Locally produced mucosal IgG in chickens immunized with conventional vaccines for Newcastle disease virus

Comparative Study of the Immune Response Induced by an Argentinian Classical Strain of IBDV in Two Chicken Breeds

The hybrid chicken Negra INTA, which originated at the National Institute of Agricultural Technology (INTA), is the product of the cross between Barred Plymouth Rock females and Rhode Island Red males, and it is used as a laying hen for egg consumption. It has been characterized by productive parameters, but the characterization from an immunological perspective has not been done yet. Infectious bursal disease virus (IBDV) causes a highly contagious viral disease that affects the bursa of Fabricius. Although most chickens are regularly vaccinated against IBDV, this virus still generates negative impacts on production with significant economic losses. The aim of the present work was to compare the immune responses of the Negra INTA hybrid and the White Leghorn layer line to the infection with a field isolate of IBDV. Four-week-old chickens were infected with a single dose of IBDV and at 3, 5, 7, and 30 days postinfection (dpi), bursae were removed, and different parameters were evaluated. Results showed that the reduction of the bursa body (BB) ratio and the histopathological damage were maximum on day 7 postinfection (pi). The viral load was greater in the hybrid Negra INTA at 5 dpi. The humoral immune response between both breeds was similar, although more animals from the commercial line showed higher titers of neutralizing antibodies. Flow cytometry analysis revealed that Bu+ bursal lymphocytes reached a minimum at 7 dpi. Meanwhile, T cell infiltration measured by the percentage of CD3+, CD4+, and CD8+ cells in the bursa was at its maximum at 5 dpi. To our knowledge, this work describes for the first time the pathogenesis and the immune response caused by an Argentinian IBDV isolate in two different chicken lines.

Comparative Safety, Immunogenicity, and Efficacy of CEF Cell-Based and DF-1 Cell Line Adapted Infectious Bursal Disease Vaccines in Specific-Pathogen-Free Chickens

Infectious bursal disease (IBD) is an immunosuppressive and economically important disease of young chickens caused by infectious bursal disease virus (IBDV). The National Veterinary Institute (Bishoftu, Ethiopia) produces intermediate IBDV vaccine using primary chicken embryo fibroblast (CEF) cells, a method with technical and economical cumbersome. This study assessed the safety, immunogenicity, and efficacy of DF-1 cell line-adapted IBDV LC–75 vaccine strain in reference to the CEF-based vaccine. Confluent monolayer of DF-1 cells was infected with IBDV and cells with cytopathic effects were passaged until 3^rd passage. Viral growth was confirmed using a one-step RT-PCR targeting IBDV VP2 gene. Viral titer increased from 1^st passage through 3^rd passage. Safety was assessed in 30 specific-pathogen-free chickens (15 chickens/group) injected with 10-fold field dose of each vaccine intraocularly and monitored for 21 days. For immunogenicity and efficacy, 60 specific-pathogen-free chickens were grouped into 3 (20 chickens/group). First and 2^nd group received DF-1 cell and CEF-based IBDV vaccines, respectively. The 3^rd group served as unvaccinated control. Antibody response was measured using iELISA. Chickens were challenged 4 weeks postvaccination with very virulent IBDV (vvIBDV) intraocularly and followed-up for 10 days. Vaccination did not cause any adverse reactions during the 21 days of follow-up. In addition, both vaccines induced higher antibody titer 14 and 24 days-post-vaccination as compared to unvaccinated controls (p < 0.05). Moreover, DF-1 and CEF-based IBDV LC–75 vaccines rendered a complete protection against vvIBDV. Contrarily, morbidity and mortality in unvaccinated chickens was 50% and 30%, respectively. The results indicated that DF-1 and CEF cell-based IBDV vaccines are comparably immunogenic and efficacious. Therefore, DF-1 cell-line can be considered an affordable and convenient alternative to the CEF-based approach. The suitability of DF-1 cells to grow other IBDV strains and safety of these vaccines on bursa of Fabricius should further be investigated.

