Intradermal gene immunization: the possible role of DNA uptake in the induction of cellular immunity to viruses

Clinical research progress of telomerase targeted cancer immunotherapy: a literature review

Background and Objective

Telomerase is activated or overexpressed in 85-90% of tumors, which maintains the length of telomere and has become an important anti-cancer target. Increasing clinical and preclinical data suggest that telomerase-targeted cancer immunotherapy could achieve effective killing of tumor cells in vivo. This article reviews the research progress of telomerase targeted cancer immunotherapy in clinical and pre-clinical trials, aiming to provide a reference for further clinical research and treatment of cancers.

Methods

We investigated the research progress of telomerase immunotherapy in the last 20 years from four electronic databases.

Key Content and Findings

Telomerase-targeted immunotherapies have been developed with the arising of a new era in immuno-oncology, including peptide vaccines, DNA vaccines, dendritic cells (DCs), adoptive cell transfer (ACT) therapies, antibodies, etc. Some of them have been approved for undergoing clinical trials by the Food and Drug Administration (FDA) for the treatment of various cancers, such as pancreatic cancer, non-small cell lung cancer, melanoma, leukaemia. Of all the treatment modalities, vaccines are the primary treatment methods, some of which have been even entered into phase III clinical trials. The main clinical application direction of telomerase vaccine is the combination with other drugs and treatment modalities, including combination with other vaccines targeting human telomerase reverse transcriptase (hTERT), traditional chemotherapy drugs and immunosuppressors. We also summarized the recent findings of immunotherapy targeting hTERT, focusing on various vaccines and the current status of associated clinical trials. We further discussed the advantages, disadvantages and potential developmental directions of various telomerase-targeted immunotherapies.

Conclusions

Telomerase-targeted cancer immunotherapy has promising prospects in improving patient survival expectancy. This review may provide data support and design ideas for all researchers and pharmaceutical enterprises in this field.

Antigen-loaded flagellate bacteria for enhanced adaptive immune response by intradermal injection

Since the skin limits the distribution of intradermal vaccines, a large number of dendritic cells in the skin cannot be fully utilized to elicit a more effective immune response. Here, we loaded the antigen to the surface of the flagellate bacteria that was modified by cationic polymer, thus creating antigen-loaded flagellate bacteria (denoted as 'FB-Ag') to overcome the skin barrier and perform the active delivery of antigen in the skin. The FB-Ag showed fast speed (∼0.2 μm s-1) and strong dendritic cell activation capabilities in the skin model in vitro. In vivo, the FB-Ag promoted the spread of antigen in the skin through active movement, increased the contact between Intradermal dendritic cells and antigen, and effectively activated the internal dendritic cells in the skin. In a mouse of pulmonary metastatic melanoma and in mice bearing subcutaneous melanoma tumor, the FB-Ag effectively increased antigen-specific therapeutic efficacy and produced long-lasting immune memory. More importantly, the FB-Ag also enhanced the level of COVID-19 specific antibodies in the serum and the number of memory B cells in the spleen of mice. The movement of antigen-loaded flagellate bacteria to overcome intradermal constraints may enhance the activation of intradermal dendritic cells, providing new ideas for developing intradermal vaccines.

Co-administration of a plasmid encoding CD40 or CD63 enhances the immune responses to a DNA vaccine against bovine viral diarrhea virus in mice

Bovine viral diarrhea virus (BVDV) causes substantial economic losses in the livestock industry worldwide. Plasmids encoding the BVDV E2 protein are potential DNA vaccines against BVDV, but their immunogenicity has been insufficient. Here, we investigated the adjuvant effect of CD40 and CD63 plasmids on the immune responses to a BVDV E2 DNA vaccine in mice. We constructed pUMVC4a-based plasmids encoding the BVDV E2 protein (pE2), mouse CD40 (pCD40), or mouse CD63 (pCD63). Protein expression by each plasmid was confirmed through Western blot analysis and immunofluorescence staining of cultured cell lines. BALB/c mice were immunized intradermally twice with pE2 in combination with, or without, pCD40 or pCD63, with 3 weeks between the two doses. pE2 with pCD40 induced significantly higher neutralizing antibody titers against BVDV than pE2 alone. pE2 with pCD63 induced significantly higher anti-E2 IgG2a antibody titers than pE2 alone. Furthermore, pE2 with pCD40 or pCD63 induced significantly increased lymphocyte proliferation and interferon (IFN)-γ production in response to BVDV, compared with E2 alone. These results suggest that a plasmid encoding CD40 or CD63 can be used as an adjuvant to enhance immune responses to DNA vaccines against BVDV.

Antigen-bearing outer membrane vesicles as tumour vaccines produced in situ by ingested genetically engineered bacteria

The complex gastrointestinal environment and the intestinal epithelial barrier constrain the design and effectiveness of orally administered tumour vaccines. Here we show that outer membrane vesicles (OMVs) fused to a tumour antigen and produced in the intestine by ingested genetically engineered bacteria function as effective tumour vaccines in mice. We modified Escherichia coli to express, under the control of a promoter induced by the monosaccharide arabinose, a specific tumour antigen fused with the protein cytolysin A on the surface of OMVs released by the commensal bacteria. In mice, oral administration of arabinose and the genetically engineered E. coli led to the production of OMVs that crossed the intestinal epithelium into the lamina propria, where they stimulated dendritic cell maturation. In a mouse model of pulmonary metastatic melanoma and in mice bearing subcutaneous colon tumours, the antigen-bearing OMVs inhibited tumour growth and protected the animals against tumour re-challenge. The in situ production of OMVs by genetically modified commensal bacteria for the delivery of stimulatory molecules could be leveraged for the development of other oral vaccines and therapeutics.

Anti-Inflammatory Gene Therapy Improves Spatial Memory Performance in a Mouse Model of Alzheimer's Disease

The immune system plays a critical role in neurodegenerative processes involved in Alzheimer’s disease (AD). In this study, a gene-based immunotherapeutic method examined the effects of anti-inflammatory cellular immune response elements (CIREs) in the amyloid-β protein precursor (AβPP) mouse model. Bi-monthly intramuscular administration, beginning at either 4 or 6 months, and examined at 7.5 through 16 months, with plasmids encoding Interleukin (IL)-10, IL-4, TGF-β polynucleotides, or a combination thereof, into AβPP mice improved spatial memory performance. This work demonstrates an efficient gene therapy strategy to downregulate neuroinflammation, and possibly prevent or delay cognitive decline in AD.

The dark side of immunotherapy: pancreatic cancer

Since the journal Science deemed cancer immunotherapy as the "breakthrough of the year" in 2014, there has been an explosion of clinical trials involving immunotherapeutic approaches that, in the last decade - thanks also to the renaissance of the immunosurveillance theory (renamed the three Es theory) - have been continuously and successfully developed. In the latest update of the development of the immuno-oncology drug pipeline, published last November by Nature Review Drug Discovery, it was clearly reported that the immunoactive drugs under study almost doubled in just two years. Of the different classes of passive and active immunotherapies, "cell therapy" is the fastest growing. The aim of this review is to discuss the preclinical and clinical studies that have focused on different immuno-oncology approaches applied to pancreatic cancer, which we assign to the "dark side" of immunotherapy, in the sense that it represents one of the solid tumors showing less response to this type of therapeutic strategy.

