N) was isolated from the seeds of the tropical plant Antiaris toxicaria in Hainan province, China. To our knowledge, the effects that Tox N has on the apoptosis of SGC-7901 cells and its potential mechanism have never been investigated. In this study, we detected the anticancer activities of Tox N and explored the potential mechanism in the human gastrointestinal cancer cell line SGC-7901. Here, we found that Tox N inhibited SGC-7901 cell growth in a dose- and time-dependent manner and induced apoptosis in cells based on cell morphology and flow cytometry analyses. Additionally, the SGC-7901 cell treated with Tox N up-regulated the expression level of cleaved caspase-3/9 and PARP, increased the Bax/Bcl-2 ratio, and led to the release of cytochrome c into the cytoplasm. In addition, Tox N treatment led to the phosphorylation of p38MAPK. SB203580, a p38MAPK inhibitor, partially attenuated Tox N induced apoptosis by preventing the activation of caspase-3/9 and PARP. Our results indicated for the first time that Tox N can induce SGC-7901 cells apoptosis by activating the p38MAPK pathway.

Autophagy plays a protective role against apoptosis induced by toxicarioside N via the Akt/mTOR pathway in human gastric cancer SGC-7901 cells.

Toxicarioside N (Tox N), a natural product extract from Antiaris toxicaria, has been reported to induce apoptosis in human gastric cancer cells. However, the mechanism and actual role of autophagy in Tox N-induced apoptosis of human gastric cancer cells remains poorly understood. In the current study, we demonstrated that Tox N could induce autophagy by inhibiting the Akt/mTOR signaling pathway in SGC-7901 cells. Moreover, we found that the inhibition of autophagy by 3-methyladenine, an autophagy inhibitor, enhanced Tox N-induced apoptotic cell death. However, the stimulation of autophagy by rapamycin, an autophagy activator, remarkably suppressed Tox N-induced apoptosis, suggesting that autophagy plays a protective role in Tox N-induced apoptosis. Thus, the results from this study suggested that Tox N combination with an autophagy inhibitor might be a promising strategy to enhance the anticancer activity of Tox N for the treatment of human gastric cancer.

Penicilazaphilone C, a new antineoplastic and antibacterial azaphilone from the Marine Fungus Penicillium sclerotiorum.

Two azaphilonidal derivatives [penicilazaphilones B (1) and C (2)], have been isolated from the fermented products of marine fungus strain Penicillium sclerotiorum M-22, penicilazaphilones C was a new compound. The compound's structures were identified by the analysis of spectroscopic data including 1D and 2D NMR techniques (1H-NMR, 13C-NMR, COSY, HMQC, and HMBC). Biological evaluation revealed that penicilazaphilones B and C showed selective cytotoxicity against melanoma cells B-16 and human gastric cancer cells SGC-7901 with IC50 values of 0.291, 0.449 and 0.065, 0.720 mM, respectively, while exhibiting no significant toxicity to normal mammary epithelial cells M10 at the same concentration. Moreover, penicilazaphilones C also exhibited strong antibacterial activity against Staphylococcus aureus, Pseudomonas aeruginosa, Klebsiella pneumonia and Escherichia coli with MIC values 0.037-0.150 mM, while penicilazaphilones B's bacteriostatic action was weaker.

Microencapsulation of tumor lysates and live cell engineering with MIP-3α as an effective vaccine.

The combination of several potential strategies so as to develop new tumor vaccines is an attractive field of translational medicine. Pulsing tumor lysates with dendritic cells (DCs), in-vivo attraction of DCs by macrophage inflammatory protein 3α (MIP-3α), and reversion of the tumor suppressive microenvironment have been tested as strategies to develop tumor vaccines. In this study, we generated an alginate microsphere (named PaLtTcAdMIP3α) that encapsulated tumor lysates, live tumor cells engineering with a recombinant MIP-3α adenovirus and BCG. We used PaLtTcAdMIP3α as a model vaccine to test its antitumor activities. Our results showed that PaLtTcAdMIP3α expressed and excreted MIP-3α, which effectively attracted DCs ex vivo and in vivo. Injection of PaLtTcAdMIP3α into tumor-bearing mice effectively induced both therapeutic and prophylactic antitumor immunities in CT26, Meth A, B16-F10 and H22 models, but without any ensuing increase in adverse effects. Both tumor-specific cellular and humoral immune responses, especially the CD8(+) T cell-dependent cytotoxic T immunity, were found in the mice injected with PaLtTcAdMIP3α. The anti-tumor activity was abrogated completely by depletion of CD8(+) and partially by CD4(+) T lymphocytes. In addition, the number of IFN-γ-producing CD8(+) T cells in spleen and tumor tissues was significantly increased; but the number of CD4(+)CD25(+)FOXP3(+) regulatory T cells (Treg) in tumor tissues was decreased. These data strongly suggest that a combination of multi-current-using strategies such as the novel approach of using our PaLtTcAdMIP3α microspheres could be an effective tumor model vaccine.