Carboxymethylated and acetylated xerogel derivatives of Plectranthus esculentus starch protect Newcastle disease vaccines against cold chain failure

Developing vaccine stabilizers from local natural sources is desirable especially if the stabilizer would enhance the ability of the antigen to withstand frequent failures in cold chains. The study was undertaken to formulate immunogenic live Newcastle Disease (ND) LaSota vaccines stabilized with modified native starches for use at cold and ambient temperatures and to assess the immunogenicity of the starch stabilized vaccines in vaccinated chickens. Native starch extracted from the tubers of Plectranthus esculentus (Family, Lamiaceae) was modified by carboxymethylation and acetylation/xerogel formation and used as vaccine stabilizers of ND LaSota virus with/without buffers/bulking excipients. Cold Chain Failure (CCF) was simulated by storing the vaccines at 5 ± 2 °C for one month then at 37 ± 1 °C for 96 h. The stability of the samples were evaluated in comparison with peptone stabilized ND vaccines using pH, residual moisture, XRD, reconstitution time, mean embryo infective dose (EID50) and haemagglutination (HA) tests. Haemagglutination inhibition was used to evaluate the efficacy of the vaccines in conferring positive serum antibody titers (≥2³ log₂) in vaccine-naïve 2-week old broilers that were orally administered a single dose of the vaccines kept at 37 ± 1 °C for 96 h and bled weekly over four weeks. Temperature, pH, moisture content and amorphousness impacted vaccine stability. Peptone stabilized vaccines were significantly less stable and most affected by temperature changes with 1.2log₁₀EID50 loss while buffered/bulked trehalose, carboxymethylated and acetylated/xerogelized starch stabilized vaccines were most stable (0.2-0.5log₁₀EID50 loss in titer) after 96 h in CCF. Buffered trehalose stabilized vaccine (TVB) had lower HA titres than peptone and starch stabilized vaccines containing D-mannitol and Na₂HPO₄. Antibody titres of vaccinated broilers were between 3.3 ± 1.398 and 8.35 ± 2.678. All the vaccines were immunogenic (HI ≥ 2³) and developed HI titres (≥2⁴) considered to be protective. Carboxymethylated and acetylated/xerogel derivatives of P. esculentus starch have a great potential as vaccine stabilizers especially in areas prone to CCF.

Chitosan Biomedical Applications for the Treatment of Viral Disease: A Data Mining Model Using Bibliometric Predictive Intelligence

Chitosan has attracted increasing attention from researchers in the pharmaceutical and biomedical fields as a potential agent for the prevention and treatment of infectious diseases. However, identifying the development of emerging technologies related to this biopolymer is difficult, especially for newcomers trying to understand the research streams. In this work, we designed and implemented a research process based on a bibliometric predictive intelligence model. Our aim is to glean detailed scientific and technological trends through an analysis of publications that include certain word phrases and related research areas. Cross correlation, factor mapping, and the calculation of “emergent” scores were also used. A total of 1,612 scientific papers on chitosan technology related to viral disease treatment published between 2010 and 2020 were retrieved from the Web of Science. Results from the keyword modelling quantitatively highlight three major frontier research and development topic groups: drug delivery and adjuvants, vaccines and immune response, and tissue engineering. More specifically, the emergent scores show that much of the chitosan-based treatment for viral diseases is in the in vitro stage of development. Most chitosan applications are in pharmacology/pharmacy and immunology. All results were confirmed by experts in the field, which indicates that the validated process can be applied to other fields of interest.

Protection of Chickens with Maternal Immunity Against Avian Influenza Virus (AIV) by Vaccination with a Novel Recombinant Newcastle Disease Virus Vector

