Infectious Bronchitis Virus Vaccine Strains Research Articles

Concurrent infection of Infectious Bronchitis Virus and Mycoplasma gallisepticum in a backyard poultry

This study reports the co-existence of two S1 mutants of GI-13 (4/91-like) Infectious Bronchitis Virus (IBV) and Mycoplasma gallisepticum (MG) in a backyard poultry flock that had non-vaccinated 30 broiler chickens and four turkey pullets. Serum samples and tracheal swabs were taken from the chickens and turkey pullets showing respiratory signs. Serum antibody levels were measured using commercial ELISA kits against IBV, Avian Influenza Virus (AIV), Newcastle Disease Virus (NDV), Avian Metapneumovirus (AMPV), MG, Mycoplasma synoviae (MS), and Ornithobacterium rhinotracheale (ORT). Additionally, tracheal swabs were tested for AIV serotypes H5, H7, and H9, NDV, IBV, AMPV, MG, MS, Pasteurella multocida, Avibacterium paragallinarum, and Bordetella avium by circular amplification technology (CAT). Anti-MS, -IBV, -MG, -NDV, -AMPV, and -ORT IgG antibodies were detected in some chicken sera, while anti-NDV, -MG, -MS, and -ORT IgG antibodies were detected in turkey sera. All avian tracheal swabs were positive for MG. However, IBV was only detected in chicken tracheal samples tested by CAT. The IBV strains were genotyped by sequencing a part of the S1 glycoprotein gene. The alignment analyses of two isolates showed 99.35% and 98.69% nucleotide similarities and 99.02% amino acid similarities with the 4/91 IBV vaccine and field strains. Two mutants showed 99.35% nucleotide and 100% amino acid sequence identity to each other. The turkeys and chickens in the flock had MG and MG/IBV co-infections, respectively. Consequently, the presence of mutants of 4/91 (GI-13) IBV genotypes and MG found in backyard poultry could be a potential epidemiological source for commercial flocks in poultry integrations.

Which strain of the avian coronavirus vaccine will become the prevalent one in China next?

Infectious bronchitis virus (IBV) is a vital pathogen in poultry farms, which can induce respiratory, nephropathogenic, oviduct, proventriculus, and intestinal diseases. Based on the phylogenetic classification of the full-length S1 gene, IBV isolates have been categorized into nine genotypes comprising 38 lineages. GI (GI-1, GI-2, GI-3, GI-4, GI-5, GI-6, GI-7, GI-13, GI-16, GI-18, GI-19, GI-22, GI-28, and GI-29), GVI-1 and GVII-1 have been reported in China in the past 60 years. In this review, a brief history of IBV in China is described, and the current epidemic strains and licensed IBV vaccine strains, as well as IBV prevention and control strategies, are highlighted. In addition, this article presents unique viewpoints and recommendations for a more effective management of IBV. The recombinant Newcastle Disease virus (NDV) vector vaccine expressed S gene of IBV QX-like and 4/91 strains may be the dominant vaccine strains against NDV and IBV.

Isolation and Characterization of Avian Coronavirus from Diagnostic Cases of Selected Bird Species in Malaysia

Infectious bronchitis virus (IBV) in chicken (Gallus gallus) is the most common and well-studied Avian coronavirus (ACoV) in avian species. The study aims to molecularly characterize ACoV isolate of selected bird species other than chicken obtained from the archived samples of field diagnostic cases in the Northern Zone Veterinary Laboratory (MVZU), Malaysia. Twelve archived virus isolates from 2013 to 2019 were amplified using selected primers on the 3’ UTR gene and S1 gene for oligonucleotide sequencing. These sequences were then molecularly characterized and compared with common IBV strains in chicken to determine the genetic diversity of the virus among selected avian species. Subsequent analyses of the nucleotides amplified on 3’ UTR conserved region of 12 selected ACoVs isolates originating from peacocks (Pavo cristatus), turkey (Meleagris), jungle fowl (Gallus gallus spadiceous), guinea fowl (Meleagris gallopavo domesticus), goose (Anser anser domesticus), love bird (Agapornis), macaw (Ara macao), and bird (species unidentified) are classified as belonging to the gammacoronavirus (Gamma-CoV) genus and have a high degree of homology. The S1 complete gene sequence analyses of guinea fowl and jungle fowl showed that both ACoV isolates are Gamma-CoV and under genotype I and GI-13 lineages. Both are identified as having a high similarity of 98% and 99%, respectively, with IBV vaccine strain 4/91 (AF093793). Due attention should be given to ACoVs strains, especially the IBV vaccine strains detected in other bird species, because there is a high probability that other bird species could be the source of pathogenic ACoV infection in general and IBV infection in chickens, as reported in other countries.

