Protective immune response of chickens against Newcastle disease, induced by the intranasal vaccination with inactivated virus

Development and Immunoprotection of Bacterium-like Particle Vaccine against Infectious Bronchitis in Chickens

Infectious bronchitis (IB) is a major threat to the global poultry industry. Despite the availability of commercial vaccines, the IB epidemic has not been effectively controlled. The exploration of novel IBV vaccines may provide a new way to prevent and control IB. In this study, BLP-S1, a bacterium-like particle displaying the S1 subunit of infectious bronchitis virus (IBV), was constructed using the GEM-PA surface display system. The immunoprotective efficacy results showed that BLP-S1 can effectively induce specific IgG and sIgA immune responses, providing a protection rate of 90% against IBV infection in 14-day-old commercial chickens. These results suggest that BLP-S1 has potential for the development of novel vaccines with good immunogenicity and immunoprotection.

Adjuvant effects of bacterium-like particles in the intranasal vaccination of chickens against Newcastle disease

Given that the respiratory mucosa is an important site for the initial replication of Newcastle disease virus (NDV), developing intranasal vaccines for chickens is an effective strategy to protect against this disease. The low immunogenicity of inactivated NDV administered by the mucosal route motivated us to identify a safe and potent adjuvant. Previous studies have shown that bacterium-like particles (BLPs), which serve as mucosal adjuvants, induce effective local and systemic immune responses through TLR2 signaling in both mammals and humans. Here, we report that BLPs could activate the innate immune system of chickens in a manner that was dependent on the combination of chicken TLR2 type 1 (chTLR2t1) and chicken TLR1 type 1 (chTLR1t1). The chicken macrophage-like HD11 cell line was stimulated with BLPs, resulting in the production of nitric oxide and the expression of the proinflammatory cytokines IFN-γ, IL-1β and IL-6. Chickens intranasally immunized with inactivated NDV vaccines mixed with BLP adjuvants exhibited significantly increased levels of local SIgA in their tracheal lavage fluid and as well as hemagglutination-inhibiting antibodies in serum samples. The strong systemic and local immune responses induced by BLP-adjuvanted vaccines provided 100 % protection against intranasal challenge with a lethal dose of virulent NDV without showing any signs of disease. These results indicate that BLPs should be considered for use as a potential mucosal adjuvant for inactivated NDV vaccines and other vaccines for poultry.

Evaluation of surface glycoproteins of classical swine fever virus as immunogens and reagents for serological diagnosis of infections in pigs: a recombinant Newcastle disease virus approach

Classical swine fever (CSF) is an important viral disease of domestic pigs and wild boar. The structural proteins E2 and E^rns of classical swine fever virus (CSFV), which participate in the attachment of the virion to the host cell surface and its subsequent entry, are immunogenic. The E2 and E^rns proteins are used for diagnosis and the development of vaccines against CSFV infection in swine. Newcastle disease virus (NDV) has been successfully used as a viral vector to express heterologous proteins. In the present study, the E2 and E^rns proteins of CSFV were expressed in cell culture as well as embryonated chicken eggs, using recombinant NDV (rNDV). Rescued rNDV expressing the E2 and E^rns proteins induced the production of CSFV-neutralizing antibodies upon intranasal vaccination of pigs. Serum samples from vaccinated animals were found to neutralize both homologous and heterologous CSFV strains. Furthermore, rNDV expressing the E2 and E^rns proteins of CSFV was used to develop an indirect ELISA, which was used to measure the the antibody titers of randomly collected serum samples. The results suggested that the ELISA based on rNDV-expressed E2 and E^rns proteins could be used to screen for CSFV infections. This study shows that rNDV-based expression of CSFV antigens is potentially applicable for development of vaccines and diagnostic tests for CSFV infection. This approach could be an economically favorable alternative to the existing vaccine and diagnostics for CSFV in pigs.

Expression and serological application of recombinant epitope-repeat protein carrying an immunodominant epitope of Newcastle disease virus nucleoprotein

Purpose

The aim of the present study was to develop a serodiagnostic test for differentiation infected from vaccinated animal (DIVA) strategy accompanying the marker vaccine lacking an immunodominant epitope (IDE) of nucleoprotein of Newcastle disease virus (NDV).

Materials and Methods

Recombinant epitope-repeat protein (rERP) gene encoding eight repeats of the IDE sequence (ETQFLDLMRAVANSMR) by tetra-glycine linker was synthesized. Recombinant baculovirus carrying the rERP gene was generated to express the rERP in insect cells. Specificity and sensitivity of an indirect enzyme-linked immunosorbent assay (ELISA) employing the rERP was evaluated.

Results

The rERP with molecular weight of 20 kDa was successfully expressed by the recombinant baculovirus in an insect-baculovirus system. The rERP was antigenically functional as demonstrated by Western blotting. An indirect ELISA employing the rERP was developed and its specificity and sensitivity was determined. The ELISA test allowed discrimination of NDV infected sera from epitope deletion virus vaccinated sera.

Conclusion

The preliminary results represent rERP ELISA as a promising DIVA diagnostic tool.