Newcastle disease virus (NDV) vectors expressing avian influenza virus (AIV) hemagglutinin of subtype H5 protect specific pathogen-free chickens from Newcastle disease and avian influenza. However, maternal AIV antibodies (AIV-MDA+) are known to interfere with active immunization by influencing vaccine virus replication and gene expression, resulting in inefficient protection. To overcome this disadvantage, we inserted a transgene encoding a truncated soluble hemagglutinin (HA) in addition to the gene encoding membrane-bound HA from highly pathogenic avian influenza virus (HPAIV) H5N1 into lentogenic NDV Clone 30 genome (rNDVsolH5_H5) to overexpress H5 antigen. Vaccination of 3-wk-old AIV-MDA+ chickens with rNDVsolH5_H5 and subsequent challenge infection with HPAIV H5N1 3 wk later resulted in 100% protection. Vaccination of younger chickens with higher AIV-MDA levels 1 and 2 wk after hatch resulted in protection rates of 40% and 85%, respectively. However, all vaccinated chickens showed strongly reduced shedding of challenge virus compared with age-matched, nonvaccinated control chickens. All control chickens succumbed to the HPAIV infection with a grading in disease progression between the three groups, indicating the influence of AIV-MDAs even at a low level. Furthermore, the shedding and serologic data gathered after immunization indicate sufficient replication of the vaccine virus, which leads to the assumption that lower protection rates in younger AIV-MDA+ chickens are caused by an H5 antigen-specific block and not by the interference of the AIV-MDA and the vaccine virus itself. In summary, solid protective efficacy and reduced virus transmission were achieved in 3-wk-old AIV-MDA+ chickens, which is relevant especially in regions endemically infected with HPAIV H5N1.

Turkey humoral and cell-mediated immune responses to a Newcastle viscerotropic vaccine and its association with major histocompatibility complex

Immune responses to vaccines are mainly influenced by the nature of vaccines and host variation in response to vaccination. In this study we aimed to investigate turkey humoral and cell-mediated immune responses to a Newcastle viscerotropic vaccine and its association with major histocompatibility complex (MHC). Turkeys were vaccinated with Villegas–Glisson/University of Georgia (VG/GA) attenuated vaccine against Newcastle disease. The stimulation index of lymphocyte proliferation and antigen-specific local secretory IgA responses in bile, duodenum, ileum, as well as serum IgY and IgA responses were analysed by enzyme-linked immunosorbent assay. The turkey MHC class II B locus was selected as candidate gene for detection of associations with cellular and humoral immune responses. Significant differences were observed between both cellular and humoral responses of vaccinated and unvaccinated groups. A significant positive correlation was also found between ND specific IgY and ND specific IgA titres in serum, intestine (duodenum and ileum) and trachea. Moreover, the correlation between specific IgA titres in ileum and specific bile, duodenum and trachea was positively significant. High resolution melting analysis (HRM) was used to genotype MHC class II B exon 2. Eight melting profiles (A-G) were identified, among which, profile G showed a significant association with cellular response. The profile B revealed significant association with total IgA titres in serum and ileum. These findings help our understanding of the association of turkey MHC types with immune responses. Further correlation analysis between serum and mucosal antibody titres demonstrated that the levels of IgY and IgA in serum can give an impression about the levels of secretory IgA and situation of mucosal immunity. Based on the significant effects, ND specific IgY in serum appears to be a promising indirect marker for specific IgA in serum and trachea.

Induction of Mucosal Humoral Immunity by Subcutaneous Injection of an Oil-emulsion Vaccine against Salmonella enterica subsp. enterica serovar Enteritidis in Chickens

Salmonella enterica subsp. enterica serovar Enteritidis (SE) is one of the major causes of food poisoning. Much effort has been made to develop a vaccine for the prevention of SE colonization and infection in poultry. However, the effect of inactivated whole-cell SE vaccines on the bacterial attachment has not been clarified. This study investigated the immune responses to a killed whole-cell SE vaccine in chickens and the effect of vaccination on the bacterial attachment of SE to cultured Vero cells. A 1 ml dose of 10⁸–10⁹ CFU viable SE bacterial cells was orally administered to chickens at 4 weeks or 10 months post vaccination. The number (CFU) of SE in 1 g of cecal droppings was counted on day 6 after administration. The SE CFUs were significantly lower (p < 0.05) in the vaccinated chickens, not only at 4 weeks but also at 10 months after vaccination, than in the unvaccinated control chickens. Anti-SE IgG and anti-SE IgA were detected using enzyme-linked immunosorbent assay (ELISA) in serum and intestinal and oviduct fluid samples from vaccinated chickens. Adhesion of heat-killed SE cells to Vero cells was reduced by pre-treatment of the bacteria by the vaccinated chicken-derived intestinal fluid, indicating the potential of the vaccine-induced antibody to prevent SE adhesion to epithelial cell surfaces.

