Adjuvant screen identifies DC modifying growth factor Flt3 ligand as candidate for prostate cancer DNA vaccine
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Abstract:
Abstract Prostate cancer is the most common type of cancer in men. Immunotherapies such as Sipuleucel-T have shown that stimulating the immune system to target the prostate is a viable therapeutic option. Inovio is a clinical-stage biotechnology company that uses DNA vaccines as a novel immunotherapy strategy. An advantage to plasmid DNA vaccine therapy is the ability to encode adjuvants within the vaccine in order to increase immunogenicity and efficacy. We conducted an adjuvant screen in BALB/c mice with 25 candidate plasmid encoded genetic adjuvants in combination with the prostate cancer specific tumor-associated antigen STEAP1. Antigen-specific T cell responses were measured by IFNg ELISpot. The screen revealed that the addition of a plasmid encoding dendritic cell (DC)-activating Fms-like tyrosine kinase 3 ligand (Flt3L) fused to an Fc domain, significantly increased antigen-specific T cells (p<0.001, 2.8 fold). Mice treated with Flt3L-Fc had an enhanced immune response to STEAP1 vaccination as early as 7 days post dose 1 (p<0.01, 2.4 fold), which developed into an enhanced memory response measured 12 weeks later (p<0.001, 8.5 fold). Flow cytometry showed that Flt3L-Fc increased DC populations at the site of injection and at the draining lymph node 8 days following the initial vaccination. DCs are considered the most potent antigen-presenting cells in the immune system and DCs at the tumor site have been shown to be critical for T cell immunity. Our data shows that enhancing DC populations and function through the use of a genetic adjuvant can enhance the immunogenicity of a DNA cancer vaccine. Future studies will assess the efficacy of Flt3L-Fc in combination with STEAP1 in a mouse tumor model.Keywords:
ELISPOT
Cancer vaccine
Modern vaccines, based on antigen subunits are devoid of many side-effects, but often lack immunogenicity. The addition of adjuvants to vaccine formulas can overcome this problem. As a very heterogeneous group of substances, adjuvants enhance immune response to weak antigens in different ways. They protect against the rapid degradation of immunogen in the organism after inoculation. They can form a reservoir of antigens (the depot effect), increasing the vaccine's persistence at the injection site and the draining lymph nodes. Adjuvants also nonspecifically activate immune cells,including antigen-presenting cells and lymphocytes. In such a case, the elevated immunogenicity of the antigen results from a bystander effect: by choosing an appropriate adjuvant or a mixture of them, one can direct the type of immune response, toward the generation of cell-mediated immunity (Th1) or the stimulation of the production of specific antibodies (Th2). Recognition of the exact mechanisms of antigen processing and cell interactions will allow constructing more effective vaccines.
Immunogen
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Immunostimulant
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Toxoplasmosis
Immunopotentiator
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Alum
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ELISPOT
Simian immunodeficiency virus
HIV vaccine
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Objective:In this research,we select HIV-1 replicating DNA vaccine and recombinant non-replicating Tiantan Vaccinia Virus(rNTV-C) vaccine to evaluate their immunogenicity in mice.The two vaccines respectively express six genes including gp160,gag-pol and rev-tat-nef of HIV-1 clade B'/C.Methods:BALB/c mice were injected with HIV-1 DNA vaccine and rNTV-C alone or combined.The different injection dose and different injection pathway of the vaccine were designed.Cellular immune responses were detected with IFN-γ ELISPOT.Results:HIV-1 DNA vaccine and rNTV-C separated immunization could induce special cellular immune responses of antigens of HIV-1.The combined immunization of DNA priming and rNTV-C boost could elicit much higher cellular immune response than DNA or rNTV-C alone immunization.The statistical analysis results showed that the immune response of intramuscular(im) injection of HIV-1 DNA vaccine and rNTV-C was higher than intradermal(id) injection.The immune response of 1 μg dose of DNA vaccine was similar with 5 μg dose and the immune response of 1×108 PFU dose of rNTV-C was higher than 2×107 PFU dose.Conclusion:HIV-1 DNA vaccine and rNTV-C alone or combined immunization can induce special cellular immune response.The research data also provided important evidence for institution of clinical immune plan.