Evolution of avian infectious bronchitis vaccine viruses reisolated from vaccinated broilers

Genetic and phenotypic diversity among infectious bronchitis virus (IBVs) is a key element of the epidemiology of avian infectious bronchitis. Virtually, all studies have focused on the evolution of wild viruses. Live-attenuated vaccine strains deserve a special attention. Two strains of IBV, 2T/17 and 16T/17, detected by quantitative reverse transcription polymerase chain reaction (qRT-PCR) in samples from H120 vaccinated chickens showing respiratory signs, were genetically analysed targeting the S1 gene. The total RNA was extracted by the classical Trizol method. The whole S1 gene was amplified in an end-point RT-PCR using a specific primer pair, before being sequenced. The obtained sequences were compared to those of vaccine strains and reference viruses and finally subjected to a phylogenetic analysis. The two isolates turned out to be vaccine strains as evidenced by the monophyletic cluster they formed with the H120 vaccine strain (100% bootstrap). Also, they shared with this vaccine strain 99.60% and 99.47% of nucleotides (nt) for strain 2T/17 and 16T/17 respectively. The sequence alignment revealed, for each of the two strains, one non-synonymous nt substitution outside the hypervariable regions: C56T and T39G leading to two amino acid (aa) substitutions: Alv19Val and Cys13Trp, respectively for the strain 2T/17 and 16T/17. The second hypervariable region of strain 2T/17 displayed 2 nt substitutions at positions 345 and 347, resulting in an aa substitution Lys116Thr. As for 16T/17 strain, it harboured two non-synonymous nt substitutions (T353G and T380G), leading to two aa substitutions: Val118Gly and Met127Arg. The chromatogram analysis revealed minor and major peaks at all positions where nt changes were observed. Nucleotides associated with minor peaks matched with those observed in the sequence of the H120 vaccine strain at the same positions, indicating subpopulation selection. Only the substitution T353G results in a mutation as evidenced by the absence of minor peak at this position. Viral subpopulations contained in IBV live-attenuated vaccines are susceptible to be in vivo selected and emerge as persistent pathotype with reversion to virulence. This draws attention to the need of monitoring the evolution of IBV vaccine strains.

Infectious Bronchitis Virus Infection of Chicken: The Essential Role of Mucosal Immunity.

Infection with either virulent or vaccine strains of infectious bronchitis virus (IBV) elicits a complex interaction of nonspecific, innate, mucosal, cellular, and humoral immunity, thereby mounting an optimal defensive response in chickens. Through this process, mucosal immunity plays an essential role in preventing infection and clearing the virus. It also assists in the development of longer lasting local immunity against IBV, mainly in the respiratory tract but also in the oviduct and gastrointestinal mucosal linings. The head-associated lymphoid tissues, particularly the Harderian gland, have an important role in the synthesis of immunoglobulin A (IgA). Levels of this immunoglobulin in lachrymal fluid often reflect the degree of protection against IBV challenge. Beyond the head, the importance of mucosal immunity has predominantly been studied in the trachea. Though IgA has been the major focus of IBV mucosal immunity investigations, the role of mucosa-associated nonspecific, innate, and cellular immune responses may also be significant. Ciliary movements and nonspecific substances in the mucosa, such as mucins and peptides, assist in the entrapment and removal of living and nonliving antigens. Mucosa-associated innate immune responses determine cascades of downstream cellular and humoral immunity against IBV. Cellular immunity, particularly involving CD4+, CD8+, and other T-cell subsets, have been studied in mucosa-associated sites, especially the trachea. The strength of cellular immunity at mucosal sites has been associated with protection against IBV. Recently, the evaluation of mucosal immunity has shifted from traditional methods to quantitative assays of mRNA transcription of immune genes. This and other molecular-based approaches will likely boost our understanding of chicken mucosal immunity against virulent and vaccine strains of IBV. It has been well accepted that mucosal immunity plays an important role in pathogenicity, vaccinal immunity, and protection conferred against virulent IBV.

