The carboxyl-terminal 120-residue polypeptide of infectious bronchitis virus nucleocapsid induces cytotoxic T lymphocytes and protects chickens from acute infection

Antiviral effect of palmatine against infectious bronchitis virus through regulation of NF-κB/IRF7/JAK-STAT signalling pathway and apoptosis

1. Infectious bronchitis virus (IBV), a gamma-coronavirus, can infect chickens of all ages and leads to an acute contact respiratory infection. This study evaluated the anti-viral activity of palmatine, a natural non-flavonoid alkaloid, against IBV in chicken embryo kidney (CEK) cells.2. The half toxic concentration (CC50) of palmatine was 672.92 μM, the half inhibitory concentration (IC50) of palmatine against IBV was 7.76 μM and the selection index (SI) was 86.74.3. Mode of action assay showed that palmatine was able to directly inactivate IBV and inhibited the adsorption, penetration and intracellular replication of IBV.4. Palmatine significantly upregulated TRAF6, TAB1 and IKK-β compared with the IBV-infected group, leading to the increased expressions of pro-inflammatory cytokines IL-1β and TNF-α in the downstream NF-κB signalling pathway.5. Palmatine significantly up-regulated the levels of MDA5, MAVS, IRF7, IFN-α and IFN-β in the IRF7 pathway, inducing type I interferon production. It up-regulated the expression of 2'5'-oligoadenylate synthase (OAS) in the JAK-STAT pathway.6. IBV infection induced cell apoptosis and palmatine-treatment delayed the process of apoptosis by regulation of the expression of apoptosis-related genes (BAX, BCL-2, CASPASE-3 and CASPASE-8).7. Palmatine could exert anti-IBV activity through regulation of NF-κB/IRF7/JAK-STAT signalling pathways and apoptosis, providing a theoretical basis for the utilisation of palmatine to treat IBV infection.

Advances in Poultry Vaccines: Leveraging Biotechnology for Improving Vaccine Development, Stability, and Delivery

With the rapidly increasing demand for poultry products and the current challenges facing the poultry industry, the application of biotechnology to enhance poultry production has gained growing significance. Biotechnology encompasses all forms of technology that can be harnessed to improve poultry health and production efficiency. Notably, biotechnology-based approaches have fueled rapid advances in biological research, including (a) genetic manipulation in poultry breeding to improve the growth and egg production traits and disease resistance, (b) rapid identification of infectious agents using DNA-based approaches, (c) inclusion of natural and synthetic feed additives to poultry diets to enhance their nutritional value and maximize feed utilization by birds, and (d) production of biological products such as vaccines and various types of immunostimulants to increase the defensive activity of the immune system against pathogenic infection. Indeed, managing both existing and newly emerging infectious diseases presents a challenge for poultry production. However, recent strides in vaccine technology are demonstrating significant promise for disease prevention and control. This review focuses on the evolving applications of biotechnology aimed at enhancing vaccine immunogenicity, efficacy, stability, and delivery.

Genetic and immunological characterization of commercial infectious bronchitis virus vaccines used in Korea

The aim of the study was to investigate the genetic and immunogenic features of commercial vaccines against infectious bronchitis virus (IBV), which is a major contagious pathogen of poultry. Although numerous vaccines have been developed based on the genetic characteristics of field strains, the continual emergence of variants decreases vaccine efficacy and cross-protection. To address this issue, we compared the S1 gene sequences of three IBV vaccines commercially available in Korea with those of various field isolates. Phylogenetic analysis showed that the vaccine strains clustered into two different lineages. Comparison of commercial vaccines with their parental viruses showed that most of the genetic variability occurred around hypervariable regions (HVRs). Conversely, antigenic stimulation with commercial vaccines and regional IBV variants was not sufficient to alter major immune cell phenotypes. Our study suggests that vaccines should be selected carefully based on their genetic background because genetic variability can affect the antigenicity of vaccines and host immune responses.

Development of an Indirect ELISA for the Detection of SARS-CoV-2 Antibodies in Cats

Companion animals are susceptible to a variety of coronaviruses, and recent studies show that felines are highly susceptible to SARS-CoV-2 infection. RT-PCR diagnostic is currently the method of choice to detect the presence of SARS-CoV-2-specific viral nucleic acids in animal samples during an active infection; however, serological assays are critical to determine whether animals were exposed to the virus and to determine the seroprevalence of SARS-CoV-2-specific antibodies in a defined population. In this study, we utilized recombinant nucleocapsid (N) protein and the receptor-binding domain (RBD) of the spike protein of SARS-CoV-2 expressed in E. coli (N) and mammalian cells (N, RBD) to develop indirect ELISA (iELISA) tests using well-characterized SARS-CoV-2-positive and -negative cat serum panels from previous experimental cat challenge studies. The optimal conditions for the iELISA tests were established based on checkerboard dilutions of antigens and antibodies. The diagnostic sensitivity for the detection of feline antibodies specific for the N or RBD proteins of the iELISA tests was between 93.3 and 97.8%, respectively, and the diagnostic specificity 95.5%. The iELISAs developed here can be used for high-throughput screening of cat sera for both antigens. The presence of SARS-CoV-2-specific antibodies in a BSL-2 biocontainment environment, unlike virus neutralization tests with live virus which have to be performed in BSL-3 laboratories.

Nationwide Surveillance for Infectious Bronchitis Virus in South Korea from 2020 to 2021

Infectious bronchitis virus (IBV) is a major pathogen in poultry. The genotypes of IBV vary considerably, and their antigenicity may differ. Nationwide surveillance in South Korea was performed to determine the prevalence and distribution of IBV and its genotypes. By both active and passive surveillance, a total of 939 samples were collected and tested for IBV detection by pathogen-specific reverse transcriptase-PCR. IBV RNA-positive samples were inoculated in embryonated eggs for virus isolation. IBV was genotyped and analyzed phylogenetically based on a partial nucleotide sequence of the S1 gene. A total of 114 IBV strains were isolated; 34 (30.9%) of the 110 samples obtained by passive surveillance, and 80 (9.7%) of the 829 samples obtained by active surveillance, were positive. Most IBVs in both groups were isolated from broilers. Five genotypes (QX-like, B4-like, KM91-like, K40/09-like, and 20AD17-like) were observed in South Korea, with the QX-like genotype being the most common, and the 20AD17-like genotype being a novel genotype. These findings will help to maximize protection against IBV infection by providing a reference for the selection of an avian vaccine for IBV in South Korea.

Development of a Nanoparticle Multiepitope DNA Vaccine against Virulent Infectious Bronchitis Virus Challenge

To develop a safe and effective nanoparticle (NP) multiepitope DNA vaccine for controlling infectious bronchitis virus (IBV) infection, we inserted the multiepitope gene expression box SBNT into a eukaryotic expression vector pcDNA3.1(+) to construct a recombinant plasmid pcDNA/SBNT. The NP multiepitope DNA vaccine pcDNA/SBNT-NPs were prepared using chitosan to encapsulate the recombinant plasmid pcDNA/SBNT, with a high encapsulation efficiency of 94.90 ± 1.35%. These spherical pcDNA/SBNT-NPs were 140.9 ± 73.2 nm in diameter, with a mean ζ potential of +16.8 ± 4.3 mV. Our results showed that the chitosan NPs not only protected the plasmid DNA from DNase degradation but also mediated gene transfection in a slow-release manner. Immunization with pcDNA/SBNT-NPs induced a significant IBV-specific immune response and partially protected chickens against homologous IBV challenge. Therefore, the chitosan NPs could be a useful gene delivery system, and NP multiepitope DNA vaccines may be a potential alternative for use in the development of a novel, safe, and effective IBV vaccine.

