Enhancement of cytotoxic T lymphocyte activity by dendritic cells loaded with Tat-protein transduction domain-fused hepatitis B virus core antigen

Potential of cell-penetrating peptides (CPPs) in delivery of antiviral therapeutics and vaccines

Viral infections are a great threat to human health. Currently, there are no effective vaccines and antiviral drugs against the majority of viral diseases, suggesting the need to develop novel and effective antiviral agents. Since the intracellular delivery of antiviral agents, particularly the impermeable molecules, such as peptides, proteins, and nucleic acids, are essential to exert their therapeutic effects, using a delivery system is highly required. Among various delivery systems, cell-penetrating peptides (CPPs), a group of short peptides with the unique ability of crossing cell membrane, offer great potential for the intracellular delivery of various biologically active cargoes. The results of numerous in vitro and in vivo studies with CPP conjugates demonstrate their promise as therapeutic agents in various medical fields including antiviral therapy. The CPP-mediated delivery of various antiviral agents including peptides, proteins, nucleic acids, and nanocarriers have been associated with therapeutic efficacy both in vitro and in vivo. This review describes various aspects of viruses including their biology, pathogenesis, and therapy and briefly discusses the concept of CPP and its potential in drug delivery. Particularly, it will highlight a variety of CPP applications in the management of viral infections.

Enhanced anti-tuberculosis immunity by a TAT-Ag85B protein vaccine in a murine tuberculosis model

BACKGROUND

The development of more effective anti-tuberculosis vaccines would contribute to the control of the global problem of infection with Mycobacterium tuberculosis (MTB). Recently, increasing evidences showed that HIV-Tat protein transduction domain is implicated in promotion of vaccines by inducing cellular immuno-response. However, it is rare known about the role of TAT in vaccines against MTB.

METHODS

In this study, we expressed recombinant protein-fused Ag85B with TAT (TAT-Ag85B) which was used as a vaccine to inoculate mice infected with MTB.

RESULTS

As s result, both IgG2a in serum and IFN-γ or TNFα produced by spleen cells were all increased significantly in the mice inoculated by TAT-Ag85B. Furthermore, consistently, TAT-Ag85B inoculation significantly reduced MTB loads both in lung and spleen.

CONCLUSIONS

These findings demonstrate that a novel protein vaccine of TAT-Ag85B enhances immune response both in humoral and cellular immunity, and contributes to protective efficacy against MTB.

Soluble CD40 ligand-activated B cells from patients with chronic hepatitis B virus infection as antigen presenting cells to induce hepatitis B virus specific cytotoxic T lymphocytes

Chronic hepatitis B virus (HBV) infection is the result of an inadequate antiviral immune response to the virus. In this study, we aimed to investigate whether the soluble CD40 ligand-activated B (CD40-B) cells could present antigen and induce specific cytotoxic T lymphocytes (CTLs) in patients with chronic HBV infection. We observed that after activated by sCD40L, the expression of CD80, CD86, major histocompatibility complex (MHC) I and II molecules on the CD40-B cells was significantly increased. Cytometry and fluorescence microscopy showed that more than 41.34% CD40-B cells were loaded by the HBcAg peptide. Furthermore, after been activated and HBcAg18-27 antigen peptide pulsed, B cells obtained from patients with chronic HBV infection could induce HBcAg18-27 specific CTLs in vitro. Taken together, our results show that B cells from patients with chronic HBV infection can be activated by sCD40L and may function as antigen presenting cells and induce HBV-specific CTLs.

