N-glycosylation modification of heat shock protein gp96 affects its immunological function / 生物工程学报

N-glycosylation modification, one of the most common protein post-translational modifications, occurs in heat shock protein gp96. The purpose of this study is to investigate the effect of N-glycosylation modification on immunologic function of the recombinant gp96 using the mutant gp96 in N-glycosylation sites. Firstly, wild-type and mutant gp96 proteins were expressed by insect expression system and their glycosylation levels were detected. To determine the effect of N-glycosylation on gp96 antigen presentation function, the IFN-γ+ CD8+ T cells in gp96-immunized mice and secretion level of IFN-γ were examined by flow cytometry and ELISA. The ATPase activity of gp96 was further detected by the ATPase kit. Finally, the effect of N-glycosylation on adjuvant function of gp96 for influenza vaccine was investigated in immunized mice. It was found that total sugar content of mutant recombinant gp96 was reduced by 27.8%. Compared to the wild type recombinant gp96, mutations in N-glycosylation sites resulted in decreased antigen presentation ability and ATPase activity of gp96. Furthermore, influenza vaccine-specific T cell levels induced by mutant gp96 as adjuvant were dramatically reduced compared to those by wild type recombinant gp96. These results demonstrate that N-glycosylation modification is involved in regulation of ATPase activity and antigen presentation function of gp96, thereby affecting its adjuvant function. The results provide the technical bases for development of gp96- adjuvanted vaccines.

Research progress of AFP in the diagnosis and therapy of hepatocellular carcinoma / 生物工程学报

Hepatocellular carcinoma (HCC) is the third leading cause of cancer-related deaths and the fifth most common cancer worldwide. Clinically therapeutic options for HCC are very limited, and the overall survival rate of patients is very low. Therefore, early diagnosis and treatment of HCC have important impact on overall survival of patients. At present, alpha-fetoprotein (AFP) is one of the most widely used serological markers for HCC. Many evidences have shown that as a specific onco-protein, AFP has great research value in the occurrence, development, diagnosis and treatment of HCC. Here, we briefly introduce the molecular mechanism of AFP in the regulation of HCC occurrence and development, and its role in tumor escape from immune surveillance. We focus on the application of AFP as an important HCC target or carcino-embryonic antigen (CEA) in HCC clinical diagnosis and treatment.

Recent advances in the development of bispecific antibodies / 生物工程学报

Bispecific antibody (BsAbs) are antibodies (Abs) containing two different antigen-binding sites in one molecule. In the last decade, three BsAbs drugs have been approved for therapeutic use. Meanwhile there are a number of BsAbs in preclinical or clinical studies. In this review, we describe BsAb design, discovery, mechanism of action, and the recent research progress in developing BsAbs.

CD133 epitope vaccine with gp96 as adjuvant elicits an antitumor T cell response against leukemia / 生物工程学报

Cancer stem cells are currently under intensive investigation due to their capabilities for tumor initiation, self-renewal, and resistance to chemotherapy. CD133 is implicated in stemness and the malignancy of tumor cells. Here, we explored heat shock protein gp96 adjuvanted CD133 epitope vaccine against leukemia. We screened and identified three H2-Kd-restricted cytotoxic T lymphocyte (CTL) epitopes derived from CD133, CD133₄₁₉₋₄₂₈, CD133₇₀₂₋₇₁₀ and CD133₇₆₀₋₇₆₉. The immunogenicity and antitumor activity of the epitope vaccine using heat shock protein gp96 as adjuvant were further determined in CD133⁺ leukemia xenograft mice. Finally, we demonstrate that adoptive transfer of epitope-specific CTLs led to suppression of leukemia growth. Our data therefore provide the basis for designing a CD133 epitope vaccine to activate specific CTLs against CD133⁺ leukemia and other cancers.

High-dose heat shock protein gp96 immunization prevents type 1 diabetes via inducing regulatory T cells / 生物工程学报

Type 1 diabetes (T1D), the most prevalent human autoimmune disease, occurs in genetically susceptible individuals. Regulatory T cells (Tregs) are defective in T1D setting. Therefore, efforts to repair or restore Tregs in T1D may prevent or reverse this autoimmune disease. Here, we studied the potential role of rgp96 in preventing T1D, using non-obese diabetic (NOD) mice as an animal model. High-dose rgp96 immunization elicited efficient protection of mice against T1D, as evidenced by stable blood glucose, decreased disease incidence. Significantly increased CD4⁺ CD25⁺ Foxp3⁺ Tregs were observed in immunized mice. In vitro co-culture experiments demonstrated that rgp96 stimulation enhanced Treg proliferation and suppressive function by up-regulation of Foxp3 and IL-10. Our work shows that activation of Tregs by high-dose rgp96 immunization protects against T1D via inducing regulatory T cells and provides preventive and therapeutic potential for the development of an rgp96-based vaccine against T1D.