Research Note: Effects of Escherichia coli co-infection on the protective efficacy assessment of two common infectious bronchitis vaccines

Avian infectious bronchitis (IB), a highly contagious disease hazardous to the poultry industry, is caused by an etiological agent called the infectious bronchitis virus (IBV). Some IBV strains (IBVs) alone usually do not cause high mortality in field conditions if not with secondary pathogens including Escherichia coli (E. coli). Herein, we established an IBV and E. coli co-infection model to evaluate the protective efficacy of two IBV vaccine strains against a new emerging genotype GVI-1 with mild virulence in experimental conditions. Chickens were inoculated with IBV field isolate ZQX (genotype GVI-1) and challenged 4 dlater with the E. coli strain MS160427 (serotype O8). Subsequently, these chickens were euthanized at seven days postchallenge (d.p.c.) with E. coli. An autopsy revealed that lesions in the IBV plus E. coli co-infection group were more severe than those in the IBV-infected group. This pathological model was used to assess the protective effect of two commonly used vaccine strains (H120 and 4/91) against the IBV ZQX strain, and a significantly better protective efficacy was observed for 4/91 compared with H120. Thus, IBV and E. coli co-infection could be employed in assessing the protective efficacy of IBV vaccines.

Construction of an infectious bronchitis virus vaccine strain carrying chimeric S1 gene of a virulent isolate and its pathogenicity analysis.

Infectious bronchitis virus (IBV) is a member of genus gamma-coronavirus in the family Coronaviridae, causing serious economic losses to the poultry industry. Reverse genetics is a common technique to study the biological characteristics of viruses. So far, there is no BAC reverse genetic system available for rescue of IBV infectious clone. In the present study, a new strategy for the construction of IBV infectious cDNA clone was established. The full-length genomic cDNA of IBV vaccine strain H120 was constructed in pBAC vector from four IBV fragment subcloning vectors by homologous recombination, which contained the CMV promoter at the 5′ end and the hepatitis D virus ribozyme (HDVR) sequence and bovine growth hormone polyadenylation (BGH) sequence after the polyA tail at the 3′ end of the full-length cDNA. Subsequently, using the same technique, another plasmid pBAC-H120/SCS1 was also constructed, in which S1 gene from IBV H120 strain was replaced with that of a virulent SC021202 strain. Recombinant virus rH120 and rH120/SCS1 were rescued by transfecting the plasmids into BHK cells and passaged in embryonated chicken eggs. Finally, the pathogenicity of both the recombinant virus strains rH120 and rH120/SCS1 was evaluated in SPF chickens. The results showed that the chimeric rH120/SCS1 strain was not pathogenic compared with the wild-type IBV SC021202 strain and the chickens inoculated with rH120/SCS1 could resist challenge infection by IBV SC021202. Taken together, our results indicate that BAC reverse genetic system could be used to rescue IBV in vitro and IBV S1 protein alone might not be the key factor for IBV pathogenicity.Key points • BAC vector was used to construct IBV full-length cDNA by homologous recombination. • Based on four subcloning vectors, a recombinant chimeric IBV H120/SCS1 was constructed and rescued. • Pathogenicity of H120/SCS1 was similar to that of H120, but different to that of SC021202.

High-resolution melting curve analysis for infectious bronchitis virus strain differentiation.