New Aspects of Ultrasound-Mediated Targeted Delivery and Therapy for Cancer

Ultrasound-mediated targeted delivery (UMTD), a novel delivery modality of therapeutic materials based on ultrasound, shows great potential in biomedical applications. By coupling ultrasound contrast agents with therapeutic materials, UMTD combines the advantages of ultrasound imaging and carrier, which benefit deep tissue penetration and high concentration aggregation. In this paper we introduced recent advances in ultrasound contrast agents and applications in tumor therapy. Ultrasound contrast agents were categorized by their functions, mainly including thermosensitive, pH-sensitive and photosensitive ultrasound contrast agents. The various applications of UMTD in tumor treatment were summarized as follows: drug therapy, transfection of anti-oncogene, RNA interference, vaccine immunotherapy, monoclonal antibody immunotherapy, adoptive cellular immunotherapy, cytokine immunotherapy, and so on. In the end, we elaborated on the current challenges and provided perspectives of UMTD for clinical applications.

DNA vaccine based on conserved HA-peptides induces strong immune response and rapidly clears influenza virus infection from vaccinated pigs

Swine influenza virus (SIVs) infections cause a significant economic impact to the pork industry. Moreover, pigs may act as mixing vessel favoring genome reassortment of diverse influenza viruses. Such an example is the pandemic H1N1 (pH1N1) virus that appeared in 2009, harboring a combination of gene segments from avian, pig and human lineages, which rapidly reached pandemic proportions. In order to confront and prevent these possible emergences as well as antigenic drift phenomena, vaccination remains of vital importance. The present work aimed to evaluate a new DNA influenza vaccine based on distinct conserved HA-peptides fused with flagellin and applied together with Diluvac Forte as adjuvant using a needle-free device (IntraDermal Application of Liquids, IDAL®). Two experimental pig studies were performed to test DNA-vaccine efficacy against SIVs in pigs. In the first experiment, SIV-seronegative pigs were vaccinated with VC4-flagellin DNA and intranasally challenged with a pH1N1. In the second study, VC4-flagellin DNA vaccine was employed in SIV-seropositive animals and challenged intranasally with an H3N2 SIV-isolate. Both experiments demonstrated a reduction in the viral shedding after challenge, suggesting vaccine efficacy against both the H1 and H3 influenza virus subtypes. In addition, the results proved that maternally derived antibodies (MDA) did not constitute an obstacle to the vaccine approach used. Moreover, elevated titers in antibodies both against H1 and H3 proteins in serum and in bronchoalveolar lavage fluids (BALFs) was detected in the vaccinated animals along with a markedly increased mucosal IgA response. Additionally, vaccinated animals developed stronger neutralizing antibodies in BALFs and higher inhibiting hemagglutination titers in sera against both the pH1N1 and H3N2 influenza viruses compared to unvaccinated, challenged-pigs. It is proposed that the described DNA-vaccine formulation could potentially be used as a multivalent vaccine against SIV infections.

A poly-neoantigen DNA vaccine synergizes with PD-1 blockade to induce T cell-mediated tumor control

The combination of immune-stimulating strategies has the potency to improve immunotherapy of cancer. Vaccination against neoepitopes derived from patient tumor material can generate tumor-specific T cell immunity, which could reinforce the efficacy of checkpoint inhibitor therapies such as anti-PD-1 treatment. DNA vaccination is a versatile platform that allows the inclusion of multiple neoantigen-coding sequences in a single formulation and therefore represents an ideal platform for neoantigen vaccination. We developed an anti-tumor vaccine based on a synthetic DNA vector designed to contain multiple cancer-specific epitopes in tandem. The DNA vector encoded a fusion gene consisting of three neoepitopes derived from the mouse colorectal tumor MC38 and their natural flanking sequences as 40 amino acid stretches. In addition, we incorporated as reporter epitopes the helper and CTL epitope sequences of ovalbumin. The poly-neoantigen DNA vaccine elicited T cell responses to all three neoantigens and induced functional CD8 and CD4 T cell responses to the reporter antigen ovalbumin after intradermal injection in mice. The DNA vaccine was effective in preventing outgrowth of B16 melanoma expressing ovalbumin in a prophylactic setting. Moreover, the combination of therapeutic DNA vaccination and anti-PD-1 treatment was synergistic in controlling MC38 tumor growth whereas individual treatments did not succeed. These data demonstrate the potential of DNA vaccination to target multiple neoepitopes in a single formulation and highlight the cooperation between vaccine-based and checkpoint blockade immunotherapies for the successful eradication of established tumors.

Novel approaches for the design, delivery and administration of vaccine technologies

It is easy to argue that vaccine development represents humankind's most important and successful endeavour, such is the impact that vaccination has had on human morbidity and mortality over the last 200 years. During this time the original method of Jenner and Pasteur, i.e. that of injecting live-attenuated or inactivated pathogens, has been developed and supplemented with a wide range of alternative approaches which are now in clinical use or under development. These next-generation technologies have been designed to produce a vaccine that has the effectiveness of the original live-attenuated and inactivated vaccines, but without the associated risks and limitations. Indeed, the method of development has undoubtedly moved away from Pasteur's three Is paradigm (isolate, inactivate, inject) towards an approach of rational design, made possible by improved knowledge of the pathogen-host interaction and the mechanisms of the immune system. These novel vaccines have explored methods for targeted delivery of antigenic material, as well as for the control of release profiles, so that dosing regimens can be matched to the time-lines of immune system stimulation and the realities of health-care delivery in dispersed populations. The methods by which vaccines are administered are also the subject of intense research in the hope that needle and syringe dosing, with all its associated issues regarding risk of injury, cross-infection and patient compliance, can be replaced. This review provides a detailed overview of new vaccine vectors as well as information pertaining to the novel delivery platforms under development.

Conserved HA-peptide NG34 formulated in pCMV-CTLA4-Ig reduces viral shedding in pigs after a heterosubtypic influenza virus SwH3N2 challenge

Swine influenza viruses (SIVs), the causal agents of swine influenza, are not only important to control due to the economic losses in the swine industry, but also can be pandemic pathogens. Vaccination is one of the most relevant strategies to control and prevent influenza infection. Current human vaccines against influenza induce strain-specific immunity and annual update is required due to the virus antigenic shift phenomena. Previously, our group has reported the use of conserved hemagglutinin peptides (HA-peptides) derived from H1-influenza virus as a potential multivalent vaccine candidate. Immunization of swine with these HA-peptides elicited antibodies that recognized and neutralized heterologous influenza viruses in vitro and demonstrated strong hemagglutination-inhibiting activity. In the present work, we cloned one HA-peptide (named NG34) into a plasmid fused with cytotoxic T lymphocyte-associated antigen (CTLA4) which is a molecule that modifies T cell activation and with an adjuvant activity interfering with the adaptive immune response. The resulting plasmid, named pCMV-CTLA4-Ig-NG34, was administered twice to animals employing a needle-free delivery approach. Two studies were carried out to test the efficacy of pCMV-CTLA4-Ig-NG34 as a potential swine influenza vaccine, one in seronegative and another in seropositive pigs against SIV. The second one was aimed to evaluate whether pCMV-CTLA4-Ig-NG34 vaccination would overcome maternally derived antibodies (MDA). After immunization, all animals were intranasally challenged with an H3N2 influenza strain. A complete elimination or significant reduction in the viral shedding was observed within the first week after the challenge in the vaccinated animals from both studies. In addition, no challenged heterologous virus load was detected in the airways of vaccinated pigs. Overall, it is suggested that the pCMV-CTLA4-Ig-NG34 vaccine formulation could potentially be used as a multivalent vaccine against influenza viruses.