Vaccination of broilers against Newcastle disease in the presence of maternally derived antibodies

Objective: The aim of this study was to evaluate the efficacy of a live attenuated vaccine against Newcastle disease in broilers with different levels of maternally derived antibodies (MDA). While vaccination remains the single most important means for controlling Newcastle disease, presence of MDA may interfere with the vaccination of young birds and decrease the efficacy of the vaccine. Materials and methods: Day-old chicks with variable levels of MDA (negative, low and high) were vaccinated with a live attenuated vaccine against Newcastle disease. Three most commonly used inoculation routes were compared; oculonasal, spray and oral (drinking water). Onset and duration of immunity were measured by serology and challenge with virulent virus. Results: Immune response in vaccinated MDA-positive birds was delayed in comparison with SPF controls. Protection was well established already at 14 days post vaccination in SPF birds while in MDA-positive birds it was 1–2 weeks delayed and was lower throughout the study. Non-vaccinated MDA-positive birds lost passive protection completely at 3–4 weeks of age and were significantly more susceptible to challenge than vaccinated hatch mates at all test points. The protection rate increased in vaccinated birds towards the end of the experiment and reached 70–100 % at the last test points (35–42 days of age). Correlation of haemagglutination inhibition (HI) titre vs. protection rate revealed the importance of cellular and local immunity as most of the vaccinated birds with low HI titre were protected, contrary to their unvaccinated hatch mates with the same HI titre. Oculonasal route seems to provide slightly better protection than the other two routes. Conclusions and clinical relevance: Although immune protection in vaccinated MDA-positive birds may be decreased or delayed, vaccination still provides high protection against ND challenge in comparison with the unvaccinated hatch mates. The degree of interference seems to be proportional to the level of MDA. Vaccination schedules therefore need to be designed according to the immune status of the flock.

The role of vaccination in risk mitigation and control of Newcastle disease in poultry

Newcastle disease is regarded as one of the most important avian diseases throughout the world and continues to be a threat and economic burden to the poultry industry. With no effective treatment, poultry producers rely primarily on stringent biosecurity and vaccination regimens to control the spread of this devastating disease. This concise review provides an historical perspective of Newcastle disease vaccination and how fundamental research has paved the way for the development of instrumental techniques which are still in use today. Although vaccination programmes have reduced the impact of clinical disease, they have historically been ineffective in controlling the spread of virulent viruses and therefore do not always offer an adequate solution to the world's food security problems. However, the continued development of novel vaccine technology and improved biosecurity measures through education may offer a solution to help reduce the global threat of Newcastle disease on the poultry industry.

Long-Term Effect of Serial Infections with H13 and H16 Low-Pathogenic Avian Influenza Viruses in Black-Headed Gulls

Infections of domestic and wild birds with low-pathogenic avian influenza viruses (LPAIVs) have been associated with protective immunity to subsequent infection. However, the degree and duration of immunity in wild birds from previous LPAIV infection, by the same or a different subtype, are poorly understood. Therefore, we inoculated H13N2 (A/black-headed gull/Netherlands/7/2009) and H16N3 (A/black-headed gull/Netherlands/26/2009) LPAIVs into black-headed gulls (Chroicocephalus ridibundus), their natural host species, and measured the long-term immune response and protection against one or two reinfections over a period of >1 year. This is the typical interval between LPAIV epizootics in wild birds. Reinfection with the same virus resulted in progressively less virus excretion, with complete abrogation of virus excretion after two infections for H13 but not H16. However, reinfection with the other virus affected neither the level nor duration of virus excretion. Virus excretion by immunologically naive birds did not differ in total levels of excreted H13 or H16 virus between first- and second-year birds, but the duration of H13 excretion was shorter for second-year birds. Furthermore, serum antibody levels did not correlate with protection against LPAIV infection. LPAIV-infected gulls showed no clinical signs of disease. These results imply that the epidemiological cycles of H13 and H16 in black-headed gulls are relatively independent from each other and depend mainly on infection of first-year birds.

IMPORTANCE

Low-pathogenic avian influenza viruses (LPAIVs) circulate mainly in wild water birds but are occasionally transmitted to other species, including humans, where they cause subclinical to fatal disease. To date, the effect of LPAIV-specific immunity on the epidemiology of LPAIV in wild birds is poorly understood. In this study, we investigated the effect of H13 and H16 LPAIV infection in black-headed gulls on susceptibility and virus excretion of subsequent infection with the same or the other virus within the same breeding season and between breeding seasons. These are the only two LPAIV hemagglutinin subtypes predominating in this species. The findings suggest that H13 and H16 LPAIV cycles in black-headed gull populations are independent of each other, indicate the importance of first-year birds in LPAIV epidemiology, and emphasize the need for alternatives to avian influenza virus (AIV)-specific serum antibodies as evidence of past LPAIV infection and correlates of protection against LPAIV infection in wild birds.

Cytotoxic T cell vaccination with PLGA microspheres interferes with influenza A virus replication in the lung and suppresses the infectious disease

Current influenza virus vaccines aim to elicit antibodies directed toward viral surface glycoproteins, which however are prone to antigenic drift. Cytotoxic T lymphocytes (CTLs) can exhibit heterosubtypic immunity against most influenza A viruses. In our study, we encapsulated the highly conserved, immunodominant, HLA-A*0201 restricted epitope from the influenza virus matrix protein M158-66 together with TLR ligands in biodegradable poly(d,l-lactide-co-glycolide) (PLGA) microspheres. Subcutaneous immunization of transgenic mice expressing chimeric HLA-A*0201 molecules with these microspheres induced a strong and sustained CTL response which sufficed to prevent replication of a recombinant vaccinia virus expressing the influenza A virus (IAV) matrix protein but not the replication of IAV in the lung. However, subcutaneous priming followed by intranasal boosting with M158-66 bearing PLGA microspheres was able to induce vigorous CTL responses both in the lung and spleen of mice which interfered with IAV replication, weight loss, and infection-related death. Taken together, vaccination with well-defined and highly conserved IAV-derived CTL epitopes encapsulated into clinically compatible PLGA microspheres contribute to the control of influenza A virus infections. The promptitude and broad reactivity of the CTL response may help to attenuate pandemic outbreaks of influenza viruses.

