Use of a liposome antigen delivery system to alter immune responses in vivo

New and old adjuvants in allergen-specific immunotherapy: With a focus on nanoparticles

Allergic diseases have remarkably increased in recent years. Nowadays, efforts for curing and management of these disorders are an important concern worldwide. Allergen-specific immunotherapy (ASIT) has recently gained more attention as a means for the management of allergic diseases. Adjuvants or helper agents are materials applied for better stimulating and shifting of protective responses, and these belong to an extremely diverse collection of complexes. The main function of adjuvants includes acting as depot foundations, transferring vehicles, and immunostimulators. Immunostimulatory adjuvants have gained increasing attention for ASIT. In this regard, the present study provides a review of old and new adjuvants used in allergen immunotherapy.

Advances in effective vaccine development against hepatitis B: focus on mucosal vaccine delivery strategies

Hepatitis B virus causes chronic necroinflammatory liver disease, which is known as hepatitis B. This inflammatory condition may further aggravate liver cirrhosis or hepatocellular carcinoma. Currently available conventional hepatitis B vaccine contains one of the viral envelope proteins, hepatitis B surface antigen, which develops a humoral immune response and hence protects against the infection. However, it fails in developing the desired cellular immune response, which is one of the most important bioresponses contributing to virus elimination from infected hepatocytes. At the same time, moderate humoral response developed following conventional vaccination do not protect the mucosal surfaces through serosal response. The mucosa is a predominant entry site for most of the infectious pathogens. Several strategies, including the use of adjuvants, development of surface functionalized novel antigen carriers and mucosal immunization for example, have been explored to investigate their role in addressing the limitations associated with the current hepatitis B vaccine. This review focuses on recent advances that have been made in order to develop an effective vaccine against hepatitis B.

Cytotoxic T lymphocytes responding to low dose TRP2 antigen are induced against B16 melanoma by liposome-encapsulated TRP2 peptide and CpG DNA adjuvant

The induction of a potent and specific T cell response is a major challenge in the development of efficacious cancer vaccine strategies. We applied a novel liposomal formulation (AVE3) for efficient delivery of antigenic peptides into APCs of the skin. These liposomes resulted in a long-lasting deposition of encapsulated compounds at the injection site and the draining lymph nodes. Using a peptide from the melanocyte differentiation antigen tyrosinase-related protein (TRP2) 2 we could show that vaccination with liposome-encapsulated peptide in combination with oligodeoxynucleotides containing unmethylated CpG motifs (CpG ODNs) as adjuvant leads to the induction of tumor cell-specific cytotoxic T cells. The most potent immune response was observed when both, TRP2 peptide and CpG ODNs, were encapsulated into AVE3. Importantly, in contrast to vaccination with free TRP2 liposomal TRP2 peptide generated T cells which respond to 1000-fold lower antigen concentration. Using the poorly immunogenic B16 melanoma model we could demonstrate that vaccination with liposomal TRP2 peptide plus CpG ODNs but not vaccination with free peptide or adjuvant alone resulted in tumor protection in subcutaneous and metastatic tumor models. In summary, vaccination with liposome-encapsulated peptide antigen and CpG ODN allows for the in vivo loading and activation of DC, thereby generating reactive CTL populations even against poorly immunogenic self-peptide presenting tumors resulting in a potent anti-tumor immune response.

Anti-HBV effect of liposome-encapsulated matrine in vitro and in vivo

AIM

To study the anti-HBV effect of liposome-encapsulated matrine (Lip-M) in vitro and in vivo.

METHODS

2.2.15 cell line was cultured in vitro to observe the effect of Lip-M and matrine on the secretion of HBsAg and HBeAg. The toxicity of Lip-M and matrine to 2.2.15 cell line was also studied by MTT method. In in vivo study, drug treatment experiment was carried out on the 13th day after ducks were infected with duck hepatitis B virus (DHBV). The ducks were randomly divided into 4 groups with 5-6 ducks in each group. Lip-M and matrine were given to DHBV-infected ducks respectively by gastric perfusion. Four groups were observed: group of Lip-M (20 mg/kg), group of Lip-M (10 mg/kg), group of matrine (20 mg/kg) and group of blank model. The drug was given once daily for 20 d continuously, and normal saline was used as control. The blood was drawn from the posterior tibial vein of all ducks before treatment (T(0)), after the medication for 5 (T5), 10 (T10), 15 (T15), 20 (T20) d and withdrawl of the drug for 3 d (P3). The serum samples were separated and stored at -70 degrees, DHBV-DNA was detected by the dot-blot hybridization.

