DNA-based Vaccines Research Articles

A novel formulation of Mtb72F DNA vaccine for immunization against tuberculosis.

Objective(s): Mycobacterium tuberculosis (M. tuberculosis), an intracellular pathogen, causes 1.5 million deaths globally. Bacilli Calmette-Guérin (BCG) is commonly administered to protect people against M. tuberculosis infection; however, there are some obstacles with this first-generation vaccine. DNA vaccines, the third generation vaccines, can induce cellular immune responses for tuberculosis (TB) protection. In this study, optimized DNA vaccine (pcDNA3.1-Mtb72F) entrapped in poly (lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) was used to achieve higher immunogenicity. Materials and Methods:Plasmid Mtb72F was formulated in PLGA NPs using double emulsion method in the presence of TB10.4 and/or CpG as an adjuvant. Female BALB/c mice were immunized either with NP-encapsulated Mtb72F or naked Mtb72F with or without each adjuvant, using the BCG-prime DNA boost regimen. Results:These NPs were approximately 250 nm in diameter and the nucleic acid and protein encapsulation efficiency were 80% and 25%, respectively. The NPs smaller than 200 nm are able to promote cellular rather than humoral responses. The immunization with the formulation consisting of Mtb72F DNA vaccine and TB10.4 entrapped in PLGA NPs showed significant immunogenicity and induced predominantly interferon-ɣ (IFN-ɣ) production and higher INF-ɣ/interleukin-4 (IL-4) ratio in the cultured spleen cells supernatant. Conclusion:PLGA NPs loaded with Mtb72F DNA-based vaccine with TB10.4 could be considered as a promising candidate for vaccination against TB. These results represent an excellent initial step toward development of novel vaccine for TB protection.

SARS-CoV-2 Infection and the Liver.

A novel strain of coronoviridae (SARS-CoV-2) was reported in Wuhan China in December 2019. Initially, infection presented with a broad spectrum of symptoms which typically included muscle aches, fever, dry cough, and shortness of breath. SARS-CoV-2 enters cells via ACE2 receptors which are abundant throughout the respiratory tract. However, there is evidence that these receptors are abundant throughout the body, and just as abundant in cholangiocytes as alveolar cells, posing the question of possible direct liver injury. While liver enzymes and function tests do seem to be deranged in some patients, it is questionable if the injury is due to direct viral damage, drug-induced liver injury, hypoxia, or microthromboses. Likely, the injury is multifactoral, and management of infected patients with pre-existing liver disease should be taken into consideration. Ultimately, a vaccine is needed to aid in reducing cases of SARS-CoV-2 and providing immunity to the general population. However, while considering the types of vaccines available, safety concerns, particularly of RNA- or DNA-based vaccines, need to be addressed.

Immunogenicity of a DNA vaccine candidate for COVID-19

The coronavirus family member, SARS-CoV-2 has been identified as the causal agent for the pandemic viral pneumonia disease, COVID-19. At this time, no vaccine is available to control further dissemination of the disease. We have previously engineered a synthetic DNA vaccine targeting the MERS coronavirus Spike (S) protein, the major surface antigen of coronaviruses, which is currently in clinical study. Here we build on this prior experience to generate a synthetic DNA-based vaccine candidate targeting SARS-CoV-2 S protein. The engineered construct, INO-4800, results in robust expression of the S protein in vitro. Following immunization of mice and guinea pigs with INO-4800 we measure antigen-specific T cell responses, functional antibodies which neutralize the SARS-CoV-2 infection and block Spike protein binding to the ACE2 receptor, and biodistribution of SARS-CoV-2 targeting antibodies to the lungs. This preliminary dataset identifies INO-4800 as a potential COVID-19 vaccine candidate, supporting further translational study.