Identification of Novel T-Cell Epitopes on Infectious Bronchitis Virus N Protein and Development of a Multi-epitope Vaccine

Cellular immune responses play a key role in the control of viral infection. The nucleocapsid (N) protein of infectious bronchitis virus (IBV) is a major immunogenic protein that can induce protective immunity. To screen for potential T-cell epitopes on IBV N protein, 40 overlapping peptides covering the entirety of the N protein were designed and synthesized. Four T-cell epitope peptides were identified by gamma interferon (IFN-γ) enzyme-linked immunosorbent spot (ELISpot), intracellular cytokine staining, and carboxyfluorescein succinimidyl ester (CFSE) lymphocyte proliferation assays; among them, three peptides (N_211-230, N_271-290, and N_381-400) were cytotoxic T lymphocyte (CTL) epitopes, and one peptide (N_261-280) was a dual-specific T-cell epitope, which can be recognized by both CD8⁺ and CD4⁺ T cells. Multi-epitope gene transcription cassettes comprising four neutralizing epitope domains and four T-cell epitope peptides were synthesized and inserted into the genome of Newcastle disease virus strain La Sota between the P and M genes. Recombinant IBV multi-epitope vaccine candidate rLa Sota/SBNT was generated via reverse genetics, and its immune protection efficacy was evaluated in specific-pathogen-free chickens. Our results show that rLa Sota/SBNT induced IBV-specific neutralizing antibody and T-cell responses and provided significant protection against homologous and heterologous IBV challenge. Thus, the T-cell epitope peptides identified in this study could be good candidates for IBV vaccine development, and recombinant Newcastle disease virus-expressing IBV multi-epitope genes represent a safe and effective vaccine candidate for controlling infectious bronchitis. IMPORTANCE T-cell-mediated immune responses are critical for the elimination of IBV-infected cells. To screen conserved T-cell epitopes in the IBV N protein, 40 overlapping peptides covering the entirety of the N protein were designed and synthesized. By combining IFN-γ ELISpot, intracellular cytokine staining, and CFSE lymphocyte proliferation assays, we identified three CTL epitopes and one dual-specific T-cell epitope. The value of T-cell epitope peptides identified in the N protein was further verified by the design of an IBV multi-epitope vaccine. Results show that IBV multi-epitope vaccine candidate rLa Sota/SBNT provided cross protection against challenges with a QX-like or a TW-like IBV strain. So, T-cell-mediated immune responses play an important role in the control of viral infection, and conserved T-cell epitopes serve as promising candidates for use in multi-epitope vaccine construction. Our results provide a new perspective for the development of a safer and more effective IBV vaccine.

Path to Success and Future Impact of Nucleic Acid Vaccines: DNA and mRNA

The rapid development of mRNA vaccines for COVID-19 has both astonished the world and raised concerns about their safety, perhaps because many people do not realize the decades’ long efforts for nucleic acid vaccines, both mRNA and DNA vaccines, including the licensure of several veterinary DNA vaccines. This manuscript traces the milestones for nucleic acid vaccine research and development (R&D), with a focus on the immune and safety issues they both raised and answered. The characteristics of the two entities are compared, demonstrating the similarities and differences between them, the advantages and disadvantages, which might lead toward using one or the other technology for different indications. In addition, as the SARS-CoV-2 pandemic has once again highlighted the importance of One Health, that is, the interactions between animal and human pathogens, focus will also be given to how DNA vaccine utilization and studies both in large domestic animals and in wildlife pave the way for more integrated approaches for vaccines to respond quickly to, and prevent, the global impacts of emerging diseases.

The Key Role of Nucleic Acid Vaccines for One Health

The ongoing SARS-CoV-2 pandemic has highlighted both the importance of One Health, i.e., the interactions and transmission of pathogens between animals and humans, and the potential power of gene-based vaccines, specifically nucleic acid vaccines. This review will highlight key aspects of the development of plasmid DNA Nucleic Acid (NA) vaccines, which have been licensed for several veterinary uses, and tested for a number of human diseases, and will explain how an understanding of their immunological and real-world attributes are important for their efficacy, and how they helped pave the way for mRNA vaccines. The review highlights how combining efforts for vaccine development for both animals and humans is crucial for advancing new technologies and for combatting emerging diseases.

Immunodominant regions prediction of nucleocapsid protein for SARS-CoV-2 early diagnosis: a bioinformatics and immunoinformatics study

COVID-19 caused by SARS-CoV-2 is sweeping the world and posing serious health problems. Rapid and accurate detection along with timely isolation is the key to control the epidemic. Nucleic acid test and antibody-detection have been applied in the diagnosis of COVID-19, while both have their limitations. Comparatively, direct detection of viral antigens in clinical specimens is highly valuable for the early diagnosis of SARS-CoV-2. The nucleocapsid (N) protein is one of the predominantly expressed proteins with high immunogenicity during the early stages of infection. Here, we applied multiple bioinformatics servers to forecast the potential immunodominant regions derived from the N protein of SARS-CoV-2. Since the high homology of N protein between SARS-CoV-2 and SARS-CoV, we attempted to leverage existing SARS-CoV immunological studies to develop SARS-CoV-2 diagnostic antibodies. Finally, N_229-269, N_349-399, and N_405-419 were predicted to be the potential immunodominant regions, which contain both predicted linear B-cell epitopes and murine MHC class II binding epitopes. These three regions exhibited good surface accessibility and hydrophilicity. All were forecasted to be non-allergen and non-toxic. The final construct was built based on the bioinformatics analysis, which could help to develop an antigen-capture system for the early diagnosis of SARS-CoV-2.

Development and evaluation of a serological test for diagnosis of COVID-19 with selected recombinant spike proteins

Serological test is a valuable diagnostic tool for coronavirus disease 2019 (COVID-19). However, considerable improvements to these tests are needed, especially in the detection sensitivity. In this study, six recombinant nucleocapsid and spike proteins of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) were prepared and evaluated, including three prokaryotic expression nucleocapsid proteins (rN, rN1, rN2) and three eukaryotic expression spike proteins (rS1, rS-RBD, rS-RBD-mFc). The recombinant proteins with the highest ELISA titers (rS1 and rS-RBD-mFc) were selected to develop a double-antigen sandwich colloidal gold immunochromatography assay (GICA) to detect total antibodies against SARS-CoV-2. The clinical evaluation results showed that the sensitivity and specificity of GICA were 92.09% (419/455) and 99.44% (706/710), respectively. Moreover, a significant number (65.63%, 21/32) of COVID-19 patients with undetectable viral RNA were correctly diagnosed by the GICA method. In conclusion, the eukaryotic expression spike proteins (rS1 and rS-RBD-mFc) are more suitable than the prokaryotic expression nucleocapsid proteins for serological diagnosis of SARS-CoV-2. The proposed GICA for detection of total antibodies could be a powerful complement to the current RNA tests for COVID-19.

