Intramuscular immunization with a monogenic plasmid DNA tuberculosis vaccine: Enhanced immunogenicity by electroporation and co-expression of GM-CSF transgene

Promising Cytokine Adjuvants for Enhancing Tuberculosis Vaccine Immunity

Tuberculosis, caused by Mycobacterium tuberculosis (M. tuberculosis), remains a formidable global health challenge, affecting a substantial portion of the world's population. The current tuberculosis vaccine, bacille Calmette-Guérin (BCG), offers limited protection against pulmonary tuberculosis in adults, underscoring the critical need for innovative vaccination strategies. Cytokines are pivotal in modulating immune responses and have been explored as potential adjuvants to enhance vaccine efficacy. The strategic inclusion of cytokines as adjuvants in tuberculosis vaccines holds significant promise for augmenting vaccine-induced immune responses and strengthening protection against M. tuberculosis. This review delves into promising cytokines, such as Type I interferons (IFNs), Type II IFN, interleukins such as IL-2, IL-7, IL-15, IL-12, and IL-21, alongside the use of a granulocyte-macrophage colony-stimulating factor (GM-CSF) as an adjuvant, which has shown effectiveness in boosting immune responses and enhancing vaccine efficacy in tuberculosis models.

pGM-CSF as an adjuvant in DNA vaccination against SARS-CoV-2

The emergence of SARS-CoV-2 presents a significant global public health dilemma. Vaccination has long been recognized as the most effective means of preventing the spread of infectious diseases. DNA vaccines have attracted attention due to their safety profile, cost-effectiveness, and ease of production. This study aims to assess the efficacy of plasmid-encoding GM-CSF (pGM-CSF) as an adjuvant to augment the specific humoral and cellular immune response elicited by DNA vaccines based on the receptor-binding domain (RBD) antigen. Compared to the use of plasmid-encoded RBD (pRBD) alone, mice that were immunized with a combination of pRBD and pGM-CSF exhibited significantly elevated levels of RBD-specific antibody titers in serum, BALF, and nasal wash. Furthermore, these mice generated more potent neutralization antibodies against both the wild-type and Omicron pseudovirus, as well as the ancestral virus. In addition, pGM-CSF enhanced pRBD-induced CD4+ and CD8+ T cell responses and promoted central memory T cells storage in the spleen. At the same time, tissue-resident memory T (Trm) cells in the lung also increased significantly, and higher levels of specific responses were maintained 60 days post the final immunization. pGM-CSF may play an adjuvant role by promoting antigen expression, immune cells recruitment and GC B cell responses. In conclusion, pGM-CSF may be an effective adjuvant candidate for the DNA vaccines against SARS-CoV-2.

Nanomaterials in tuberculosis DNA vaccine delivery: historical perspective and current landscape

Vaccinations, especially DNA vaccines that promote host immunity, are the most effective interventions for tuberculosis (TB) control. However, the vaccine delivery system exhibits a significant impact on the protective effects of the vaccine. Recently, effective nanomaterial-based delivery systems (including nanoparticles, nanogold, nanoliposomes, virus-like particles, and virus carriers) have been developed for DNA vaccines to control TB. This review highlights the historical development of various nanomaterial-based delivery systems for TB DNA vaccines, along with the emerging technologies. Nanomaterial-based vaccine delivery systems could enhance the efficacy of TB vaccination; therefore, this summary could guide nanomaterial selection for optimal and safe vaccine delivery, facilitating the design and development of highly effective TB vaccines.

Immunotherapeutic Effects of Different Doses of Mycobacterium tuberculosis ag85a/b DNA Vaccine Delivered by Electroporation

Background

Tuberculosis (TB) is a major global public health problem. New treatment methods on TB are urgently demanded.

Methods

Ninety-six female BALB/c mice were challenged with 2×10⁴ colony-forming units (CFUs) of MTB H₃₇Rv through tail vein injection, then was treated with 10μg, 50μg, 100μg, and 200μg of Mycobacterium tuberculosis (MTB) ag85a/b chimeric DNA vaccine delivered by intramuscular injection (IM) and electroporation (EP), respectively. The immunotherapeutic effects were evaluated immunologically, bacteriologically, and pathologically.

Results

Compared with the phosphate-buffered saline (PBS) group, the CD4⁺IFN-γ⁺ T cells% in whole blood from 200 µg DNA IM group and four DNA EP groups increased significantly (P<0.05), CD8⁺IFN-γ⁺ T cells% (in 200 μg DNA EP group), CD4⁺IL-4⁺ T cells% (50 μg DNA IM group) and CD8⁺IL-4⁺ T cells% (50 μg and 100 μg DNA IM group, 100 μg and 200 μg DNA EP group) increased significantly only in a few DNA groups (P< 0.05). The CD4⁺CD25⁺ Treg cells% decreased significantly in all DNA vaccine groups (P<0.01). Except for the 10 μg DNA IM group, the lung and spleen colony-forming units (CFUs) of the other seven DNA immunization groups decreased significantly (P<0.001, P<0.01), especially the 100 μg DNA IM group and 50 μg DNA EP group significantly reduced the pulmonary bacterial loads and lung lesions than the other DNA groups.