Quantification and phenotypic characterisation of peripheral IFN-γ producing leucocytes in chickens vaccinated against Newcastle disease

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An avian ICS assay for detection of chIFN-γ was established.

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Commercially available chIFN-γ antibodies were evaluated using tranfected CHO cells.

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Functional T cell responses were addressed in NDV vaccination study.

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Circulating T cells producing IFN-γ were quantified and phenotyped by flow cytometry.

The aim of this study was to optimise and evaluate an intracellular cytokine staining (ICS) assay for assessment of T cell IFN-γ responses in chickens vaccinated against Newcastle disease (ND). We aimed to validate currently available antibodies to chicken IFN-γ using transfected CHO cells. Moreover, this ICS assay was evaluated for use to detect mitogen and antigen induced IFN-γ production in chicken peripheral blood leucocytes.

Chickens from an inbred white leghorn line containing two MHC haplotypes, B19 and B21, were divided into three experimental groups; one group was kept as naive controls, one group was vaccinated intramuscularly twice with a commercial inactivated ND virus (NDV) vaccine, and the last group was vaccinated orally twice with a commercial live attenuated NDV vaccine. PBMC were ex vivo stimulated with ConA or with NDV antigen. The ICS assay was used to determine the phenotype and frequency of IFN-γ positive cells. ConA stimulation induced extensive IFN-γ production in both CD3⁺TCRγδ⁺ (γδ T cells) cells and CD3⁺TCRγδ⁻ cells (αβ T cells), but no significant differences were observed between the experimental groups. Furthermore, a large proportion of the IFN-γ producing cells were CD3⁻ indicating that other cells than classic T cells, secreted this cytokine. NDV antigen stimulation induced IFN-γ production but to a lower extent than ConA and with a large variation between individuals. The CD3⁺TCR1γδ⁻CD8α⁺ (CTL) population produced the highest NDV specific IFN-γ responses, with significantly elevated levels of IFN-γ producing cells in the B19 chickens vaccinated orally with live attenuated NDV vaccine. This was not the case in the B21 animals, indicating a haplotype restricted variation. In contrast, the CD3⁺TCR1γδ⁻CD4⁺ (Th) population did not show a significant increase in IFN-γ production in NDV stimulated samples which was in part due to a high number of IFN-γ producing cells after incubation with medium alone. In conclusion, an ICS assay for phenotyping of IFN-γ producing chicken leukocytes was set up that proved useful in identifying cytokine producing cells upon either mitogen or antigen-specific stimulation.

IgA response and protection following nasal vaccination of chickens with Newcastle disease virus DNA vaccine nanoencapsulated with Ag@SiO2 hollow nanoparticles

Newcastle disease caused by ND virus (NDV) is a highly contagious disease of birds. Vaccine for effective protection of poultry animals from NDV infection is urgently needed. Mucosal immunity plays a very important role in the antiviral immune response. In this study, a NDV F gene-containing DNA vaccine encapsulated in Ag@SiO2 hollow nanoparticles (pFDNA-Ag@SiO2-NPs) with an average diameter of 500 nm were prepared to assess the mucosal immune response. These nanoparticles exhibited low cytotoxicity and did not destroy the bioactivity of plasmid DNA, which could be expressed in vitro. The plasmid DNA was sustainably released after an initial burst release. In vivo immunization showed that the intranasal immunization of chickens with pFDNA-Ag@SiO2-NPs induced high titers of serum antibody, significantly promoted lymphocyte proliferation and induced higher expression levels of IL-2 and IFN-γ in a dose-dependent manner. These results indicated that the Ag@SiO2 hollow nanoparticles could serve as an efficient and safe delivery carrier for NDV DNA vaccine to induce mucosal immunity. This study has provided promising results for the further development of mucosal vaccines encapsulated in inorganic nanoparticles.