Immune responses and interactions following simultaneous application of live Newcastle disease, infectious bronchitis and avian metapneumovirus vaccines in specific-pathogen-free chicks

Interactions between live Newcastle disease virus (NDV), avian metapneumovirus (aMPV) and infectious bronchitis virus (IBV) vaccines following simultaneous vaccination of day old specific pathogen free (SPF) chicks were evaluated. The chicks were divided into eight groups: seven vaccinated against NDV, aMPV and IBV (single, dual or triple) and one unvaccinated as control. Haemagglutination inhibition (HI) NDV antibody titres were similar across all groups but were above protective titres. aMPV vaccine when given with other live vaccines suppressed levels of aMPV enzyme-linked immunosorbent assay (ELISA) antibodies. Cellular and local immunity induced by administration of NDV, aMPV or IBV vaccines (individually or together) showed significant increase in CD4+, CD8+ and IgA bearing B-cells in the trachea compared to the unvaccinated group. Differences between the vaccinated groups were insignificant. Simultaneous vaccination with live NDV, aMPV and IBV did not affect the protection conferred against aMPV or IBV.

Assessment of cellular and mucosal immune responses in chicks to Newcastle disease oral pellet vaccine (D58 strain) using qPCR

To assess the cell mediated and mucosal immune responses in chicks to Newcastle disease vaccine, expression levels of certain genes encoding cytokines and chemokines were quantified by q-PCR. The utility of cytokine and chemokine gene expression profile in estimating the cell mediated and humoral immune response has been established. The cell mediated immune response was assessed by quantifying the IFN-γ gene expression in splenocytes and compared with colorimetric blastogenesis assay. The mucosal immune response was assessed by quantifying the expression of IL-8, IL1-β, MIP1-β, K60 and K203 in the intestinal cells and compared with IgA ELISA. On 14th day post vaccination, the expression of IFN-γ was upregulated by 12-folds in the Group I, which have received oral pellet vaccine and fourfolds in the Group II where birds have received live thermostable vaccine as occulonasal instillation. 3 and 7 days after receiving booster, the same cytokine gene was upregulated by 12-folds and 27-folds respectively in the Group III, where birds have received live thermostable ND vaccine as priming vaccine and oral pellet vaccine as booster. On 21st day post vaccination the expression of IL-8 was upregulated by 42.8-folds in Group I and 3.3-folds in the Group II. The expression of IL-1β was upregulated by eightfolds on 3rd day post vaccination and 23-folds on 21st day post vaccination in Group I. The expression of macrophage inflammatory protein-1β (MIP-1β) was upregulated by 16-folds in Group I and 70-folds in Group II on 14th day post vaccination. No significant change in expression of chemokine genes K60 and K203 in vaccinated birds. The results were comparable with the results of conventional tests and proved the utility of qPCR in estimating the cellular and mucosal immune responses.

Enhancing mucosal immunity in mice by recombinant adenovirus expressing major epitopes of porcine circovirus-2 capsid protein delivered with cytosine-phosphate-guanosine oligodeoxynucleotides

A recombinant replication-defective adenovirus expressing the major epitopes of porcine circovirus-2 (PCV-2) capsid protein (rAd/Cap/518) was previously constructed and shown to induce mucosal immunity in mice following intranasal delivery. In the present study, immune responses induced by intranasal immunization with a combination of rAd/Cap/518 and cytosine-phosphate-guanosine oligodeoxynucleotides (CpG ODN) were evaluated in mice. The levels of PCV-2-specific IgG in serum and IgA in saliva, lung, and intestinal fluids were significantly higher in the group immunized with rAd/Cap/518 and CpG ODN than animals immunized with rAd/Cap/518 alone. The frequencies of IL-2-secreting CD4⁺ T cells and IFN-γ-producing CD8⁺ T cells were significantly higher in the combined immunization group than mice immunized with rAd/Cap/518 alone. The frequencies of CD3⁺, CD3⁺CD4⁺CD8^-, and CD3⁺CD4^-CD8⁺ T cells in the combined immunization group were similar to that treated with CpG ODN alone, but significantly higher than mice that did not receive CpG ODN. PCV-2 load after challenge in the combined immunization group was significantly lower than that in the phosphate-buffered saline placebo group and approximately 7-fold lower in the group treated with CpG ODN alone. These results indicate that rAd/Cap/518 combined with CpG ODN can enhance systemic and local mucosal immunity in mice, and represent a promising synergetic mucosal vaccine against PCV-2.