Conclusions

An MTB ag85a/b chimeric DNA vaccine could induce Th1-type cellular immune reactions. DNA immunization by EP could improve the immunogenicity of the low-dose DNA vaccine, reduce DNA dose, and produce good immunotherapeutic effects on the mouse TB model, to provide the basis for the future human clinical trial of MTB ag85a/b chimeric DNA vaccine.

Recent progress in the design of DNA vaccines against tuberculosis

Current tuberculosis (TB) vaccines have some disadvantages and many efforts have been undertaken to produce effective TB vaccines. As a result of their advantages, DNA vaccines are promising future vaccine candidates. This review focuses on the design and delivery of novel DNA-based vaccines against TB.

Formulation in DDA-MPLA-TDB Liposome Enhances the Immunogenicity and Protective Efficacy of a DNA Vaccine against Mycobacterium tuberculosis Infection

Despite the vaccine Mycobacterium bovis Bacillus Calmette–Guérin is used worldwide, tuberculosis (TB) remains the first killer among infectious diseases. An effective vaccine is urgently required. DNA vaccine has shown prophylactic as well as therapeutic effects against TB, while its weak immunogenicity hinders the application. As a strong inducer of Th1-biased immune response, DMT, consisting of dimethyldioctadecylammonium (DDA) and two pattern recognition receptor agonists monophosphoryl lipid A and trehalose 6,6′-dibehenate (TDB), was a newly developed liposomal adjuvant. To elucidate the action mechanism of DMT and improve immunological effects induced by DNA vaccine, a new recombinant eukaryotic expression plasmid pCMFO that secretes the fusion of four multistage antigens (Rv2875, Rv3044, Rv2073c, and Rv0577) of Mycobacterium tuberculosis was constructed. pCMFO/DDA and pCMFO/DMT complexes were then prepared and their physicochemical properties were analyzed. The immunogenicity and protection against M. tuberculosis infection in vaccinated C57BL/6 mice were compared. Formulation of DNA and two agonists into the DDA liposome decreased zeta potential but increased the stability of storage, which resulted in a slower and longer-lasting release of DNA from the DNA–DMT complex than the DNA–DDA liposome. Besides Th1-biased responses, pCMFO/DMT vaccinated mice elicited more significantly CFMO-specific IL2⁺ T_CM cell responses in the spleen and provided an enhanced and persistent protection against M. tuberculosis aerosol infection, compared to pCMFO/DDA and pCMFO groups. Therefore, the adjuvant DMT can release DNA and agonists slowly, which might attribute to the improved protection of DMT adjuvanted vaccines. pCMFO/DMT, a very promising TB vaccine, warrants for further preclinical and clinical trials.

Designing and Construction Pcdna3.1 Vector Encoding Cfp10 Gene of Mycobacterium tuberculosis

Background:

Pathogenic mycobacteria are a major cause of human morbidity and mortality. Mycobacterium tuberculosis is an etiological agent of human tuberculosis (TB). Designing new vaccines, including DNA vaccines, may be a useful strategy for preventing TB.

Objectives:

The purpose of this study was to design and construct an eukaryotic expression vector containing M. tuberculosis.

Materials and Methods:

Genomic DNA of M. tuberculosis H37Rv cultured on Lowenstein Jensen medium was extracted, and cfp10 was amplified by PCR. After digesting the PCR product and the plasmid, the cfp10 fragment was ligated into the vector pcDNA3.1 (+). Correct insertion was confirmed by colony PCR, restriction enzyme digestion, and sequencing.

Results:

Electrophoresis of the PCR product on gel showed a 303-bp target fragment. Colony PCR, restriction enzyme digestion, and Sequencing methods confirmed the accuracy of the gene cloning. Colony PCR and restriction enzyme digestion confirmed the cloning.

Conclusions:

Cloning of cfp10 of M. tuberculosis into an eukaryotic expression vector was performed successfully. We propose this recombinant plasmid for inducing immunity in animal models in future studies. This recombinant vector can also be used in the construction of fusion proteins.