A new unconventional HLA-A2-restricted epitope from HBV core protein elicits antiviral cytotoxic T lymphocytes

Cytotoxic T cells (CTLs) play a key role in the control of Hepatitis B virus (HBV) infection and viral clearance. However, most of identified CTL epitopes are derived from HBV of genotypes A and D, and few have been defined in virus of genotypes B and C which are more prevalent in Asia. As HBV core protein (HBc) is the most conservative and immunogenic component, in this study we used an overlapping 9-mer peptide pool covering HBc to screen and identify specific CTL epitopes. An unconventional HLA-A2-restricted epitope HBc141-149 was discovered and structurally characterized by crystallization analysis. The immunogenicity and anti-HBV activity were further determined in HBV and HLA-A2 transgenic mice. Finally, we show that mutations in HBc141-149 epitope are associated with viral parameters and disease progression in HBV infected patients. Our data therefore provide insights into the structure characteristics of this unconventional epitope binding to MHC-I molecules, as well as epitope specific CTL activity that orchestrate T cell response and immune evasion in HBV infected patients.

Competitive virus and host RNAs: the interplay of a hidden virus and host interaction

During virus infection, viral RNAs and mRNAs function as blueprints for viral protein synthesis and possibly as pathogen-associated molecular patterns (PAMPs) in innate immunity. Here, considering recent research progress in microRNAs (miRNAs) and competitive endogenous RNAs (ceRNAs), we speculate that viral RNAs act as sponges and can sequester endogenous miRNAs within infected cells, thus cross-regulating the stability and translational efficiency of host mRNAs with shared miRNA response elements. This cross-talk and these reciprocal interactions between viral RNAs and host mRNAs are termed "competitive viral and host RNAs" (cvhRNAs). We further provide recent experimental evidence for the existence of cvhRNAs networks in hepatitis B virus (HBV), as well as Herpesvirus saimiri (HVS), lytic murine cytomegalovirus (MCMV) and human cytomegalovirus (HCMV) infections. In addition, the cvhRNA hypothesis also predicts possible cross-regulation between host and other viruses, such as hepatitis C virus (HCV), HIV, influenza virus, human papillomaviruses (HPV). Since the interaction between miRNAs and viral RNAs also inevitably leads to repression of viral RNA function, we speculate that virus may evolve either to employ cvhRNA networks or to avoid miRNA targeting for optimal fitness within the host. CvhRNA networks may therefore play a fundamental role in the regulation of viral replication, infection establishment, and viral pathogenesis.

Expression of anti-gp96 scFv fragment in Pichia pastoris and identification of its biological activity / 生物工程学报

Secretory anti-gp96 scFv fragment was expressed in Pichia pastoris to obtain a small molecule antibody that specifically recognizes heat shock protein gp96. The gp96-scFv fragment gene was synthesized and cloned to Pichia pastoris expression plasmid pPICZa-A. Pichia pastoris X33 was electroporated with the linearized recombinant expression vector, and expression of gp96-scFv fragment was induced by methanol. The His-tagged recombinant protein was then purified by affinity chromatography and analyzed with SDS-PAGE and Western blotting assays. The biological activities of recombinant gp96-scFv fragment were determined by Western blotting, Immunofluorescence, ELISA and FACS assays. The gp96-scFv fragment was expressed successfully in Pichia pastoris. About 50 mg of recombinant protein could be purified from 1 liter of the Pichia pastoris culture supernatant. Its molecular weight was about 15 kDa. The gp96-scFv fragment could specifically bind to gp96 protein by Western blotting, immunofluorescence, ELISA and FACS analyses. Pichia pastoris-expressed gp96-scFv fragment specifically recognizes gp96 protein, which could be used for Western blotting, Immunofluorescence, ELISA and FACS analyses.

Activation of anti-HBV immune activity by DNA vaccine via electroporation using heat shock proteins as adjuvant / 生物工程学报

Although DNA vaccination is now a promising strategy against hepatitis B virus (HBV) infection, this approach has relatively modest antiviral effect, indicating that immunosuppressive mechanisms may occur in the long-term established infection. In this study, we studied the immunogenicity and anti-HBV efficiency of a combination of HBV surface (HBsAg) and core (HBcAg) DNA vaccine, enhanced by heat shock protein (HSP) gp96 or HSP70 and mediated by in vivo electroporation. Immunization with gp96 adjuvanted HBsAg/HBcAg DNA formulation induced potent T cell and antibody immunity against HBsAg and HBcAg. Notably, treatment with gp96 or HSP70 as adjuvant resulted in reduction of Treg populations by around 20%. Moreover, compared with nonimmunized control mice, immunization with gp96 or HSP70 adjuvanted DNA vaccine dramatically decreased serum HBsAg and viral DNA levels, and HBcAg expression in liver. These results may therefore provide an effective strategy for designing gp96-based DNA vaccine for immunotherapy of chronic HBV infection.