Evaluation the surface antigen of the Salmonella typhimurium ATCC 14028 ghosts prepared by "SLRP"

Recently, bacterial ghosts (BGs) were prepared using a protocol based on critical chemical concentrations. It has been given the name "sponge like" (SL) protocol and used in its reduced form "sponge like reduced protocol" (SLRP). While specific antibody for Salmonella is available on the market under the commercial names (of some kits) such as Febrile Antigen Kit (N.S. BIO-TEC), we used the described Kit to investigate the validity of the SLRP. In this study, using SLRP we succeeded to prepare STGs with correct surface antigens could interact with their specific antibodies. Additionally the study has included oral vaccination with STGs with challenge test. The rats serums have been evaluated against both of the O and H antigens. The antigen-antibody interaction (agglutination) results of both the SLRP and the animal experiments prove that we have correct STGs able to immunize the rats against viable Salmonella. STGs could be used as vaccine and as adjuvant and in the antibodies and in the diagnostic kits production. This study is an additional step for the establishment of correct BGs for immunological purposes.

Immunization with a thermostable newcastle disease virus K148/08 strain originated from wild mallard duck confers protection against lethal viscerotropic velogenic newcastle disease virus infection in chickens

Newcastle disease (ND) is one of the most devastating poultry infections because of its worldwide distribution and accompanying economical threat. In the present study, we characterized the ND virus (NDV) K148/08 strain from wild mallard duck, with regard to safety, thermostability, immunogenicity, and protective efficacy against velogenic ND viral infection. The NDV K148/08 strain offered enhanced immunogenicity and safety relative to commercially available vaccine strains. The NDV K148/08 strain was safe in 1-day-old SPF chicks after vaccination using a coarse or cabinet-type fine sprayer. We demonstrated that the NDV K148/08 strain elicited high levels of antibody responses and provided protective efficacy against lethal NDV challenge. In addition, the thermostability of the NDV K148/08 strain was as high as that of the thermostable V4 strain. Therefore, the NDV K148/08 strain may be useful to ensure NDV vaccine performance and effectiveness in developing countries, especially in remote areas without cold chains.

Effect of passive immunization on immunogenicity and protective efficacy of vaccination against a Mexican low-pathogenic avian H5N2 influenza virus

Background

Despite the use of vaccines, low‐pathogenic (LP) H5N2 influenza viruses have continued to circulate and evolve in chickens in Mexico since 1993, giving rise to multiple genetic variants. Antigenic drift is partially responsible for the failure to control H5N2 influenza by vaccination; the contribution of maternal antibodies to this problem has received less attention.

Methods

We investigated the effect of different antisera on the efficacy of vaccination and whether booster doses of vaccine can impact immune suppression.

Results

While single doses of inactivated oil emulsion vaccine to currently circulating H5N2 influenza viruses provide partial protection from homologous challenge, chickens that receive high‐titer homologous antisera intraperitoneally before vaccination showed effects ranging from added protection to immunosuppression. Post‐infection antisera were less immunosuppressive than antisera obtained from field‐vaccinated chickens. Homologous, post‐infection chicken antisera provided initial protection from virus challenge, but reduced the induction of detectable antibody responses. Homologous antisera from field‐vaccinated chickens were markedly immunosuppressive, annulling the efficacy of the vaccine and leaving the chickens as susceptible to infection as non‐vaccinated birds. Booster doses of vaccine reduced the immunosuppressive effects of the administered sera.

Conclusion

Vaccine efficacy against LP H5N2 in Mexico can be severely reduced by maternal antibodies. Source‐dependent antisera effects offer the possibility of further elucidation of the immunosuppressive components involved.

Preparation and efficacy of a live newcastle disease virus vaccine encapsulated in chitosan nanoparticles

BACKGROUND

Newcastle disease (ND) is a highly contagious viral disease of poultry caused by pathogenic strains of the Newcastle disease virus (NDV). Live NDV vaccines are administered by drinking water, eyedrops or coarse aerosol spray. To further enhance mucosal immune responses, chitosan nanoparticles were developed for the mucosal delivery of a live NDV vaccine.

METHODOLOGY/PRINCIPAL FINDINGS

A lentogenic live-virus vaccine (strain LaSota) against NDV encapsulated in chitosan nanoparticles were developed using an ionic crosslinking method. Chitosan nanoparticles containing the lentogenic live-virus vaccine against NDV (NDV-CS-NPs) were produced with good morphology, high stability, a mean diameter of 371.1 nm, an encapsulation rate of 77% and a zeta potential of +2.84 mV. The Western blotting analysis showed that NDV structural proteins were detected in NDV-CS-NPs. The virus release assay results of NDV-CS-NPs indicated that NDV was released from NDV-CS-NPs. Chickens immunized orally or intranasally with NDV-CS-NPs were fully protected whereas one out of five chickens immunized with the LaSota live NDV vaccine and three out of five chickens immunized with the inactivated NDV vaccine were dead after challenge with the highly virulent NDV strain F48E9.

CONCLUSIONS/SIGNIFICANCE

NDV-CS-NPs induced better protection of immunized specific pathogen free chickens compared to the live NDV vaccine strain LaSota and the inactivated NDV vaccine. This study lays a foundation for the further development of mucosal vaccines and drugs encapsulated in chitosan nanoparticles.