A Novel Mucosal Adjuvant System for Immunization against Avian Coronavirus Causing Infectious Bronchitis

Infectious bronchitis (IB) caused by infectious bronchitis virus (IBV) is currently a major threat to chicken health, with multiple outbreaks being reported in the United States over the past decade. Modified live virus (MLV) vaccines used in the field can persist and provide the genetic material needed for recombination and emergence of novel IBV serotypes. Inactivated and subunit vaccines overcome some of the limitations of MLV with no risk of virulence reversion and emergence of new virulent serotypes. However, these vaccines are weakly immunogenic and poorly protective. There is an urgent need to develop more effective vaccines that can elicit a robust, long-lasting immune response. In this study, we evaluate a novel adjuvant system developed from Quil-A and chitosan (QAC) for the intranasal delivery of nucleic acid immunogens to improve protective efficacy. The QAC adjuvant system forms nanocarriers (<100 nm) that efficiently encapsulate nucleic acid cargo, exhibit sustained release of payload, and can stably transfect cells. Encapsulation of plasmid DNA vaccine expressing IBV nucleocapsid (N) protein by the QAC adjuvant system (pQAC-N) enhanced immunogenicity, as evidenced by robust induction of adaptive humoral and cellular immune responses postvaccination and postchallenge. Birds immunized with pQAC-N showed reduced clinical severity and viral shedding postchallenge on par with protection observed with current commercial vaccines without the associated safety concerns. Presented results indicate that the QAC adjuvant system can offer a safer alternative to the use of live vaccines against avian and other emerging coronaviruses.IMPORTANCE According to 2017 U.S. agriculture statistics, the combined value of production and sales from broilers, eggs, turkeys, and chicks was $42.8 billion. Of this number, broiler sales comprised 67% of the industry value, with the production of >50 billion pounds of chicken meat. The economic success of the poultry industry in the United States hinges on the extensive use of vaccines to control infectious bronchitis virus (IBV) and other poultry pathogens. The majority of vaccines currently licensed for poultry health include both modified live vaccine and inactivated pathogens. Despite their proven efficacy, modified live vaccine constructs take time to produce and could revert to virulence, which limits their safety. The significance of our research stems from the development of a safer and potent alternative mucosal vaccine to replace live vaccines against IBV and other emerging coronaviruses.

Nanomedicine as a promising approach for diagnosis, treatment and prophylaxis against COVID-19

The COVID-19 pandemic caused by the newly emerged severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) puts the world in an unprecedented crisis, leaving behind huge human losses and deep socioeconomic damages. Due to the lack of specific treatment against SARS-CoV-2, effective vaccines and antiviral agents are urgently needed to properly restrain the COVID-19 pandemic. Repositioned drugs such as remdesivir have revealed a promising clinical efficacy against COVID-19. Interestingly, nanomedicine as a promising therapeutic approach could effectively help win the battle between coronaviruses (CoVs) and host cells. This review discusses the potential therapeutic approaches, in addition to the contribution of nanomedicine against CoVs in the fields of vaccination, diagnosis and therapy.

Techniques for the Measurement of Cell Mediated Immune Responses to Avian Influenza Virus

Cellular immune responses, through both T and B cells, are critical to understanding the role and regulation of lymphocytes following viral infection, as well as defining responses to vaccination. T cells play a critical role in adaptive immunity, including pathogen elimination through the engagement of CD4 and CD8 receptors, which trigger signaling mechanisms. B cells contribute to generating antibodies following exposure to foreign pathogens through interactions with CD4+ lymphocytes. While these different cell types have distinctly different modes of action in terms of contributions to protection (cytotoxic versus antibody mediated), they account for the majority of adaptive immunity induced following infection or vaccination. While the ability to measure cell-mediated immunity (CMI) has steadily improved, there is much to learn with regard to their contribution to the protection of birds against diseases induced by avian influenza virus. The rapidly increasing knowledge of genomic avian sequences, along with the increasing availability of monoclonal antibodies detecting avian cell-associated antigen markers, has made techniques to measure CMI more specific and informative for researchers.

Genetic and Pathologic Characterization of a Novel Recombinant TC07-2-Type Avian Infectious Bronchitis Virus

Avian infectious bronchitis viruses (IBVs) with the TC07-2 genotype have spread rapidly in East Asia since they were first reported in China in 2007. In 2015, an IBV with the TC07-2 genotype (designated KrD1515) was isolated from layer chickens with severe respiratory symptoms in Korea. In the present study, the full-length open reading frames of the spike (S) and nucleocapsid (N) genes of the virus were sequenced and analyzed. S1 gene phylogenetic analysis revealed that the KrD1515 virus clustered with viruses with the TC07-2 genotype, whereas N gene phylogenetic analysis revealed that the KrD1515 virus clustered with Korean IBVs, but not with Chinese TC07-2 IBV. When 7-day-old specific-pathogen-free chickens were inoculated with the KrD1515 virus, they developed severe respiratory symptoms and tracheal lesions. However, there were no other clinical symptoms or pathologic lesions in other tissues. The virus was shed from the trachea for at least a week and from the cloaca for only a day. Our findings suggest that the KrD1515 virus is a recombinant virus between a Chinese TC07-2 IBV and a non-TC07-2 Korean IBV and engages in respiratory tropism in chickens.

Protection against Virulent Infectious Bronchitis Virus Challenge Conferred by a Recombinant Baculovirus Co-Expressing S1 and N Proteins

Avian infectious bronchitis virus (IBV) is the causative agent of infectious bronchitis, which results in considerable economic losses. It is imperative to develop safe and efficient candidate vaccines to control IBV infection. In the current study, recombinant baculoviruses co-expressing the S1 and N proteins and mono-expressing S1 or N proteins of the GX-YL5 strain of IBV were constructed and prepared into subunit vaccines rHBM-S1-N, rHBM-S1 and rHBM-N. The levels of immune protection of these subunit vaccines were evaluated by inoculating specific pathogen-free (SPF) chickens at 14 days of age, giving them a booster with the same dose 14 days later and challenging them with a virulent GX-YL5 strain of IBV 14 days post-booster (dpb). The commercial vaccine strain H120 was used as a control. The IBV-specific antibody levels, as well as the percentages of CD4+ and CD8+ T lymphocytes, were detected within 28 days post-vaccination (dpv). The morbidity, mortality and re-isolation of the virus from the tracheas and kidneys of challenged birds were evaluated at five days post-challenge (dpc). The results showed that the IBV-specific antibody levels and the percentages of CD4+ and CD8+ T lymphocytes were higher in the rHBM-S1-N vaccinated birds compared to birds vaccinated with the rHBM-S1 and rHBM-N vaccines. At 5 dpc, the mortality, morbidity and virus re-isolation rate of the birds vaccinated with the rHBM-S1-N vaccine were slightly higher than those vaccinated with the H120 control vaccine but were lower than those vaccinated with the rHBM-S1 and rHBM-N vaccines. The present study demonstrated that the protection of the recombinant baculovirus co-expressing S1 and N proteins was better than that of recombinant baculoviruses mono-expressing the S1 or N protein. Thus, the recombinant baculovirus co-expressing S1 and N proteins could serve as a potential IBV vaccine and this demonstrates that the bivalent subunit vaccine including the S1 and N proteins might be a strategy for the development of an IBV subunit vaccine.