MiR-122 in hepatic function and liver diseases

As the most abundant liver-specific microRNA, microRNA-122 (miR-122) is involved in various physiological processes in hepatic function as well as in liver pathology. There is now compelling evidence that miR-122, as a regulator of gene networks and pathways in hepatocytes, plays a central role in diverse aspects of hepatic function and in the progress of liver diseases. This liver-enriched transcription factors-regulated miRNA promotes differentiation of hepatocytes and regulates lipid metabolism. With regard to liver diseases, miR-122 was shown to stimulate hepatitis C virus (HCV) replication through a unique and unusual interaction with two binding sites in the 5'-UTR of HCV genome to mediate the stability of the viral RNA, whereas inhibit the expression and replication of hepatitis B virus (HBV) by a miR-122-cylin G1/p53-HBV enhancer regulatory pathway. In addition, miR-122 acts as a suppressor of cell proliferation and malignant transformation of hepatocytes with remarkable tumor inhibition activity. Notably, a clinical trial targeting miR-122 with the anti-miR-122 oligonucleotides miravirsen, the first miRNA targeted drug, has been initiated for treatment of HCV infection. With further understanding of the comprehensive roles of miR-122 in hepatic functions and the mechanisms involved in miR-122 down-regulation in chronic hepatitis or hepatocellular carcinoma, miR-122 appears to be a promising candidate for effective therapeutic approaches against tumor and infectious diseases.

Immune activity of heat shock protein gp96 and its application in active immunotherapy for tumor and infectious diseases / 生物工程学报

Heat-shock protein gp96 associates with antigenic peptides derived from tumor and virus. Exogenous gp96-peptide complexes are taken up by antigen-presenting cells through interaction with its receptor CD91 on the cell surface, and cross-present antigenic peptides to MHC class I molecules by a peptide relay line in the endoplasmic reticulum for specific T-cell activation. Meanwhile, gp96 has been shown to initiate innate immune responses through interaction with toll-like receptor 2 and toll-like receptor 4. Recent studies have shown a gp96-mediated immune balance between CTL and Tregs. With the further understanding of counteracting immunosuppressive mechanisms in gp96-induced cellular immune responses, and establishment of high level production of recombinant gp96 by the yeast, gp96 appears to be a promising candidate for designing effective therapeutic vaccines against tumor and infectious diseases.

Overview of Gp96 mediated immunity / 生物工程学报

As a member of the HSP90 family, heat shock protein (HSP) Gp96 is one of the most abundant proteins in the endoplasmic reticulum (ER), which displayed important molecular chaperones function in cells. Gp96 can stimulate the production of cytokines by activating the antigen presentation cells (such as dendritic cell, et al) in innate immunity. It is capable of eliciting an antigen-specific cytotoxic T lymphocyte (CTL) immune response to eliminate pathogens and tumors by facilitating antigen cross-presentation in adaptive immunity. Gp96 is also an ideal adjuvant in many recent researches. Here, we review the progress that addresses the role of biological characteristics, immunogenic mechanism that may be involved in the induction of anti-infection immune response and antitumor immunity, which may guide the new vaccine strategies with the knowledge of Gp96-antigen complexes.

Enhancement of cellular and humoral immune responses of HBV DNA vaccine by HSP70 and gp96 / 生物工程学报

While currently therapeutic vaccines for chronic hepatitis B virus (HBV) infection are actively being developed to complement standard antiviral treatments, their immune activity, especially T cell activity, remains to be further improved. Here, we investigated the role of heat shock proteins HSP70 and gp96 on cellular and humoral immunity, using the main structure antigens of hepatitis core (HBcAg) and surface (HBsAg) as the DNA vaccine. By ELISPOT (enzyme linked immunospot assay), IFN-gamma intracellular staining, [3H]-thymidine incorporation and ELISA (enzyme linked immunosorbent assay) analyses, we showed that immunization with HBsAg/HBcAg DNA formulation along with HSP70 or gp96 induced significant increase of T-cell (about 1-6-fold) and antibody (about 20%-60%) immunity against HBsAg and HBcAg. These results may provide bases for designing HSP70- and gp96-based vaccines aimed at eliciting T-cell responses for therapeutic applications.

Large-scale in vitro preparation of new gp96 tumor vaccine and analysis of its induction of specific anti-tumor immunoresponses / 生物工程学报

Heat shock protein gp96 isolated from tumor tissues holds great promise for tumor immunotherapy. However, at present only very limited amount of gp96 protein can be isolated from tumor tissues. Here, we reconstituted the yeast-expressed gp96 (recombinant gp96, rgp96) with B16.F10 melanoma antigens in vitro to prepare new gp96 tumor vaccine on large-scale, and analyzed its induction of specific anti-tumor immunoresponses by ELISPOT, IFN-gamma intracellular staining and cytotoxicity assays. Immunization with rgp96-tumor antigen complexes significantly inhibited B16 tumor growth compared with either rgp96 or tumor antigens alone and led to enhancement of tumor-specific T-cell activities, which was found similar to that of tumor tissue derived gp96. Our results therefore may provide bases for large-scale preparation of the new generation of gp96 tumor vaccines.