Intraocular vaccination with an inactivated highly pathogenic avian influenza virus induces protective antibody responses in chickens

Because it is expected to induce cross-reactive serum and mucosal antibody responses, mucosal vaccination against highly pathogenic avian influenza (HPAI) is potentially superior to conventional parenteral vaccination. Here, we tested whether intraocular vaccination with an inactivated AI virus induced protective antibody responses in chickens. Chickens were inoculated intraocularly twice with 10(4) hemagglutination units of an inactivated H5N1 HPAI virus. Four weeks after the second vaccination, the chickens were challenged with a lethal dose of the homologous H5N1 HPAI virus. Results showed that most of the vaccinated chickens mounted positive antibody responses. The median serum hemagglutination inhibition titer was 1:80. Addition of CpG oligodeoxynucleotide 2006 or cholera toxin to the vaccine did not enhance serum antibody titers. Cross-reactive anti-hemagglutinin IgG, but not IgA, was detected in oropharyngeal secretions. In accordance with these antibody results, most vaccinated chickens survived a lethal challenge with the H5N1 HPAI virus and did not shed the challenge virus in respiratory or digestive tract secretions. Our results show that intraocular vaccination with an inactivated AI virus induces not only systemic but also mucosal antibody responses and confers protection against HPAI in chickens.

Cross-protective peptide vaccine against influenza A viruses developed in HLA-A*2402 human immunity model

Background

The virus-specific cytotoxic T lymphocyte (CTL) induction is an important target for the development of a broadly protective human influenza vaccine, since most CTL epitopes are found on internal viral proteins and relatively conserved. In this study, the possibility of developing a strain/subtype-independent human influenza vaccine was explored by taking a bioinformatics approach to establish an immunogenic HLA-A24 restricted CTL epitope screening system in HLA-transgenic mice.

Methodology/Principal Findings

HLA-A24 restricted CTL epitope peptides derived from internal proteins of the H5N1 highly pathogenic avian influenza A virus were predicted by CTL epitope peptide prediction programs. Of 35 predicted peptides, six peptides exhibited remarkable cytotoxic activity in vivo. More than half of the mice which were subcutaneously vaccinated with the three most immunogenic and highly conserved epitopes among three different influenza A virus subtypes (H1N1, H3N2 and H5N1) survived lethal influenza virus challenge during both effector and memory CTL phases. Furthermore, mice that were intranasally vaccinated with these peptides remained free of clinical signs after lethal virus challenge during the effector phase.

Conclusions/Significance

This CTL epitope peptide selection system can be used as an effective tool for the development of a cross-protective human influenza vaccine. Furthermore this vaccine strategy can be applicable to the development of all intracellular pathogens vaccines to induce epitope-specific CTL that effectively eliminate infected cells.

A lack of antibody formation against inactivated influenza virus after aerosol vaccination in presence or absence of adjuvantia

In the poultry industry, infections with avian influenza virus (AIV) can result in significant economic losses. The risk and the size of an outbreak might be restricted by vaccination of poultry. A vaccine that would be used for rapid intervention during an outbreak should be safe to use, highly effective after a single administration and be suitable for mass application. A vaccine that could be applied by spray or aerosol would be suitable for mass application, but respiratory applied inactivated influenza is poorly immunogenic and needs to be adjuvanted. We chose aluminum OH, chitosan, cholera toxin B subunit (CT-B), and Stimune as adjuvant for an aerosolized vaccine with inactivated H9N2. Each adjuvant was tested in two doses. None of the adjuvanted vaccines induced AIV-specific antibodies after single vaccination, measured 1 and 3 weeks after vaccination by aerosol, in contrast to the intramuscularly applied vaccine. The aerosolized vaccine did enter the chickens' respiratory tract as CT-B-specific serum antibodies were detected after 1 week in chickens vaccinated with the CT-B-adjuvanted vaccine. Chickens showed no adverse effects after the aerosol vaccination based on weight gain and clinical signs. The failure to detect AIV-specific antibodies might be due to the concentration of the inactivated virus.

Adjuvant effect of liposome in chicken result from induction of nitric oxide

Intranasal delivery of liposome-encapsulated inactivated Newcastle Disease virus (NDV) is known to be an effective vaccine for inducing immunity in the respiratory tract from our previous reports. Four-week-old specific pathogen-free chickens were intranasally immunized with NDV entrapped in phosphatidylcholine-liposomes (PC-Lip). The mucosal levels of anti-NDV s-immunoglobulin A (IgA), serum IgG, a high hemagglutination inhibition titer (1:640), and the high survival rate with the PC-Lip vaccine were comparable to those of our previous report. The immune mechanisms of the PC-Lip adjuvant were determined by in vitro cellular experiments using the NO production of chicken spleen macrophages. The most important finding of this study was proving that macrophages were stimulated by PC-Lip via the extracellular regulated kinase (ERK) 1/2 and nuclear factor (NF)-κB activation pathways. This finding may be useful for developing potent mucosal vaccine delivery systems in the future.

Local and systemic immune responses following infection of broiler-type chickens with avian Metapneumovirus subtypes A and B

