Electroporation enhances immune responses and protection induced by a bovine viral diarrhea virus DNA vaccine in newborn calves with maternal antibodies

Recombinant Subunit Vaccine Candidate against the Bovine Viral Diarrhea Virus

Multivalent live-attenuated or inactivated vaccines are often used to control the bovine viral diarrhea disease (BVD). Still, they retain inherent disadvantages and do not provide the expected protection. This study developed a new vaccine prototype, including the external segment of the E2 viral protein from five different subgenotypes selected after a massive screening. The E2 proteins of every subgenotype (1aE2, 1bE2, 1cE2, 1dE2, and 1eE2) were produced in mammalian cells and purified by IMAC. An equimolar mixture of E2 proteins formulated in an oil-in-water adjuvant made up the vaccine candidate, inducing a high humoral response at 50, 100, and 150 µg doses in sheep. A similar immune response was observed in bovines at 50 µg. The cellular response showed a significant increase in the transcript levels of relevant Th1 cytokines, while those corresponding to the Th2 cytokine IL-4 and the negative control were similar. High levels of neutralizing antibodies against the subgenotype BVDV1a demonstrated the effectiveness of our vaccine candidate, similar to that observed in the sera of animals vaccinated with the commercial vaccine. These results suggest that our vaccine prototype could become an effective recombinant vaccine against the BVD.

The combination of vaccines and adjuvants to prevent the occurrence of high incidence of infectious diseases in bovine

As the global population grows, the demand for beef and dairy products is also increasing. The cattle industry is facing tremendous pressures and challenges. The expanding cattle industry has led to an increased risk of disease in cattle. These diseases not only cause economic losses but also pose threats to public health and safety. Hence, ensuring the health of cattle is crucial. Vaccination is one of the most economical and effective methods of preventing bovine infectious diseases. However, there are fewer comprehensive reviews of bovine vaccines available. In addition, the variable nature of bovine infectious diseases will result in weakened or even ineffective immune protection from existing vaccines. This shows that it is crucial to improve overall awareness of bovine vaccines. Adjuvants, which are crucial constituents of vaccines, have a significant role in enhancing vaccine response. This review aims to present the latest advances in bovine vaccines mainly including types of bovine vaccines, current status of development of commonly used vaccines, and vaccine adjuvants. In addition, this review highlights the main challenges and outstanding problems of bovine vaccines and adjuvants in the field of research and applications. This review provides a theoretical and practical basis for the eradication of global bovine infectious diseases.

A DNA vaccine targeting VEE virus delivered by needle-free jet-injection protects macaques against aerosol challenge

We have previously shown that DNA vaccines expressing codon optimized alphavirus envelope glycoprotein genes protect both mice and nonhuman primates from viral challenge when delivered by particle-mediated epidermal delivery (PMED) or intramuscular (IM) electroporation (EP). Another technology with fewer logistical drawbacks is disposable syringe jet injection (DSJI) devices developed by PharmaJet, Inc. These needle-free jet injection systems are spring-powered and capable of delivering vaccines either IM or into the dermis (ID). Here, we evaluated the immunogenicity of our Venezuelan equine encephalitis virus (VEEV) DNA vaccine delivered by either the IM- or ID-DSJI devices in nonhuman primates. The protective efficacy was assessed following aerosol challenge. We found that a prime and single boost by either the IM or ID route resulted in humoral and cellular immune responses that provided significant protection against disease and viremia. Although the ID route utilized one-fifth the DNA dose used in the IM route of vaccination, and the measured humoral and cellular immune responses trended lower, the level of protection was high and performed as well as the IM route for several clinical endpoints.