Background and Aim:Belonging to the Coronaviridae family, avian infectious bronchitis virus (IBV) causes respiratory, reproductive, and renal diseases in poultry. Preventative measures lie mainly in vaccination, while the gold standard for IBV classification and differentiation is based on the sequence analysis of the spike 1 (S1) gene. In this study, we tested a new assay for IBV strain classification that is less expensive and requires reduced time and effort to perform. We carried out a quantitative real-time polymerase chain reaction followed by high-resolution melting (qRT-PCR/HRM) curve analysis.Materials and Methods:In this study, qRT-PCR was conducted on a partial fragment S1 gene followed by a high resolution melting curve analysis (qRT-PCR/HRM) on 23 IBV-positive samples in Jordan. For this assay, we utilized the most common IBV vaccine strains (Mass and 4/91) as a reference in the HRM assay. To evaluate the discrimination power of the qRT-PCR/HRM, we did the sequencing of the partial S1 gene.Results:It was shown that HRM was able to classify IBV samples into four clusters based on the degree of similarity between their melting points: The first cluster exhibited the highest similarity to the 4/91 strain, while the second was similar to the Mass-related IBV strain. Although the third cluster contained the highest number of samples, it displayed no similarity to any of the reference vaccine strains, and, after comparing them with the sequencing results, we found that the samples in the third cluster were similar to the variant II-like (IS-1494-06) IBV field strain. Finally, the fourth cluster comprised one unique sample that was found to belong to the Q1 IBV strain.Conclusion:Our developed qRT-PCR/HRM curve analysis was able to detect and rapidly identify novel and vaccine-related IBV strains as confirmed by S1 gene nucleotide sequences, making it a rapid and cost-effective tool.

Viral interference between H9N2-low pathogenic avian influenza virus and avian infectious bronchitis virus vaccine strain H120 in vivo

The interaction between a low pathogenic avian influenza virus (A/CK/TUN/145/2012), a H9N2 Tunisian isolate, and a vaccine strain (H120) of avian infectious bronchitis, administered simultaneously or sequentially three days apart to chicks during 20 days, was evaluated using ELISA antibody levels, quantitative reverse transcription–polymerase chain reaction (qRT-PCR) analyses and histopathology examination. First, the in vivo replication interference of avian influenza virus (AIV) and infectious bronchitis virus (IBV) was evaluated using qRT-PCR to detect accurately either AIV or IBV genomes or viral copy numbers during dual infections. Second, we have determined the amount of specific antibodies in sera of chick’s infected with AIV alone, IBV alone, mixed AIV + IBV, IBV then AIV or AIV IBV 3 days later using an ELISA test. Finally, histopathological analyses of internal organs from inoculated chicks were realized. Quantitative results of AIV and IBV co-infection showed that interferences between the two viruses yielded decreased viral growth. However, in the case of super-infection, the second virus, either AIV or IBV, induced a decrease in the growth of the first inoculated virus. According to our results, vaccine application was safe and do not interfere with AIV H9N2 infection, and does not enhance such infection. In conclusion, co-infection of chicks with AIV and IBV, simultaneously or sequentially, affected the clinical signs, the virus replication dynamics as well as the internal organ integrity. The results proposed that infection with heterologous virus may result in temporary competition for cell receptors or competent cells for replication, most likely interferon-mediated.

Genetic characterization of S1 gene of infectious bronchitis virus isolated from commercial poultry flocks in West Java, Indonesia.