A Phase 1 Trial Assessing the Safety and Tolerability of a Therapeutic DNA Vaccination Against HPV16 and HPV18 E6/E7 Oncogenes After Chemoradiation for Cervical Cancer

This study assessed the safety and tolerability of therapeutic immunization against the human papillomavirus (HPV) viral oncoproteins E6 and E7 in patients with cervical cancer after chemoradiation. MEDI0457 (INO-3112) is a DNA-based vaccine targeting E6 and E7 of HPV-16/18 that is coinjected with an IL-12 plasmid followed by electroporation with the CELLECTRA 5P device. At 2 to 4 weeks after chemoradiation, patients with newly diagnosed stage IB1-IVA (cohort 1) or persistent/recurrent (cohort 2) cervical cancers were treated with 4 immunizations of MEDI0457 every 4 weeks. The primary endpoints were incidence of adverse events and injection site reactions. Immune responses against HPV antigens were measured by ELISpot for interferon-γ (IFNγ), enzyme-linked immunosorbent assay for antibody responses and multiplexed immunofluorescence for immune cells in cervical biopsy specimens. Ten patients (cohort 1, n = 7; cohort 2, n = 3) with HPV16 (n = 7) or HPV18 (n = 3) cervical cancers received MEDI0457 after chemoradiation. Treatment-related adverse events were all grade 1, primarily related to the injection site. Eight of 10 patients had detectable cellular or humoral immune responses against HPV antigens after chemoradiation and vaccination: 6 of 10 patients generated anti-HPV antibody responses and 6 of 10 patients generated IFNγ-producing T cell responses. At the completion of chemoradiation and vaccination, cervical biopsy specimens had detectable CD8+ T cells and decreased PD-1+CD8+, PD-L1+CD8+, and PD-L1+CD68+ subpopulations. All patients cleared detectable HPV DNA in cervical biopsies by completion of chemoradiation and vaccination. Adjuvant MEDI0457 is safe and well tolerated after chemoradiation for locally advanced or recurrent cervical cancers, supporting further investigation into combining tumor-specific vaccines with radiation therapy.

Biotech firms to tackle coronavirus

A newly discovered coronavirus that emerged in Wuhan City, China, has sickened at least 570 people and killed 17 as of Jan. 23. The US Centers for Disease Control and Prevention (CDC) announced the first case of the virus in the US on Jan. 21. In the following days, several biotech companies, quick to see opportunity for both business and attention, announced plans to tackle the virus. Gaithersburg, Maryland–based Novavax said it would attempt to make a vaccine for the virus, which is being called 2019-nCoV. Novavax’s stock rose 70% within a day of the news. The company followed up by announcing plans to raise $100 million in a public sale of its stock. Inovio Pharmaceuticals, which develops DNA-based vaccines, announced a $9 million grant from the Coalition for Epidemic Preparedness Innovations (CEPI) to design and test a vaccine for 2019-nCoV. The company has experience designing experimental vaccines for Ebola

Modulation of Vaccine-Induced HIV-1-Specific Immune Responses by Co-Electroporation of PD-L1 Encoding DNA.

The importance of a balanced TH1/TH2 humoral immune response against the HIV-1 envelope protein (Env) for antibody-mediated HIV-1 control is increasingly recognized. However, there is no defined vaccination strategy to raise it. Since immune checkpoints are involved in the induction of adoptive immunity and their inhibitors (monoclonal antibodies) are licensed for cancer therapy, we investigated the effect of checkpoint blockade after HIV-1 genetic vaccination on enhancement and modulation of antiviral antibody responses. By intraperitoneal administration of checkpoint antibodies in mice we observed an induction of anti-drug antibodies which may interfere with immunomodulation by checkpoint inhibitors. Therefore, we blocked immune checkpoints locally by co-electroporation of DNA vaccines encoding the active soluble ectodomains of programmed cell death protein-1 (PD-1) or its ligand (PD-L1), respectively. Plasmid-encoded immune checkpoints did not elicit a detectable antibody response, suggesting no interference with their immunomodulatory effects. Co-electroporation of a HIV-1 DNA vaccine formulation with soluble PD-L1 ectodomain increased HIV-1 Env-specific TH1 CD4 T cell and IgG2a antibody responses. The overall antibody response was hereby shifted towards a more TH1/TH2 balanced subtype pattern. These findings indicate that co-electroporation of soluble checkpoint ectodomains together with DNA-based vaccines has modulatory effects on vaccine-induced immune responses that could improve vaccine efficacies.