TcVac1 vaccine delivery by intradermal electroporation enhances vaccine induced immune protection against Trypanosoma cruzi infection in mice

The efforts for the development and testing of vaccines against Trypanosoma cruzi infection have increased during the past years. We have designed a TcVac series of vaccines composed of T. cruzi derived, GPI-anchored membrane antigens. The TcVac vaccines have been shown to elicit humoral and cellular mediated immune responses and provide significant (but not complete) control of experimental infection in mice and dogs. Herein, we aimed to test two immunization protocols for the delivery of DNA-prime/DNA-boost vaccine (TcVac1) composed of TcG2 and TcG4 antigens in a BALB/c mouse model. Mice were immunized with TcVac1 through intradermal/electroporation (IDE) or intramuscular (IM) routes, challenged with T. cruzi, and evaluated during acute phase of infection. The humoral immune response was evaluated through the assessment of anti-TcG2 and anti-TcG4 IgG subtypes by using an ELISA. Cellular immune response was assessed through a lymphocyte proliferation assay. Finally, clinical and morphopathological aspects were evaluated for all experimental animals. Our results demonstrated that when comparing TcVac1 IDE delivery vs IM delivery, the former induced significantly higher level of antigen-specific antibody response (IgG2a + IgG2b > IgG1) and lymphocyte proliferation, which expanded in response to challenge infection. Histological evaluation after challenge infection showed infiltration of inflammatory cells (macrophages and lymphocytes) in the heart and skeletal tissue of all infected mice. However, the largest increase in inflammatory infiltrate was observed in TcVac1_IDE/Tc mice when compared with TcVac1_IM/Tc or non-vaccinated/infected mice. The extent of tissue inflammatory infiltrate was directly associated with the control of tissue amastigote nests in vaccinated/infected (vs. non-vaccinated/infected) mice. Our results suggest that IDE delivery improves the protective efficacy of TcVac1 vaccine against T. cruzi infection in mice when compared with IM delivery of the vaccine.

B lymphocytes as direct antigen-presenting cells for anti-tumor DNA vaccines

In spite of remarkable preclinical efficacy, DNA vaccination has demonstrated low immunogenicity in humans. While efforts have focused on increasing cross-presentation of DNA-encoded antigens, efforts to increase DNA vaccine immunogenicity by targeting direct presentation have remained mostly unexplored. In these studies, we compared the ability of different APCs to present antigen to T cells after simple co-culture with plasmid DNA. We found that human primary peripheral B lymphocytes, and not monocytes or in vitro derived dendritic cells (DCs), were able to efficiently encode antigen mRNA and expand cognate tumor antigen-specific CD8 T cells ex vivo. Similarly, murine B lymphocytes co-cultured with plasmid DNA, and not DCs, were able to prime antigen-specific T cells in vivo. Moreover, B lymphocyte-mediated presentation of plasmid antigen led to greater Th1-biased immunity and was sufficient to elicit an anti-tumor effect in vivo. Surprisingly, increasing plasmid presentation by B cells, and not cross presentation of peptides by DCs, further augmented traditional plasmid vaccination. Together, these data suggest that targeting plasmid DNA to B lymphocytes, for example through transfer of ex vivo plasmidloaded B cells, may be novel means to achieve greater T cell immunity from DNA vaccines.

Prime-boost immunization by both DNA vaccine and oncolytic adenovirus expressing GM-CSF and shRNA of TGF-β2 induces anti-tumor immune activation

A successful DNA vaccine for the treatment of tumors should break established immune tolerance to tumor antigen. However, due to the relatively low immunogenicity of DNA vaccines, compared to other kinds of vaccines using live virus or protein, a recombinant viral vector was used to enhance humoral and cellular immunity. In the current study, we sought to develop a novel anti-cancer agent as a complex of DNA and oncolytic adenovirus for the treatment of malignant melanoma in the C57BL/6 mouse model. MART1, a human melanoma-specific tumor antigen, was used to induce an increased immune reaction, since a MART1-protective response is required to overcome immune tolerance to the melanoma antigen MelanA. Because GM-CSF is a potent inducer of anti-tumor immunity and TGF-β2 is involved in tumor survival and host immune suppression, mouse GM-CSF (mGM-CSF) and shRNA of mouse TGF-β2 (shmTGF-β2) genes were delivered together with MART1 via oncolytic adenovirus. MART1 plasmid was also used for antigen-priming. To compare the anti-tumor effect of oncolytic adenovirus expressing both mGM-CSF and shmTGF-β2 (Ad^GshT) with that of oncolytic adenovirus expressing mGM-CSF only (Ad^G), each virus was intratumorally injected into melanoma-bearing C57BL/6 mice. As a result, mice that received Ad^GshT showed delayed tumor growth than those that received Ad^G. Heterologous prime-boost immunization was combined with oncolytic Ad^GshT and MART1 expression to result in further delayed tumor growth. This regression is likely due to the following 4 combinations: MART1-derived mouse melanoma antigen-specific immune reaction, immune stimulation by mGM-CSF/shmTGF-β2, tumor growth inhibition by shmTGF-β2, and tumor cell-specific lysis via an oncolytic adenovirus. Immune activation was mainly induced by mature tumor-infiltrating dendritic cell (TIDC) and lowered regulatory T cells in tumor-infiltrating lymphocytes (TIL). Taken together, these findings demonstrate that human MART1 induces a mouse melanoma antigen-specific immune reaction. In addition, the results also indicate that combination therapy of MART1 plasmid, together with an oncolytic adenovirus expressing MART1, mGM-CSF, and shmTGF-β2, is a promising candidate for the treatment of malignant melanoma.

Enhanced Prophylactic and Therapeutic Effects of Polylysine-Modified Ara h 2 DNA Vaccine in a Mouse Model of Peanut Allergy

BACKGROUND

The prevalence of food allergy has been increasing, but treatment is very limited. DNA vaccination has been recognized as a promising method for the treatment of allergic diseases; however, poor immunogenicity has hindered its application.

METHODS

BALB/c mice were intradermally injected with plasmid DNA encoding the peanut protein Ara h 2 (pAra h 2) or pAra h 2 pretreated with poly-L- lysine (PLL) before or after sensitization with Ara h 2 protein. Ara h 2-specific antibodies were measured by ELISA. CD207+ dendritic cells (DCs) and Treg cells in draining lymph nodes were analyzed by flow cytometry after DNA immunization, and cytokine production in splenocytes was also analyzed.

RESULTS

In the prophylactic study, pretreatment with pAra h 2 or PLL-pAra h 2 resulted in lower levels of Ara h 2-specific IgG1, IgG2a, and IgE after sensitization with Ara h 2 protein, and mice in the PLL-pAra h 2 group had a significantly lower level of antibodies than those in the pAra h 2 group. In the treatment study, intradermal injection with pAra h 2 or PLL-pAra h 2 after Ara h 2 protein sensitization significantly decreased the level of Ara h 2-specific antibodies, and PLL- pAra h 2 had stronger effects than pAra h 2. There were increased numbers of CD207+ DCs and Treg cells in the mice receiving intradermal injection with PLL-pAra h 2, and splenocytes from PLL-pAra h 2-treated mice secreted increased levels of IFN-γ and IL-10.

CONCLUSIONS

Modification of pAra h 2 with PLL improved its prophylactic and therapeutic effects in peanut-allergic mice.