Infectious Bronchitis Virus Variants: Molecular Analysis and Pathogenicity Investigation

Infectious bronchitis virus (IBV) variants constantly emerge and pose economic threats to poultry farms worldwide. Numerous studies on the molecular and pathogenic characterization of IBV variants have been performed between 2007 and 2017, which we have reviewed herein. We noted that viral genetic mutations and recombination events commonly gave rise to distinct IBV genotypes, serotypes and pathotypes. In addition to characterizing the S1 genes, full viral genomic sequencing, comprehensive antigenicity, and pathogenicity studies on emerging variants have advanced our understanding of IBV infections, which is valuable for developing countermeasures against IBV field outbreaks. This review of IBV variants provides practical value for understanding their phylogenetic relationships and epidemiology from both regional and worldwide viewpoints.

Full genome analysis of Australian infectious bronchitis viruses suggests frequent recombination events between vaccine strains and multiple phylogenetically distant avian coronaviruses of unknown origin

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Vaccines contributed to emergence of recombinant IBV strains.

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Exotic avian coronaviruses have played a decisive role in recombination events.

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Recombination breakpoints have been in genes for nsp 2, 3 and 16 and the S protein.

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Avian coronavirus of unknown origin have been recombining with IBV for 20 years.

Australian strains of infectious bronchitis virus (IBV) have been evolving independently for many years, with control achieved by vaccination with local attenuated strains. Previous studies have documented the emergence of recombinants over the last 20 years, with the most recent one, Ck/Aus/N1/08, detected in 2008. These recombinants did not appear to be controlled by the vaccines currently in use.

In this study we sequenced the complete genomes of three emergent Australian strains of IBV (IBV/Ck/Aus/N1/88, IBV/Ck/Aus/N1/03 and IBV/Ck/Aus/N1/08) and a previously incompletely characterised vaccine strain, IBV/Ck/Aus/Armidale, and compared them to the genome of the vaccine strain VicS. We detected multiple recombination events throughout the genome between wild type viruses and the vaccine strains in all three emergent isolates. Moreover, we found that strain N1/88 was not entirely exogenous, as was previously hypothesised. Rather, it originated from a recombination event involving the VicS vaccine strain. The S glycoprotein genes of N1/88 and N1/03 were known to be genetically distinct from previously characterised circulating strains and from each other, and the original donors of these genes remains unknown. The S1 glycoprotein gene of N1/88, a subgroup 2 strain, shares a high nucleotide identity with the sequence of the S1 gene of the recent isolate N1/08. As the subgroup 2 strains have not been isolated for at least 20 years, it appears likely that an unknown avian coronavirus that was the donor of the S1 glycoprotein sequence of N1/88 in the 1980s is still recombining with IBV strains in the field.

Recombinant duck enteritis viruses expressing major structural proteins of the infectious bronchitis virus provide protection against infectious bronchitis in chickens

To design an alternative vaccine for control of infectious bronchitis in chickens, three recombinant duck enteritis viruses (rDEVs) expressing the N, S, or S1 protein of infectious bronchitis virus (IBV) were constructed using conventional homologous recombination methods, and were designated as rDEV-N, rDEV-S, and rDEV-S1, respectively. Chickens were divided into five vaccinated groups, which were each immunized with one of the rDEVs, covalent vaccination with rDEV-N & rDEV-S, or covalent vaccination with rDEV-N & rDEV-S1, and a control group. An antibody response against IBV was detectable and the ratio of CD4⁺/CD8⁺ T-lymphocytes decreased at 7 days post-vaccination in each vaccinated group, suggesting that humoral and cellular responses were elicited in each group as early as 7 days post-immunization. After challenge with a homologous virulent IBV strain at 21 days post-immunization, vaccinated groups showed significant differences in the percentage of birds with clinical signs, as compared to the control group (p < 0.01), as the two covalent-vaccination groups and the rDEV-S group provided better protection than the rDEV-N- or rDEV-S1-vaccinated group. There was less viral shedding in the rDEV-N & rDEV-S- (2/10) and rDEV-N & rDEV-S1- (2/10) vaccinated groups than the other three vaccinated groups. Based on the clinical signs, viral shedding, and mortality rates, rDEV-N & rDEV-S1 covalent vaccination conferred better protection than use of any of the single rDEVs.

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Infectious bronchitis virus (IBV) causes a respiratory disease in domestic chickens worldwide.

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Duck enteritis virus (DEV) was used as viral vaccine vector in chickens.

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Recombinant DEV (rDEV) expressing IBV N, S, or S1 conferred protection against IBV.

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Covalent vaccination with rDEV-N & rDEV-S1 conferred higher level of protection against IBV.

Prediction and identification of novel IBV S1 protein derived CTL epitopes in chicken

Infectious bronchitis virus (IBV) is a major pathogen common in the poultry industry. Broad cytotoxic T lymphocyte (CTL) response against IBV is one of the crucial factors that help to control viral replication. Spike glycoproteins on the surface of the IBV virion harbor major T cell epitopes. In this study, based on the peptide-binding motifs of chicken MHC I molecules for the BF2*4, BF2*12, BF2*15, and BF2*19 haplotypes, potential CTL epitopes were predicted using S1 proteins from different IBV strains. Twenty-one peptides were predicted to be potential CTL epitopes; they were manually synthesized and the CTL responses to them tested in vitro. Spleen lymphocytes were collected from specific-pathogen free (SPF) chicken that had been immunized with the S1 protein expression plasmid, pV-S1, and were stimulated by the synthesized peptides. IFN-γ secretion and CD8(+) T cell proliferation in chickens were tested by ELISpot array and flow cytometry, respectively. Four epitopes (P8SRIQTATDP, P9SRNATGSQP, P18GAYAVVNV, and P19SRIQTATQP) were identified to stimulate CD8(+) T cell proliferation and IFN-γ secretion, indicating their efficacy as CTL epitopes in chicken. Poly-CTL-epitope DNA vaccine (pV-S1T) was constructed by inserting nucleotide sequences encoding the P8, P9, P18, and P19 CTL epitopes into the pVAX1 vector. Chickens were vaccinated with either pV-S1, pV-S1T, or pVAX1 and the protection efficacy was analyzed, revealing that ninety percent of chickens immunized with pV-S1T were protected after challenge with 10(6) ELD50 of IBV, demonstrating that these novel CTL epitopes were effective against IBV challenge. This study provides a new method to screen virus CTL epitopes in chicken and to develop poly-CTL-epitope DNA vaccines.

