T cell-specific immune response induced by bacterial ghosts

BACKGROUND: Bacterial ghosts, genetically inactivated Gram-negative bacterial pathogens, possess significant advantages over commonly used vaccination technologies. The autolysis of the bacteria, by the expression of a cloned viral gene, results in empty bacterial envelopes through the expulsion of cytoplasmic content. Immunostimulatory properties are generally presented through the targeting of professional antigen-presenting cells (APCs), such as macrophages and dendritic cells (DCs). MATERIAL/METHODS: This study investigated the interactions between porcine antigen-presenting cells and bacterial ghosts derived from the bacterial pathogen Actinobacillus pleuropneumoniae. The maturation process of DCs and their generation of immune responses to bacterial ghosts was shown by the expression of activation markers on their surface, as well as in the functional tests. RESULTS: A population of porcine APCs was generated from PBS by incubation with rpo-GMCSF and rh-IL-4. The cells expressed SWC3, MIL-2, CD80/86 molecules, as well as a high level of MSA3 molecules. The internalization of bacterial ghosts by the cells resulted in increased expression of MSA3 molecules. The capacity of T cells to proliferate when induced by bacterial ghosts was 4 times higher in the cultures including APCs than in cultures stimulated with bacterial ghosts only. CONCLUSIONS: We found that antigen-presenting cells have the capacity to stimulate specific T cells after the internalization and processing of Actinobacillus ghosts, as demonstrated by a strong specific T-cell response generated against the ghost antigens

Prevention and Therapy of Hepatocellular Carcinoma by Vaccination with TM4SF5 Epitope-CpG-DNA-Liposome Complex without Carriers

Although peptide vaccines have been actively studied in various animal models, their efficacy in treatment is limited. To improve the efficacy of peptide vaccines, we previously formulated an efficacious peptide vaccine without carriers using the natural phosphodiester bond CpG-DNA and a special liposome complex (Lipoplex(O)). Here, we show that immunization of mice with a complex consisting of peptide and Lipoplex(O) without carriers significantly induces peptide-specific IgG2a production in a CD4+ cells- and Th1 differentiation-dependent manner. The transmembrane 4 superfamily member 5 protein (TM4SF5) has gained attention as a target for hepatocellular carcinoma (HCC) therapy because it induces uncontrolled growth of human HCC cells via the loss of contact inhibition. Monoclonal antibodies specific to an epitope of human TM4SF5 (hTM4SF5R2-3) can recognize native mouse TM4SF5 and induce functional effects on mouse cancer cells. Pre-immunization with a complex of the hTM4SF5R2-3 epitope and Lipoplex(O) had prophylactic effects against tumor formation by HCC cells implanted in an mouse tumor model. Furthermore, therapeutic effects were revealed regarding the growth of HCC when the vaccine was injected into mice after tumor formation. These results suggest that our improved peptide vaccine technology provides a novel prophylaxis measure as well as therapy for HCC patients with TM4SF5-positive tumors

Delivery of foreign antigens by engineered outer membrane vesicle vaccines

As new disease threats arise and existing pathogens grow resistant to conventional interventions, attention increasingly focuses on the development of vaccines to induce protective immune responses. Given their admirable safety records, protein subunit vaccines are attractive for widespread immunization, but their disadvantages include poor immunogenicity and expensive manufacture. We show here that engineered Escherichia coli outer membrane vesicles (OMVs) are an easily purified vaccine-delivery system capable of greatly enhancing the immunogenicity of a low-immunogenicity protein antigen without added adjuvants. Using green-fluorescent protein (GFP) as the model subunit antigen, genetic fusion of GFP with the bacterial hemolysin ClyA resulted in a chimeric protein that elicited strong anti-GFP antibody titers in immunized mice, whereas immunization with GFP alone did not elicit such titers. Harnessing the specific secretion of ClyA to OMVs, the ClyA-GFP fusion was found localized in OMVs, resulting in engineered recombinant OMVs. The anti-GFP humoral response in mice immunized with the engineered OMV formulations was indistinguishable from the response to the purified ClyA-GFP fusion protein alone and equal to purified proteins absorbed to aluminum hydroxide, a standard adjuvant. In a major improvement over current practice, engineered OMVs containing ClyA-GFP were easily isolated by ultracentrifugation, effectively eliminating the need for laborious antigen purification from cell-culture expression systems. With the diverse collection of heterologous proteins that can be functionally localized with OMVs when fused with ClyA, this work signals the possibility of OMVs as a robust and tunable technology platform for a new generation of prophylactic and therapeutic vaccines