Construction and characterization of monoclonal antibodies against the extracellular domain of B-lymphocyte antigen CD20 using DNA immunization method

To date, several new anti-CD20 monoclonal antibodies (mAbs) have been developed for potential efficacies compared with familiar mAb rituximab. Despite the recent advances in development of anti-CD20 mAbs for the treatment of B cell malignancies, the efforts should be continued to develop novel antibodies with improved properties. However, the development of mAbs against CD20 as a multi-transmembrane protein is challenging due to the difficulty of providing a lipid environment that can maintain native epitopes. To overcome this limitation, we describe a simple and efficient DNA immunization strategy for the construction of a novel anti-CD20 mAb with improved anti-tumour properties. Using a DNA immunization strategy that includes intradermal (i.d.) immunization with naked plasmid DNA encoding the CD20 gene, we generated the hybridoma cell line D4, which secretes functional mAbs against an extracellular epitope of CD20. Immunocytochemistry analysis and a cell-based enzyme-linked immunosorbent assay using a Burkitt's lymphoma cell line showed that D4 mAbs are capable of binding to native extracellular epitopes of CD20. Moreover, the binding specificity of D4 mAbs was determined by western blot analysis. Cell proliferation was examined by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Apoptosis was detected by the annexin V/propidium iodide staining and dye exclusion assay. The results showed that D4 anti-CD20 mAbs produced by DNA immunization exhibit potent growth inhibitory activity and have superior direct B-cell cytotoxicity compared to rituximab. We propose that antibody-induced apoptosis is one of the mechanisms of cell growth inhibition. Taken together, the data reported here open the path to DNA-based immunization for generating pharmacologically active monoclonal antibodies against CD20. In addition, the data support future in vivo animal testing and subsequent procedures to produce a potential therapeutic mAb.

In vivo monitoring of transfected DNA, gene expression kinetics, and cellular immune responses in mice immunized with a human NIS gene-expressing plasmid

In assessing the effectiveness of DNA vaccines, it is important to monitor: (1) the kinetics of target gene expression in vivo; and (2) the movement of cells that become transfected with the plasmid DNA used in the immunization of a subject. In this study, we used, as a visual imaging marker, expression of the transfected human sodium/iodide symporter (hNIS) gene, which enhances intracellular radio-pertechnetate (TcO4-) accumulation. After intradermal (i.d.) and systemic injection of mice with pcDNA-hNIS and radioactive Technetium-99m (Tc-99m), respectively, whole-body images were obtained by nuclear scintigraphy. The migration of mice cells transfected with the hNIS gene was monitored over a 2-week period by gamma-radioactivity counting of isolated cell populations and was demonstrated in peripheral lymphoid tissues, especially in the draining lymph nodes (dLNs). Beginning at 24 h after DNA inoculation and continuing for the 2-week monitoring period, hNIS-expressing cells were observed specifically in the T-cell-rich zones of the paracortical area of the dLNs. Over the same time period, high levels of INF-γ-secreting CD8 T-cells were found in the dLNs of the pcDNA-hNIS immunized mice. Tumor growth was also significantly retarded in the mice that received hNIS DNA immunization followed by inoculation with CT26 colorectal adenocarcinoma cells that had been transfected with the rat NIS gene (rNIS), which is 93% homologous to the hNIS gene. In conclusion, mouse cells transfected with hNIS DNA after i.d. immunization were found to traffic to the dLNs, and hNIS gene expression in these cells continued for at least 2 weeks post immunization. Furthermore, sequential presentation of NIS DNA to T-cells by migratory antigen presenting cells could induce NIS DNA-specific Th1 immune responses and thus retard the growth of NIS-expressing tumors.

Gene-based neonatal immune priming potentiates a mucosal adenoviral vaccine encoding mycobacterial Ag85B

Tuberculosis remains a major public health hazard worldwide, with neonates and young infants potentially more susceptible to infection than adults. BCG, the only vaccine currently available, provides some protection against tuberculous meningitis in children but variable efficacy in adults, and is not safe to use in immune compromised individuals. A safe and effective vaccine that could be given early in life, and that could also potentiate subsequent booster immunization, would represent a significant advance. To test this proposition, we have generated gene-based vaccine vectors expressing Ag85B from Mycobacterium tuberculosis (Mtb) and designed experiments to test their immunogenicity and protective efficacy particularly when given in heterologous prime-boost combination, with the initial DNA vaccine component given soon after birth. Intradermal delivery of DNA vaccines elicited Th1-based immune responses against Ag85B in neonatal mice but did not protect them from subsequent aerosol challenge with virulent Mtb H37Rv. Recombinant adenovirus vectors encoding Ag85B, given via the intranasal route at six weeks of age, generated moderate immune responses and were poorly protective. However, neonatal DNA priming following by mucosal boosting with recombinant adenovirus generated strong immune responses, as evidenced by strong Ag85B-specific CD4+ and CD8+ T cell responses, both in the lung-associated lymph nodes and the spleen, by the quality of these responding cells (assessed by their capacity to secrete multiple antimicrobial factors), and by improved protection, as indicated by reduced bacterial burden in the lungs following pulmonary TB challenge. These results suggest that neonatal immunization with gene-based vaccines may create a favorable immunological environment that potentiates the pulmonary mucosal boosting effects of a subsequent heterologous vector vaccine encoding the same antigen. Our data indicate that immunization early in life with mycobacterial antigens in an appropriate vaccine setting can prime for protective immunity against Mtb.

DNA vaccines, electroporation and their applications in cancer treatment

Numerous animal studies and recent clinical studies have shown that electroporation-delivered DNA vaccines can elicit robust Ag-specific CTL responses and reduce disease severity. However, cancer antigens are generally poorly immunogenic, requiring special conditions for immune response induction. To date, many different approaches have been used to elicit Ag-specific CTL and anti-neoplastic responses to DNA vaccines against cancer. In vivo electroporation is one example, whereas others include DNA manipulation, xenogeneic antigen use, immune stimulatory molecule and immune response regulator application, DNA prime-boost immunization strategy use and different DNA delivery methods. These strategies likely increase the immunogenicity of cancer DNA vaccines, thereby contributing to cancer eradication. However, cancer cells are heterogeneous and might become CTL-resistant. Thus, understanding the CTL resistance mechanism(s) employed by cancer cells is critical to develop counter-measures for this immune escape. In this review, the use of electroporation as a DNA delivery method, the strategies used to enhance the immune responses, the cancer antigens that have been tested, and the escape mechanism(s) used by tumor cells are discussed, with a focus on the progress of clinical trials using cancer DNA vaccines.

Nanoparticulate mediated transcutaneous immunization: Myth or reality

Transcutaneous immunization (TCI) is a promising route of vaccine delivery through skin due to many well documented advantages. The main obstacle in TCI is the skin's top dead layer i.e. stratum corneum which is difficult to penetrate. Efficiently delivery of antigen to the immune competent cells of epidermis or dermis in TCI might elicit an effective immune response. In this review, skin immunology with a particular focus on potential of immunological active receptors in influencing adaptive immune responses is highlighted. The challenges with TCI and methods to improve it using different adjuvants, chemical and physical approaches, delivery systems, and combination of above methods to further improve immune response following skin application of antigen are elaborately discussed. Nanoparticulate vaccine delivery systems with reference to their applications in TCI are classified according to their chronological development. Conclusively, clinical translations of above methods are also briefly reviewed.

FROM THE CLINICAL EDITOR

Transcutaneous immunization has been investigated by many as a promising route of vaccination. In this comprehensive review article, the authors described and discussed the existing knowledge and difficulties in this approach. Furthermore, ways of improving transcutaneous delivery were also reviewed.