Recombinant mammaglobin A adenovirus-infected dendritic cells induce mammaglobin A-specific CD8+ cytotoxic T lymphocytes against breast cancer cells in vitro

Mammaglobin A (MGBA) is a novel breast cancer-associated antigen almost exclusively over-expressed in primary and metastatic human breast cancers, making it a potential therapeutic target for breast cancer. The development of dendritic cell (DC)-induced tumor antigen specific CD8⁺ cytotoxic T lymphocytes (CTLs) may hold promise in cancer immunotherapy. In this study we constructed recombinant replication-defective adenoviral (Ad) vectors encoding MGBA and evaluated their ability to trigger anti-tumor immunity in vitro. DCs were isolated from the human peripheral blood monocyte cells (PBMCs) of two HLA-A33⁺ healthy female volunteers, and infected with adenovirus carrying MGBA cDNA (Ad-MGBA). After that, the Ad-MGBA-infected DCs were used to stimulate CD8⁺ CTLs in vitro and the latter was used for co-culture with breast cancer cell lines. The data revealed that infection with Ad-MGBA improved DC maturation and up-regulated the expression of co-stimulatory molecules and the secretion of interleukin-12 (IL-12), but down-regulated interleukin-10 (IL-10) secretion from DCs. Ad-MGBA-infected DC-stimulated CD8⁺CTLs displayed the highest cytotoxicity towards HLA-A33⁺/MGBA⁺ breast cancer MDA-MB-415 cells compared with other CD8⁺CTL populations, and compared with the cytotoxicity towards HLA-A33⁻/MGBA⁺ breast cancer HBL-100 cells and HLA-A33⁻/MGBA⁻ breast cancer MDA-MB 231 cells. In addition, Ad-MGBA-infected DC-stimulated CD8⁺ CTLs showed a high level of IFNγ secretion when stimulated with HLA-A33⁺/MGBA⁺ breast cancer MDA-MB-415 cells, but not when stimulated with HLA-A33⁻/MGBA⁺ HBL-100 and HLA-A33⁻/MGBA⁻MDA-MB-231 cells. In addition, killing of CD8⁺CTLs against breast cancer was in a major histocompability complex (MHC)-limited pattern. Finally, the data also determined the importance of TNF-α in activating DCs and T cells. These data together suggest that MGBA recombinant adenovirus-infected DCs could induce specific anti-tumor immunity against MGBA⁺ breast cancers, which could provide a novel strategy in the immunotherapy of breast cancer.

Ubiquitin conjugation of hepatitis B virus core antigen DNA vaccine leads to enhanced cell-mediated immune response in BALB/c mice

BACKGROUND

Nearly 350 million persons worldwide are chronically infected with hepatitis B virus (HBV). Ubiquitin (Ub) is a highly conserved small regulatory protein, ubiquitous in eukaryotes, that usually serves as a signal for the target protein that is recognised and degraded in proteasomes . The Ub-mediated processing of antigens is rapid and efficient and stimulates cell-mediated immune responses. Accordingly, Ub-mediated processing of antigens has been widely used in chronic-infection and cancer studies to improve immune response.

OBJECTIVES

Many clinical trials have shown that DNA vaccine potency needs to be greatly enhanced. Here, we report a new strategy for designing an HBV DNA vaccine using the ubiquitin (Ub) sequence. The aim of this study was to investigate a novel DNA vaccination, based on the expression of HBV core antigen (HBcAg), fused to Ub to enhance DNA vaccine potency.

MATERIALS AND METHODS

Mouse ubiquitin fused to the HBcAg gene and cloned into the eukaryotic vector pcDNA3.1 (-). BALB/c mice were immunized with recombinant pUb-HBcAg or pHBcAg DNA vaccine. Lymphocyte proliferation assay, intracellular IFN-γ assay, CTL cytotoxicity assay, and antibody assay were performed to analyze the cellular and humoral immune responses to our DNA constructs.

RESULTS

HBcAg was expressed effectively in the COS-7 cells that were transiently transfected with pUb-HBcAg. Strong anti-HBc IgG responses were elicited in mice that were immunized with pUb-HBcAg. The endpoint titers of anti-HBc peaked at 1:656100 on the 42nd day after the third immunization. pUb-HBcAg stimulated greater lymphocyte proliferation and induced higher levels of IL-2 and IFN-γ and a greater percentage of HBcAg-specific CD8+ T cells in mice than pHBcAg. In the CTL assay, the specific lysis rate reached 56.5% at an effector:target ratio of 50:1 in mice that were immunized with pUb-HBcAg.