A Highly Immunogenic and Protective Middle East Respiratory Syndrome Coronavirus Vaccine Based on a Recombinant Measles Virus Vaccine Platform

In 2012, the first cases of infection with the Middle East respiratory syndrome coronavirus (MERS-CoV) were identified. Since then, more than 1,000 cases of MERS-CoV infection have been confirmed; infection is typically associated with considerable morbidity and, in approximately 30% of cases, mortality. Currently, there is no protective vaccine available. Replication-competent recombinant measles virus (MV) expressing foreign antigens constitutes a promising tool to induce protective immunity against corresponding pathogens. Therefore, we generated MVs expressing the spike glycoprotein of MERS-CoV in its full-length (MERS-S) or a truncated, soluble variant of MERS-S (MERS-solS). The genes encoding MERS-S and MERS-solS were cloned into the vaccine strain MVvac2 genome, and the respective viruses were rescued (MVvac2-CoV-S and MVvac2-CoV-solS). These recombinant MVs were amplified and characterized at passages 3 and 10. The replication of MVvac2-CoV-S in Vero cells turned out to be comparable to that of the control virus MVvac2-GFP (encoding green fluorescent protein), while titers of MVvac2-CoV-solS were impaired approximately 3-fold. The genomic stability and expression of the inserted antigens were confirmed via sequencing of viral cDNA and immunoblot analysis. In vivo, immunization of type I interferon receptor-deficient (IFNAR(-/-))-CD46Ge mice with 2 × 10(5) 50% tissue culture infective doses of MVvac2-CoV-S(H) or MVvac2-CoV-solS(H) in a prime-boost regimen induced robust levels of both MV- and MERS-CoV-neutralizing antibodies. Additionally, induction of specific T cells was demonstrated by T cell proliferation, antigen-specific T cell cytotoxicity, and gamma interferon secretion after stimulation of splenocytes with MERS-CoV-S presented by murine dendritic cells. MERS-CoV challenge experiments indicated the protective capacity of these immune responses in vaccinated mice.

IMPORTANCE

Although MERS-CoV has not yet acquired extensive distribution, being mainly confined to the Arabic and Korean peninsulas, it could adapt to spread more readily among humans and thereby become pandemic. Therefore, the development of a vaccine is mandatory. The integration of antigen-coding genes into recombinant MV resulting in coexpression of MV and foreign antigens can efficiently be achieved. Thus, in combination with the excellent safety profile of the MV vaccine, recombinant MV seems to constitute an ideal vaccine platform. The present study shows that a recombinant MV expressing MERS-S is genetically stable and induces strong humoral and cellular immunity against MERS-CoV in vaccinated mice. Subsequent challenge experiments indicated protection of vaccinated animals, illustrating the potential of MV as a vaccine platform with the potential to target emerging infections, such as MERS-CoV.

Immune Responses to Virulent and Vaccine Strains of Infectious Bronchitis Viruses in Chickens

Infectious bronchitis (IB) is an acute and highly contagious chicken viral disease, causing severe economic losses to poultry producers worldwide. In the last few decades, infectious bronchitis virus (IBV) has been extensively studied, but knowledge of immune responses to virulent or vaccine strains of IBVs remains limited. This review focuses on fundamental aspects of immune responses against IBV, including the role of pattern recognition receptors (PRRs) in identification of conserved viral structures and the role of different components of innate immunity (e.g., heterophils, macrophages, dendritic cells, acute phase protein, and cytokines). Studies on adaptive immune activation and the role of humoral and cellular immunity in IBV clearance are also reviewed. Multiple interlinking immune responses are essential for protection against virulent IBVs, including passive, innate, adaptive, and effector T cells active at mucosal surfaces. Although the development of approaches for chicken transcriptome and proteome analyses have greatly helped the understanding of the underlying genetic mechanisms for immunity, there are still major knowledge gaps, such as the role of mucosal and cellular responses to IBVs. In view of recent reports of emergent IBV variants in many countries, there is renewed interest in a more complete understanding of poultry immune responses to both virulent and vaccine strains of IBVs. This will be critical for developing new vaccine or vaccination strategies and other intervention programs.

Progress and challenges toward the development of vaccines against avian infectious bronchitis

Avian infectious bronchitis (IB) is a widely distributed poultry disease that has huge economic impact on poultry industry. The continuous emergence of new IBV genotypes and lack of cross protection among different IBV genotypes have been an important challenge. Although live attenuated IB vaccines remarkably induce potent immune response, the potential risk of reversion to virulence, neutralization by the maternal antibodies, and recombination and mutation events are important concern on their usage. On the other hand, inactivated vaccines induce a weaker immune response and may require multiple dosing and/or the use of adjuvants that probably have potential safety risks and increased economic burdens. Consequently, alternative IB vaccines are widely sought. Recent advances in recombinant DNA technology have resulted in experimental IB vaccines that show promise in antibody and T-cells responses, comparable to live attenuated vaccines. Recombinant DNA vaccines have also been enhanced to target multiple serotypes and their efficacy has been improved using delivery vectors, nanoadjuvants, and in ovo vaccination approaches. Although most recombinant IB DNA vaccines are yet to be licensed, it is expected that these types of vaccines may hold sway as future vaccines for inducing a cross protection against multiple IBV serotypes.

Phylodynamic analysis of avian infectious bronchitis virus in South America

Infectious bronchitis virus (IBV) is a coronavirus of chickens that causes great economic losses to the global poultry industry. The present study focuses on South American IBVs and their genetic relationships with global strains. We obtained full-length sequences of the S1 coding region and N gene of IBV field isolates from Uruguay and Argentina, and performed Phylodynamic analysis to characterize the strains and estimate the time of the most recent common ancestor. We identified two major South American genotypes, which were here denoted South America I (SAI) and Asia/South America II (A/SAII). The SAI genotype is an exclusive South American lineage that emerged in the 1960s. The A/SAII genotype may have emerged in Asia in approximately 1995 before being introduced into South America. Both SAI and A/SAII genotype strains clearly differ from the Massachusetts strains that are included in the vaccine formulations being used in most South American countries.

High-level protein expression following single and dual gene cloning of infectious bronchitis virus N and S genes using baculovirus systems

Baculovirus is an efficient system for the gene expression that can be used for gene transfer to both insect and different vertebrate hosts. The nucleocapsid gene (N) of the infectious bronchitis virus was cloned in a baculovirus expression system for insect cell expression. Dual expression vectors containing IBV N and spike (S) proteins of the avian infectious bronchitis virus were engineered under the control of human and murine cytomegalovirus immediate-early enhancer/promoter elements in combination with the baculoviral polyhedrin and p10 promoters for simultaneous expression in both vertebrate and insect cells. Transduction of the N gene in the insect Sf9 cells revealed a high level of protein expression. The expressed protein, used in ELISA, effectively detected chicken anti-IBV antibodies with high specificity. Transduction of mammalian and avian cells with BacMam viruses revealed that dual expression cassettes yielded high levels of protein from both transcription units.

Recombinant nucleocapsid protein based single serum dilution ELISA for the detection of antibodies to infectious bronchitis virus in poultry

Avian infectious bronchitis is ubiquitous and highly contagious disease of poultry, with profound effect on commercial poultry production. For effective control of infectious bronchitis virus (IBV), quick and specific diagnosis is of utmost importance. In this study, the virus was isolated from clinical samples from India and the full length nucleocapsid (N) gene was amplified, cloned and expressed in a prokaryotic system. The purified recombinant N protein based single serum dilution enzyme linked immunosorbent assay (ELISA) was developed for IBV to measure specific antibody in the sera of chickens. A total of 310 chicken sera samples were tested using the commercial IDEXX kit along with the assay developed. A linear correlation was obtained between predicted antibody titres at a single working dilution of 1:100 and the corresponding serum titres observed as determined by the standard serial dilution method. Regression analysis was used to construct a standard curve from which an equation was derived which confirmed their correlation. The developed equation was then used to extrapolate predicated ELISA antibody titer from corrected absorbance readings of the single working dilution. The assay proved to be specific (95.8%) and sensitive (96.8%) when compared to the commercial IDEXX ELISA test.