ELISPOT
Modified vaccinia Ankara
HIV vaccine
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For the development of veterinary subunit vaccines, modifications to the antigen may be needed to make the production of these vaccines cost effective. To investigate the effect of antigen modifications on immune response, we used glycoprotein D, one of the major glycoproteins of bovine herpesvirus-1 (BHV-1), as a model antigen. We developed a mouse model to assess the immune response elicited by immunization with either a recombinant truncated (tgD) or the authentic full-length (gD) form of BHV-1 gD in VSA3, a novel water-in-oil adjuvant. Both forms of BHV-1 gD antigen induced good levels of cell-mediated immunity, as evaluated by antigen-specific proliferative response and cytokine (IFN-γ and IL-4) production. Following primary immunization, the humoral immune response induced by gD was superior to that elicited by vaccination with tgD. However, after a secondary immunization, a strong and similar antibody response to BHV-1 gD was induced by both forms of the antigen. The difference in immunogenicity between gD and tgD after primary immunization was not due to the loss of immunogenic epitopes in the truncated antigen or the ability to associate with the adjuvant VSA3. Our results indicate that both gD and tgD are capable of efficiently inducing a cell-mediated immune response, and although recombinant tgD is less efficient in inducing a primary humoral immune response when compared to the full-length gD, tgD effectively primed for a secondary antibody response.
Humoral immunity
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Statement: The formulation of effective vaccines
generally requires adjuvants to stimulate an appropriate
immune response. Adjuvants are usually defined
as compounds that can increase or modulate
the immunogenicity of an antigen. According to the
literature, saponins are shown to possess several
physiological properties, mainly the capacity for
alteration of membrane permeability. These compounds
have been reported to possess therapeutic
potential for immune system modulation. Because
the observation that certain saponins cause substantial
enhancement of immune responses when
given together with an antigen in a vaccine, their
use as adjuvants received special attention. The
present study is concerned with the investigation
of molecular characteristics and structural aspects
of an antigen-adjuvant complex originated from an
experimental vaccine formulation. Methodology: A
commercial extract of Quillaja saponaria was fractionated
by chromatographic techniques to afford
a purified saponin (QS-21), which was identified by
Nuclear Magnetic Resonance spectroscopy. The adjuvant
potential of QS-21 on the cellular immuneresponse against ovalbumin antigen was evaluated.
The delayed type hypersensitivity reaction was used
as an in vivo assay of cellular immune response. The
capacity of the antigen-adjuvant complex to interact
with biomembranes was evaluated using in vitro assays.
Findings: When the immunization occurs only
with the antigen or the adjuvant without conjugation,
the cellular immune response was practically
abolished, since these compounds were not capable
to induce an effective immune response when administered
alone, which implies the necessity of conjugation
to elicit an immunological reaction, which
was significantly effective for the antigen-adjuvant
complex. Additionally, the complex showed a potent
capacity to interact with biomembranes, forming
structurally diverse aggregates. Conclusion: A remarkable
property of the antigen-adjuvant complex
to stimulate the immune response was demonstrated.
This activity can be attributed to its capacity to
form aggregates with biomembranes, identified as
the immunostimulating complexes, responsible for the enhanced immunogenicity
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Two series of experiments are described in which elimination of [131I]BGG is observed in CBA mice treated with mycobacterial adjuvants. Neither mycobacteria in oil nor Wax D in oil induced immune-type elimination in the first series where control mice catabolized the antigen relatively slowly (mean half-lives of 4.38 and 5.0 days). In a second series where control mice showed faster catabolism (mean half-lives 3.82 and 2.96 days) the adjuvants did induce immune elimination. It was found also that such adjuvants invariably accelerated the elimination rate in the pre-immune period of elimination.
Porton White mice eliminated the antigen rapidly and even mice not given adjuvant frequently gave a secondary immune response on a further exposure to antigen.
The results suggest that increases in the rate of antigen catabolism contribute to adjuvant activity in this model.
Catabolism
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The use of specific combinations of antigens and adjuvant represents a promising approach for increasing the immunogenicity of DNA vaccines. In the present study, we evaluated the immunity and antitumor effects of DNA vaccines with G250 as the target antigen in a mouse model of renal cell carcinoma. We constructed two recombinant plasmids, pVAX1-G250 and pVAX1-CD40L. The recombinant plasmids were injected into mice by intramuscular injection and electrical pulse stimulation. ELISA and ELISPOT experiments were performed to evaluate the corresponding humoral and cellular immune responses following immunization. To further investigate the antitumor potential of the DNA vaccines, we established a tumor-bearing mouse model expressing G250 target antigen. Our results showed that immunization with the combination of the two plasmids exerted the strongest anti-tumor effects. Therefore, our findings demonstrated the effectiveness of CD40L as an adjuvant for DNA vaccines and highlighted the promising use of these vaccines for the treatment of tumors.
ELISPOT
Immunoadjuvant
Cancer vaccine
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