CONCLUSIONS

pUb-HBcAg elicits specific anti-HBc responses and induces HBc-specific CTL responses in immunized BALB/c mice. Our results imply that Ub can be used as a molecular adjuvant that enhances the potency of DNA vaccines.

The delivery of HBcAg via Tat-PTD enhances specific immune response and inhibits Hepatitis B virus replication in transgenic mice

Recent studies have indicated that the therapeutic vaccine based on enhancement of HBV-specific cytotoxic T-lymphocyte (CTL) activity may lead to viral clearance in chronically infected individuals. It is demonstrated that protein transduction domains (PTD) from HIV-1-Tat protein is able to enter cells when combined with exogenous antigens and induce specific CTL responses. We have previously testified that the expressed and purified fusion protein containing Tat-PTD47-57 and HBcAg could enter cytoplasm of dendritic cells, and enhance T cells response to generate HBcAg-specific CTLs efficiently in vitro. In the present study, we evaluated HBcAg-specific immune responses of PTD-HBcAg fusion protein in BALB/c mice and antiviral immunity in HBV transgenic mice. The studies showed that PTD-HBcAg not only induced significantly higher antibody responses, but also increased production of cytokine (IFN-gamma, IL-2, IL-4 and IL-10) compared to HBcAg alone and PBS. Moreover, PTD-HBcAg fusion protein increased significantly the percentages of IFN-gamma+CD8+ T cells and HBcAg-specific (CTL) responses. Also, enhancement of immune response induced by fusion protein reduced HBV DNA and HBsAg levels and decreased the expression of HBsAg in liver tissue of HBV transgenic mice. In conclusion, PTD-HBcAg fusion protein could enhance not only cell immune response but also humoral immune response, and induce robust specific CTL activity and therapeutic effects in HBV transgenic mice.

Protein transduction domain-hepatitis B virus core antigen fusion protein-induced specific cytotoxic T lymphocyte response inhibits hepatitis B virus replication in hepatitis B virus-transgenic mice

AIM: To investigate the effect of protein transduction domain-hepatitis B virus core antigen (PTD-HBcAg) fusion protein-induced specific cytotoxic T lymphocyte (CTL) response on hepatitis B virus (HBV) replication in HBV-transgenic mice.

METHODS: Twenty HBV-transgenic mice were randomly divided into two groups: mice subcutaneously immunized with PTD-HBcAg fusion protein (PTD-HbcAg group) and those immunized with HBcAg (HBcAg group). The immunizations were given once a week for three weeks. Cytokine expression in splenocytes was analyzed by flow cytometry. Serum HBsAg and HBV DNA levels were determined by microparticle enzyme immunoassay and real-time fluorescent PCR assay, respectively. The expression of HBsAg in hepatic tissue was detected by immunohistochemistry.

RESULTS: Following immunization with PTD-HBcAg fusion protein, the proportions of CTLs in the spleen and inflammatory cells in hepatic tissue of HBV transgenic mice were upregulated remarkably. Serum HBsAg and HBV DNA levels in the PTD-HbcAg group were significantly lower than those in the HBcAg group. The mean absorbance values of HBsAg staining in hepatic tissue in the PTD-HBcAg group (50 µg: 127.77 ± 4.92; 100 µg: 117.71 ± 5.18) were significantly lower than those in the blank control group (156.84 ± 4.94) and HBcAg group (50 µg: 138.70 ± 5.92)(all P < 0.05).

CONCLUSION: Immunization with PTD-HBcAg fusion protein significantly increases the number of specific CTLs in the spleen, decreases serum HBsAg and HBV DNA levels, and downregulates HbsAg expression in hepatic tissue in HBV-transgenic mice, suggesting that PTD-HBcAg fusion protein has anti-HBV activity.