Multivalent TB vaccines targeting the esx gene family generate potent and broad cell-mediated immune responses superior to BCG

Development of a broad-spectrum synthetic vaccine against TB would represent an important advance to the limited vaccine armamentarium against TB. It is believed that the esx family of TB antigens may represent important vaccine candidates. However, only 4 esx antigens have been studied as potential vaccine antigens. The challenge remains to develop a vaccine that simultaneously targets all 23 members of the esx family to induce enhanced broad-spectrum cell-mediated immunity. We sought to investigate if broader cellular immune responses could be induced using a multivalent DNA vaccine representing the esx family protein members delivered via electroporation. In this study, 15 designed esx antigens were created to cross target all members of the esx family. They were distributed into groups of 3 self-processing antigens each, resulting in 5 trivalent highly optimized DNA plasmids. Vaccination with all 5 constructs elicited robust antigen-specific IFN-γ responses to all encoded esx antigens and induced multifunctional CD4 Th1 and CD8 T cell responses. Importantly, we show that when all constructs are combined into a cocktail, the RSQ-15 vaccine, elicited substantial broad Ag-specific T cell responses to all esx antigens as compared with vaccination with BCG. Moreover, these vaccine-induced responses were highly cross-reactive with BCG encoded esx family members and were highly immune effective in a BCG DNA prime-boost format. Furthermore, we demonstrate the vaccine potential and immunopotent profile of several novel esx antigens never previously studied. These data highlight the likely importance of these novel immunogens for study as preventative or therapeutic synthetic TB vaccines in combination or as stand alone antigens.

DNA vaccination for prostate cancer: key concepts and considerations

While locally confined prostate cancer is associated with a low five year mortality rate, advanced or metastatic disease remains a major challenge for healthcare professionals to treat and is usually terminal. As such, there is a need for the development of new, efficacious therapies for prostate cancer. Immunotherapy represents a promising approach where the host's immune system is harnessed to mount an anti-tumour effect, and the licensing of the first prostate cancer specific immunotherapy in 2010 has opened the door for other immunotherapies to gain regulatory approval. Among these strategies DNA vaccines are an attractive option in terms of their ability to elicit a highly specific, potent and wide-sweeping immune response. Several DNA vaccines have been tested for prostate cancer and while they have demonstrated a good safety profile they have faced problems with low efficacy and immunogenicity compared to other immunotherapeutic approaches. This review focuses on the positive aspects of DNA vaccines for prostate cancer that have been assessed in preclinical and clinical trials thus far and examines the key considerations that must be employed to improve the efficacy and immunogenicity of these vaccines.

Electroporation-mediated gene delivery

Electroporation has been used extensively to transfer DNA to bacteria, yeast, and mammalian cells in culture for the past 30 years. Over this time, numerous advances have been made, from using fields to facilitate cell fusion, delivery of chemotherapeutic drugs to cells and tissues, and most importantly, gene and drug delivery in living tissues from rodents to man. Electroporation uses electrical fields to transiently destabilize the membrane allowing the entry of normally impermeable macromolecules into the cytoplasm. Surprisingly, at the appropriate field strengths, the application of these fields to tissues results in little, if any, damage or trauma. Indeed, electroporation has even been used successfully in human trials for gene delivery for the treatment of tumors and for vaccine development. Electroporation can lead to between 100 and 1000-fold increases in gene delivery and expression and can also increase both the distribution of cells taking up and expressing the DNA as well as the absolute amount of gene product per cell (likely due to increased delivery of plasmids into each cell). Effective electroporation depends on electric field parameters, electrode design, the tissues and cells being targeted, and the plasmids that are being transferred themselves. Most importantly, there is no single combination of these variables that leads to greatest efficacy in every situation; optimization is required in every new setting. Electroporation-mediated in vivo gene delivery has proven highly effective in vaccine production, transgene expression, enzyme replacement, and control of a variety of cancers. Almost any tissue can be targeted with electroporation, including muscle, skin, heart, liver, lung, and vasculature. This chapter will provide an overview of the theory of electroporation for the delivery of DNA both in individual cells and in tissues and its application for in vivo gene delivery in a number of animal models.

DNA vaccines against tuberculosis

INTRODUCTION

Tuberculosis (TB) remains a major health problem and novel vaccination regimens are urgently needed.

AREAS COVERED

DNA vaccines against TB have been tested in various preclinical models and strategies have been developed to increase their immunogenicity in large animal species. DNA vaccines are able to induce a wide variety of immune responses, including CD8(+) T-cell-mediated cytolytic and IFN-γ responses. DNA vaccination may be valuable in heterologous prime-boost strategies with the currently used bacillus Calmette-Guérin (BCG) vaccine. This approach could broaden the antigenic repertoire of BCG and enhance its weak induction of MHC class I-restricted immune responses.

