Oral administration of live attenuated Salmonella enterica serovar Typhimurium expressing chicken interferon-α alleviates clinical signs caused by respiratory infection with avian influenza virus H9N2

Soluble expression, rapid purification, biological identification of chicken interferon-alpha using a thioredoxin fusion system in E. coli and its antiviral effects to H9N2 avian influenza virus

In this paper, we report a soluble expression based on Escherichia coli and two-step purification of a novel thioredoxin-tagged chicken interferon-α fusion protein (Trx-rChIFN-α) by using pET32a(+) expression system. The mature ChIFN-α gene was amplified by Reverse transcriptase-polymerase chain reaction (RT-PCR) and subcloned into pET-32a (+) vector prior to transformation into Rosetta (DE3) competent cells. After IPTG induction, the recombinant fusion protein was expressed efficiently in the soluble fraction. The protein purification was performed by nickel affinity chromatography and DEAE anion exchange chromatography. The purified product has a purity of 95% with a yield of 47.3 mg/L of culture. The specific activity of the fusion protein reaches to 2.0 × 10⁷ IU/mg as determined in the CEF/VSV titration system. After excision of the Trx tag by enterokinase, the remaining solo protein was confirmed as rChIFN-α protein by SDS-PAGE, N-terminal sequencing and mass spectrometry. The effects of this Trx-rChIFN-α fusion protein against H9N2 influenza virus infection were also evaluated in ovo. The results showed that the Trx-rChIFN-α protein could significantly reduce the hemagglutination titer of H9N2 virus, and the H9N2 viruses HA gene copy numbers. These findings will enable us to produce large amount and bio-active rChIFN-α protein for future applications.

Recombinant-attenuated Salmonella Pullorum strain expressing the hemagglutinin-neuraminidase protein of Newcastle disease virus (NDV) protects chickens against NDV and Salmonella Pullorum challenge

Newcastle disease virus (NDV) and Salmonella Pullorum have significant damaging effects on the poultry industry, but no previous vaccine can protect poultry effectively. In this study, a recombinant-attenuated S. Pullorum strain secreting the NDV hemagglutinin-neuraminidase (HN) protein, C79-13ΔcrpΔasd (pYA-HN), was constructed by using the suicide plasmid pREasd-mediated bacteria homologous recombination method to form a new bivalent vaccine candidate against Newcastle disease (ND) and S. Pullorum disease (PD). The effect of this vaccine candidate was compared with those of the NDV LaSota and C79-13ΔcrpΔasd (pYA) strains. The serum hemagglutination inhibition antibody titers, serum immunoglobulin G (IgG) antibodies, secretory IgA, and stimulation index in lymphocyte proliferation were increased significantly more (p < 0.01) in chickens inoculated with C79-13ΔcrpΔasd (pYA-HN) than with C79-13ΔcrpΔasd (pYA) but were not significantly increased compared with the chickens immunized with the LaSota live vaccine (p > 0.05). Moreover, the novel strain provides 60% and 80% protective efficacy against the NDV virulent strain F48E9 and the S. Pullorum virulent strain C79-13. In summary, in this study, a recombinant-attenuated S. Pullorum strain secreting NDV HN protein was constructed. The generation of the S. Pullorum C79-13ΔcrpΔasd (pYA-HN) strain provides a foundation for the development of an effective living-vector double vaccine against ND and PD.

Modulation of systemic and mucosal immunity against an inactivated vaccine of Newcastle disease virus by oral co-administration of live attenuated Salmonella enterica serovar Typhimurium expressing chicken interleukin-18 and interferon-α