DNA vaccine for cancer immunotherapy

DNA vaccination has emerged as an attractive immunotherapeutic approach against cancer due to its simplicity, stability, and safety. Results from numerous clinical trials have demonstrated that DNA vaccines are well tolerated by patients and do not trigger major adverse effects. DNA vaccines are also very cost effective and can be administered repeatedly for long-term protection. Despite all the practical advantages, DNA vaccines face challenges in inducing potent antigen specific cellular immune responses as a result of immune tolerance against endogenous self-antigens in tumors. Strategies to enhance immunogenicity of DNA vaccines against self-antigens have been investigated including encoding of xenogeneic versions of antigens, fusion of antigens to molecules that activate T cells or trigger associative recognition, priming with DNA vectors followed by boosting with viral vector, and utilization of immunomodulatory molecules. This review will focus on discussing strategies that circumvent immune tolerance and provide updates on findings from recent clinical trials.

Suppressive Effects of Chronic Stress on Influenza Virus Protection after Vaccination with Plasmid DNA-Encoded Nucleoprotein

BACKGROUND

Influenza is a highly infectious and acute respiratory disease caused by an infection of the host respiratory tract mucosa by the influenza virus. The use of DNA vaccines that express conserved genes such as nucleoprotein (NP) represents a new method of vaccination against influenza. In this study, the effect of chronic stress on the efficiency of this type of vaccine has been evaluated in a mouse model.

METHODS

The NP DNA vaccine was administered intradermally 3 times on days 0, 3 and 6 to stressed and nonstressed male BALB/c mice. Two weeks after the last immunization, half of these mice were challenged with A/Puerto Rico/8/34 (PR8) influenza virus and were weighed for 12 days, and their mortality rate was assessed during this period. The cellular immune response of the other half of the mice was evaluated by cytotoxicity assay.

RESULTS

The results indicate a significant reduction in the cytotoxic T-lymphocyte response of stressed mice in comparison with unstressed mice. Also, the percentage of weight loss and mortality after the challenge in stressed mice was significantly increased compared to the other group.

CONCLUSION

These results indicate that the NP DNA vaccine is not able to induce any effective cytotoxic T-lymphocyte response against influenza virus in stressed mice and cannot induce protective immunity against influenza infection in this group of mice.

Applications of immunochemistry in human health: advances in vaccinology and antibody design (IUPAC Technical Report)

This report discusses the history and mechanisms of vaccination of humans as well as the engineering of therapeutic antibodies. Deeper understanding of the molecular interactions involved in both acquired and innate immunity is allowing sophistication in design of modified and even synthetic vaccines. Recombinant DNA technologies are facilitating development of DNA-based vaccines, for example, with the recognition that unmethylated CpG sequences in plasmid DNA will target Toll-like receptors on antigen-presenting cells. Formulations of DNA vaccines with increased immunogenicity include engineering into plasmids with “genetic adjuvant” capability, incorporation into polymeric or magnetic nanoparticles, and formulation with cationic polymers and other polymeric and non-polymeric coatings. Newer methods of delivery, such as particle bombardment, DNA tattooing, electroporation, and magnetic delivery, are also improving the effectiveness of DNA vaccines. RNA-based vaccines and reverse vaccinology based on gene sequencing and bioinformatic approaches are also considered. Structural vaccinology is an approach in which the detailed molecular structure of viral epitopes is used to design synthetic antigenic peptides. Virus-like particles are being designed for vaccine deliveries that are based on structures of viral capsid proteins and other synthetic lipopeptide building blocks. A new generation of adjuvants is being developed to further enhance immunogenicity, based on squalene and other oil–water emulsions, saponins, muramyl dipeptide, immunostimulatory oligonucleotides, Toll-like receptor ligands, and lymphotoxins. Finally, current trends in engineering of therapeutic antibodies including improvements of antigen-binding properties, pharmacokinetic and pharmaceutical properties, and reduction of immunogenicity are discussed. Taken together, understanding the chemistry of vaccine design, delivery and immunostimulation, and knowledge of the techniques of antibody design are allowing targeted development for the treatment of chronic disorders characterized by continuing activation of the immune system, such as autoimmune disorders, cancer, or allergies that have long been refractory to conventional approaches.

Combination of MIDGE-Th1 DNA vaccines with the cationic lipid SAINT-18: studies on formulation, biodistribution and vector clearance

We have previously shown that the combination of MIDGE-Th1 DNA vectors with the cationic lipid SAINT-18 increases the immune response to the encoded antigen in mice. Here, we report on experiments to further optimize and characterize this approach. We evaluated different formulations of MIDGE-Th1 vectors with SAINT-18 by assessing their influence on the transfection efficiency in cell culture and on the immune response in mice. We found that high amounts of SAINT-18 in formulations with a w/w ratio MIDGE Th1/SAINT-18 of 1:4.8 are beneficial for cell transfection in vitro. In contrast, the formulation of HBsAg-encoding MIDGE-Th1 DNA vectors with the lowest amount of SAINT-18 (w/w ratio MIDGE Th1/SAINT-18 of 1:0.5) resulted in the highest serum IgG1 and IgG2a levels after intradermal immunization of mice. Consequently, latter formulation was selected for a comparative biodistribution study in rats. Following intradermal administration of both naked and formulated MIDGE-Th1 DNA, the vectors localized primarily at the site of injection. Vector DNA levels decreased substantially over the two months duration of the study. When administered in combination with SAINT-18, the vectors were found in significantly higher amounts in draining lymph nodes in comparison to administration of naked MIDGE-Th1 DNA. We propose that the high immune responses induced by MIDGE-Th1/SAINT-18 lipoplexes are mediated by enhanced transfection of cells in vivo, resulting in stronger antigen expression and presentation. Importantly, the combination of MIDGE-Th1 vectors with SAINT-18 was well tolerated in mice and rats and is expected to be safe in human clinical applications.

Host responses in human skin after conventional intradermal injection or microneedle administration of virus-like-particle influenza vaccine

Miniaturized microneedle devices are being developed for painlessly targeting vaccines to the immune cell populations in skin. As skin immunization studies are generally restricted to animal models however, where skin architecture and immunity is greatly different to human, surprisingly little is known about the local human response to intradermal (ID) vaccines. Here surgically excised human skin is used to explore for the first time the complex molecular and cellular host responses to a candidate influenza vaccine comprising nanoparticulate virus-like-particles (VLPs), administered via conventional hypodermic injection or reduced scale microneedles. Responses at the molecular level are determined by microarray analysis (47,296 discrete transcripts) and validated by quantitative PCR (96 genes). Cellular response is probed through monitoring migration of dendritic cells in viable skin tissue. Gene expression mapping, ontological analysis, and qPCR reveal up-regulation of a host of genes responsible for key immunomodulatory processes and host viral response, including cell recruitment, activation, migration, and T cell interaction following both ID and microneedle injection of VLPs; the response from the microneedles being more subtle. Significant morphological and migratory changes to skin dendritic cells are also apparent following microneedle VLP delivery. This is the first study displaying the global, multifaceted immunological events that occur at the site of vaccine deposition in human skin and will subsequently influence the degree and nature of innate and adaptive immune responses. An increased understanding of the detailed similarities and differences in response against antigen administered via different delivery modalities will inform the development of improved vaccines and vaccine delivery systems.