EXPERT OPINION

DNA vaccines offer a number of advantages over certain other types of vaccines, such as the induction of robust MHC class I-restricted cytotoxic T lymphocyte (CTL), their generic manufacturing platform and their relatively low manufacturing costs. Because of their strong potential for inducing memory responses, DNA vaccines are particularly suited for priming immune responses. Furthermore, DNA vaccine technology may help antigen discovery by facilitating screening of candidate vaccines. Co-administration of BCG with plasmid DNA coding for immunodominant, subdominant and phase-specific antigens, poorly expressed by BCG, may lead to the development of improved TB vaccines.

Enhanced therapeutic effects conferred by an experimental DNA vaccine targeting human papillomavirus-induced tumors

Human papillomavirus (HPV) infection is responsible for all cervical cancer cases, other anogenital cancers, and head and neck tumors. The epidemiological relevance of HPV-induced tumors reinforces the need for the development of therapeutic antitumor vaccines. Clinical trials with different vaccine formulations, particularly DNA vaccines, have provided promising results but have still been unable to achieve the immunogenicity required for use in infected patients. In experimental conditions, anticancer HPV-specific vaccines induced E7-specific CD8(+) T-cell responses but did not confer full therapeutic antitumor protection in mice with transplanted HPV-expressing TC-1 cells, which are the most frequently used nonclinical protection correlate for antitumor effects. Our group has developed a DNA vaccine strategy based on the fusion of HPV oncoproteins to the herpes virus gD protein. This vaccine promoted the induction of antigen-specific cytotoxic CD8(+) T-cell responses and partial antitumor therapeutic effects based on the blockade of coinhibitory signals and the enhancement of coactivation mechanisms. In the present study, we report conditions leading to full therapeutic antitumor effects using the TC-1 cell murine model after a single vaccine dose. The combination of a coadministered plasmid encoding IL-2, optimization of the coding sequence for mammalian cells, and the use of different delivery routes resulted in enhancements of the E7-specific cytotoxic CD8(+) T-cell responses and full therapeutic protection under experimental conditions. The combination of these strategies augmented the potency of the DNA vaccine formulation to levels not previously achieved by other therapeutic antitumor vaccines under similar experimental conditions, including some that have been taken to clinical trials.

Immunotherapeutic effects of recombinant adenovirus encoding granulocyte-macrophage colony-stimulating factor in experimental pulmonary tuberculosis

BALB/c mice with pulmonary tuberculosis (TB) develop a T helper cell type 1 that temporarily controls bacterial growth. Bacterial proliferation increases, accompanied by decreasing expression of interferon (IFN)-γ, tumour necrosis factor (TNF)-α and inducible nitric oxide synthase (iNOS). Activation of dendritic cells (DCs) is delayed. Intratracheal administration of only one dose of recombinant adenoviruses encoding granulocyte-macrophage colony-stimulating factor (AdGM-CSF) 1 day before Mycobacterium tuberculosis (Mtb) infection produced a significant decrease of pulmonary bacterial loads, higher activated DCs and increased expression of TNF-α, IFN-γ and iNOS. When AdGM-CSF was given in female mice B6D2F1 (C57BL/6J X DBA/2J) infected with a low Mtb dose to induce chronic infection similar to latent infection and corticosterone was used to induce reactivation, a very low bacilli burden in lungs was detected, and the same effect was observed in healthy mice co-housed with mice infected with mild and highly virulent bacteria in a model of transmissibility. Thus, GM-CSF is a significant cytokine in the immune protection against Mtb and gene therapy with AdGM-CSF increased protective immunity when administered in a single dose 1 day before Mtb infection in a model of progressive disease, and when used to prevent reactivation of latent infection or transmission.

Optimization of a Der p 2-based prophylactic DNA vaccine against house dust mite allergy

DNA vaccines encoding allergens are promising immunotherapeutics to prevent or to treat allergy through induction of allergen-specific Th1 responses. Despite anti-allergy effects observed in small rodents, DNA-based vaccines are weak immunogens in primates and humans and particularly when administered by conventional injection. The goal of the present study was to improve the immunogenicity of a prophylactic vaccine encoding the major house dust mite allergen Der p 2. In this context, we evaluated the influence of different DNA backbones including notably intron and CpG enriched sequence, the DNA dose, the in vivo delivery by electroporation as well as the heterologous prime boost regimen on the vaccine efficiency. We found that a minimal allergen expression level threshold must be reached to induce the production of specific antibodies but beyond this limit, the intensity of the immune response was independent on the DNA dose and allergen expression. The in vivo DNA delivery by electroporation drastically enhanced the production of specific antibodies but not the IFNg secretion. Vaccination of naïve mice with DNA encoding Der p 2 delivered by electroporation even at very low dose (2μg) prevented the development of house dust mite allergy through Th1-skewed immune response characterized by the drastic reduction of allergen-specific IgE, IL-5 and lung inflammation together with the induction of strong specific IgG2a titers and IFNg secretion. CpG cassette in the DNA backbone does not play a critical role in the efficient prophylaxis. Finally, comparable protective immune responses were observed when using heterologous DNA prime/protein boost or homologous DNA prime/boost. Taken together, these data suggest that the potent Th1 response induced by DNA-based vaccine encoding allergens through electroporation provides the rationale for the evaluation of DNA encoding Der p 2 into HDM allergy clinical trials.

