Attenuated Salmonella typhimurium delivering DNA vaccine encoding duck enteritis virus UL24 induced systemic and mucosal immune responses and conferred good protection against challenge

UL24 herpesvirus determinants of pathogenesis: Roles in virus-host interactions

Members of the UL24 herpesvirus gene family are determinants of pathogenesis. The gene is widely conserved across the Orthoherpesviridae family, also commonly referred to as Herpesviridae. In this review, the impact of UL24 homologs on pathogenesis as studied with different model systems is presented, as well as mechanistic aspects related to the different roles of UL24 proteins in virus-host cell interactions. The targeting of UL24 for the development of therapeutic applications is also discussed.

Recombinant Live-Attenuated Salmonella Vaccine for Veterinary Use

Vaccination is essential for maintaining animal health, with priority placed on safety and cost effectiveness in veterinary use. The development of recombinant live-attenuated Salmonella vaccines (RASVs) has enabled the construction of balanced lethal systems, ensuring the stability of plasmid vectors encoding protective antigens post-immunization. These vaccines are particularly suitable for production animals, providing long-term immunity against a range of bacterial, viral, and parasitic pathogens. This review summarizes the progress made in this field, with a focus on clinical trials demonstrating the efficacy and commercial potential of RASVs in veterinary medicine.

Duck CD40L as an adjuvant enhances systemic immune responses of avian flavivirus DNA vaccine

Under the dual pressure of emerging zoonoses and the difficulty in eliminating conventional zoonoses, the strategic management of bird diseases through vaccination represents a highly efficacious approach to disrupting the transmission of zoonotic pathogens to humans. Immunization with a DNA vaccine yielded limited protection against avian pathogen infection. To improve its immunogenicity, the extracellular domain of duck-derived CD40L (designated as dusCD40L) was employed as a bio-adjuvant. Our findings unequivocally established the evolutionary conservation of dusCD40L across avian species. Notably, dusCD40L exhibited a compelling capacity to elicit robust immune responses from both B and T lymphocytes. Furthermore, when employed as an adjuvant, dusCD40L demonstrated a remarkable capacity to significantly augment the titers of neutralizing antibodies and the production of IFNγ elicited by a DNA vaccine encoding the prM-E region of an avian flavivirus, namely, the Tembusu virus (TMUV). Moreover, dusCD40L could strengthen virus clearance of the prM-E DNA vaccine in ducks post-TMUV challenge. This research study presents a highly effective adjuvant for advancing the development of DNA vaccines targeting TMUV in avian hosts. Additionally, it underscores the pivotal role of duCD40L as a potent adjuvant in the context of vaccines designed to combat zoonotic infections in avian species.

Salmonella Infection in Poultry: A Review on the Pathogen and Control Strategies

Salmonella is the leading cause of food-borne zoonotic disease worldwide. Non-typhoidal Salmonella serotypes are the primary etiological agents associated with salmonellosis in poultry. Contaminated poultry eggs and meat products are the major sources of human Salmonella infection. Horizontal and vertical transmission are the primary routes of infection in chickens. The principal virulence genes linked to Salmonella pathogenesis in poultry are located in Salmonella pathogenicity islands 1 and 2 (SPI-1 and SPI-2). Cell-mediated and humoral immune responses are involved in the defense against Salmonella invasion in poultry. Vaccination of chickens and supplementation of feed additives like prebiotics, probiotics, postbiotics, synbiotics, and bacteriophages are currently being used to mitigate the Salmonella load in poultry. Despite the existence of various control measures, there is still a need for a broad, safe, and well-defined strategy that can confer long-term protection from Salmonella in poultry flocks. This review examines the current knowledge on the etiology, transmission, cell wall structure, nomenclature, pathogenesis, immune response, and efficacy of preventative approaches to Salmonella.

Mechanism of herpesvirus UL24 protein regulating viral immune escape and virulence

Herpesviruses have evolved a series of abilities involved in the process of host infection that are conducive to virus survival and adaptation to the host, such as immune escape, latent infection, and induction of programmed cell death for sustainable infection. The herpesvirus gene UL24 encodes a highly conserved core protein that plays an important role in effective viral infection. The UL24 protein can inhibit the innate immune response of the host by acting on multiple immune signaling pathways during virus infection, and it also plays a key role in the proliferation and pathogenicity of the virus in the later stage of infection. This article reviews the mechanism by which the UL24 protein mediates herpesvirus immune escape and its effects on viral proliferation and virulence by influencing syncytial formation, DNA damage and the cell cycle. Reviewing these studies will enhance our understanding of the pathogenesis of herpesvirus infection and provide evidence for new strategies to combat against viral infection.