A Novel Formulation Strategy to Deliver Combined DNA and VLP Based HPV Vaccine.

Human papillomaviruses (HPV) are small, double-stranded DNA viruses that cause cervical cancer, the second most lethal cancer among women in the world. Currently, two vaccines are on the market for preventing HPV-caused cervical cancers and warts. Both are virus-like particle (VLP)-based vaccines. However, these vaccines have limitations; they are costly, have an invasive route of administration, require trained personnel to administer, need cold chain storage to preserve them, and most of all, they are preventive vaccines that do not have curative effects. Therefore, it is necessary to develop therapeutic HPV vaccines to facilitate the control of HPV-associated malignancies and to address all these issues. Recently there are DNA vaccines under investigation to prevent HPV. In general, DNA-based vaccines are better than or an excellent alternative to traditional vaccines since they can closely mimic live infections and can induce both antibody and cell-mediated immune responses. DNA vaccines involve the delivery of plasmid DNA (pDNA) which encodes the specific antigens. DNA vaccines have potential to be effective therapeutic tools against HPV infections. Combining the VLP-based and DNA-based vaccines can be highly effective as they can complement each other. VLP vaccines are more prone to mucosal immunity whereas DNA vaccines are more towards systemic immunity. In this article, we discuss an optimal formulation that will contain both type of vaccines, preventive and therapeutic. A film dosage form can be a good option which can be administered in buccal or sublingual routes for systemic action or in the vaginal area for local action to treat cervical cancer and to protect from future infection. Multiple vaccines in native form or in particulate form can be incorporated in film dosage forms. The film dosage form of vaccines can elicit both antibody-mediated (preventative) and cell-mediated (therapeutic) mechanisms. Film dosage forms are feasible to prepare for vaccine administration in the mouth cavity, GI tract, and vagina.

Anti-Leishmanial Vaccines: Assumptions, Approaches, and Annulments.

Leishmaniasis is a neglected protozoan parasitic disease that occurs in 88 countries but a vaccine is unavailable. Vaccination with live, killed, attenuated (physically or genetically) Leishmania have met with limited success, while peptide-, protein-, or DNA-based vaccines showed promise only in animal models. Here, we critically assess several technical issues in vaccination and expectation of a host-protective immune response. Several studies showed that antigen presentation during priming and triggering of the same cells in infected condition are not comparable. Altered proteolytic processing, antigen presentation, protease-susceptible sites, and intracellular expression of pathogenic proteins during Leishmania infection may vary dominant epitope selection, MHC-II/peptide affinity, and may deter the reactivation of desired antigen-specific T cells generated during priming. The robustness of the memory T cells and their functions remains a concern. Presentation of the antigens by Leishmania-infected macrophages to antigen-specific memory T cells may lead to change in the T cells’ functional phenotype or anergy or apoptosis. Although cells may be activated, the peptides generated during infection may be different and cross-reactive to the priming peptides. Such altered peptide ligands may lead to suppression of otherwise active antigen-specific T cells. We critically assess these different immunological issues that led to the non-availability of a vaccine for human use.

Guest Editorial

Guest Editorial

Characterization of jet injection efficiency with mouse cadavers

Needle-free drug delivery is highly sought after for reduction in sharps waste, prevention of needle-stick injuries, and potential for improved drug dispersion and uptake. Whilst there is a wealth of literature on the array of different delivery methods, jet injection is proposed as the sole candidate for delivery of viscous fluids, which is especially relevant with the advent of DNA-based vaccines. The focus of this study was therefore to assess the role of viscosity and jet configuration (i.e. stand-off relative to the skin) upon injection efficiency for a fixed spring-loaded system (Bioject ID Pen). We performed this assessment in the context of mouse cadavers and found that the dominant factor in determining success rates was the time from euthanasia, which was taken as a proxy for the stiffness of the underlying tissue. For overall injection efficiency, ANOVA tests indicated that stiffness was highly significant (P < < 0.001), stand-off was moderately significant (P < 0.1), and viscosity was insignificant. In contrast, both viscosity and standoff were found to be significant (P < 0.01) when evaluating the percentage delivered intradermally. Using high-resolution micro-computed tomography (μ-CT), we also determined the depth and overall dispersion pattern immediately after injection.