Background and Aim:Infectious bronchitis (IB) is still a major problem among poultry industry in Indonesia, IB outbreaks continue to happen even in vaccinated flocks. The emergence of new IB virus (IBV) variants might lead to mismatching between vaccine virus strain and circulating virus strain, this may be a reason of vaccination failure. Information about circulating IBV in a region is important to decide which IB vaccine should be used. However, information about recent IBV strains which circulated in Indonesia and their genetic characters were limited; therefore, the aim of our research was to determine the genetic characterization of S1 gene of IBV isolated from commercial poultry flocks in West Java, Indonesia.Materials and Methods:A total of 47 viral isolate samples collected from chickens with clinical sign and reduced in egg production. Six IB live vaccines were used as control, the reference vaccines represent IBV strains including H120, H52, 4/91, CR88, 233A, and 1-96. Primers XCe2+ and XCe2- were used to amplify S1 gene partially.Results:Twenty-six of 47 samples showed positive result to S1 gene of IBV by reverse transcription-polymerase chain reaction. Three IBV isolates, Indonesia/K233A31/18, Indonesia/K4A9/17, and Indonesia/P3/17, were selected for nucleotide sequencing. Phylogenetic analysis of 352 nucleotides of the partial S1 gene shows that isolates Indonesia/K4A9/17 and Indonesia/K233A31/18 have 100% homology with IBV vaccine strain 4/91, while isolate Indonesia/P3/17 has 100% homology with IBV vaccine strain 233A.Conclusion:Our result indicates that at least two IBV strains were circulating among poultry in West Java, Indonesia, which is IBV close to vaccine strain 4/91 and 233A. The present study provides updates on the circulating IBV in commercial poultry flocks in West Java, Indonesia, and might use as guidance on selecting a proper IB vaccine strain to improve IB vaccination efficacy in certain region.

Recombinant infectious bronchitis viruses expressing heterologous S1 subunits: potential for a new generation of vaccines that replicate in Vero cells.

The spike glycoprotein (S) of infectious bronchitis virus (IBV) comprises two subunits, S1 and S2. We have previously demonstrated that the S2 subunit of the avirulent Beau-R strain is responsible for its extended cellular tropism for Vero cells. Two recombinant infectious bronchitis viruses (rIBVs) have been generated; the immunogenic S1 subunit is derived from the IBV vaccine strain, H120, or the virulent field strain, QX, within the genetic background of Beau-R. The rIBVs BeauR-H120(S1) and BeauR-QX(S1) are capable of replicating in primary chicken kidney cell cultures and in Vero cells. These results demonstrate that rIBVs are able to express S1 subunits from genetically diverse strains of IBV, which will enable the rational design of a future generation of IBV vaccines that may be grown in Vero cells.

A Recombinant Newcastle Disease Virus (NDV) Expressing S Protein of Infectious Bronchitis Virus (IBV) Protects Chickens against IBV and NDV

Infectious bronchitis virus (IBV) causes a highly contagious respiratory, reproductive and urogenital tract disease in chickens worldwide, resulting in substantial economic losses for the poultry industry. Currently, live-attenuated IBV vaccines are used to control the disease. However, safety, attenuation and immunization outcomes of current vaccines are not guaranteed. Several studies indicate that attenuated IBV vaccine strains contribute to the emergence of variant viruses in the field due to mutations and recombination. Therefore, there is a need to develop a stable and safe IBV vaccine that will not create variant viruses. In this study, we generated recombinant Newcastle disease viruses (rNDVs) expressing the S1, S2 and S proteins of IBV using reverse genetics technology. Our results showed that the rNDV expressing the S protein of IBV provided better protection than the rNDV expressing S1 or S2 protein of IBV, indicating that the S protein is the best protective antigen of IBV. Immunization of 4-week-old SPF chickens with the rNDV expressing S protein elicited IBV-specific neutralizing antibodies and provided complete protection against virulent IBV and virulent NDV challenges. These results suggest that the rNDV expressing the S protein of IBV is a safe and effective bivalent vaccine candidate for both IBV and NDV.