Enhanced potency of replicon vaccine using one vector to simultaneously co-express antigen and interleukin-4 molecular adjuvant

We evaluated the utility of interleukin-4 (IL-4) as molecular adjuvant of replicon vaccines for botulinum neurotoxin serotype A (BoNT/A) in mouse model. In both Balb/c and C57/BL6 mice that received the plasmid DNA replicon vaccines derived from Semliki Forest virus (SFV) encoding the Hc gene of BoNT/A (AHc), the immunogenicity was significantly modulated and enhanced by co-delivery or co-express of the IL-4 molecular adjuvant. The enhanced potencies were also produced by co-delivery or co-expression of the IL-4 molecular adjuvant in mice immunized with the recombinant SFV replicon particles (VRP) vaccines. In particular, when AHc and IL-4 were co-expressed within the same replicon vaccine vector using dual-expression or bicistronic IRES, the anti-AHc antibody titers, serum neutralization titers and survival rates of immunized mice after challenged with BoNT/A were significantly increased. These results indicate IL-4 is an effective Th2-type adjuvant for the replicon vaccines in both strain mice, and the co-expression replicon vaccines described here may be an excellent candidate for further vaccine development in other animals or humans. Thus, we described a strategy to design and develop efficient vaccines against BoNT/A or other pathogens using one replicon vector to simultaneously co-express antigen and molecular adjuvant.

Enhanced cellular immune response elicited by a DNA vaccine fused with Ub against Mycobacterium tuberculosis

This study evaluated the immune response elicited by a Ub-fused Ag85A DNA vaccine against Mycobacterium tuberculosis. BALB/c mice were vaccinated with plasmid DNA encoding Ag85A protein, Ub-fused Ag85A DNA vaccine (UbGR-Ag85A) and negative DNA vaccines, respectively. Ag85A DNA vaccine immunization induced a Th(l)-polarized immune response. The production of Th(l)-type cytokine (IFN-γ) and proliferative T cell responses was enhanced significantly in mice immunized with UbGR-Ag85A fusion DNA vaccine, compared with non-fusion DNA vaccine. Moreover, this fusion DNA vaccine also resulted in an increased relative ratio of IgG(2a) to IgG(l) and the cytotoxicity of T cells. IFN-γ intracellular staining of splenocytes indicated that UbGR-Ag85A fusion DNA vaccine activated CD4(+) and CD8(+) T cells, particularly CD8(+) T cells. Thus, this study demonstrated that the UbGR-Ag85A fusion DNA vaccine inoculation could improve antigen-specific cellular immune responses, which is helpful for protection against TB infection.

Suppressive effects on the immune response and protective immunity to a JEV DNA vaccine by co-administration of a GM-CSF-expressing plasmid in mice

As a potential cytokine adjuvant of DNA vaccines, granulocyte-macrophage colony–stimulating factor (GM-CSF) has received considerable attention due to its essential role in the recruitment of antigen-presenting cells, differentiation and maturation of dendritic cells. However, in our recent study of a Japanese encephalitis virus (JEV) DNA vaccine, co-inoculation of a GM-CSF plasmid dramatically suppressed the specific IgG response and resulted in decreased protection against JEV challenge. It is known that GM-CSF has been used in clinic to treat neutropenia for repopulating myeloid cells, and as an adjuvant in vaccine studies; it has shown various effects on the immune response. Therefore, in this study, we characterized the suppressive effects on the immune response to a JEV DNA vaccine by the co-administration of the GM-CSF-expressing plasmid and clarified the underlying mechanisms of the suppression in mice. Our results demonstrated that co-immunization with GM-CSF caused a substantial dampening of the vaccine-induced antibody responses. The suppressive effect was dose- and timing-dependent and likely related to the immunogenicity of the antigen. The suppression was associated with the induction of immature dendritic cells and the expansion of regulatory T cells but not myeloid-derived suppressor cells. Collectively, our findings not only provide valuable information for the application of GM-CSF in clinic and using as a vaccine adjuvant but also offer further insight into the understanding of the complex roles of GM-CSF.