IL17 depletion enhances the DNA vaccine efficacy in pancreatic ductal adenocarcinoma treatment

Abstract Pancreatic ductal adenocarcinoma (PDA) remains one of the most aggressive cancer with a 5-year survival rate of ~8%. PDA is considered an “immunologically-cold” tumor because of the abundant desmoplastic immune-suppressive microenvironment and low presence of neo-antigens. Moreover, it is characterised by a complex inflammatory response in which the role of the IL17 and T helper-17 remain controversial. We have demonstrated that a DNA-based vaccination strategy targeting a PDA-associated antigen, namely alpha-enolase (ENO1), significantly prolongs survival in genetically engineered mice (GEM). We have also observed that the absence of IL17 strongly modified PDA microenvironment, improving CD8 T cell recruitment. Therefore, the aim of this study is to assess the role of IL17-targeting in combination with the DNA-vaccination. GEM crossed with IL17 knockout mice (GEM/IL17−/−) were vaccinated and monitored weekly to obtain a Kaplan-Meier survival curve. GEM vaccinated in absence of IL17 showed higher level of anti-ENO1 antibodies and IFNγ-secreting ENO1-specific T cells. The analysis of the tumor infiltrating cells revealed an increase of antigen-presenting cells and effector/memory T cells. To translate the experimental model into a clinical setting, mice orthotopically injected with PDA cells, were treated with anti-IL17 mAb in combination or not with ENO1-DNA vaccine. Only the combination elicited a significantly reduction in tumor growth that paralleled the induction of cytotoxic T cells not observed after ENO1-vaccine or anti-IL17 Ab alone. Overall, the depletion of IL17 opens new possibilities for combination to design more effective immunotherapeutic strategies to be associated with conventional one.

Bioproduction of a Therapeutic Vaccine Against Human Papillomavirus in Tomato Hairy Root Cultures

Human papillomavirus (HPV) tumor disease is a critical public health problem worldwide, especially in the developing countries. The recognized pathogenic function of E5, E6, and E7 oncoproteins offers the opportunity to devise therapeutic vaccines based on engineered recombinant proteins. The potential of plants to manufacture engineered compounds for pharmaceutical purposes, from small to complex protein molecules, allows the expression of HPV antigens and, possibly, the regulation of immune functions to develop very specific therapies as a reinforcement to available nonspecific therapies and preventive vaccination also in developed countries. Among plant-based expression formats, hairy root cultures are a robust platform combining the benefits of eukaryotic plant-based bioreactors, with those typical of cell cultures. In this work, to devise an experimental therapeutic vaccine against HPV, hairy root cultures were used to express a harmless form of the HPV type 16 E7 protein (E7*) fused to SAPKQ, a noncytotoxic form of the saporin protein from Saponaria officinalis, that we had shown to improve E7-specific cell-mediated responses as a fusion E7*-SAPKQ DNA vaccine. Hairy root clones expressing the E7*-SAPKQ candidate vaccine were obtained upon infection of leaf explants of Solanum lycopersicum using a recombinant plant expression vector. Yield was approximately 35.5 μg/g of fresh weight. Mouse immunization with vaccine-containing crude extracts was performed together with immunological and biological tests to investigate immune responses and anticancer activity, respectively. Animals were primed with either E7*-SAPKQ DNA-based vaccine or E7*-SAPKQ root extract-based vaccine and boosted with the same (homologous schedule) or with the other vaccine preparation (heterologous schedule) in the context of TC-1 experimental mouse model of HPV-associated tumor. All the formulations exhibited an immunological response associated to anticancer activity. In particular, DNA as prime and hairy root extract as boost demonstrated the highest efficacy. This work, based on the development of low-cost technologies, highlights the suitability of hairy root cultures as possible biofactories of therapeutic HPV vaccines and underlines the importance of the synergic combination of treatment modalities for future developments in this field.

Field Testing Integrated Interventions for Schistosomiasis Elimination in the People's Republic of China: Outcomes of a Multifactorial Cluster-Randomized Controlled Trial.