Viral interference between low pathogenic avian influenza H9N2 and avian infectious bronchitis viruses in vitro and in ovo

BackgroundLow pathogenic avian influenza (LPAI) H9N2 and infectious bronchitis virus (IBV) are important pathogens of poultry, causing important economic losses for the sector. Replication interference between these two viruses was described using cell cultures (CC) and embryonated chicken eggs (ECE). Chicken embryo lung (CEL) and ECE were simultaneously or sequentially infected with IBV vaccine strain (H120) and LPAIV-H9N2 (A/Ck/TUN/145/2012) to evaluate viral interactionsin vitro and in ovo, respectively. Real-time RT-PCR was developed to specifically quantify both AIV and IBV genomes as well as viral gene copy numbers during mixed infections. The amount of IL-1 beta, in supernatants of co-infected cell cultures, was determined using an ELISA assay. ResultsQuantitative results of AIV and IBV co-infection showed that interferences between the two viruses yielded decreased viral growth. However, in the case of super-infection, the second virus, either AIV or IBV, induced a decrease in the growth of the first inoculated virus. ConclusionIt appears that either AIV or IBV has a negative impact on the other virus growth when they are inoculated simultaneously or sequentially. The ELISA results showed that higher level of secreted IL-1beta varies, depending on the viral interference conditions between both viruses, during mixed infections.

Differentiation of infectious bronchitis virus vaccine strains Ma5 and 4/91 by TaqMan real-time PCR

The aim of this study was to develop rapid molecular assays for differentiating vaccine strains Ma5 and 4/91 of the infectious bronchitis virus (IBV). Specific primers and probes for S1 and N genes were designed based on the nucleotide sequences of both vaccine strains. Cross-reactivity was not observed. Assay sensitivity was 2.373 × 103 copies of the Ma5 strain, and 3.852 x 103 copies of the 4/91 strain. Samples belonging to a known genotype demonstrated that the designed assays supported rapid and sensitive detection of Ma5 and 4/91 vaccine strains of IBV.

Investigation of Infectious Bronchitis Virus Strains by Real Time RT-PCR and S1 Gene Sequencing in Broilers

In this study, detection of infectious bronchitis virus (IBV) from chicken tracheal swab samples by real time RT-PCR, which was reported as a rapid and sensitive virus detection method, was aimed. Phylogenetic relations in different field and variant strains of IBV by sequencing of hyper variable regions (HVRs) of S1 gene of IBV was determined. Tracheal swabs were taken from 120 broiler chickens with respiratory signs, randomly. Samples were inoculated into the allantoic fluids (AF) of SPF embryonated chicken eggs. RNAs were extracted by AF. RNAs were translated to ss cDNAs. Real time RT-PCR was performed with double labelled Taqman probe, IBV 5 GU391 and IBV5 GL533 primer pairs. Positive results were obtained in 33 samples of 120 (27.5 %) by real time RT-PCR. cDNAs from positive samples were used for amplification HVRs (Hyper Variable Regions) in S1 gene region with C2U and Ag0723 primers. Samples were amplified by S1 5’mod and CK2 primers, too. RT-PCR products were sequenced directly. Sequencing results have been compared with NCBI’s nucleotide database. Sequencing results were matched to some variant IBV strains in gen banks database at the rate of 72-86 %. These results support that we are faced with variant IBV strains. Also, we observed a lot of SNP mutations in alignment. This study shows that birds can be infected by IBV variant strains at rate of 27.5 %, although they were vaccinated by classic type vaccine. These results demonstrate that vaccination by classical vaccine strains of IBV cannot provide enough cross protection against variant strains. Therefore, outbreaks of the disease still occur in vaccinated flocks. Also, we found these primers are not enough for all IBV field strains to be sequenced and classified. Thus, different primers should be developed and used primer pairs more than two. In this experiment, we found virus load is more in AF than swab samples because of IBV replication in SPF egg AF. We observed dwarfism and hemorrhages at 14 days old chick embryos

Full-length genome sequencing analysis of avian infectious bronchitis virus isolate associated with nephropathogenic infection