Development, characterization and optimization of a new suspension chicken-induced pluripotent cell line for the production of Newcastle disease vaccine

Traditionally, substrates for production of viral poultry vaccines have been embryonated eggs or adherent primary cell cultures. The difficulties and cost involved in scaling up these substrates in cases of increased demand have been a limitation for vaccine production. Here, we assess the ability of a newly developed chicken-induced pluripotent cell line, BA3, to support replication and growth of Newcastle disease virus (NDV) LaSota vaccine strain. The characteristics and growth profile of the cells were also investigated. BA3 cells could grow in suspension in different media to a high density of up to 7.0 × 10(6) cells/mL and showed rapid proliferation with doubling time of 21 h. Upon infection, a high virus titer of 1.02 × 10(8) EID50/mL was obtained at 24 h post infection using a multiplicity of infection (MOI) of 5. In addition, the cell line was shown to be free of endogenous and exogenous Avian Leukosis viruses, Reticuloendotheliosis virus, Fowl Adenovirus, Marek's disease virus, and several Mycoplasma species. In conclusion, BA3 cell line is potentially an excellent candidate for vaccine production due to its highly desirable industrially friendly characteristics of growing to high cell density and capability of growth in serum free medium.

Newcastle disease virus vaccine encapsulated in biodegradable nanoparticles for mucosal delivery of a human vaccine

An overwhelming number of medicines on the market are oral medicine with the disadvantage of lower bioavailability universally. Newcastle disease (ND) has become a serious disease that threatens the poultry industries in many countries, and there are no treatments available for ND. The biodegradable materials could be surface modified and protect antigen or DNA from damage. Furthermore, nanoparticles are also a potential drug delivery with proper size. However, Newcastle disease virus (NDV) vaccines encapsulated in nanoparticles were widely used due to their proved a high safety and induced quicker and better mucosal and humoral immune responses. Here we review the results of mucosal immune delivery system for ND. Due to the safety, low toxicity, and better immunogenicity of the mucosal immune delivery system, our studies provide a clearly view that used the biodegradable materials to research and develop the human vaccines to save more patients' lives. These promising results provide a foundation for testing the approach in humans.

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.

Effects of Newcastle disease virus vaccine antibodies on the shedding and transmission of challenge viruses

Different genotypes of avian paramyxovirus serotype-1 virus (APMV-1) circulate in many parts of the world. Traditionally, Newcastle disease virus (NDV) is recognized as having two major divisions represented by classes I and II, with class II being further divided into sixteen genotypes. Although all NDV are members of APMV-1 and are of one serotype, antigenic and genetic diversity is observed between the different genotypes. Reports of vaccine failure from many countries and reports by our lab on the reduced ability of classical vaccines to significantly decrease viral replication and shedding have created renewed interest in developing vaccines formulated with genotypes homologous to the virulent NDV (vNDV) circulating in the field. We assessed how the amount and specificity of humoral antibodies induced by inactivated vaccines affected viral replication, clinical protection and evaluated how non-homologous (heterologous) antibody levels induced by live NDV vaccines relate to transmission of vNDV. In an experimental setting, all inactivated NDV vaccines protected birds from morbidity and mortality, but higher and more specific levels of antibodies were required to significantly decrease viral replication. It was possible to significantly decrease viral replication and shedding with high levels of antibodies and those levels could be more easily reached with vaccines formulated with NDV of the same genotype as the challenge viruses. However, when the levels of heterologous antibodies were sufficiently high, it was possible to prevent transmission. As the level of humoral antibodies increase in vaccinated birds, the number of infected birds and the amount of vNDV shed decreased. Thus, in an experimental setting the effective levels of humoral antibodies could be increased by (1) increasing the homology of the vaccine to the challenge virus, or (2) allowing optimal time for the development of the immune response.