Functional testing of an inhalable nanoparticle based influenza vaccine using a human precision cut lung slice technique

Annual outbreaks of influenza infections, caused by new influenza virus subtypes and high incidences of zoonosis, make seasonal influenza one of the most unpredictable and serious health threats worldwide. Currently available vaccines, though the main prevention strategy, can neither efficiently be adapted to new circulating virus subtypes nor provide high amounts to meet the global demand fast enough. New influenza vaccines quickly adapted to current virus strains are needed. In the present study we investigated the local toxicity and capacity of a new inhalable influenza vaccine to induce an antigen-specific recall response at the site of virus entry in human precision-cut lung slices (PCLS). This new vaccine combines recombinant H1N1 influenza hemagglutinin (HAC1), produced in tobacco plants, and a silica nanoparticle (NP)-based drug delivery system. We found no local cellular toxicity of the vaccine within applicable concentrations. However higher concentrations of NP (≥10³ µg/ml) dose-dependently decreased viability of human PCLS. Furthermore NP, not the protein, provoked a dose-dependent induction of TNF-α and IL-1β, indicating adjuvant properties of silica. In contrast, we found an antigen-specific induction of the T cell proliferation and differentiation cytokine, IL-2, compared to baseline level (152±49 pg/mg vs. 22±5 pg/mg), which could not be seen for the NP alone. Additionally, treatment with 10 µg/ml HAC1 caused a 6-times higher secretion of IFN-γ compared to baseline (602±307 pg/mg vs. 97±51 pg/mg). This antigen-induced IFN-γ secretion was further boosted by the adjuvant effect of silica NP for the formulated vaccine to a 12-fold increase (97±51 pg/mg vs. 1226±535 pg/mg). Thus we were able to show that the plant-produced vaccine induced an adequate innate immune response and re-activated an established antigen-specific T cell response within a non-toxic range in human PCLS at the site of virus entry.

DNA vaccines targeting human papillomavirus-associated diseases: progresses in animal and clinical studies

Human papillomavirus (HPV) infection is a major cause of cervical cancer and its precancerous diseases. Cervical cancer is the second deadliest cancer killer among women worldwide. Moreover, HPV is also known to be a causative agent of oral, pharyngeal, anal and genital cancer. Recent application of HPV structural protein (L1)-targeted prophylactic vaccines (Gardasil® and Cervarix®) is expected to reduce the incidence of HPV infection and cervical cancer, and possibly other HPV-associated cancers. However, the benefit of the prophylactic vaccines for treating HPV-infected patients is unlikely, underscoring the importance of developing therapeutic vaccines against HPV infection. In this regard, numerous types of therapeutic vaccine approaches targeting the HPV regulatory proteins, E6 and E7, have been tested for their efficacy in animals and clinically. In this communication, we review HPV vaccine types, in particular DNA vaccines, their designs and delivery by electroporation and their immunologic and antitumor efficacy in animals and humans, along with the basics of HPV and its pathogenesis.

Targeting the skin for microneedle delivery of influenza vaccine

Influenza infection represents a major socioeconomic burden worldwide. Skin represents a new target that has gained much attention in recent years for delivery of influenza vaccine as an alternative to the conventional intramuscular route of immunization. In this review we describe different microneedle vaccination approaches used in vivo, including metal and dissolving microneedle patches that have demonstrated promising results. Additionally we analyze the immunological basis for microneedle skin immunization and targeting of the skin's dense population of antigen presenting cells, their role, characterization, and function. Additionally we analyze the importance of inflammatory signaling in the skin after microneedle delivery.

Protective immune responses to biolistic DNA vaccination of Brugia malayi abundant larval transcript-2

Biolistic vaccination using gene gun is developed as a safer tool for delivery of DNA vaccines, a technique that combines high vaccine efficiency with lower antigen dosage and lower cost per vaccine dose. In this study, we compared the protective responses in mice after delivering the Brugia malayi abundant larval transcript-2 (BmALT-2) DNA vaccine using the conventional intradermal approach or with the needleless gene gun delivery approach. BmALT-2 is a leading vaccine candidate against B. malayi, a lymphatic filarial parasite of human. After optimizing the DNA dose and gene gun parameters for delivery into mouse skin, groups of mice were biolistically vaccinated with 5 μg of BmALT-2pVAX. Groups of mice vaccinated intradermally with 5 μg or 100 μg of BmALT-2pVAX was used for comparison of vaccine efficacy. Results demonstrated that gene gun vaccination with 5 μg of BmALT-2pVAX conferred significant protection against challenge infection that was comparable to the degree of protection conferred by intradermal vaccination with 100 μg of BmALT-2pVAX. This observation was further supported by an in vitro antibody dependent cellular cytotoxicity (ADCC) assay. Analysis of the immune response showed that the gene gun vaccination predominantly induced an IgG1 antibody response and significantly high Th2 cytokine response (IL-4) from spleen cells compared to intradermal BmALT-2 DNA delivery that induced predominantly an IgG2a and Th1 cytokine response (IFN-γ, IL-12 and TNF-α). These findings show that host protective responses could be achieved with 20 fold decrease in DNA dose using a gene gun and could prove to be an efficient delivery method in BmALT-2 DNA vaccination against lymphatic filariasis.

P3 mAb: An Immunogenic Anti-NeuGcGM3 Antibody with Unusual Immunoregulatory Properties

P3 is a murine IgM mAb that recognize N-glycosylated gangliosides, sulfatides, and antigens expressed in melanoma, breast, and lung human tumors. This antibody has the ability to trigger an IgG antibody response in the syngeneic BALB/c model, even when it is administered in the absence of adjuvant or carrier protein. The mechanism by which the P3 mAb, a self-immunoglobulin, induce this immune response in the absence of co-stimulatory or classical danger signals is still unknown. In the present paper we show that the high immunogenicity of P3 mAb depends not only on CD4 but also on CD8⁺ T cells, since the depletion of CD8⁺ or CD4⁺ T cells led to the loss of P3 mAb immunogenicity in the syngeneic model. Furthermore, the immunization with P3 mAb enhanced the recovery of the CD8⁺ T cell population in mice treated with an anti-CD8a antibody. Additionally, the immunization with P3 mAb restored the capacity of immunosuppressed mice to reject allogeneic tumors, a mechanism mediated by the action of CD8⁺ T cells. Finally, in mice with cyclophosphamide induced lymphopenia, the administration of P3 mAb accelerated the recovery of both CD4⁺ and CD8⁺ T cells. These results show new possibilities for B and CD8⁺ T cells interactions during the immune response elicited by a self-protein. Furthermore they point to P3 mAb as a potential interesting candidate for the treatment of immunosuppressed patients.

Shikonin enhances efficacy of a gene-based cancer vaccine via induction of RANTES

Background

Shikonin, a phytochemical purified from Lithospermum erythrorhizon, has been shown to confer diverse pharmacological activities, including accelerating granuloma formation, wound healing, anti-inflammation and others, and is explored for immune-modifier activities for vaccination in this study. Transdermal gene-based vaccine is an attractive approach for delivery of DNA transgenes encoding specific tumor antigens to host skin tissues. Skin dendritic cells (DCs), a potent antigen-presenting cell type, is known to play a critical role in transmitting and orchestrating tumor antigen-specific immunities against cancers. The present study hence employs these various components for experimentation.

Method

The mRNA and protein expression of RANTES were detected by RT-PCR and ELISA, respectively. The regional expression of RANTES and tissue damage in test skin were evaluated via immunohistochemistry assay. Fluorescein isothiocyanate sensitization assay was performed to trace the trafficking of DCs from the skin vaccination site to draining lymph nodes. Adjuvantic effect of shikonin on gene gun-delivered human gp100 (hgp100) DNA cancer vaccine was studied in a human gp100-transfected B16 (B16/hgp100) tumor model.