Despite significant progress, China faces the challenge of re-emerging schistosomiasis transmission in currently controlled areas due, in part, to the presence of a range of animal reservoirs, notably water buffalo and cattle, which can harbor Schistosoma japonicum infections. Environmental, ecological and social-demographic changes in China, shown to affect the distribution of oncomelanid snails, can also impact future schistosomiasis transmission. In light of their importance in the S. japonicum, lifecycle, vaccination has been proposed as a means to reduce the excretion of egg from cattle and buffalo, thereby interrupting transmission from these reservoir hosts to snails. A DNA-based vaccine (SjCTPI) our team developed showed encouraging efficacy against S. japonicum in Chinese water buffaloes. Here we report the results of a double-blind cluster randomized trial aimed at determining the impact of a combination of the SjCTPI bovine vaccine (given as a prime-boost regimen), human mass chemotherapy and snail control on the transmission of S. japonicum in 12 selected administrative villages around the Dongting Lake in Hunan province. The trial confirmed human praziquantel treatment is an effective intervention at the population level. Further, mollusciciding had an indirect ~50% efficacy in reducing human infection rates. Serology showed that the SjCTPI vaccine produced an effective antibody response in vaccinated bovines, resulting in a negative correlation with bovine egg counts observed at all post-vaccination time points. Despite these encouraging outcomes, the effect of the vaccine in preventing human infection was inconclusive. This was likely due to activities undertaken by the China National Schistosomiasis Control Program, notably the treatment, sacrifice or removal of bovines from trial villages, over which we had no control; as a result, the trial design was compromised, reducing power and contaminating outcome measures. This highlights the difficulties in undertaking field trials of this nature and magnitude, particularly over a long period, and emphasizes the importance of mathematical modeling in predicting the potential impact of control intervention measures. A transmission blocking vaccine targeting bovines for the prevention of S. japonicum with the required protective efficacy would be invaluable in tandem with other preventive intervention measures if the goal of eliminating schistosomiasis from China is to become a reality.

Toward DNA-Based T-Cell Mediated Vaccines to Target HIV-1 and Hepatitis C Virus: Approaches to Elicit Localized Immunity for Protection.

Human immunodeficiency virus (HIV)-1 and hepatitis C virus (HCV) are major contributors to the global disease burden with many experts recognizing the requirement of an effective vaccine to bring a durable end to these viral epidemics. The most promising vaccine candidates that have advanced into pre-clinical models and the clinic to eliminate or provide protection against these chronic viruses are viral vectors [e.g., recombinant cytomegalovirus, Adenovirus, and modified vaccinia Ankara (MVA)]. This raises the question, is there a need to develop DNA vaccines against HIV-1 and HCV? Since the initial study from Wolff and colleagues which showed that DNA represents a vector that can be used to express transgenes durably in vivo, DNA has been regularly evaluated as a vaccine vector albeit with limited success in large animal models and humans. However, several recent studies in Phase I-IIb trials showed that vaccination of patients with recombinant DNA represents a feasible therapeutic intervention to even cure cervical cancer, highlighting the potential of using DNA for human vaccinations. In this review, we will discuss the limitations and the strategies of using DNA as a vector to develop prophylactic T cell-mediated vaccines against HIV-1 and HCV. In particular, we focus on potential strategies exploiting DNA vectors to elicit protective localized CD8+ T cell immunity in the liver for HCV and in the cervicovaginal mucosa for HIV-1 as localized immunity will be an important, if not critical component, of an efficacious vaccine against these viral infections.