Immune responses of poultry to Newcastle disease virus

Newcastle disease (ND) remains a constant threat to poultry producers worldwide, in spite of the availability and global employment of ND vaccinations since the 1950s. Strains of Newcastle disease virus (NDV) belong to the order Mononegavirales, family Paramyxoviridae, and genus Avulavirus, are contained in one serotype and are also known as avian paramyxovirus serotype-1 (APMV-1). They are pleomorphic in shape and are single-stranded, non-segmented, negative sense RNA viruses. The virus has been reported to infect most orders of birds and thus has a wide host range. Isolates are characterized by virulence in chickens and the presence of basic amino acids at the fusion protein cleavage site. Low virulent NDV typically produce subclinical disease with some morbidity, whereas virulent isolates can result in rapid, high mortality of birds. Virulent NDV are listed pathogens that require immediate notification to the Office of International Epizootics and outbreaks typically result in trade embargos. Protection against NDV is through the use of vaccines generated with low virulent NDV strains. Immunity is derived from neutralizing antibodies formed against the viral hemagglutinin and fusion glycoproteins, which are responsible for attachment and spread of the virus. However, new techniques and technologies have also allowed for more in depth analysis of the innate and cell-mediated immunity of poultry to NDV. Gene profiling experiments have led to the discovery of novel host genes modulated immediately after infection. Differences in virus virulence alter host gene response patterns have been demonstrated. Furthermore, the timing and contributions of cell-mediated immune responses appear to decrease disease and transmission potential. In view of recent reports of vaccine failure from many countries on the ability of classical NDV vaccines to stop spread of disease, renewed interest in a more complete understanding of the global immune response of poultry to NDV will be critical to developing new control strategies and intervention programs for the future.

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.

Expression of a secreted version of the hemagglutinin-neuraminidase glycoprotein of Newcastle disease virus

The hemagglutinin-neuraminidase (HN) glycoprotein of Newcastle disease virus (NDV) constitutes, together with the fusion glycoprotein, the main surface antigen of this avian pathogen, which causes a highly contagious disease, relevant economically worldwide. The purpose of this work was to obtain the HN glycoprotein as a soluble antigen in culture supernatants of recombinant baculovirus-infected Spodoptera frugiperda (Sf9) cells and to evaluate its application to the development of a recombinant enzyme-linked immunosorbent assay (rELISA) for the analysis of chicken sera. A transfer vector for baculovirus containing the sequence of a melittin signal peptide was constructed and the sequence coding for HN protein without its own signal peptide was cloned. The recombinant protein was secreted and recovered easily from the culture medium of Sf9-infected cells. The recombinant protein was evaluated as antigen for ELISA coating the plates with the recovered HN using 79 positive and 142 negative samples. The Cohen kappa value resulted 0.91, indicating excellent agreement between the rELISA and the hemagglutinin inhibition tests. The rELISA was also compared with a commercial ELISA, finding high levels of agreement between both assays. The present results show that the cloning strategy developed yielded the HN protein free in the cell culture supernatant and that the recombinant protein retained its reactivity with anti-NDV HN antibodies in chicken sera.

Probiotic bacteria and intestinal epithelial barrier function

The intestinal tract is a diverse microenvironment where more than 500 species of bacteria thrive. A single layer of epithelium is all that separates these commensal microorganisms and pathogens from the underlying immune cells, and thus epithelial barrier function is a key component in the arsenal of defense mechanisms required to prevent infection and inflammation. The epithelial barrier consists of a dense mucous layer containing secretory IgA and antimicrobial peptides as well as dynamic junctional complexes that regulate permeability between cells. Probiotics are live microorganisms that confer benefit to the host and that have been suggested to ameliorate or prevent diseases including antibiotic-associated diarrhea, irritable bowel syndrome, and inflammatory bowel disease. Probiotics likely function through enhancement of barrier function, immunomodulation, and competitive adherence to the mucus and epithelium. This review summarizes the evidence about effects of the many available probiotics with an emphasis on intestinal barrier function and the mechanisms affected by probiotics.

Potential use of the hemagglutinin-neuraminidase glycoprotein of Newcastle disease virus expressed in Rachiplusia nu larvae as an immunogen for chickens

The hemagglutinin-neuraminidase glycoprotein of Newcastle disease virus (NDV) was obtained as a recombinant antigen in Rachiplusia nu larvae. When it was used as an immunogen in chickens, a solid immune response, including neutralizing antibodies, was detected, demonstrating the potential use of this simple and economic strategy in the design of recombinant anti-NDV vaccines.