Results

Among various phytochemicals tested, shikonin induced the highest level of expression of RANTES in normal skin tissues. In comparison, mouse RANTES cDNA gene transfection induced a higher level of mRANTES expression for a longer period, but caused more extensive skin damage. Topical application of shikonin onto the immunization site before gene gun-mediated vaccination augmented the population of skin DCs migrating into the draining lymph nodes. A hgp100 cDNA gene vaccination regimen with shikonin pretreatment as an adjuvant in a B16/hgp100 tumor model increased cytotoxic T lymphocyte activities in splenocytes and lymph node cells on target tumor cells.

Conclusion

Together, our findings suggest that shikonin can effectively enhance anti-tumor potency of a gene-based cancer vaccine via the induction of RANTES expression at the skin immunization site.

Surface-engineered gold nanorods: promising DNA vaccine adjuvant for HIV-1 treatment

With the intense international response to the AIDS pandemic, HIV vaccines have been extensively investigated but have failed due to issues of safety or efficacy in humans. Adjuvants for HIV/AIDS vaccines are under intense research but a rational design approach is still lacking. Nanomaterials represent an obvious opportunity in this field due to their unique physicochemical properties. Gold nanostructures are being actively studied as a promising and versatile platform for biomedical application. Herein, we report novel surface-engineered gold nanorods (NRs) used as promising DNA vaccine adjuvant for HIV treatment. We have exploited the effects of surface chemistry on the adjuvant activity of the gold nanorod by placing three kinds of molecules, that is, cetyltrimethylammonium bromide (CTAB), poly(diallydimethylammonium chloride) (PDDAC), and polyethyleneimine (PEI) on the surface of the nanorod. These PDDAC- or PEI-modified Au NRs can significantly promote cellular and humoral immunity as well as T cell proliferation through activating antigen-presenting cells if compared to naked HIV-1 Env plasmid DNA treatment in vivo. These findings have shed light on the rational design of low-toxic nanomaterials as a versatile platform for vaccine nanoadjuvants/delivery systems.

Intradermal naked plasmid DNA immunization: mechanisms of action

Plasmid DNA is a promising vaccine modality that is regularly examined in prime-boost immunization regimens. Recent advances in skin immunity increased our understanding of the sophisticated cutaneous immune network, which revived scientific interest in delivering vaccines to the skin. Intradermal administration of plasmid DNA via needle injection is a simple and inexpensive procedure that exposes the plasmid and its encoded antigen to the dermal immune surveillance system. This triggers unique mechanisms for eliciting local and systemic immunity that can confer protection against pathogens and tumors. Understanding the mechanisms of intradermal plasmid DNA immunization is essential for enhancing and modulating its immunogenicity. With regard to vaccination, this is of greater importance as this routine injection technique is highly desirable for worldwide immunization. This article will focus on the current understanding of the mechanisms involved in antigen expression and presentation during primary and secondary syringe and needle intradermal plasmid DNA immunization.

Covalently stabilized trimethyl chitosan-hyaluronic acid nanoparticles for nasal and intradermal vaccination

The physical stability of polyelectrolyte nanocomplexes composed of trimethyl chitosan (TMC) and hyaluronic acid (HA) is limited in physiological conditions. This may minimize the favorable adjuvant effects associated with particulate systems for nasal and intradermal immunization. Therefore, covalently stabilized nanoparticles loaded with ovalbumin (OVA) were prepared with thiolated TMC and thiolated HA via ionic gelation followed by spontaneous disulfide formation after incubation at pH 7.4 and 37°C. Also, maleimide PEG was coupled to the remaining thiol-moieties on the particles to shield their surface charge. OVA-loaded TMC/HA nanoparticles had a size of around 250-350nm, a positive zeta potential and OVA loading efficiencies up to 60%. Reacting the thiolated particles with maleimide PEG resulted in a slight reduction of zeta potential (from +7 to +4mV) and a minor increase in particle size. Stabilized TMC-S-S-HA particles (PEGylated or not) showed superior stability in saline solutions compared to non-stabilized particles (composed of nonthiolated polymers) but readily disintegrated upon incubation in a saline buffer containing 10mM dithiothreitol. In both the nasal and intradermal immunization study, OVA loaded stabilized TMC-S-S-HA particles demonstrated superior immunogenicity compared to non-stabilized particles (indicated by higher IgG titers). Intranasal, PEGylation completely abolished the beneficial effects of stabilization and it induced no enhanced immune responses against OVA after intradermal administration. In conclusion, stabilization of the TMC/HA particulate system greatly enhances the immunogenicity of OVA in nasal and intradermal vaccination.

Serological memory and long-term protection to novel H1N1 influenza virus after skin vaccination

BACKGROUND

A major goal in influenza vaccine development is induction of serological memory and cellular responses to confer long-term protection and limit virus spread after infection. Here, we investigate induction of long-lived immunity against the 2009 H1N1 virus after skin vaccination.

METHODS

BALB/c mice received a single dose of 5 μg inactivated A/California/04/09 virus via coated metal microneedles (MN) applied to skin or via subcutaneous injection.

RESULTS

MN or subcutaneous vaccination elicited similar serum IgG and hemagglutination inhibition titers and 100% protection against lethal viral challenge 6 weeks after vaccination. Six months after vaccination, the subcutaneous group exhibited a 60% decrease in functional antibody titers and extensive lung inflammation after challenge with 10 × LD(50) of homologous virus. In contrast, the MN group maintained high functional antibody titers and IFN-γ levels, inhibition of viral replication, and no signs of lung inflammation after challenge. MN vaccination conferred complete protection against lethal challenge, whereas subcutaneous vaccination induced only partial protection. These findings were further supported by high numbers of bone marrow plasma cells and spleen antibody-secreting cells detected in the MN group.

CONCLUSIONS

A single skin vaccination with MN induced potent long-lived immunity and improved protection against the 2009 H1N1 influenza virus, compared with subcutaneous injection.

Induction of immune responses in ducks with a DNA vaccine encoding duck plague virus glycoprotein C

Background

A DNA vaccine expressing glycoprotein C (gC) of duck plague virus (DPV) was evaluated for inducing immunity in ducks. The plasmid encoding gC of DPV was administered via intramuscular (IM) injection and gene gun bombardment.

Results

After immunization by both routes virus-specific serum antibody and T-cell responses developed. Vaccination of ducks by IM injection induced a stronger humoral, but weaker cell-mediated immune response. In contrast, a better cell-mediated immune response was achieved by using a gene gun to deliver DNA-coated gold beads to the epidermis with as little as 6 μg of DNA.

Conclusions

This demonstrated that both routes of DNA inoculation can be used for eliciting virus-specific immune responses. Although DNA vaccine containing DPV gC is effective in both intramuscular injection and gene gun bombardment, the latter could induce significantly higher cell-mediated responses against DPV.

The virus-induced signaling adaptor molecule enhances DNA-raised immune protection against H5N1 influenza virus infection in mice

As an adaptor molecule in the retinoic acid-inducible gene-I (RIG-I) signaling pathway, the virus-induced signaling adaptor (VISA) molecule activates NF-κB and IRF3 and thereby leads to the production of type I interferons (IFNs). To explore the potential of VISA as a genetic adjuvant for DNA vaccines, a eukaryotic expression plasmid, pVISA, was generated by cloning the VISA gene into the pVAX1vector. For comparison, the pTRIF plasmid was similarly constructed, encoding the known genetic adjuvant TRIF (TIR-domain-containing adapter-inducing interferon-β), an adapter in the Toll-like receptor (TLR) signaling pathway. Mice were immunized with the chimeric DNA vaccine pHA/NP(147-155), which encodes the HA (hemagglutinin) fused with NP (nucleoprotein) CTL epitope (NP(147-155)) of H5N1 influenza virus, either alone or in combination with pVISA or pTRIF. Antigen-specific immune responses were examined in immunized mice. Our results demonstrate that co-immunization of the pHA/NP(147-155) plasmid with the VISA adjuvant augmented DNA-raised cellular immune responses and provided protection against H5N1 influenza virus challenge in mice. In addition, our data suggest that VISA acts as a stronger adjuvant for DNA immunization than TRIF. We conclude that co-inoculation with a vector expressing the adaptor molecule VISA enhanced the protective immunity against H5N1 infection induced by pHA/NP(147-155) and that VISA could be developed as a novel genetic adjuvant for DNA vaccines.