Detection of cell-mediated immune response to avian influenza viruses

The measurement of cell-mediated immunity (CMI) is critical to understanding the role and regulation of avian lymphocytes following avian influenza virus (AIV) infection. While these different cell types have distinctly different modes of action in terms of contributions to protection, they account for the majority of adaptive immunity induced following infection or vaccination. Although the ability to measure CMI has steadily improved over the last few years, few studies have examined its role in protection of birds against AIV. The increasing availability of monoclonal antibodies recognizing various avian cell-associated antigens has made this technique more specific and informative.

A DNA vaccine expressing ENV and GAG offers partial protection against reticuloendotheliosis virus in the prairie chicken (Tympanicus cupido)

Recurring infection of reticuloendotheliosis virus (REV), an avian oncogenic gammaretrovirus, has been a major obstacle in attempts to breed and release the endangered Attwater's prairie chicken (Tympanicus cupido attwateri). The aim of this study was to develop a DNA vaccine that protects the birds against REV infection. A plasmid was constructed expressing fusion proteins of REV envelope (env) and VP22 of Gallid herpesvirus 2 or REV gag and VP22. Birds vaccinated with these recombinant plasmids developed neutralizing antibodies; showed delayed replication of virus; and had significantly less infection of lymphocytes, specifically CD4+ lymphocytes. Although the vaccine did not prevent infection, it offered partial protection. Birds in field conditions and breeding facilities could potentially benefit from increased immunity when vaccinated.

Avian metapneumoviruses expressing Infectious Bronchitis virus genes are stable and induce protection

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Foreign viral genes can be inserted into the AMPV genome.

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Resultant recombinant viruses express the inserted genes and are stable in cell culture.

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Both S1 and N genes from IBX QX induced protection against QX challenge.

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Induced seroconversion after recombinant inoculation was minimal.

The study investigates the ability of subtype A Avian metapneumovirus (AMPV) to accept foreign genes and be used as a vector for delivery of Infectious bronchitis virus (IBV) QX genes to chickens. Initially the GFP gene was added to AMPV at all gene junctions in conjunction with the development of cassetted full length DNA AMPV copies. After recombinant virus had been recovered by reverse genetics, GFP positions supporting gene expression while maintaining virus viability in vitro, were determined. Subsequently, either S1 or nucleocapsid (N) genes of IBV were positioned between AMPV M and F genes, while later a bivalent recombinant was prepared by inserting S1 and N at AMPV MF and GL junctions respectively. Immunofluorescent antibody staining showed that all recombinants expressed the inserted IBV genes in vitro and furthermore, all recombinant viruses were found to be highly stable during serial passage. Eyedrop inoculation of chickens with some AMPV-IBV recombinants at one-day-old induced protection against virulent IBV QX challenge 3 weeks later, as assessed by greater motility of tracheal cilia from chickens receiving the recombinants. Nonetheless evidence of AMPV/IBV seroconversion, or major recombinant tracheal replication, were largely absent.

Association of the chicken MHC B haplotypes with resistance to avian coronavirus

Clinical respiratory illness was compared in five homozygous chicken lines, originating from homozygous B2, B8, B12 and B19, and heterozygous B2/B12 birds after infection with either of two strains of the infectious bronchitis virus (IBV). All chickens used in these studies originated from White Leghorn and Ancona linages. IBV Gray strain infection of MHC homozygous B12 and B19 haplotype chicks resulted in severe respiratory disease compared to chicks with B2/B2 and B5/B5 haplotypes. Demonstrating a dominant B2 phenotype, B2/B12 birds were also more resistant to IBV. Respiratory clinical illness in B8/B8 chicks was severe early after infection, while illness resolved similar to the B5 and B2 homozygous birds. Following M41 strain infection, birds with B2/B2 and B8/B8 haplotypes were again more resistant to clinical illness than B19/B19 birds. Real time RT-PCR indicated that infection was cleared more efficiently in trachea, lungs and kidneys of B2/B2 and B8/B8 birds compared with B19/B19 birds. Furthermore, M41 infected B2/B2 and B8/B8 chicks performed better in terms of body weight gain than B19/B19 chicks. These studies suggest that genetics of B defined haplotypes might be exploited to produce chicks resistant to respiratory pathogens or with more effective immune responses.

Fine level epitope mapping and conservation analysis of two novel linear B-cell epitopes of the avian infectious bronchitis coronavirus nucleocapsid protein

The nucleocapsid (N) protein of the infectious bronchitis virus (IBV) may play an essential role in the replication and translation of viral RNA. The N protein can also induce high titers of cross-reactive antibodies and cell-mediated immunity, which protects chickens from acute infection. In this study, we generated two monoclonal antibodies (mAbs), designated as 6D10 and 4F10, which were directed against the N protein of IBV using the whole viral particles as immunogens. Both of the mAbs do not cross react with Newcastle disease virus (NDV), infectious laryngotracheitis virus (ILTV) and subtype H9 avian influenza virus (AIV). After screening a phage display peptide library and peptide scanning, we identified two linear B-cell epitopes that were recognized by the mAbs 6D10 and 4F10, which corresponded to the amino acid sequences (242)FGPRTK(247) and (195)DLIARAAKI(203), respectively, in the IBV N protein. Alignments of amino acid sequences from a large number of IBV isolates indicated that the two epitopes, especially (242)FGPRTK(247), were well conserved among IBV strains. This conclusion was further confirmed by the relationships of 18 heterologous sequences to the 2 mAbs. The novel mAbs and the epitopes identified will be useful for developing diagnostic assays for IBV infections.

Understanding the T cell immune response in SARS coronavirus infection

The severe acute respiratory syndrome (SARS) epidemic started in late 2002 and swiftly spread across 5 continents with a mortality rate of around 10%. Although the epidemic was eventually controlled through the implementation of strict quarantine measures, there continues a need to investigate the SARS coronavirus (SARS-CoV) and develop interventions should it re-emerge. Numerous studies have shown that neutralizing antibodies against the virus can be found in patients infected with SARS-CoV within days upon the onset of illness and lasting up to several months. In contrast, there is little data on the kinetics of T cell responses during SARS-CoV infection and little is known about their role in the recovery process. However, recent studies in mice suggest the importance of T cells in viral clearance during SARS-CoV infection. Moreover, a growing number of studies have investigated the memory T cell responses in recovered SARS patients. This review covers the available literature on the emerging importance of T cell responses in SARS-CoV infection, particularly on the mapping of cytotoxic T lymphocyte (CTL) epitopes, longevity, polyfunctionality and human leukocyte antigen (HLA) association as well as their potential implications on treatment and vaccine development.