Infections with avian Metapneumovirus (aMPV) are often associated with swollen head syndrome in meat type chickens. Previous studies in turkeys have demonstrated that local humoral and cell-mediated immunity plays a role in aMPV-infection. Previous experimental and field observations indicated that the susceptibility of broilers and their immune reactions to aMPV may differ from turkeys. In the presented study local and systemic immune reactions of broilers were investigated after experimental infections with subtypes A and B aMPV of turkey origin. Both virus subtypes induced a mild respiratory disease. The recovery from respiratory signs correlated with the induction of local and systemic aMPV virus-neutralizing antibodies, which began to rise at 6 days post infection (dpi), when the peak of clinical signs was observed. In a different manner to the virus neutralizing (VN) and IgG-ELISA serum antibody titres, which showed high levels until the end of the experiments between 24 and 28 dpi, the specific IgA-ELISA and VN-antibody levels in tracheal washes decreased by 10 and 14 dpi, respectively, which may explain the recurring aMPV-infections in the field. Ex vivo cultured spleen cells from aMPV-infected broilers released at 3 and 6 dpi higher levels of IFN-γ after stimulation with Concanavalin A as compared to virus-free birds. In agreement with studies in turkeys, aMPV-infected broilers showed a clear CD4+ T cell accumulation in the Harderian gland (HG) at 6 dpi (P<0.05). In contrast to other investigations in turkeys aMPV-infected broilers showed an increase in the number of CD8alpha+ cells at 6 dpi compared to virus-free birds (P<0.05). The numbers of local B cells in the Harderian gland were not affected by the infection. Both aMPV A and B induced up-regulation of interferon (IFN)-γ mRNA-expression in the nasal turbinates, while in the Harderian gland only aMPV-A induced enhanced IFN-γ expression at 3 dpi. The differences in systemic and local T cell and possibly natural killer cell activity in the HG between turkeys and chickens may explain the differences in aMPV-pathogenesis between these two species.

The influence of liposomal adjuvant on intranasal vaccination of chickens against Newcastle disease

The adjuvant effect of liposomes formulated with three phospholipids including phosphatidylcholine-liposomes (PC-Lip), phosphatidylserine-liposomes (PS-Lip), and stearylamine-liposomes (SA-Lip) was compared with virus alone using inactivated Newcastle disease virus (NDV) as a model antigen. The difference in adjuvanticity was evaluated using the haemagglutination-inhibition (HI) test, enzyme-linked immunosorbent assay, and a challenge study following intranasal inoculation of specific pathogen-free chickens. After two inoculations, a liposomal vaccine consisting of NDV in PC-Lip resulted in a significant increase in HI titre, up to 32-fold higher than a vaccine containing virus alone and 320-fold higher than a vaccine containing NDV in SA-Lip. PC-Lip also elicited a significant mucosal secretary immunoglobulin A response (P<0.05) in tracheal lavages and a serum IgG response (P<0.05). In response to viral challenge, all control animals died, whereas 90% of animals which received PC-Lip survived. The results suggest that PC-Lip may be suitable as an adjuvant for mucosal vaccination against NDV in chickens.

Protection levels of vaccinated pigeons (Columba livia) against a highly pathogenic Newcastle disease virus strain

The purposes of this study were to model a vaccination regimen for Newcastle disease virus (NDV) in pigeons, and to evaluate the susceptibility and behavior of vaccinated birds against a highly pathogenic NDV Brazilian strain. Antibody response was assessed by means of hemagglutination inhibition test (HI), and viral genome excretion by means of RT-PCR. Vaccinal strains (La Sota and Ulster) induced high antibody titers without any adverse effects, both in inoculated and in sentinel birds. A viral strain pathogenic for chickens did not produce clinical signs of the disease in experimentally infected pigeons. Only 4 out of 10 vaccinated pigeons shed NDV genome, and just for two days. Results confirmed the high infectivity of the vaccinal strains used, as all nonvaccinated pigeons showed antibody titers as high as those of vaccinated birds.

Adjuvants modulating mucosal immune responses or directing systemic responses towards the mucosa

In developing veterinary mucosal vaccines and vaccination strategies, mucosal adjuvants are one of the key players for inducing protective immune responses. Most of the mucosal adjuvants seem to exert their effect via binding to a receptor/or target cells and these properties were used to classify the mucosal adjuvants reviewed in the present paper: (1) ganglioside receptor-binding toxins (cholera toxin, LT enterotoxin, their B subunits and mutants); (2) surface immunoglobulin binding complex CTA1-DD; (3) TLR4 binding lipopolysaccharide; (4) TLR2-binding muramyl dipeptide; (5) Mannose receptor-binding mannan; (6) Dectin-1-binding ss 1,3/1,6 glucans; (7) TLR9-binding CpG-oligodeoxynucleotides; (8) Cytokines and chemokines; (9) Antigen-presenting cell targeting ISCOMATRIX and ISCOM. In addition, attention is given to two adjuvants able to prime the mucosal immune system following a systemic immunization, namely 1alpha, 25(OH)2D3 and cholera toxin.

Correlation between adjuvanticity and immunogenicity of cholera toxin B subunit in orally immunised young chickens. Brief report

The aim of the present study was to investigate whether the adjuvanticity of the cholera toxin B (CTB) subunit was correlated with its immunogenicity in young orally immunised chickens. Thirteen 15-day-old chickens were orally immunised with bovine serum albumin (BSA) glutaraldehyde coupled to CTB. The chicken antibody (IgG) concentrations against BSA and CTB, respectively, were quantified by ELISA. A significant positive correlation (r=0.66, n=39, p<0.001) between the concentrations of immunospecific antibodies with specificities against BSA and CTB, respectively, demonstrated that the adjuvanticity of CTB is correlated with its immunogenicity.

Refinement of Polyclonal Antibody Production by Combining Oral Immunization of Chickens with Harvest of Antibodies from the Egg Yolk

Polyclonal antibody production in mammals is generally associated with multiple injections of antigens and adjuvants and repeated blood sampling procedures. During the past 20 yr, the use of chickens instead of mammals for this purpose has increased. A major advantage of using birds is that the antibodies can be harvested from the egg yolk instead of serum, thus making blood sampling obsolete. In addition, the antibody productivity of an egg-laying hen is much greater than that of a similar sized mammal. This article focuses on the developments in oral immunization strategies for chickens that combined with the antibodies from the egg yolk, have great potential for active implementation of the three Rs (replacing, reducing, and refining the use of laboratory animals to the extent possible) in polyclonal antibody production schemes.