Changes in the gut microbiota of NOD mice in response to an oral Salmonella-based vaccine against type 1 diabetes

We developed an oral Salmonella-based vaccine that prevents and reverses diabetes in non-obese diabetic (NOD) mice. Related to this, the gastrointestinal tract harbors a complex dynamic population of microorganisms, the gut microbiome, that influences host homeostasis and metabolism. Changes in the gut microbiome are associated with insulin dysfunction and type 1 diabetes (T1D). Oral administration of diabetic autoantigens as a vaccine can restore immune balance. However, it was not known if a Salmonella-based vaccine would impact the gut microbiome. We administered a Salmonella-based vaccine to prediabetic NOD mice. Changes in the gut microbiota and associated metabolome were assessed using next-generation sequencing and gas chromatography-mass spectrometry (GC-MS). The Salmonella-based vaccine did not cause significant changes in the gut microbiota composition immediately after vaccination although at 30 days post-vaccination changes were seen. Additionally, no changes were noted in the fecal mycobiome between vaccine- and control/vehicle-treated mice. Significant changes in metabolic pathways related to inflammation and proliferation were found after vaccine administration. The results from this study suggest that an oral Salmonella-based vaccine alters the gut microbiome and metabolome towards a more tolerant composition. These results support the use of orally administered Salmonella-based vaccines that induced tolerance after administration.

Simultaneous Protective Immune Responses of Ducks against Duck Plague and Fowl Cholera by Recombinant Duck Enteritis Virus Vector Expressing Pasteurella multocida OmpH Gene

Duck enteritis virus and Pasteurella multocida are major duck pathogens that induce duck plague and fowl cholera, respectively, in ducks and other waterfowl populations, leading to high levels of morbidity and mortality. Immunization with live attenuated DEV vaccine containing P. multocida outer membrane protein H (OmpH) can provide the most effective protection against these two infectious diseases in ducks. We have recently reported the construction of recombinant DEV expressing P. multocida ompH gene using the CRISPR/Cas9 gene editing strategy with the goal of using it as a bivalent vaccine that can simultaneously protect against both infections. Here we describe the findings of our investigation into the systemic immune responses, potency and clinical protection induced by the two recombinant DEV-ompH vaccine constructs, where one copy each of the ompH gene was inserted into the DEV genome at the UL55-LORF11 and UL44-44.5 intergenic regions, respectively. Our study demonstrated that the insertion of the ompH gene exerted no adverse effect on the DEV parental virus. Moreover, ducklings immunized with the rDEV-ompH-UL55 and rDEV-ompH-UL44 vaccines induced promising levels of P. multocida OmpH-specific as well as DEV-specific antibodies and were completely protected from both diseases. Analysis of the humoral and cellular immunity confirmed the immunogenicity of both recombinant vaccines, which provided strong immune responses against DEV and P. multocida. This study not only provides insights into understanding the immune responses of ducks to recombinant DEV-ompH vaccines but also demonstrates the potential for simultaneous prevention of viral and bacterial infections using viral vectors expressing bacterial immunogens.

Evaluation of the Safety and Immunogenicity of Duck-Plague Virus gE Mutants

Duck plague (DP) is an acute infectious disease in the duck industry. The duck plague virus (DPV) is the pathogen, a subfamily of alphaherpesvirinae. gE is a type I membrane protein that contains three parts: an extracellular domain, a transmembrane domain, and a cytoplasmic domain. gE is the major virulence determinant of α-herpesvirus. However, the functions of the gE extracellular and cytoplasmic domains have not been reported in DPV. In this study, a gE extracellular domain deletion mutant and a gE cytoplasmic domain deletion mutant were constructed from DPV. Virus replication kinetics showed that the growth titers of both the gE ectodomain-deleted mutant virus and the gE cytoplasmic domain-deleted virus in DEFs were lower than that of the parental virus CHv-50. DPV CHv-gEΔET and DPV CHv-gEΔCT were continuously passed to the 20th passage in DEFs and the 10th in ducklings. The mutant virus DNA after passage was extracted for identification. The results showed that the gE ectodomain and gE cytoplasmic domain deletion mutant viruses have good genetic stability. The ducklings in each group (n=10) were inoculated with the same titers of DPV CHv-gEΔET, DPV CHv-gEΔCT, DPV CHv-ΔgE, and parental CHv-50, respectively. Clinical symptoms and serum antibody levels were detected after inoculation. The results showed that the virulence of DPV CHv-gEΔCT to ducklings was reduced compared with parental CHv-50, while the virulence of DPV CHv-gEΔET to ducklings was significantly reduced. 10⁵ TCID₅₀ DPV CHv-gEΔET or DPV CHv-ΔgE can induce ducklings to produce DPV-specific antibodies, protect the ducklings from virulent CHv challenge. Therefore, DPV CHv-gEΔET may serve as a promising vaccine candidate to prevent and control duck plague.