Infectious bronchitis virus (IBV) produces infectious bronchitis (IB) disease in poultry worldwide. In spite of proper vaccinations against the IBV, new IBV strains are continually emerging worldwide. In this study, a new highly virulent nephropathogenic IBV strain named CK/CH/XDC-2/2013 was identified from a vaccinated flock with clinical signs of IB in the Jiangsu province of China. The full-length genome sequence of the isolate was 27,714 nucleotides long, and the genome was organized similarly to classical IBV strains. Minimum divergence, phylogenetic analysis, and distance matrix of the genome showed that the CK/CH/XDC-2/2013 isolate had the highest similarity to the IBV BJ strain. The spike glycoprotein (S) gene had the greatest similarity to the nephropathogenic BJ strain and showed an 8 amino acid insertion (YSNGNSDV) at 73 to 80 sites and 3 amino acid deletion at sites 126 to 128 compared to the IBV vaccine strains. A recombination analysis of the S gene showed that the new isolate evolved from the IBV BJ strain and the KM91 vaccine strain. An animal challenge experiment showed a mortality of 60 to 80% in early-age chickens by different inoculation routes. Pathological examinations of the kidneys revealed inflammation, distention with uric acid deposits, and tubular degeneration. It indicated that the CK/CH/XDC-2/2013 isolate has robust kidney tissue tropism, and new nephropathogenic IBV strains are continuously evolving in China.

Genetic mutations in live infectious bronchitis vaccine viruses following single or dual in vitro infection of tracheal organ cultures.

Despite regular co-vaccination of two different strains of live infectious bronchitis vaccine viruses, little is known about possible mutations in these viruses following vaccination. As an alternative to chicks, this study used an in vitro infection model to identify single-nucleotide polymorphisms (SNPs) within the part-S1 gene of two live infectious bronchitis virus vaccine strains (793B and Massachusetts) following single or dual inoculation onto tracheal organ cultures. Results indicate that viral titres reduced over the duration of the study; conversely, the amount of detected infectious bronchitis virus genome increased. Results demonstrate a greater number of non-synonymous SNPs in both vaccine strains when they are co-inoculated, compared with the single inoculations. The influence of the increased SNP and hydrophobic properties of the translated proteins on the vaccine viruses' virulence is unknown.

The effect of Allium sativum (Garlic) extract on infectious bronchitis virus in specific pathogen free embryonic egg.

Garlic is a plant has been used as a flavor, and anti-microbial and anti-diarrheal agent. Infectious bronchitis virus (IBV) is a coronavirus. The available vaccines against IBV cannot cover new variants. This study evaluated the inhibitory effects of garlic extract on IBV. The constituents of garlic extract were detected by gas chromatography. This study was done in four groups of embryonic SPF eggs; first group was used for virus titration; second group received the mixture of different virus titration and constant amount of garlic extract; third group received 10(-3) titration of virus and after 8 hr received garlic extract and the last group received different dilutions of garlic extract. Based on our results, in the second group, IBV vaccine strain (4/91) at all titration and M41 in 10(-2) and 10(-3) titration and in the third group both variants of virus the embryonic Index (EI) was significantly increased. The garlic extract had inhibitory effects on IBV in the chickens embryo.

Cross-Protection by Infectious Bronchitis Viruses Under Controlled Experimental Conditions.

Infectious bronchitis virus (IBV) cross-protection trials were performed in healthy chickens maintained under controlled environmental conditions. Chickens primed or primed and boosted with a Massachusetts (Mass)-type attenuated vaccine were subsequently challenged with either IBV Arkansas (Ark) or GA13-type virulent strains. In addition, Ark-vaccinated chickens were challenged with IBV GA13. Spike protein 1 (S1) amino acid identities between IBV vaccine and challenge strains varied from 76.0% to 77.3%. Contrary to expectations, assessments of clinical signs, viral load, and histopathology indicated a significant level of cross-protection among these antigenically distant IBV strains. Moreover, prime and booster vaccination with Mass protected against GA13 and improved protection against Ark when compared with Mass single vaccination. These results emphasize the need to include both single vaccination control groups and control groups primed and boosted with a single serotype when testing the efficacy of IBV protectotypes and/or novel IBV vaccine combinations against heterologous serotypes under controlled experimental conditions. Such controls are of distinct importance in experiments supporting the introduction of attenuated IBV vaccine strains exotic to regions, since these exotic strains may provide new genetic material for recombination and emergence of novel IBV strains.

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.