Humoral and cellular immunity against both ZIKV and poxvirus is elicited by a two-dose regimen using DNA and non-replicating vaccinia virus-based vaccine candidates

The Zika virus (ZIKV) and poxvirus infection are considered as public health emergencies, necessitating the development of effective vaccines. Here, we report novel recombinant DNA-based and non-replicating vaccinia virus (NTV)-based vaccine candidates that express the precursor membrane-envelope (prME) or envelope (E) glycoproteins of ZIKV. After immunization of BABL/c mice with the vaccines using a homologous protocol (DNA/DNA, NTV/NTV) or heterogeneous (DNA/NTV) protocol, a similar level of anti-E IgG and neutralizing antibodies (microneutralization test) were detected in the mice. However, a significantly higher level of E-specific T cell responses was elicited in mice when a heterogeneous prime-boost protocol was used (DNA/NTV) with either the DNA-based or NTV-based vaccines. Furthermore, neutralizing antibodies and a T cell immune response against the vaccinia virus (VV) were detected in mice that were subjected to the prime-boost protocol (DNA/NTV), whereas those subjected to a homologous NTV/NTV protocol had higher levels of anti-VV IgG and neutralizing antibodies. Lastly, a novel H-2d-restricted CD8 T-cell epitope, VRSYCYEASISDMAS, was identified in the ZIKV E protein. These data demonstrate proof of concept of a bivalent vaccine candidate against ZIKV and orthopoxvirus, and support the use of DNA-prME prime and NTV-E boost protocols to protect against ZIKV and orthopoxvirus infections.

Optimization of Chitosan-α-casein Nanoparticles for Improved Gene Delivery: Characterization, Stability, and Transfection Efficiency.

Among non-viral vectors, the cationic polymer chitosan has gained attention as a gene delivery system. We hypothesized that the addition of casein into the nanoparticle's structure would facilitate a proper gene transfer. The work herein presented aimed to optimize the production method of chitosan-casein nanoparticles (ChiCas NPs) and to test their ability as a gene delivery system. ChiCas NPs formulation optimization was carried out by analyzing several characteristics such as NP size, zeta potential, and chitosan and casein incorporation efficacy. The best formulation developed presented small and homogenous particle size (around 335nm) and positive zeta potential (≈ + 38mV), and showed to be stable for 34weeks both, at 4°C and 20°C. The particles were further used to entrap or to adsorb DNA and form NPs-DNA complexes. In vitro transfection studies, carried out in COS-7 cells, suggested a low transfection efficiency of the different NPs:DNA ratios tested, comparatively to the positive control. Nonetheless, we could observe that the complexes with larger sizes presented better transfection results than those with smaller diameters. To conclude, ChiCas NPs have great technological potential since the preparation process is very simple, and the DNA incorporation efficacy is very high and shows to be physically very stable. The NPs:DNA ratio still needs to be optimized with the aim of achieving better transfection results and being able to anticipate a high gene expression on DNA-based vaccination studies.

In SilicoDesigning a Novel Multi-epitope DNA Vaccine against Anti-apoptotic Proteins in Tumor Cells

Background:Cancer therapy has been known as one of the most important challenges in the world. Various therapeutic methods such as cancer immunotherapy are used to eradicate tumor cells. Vaccines have an important role among different cancer immunotherapeutic approaches. In the field of vaccine production, bioinformatics approach is considered as a useful tool to design multi-epitope cancer vaccines, mainly for selecting immunodominant Cytotoxic T Lymphocytes (CTL) and Helper T Lymphocytes (HTL) epitopes.Objective:Generally, to design efficient multi-epitope cancer vaccines, Tumor-Specific Antigens (TSA) are targeted. In the context of DNA-based cancer vaccines, they contain genes that code tumor antigens and are delivered to host by different methods.Methods:In this study, the anti-apoptotic proteins (BCL2, BCL-X, survivin) that are over-expressed in different tumor cells were selected for CTL and HTL epitopes prediction through different servers such as RANKPEP, CTLpred, and BCPREDS.Results:Three regions from BCL2 and one region from BCL-X were selected as CTL epitopes and two segments from survivin were defined as HTL epitopes. In addition, &amp;#946;-defensin was used as a proper adjuvant to enhance vaccine efficacy. The aforesaid segments were joined together by appropriate linkers, and some important properties of designed vaccine such as antigenicity, allergenicity and physicochemical characteristics were determined by various bioinformatics servers.Conclusion:Based on the bioinformatics results, the physicochemical and immunological features showed that the designed vaccine construct can be used as an efficient cancer vaccine after its efficacy was confirmed by in vitro and in vivo immunological assays.