Duck plague virus UL41 protein inhibits RIG-I/MDA5-mediated duck IFN-β production via mRNA degradation activity

Retinoic acid-inducible gene I (RIG-I)-like receptors (RLRs) are cytosolic pattern recognition receptors that initiate innate antiviral immunity. Recent reports found that duck RLRs significantly restrict duck plague virus (DPV) infection. However, the molecular mechanism by which DPV evades immune responses is unknown. In this study, we first found that the DPV UL41 protein inhibited duck interferon-β (IFN-β) production mediated by RIG-I and melanoma differentiation-associated gene 5 (MDA5) by broadly downregulating the mRNA levels of important adaptor molecules, such as RIG-I, MDA5, mitochondrial antiviral signalling protein (MAVS), stimulator of interferon gene (STING), TANK-binding kinase 1 (TBK1), and interferon regulatory factor (IRF) 7. The conserved sites of the UL41 protein, E229, D231, and D232, were responsible for this activity. Furthermore, the DPV CHv-BAC-ΔUL41 mutant virus induced more duck IFN-β and IFN-stimulated genes (Mx, OASL) production in duck embryo fibroblasts (DEFs) than DPV CHv-BAC parent virus. Our findings provide insights into the molecular mechanism underlying DPV immune evasion.

The LORF5 Gene Is Non-essential for Replication but Important for Duck Plague Virus Cell-to-Cell Spread Efficiently in Host Cells

Duck plague virus (DPV) can cause high morbidity and mortality in many waterfowl species within the order Anseriformes. The DPV genome contains 78 open reading frames (ORFs), among which the LORF2, LORF3, LORF4, LORF5, and SORF3 genes are unique genes of avian herpesvirus. In this study, to investigate the role of this unique LORF5 gene in DPV proliferation, we generated a recombinant virus that lacks the LORF5 gene by a two-step red recombination system, which cloned the DPV Chinese virulent strain (DPV CHv) genome into a bacterial artificial chromosome (DPV CHv-BAC); the proliferation law of LORF5-deleted mutant virus on DEF cells and the effect of LORF5 gene on the life cycle stages of DPV compared with the parent strain were tested. Our data revealed that the LORF5 gene contributes to the cell-to-cell transmission of DPV but is not relevant to virus invasion, replication, assembly, and release formation. Taken together, this study sheds light on the role of the avian herpesvirus-specific gene LORF5 in the DPV proliferation life cycle. These findings lay the foundation for in-depth functional studies of the LORF5 gene in DPV or other avian herpesviruses.

Heterologous prime-boost: an important candidate immunization strategy against Tembusu virus

BACKGROUND

Tembusu virus (TMUV), a newly emerging pathogenic flavivirus, spreads rapidly between ducks, causing massive economic losses in the Chinese duck industry. Vaccination is the most effective method to prevent TMUV. Therefore, it is urgent to look for an effective vaccine strategy against TMUV. Heterologous prime-boost regimens priming with vaccines and boosting with recombinant adenovirus vaccines have been proven to be successful strategies for protecting against viruses in experimental animal models.

METHODS

In this study, heterologous and homologous prime-boost strategies using an attenuated salmonella vaccine and a recombinant adenovirus vaccine expressing prM-E or the E gene of TMUV were evaluated to protect ducks against TMUV infection for the first time, including priming and boosting with the attenuated salmonella vaccine, priming and boosting with the recombinant adenovirus vaccine, and priming with the attenuated salmonella vaccine and boosting with the recombinant adenovirus vaccine. Humoral and cellular immune responses were detected and evaluated. We then challenged the ducks with TMUV at 12 days after boosting to assay for clinical symptoms, mortality, viral loads and histopathological lesions after these different strategies.