Immune response to a mucosally administered aflatoxin B1 vaccine

In the present study, a mucosal vaccine was used in an effort to elicit serum IgG and intestinal secretory IgA against the mycotoxin aflatoxin B1 (AFB) in chickens. AFB was coupled to carrier proteins (BSA and porcine thyroglobulin) for use as a vaccine and ELISA coating antigen, respectively. Seven-day-old broiler chicks were divided into groups of 10 and immunized with one of four vaccine preparations: 1) AFB-BSA conjugate alone, 2) AFB-BSA linked to the B subunit of the recombinant heat-labile enterotoxin of Escherichia coli (rLT-B), 3) AFB-BSA admixed with rLT-B, or 4) AFB-BSA mixed with cholera toxin (CT). Each vaccine preparation was administered perorally, intrarectally, or intraperitoneally, with a booster immunization given 2 wk later. Sera and feces were collected weekly and assayed using isotype specific ELISA. All three routes of immunization elicited significant serum IgG responses; however, the intraperitoneal route was strongest for all vaccine preparations tested. The serum IgG immune response to the AFB-BSA conjugate was enhanced by co-administration of rLT-B but not by covalent coupling to rLT-B or coadministration with CT. Secretory IgA anti-CT and anti-rLT-B antibodies were detected in fecal supernatants, but no anti-AFB responses could be detected. As all 12 treatment groups produced significant levels of serum IgG anti-AFB, any of these approaches, including oral administration without adjuvant, may afford the chicken some level of protection through simple immuno-interception of free AFB.

Intranasal immunization with formalin-inactivated virus vaccine induces a broad spectrum of heterosubtypic immunity against influenza A virus infection in mice

It has been known that influenza A virus infection induces a cross-protective immunity against infection by viruses with different subtypes of viral envelope proteins, hemagglutinin (HA) and neuraminidase (NA). This heterosubtypic immunity is generally mediated by cytotoxic T lymphocytes (CTL) reactive to specific epitopes in the viral internal proteins, such as nucleoprotein and matrix protein. By contrast, immunization with inactivated virus antigens has been thought to be unable to generate heterosubtypic immunity, since inactivated antigens do not usually induce CTL responses. However, we show that intranasal immunization with formalin-inactivated intact virus, but not ether-split vaccines, induced a broad spectrum of heterosubtypic protective immunity in mice. The protection may be mediated by the mucosal immune response, most likely secretory IgA antibodies to the viral proteins. This approach may overcome limitations in the efficacy of inactivated influenza vaccines and confer potent immunity to humans against viruses with new pandemic potential.

Development of a Virosome Vaccine for Newcastle Disease Virus

In an effort to protect chickens against Newcastle disease (ND), a nonreplicating virosome vaccine was produced by solubilization of Newcastle disease virus (NDV) with Triton X-100 followed by detergent removal with SM2 Bio-Beads. Biochemical analysis indicated that the NDV virosomes had similar characteristics as the parent virus and contained both the fusion and hemagglutinin-neuraminidase proteins. To target the respiratory tract, specific-pathogen-free chickens were immunized intranasally and intratracheally with the NDV virosome vaccine. This vaccine was compared with a standard NDV (LaSota) live-virus vaccine for commercial poultry. Seroconversion (> or = four fold increase in hemagglutination inhibition [HI] antibody titers) was achieved in all birds vaccinated with the virosome vaccine. Upon lethal challenge with a velogenic NDV strain (Texas GB), all birds receiving either vaccination method were protected against death. Antibody levels against NDV, as determined by enzyme-linked immunosorbent assay and HI titer, were comparable with either vaccine and increased after virus challenge. These results demonstrate the potential of virosomes as an effective tool for ND vaccination.

Immunoglobulin class distribution of systemic and mucosal antibody responses to Newcastle disease in chickens

In serum, tracheal wash fluid, and bile from chickens that were inoculated with live or inactivated Newcastle disease virus (NDV), the kinetics and immunoglobulin (Ig) class distribution of an antibody response were demonstrated. The Ig classes (IgM, IgG, and IgA) were captured using monoclonal antibodies (MAbs) in enzyme-linked immunosorbent assays (Ig-capture ELISA). The antibody specificity of the captured Ig was confirmed by binding of NDV. After inoculation with live virus, antibodies of the IgG and IgM classes were mainly found in serum. IgM was produced early from day 4 postexposure (PE) onward, IgG was detected later from day 7 PE onward, and in the tracheal wash fluid and bile, all three Ig classes were demonstrated. After inoculation of inactivated virus, a delayed response of all three classes was observed in serum, and only IgM and IgG were recognized in the tracheal fluid and bile. The type of vaccine and the mute of antigen entrance may have determined the immunoglobulin class produced. The Ig-capture ELISA assay developed in this study can be useful for evaluating various strategies to improve the efficacy of Newcastle disease vaccines and to study the evoked immune mechanisms.