Cellular magnetic resonance imaging of monocyte-derived dendritic cell migration from healthy donors and cancer patients as assessed in a scid mouse model

BACKGROUND AIMS. The use of dendritic cells (DC) as an adjuvant in cell-based immunotherapeutic cancer vaccines is a growing field of interest. A reliable and non-invasive method to track the fate of autologous DC following their administration to patients is required in order to confirm that clinically sufficient numbers are reaching the lymph node (LN). We demonstrate that an immunocompromised mouse model can be used to conduct translational studies employing cellular magnetic resonance imaging (MRI). Such studies can provide clinically relevant information regarding the migration potential of clinical-grade DC used in cancer immunotherapies. METHODS. Human monocyte-derived dendritic cells (mo-DC) were generated from negatively selected monocytes obtained from either healthy donors or cancer patients. DC were labeled with superparamagnetic iron oxide (SPIO) nanoparticles in order to track them in vivo in a CB17scid mouse model using cellular MRI. SPIO did not have any adverse effects on DC phenotype or function, independent of donor type. Cellular MRI readily detected migration of SPIO-loaded DC in CB17scid mice. No differences in migration were observed between DC obtained from healthy donors and those obtained from donors undergoing autologous stem cell transplant for cancer therapy. CONCLUSIONS. Cellular MRI provided semi-quantitative image data that corresponded with data obtained by digital morphometry, validating cellular MRI's potential to assess DC migration in DC-based cancer immunotherapy clinical trials.

Improved cellular immune response elicited by a ubiquitin-fused DNA vaccine against Mycobacterium tuberculosis

This study evaluated the immune response elicited by a ubiquitin (Ub)-fused MPT64 DNA vaccine against Mycobacterium tuberculosis. BALB/c mice were vaccinated with plasmid DNA encoding MPT64 protein, Ub-fused MPT64 DNA vaccine (UbGR-MPT64), and negative DNA vaccines, respectively. MPT64 DNA vaccine immunization induced a Thl-polarized immune response. The production of Thl-type cytokine (interferon-gamma [IFN-γ]) and proliferative T cell responses were enhanced significantly in mice immunized with UbGR-MPT64 fusion DNA vaccine, compared with nonfusion DNA vaccine. Moreover, this fusion DNA vaccine also resulted in an increased relative ratio of IgG2a to IgGl and the cytotoxicity of T cells. IFN-γ intracellular staining of splenocytes indicated that UbGR-mpt64 fusion DNA vaccine activated CD4+ and CD8+ T cells, particularly CD8+ T cells. Thus, this study demonstrated that the UbGR-MPT64 fusion DNA vaccine inoculation could improve antigen-specific cellular immune responses, which is helpful for protection against TB.

Enhancement of the immunogenicity of DNA replicon vaccine of Clostridium botulinum neurotoxin serotype A by GM-CSF gene adjuvant

Granulocyte-macrophage clony-stimulating factor (GM-CSF) is an attractive adjuvant for a DNA vaccine on account of its ability to recruit antigen-presenting cells to the site of antigen synthesis as well as stimulate the maturation of dendritic cells.This study evaluated the utility of GM-CSF as a plasmid DNA replicon vaccine adjuvants for botulinum neurotoxin serotype A (BoNT/A) in mouse model. In balb/c mice that received the plasmid DNA replicon vaccines derived from Semliki Forest virus (SFV) carrying the Hc gene of BoNT/A (AHc), both antibody and lymphoproliferative response specific to AHc were induced, the immunogenicity was enhanced by co-delivery or coexpress of the GM-CSF gene. In particular, when AHc and GM-CSF were coexpressed within the SFV based DNA vaccine, the anti-AHc antibody titers and survival rates of immunized mice after challenged with BoNT/A were significantly increased, and further enhanced by coimmunization with aluminum phosphate adjuvant.

Serum amyloid P component facilitates DNA clearance and inhibits plasmid transfection: implications for human DNA vaccine

The demonstration that naked plasmid DNA can induce strong immune responses in mice has attracted considerable attention in the vaccine community. However, similar immunizations have been less/not effective in clinical trials during the past decade, and the underlying mechanisms remain unknown. In this study, we hypothesized that some DNA-binding proteins in human serum may serve as host barriers, responsible for the low efficiency of plasmids' transfection in vivo. Using proteomics, we showed that human serum amyloid P component (hSAP) is specifically present in human DNA-protein complexes. Further analysis indicated that hSAP effectively binds plasmid DNA, inhibits DNA transfection into somatic cells and facilitates the endocytosis of DNA by macrophages, whereas mouse SAP (mSAP) has similar, but much weaker, activities. In the presence of hSAP, the plasmid DNA expression in vivo and plasmid DNA-induced immune responses also significantly decreased. Therefore, our results suggest that hSAP contributes to extracellular DNA clearance and the inhibition of plasmid DNA transfection in vivo. This mechanism may be partly responsible for the insufficient immune responses to DNA vaccination in human beings; therefore, it may serve as a novel target for the improvement of DNA vaccines and DNA-based gene therapy.