RESULTS

Compared with the homologous prime-boost strategies, the heterologous prime-boost regimen produced higher levels of neutralizing antibodies and IgG antibodies against TMUV. Additionally, it could induce higher levels of IFN-γ than homologous prime-boost strategies in the later stage. Interestingly, the heterologous prime-boost strategy induced higher levels of IL-4 in the early stage, but the IL-4 levels gradually decreased and were even lower than those induced by the homologous prime-boost strategy in the later stage. Moreover, the heterologous prime-boost strategy could efficiently protect ducks, with low viral titres, no clinical symptoms and histopathological lesions in this experiment after challenge with TMUV, while slight clinical symptoms and histopathological lesions were observed with the homologous prime-boost strategies.

CONCLUSIONS

Our results indicated that the heterologous prime-boost strategy induced higher levels of humoral and cellular immune responses and better protection against TMUV infection in ducks than the homologous prime-boost strategies, suggesting that the heterologous prime-boost strategy is an important candidate for the design of a novel vaccine strategy against TMUV.

Recent advances in delivery of veterinary DNA vaccines against avian pathogens

Veterinary vaccines need to have desired characteristics, such as being effective, inexpensive, easy to administer, suitable for mass vaccination and stable under field conditions. DNA vaccines have been proposed as potential solutions for poultry diseases since they are subunit vaccines with no risk of infection or reversion to virulence. DNA vaccines can be utilized for simultaneous immunizations against multiple pathogens and are relatively easy to design and inexpensive to manufacture and store. Administration of DNA vaccines has been shown to stimulate immune responses and provide protection from challenges in different animal models. Although DNA vaccines offer advantages, setbacks including the inability to induce strong immunity, and the fact that they are not currently applicable for mass vaccination impede the use of DNA vaccines in the poultry industry. The use of either biological or physical carriers has been proposed as a solution to overcome the current delivery limitations of DNA vaccines for veterinary applications. This review presents an overview of the recent development of carriers for delivery of veterinary DNA vaccines against avian pathogens.

Duck Plague Virus Promotes DEF Cell Apoptosis by Activating Caspases, Increasing Intracellular ROS Levels and Inducing Cell Cycle S-Phase Arrest

Background: Duck plague virus (DPV) can induce apoptosis in duck embryo fibroblasts (DEFs) and in infected ducks, but the molecular mechanism of DPV-induced apoptosis remains unknown. Methods: We first used qRT-PCR and a Caspase-Glo assay to determine whether the caspase protein family plays an important role in DPV-induced apoptosis. Then, we used an intracellular ROS detection kit and the mitochondrial probe JC-1 to respectively detect ROS levels and mitochondrial membrane potential (MMP). Finally, flow cytometry was used to detect apoptosis and cell cycle progression. Results: In this study, the mRNA levels and enzymatic activities of caspase-3, caspase-7, caspase-8, and caspase-9 were significantly increased during DPV-induced apoptosis. The caspase inhibitors Z-DEVD-FMK, Z-LEHD-FMK, and Q-VD-Oph could inhibit DPV-induced apoptosis and promote viral replication. Subsequently, a significant decrease in MMP and an increase in the intracellular ROS levels were observed. Further study showed that pretreating infected cells with NAC (a ROS scavenger) decreased the intracellular ROS levels, increased the MMP, inhibited apoptosis, and promoted viral replication. Finally, we showed that DPV infection can cause cell cycle S-phase arrest. Conclusions: This study shows that DPV causes cell cycle S-phase arrest and leads to apoptosis through caspase activation and increased intracellular ROS levels. These findings may be useful for gaining an understanding of the pathogenesis of DPV and the apoptotic pathways induced by α-herpesviruses.

