Avian infectious bronchitis virus (AIBV) review by continent

Inhibiting Infectious Bronchitis Virus PLpro Using Ubiquitin Variants

Infectious bronchitis virus (IBV) is a coronavirus first isolated in the 1930s infecting chickens. IBV causes great economic losses to the global poultry industry, as it affects egg production and causes mortality by leaving the host susceptible to secondary bacterial infections. Even though vaccines are available, they are poorly cross-protective against new variants of the virus, which are always on the cusp of emerging. Effective antiviral therapies, or possibly the production of transgenic animals immune to IBV infection, are therefore sorely needed. As the papain-like protease (PLpro) of IBV has deubiquitinating activity besides its crucial ability to cleave the viral polyprotein, we have applied a novel strategy of selecting ubiquitin variants (UbVs) from a phage-displayed library that have high affinity to this viral protease. These UbVs were found to inhibit the deubiquitinating activity of PLpro and consequently obstruct the virus's ability to evade the innate immune response in the host cell. By obstructing the proteolytic activity of PLpro, these UbVs were seemingly able to inhibit viral infection as assessed using immunofluorescence microscopy. Whilst virus infection was detected in around 5% of UbV-expressing cells, the virus was present in around 30-40% of GFP (control)-expressing cells. This suggests that the expression of UbVs indeed seems to inhibit IBV infection, making UbVs a potentially potent and innovative antiviral strategy in the quest for control of IBV infections.

Review of respiratory syndromes in poultry: pathogens, prevention, and control measures

Respiratory syndromes (RS) include a variety of diseases that lead to respiratory dysfunction, resulting in significant economic losses for the poultry industry. Infectious agents and unfavourable environmental factors cause these respiratory diseases, and rapid transmission, high morbidity rates, and frequent mixed infections characterise them. The challenge in preventing and treating these diseases arises from the complexity of their triggers and the potential for secondary infections. Current vaccines often do not provide effective prevention, and the overuse of certain medications can lead to increased bacterial resistance, complicating prevention and control efforts. This review article examines the common sources of respiratory infections in poultry flocks, including infectious bronchitis virus, avian influenza virus, Newcastle disease virus, infectious laryngotracheitis virus, avian metapneumovirus, pathogenic Escherichia coli, Haemophilus paragallinarum, Mycoplasma gallisepticum, and Chlamydia. It also considers non-infectious factors such as adverse environmental conditions and management errors. The article provides an updated, comprehensive overview of widespread and economically significant poultry respiratory pathogens. It briefly discusses detection technology and vaccine development based on the transmission characteristics of RS. Furthermore, it explores prevention and control measures such as combination drug strategies and antibiotic alternatives to enhance understanding and implementation of effective disease prevention and control measures.

A novel plant-derived recombinant COBRA infectious bronchitis virus spike protein can elicit a strong immune response in chickens

Infectious bronchitis virus (IBV) causes an acute respiratory disease in chickens of all ages, and is an economic burden on the global poultry industry. In severe cases, this virus can spread from the respiratory tract to urinary and reproductive organs, leading to kidney damage, poor egg quality, and high mortality rate of chickens. Among IBV glycoproteins, spike (S) is the major determinant of viral attachment to host receptors and induction of neutralizing antibodies. Rapid mutations were found within the S gene of numerous IBV strains presenting in multiple geographical locations. Since the early detection of IBV in the 1930s, no single control strategy has so far shown high efficacy in protecting chickens. The aim of this investigation was therefore to develop a novel S-subunit vaccine to prevent this disease. Using a design approach of Computationally Optimized Broadly Reactive Antigen (COBRA) and the Nicotiana benthamiana transient expression system, we have successfully generated a recombinant S protein comprising the most consensus amino acids of IBV strains circulating in Vietnam and surrounding areas. Importantly, our results showed that the plant-derived protein was able to induce a strong immune response in chickens with significantly high expression levels of IFN-γ, GZM-A, CD4, CD8 mRNAs in the peripheral blood. Remarkable titers of IgY specific antibodies were stably observed over a 5-week period post immunization by COBRA-S, which was in agreement with the reduction of clinical signs after virus challenge. This study contributes a potential direction to vaccine development coping with new IBV outbreaks in the future.