Newcastle disease (ND) is a highly contagious disease of chickens causing significant economic losses worldwide. Due to limitations in the efficacy against currently circulating ND viruses, existing vaccination strategies require improvements, and incorporating immunomodulatory cytokines with existing vaccines might be a novel approach. Here, we investigated the systemic and mucosal immunomodulatory properties of oral co-administration of chicken interleukin-18 (chIL-18) and chicken interferon-α (chIFN-α) using attenuated Salmonella enterica serovar Typhimurium on an inactivated ND vaccine. Our results demonstrate that oral administration of S. enterica serovar Typhimurium expressing chIL-18 or chIFN-α provided enhanced systemic and mucosal immune responses, as determined by serum hemagglutination inhibition antibody and NDV Ag-specific IgG as well as NDV Ag-specific IgA in lung and duodenal lavages of chickens immunized with inactivated ND vaccine via the intramuscular or intranasal route. Notably, combined oral administration of S. enterica serovar Typhimurium expressing chIL-18 and chIFN-α significantly enhanced systemic and mucosal immunity in ND-vaccinated chickens, compared to single administration of S. enterica serovar Typhimurium expressing chIL-18 or chIFN-α. In addition, oral co-administration of S. enterica serovar Typhimurium expressing chIL-18 and chIFN-α provided enhanced NDV Ag-specific proliferation of peripheral blood mononuclear cells and Th1-biased cell-mediated immunity, compared to single administration of either construct. Therefore, our results provide valuable insight into the modulation of systemic and mucosal immunity by incorporation of immunomodulatory chIL-18 and chIFN-α using Salmonella vaccines into existing ND vaccines.

Modulation of Humoral and Cell-Mediated Immunity Against Avian Influenza and Newcastle Disease Vaccines by Oral Administration of Salmonella enterica Serovar Typhimurium Expressing Chicken Interleukin-18

Interleukin-18 (IL-18) has been known to induce interferon-γ (IFN-γ) production and promote Th1 immunity. Although mammalian IL-18 has been characterized in great detail, the properties and application of chicken IL-18 remain largely uninvestigated as of yet. In this study, we evaluated the immunomodulatory properties of Salmonella enterica serovar Typhimurium expressing chicken interleukin-18 (chIL-18) on immune responses induced by avian influenza (AI) and Newcastle disease (ND) vaccines. After oral administration of S. enterica serovar Typhimurium expressing chIL-18, chickens were vaccinated intramuscularly with the recommended dose of either inactivated AI H9N2 vaccine or ND (B1 strain) vaccine. Chickens receiving a primary vaccination were boosted using the same protocol 7 days later. Humoral and cell-mediated immune responses were evaluated in terms of HI antibody titers and proliferation and mRNA expression of IFN-γ and IL-4 of peripheral blood mononuclear cells (PBMC) in response to specific antigen stimulation. According to our results, oral administration of S. enterica serovar Typhimurium expressing chIL-18 induced enhanced humoral and Th1-biased cell-mediated immunity against AI and ND vaccines, compared to that of chickens received S. enterica serovar Typhimurium harboring empty vector. Therefore, we conclude that our proposed vaccination regimen using inactivated AI and ND viruses along with oral administration of S. enterica serovar Typhimurium expressing chIL-18 may provide a novel approach in protecting chicken from currently circulating AI and ND virus strains.

Insight into alternative approaches for control of avian influenza in poultry, with emphasis on highly pathogenic H5N1

Highly pathogenic avian influenza virus (HPAIV) of subtype H5N1 causes a devastating disease in poultry but when it accidentally infects humans it can cause death. Therefore, decrease the incidence of H5N1 in humans needs to focus on prevention and control of poultry infections. Conventional control strategies in poultry based on surveillance, stamping out, movement restriction and enforcement of biosecurity measures did not prevent the virus spreading, particularly in developing countries. Several challenges limit efficiency of the vaccines to prevent outbreaks of HPAIV H5N1 in endemic countries. Alternative and complementary approaches to reduce the current burden of H5N1 epidemics in poultry should be encouraged. The use of antiviral chemotherapy and natural compounds, avian-cytokines, RNA interference, genetic breeding and/or development of transgenic poultry warrant further evaluation as integrated intervention strategies for control of HPAIV H5N1 in poultry.

A review of vaccine development and research for industry animals in Korea

Vaccination has proven to be the most cost-effective strategy for controlling a wide variety of infectious diseases in humans and animals. For the last decade, veterinary vaccines have been substantially developed and demonstrated their effectiveness against many diseases. Nevertheless, new vaccines are greatly demanded to effectively control newly- and re-emerging pathogens in livestock. However, development of veterinary vaccines is a challenging task, in part, due to a variety of pathogens, hosts, and the uniqueness of host-susceptibility to each pathogen. Therefore, novel concepts of vaccines should be explored to overcome the limitation of conventional vaccines. There have been greatly advanced in the completion of genomic sequencing of pathogens, the application of comparative genomic and transcriptome analysis. This would facilitate to open opportunities up to investigate a new generation of vaccines; recombinant subunit vaccine, virus-like particle, DNA vaccine, and vector-vehicle vaccine. Currently, such types of vaccines are being actively explored against various livestock diseases, affording numerous advantages over conventional vaccines, including ease of production, immunogenicity, safety, and multivalency in a single shot. In this articles, the authors present the current status of the development of veterinary vaccines at large as well as research activities conducted in Korea.