Oral Delivery of a DNA Vaccine Expressing the PrM and E Genes: A Promising Vaccine Strategy against Flavivirus in Ducks

A flavivirus, named duck tembusu virus (DTMUV), emerged in China in 2010. This virus has caused great economic losses in the poultry industry in China and may pose a threat to public health. As a safe, efficient and convenient vaccine development strategy, DNA-based vaccines have become a popular approach for both human and veterinary applications. Attenuated bacteria have been widely used as vehicles to deliver heterologous antigens to the immune system. Thus, an efficient and low-cost oral delivery DNA vaccine SL7207 (pVAX1-SME) based on envelope proteins (prM and E) of DTMUV and attenuated Salmonella typhimurium aroA^- strain SL7207 was developed and evaluated in this study. The prM and E antigen proteins were successfully expressed from the vaccine SL7207 (pVAX1-SME) both in vitro and in vivo. High titers of the specific antibody against the DTMUV-E protein and the neutralizing antibody against the DTMUV virus were both detected after vaccination with SL7207 (pVAX1-SME). Ducks orally vaccinated with the SL7207 (pVAX-SME) vaccine were efficiently protected from lethal DTMUV infection in this study. Taken together, we demonstrated that prM and E proteins of DTMUV possess strong immunogenicity against the DTMUV infection. Moreover, an oral delivery of the DNA vaccine SL7207 (pVAX1-SME) utilizing Salmonella SL7207 was an efficient way to protect the ducks against DTMUV infection and provides an economic and fast vaccine delivery strategy for a large-scale clinical use.

Oral Vaccination with a DNA Vaccine Encoding Capsid Protein of Duck Tembusu Virus Induces Protection Immunity

The emergence of duck tembusu virus (DTMUV), a new member of the Flavivirus genus, has caused great economical loss in the poultry industry in China. Since the outbreak and spread of DTMUV is hard to control in a clinical setting, an efficient and low-cost oral delivery DNA vaccine SL7207 (pVAX1-C) based on the capsid protein of DTMUV was developed and evaluated in this study. The antigen capsid protein was expressed from the DNA vaccine SL7207 (pVAX1-C), both in vitro and in vivo. The humoral and cellular immune responses in vivo were observed after oral immunization with the SL7207 (pVAX1-C) DNA vaccine. High titers of the specific antibody against the capsid protein and the neutralizing antibody against the DTMUV virus were both detected after inoculation. The ducks were efficiently protected from lethal DTMUV exposure by the SL7207 (pVAX1-C) vaccine in this experiment. Taken together, we demonstrated that the capsid protein of DTMUV possesses a strong immunogenicity against the DTMUV infection. Moreover, an oral delivery of the DNA vaccine SL7207 (pVAX1-C) utilizing Salmonella SL7207 was an efficient way to protect the ducks against DTMUV infection and provides an economic and fast vaccine delivery strategy for a large scale clinical use.

Duck virus enteritis (duck plague) - a comprehensive update

Duck virus enteritis (DVE), also called duck plague, is one of the major contagious and fatal diseases of ducks, geese and swan. It is caused by duck enteritis virus (DEV)/Anatid herpesvirus-1 of the genus Mardivirus, family Herpesviridae, and subfamily Alpha-herpesvirinae. Of note, DVE has worldwide distribution, wherein migratory waterfowl plays a crucial role in its transmission within and between continents. Furthermore, horizontal and/ or vertical transmission plays a significant role in disease spread through oral-fecal discharges. Either of sexes from varying age groups of ducks is vulnerable to DVE. The disease is characterized by sudden death, vascular damage and subsequent internal hemorrhage, lesions in lymphoid organs, digestive mucosal eruptions, severe diarrhea and degenerative lesions in parenchymatous organs. Huge economic losses are connected with acute nature of the disease, increased morbidity and mortality (5%-100%), condemnations of carcasses, decreased egg production and hatchability. Although clinical manifestations and histopathology can provide preliminary diagnosis, the confirmatory diagnosis involves virus isolation and detection using serological and molecular tests. For prophylaxis, both live-attenuated and killed vaccines are being used in broiler and breeder ducks above 2 weeks of age. Since DEV is capable of becoming latent as well as shed intermittently, recombinant subunit and DNA vaccines either alone or in combination (polyvalent) are being targeted for its benign prevention. This review describes DEV, epidemiology, transmission, the disease (DVE), pathogenesis, and advances in diagnosis, vaccination and antiviral agents/therapies along with appropriate prevention and control strategies.

Duck enteritis virus (DEV) UL54 protein, a novel partner, interacts with DEV UL24 protein

Background

UL24 is a multifunctional protein that is conserved among alphaherpesviruses and is believed to play an important role in viral infection and replication.