Microneedle-based transcutaneous immunisation in mice with N-trimethyl chitosan adjuvanted diphtheria toxoid formulations

Purpose

The purpose of this study was to gain insight into the delivery and immunogenicity of N-trimethyl chitosan (TMC) adjuvanted diphtheria toxoid (DT) formulations applied transcutaneously with microneedles.

Methods

Mice were vaccinated with DT-loaded TMC nanoparticles, a solution of TMC and DT (TMC/DT) or DT alone. The formulations were applied onto the skin before or after microneedle treatment with two different 300-µm-long microneedle arrays and also injected intradermally (ID). As a positive control, alum-adjuvanted DT (DT-alum) was injected subcutaneously (SC). Ex vivo confocal microscopy studies were performed with rhodamine-labelled TMC.

Results

Independent of the microneedle array used and the sequence of microneedle treatment and vaccine application, transcutaneous immunisation with the TMC/DT mixture elicited 8-fold higher IgG titres compared to the TMC nanoparticles or DT solution. The toxin-neutralising antibody titres from this group were similar to those elicited by SC DT-alum. After ID immunisation, both TMC-containing formulations induced enhanced titres compared to a DT solution. Confocal microscopy studies revealed that transport of the TMC nanoparticles across the microneedle conduits was limited compared to a TMC solution.

Conclusions

In conclusion, TMC has an adjuvant function in transcutaneous immunisation with microneedles, but only if applied in a solution.

Electronic Supplementary Material

The online version of this article (doi:10.1007/s11095-010-0182-y) contains supplementary material, which is available to authorized users.

Induction of Specific CD8 T Cells against Intracellular Bacteria by CD8 T-Cell-Oriented Immunization Approaches

For protection against intracellular bacteria such as Mycobacterium tuberculosis and Listeria monocytogenes, the cellular arm of adaptive immunity is necessary. A variety of immunization methods have been evaluated and are reported to induce specific CD8⁺ T cells against intracellular bacterial infection. Modified BCG vaccines have been examined to enhance CD8⁺ T-cell responses. Naked DNA vaccination is a promising strategy to induce CD8⁺ T cells. In addition to this strategy, live attenuated intracellular bacteria such as Shigella, Salmonella, and Listeria have been utilized as carriers of DNA vaccines in animal models. Vaccination with dendritic cells pulsed with antigenic peptides or the cells introduced antigen genes by virus vectors such as retroviruses is also a powerful strategy. Furthermore, vaccination with recombinant lentivirus has been attempted to induce specific CD8⁺ T cells. Combinations of these strategies (prime-boost immunization) have been studied for the efficient induction of intracellular bacteria-specific CD8⁺ T cells.

DNA vaccines: developing new strategies against cancer

Due to their rapid and widespread development, DNA vaccines have entered into a variety of human clinical trials for vaccines against various diseases including cancer. Evidence that DNA vaccines are well tolerated and have an excellent safety profile proved to be of advantage as many clinical trials combines the first phase with the second, saving both time and money. It is clear from the results obtained in clinical trials that such DNA vaccines require much improvement in antigen expression and delivery methods to make them sufficiently effective in the clinic. Similarly, it is clear that additional strategies are required to activate effective immunity against poorly immunogenic tumor antigens. Engineering vaccine design for manipulating antigen presentation and processing pathways is one of the most important aspects that can be easily handled in the DNA vaccine technology. Several approaches have been investigated including DNA vaccine engineering, co-delivery of immunomodulatory molecules, safe routes of administration, prime-boost regimen and strategies to break the immunosuppressive networks mechanisms adopted by malignant cells to prevent immune cell function. Combined or single strategies to enhance the efficacy and immunogenicity of DNA vaccines are applied in completed and ongoing clinical trials, where the safety and tolerability of the DNA platform are substantiated. In this review on DNA vaccines, salient aspects on this topic going from basic research to the clinic are evaluated. Some representative DNA cancer vaccine studies are also discussed.

Single-chain HLA-A2 MHC trimers that incorporate an immundominant peptide elicit protective T cell immunity against lethal West Nile virus infection

The generation of a robust CD8(+) T cell response is an ongoing challenge for the development of DNA vaccines. One problem encountered with classical DNA plasmid immunization is that peptides produced are noncovalently and transiently associated with MHC class I molecules and thus may not durably stimulate CD8(+) T cell responses. To address this and enhance the expression and presentation of the antigenic peptide/MHC complexes, we generated single-chain trimers (SCTs) composed of a single polypeptide chain with a linear composition of antigenic peptide, beta(2)-microglobulin, and H chain connected by flexible linkers. In this study, we test whether the preassembled nature of the SCT makes them effective for eliciting protective CD8(+) T cell responses against pathogens. A DNA plasmid was constructed encoding an SCT incorporating the human MHC class I molecule HLA-A2 and the immunodominant peptide SVG9 derived from the envelope protein of West Nile virus (WNV). HLA-A2 transgenic mice vaccinated with the DNA encoding the SVG9/HLA-A2 SCT generated a robust epitope-specific CD8(+) T cell response and showed enhanced survival rate and lower viral burden in the brain after lethal WNV challenge. Inclusion of a CD4(+) Th cell epitope within the SCT did not increase the frequency of SVG9-specific CD8(+) T cells, but did enhance protection against WNV challenge. Overall, these findings demonstrate that the SCT platform can induce protective CD8(+) T cell responses against lethal virus infection and may be paired with immunogens that elicit robust neutralizing Ab responses to generate vaccines that optimally activate all facets of adaptive immunity.

Recombinant DNA and Protein Vaccines for Foot-and-mouth Disease Induce Humoral and Cellular Immune Responses in Mice

Background

Foot-and-mouth disease virus (FMDV) is a small single-stranded RNA virus which belongs to the family Picornaviridae, genus Apthovirus. It is a principal cause of FMD which is highly contagious in livestock. In a wild type virus infection, infected animals usually elicit antibodies against structural and non-structural protein of FMDV. A structural protein, VP1, is involved in neutralization of virus particle, and has both B and T cell epitopes. A RNA-dependent RNA polymerase, 3D, is highly conserved among other serotypes and strongly immunogenic, therefore, we selected VP1 and 3D as vaccine targets.

Methods

VP1 and 3D genes were codon-optimized to enhance protein expression level and cloned into mammalian expression vector. To produce recombinant protein, VP1 and 3D genes were also cloned into pET vector. The VP1 and 3D DNA or proteins were co-immunized into 5 weeks old BALB/C mice.

Results

Antigen-specific serum antibody (Ab) responses were detected by Ab ELISA. Cellular immune response against VP1 and 3D was confirmed by ELISpot assay.

Conclusion

The results showed that all DNA- and protein-immunized groups induced cellular immune responses, suggesting that both DNA and recombinant protein vaccine administration efficiently induced Ag-specific humoral and cellular immune responses.