Airway luminal T cells: a newcomer on the stage of TB vaccination strategies

Protection against pulmonary tuberculosis (TB) by vaccination is often ascribed to the presence of TB-reactive T cells in the lung before infection. Challenging this view, new studies analyzing vaccine-induced T cells in various tissue compartments after parenteral immunization suggest a poor correlation between the presence of anti-TB T cells in the lung interstitium and spleen before Mycobacterium tuberculosis exposure and protection. In contrast, respiratory mucosal immunization leads to distribution of T cells not only in the lung interstitium and spleen, but also in the airway lumen, and the presence of these cells correlates well with protection. Furthermore, airway luminal recruitment of parenteral vaccine-induced T cells in peripheral tissues prior to M. tuberculosis challenge restores protection. We propose that understanding the biology of airway luminal T cells holds important implications for developing effective TB vaccination strategies.

Comparative measurement of cell-mediated immune responses of swine to the M and N proteins of porcine reproductive and respiratory syndrome virus

The principal objectives of this study were to develop autologous antigen-presenting cells (APCs) and to characterize the antigen-specific T-cell responses to the M and N proteins of porcine reproductive and respiratory syndrome virus (PRRSV) by using those APCs in outbred pigs. The orf6 and orf7 genes fused with porcine granulocyte-macrophage colony-stimulating factor (GM-CSF) were cloned into the mammalian expression vector to generate two plasmid DNAs, namely, pcDNA3.1-GM-CSF-PRRSV-M and pcDNA3.1-GM-CSF-PRRSV-N. Three of six pigs in two groups were repeatedly immunized with either plasmid DNA construct, and four pigs were used as controls. The recombinant M and N proteins fused with the protein transduction domain (PTD) of the human immunodeficiency virus type 1 transactivator of transcription protein were employed to generate major histocompatibility complex-matched autologous APCs from each pig. The levels of T-cell proliferation and gamma interferon (IFN-gamma) synthesis were compared between pigs immunized with the two plasmid DNAs after stimulation of the peripheral blood mononuclear cells (PBMCs) of each pig with the autologous antigen-presenting dendritic cells and PBMCs. Higher levels of T-cell proliferation and IFN-gamma synthesis were identified in PBMCs isolated from the pigs immunized with pcDNA3.1-GM-CSF-PRRSV-M than in those isolated from the pigs immunized with pcDNA3.1-GM-CSF-PRRSV-N. By way of contrast, serum antibodies were detected only in pigs immunized with pcDNA3.1-GM-CSF-PRRSV-N. However, no T-cell response or antibody production was detected in the control pigs. These results suggest that the M protein of PRRSV is a more potent T cell-stimulating antigen than the N protein. Nevertheless, it should be emphasized that the N protein substantially induces both cellular and humoral immune responses. The newly developed protocol for generating self APCs may prove effective in further efforts to characterize additional PRRSV proteins involved in the induction of cell-mediated immunity.

Gene electrotransfer: from biophysical mechanisms to in vivo applications : Part 2 - In vivo developments and present clinical applications

Gene electrotransfer can be obtained not just on single cells in diluted suspension. For more than 10 years, this is a quasi routine strategy in tissue on the living animal and a few clinical trials have now been approved. New problems have been brought by the close contacts of cells in tissue both on the local field distribution and on the access of DNA to target cells. They need to be solved to provide a further improvement in the efficacy and safety of protein expression. There is a competition between gene transfer and cell destruction. Nevertheless, present results are indicative that electrotransfer is a promising approach for gene therapy. High level and long-lived expression of proteins can be obtained in muscles. This is used for a successful method of electrovaccination.

Improved cellular immune response elicited by a ubiquitin-fused ESAT-6 DNA vaccine against Mycobacterium tuberculosis

The present study evaluated the immune response elicited by a ubiquitin-fused ESAT-6 DNA vaccine against Mycobacterium tuberculosis. BALB/c mice were vaccinated with plasmid DNA encoding ESAT-6 protein, ubiquitin-fused ESAT-6 DNA vaccine (UbGR-ESAT-6), pcDNA3-ubiquitin and blank vector, respectively. ESAT-6 DNA vaccine immunization induced a Thl-polarized immune response. The production of Thl-type cytokine (IFN-gamma) and proliferative T-cell responses was enhanced significantly in mice immunized with UbGR-ESAT-6 fusion DNA vaccine, compared to non-fusion DNA vaccine. This fusion DNA vaccine also resulted in an increased relative ratio of IgG(2a) to IgG(l) and the cytotoxicity of T cells. Thus, the present study demonstrated that the UbGR-ESAT-6 fusion DNA vaccine inoculation improved antigen-specific cellular immune responses, which is helpful for protection against tuberculosis infection.