Enhancement of Th1-biased protective immunity against avian influenza H9N2 virus via oral co-administration of attenuated Salmonella enterica serovar Typhimurium expressing chicken interferon-α and interleukin-18 along with an inactivated vaccine

Background

Control of currently circulating re-assorted low-pathogenicity avian influenza (LPAI) H9N2 is a major concern for both animal and human health. Thus, an improved LPAI H9N2 vaccination strategy is needed to induce complete immunity in chickens against LPAI H9N2 virus strains. Cytokines play a crucial role in mounting both the type and extent of an immune response generated following infection with a pathogen or after vaccination. To improve the efficacy of inactivated LPAI H9N2 vaccine, attenuated Salmonella enterica serovar Typhimurium was used for oral co-administration of chicken interferon-α (chIFN-α) and chicken interleukin-18 (chIL-18) as natural immunomodulators.

Results

Oral co-administration of S. enterica serovar Typhimurium expressing chIFN-α and chIL-18, prior to vaccination with inactivated AI H9N2 vaccine, modulated the immune response of chickens against the vaccine antigen through enhanced humoral and Th1-biased cell-mediated immunity, compared to chickens that received single administration of S. enterica serovar Typhimurium expressing either chIFN-α or chIL-18. To further test the protective efficacy of this improved vaccination regimen, immunized chickens were intra-tracheally challenged with a high dose of LPAI H9N2 virus. Combined administration of S. enterica serovar Typhimurium expressing chIFN-α and chIL-18 showed markedly enhanced protection compared to single administration of the construct, as determined by mortality, clinical severity, and feed and water intake. This enhancement of protective immunity was further confirmed by reduced rectal shedding and replication of AIV H9N2 in different tissues of challenged chickens.

Conclusions

Our results indicate the value of combined administration of chIFN-α and chIL-18 using a Salmonella vaccine strain to generate an effective immunization strategy in chickens against LPAI H9N2.

Oral co-administration of live attenuated Salmonella enterica serovar Typhimurium expressing chicken interferon-α and interleukin-18 enhances the alleviation of clinical signs caused by respiratory infection with avian influenza virus H9N2

The combined use of cytokines has shown synergistic and/or additive effects in controlling several viral infections of livestock animals. However, little is known concerning the practical use of chicken cytokine combinations to control avian diseases. Here, we investigated the antiviral efficacy of oral co-administration of chicken interferon-α (chIFN-α) and chicken interleukin-18 (chIL-18) using attenuated Salmonella enterica serovar Typhimurium in chickens infected with avian influenza virus (AIV) H9N2. Our results demonstrate that oral co-administration of S. enterica serovar Typhimurium expressing chIFN-α and chIL-18 produced a greater alleviation of clinical signs caused by respiratory infection with AIV H9N2 in chickens, when compared to administration of S. enterica serovar Typhimurium expressing either chIFN-α or chIL-18 alone. Mortality, clinical symptom severity, and feed and water intake were used to access treatment effectiveness. This enhancement of antiviral immunity was further confirmed by evidence of reduced rectal shedding and decreased replication of AIV H9N2 in several different tissues of challenged chickens including trachea, lung, cecal tonsil, and brain. Furthermore, oral co-administration of chIFN-α and chIL-18 more efficiently modulated the immune responses of chickens against AIV H9N2 by enhancing both humoral and Th1-biased cell-mediated immunity, compared to single administration of either construct. Therefore, our results suggest that the combined administration of two chicken cytokines, chIFN-α and chIL-18, using attenuated S. enterica serovar Typhimurium as an oral carrier, provides an effective means for controlling respiratory disease caused by AIV H9N2 infection.