Immunology of avian influenza virus: a review

Avian influenza virus can cause serious disease in a wide variety of birds and mammals, but its natural host range is in wild ducks, gulls, and shorebirds. Infections in poultry can be inapparent or cause respiratory disease, decreases in production, or a rapidly fatal systemic disease known as highly pathogenic avian influenza (HPAI). For the protection of poultry, neutralizing antibody to the hemagglutinin and neuraminidase proteins provide the primary protection against disease. A variety of vaccines elicit neutralizing antibody, including killed whole virus vaccines and fowl-pox recombinant vaccines. Antigenic drift of influenza viruses appears to be less important in causing vaccine failures in poultry as compared to humans. The cytotoxic T lymphocyte response can reduce viral shedding in mildly pathogenic avian influenza viruses, but provides questionable protection against HPAI. Influenza viruses can directly affect the immune response of infected birds, and the role of the Mx gene, interferons, and other cytokines in protection from disease remains unknown.

Immunity, vaccination and the avian intestinal tract

Defence of the intestinal mucosal surface from enteric pathogens is initially mediated by secretory IgA (SIgA). As oral immunization of non-replicating antigen induces minimal SIgA antibody titers, novel immunization strategies which selectively induce mucosal immune responses in mammals are now being assessed in chickens. The strategies reviewed include the route of antigen delivery, the incorporation of antigenic components in delivery vehicles, the inclusion of immunomodulators in the vaccine formula or in the diet, and manipulation of intestinal microflora. The differences in anatomical organization and immunological mechanisms between birds and mammals must be considered when manipulating avian intestinal immunity with the latest immunotechnologies developed for mammals. Our knowledge of the function and functioning of the avian mucosal system is discussed. Progress in our understanding of this system, the location of precursor IgA B cells and antigen sampling by these sites is not as advanced as knowledge of the mammalian system, highlighting the need for ongoing research into the avian application of novel vaccination strategies.

Avirulent Avian influenza virus as a vaccine strain against a potential human pandemic

In the influenza H5N1 virus incident in Hong Kong in 1997, viruses that are closely related to H5N1 viruses initially isolated in a severe outbreak of avian influenza in chickens were isolated from humans, signaling the possibility of an incipient pandemic. However, it was not possible to prepare a vaccine against the virus in the conventional embryonated egg system because of the lethality of the virus for chicken embryos and the high level of biosafety therefore required for vaccine production. Alternative approaches, including an avirulent H5N4 virus isolated from a migratory duck as a surrogate virus, H5N1 virus as a reassortant with avian virus H3N1 and an avirulent recombinant H5N1 virus generated by reverse genetics, have been explored. All vaccines were formalin inactivated. Intraperitoneal immunization of mice with each of vaccines elicited the production of hemagglutination-inhibiting and virus-neutralizing antibodies, while intranasal vaccination without adjuvant induced both mucosal and systemic antibody responses that protected the mice from lethal H5N1 virus challenge. Surveillance of birds and animals, particularly aquatic birds, for viruses to provide vaccine strains, especially surrogate viruses, for a future pandemic is stressed.

Vaccine delivery to animals

For many years vaccination of animals has been practiced to prevent infectious diseases using inactivated organisms or modified live organisms. The live vaccines were effective but lacked safety. The vaccines made with inactivated organisms required an adjuvant to induce an immune response that was not as effective as either the clinical disease or live vaccines. An 'ideal' vaccine would induce effective immunity specific for the type of infection, have long duration, require minimal or no boosters, have impeccable safety, would not induce adverse reactions, and be easy to administer. The desire to meet these criteria, and especially safety, has resulted in the development of vaccines that do not depend on the use of the viable disease agent. The emphasis on subunit or inactivated vaccines that meet the desired criteria of a perfect vaccine has resulted in a critical need for better adjuvants and delivery systems. This has resulted in a technological innovation revolution with development of a wide array of different technologies to generate effective vaccines. This review will describe the historical relevance of adjuvants used for parenterally administered inactivated/subunit vaccines as well as describe some of the exciting technological advances including adjuvants (ISCOMS), delivery systems (recombinant vectors, microparticles), and novel approaches (transgenic plants, naked DNA) that are currently being, or will be used in the future, in the search for better, more effective vaccines that meet the current and future needs of veterinary medicine.

Induction of a local and systemic immune response using cholera toxin as vehicle to deliver antigen in the lamina propria of the chicken intestine

In this study, the humoral mucosal immune response to a recombinant Eimeria antigen (Ea1A) was enhanced using cholera toxin (CT). Chickens were primed intra-intestinally with Ea1A either conjugated or not to CT. The local and systemic antibody responses to both Ea1A and CT were determined to find out whether the chickens could respond to CT and whether both antigens had reached the lamina propria. In addition the effects of CT on lamina propria leukocytes were examined. The results showed that chickens had receptors on the caecal epithelium that could bind CT. At day 7 after administration, the number of CD4+ and CD8+ T lymphocytes in the lamina propria of the caecum had increased, indicating that CT had a specific immunological effect. At this timepoint, anti-CT antibody containing cells were detected locally in the lamina propria of the caecum. In serum all antigen preparations containing CT induced IgM and IgG antibody titres specific for CT within 10 days after priming. In addition, the recombinant Ea1A antigen also induced serum responses when administered together with CT or conjugated to CT, thus both CT and the antigen had reached the lamina propria. Nevertheless, the Ea1A specific response was much higher in the primary response and after booster immunization when the antigen was conjugated to CT than when only mixed with CT. Therefore, we conclude that CT is a suitable adjuvant for intra-intestinal application in chickens, especially when the antigen is conjugated to it.