Immunization with a bivalent adenovirus-vectored tuberculosis vaccine provides markedly improved protection over its monovalent counterpart against pulmonary tuberculosis

Recombinant virus-vectored vaccines hold great promise for tuberculosis (TB) vaccination strategies. However, there is a lack of side-by-side comparative investigations to dissect the functional differences and support the advantage of multivalent virus-vectored vaccine over its monovalent counterpart. We previously successfully developed a monovalent adenovirus (Ad)-vectored vaccine expressing Ag85a (AdAg85a) and demonstrated its superior protective efficacy in models of pulmonary TB. In this study, we have developed a bivalent Ad TB vaccine expressing Ag85a and TB10.4 antigens as a fusion protein (AdAg85a:TB10.4) and compared its T-cell-activating and immune protective efficacy with that by monovalent AdAg85a. A single intranasal (i.n.) administration of AdAg85a:TB10.4 induced robust T-cell responses toward the respective antigens within the airway lumen and spleen, although the level of Ag85a-specific T-cell responses in the airway lumen triggered by bivalent AdAg85a:TB10.4 was lower than that by its monovalent counterpart at earlier time points. Thus, a single i.n. delivery of AdAg85a:TB10.4 conferred a markedly improved and sustained level of protection in the lung against Mycobacterium tuberculosis (M.tb) challenge over that by AdAg85a or by conventional BCG immunization with similarly induced levels of protection in the spleen. Our results indicate a unique advantage of multivalent viral-vectored TB vaccines for immunization against pulmonary TB.

CD11c+ antigen presenting cells from the alveolar space, lung parenchyma and spleen differ in their phenotype and capabilities to activate naïve and antigen-primed T cells

Background

The lung is divided into two major compartments: the alveolar space and the parenchyma. The alveolar macrophages are the first line of leukocytes in the lung taking up incoming microbes or microbial antigens whereas the parenchymal dendritic cells (DCs) are believed to be the sole potent antigen presenting cells (APCs) in the lung. Both resting alveolar macrophages and parenchymal DCs express CD11c. Several important questions remain to be elucidated: 1] to which extent the alveolar space and lung parenchymal CD11c+ APCs differ in their phenotype and ability to activate naïve T cells; 2] whether they differ in their ability to activate antigen-experienced or -primed T cells; and 3] whether these lung CD11c+ APC populations differ from the splenic CD11c+ APCs which have been commonly used for understanding APC biology.

Results

CD11c+ APCs from the alveolar space, lung parenchyma, and the spleen display differential co-stimulatory molecule expression and cytokine responsiveness upon stimulation. Alveolar space APCs are weak activators of naïve T cells compared to lung parenchymal and splenic CD11c+ APC populations. However, alveolar space APCs are able to potently activate the in vivo microbial antigen-primed T cells to a similar extent as lung parenchymal and splenic APCs.

Conclusion

Together our findings indicate that alveolar CD11c+ APCs have a specialized T cell-activating function, capable of activating antigen-primed, but not naïve, T cells whereas lung CD11c+ APCs are capable of activating both the naïve and antigen-primed T cell populations.

Immune responses and protective efficacy of the gene vaccine expressing Ag85B and ESAT6 fusion protein from Mycobacterium tuberculosis

Genetic immunity is a new promising approach for the development of novel tuberculosis vaccines. In this study, it is shown that DNA vaccines expressing the fusion protein of antigen 85B (Ag85B) and early secreted antigenic target 6-kDa antigen (ESAT6) can induce high levels of specific IgG2a antibody subtype in the mice. With the prolongation of postimmunization time, the levels of IgG2a antibody decrease gradually. Although a high-level specific IgG2a antibody subtype is also elicited by classical BCG, the ratio of antibody subtypes IgG2a to IgG1 changes 4 weeks after immunization, and IgG1 is gradually shifted to the main antibody subtype. DNA vaccines also elicit cellular immunity as shown by specific spleen lymphocytes proliferation to Ag85B or ESAT6 protein and the production of high levels of IFN-gamma and IL-2, which is similar to that elicited by BCG. Vaccination of mice with DNA vaccines expressing the fusion protein Ag85B-ESAT6 results in a significant level of protection against the subsequent high-dose challenge with virulent Mycobacterium tuberculosis (MTB) H37Rv. Dramatic reduction in the number of MTB colony-forming units in the spleens and lungs is observed. Pathological examination showed that recombinant plasmid and BCG groups have only minor damage and organizational structures that are kept relatively complete, while in the control group, spleens and lungs are damaged seriously. Therefore, although the reducing degree of mycobacterial loads in the organ of mice immunized with recombinant plasmid is not more than that of BCG, through the analysis of pathological changes, we may conclude that the protective effect provided by DNA vaccine expressing the Ag85B-ESAT6 fusion protein is equivalent to that afforded by the classical BCG.