Nucleoside-modified mRNA vaccination partially overcomes maternal antibody inhibition of de novo immune responses in mice

Maternal antibodies provide short-term protection to infants against many infections. However, they can inhibit de novo antibody responses in infants elicited by infections or vaccination, leading to increased long-term susceptibility to infectious diseases. Thus, there is a need to develop vaccines that are able to elicit protective immune responses in the presence of antigen-specific maternal antibodies. Here, we used a mouse model to demonstrate that influenza virus-specific maternal antibodies inhibited de novo antibody responses in mouse pups elicited by influenza virus infection or administration of conventional influenza vaccines. We found that a recently developed influenza vaccine, nucleoside-modified mRNA encapsulated in lipid nanoparticles (mRNA-LNP), partially overcame this inhibition by maternal antibodies. The mRNA-LNP influenza vaccine established long-lived germinal centers in the mouse pups and elicited stronger antibody responses than did a conventional influenza vaccine approved for use in humans. Vaccination with mRNA-LNP vaccines may offer a promising strategy for generating robust immune responses in infants in the presence of maternal antibodies.

Bovine herpesvirus glycoprotein D: a review of its structural characteristics and applications in vaccinology

The viral envelope glycoprotein D from bovine herpesviruses 1 and 5 (BoHV-1 and -5), two important pathogens of cattle, is a major component of the virion and plays a critical role in the pathogenesis of herpesviruses. Glycoprotein D is essential for virus penetration into permissive cells and thus is a major target for virus neutralizing antibodies during infection. In view of its role in the induction of protective immunity, gD has been tested in new vaccine development strategies against both viruses. Subunit, DNA and vectored vaccine candidates have been developed using this glycoprotein as the primary antigen, demonstrating that gD has the capacity to induce robust virus neutralizing antibodies and strong cell-mediated immune responses, as well as protection from clinical symptoms, in target species. This review highlights the structural and functional characteristics of BoHV-1, BoHV-5 and where appropriate, Human herpesvirus gD, as well as its role in viral entry and interactions with host cell receptors. Furthermore, the interactions of gD with the host immune system are discussed. Finally, the application of this glycoprotein in new vaccine design is reviewed, taking its structural and functional characteristics into consideration.

Electroporation mediated DNA vaccination directly to a mucosal surface results in improved immune responses

In vivo electroporation (EP) has been shown to be a highly efficient non-viral method for enhancing DNA vaccine delivery and immunogenicity, when the site of immunization is the skin or muscle of animals and humans. However, the route of entry for many microbial pathogens is via the mucosal surfaces of the human body. We have previously reported on minimally invasive, surface and contactless EP devices for enhanced DNA delivery to dermal tissue. Robust antibody responses were induced following vaccine delivery in several tested animal models using these devices. Here, we investigated extending the modality of the surface device to efficiently deliver DNA vaccines to mucosal tissue. Initially, we demonstrated reporter gene expression in the epithelial layer of buccal mucosa in a guinea pig model. There was minimal tissue damage in guinea pig mucosal tissue resulting from EP. Delivery of a DNA vaccine encoding influenza virus nucleoprotein (NP) of influenza H1N1 elicited robust and sustained systemic IgG antibody responses following EP-enhanced delivery in the mucosa. Upon further analysis, IgA antibody responses were detected in vaginal washes and sustained cellular immune responses were detected in animals immunized at the oral mucosa with the surface EP device. This data confirms that DNA delivery and EP targeting mucosal tissue directly results in both robust and sustainable humoral as well as cellular immune responses without tissue damage. These responses are seen both in the mucosa and systemically in the blood. Direct DNA vaccine delivery enhanced by EP in mucosa may have important clinical applications for delivery of prophylactic and therapeutic DNA vaccines against diseases such as HIV, HPV and pneumonia that enter at mucosal sites and require both cellular and humoral immune responses for protection.

A single electroporation delivery of a DNA vaccine containing the hemagglutinin gene of Asian H5N1 avian influenza virus generated a protective antibody response in chickens against a North American virus strain