Cytochalasin D promotes pulmonary metastasis of B16 melanoma through expression of tissue factor.

Cytochalasin D (CytD) targets actin, a ubiquitous protein in eukaryotic cells. Previous studies have focused mainly on the antitumor effects of CytD. We previously found CytD to promote lung metastasis in B16 melanoma cells, which we had not anticipated, and, therefore, in the present study we investigated the possible underlying mechanisms. B16 melanoma cells were co-cultured with CytD and other agents and used to establish a lung metastatic model. In this B16 melanoma metastatic model, significantly increased lung metastasis and lung weight were found in CytD-treated mice, which was almost completely suppressed by tissue factor (TF) RNA interference expressed via lentivirus. The results of northern and western blot, and real-time RT-PCR analysis showed that the expression of TF was significantly upregulated in B16 cells treated with CytD but was significantly inhibited by TF RNA interference. In addition, upregulation and phosphorylation of mitogen-activated protein kinase p38 were also found in the metastatic lung tissues treated with CytD and in the B16 cells co-cultured with CytD and factor VIIa (FVIIa), but not in cells cultured with CytD, dimethyl sulfoxide or FVIIa alone. These results indicate that CytD stimulates the expression of TF in B16 melanoma cells, activating both coagulation-dependent and -independent pathways via binding to FVIIa, eventually promoting lung metastasis. TF interference is a potential approach to the prevention of B16 melanoma metastasis.

The antitumour activities induced by pegylated liposomal cytochalasin D in murine models.

Cytochalasin D targets actin and is ubiquitous in eukaryotic cells. When cytochalasin D is used as a cytotoxic agent in cancer therapy, it causes significant side effects. To prevent this, cytochalasin D can be encapsulated in polyethylene liposomes. In this study, high-performance liquid chromatography observation of the biodistribution of pegylated liposomal cytochalasin D in tumour-bearing mice showed that liposomal cytochalasin D could be conveniently dissolved in water for i.v. injection and that it specifically accumulated in tumour tissues, more than natural cytochalasin D did. The half-time of liposomal cytochalasin D in the plasma was also significantly longer than that of natural cytochalasin D (4h versus 10 min). MTT 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay showed that liposomal cytochalasin D treatment could cause significant inhibition of cell proliferation in vitro in a manner similar to that of natural cytochalasin D. The antitumour activities of liposomal cytochalasin D were investigated in B16 melanoma, CT26 colorectal carcinoma and H22 hepatoma models, and the results indicated that liposomal cytochalasin D could significantly inhibit tumour growth and prolong survival in a manner similar to that of cisplatin. TUNEL-based apoptosis assays showed that liposomal cytochalasin D induced significant tumour cell apoptosis. Significant inhibition of tumour angiogenesis was observed in mice treated with liposomal cytochalasin D. In addition, no significant side effects were observed in mice treated with liposomal cytochalasin D. Our results show that liposomal cytochalasin D increases solubility and bioavailability, a lower incidence of side effects and improves antitumour effects, indicating its potential as a chemical agent for cancer therapy.

Toxicarioside A inhibits tumor growth and angiogenesis: involvement of TGF-ß/endoglin signaling.

Toxicarioside A is a cardenolide isolated mainly from plants and animals. Emerging evidence demonstrate that cardenolides not only have cardiac effects but also anticancer effects. In this study, we used in vivo models to investigate the antitumor activities of toxicarioside A and the potential mechanisms behind them. Murine colorectal carcinoma (CT26) and Lewis lung carcinoma (LL/2) models were established in syngeneic BALB/c and C57BL/6 mice, respectively. We found that the optimum effective dose of toxicarioside A treatment significantly suppressed tumor growth and angiogenesis in CT and LL/2 tumor models in vivo. Northern and Western blot analysis showed significant inhibition of endoglin expression in toxicarioside A-treated human umbilical vein endothelial cells (HUVECs) in vitro and tumor tissues in vivo. Toxicarioside A treatment significantly inhibited cell proliferation, migration and invasion, but did not cause significant cell apoptosis and affected other membrane protein (such as CD31 and MHC I) expression. In addition, TGF-ß expression was also significantly inhibited in CT26 and LL/2 tumor cells treated with toxicarioside A. Western blot analysis indicated that Smad1 and phosphorylated Smad1 but not Smad2/3 and phosphorylated Smad2/3 were attenuated in HUVECs treated with toxicarioside A. Smad1 and Smad2/3 signaling remained unchanged in CT26 and LL/2 tumor cells treated with toxicarioside A. Endoglin knockout by small interfering RNA against endoglin induced alternations in Smad1 and Smad2/3 signaling in HUVECs. Our results indicate that toxicarioside A suppresses tumor growth through inhibition of endoglin-related tumor angiogenesis, which involves in the endoglin/TGF-ß signal pathway.