Results

In this paper, to investigate putative UL24-binding proteins and to explore the functional mechanisms of DEV UL24, yeast two-hybrid (Y2H) was carried out, and further verified the interaction between UL24 and partners by co-immunoprecipitation and fluorescence microscopy experiments. Interaction partners of UL24 protein were screened by yeast two-hybrid (Y2H) with the cDNA library of DEV-CHv strain post-infection DEF cells. A novel partner, DEV UL54 protein, was discovered by Y2H screening and bioinformatic. Co-immunoprecipitation experiments suggested that DEV UL24 interacted with UL54 proteins. And distribution of a part of UL54 protein was changed from nucleus to cytoplasm in DF-1 cells of co-subcellular localization experiments which also showed that DEV UL24 interacted with UL54 proteins.

Conclusions

The interaction between the DEV UL24 and UL54 proteins was discovered for the first time. Thus, DEV UL54 protein as a novel partner interacted with DEV UL24 protein.

Electronic supplementary material

The online version of this article (doi:10.1186/s12985-017-0830-5) contains supplementary material, which is available to authorized users.

Live attenuated Salmonella displaying HIV-1 10E8 epitope on fimbriae: systemic and mucosal immune responses in BALB/c mice by mucosal administration

The HIV-1 membrane proximal external region (MPER) that is targeted by several broadly neutralizing antibodies (BNAbs) has been considered a potential immunogen for vaccine development. However, to date the immunogenicity of these BNAb epitopes has not been made sufficiently adequate. In the present work, we used live attenuated Salmonella as a platform to present the HIV-1 MPER 10E8 epitope in the fimbriae. The insertion of the 10E8 epitope into the fimbriae had no significant influence on the expression and the absorption capacity of bacterial fimbriae, nor on the virulence and invasiveness of the attenuated Salmonella. After oral administration of the vaccine construct to mice followed by 10E8 epitope peptide boost, specific antibody responses in serum and mucosa as well as memory lymphocytes in spleen and plasma cells in bone marrow were induced. We also found that the live attenuated Salmonella vector directed the immunity toward Th1 bias, induced Th1 and Th2 cytokine responses and stimulated significant B cell differentiation into GC B, memory B and plasma cells. Therefore, we propose that the live attenuated Salmonella constitutively expressing HIV-1 BNAb epitopes on the fimbriae will be an effective approach to improving immune microenvironment and enhancing the immunogenicity of HIV-1 epitope vaccines.

DNA vaccination of poultry: The current status in 2015

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Poultry DNA vaccination studies are regularly being published since 1993.

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These studies are mainly, but not only, concerned with vaccination against viruses.

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The different strategies of improving DNA vaccine efficacies are presented.

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The fate of the vaccine plasmid, immune properties and other applications are described.

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Despite the compiling preclinical reports, a poultry DNA vaccine is yet unavailable in the market.

DNA vaccination is a promising alternative strategy for developing new human and animal vaccines. The massive efforts made these past 25 years to increase the immunizing potential of this kind of vaccine are still ongoing. A relatively small number of studies concerning poultry have been published. Even though there is a need for new poultry vaccines, five parameters must nevertheless be taken into account for their development: the vaccine has to be very effective, safe, inexpensive, suitable for mass vaccination and able to induce immune responses in the presence of maternal antibodies (when appropriate). DNA vaccination should meet these requirements. This review describes studies in this field performed exclusively on birds (chickens, ducks and turkeys). No evaluations of avian DNA vaccine efficacy performed on mice as preliminary tests have been taken into consideration. The review first describes the state of the art for DNA vaccination in poultry: pathogens targeted, plasmids used and different routes of vaccine administration. Second, it presents strategies designed to improve DNA vaccine efficacy: influence of the route of administration, plasmid dose and age of birds on their first inoculation; increasing plasmid uptake by host cells; addition of immunomodulators; optimization of plasmid backbones and codon usage; association of vaccine antigens and finally, heterologous prime-boost regimens. The final part will indicate additional properties of DNA vaccines in poultry: fate of the plasmids upon inoculation, immunological considerations and the use of DNA vaccines for purposes other than preventing infectious diseases.