Immune responses to mucosal vaccination by the recombinant A1 and N proteins of infectious bronchitis virus

Infectious bronchitis virus (IBV) is prevented primarily by the use of live attenuated vaccines, which are known to have a limited strain range of protection. Alternative vaccines against the emerging new virus strains can improve control of the disease. The aim of this study was to evaluate the immunogenic potential of two recombinant viral proteins, when administered by eyedrop, without the assistance of a vector. The recombinant S1 (rS1) and N (rN) proteins of the M41 strain expressed in E. coli were tested, and the live attenuated vaccine H120 was used as a positive control. Protection was evaluated by re-isolation of virus from tracheas of vaccinated chickens after challenge with strain M41. After three immunizations, rS1 glycoprotein induced 40% protection, while vaccination with rN provided no protection. Vaccination with rS1, rN, or H120 induced a cellular immune response as demonstrated by in vitro ChIFN-γ production by splenocytes of vaccinated birds. Vaccination with H120, and to a lesser extent rS1, induced HI and virus-specific IgG antibody production. These findings indicate that recombinant viral proteins administered through the mucosal route can evoke an immune response without the assistance of a vector.

Oral and nasal DNA vaccines delivered by attenuated Salmonella enterica serovar Typhimurium induce a protective immune response against infectious bronchitis in chickens

Several studies have reported that intramuscular injection of DNA vaccines against infectious bronchitis virus (IBV) induces protective immune responses. In the present study, we developed oral and nasal DNA vaccines that carried the S1 gene and N gene of IBV delivered by attenuated Salmonella enterica serovar Typhimurium strains SL/pV-S1 and SL/pV-N, respectively. The safety and stability of recombinant Salmonella vaccine were evaluated. Following oral and nasal administration to chickens, the serum and mucosal samples were collected and antibodies against IBV were measured. Chickens were then challenged with IBV strain M41 by the nasal-ocular route 3 weeks after boosting. The results showed that oral and nasal immunization with coadministered SL/pV-S1 and SL/pV-N elicited significant IBV-specific humoral and mucosal immune responses and conferred protective efficacy against IBV challenge higher than that in chickens immunized only with SL/pV-S1. The current study shows that novel DNA vaccines delivered by attenuated S. Typhimurium may be promising candidates for the prevention of infectious bronchitis (IB).These vaccines are efficacious, easily produced economically, and able to be delivered orally and nasally rather than injected. Coadministration of SL/pV-S1 and SL/pV-N may represent an effective mucosal vaccination regimen.

Protective immune responses induced by in ovo immunization with recombinant adenoviruses expressing spike (S1) glycoprotein of infectious bronchitis virus fused/co-administered with granulocyte-macrophage colony stimulating factor

Infectious bronchitis virus (IBV) causes tremendous economic losses associated with production inefficiencies and mortality in poultry industry worldwide. In the present report, the recombinant adenoviruses expressing chicken granulocyte-macrophage colony stimulating factor (GM-CSF) and S1 gene of nephropathogenic IBV were constructed and characterized. Then, the immunological efficacy and protection against homologous IBV challenge were assessed in specific pathogen free (SPF) chickens. The results showed that the chickens vaccinated in ovo with rAd-S1, rAd-GM-S1 (GM-CSF fused with S1 using glycine linkers) and rAd-GM-CSF plus rAd-S1 (co-administered) developed specific anti-IBV HI antibodies. Moreover, the fusion of the GM-CSF markedly increased spleen cell proliferation and IFN-γ production while mild increased in IL-4 production, which demonstrated the enhancement of cell-mediated immune responses. Following challenge with IBV, the chickens in the group vaccinated with rAd-S1 fused or co-administered with GM-CSF had fewer nephropathic lesions and showed 100% protection as compared to that of rAd-S1 alone which showed 70% protection. It indicated that the single dose in ovo vaccination of the GM-CSF fused or co-administered with S1 of IBV could enhance significantly the humoral, cellular immune responses and provide complete protection against nephropathogenic IBV challenge. This finding may provide basic information for effective in ovo vaccines design against IBV.

CD8+ T cell response in HLA-A*0201 transgenic mice is elicited by epitopes from SARS-CoV S protein

Cytotoxic CD8(+) T lymphocytes (CTLs) play an important role in antiviral immunity. Several human HLA-A*0201 restricted CTL epitopes of severe acute respiratory syndrome (SARS) spike (S) protein have been identified in HLA-A*0201 transgenic (Tg) mice, but the mechanisms and properties of immune responses are still not well understood. In this study, HLA-A*0201 Tg mice were primed intramuscularly with SARS S DNA and boosted subcutaneously with HLA-A*0201 restricted peptides. The lymphocytes from draining lymph nodes, spleens and lungs were stimulated with the cognate peptides. Three different methods (ELISA, ELISPOT and FACS) were used to evaluate the immune responses during short and long periods of time after immunization. Results showed that peptide-specific CD8(+) T cells secreted IFN-γ, TNF-α and IL-2 and expressed CD107a/b on cell surface. IFN-γ(+)CD8(+) T cells and CD107a/b(+)CD8(+) T cells distributed throughout the lymphoid and non-lymphoid tissues, but the frequency of peptide-specific CD8(+) T cells was higher in lungs than in spleens and lymph nodes. The phenotype of the CD8(+) T cells was characterized based on the expression of IFN-γ. Most of the HLA-A*0201 restricted peptide-specific CD8(+) T cells represented a memory subset with CD45RB(high) and CD62L(low). Taken together, these data demonstrate that immunization with SARS S DNA and HLA-A*0201 restricted peptides can elicit antigen-specific CD8(+) T cell immune responses which may have a significant implication in the long-term protection. We provide novel information in cellular immune responses of SARS S antigen-specific CD8(+) T cells, which are important in the development of vaccine against SARS-CoV infection.

Priming with a DNA vaccine and boosting with an inactivated vaccine enhance the immune response against infectious bronchitis virus

The methods of repeated immunization with inactivated vaccines have been used widely to increase antibody protection against infectious bronchitis virus (IBV). However, compared with DNA vaccines, these methods usually induce poor cellular responses. In the present study, specific pathogen-free (SPF) chickens were immunized intramuscularly with a DNA vaccine carrying the main IBV structural genes (pVAX1-S1, pVAX1-M, and pVAX1-N, respectively) and boosted with the IBV M41 strain inactivated vaccine to assess whether such a new strategy could enhance the immune responses against IBV. The protection efficacy of the DNA vaccine carrying different structural genes for priming was evaluated further. The chickens were immunized primely on day 7 and boosted 2 weeks later. After that, distribution of the DNA vaccine in vivo, the percentage of CD4+CD3+ and CD8+CD3+ subgroups of peripheral blood T-lymphocytes, and the specific IgG and virus neutralizing antibodies were measured. Chickens were then challenged by the nasal-ocular route with the IBV M41 strain 4 weeks after booster immunization. The results demonstrated that priming with a DNA vaccine encoding nucleocapsid protein (pVAX1-N) and boosting with the inactivated IBV vaccine led to the dramatic augmentation of humoral and cellular responses, and provided up to 86.7% rate of immune protection, providing an effective approach to protect chickens from IBV.