RESULTS

After addition of Lip-M and matrine to 2.2.15 cell line for eleven d, the median toxic concentration (TC50) of Lip-M and matrine was 7.29 mg/mL and 1.33 mg/mL respectively. The median concentration (IC50) of Lip-M to inhibit HBsAg and HBeAg expression was 0.078 mg/mL and 3.35 mg/mL respectively. The treatment index (TI) value of Lip-M for HBsAg and HBeAg was 93.46 and 2.17 respectively, better than that of matrine. The DHBV-infected duck model treatment test showed that the duck serum DHBV-DNA levels were markedly reduced in the group of Lip-M (20 mg/kg) after treated by gastric perfusion for 10, 15 and 20 d (0.43+/-0.22 vs 0.95+/-0.18, t = 4.70, P = 0.001<0.01.0.40+/-0.12 vs 0.95+/-0.18, t = 6.34, P = 0.000<0.01. 0.22+/-0.10 vs 0.95+/-0.18, t = 8.30, P = 0.000<0.01), compared to the group of matrine (20 mg/kg) (0.43+/-0.22 vs 0.79+/-0.19, t = 3.17, P = 0.01<0.05. 0.40+/-0.12 vs 0.73+/-0.24, t = 3.21, P = 0.009<0.05. 0.22+/-0.10 vs 0.55+/-0.32, t = 2.27, P = 0.046<0.05.), and the control(0.43+/-0.22 vs 0.98+/-0.29, t = 3.68, P = 0.005<0.01. 0.40+/-0.12 vs 0.97+/-0.30, t = 4.26, P = 0.002<0.01. 0.22+/-0.10 vs 0.95+/-0.27, t = 5.76, P = 0.000<0.01). After the treatment for 20 d and withdrawl of the drug for 3 d, duck serum DHBV-DNA level in the group of Lip-M (10 mg/kg) markedly reduced (0.56+/-0.26 vs 0.95+/-0.38, t = 5.26, P = 0.003<0.05. 0.55+/-0.25 vs 0.95+/-0.38, t = 5.52, P = 0.003<0.05), and the difference was significant as compared with the control (0.56+/-0.26 vs 0.95+/-0.27, t = 2.37, P = 0.042<0.05. 0.55+/-0.25 vs 0.89+/-0.18, t = 2.55, P = 0.031<0.05), but not significant as compared with the group of matrine (20 mg/kg). After withdrawl of the drug for 3 d, the levels of DHBV-DNA did not relapse in both groups of Lip-M.

CONCLUSION

Lip-M can evidently inhibit the replication of hepatitis B virus in vitro and in vivo; its anti-HBV effect is better than that of matrine.

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Recent advances in the development of peptide vaccines for hepatitis B

The control of hepatitis B by vaccination is arguably one of medicine's greatest achievements in terms of protecting infants and adults at high risk of infection. Paradoxically, however, the existence of a large reservoir of chronically infected individuals will not diminish the risk of infection by those coming into close contact with such persons until universal infant immunisation is practised globally and vaccines are in place to ensure maximum efficacy in those with impaired immune responses, immunity is achieved with fewer doses, and immunisation as an adjunct to the antiviral treatment of chronic carriers is adopted. These imperatives have continued to stimulate research into vaccines based on chemically synthesised short peptides, and those systems best suited for their delivery. This review discusses the potential of synthetic peptide formulations as efficient inducers of both humoral and cellular immune responses against hepatitis B, and reviews recent advances in peptide delivery. Synthetic peptide and delivery systems technologies will, amongst others, be of paramount importance in the global fight for the eradication of hepatitis B in the 21st century.

Altered immune response to liposomal allergens of Aspergillus fumigatus in mice

Aspergillus fumigatus has been implicated as the major pathogenic fungus causing Aspergillus-mediated disorders. It secretes complex glycoprotein antigens and allergens, which induce type I and type III mediated hypersensitivity reactions. The immune response to these allergens/antigens in allergic disorders is characterized by elevated levels of specific IgE, Th2 cytokines and eosinophilia. In the current study, the ability of negatively charged liposomes entrapped with glycoprotein antigens and allergens of A. fumigatus to modulate the immune response was studied. Immune response in mice was evaluated with both free and liposomal formulations. Liposome entrapped glycoprotein antigens/allergens of A. fumigatus elicited a Th1 type response with increased levels of TNF-alpha (5.5-folds), IFN-gamma (four-folds), specific IgG (three-folds) and IgG2a (2.4-folds), low titers of specific IgG1 (2.2-folds decrease) and IgE (three-folds decrease), and decreased peripheral eosinophilia by four-folds in comparison to mice receiving free glycoprotein allergens/antigens of A. fumigatus. Histopathological examination of lung tissue sections clearly indicated reduced eosinophil infiltration in mice immunized with liposomal formulations. These results suggest potential of liposomal formulations for A. fumigatus allergens/antigens for exploration in immunotherapy.

Effect of liposomal antigens on the priming and activation of the immune system by dendritic cells

Dendritic cells (DCs) are recognized as the sole professional antigen-presenting cells capable of priming naive T cells of the helper and cytotoxic phenotypes. This property is presently exploited with success in vaccinal strategies against pathogens or tumor cells that otherwise escape immune recognition, but the repeated infusions of ex vivo expanded and sensitized DCs are usually required to achieve protection. In this paper, we demonstrate that liposomal antigens can efficiently relay and propagate the action of DCs, inducing a strong long-term response against their associated antigen. Their effect is mainly achieved by improving the ex vivo loading of DCs and by efficiently channeling the activation stimulus into the induction of effector function. This is demonstrated by the sustained immunoglobulin production as well as by the sustained lymphoproliferation and the increased cytokine secretion that can be achieved upon restimulation of DC-primed immune cells with limited amount of liposomal antigenic material. Being well-tolerated and easily prepared, liposomal antigens could therefore be expected to significantly contribute to the efficiency and to a more general utilization of the highly promising but rather cumbersome DC-based immunotherapies.

Targeting early events in T cell activation to construct improved vaccines

Live, attenuated vaccines currently offer the best protection against virulent pathogens. Recent advances in Immunology and Molecular Biology provide an opportunity to design vaccines that will be more effective and safer than existing ones. Immunologists are rapidly developing the capacity to identify and construct the minimal immunogenic units from pathogens. The molecular signals required to fully activate antigen presenting cells (APCs) and responder T cells are becoming apparent. Improved vaccine delivery systems are being designed which will mimic the actions of pathogens in vivo. These vaccines will incorporate protective epitopes fused to immunoregulatory cytokines in chimeric proteins. They will be encapsulated in formulations which allow for the slow release of these chimeric proteins thereby inducing the memory T cells required for long-lived immunity. These vaccine formulations will target receptors present on the most active APCs. Here we discuss how these advances will allow us to rationally construct "virtual pathogens" which will provide improved protection against new and old microbial foes.