Protection against the avian influenza (AI) H5N1 virus is suspected to be mainly conferred by the presence of antibodies directed against the hemagglutinin (HA) protein of the virus. A single electroporation delivery of 100 or 250 μg of a DNA vaccine construct, pCAG-HA, carrying the HA gene of strain A/Hanoi/30408/2005 (H5N1), in chickens led to the development of anti-HA antibody response in 16 of 17 immunized birds, as measured by a hemagglutination inhibition (HI) test, competitive enzyme-linked immunosorbent assay (cELISA), and an indirect ELISA. Birds vaccinated by electroporation (n = 11) were protected from experimental AI challenge with strain A/chicken/Pennsylvania/1370/1/1983 (H5N2) as judged by low viral load, absence of clinical symptoms, and absence of mortality (n = 11). In contrast, only two out of 10 birds vaccinated with the same vaccine dose (100 or 250 μg) but without electroporation developed antibodies. These birds showed high viral loads and significant morbidity and mortality after the challenge. Seroconversion was reduced in birds electroporated with a low vaccine dose (10 μg), but the antibody-positive birds were protected against virus challenge. Nonelectroporation delivery of a low-dose vaccine did not result in seroconversion, and the birds were as susceptible as those in the control groups that received the control pCAG vector. Electroporation delivery of the DNA vaccine led to enhanced antibody responses and to protection against the AI virus challenge. The HI test, cELISA, or indirect ELISA for anti-H5 antibodies might serve as a good predictor of the potency and efficacy of a DNA immunization strategy against AI in chickens.

Two doses of bovine viral diarrhea virus DNA vaccine delivered by electroporation induce long-term protective immune responses

Bovine viral diarrhea virus (BVDV) is a pathogen of major importance in cattle, so there is a need for new effective vaccines. DNA vaccines induce balanced immune responses and are relatively inexpensive and thus promising for both human and veterinary applications. In this study, newborn calves with maternal antibodies were vaccinated intramuscularly (i.m.) with a BVDV E2 DNA vaccine with the TriGrid Delivery System for i.m. delivery (TDS-IM). Two doses of this vaccine spaced 6 or 12 weeks apart were sufficient to induce significant virus-neutralizing antibody titers, numbers of activated T cells, and reduction in viral shedding and clinical presentations after BVDV-2 challenge. In contrast to the placebo-treated animals, the vaccinated calves did not lose any weight, which is an excellent indicator of the well-being of an animal and has a significant economic impact. Furthermore, the interval between the two vaccinations did not influence the magnitude of the immune responses or degree of clinical protection, and a third immunization was not necessary or beneficial. Since electroporation may enhance not only the magnitude but also the duration of immunity after DNA immunization, the interval between vaccination and challenge was extended in a second trial, which showed that two doses of this E2 DNA vaccine again significantly reduced clinical disease against BVDV for several months. These results are promising and support this technology for use against infectious diseases in cattle and large species, including humans, in general.

DNA vaccination partially protects against African swine fever virus lethal challenge in the absence of antibodies

The lack of available vaccines against African swine fever virus (ASFV) means that the evaluation of new immunization strategies is required. Here we show that fusion of the extracellular domain of the ASFV Hemagglutinin (sHA) to p54 and p30, two immunodominant structural viral antigens, exponentially improved both the humoral and the cellular responses induced in pigs after DNA immunization. However, immunization with the resulting plasmid (pCMV-sHAPQ) did not confer protection against lethal challenge with the virulent E75 ASFV-strain. Due to the fact that CD8⁺ T-cell responses are emerging as key components for ASFV protection, we designed a new plasmid construct, pCMV-UbsHAPQ, encoding the three viral determinants above mentioned (sHA, p54 and p30) fused to ubiquitin, aiming to improve Class I antigen presentation and to enhance the CTL responses induced. As expected, immunization with pCMV-UbsHAPQ induced specific T-cell responses in the absence of antibodies and, more important, protected a proportion of immunized-pigs from lethal challenge with ASFV. In contrast with control pigs, survivor animals showed a peak of CD8⁺ T-cells at day 3 post-infection, coinciding with the absence of viremia at this time point. Finally, an in silico prediction of CTL peptides has allowed the identification of two SLA I-restricted 9-mer peptides within the hemagglutinin of the virus, capable of in vitro stimulating the specific secretion of IFNγ when using PBMCs from survivor pigs. Our results confirm the relevance of T-cell responses in protection against ASF and open new expectations for the future development of more efficient recombinant vaccines against this disease.