CLONAGEM, EXPRESSÃO E CARACTERIZAÇÃO DA NUCLEOPROTEÍNA RECOMBINANTE DO VÍRUS DA BRONQUITE INFECCIOSA EM ESCHERICHIA COLI E EM PICHIA PASTORIS

RESUMO O gene da proteína de nucleocapsídeo (1.230 pb) da estirpe M41 do vírus da bronquite infecciosa (VBI) foi amplificado pelas reações de transcrição reversa e em cadeia da polimerase (RT-PCR) e clonado, em seguida, em dois sistemas; pET28a - Escherichia coli e pFLD -Pichia pastoris. Os produtos recombinantes construídos para expressão (pET28a-N ou pFLD-N) foram identificados por análises de PCR e de sequenciamento de nucleotídeos. Os clones transformantes da linhagem BL21 de E. coli e da linhagem GS115 de P. pastoris foram submetidos aos protocolos apropriados de indução. A expressão da proteína N de fusão com etiqueta de poli-histidina e com massa molecular de 54 kDa foi determinada pelas técnicas de SDS-PAGE e de Western blotting, confirmando-se que ambas proteínas N recombinantes apresentaram tamanhos e antigenicidade compatíveis com a proteína N nativa do próprio VBI. O sistema E. coli expressou uma quantidade relevante da proteína N recombinante, enquanto que o sistema P. pastoris produziu uma baixa recuperação dessa proteína recombinante. A proteína N recombinante gerada pelo sistema bacteriano foi purificada em resina de níquel-sepharose. O conjunto de resultados indica que o sistema de expressão constituído por pET28a – E. coli é mais efetivo para produzir a proteína N recombinante do VBI destinada ao uso como antígeno para detectar anticorpos anti-virais específicos em ensaios de imunodiagnóstico para essa infecção viral.

Avian influenza viral nucleocapsid and hemagglutinin proteins induce chicken CD8+ memory T lymphocytes

The avian influenza viruses (AIVs) can be highly contagious to poultry and a zoonotic threat to humans. Since the memory CD8(+) T lymphocyte responses in chickens to AIV proteins have not been defined, these responses to H5N9 AIV hemagglutinin (HA) and nucleocapsid (NP) proteins were evaluated by ex vivo stimulation with virus infected non-professional antigen presenting cells. Secretion of IFNgamma by activated T lymphocytes was evaluated through macrophage induction of nitric oxide. AIV specific, MHC-I restricted memory CD8(+) T lymphocyte responses to NP and HA were observed 3 to 9 weeks post-inoculation (p.i.). The responses specific to NP were greater than those to HA with maximum responses being observed at 5 weeks p.i. followed by a decline to weakly detectable levels by 9 weeks p.i. The cross-reaction of T lymphocytes to a heterologous H7N2 AIV strain demonstrated their ability to respond to a broader range of AIV.

SARS vaccines: where are we?

In this review, the current state of vaccine development against human severe acute respiratory syndrome (SARS) coronavirus, focusing on recently published data is assessed. We discuss which strategies have been assessed immunologically and which have been evaluated in SARS coronavirus challenge models. We discuss inactivated vaccines, virally and bacterially vectored vaccines, recombinant protein and DNA vaccines, as well as the use of attenuated vaccines. Data regarding the correlates of protection, animal models and the available evidence regarding potential vaccine enhancement of SARS disease are discussed. While there is much evidence that various vaccine strategies against SARS are safe and immunogenic, vaccinated animals still display significant disease upon challenge. Current data suggest that intranasal vaccination may be crucial and that new or combination strategies may be required for good protective efficacy against SARS in humans.

The protective immune response against infectious bronchitis virus induced by multi-epitope based peptide vaccines

Peptide vaccine was found to be an effective and powerful approach to a variety of pathogens. To explore multi-epitope based peptide vaccines against infectious bronchitis virus (IBV), the immunogenic peptides were fused to the 3' terminal of glutathione S transferase gene (GST) and expressed in Escherichia coli. ELISA and Western blot analysis showed that the purified fusion proteins had excellent immune activity with chicken anti-IBV serum. During the vaccination course, the candidate peptide vaccines induced strong humoral and cellular response, and provided up to 80.0% immune protection, while all non-immunized chickens in the negative control group manifested obvious typical symptoms and died after virus challenge. Our finding provides a new way to develop multi-epitope based peptide vaccine against IBV.

A prime-boost vaccination protocol optimizes immune responses against the nucleocapsid protein of the SARS coronavirus

Severe acute respiratory syndrome (SARS) is a serious infectious disease caused by the SARS coronavirus. We assessed the potential of prime-boost vaccination protocols based on the nucleocapsid (NC) protein co-administered with a derivative of the mucosal adjuvant MALP-2 or expressed by modified Vaccinia virus Ankara (MVA–NC) to stimulate humoral and cellular immune responses at systemic and mucosal levels. The obtained results demonstrated that strong immune responses can be elicited both at systemic and mucosal levels following a heterologous prime-boost vaccination protocol consisting in priming with NC protein add-mixed with MALP-2 by intranasal route and boosting with MVA–NC by intramuscular route.

Molecular characterization of a new PToV strain. Evolutionary implications

Toroviruses are emergent viruses, belonging to the Nidovirales order, that remain mostly ignored, despite they are able to infect different species of domestic animals and humans, causing enteric diseases and diarrhea. Thus far, only five variants of porcine torovirus (PToV) have been identified. In this report we describe the identification and partial characterization of a new strain of porcine torovirus (PToV-BRES) that was detected by RT-PCR in a swine faecal specimen from a farm in Brescia (Italy). The complete genes coding for the nucleocapsid (N), hemagglutinin-esterase (HE) and membrane (M) proteins were amplified, and sequence analysis showed that PToV-BRES is a new PToV strain that, based on the HE gene sequence, is phylogenetically related to P4 strain, that was up to now the only member of a distinct PToV lineage. The nucleocapsid protein from PToV-BRES was expressed in insect cells as a his-tagged protein, purified by affinity chromatography and used to develop an ELISA method to detect antibodies against PToV. This assay was evaluated using a serum collection including 45 samples from three commercial farms from Spain. High antibody prevalence against PToV was observed in the three farms, both in adult animals and in piglets, which could suggest that PToV might be endemic in Spanish porcine population. The ELISA method developed in this work could be useful in future epidemiological surveys about toroviruses.

An avian, oncogenic retrovirus replicates in vivo in more than 50% of CD4+ and CD8+ T lymphocytes from an endangered grouse

Reoccurring infection of reticuloendotheliosis virus (REV), an avian oncogenic retrovirus, has been a major obstacle in attempts to breed and release an endangered grouse, the Attwater's prairie chicken (Tympanicus cupido attwateri). REV infection of these birds in breeding facilities was found to result in significant decreases in the CD4(+) and increases in the CD8(+) lymphocyte populations, although experimental infection of birds resulted in only increases in the CD8(+) lymphocytes. Because our indirect immunofluorescent assay readily detected infection of both CD4(+) and CD8(+) lymphocytes, a triple labeling flow cytometric procedure was developed to quantify the individual lymphocytes infected in vivo with REV. Lymphocytes were gated with a biotinylated pan-leukocyte marker bound to streptavidin R-PE-Cy5. Chicken CD4 or CD8 specific mouse MAb directly labeled with R-PE identified the phenotype and with permeabilizing of cells, infection was indirectly labeled with rabbit IgG specific for the REV gag polypeptide and FITC conjugated goat anti-rabbit antibody. More than 50% of the total lymphocytes and of the total CD4(+) or CD8(+) lymphocytes supported in vivo viral expression in all infected birds examined. Remarkably, this level of infection was detected in the absence of visible clinical signs of illness.