Efficient strategy for constructing duck enteritis virus-based live attenuated vaccine against homologous and heterologous H5N1 avian influenza virus and duck enteritis virus infection

Duck is susceptible to many pathogens, such as duck hepatitis virus, duck enteritis virus (DEV), duck tembusu virus, H5N1 highly pathogenic avian influenza virus (HPAIV) in particular. With the significant role of duck in the evolution of H5N1 HPAIV, control and eradication of H5N1 HPAIV in duck through vaccine immunization is considered an effective method in minimizing the threat of a pandemic outbreak. Consequently, a practical strategy to construct a vaccine against these pathogens should be determined. In this study, the DEV was examined as a candidate vaccine vector to deliver the hemagglutinin (HA) gene of H5N1, and its potential as a polyvalent vaccine was evaluated. A modified mini-F vector was inserted into the gB and UL26 gene junction of the attenuated DEV vaccine strain C-KCE genome to generate an infectious bacterial artificial chromosome (BAC) of C-KCE (vBAC-C-KCE). The HA gene of A/duck/Hubei/xn/2007 (H5N1) was inserted into the C-KCE genome via the mating-assisted genetically integrated cloning (MAGIC) to generate the recombinant vector pBAC-C-KCE-HA. A bivalent vaccine C-KCE-HA was developed by eliminating the BAC backbone. Ducks immunized with C-KCE-HA induced both the cross-reactive antibodies and T cell response against H5. Moreover, C-KCE-HA-immunized ducks provided rapid and long-lasting protection against homologous and heterologous HPAIV H5N1 and DEV clinical signs, death, and primary viral replication. In conclusion, our BAC-C-KCE is a promising platform for developing a polyvalent live attenuated vaccine.

Antigen Delivery System II

This chapter reviews papers mostly written since 2005 that report results using live attenuated bacterial vectors to deliver after administration through mucosal surfaces, protective antigens, and DNA vaccines, encoding protective antigens to induce immune responses and/or protective immunity to pathogens that colonize on or invade through mucosal surfaces. Papers that report use of such vaccine vector systems for parenteral vaccination or to deal with nonmucosal pathogens or do not address induction of mucosal antibody and/or cellular immune responses are not reviewed.

An attenuated duck plague virus (DPV) vaccine induces both systemic and mucosal immune responses to protect ducks against virulent DPV infection

Duck plague (DP) is a severe disease caused by DP virus (DPV). Control of the disease is recognized as one of the biggest challenges in avian medicine. Vaccination is an efficient way to control DPV, and an attenuated vaccine is the main routine vaccine. The attenuated DPV vaccine strain CHa is a modified live vaccine, but the systemic and mucosal immune responses induced by this vaccine have been poorly understood. In this study, the immunogenicity and efficacy of the vaccine were evaluated after subcutaneous immunization of ducks. CD4(+) and CD8(+) T cells were counted by flow cytometry, and humoral and mucosal Ig antibodies were analyzed by enzyme-linked immunosorbent assay (ELISA). The results showed that high levels of T cells and Ig antibodies were present postimmunization and that there were more CD4(+) T cells than CD8(+) T cells. Titers of humoral IgG were higher than those of humoral IgA. Local IgA was found in each sample, whereas local IgG was found only in the spleen, thymus, bursa of Fabricius, harderian gland, liver, bile, and lung. In a protection assay, the attenuated DPV vaccine completely protected ducks against 1,000 50% lethal doses (LD50) of the lethal DPV strain CHv via oral infection. These data suggest that this subcutaneous vaccine elicits sufficient systemic and mucosal immune responses against lethal DPV challenge to be protective in ducks. This study provides broad insights into understanding the immune responses to the attenuated DPV vaccine strain CHa through subcutaneous immunization in ducks.

Attenuated Salmonella typhimurium carrying the hepatocyte growth factor and keratinocyte growth factor genes repairs gastrointestinal mucosal damage caused by chemotherapy

Radiotherapy and chemotherapy are the main therapeutic approaches for patients with malignant tumours, especially advanced tumours. However, they can cause adverse effects, one of which is gastrointestinal mucosal damage, which can greatly affect patients' quality of life. Until now, there have been no effective therapies to avoid or treat these adverse effects. In this study, we used attenuated Salmonella typhimurium (S. typhimurium) to deliver the hepatocyte growth factor (HGF) or keratinocyte growth factor (KGF) to murine gastrointestinal mucosa. We found that attenuated S. typhimurium carrying the HGF or KGF genes can effectively reduce the ratio of tumour to non-tumour carcass weight, repair damage to the gastrointestinal mucosal from chemotherapy, improve the immune response, and reduce the mortality rate of mice. Oral administration of attenuated S. typhimurium with HGF and KGF may be promising as a way of improving the quality of life of patients undergoing radiotherapy and chemotherapy.