Using monoclonal antibodies to stimulate antitumor cellular immunity

Monoclonal antibodies (mAbs) have an established role in current cancer therapy with seven approved for the treatment of a wide variety of tumors. The approved mAbs directly target tumor cells; however, it is becoming increasingly clear that as well as their direct effects, these mAbs can present antigens to the immune system. This stimulates long-lasting T-cell immunity, which may correlate with long-term survival. A more direct approach is to use mAbs to target antigens directly to antigen-presenting cells. One approach, ImmunoBody, which has just entered the clinic, stimulates antitumor immunity using mAbs genetically engineered to express tumor-specific T-cell epitopes. T cells not only respond via their T-cell receptors recognizing T-cell epitopes presented on MHC but are also influenced by stimulation of a wide variety of costimulatory molecules. mAbs targeting these molecules can also influence antitumor immunity. The main protagonist in this class of mAbs is ipilimumab, which has recently been shown to improve survival at 2 years in 23% of advanced melanoma patients. Combinations of mAbs targeting tumor antigens to activated antigen-presenting cells and mAbs targeting costimulatory receptors may provide effective therapy for a broad range of tumors.

The Importance of Animal Models in the Development of Vaccines

Efficient translation of basic vaccine research into clinical therapies greatly depends upon the availability of appropriate animal models. Testing novel vaccine candidates in animal models is a critical step in the development of modern vaccines. Animal models are being used to assess the quality and quantity of the immune response, to identify the optimal route of delivery and formulation, to determine protection from infection and disease transmission, and to evaluate the safety and toxicity of the vaccine formulation. Animal models help to make the translation from basic research to clinical application, and they often allow prediction of the vaccine potential, which helps in predicting the financial risks for vaccine manufacturers. Choosing an appropriate animal model has become increasingly important for the field, as each model has its own advantages and disadvantages. In this review, the criteria for selecting the right animal model, the advantages and disadvantages of various animal models, as well as the future needs for animal models are being discussed.

Genetic immunization with plasmid DNA mediated by electrotransfer

The concept of DNA immunization was first advanced in the early 1990s, but was not developed because of an initial lack of efficiency. Recent technical advances in plasmid design and gene delivery techniques have allowed renewed interest in the idea. Particularly, a better understanding of genetic immunization has led to construction of optimized plasmids and the use of efficient molecular adjuvants. The field also took great advantage of new delivery techniques such as electrotransfer. This is a simple physical technique consisting of injecting plasmid DNA into a target tissue and applying an electric field, allowing up to a thousandfold more expression of the transgene than naked DNA. DNA immunization mediated by electrotransfer is now effective in a variety of preclinical models against infectious or acquired diseases such as cancer or autoimmune diseases, and is making its way through the clinics in several ongoing phase I human clinical trials. This review will briefly describe genetic immunization mediated by electrotransfer and the main fields of application.

Modulation of immunogenicity and immunoprotection of mucosal vaccine against coxsackievirus B3 by optimizing the coadministration mode of lymphotactin adjuvant

Induction of potent mucosal immune response is a goal of current vaccine strategies against mucus-infectious pathogens such as Coxsackievirus B3 type (CVB3). We previously showed that administration of lymphotactin (LTN) as an adjuvant could enhance the specific immune responses against a mucosal gene vaccine, chitosan-pVP1, against CVB3. To optimize the coadministration mode of the mucosal adjuvant, we compared the mucosal immune responses induced by chitosan-DNA vaccine with different combinations of the target VP1 antigen gene and the adjuvant LTN gene. The two genes were either cloned in separate vectors or coexpressed as a fusion or bicistron protein in the same vector before encapsulation in chitosan nanoparticles. Four doses of various adjuvant-combined chitosan-DNA were intranasally administrated to mice before challenge with CVB3. The results indicated that chitosan-formulated pVP1-LTN fusion plasmid exhibited very weak improvement of CVB3-specific immune responses. Although the bicistronic coexpression of LTN with VP1 was expected to be powerful, this combination had enhanced effects on serum IgG and systemic T cell immune responses, but not on mucosal T cell immunity. Coimmunization with VP1 and LTN as separate chitosan-DNA formulation remarkably enhanced antibody and T cell immune responses both in systemic and mucosal immune compartments, leading to the most desirable preventive effect on viral myocarditis. Taken together, how the adjuvant is combined with the target antigen has a strong influence on the mucosal immune responses induced by mucosal DNA vaccines.