A DNA Vaccine Encoding SA-4-1BBL Fused to HPV-16 E7 Antigen Has Prophylactic and Therapeutic Efficacy in a Cervical Cancer Mouse Model.

The SA-4-1BBL, an oligomeric novel form of the natural ligand for the 4-1BB co-stimulatory receptor of the tumor necrosis factor (TNF) superfamily, as a recombinant protein has potent pleiotropic effects on cells of innate, adaptive, and regulatory immunity with demonstrated therapeutic efficacy in several tumor models. However, the production of soluble form of SA-4-1BBL protein and quality control is time and resource intensive and face various issues pertinent to clinical development of biologics. The present study sought to take advantage of the simplicity and translatability of DNA-based vaccines for the production and delivery of SA-4-1BBL for cancer immune prevention and therapy. A chimeric HPV-16 E7 DNA vaccine (SP-SA-E7-4-1BBL) was constructed that contains the signal peptide (SP) of calreticulin (CRT), streptavidin (SA) domain of SA-4-1BBL, HPV-16 E7 double mutant gene, and the extracellular domain of mouse 4-1BBL. Immunization by gene gun with SP-SA-E7-4-1BBL induced greater prophylactic as well as therapeutic effects in C57BL/6 mice against TC-1 tumor model compared with immunization with E7wt, SP-SA-4-1BBL or reference-positive control CRT-E7wt. The therapeutic efficacy of the DNA vaccine was associated with increased frequency of E7-specific T cells producing interferon (IFN)-γ. Overall, our data suggest that this DNA-based vaccine strategy might represent a translational approach because it provides a simpler and versatile alternative to a subunit vaccine based on SA-4-1BBL and E7 proteins.

Liposome and polymer-based nanomaterials for vaccine applications

Nanoparticles (NPs) are effective and safe adjuvants for antigen delivery in modern vaccinology. Biodegradable nanomaterials with suitable properties are frequently applied for conjugation or loading with antigens; they protect the antigens from degradation in vivo. NPs are applied as effective delivery system to facilitate antigen uptake by antigen presenting cells (APCs) and especially dendritic cells (DCs) both in vitro and in vivo. Using nanoparticles to target DCs is an effective method to deliver antigens and potent immunomodulators. Uptake of NPs by DCs enhances the intracellular process of antigens and the antigen presentation pathway by MHC class I and II molecules to induce both CD4+ and CD8+ T-cell responses. Liposome and polymer-based NPs are now extensively applied as effective adjuvants or immunomodulators in several types of vaccines. In this review, the nanomaterials for vaccine application are focused intensively in poly(lactic-co-glycolic) acid (PLGA), dendrimers, liposomes, nanogels and micelles which are the targeted antigen delivery system, and present high potential as a promising future strategy for DNA-based, bacterial and viral vaccines. Further advances in nanotechnology and molecular immunology techniques will enhance the success of targeting and lead to the next generation of nano-delivery systems.

DNA Vaccine Targeting Gonadotropin-Releasing Hormone Receptor and Its Application in Animal Contraception

Overpopulation of free-roaming and wildlife animals negatively affects economy and public health in many parts of the world. Contraceptive vaccines are viewed as a valuable option for reducing numbers of unwanted animals. This study develops vaccines for potential use in animal contraception exploiting a DNA platform. Objectives of the study were to generate DNA constructs directed against gonadotropin-releasing hormone receptor (GnRHR), a crucial molecular player in animal reproduction, and characterize them for ability to promote immune responses and suppression of reproductive parameters in vivo. DNA constructs were created to encode for a recombinant protein composed of two domains: GnRHR, the target antigen, and ubiquitin (Ub), a support protein. Ub-GnRHR constructs administered intramuscularly or intradermally or containing different promoters were compared. CMV and EF1α promoters were shown to be superior to CAG. In fertility trials, mice immunized intradermally with Ub-GnRHR construct driven by EF1α had a significantly lower number of fetuses. Importantly, the impaired fertility was achieved with a single DNA immunization and without the use of adjuvants. The study demonstrated for the first time that targeting the GnRH receptor with DNA-based vaccines could be a viable option for animal contraception.