Emergence and Dissemination of the Avian Infectious Bronchitis Virus Lineages in Poultry Farms in South America

Infectious bronchitis virus (IBV) is a chicken pathogen present in commercial poultry farms worldwide. It is classified within the species Avian coronavirus, genus Gammacoronavirus. As with other members of the family Coronaviridae, it has a single positive-sense RNA genome with 27.6 Kb and presents viral particles with a typical crown-like aspect due to the spike (S) transmembrane glycoprotein. IBV has a remarkable capacity for genetic recombination and mutation, resulting in many genotypes and antigenic variants over evolutionary time. Currently, it is classified into nine genetic types (GI to GIX) and 41 (1 to 41) lineages disseminated worldwide. In South America, IBV was first identified in early commercial poultry production ventures in Brazil in the 1950s. Since then, this virus has been frequently detected in commercial South American poultry farms, being classified into serotypes in the first decades and genotypes more recently. IBVs of the Massachusetts (Mass) serotype were initially detected and vaccine strains of this serotype were used extensively on commercial poultry farms. Other serotypes/genotypes were identified later, with almost all of them classified in the current genetic type I (GI). In addition, five GI lineages (GI-1, -11, -13, -16, and -23) have been associated with the main infectious bronchitis outbreaks in the continent, with some variations in the occurrence according to the countries and the period of time. Molecular epidemiological surveillance of IBV genetic types and lineages is necessary to anticipate potential outbreaks, revealing patterns of viral evolution and dissemination, as well as to guide the selection of appropriate vaccine strains and immunization programs.

Seven infectious bronchitis virus genotypes including South American-origin G1-11 and Asian-origin GVI-1 circulated in southern African poultry from 2010 to 2020

Infectious bronchitis virus (IBV) affects the respiratory, urogenital and reproductive systems of chickens and causes major economic losses. Biosecurity and vaccinations are used to limit the disease's impact, and identifying the circulating strains is important for selecting appropriate vaccines. The partial spike (S1) genes of 364 IBVs, isolated from commercial chickens in Botswana, Eswatini, Namibia and South Africa from 2010 to 2020, were phylogenetically analyzed. Seven genotypes were identified: 184 viruses (50,5 %) were classified as genotype GI-19 (QX) and 78 (21,4 %) were GI-1 (Mass/H120). Thirty-nine (10,7 %) were genotype GI-13 (4/91), 29 (8,0 %) were GVI-1 (TC07-2), 19 (5,2 %) were GI-23 (Variant 2), and 13 (3,6 %) were GI-11 (UFMG/G-Brazil). Two (0.5 %) viruses belonged to the GIV-1 (DE/072/92) genotype. Genotype GI-11 had not been reported outside South America before but has evidently circulated in South Africa for at least a decade. Similarly, genotype GVI-1, previously thought to be restricted to Asia, has been present in southern Africa since at least 2010. Prior to 2013, only Mass and H120 vaccines were permitted to be used in South Africa, but since 2013 793/B (GI-13), QX (GI-19), 4-91 (GI-13) and Variant 2 (GI-23) live attenuated vaccines were permitted. Accordingly, the four IBV variants we identified were putative recombinants of genotypes G1-1 and G1-19, G1-13 and G1-19, or G1-13 and unknown IBV strains, but these variant viruses did not spread extensively or persist in the region. The phylogenetic evidence points to imported contaminated poultry and poultry products as the source of new IBV genotypes in southern Africa.

Biosecurity Implications, Transmission Routes and Modes of Economically Important Diseases in Domestic Fowl and Turkey

The poultry industry is a critical source of affordable protein worldwide; however, it faces continuous threats from various poultry diseases that significantly impact public health, economic stability, and food security. Knowledge of and examination of the transmission routes, risk factors, and environmental survival characteristics of the most important pathogens affecting poultry populations, as well as the importance of strict biosecurity, are pivotal. Transmission routes are split into direct and vector-borne pathways, and indirect ways, which include infections via contaminated surfaces and vector-borne pathways, including insects and rodents. Avian influenza virus and Newcastle disease virus spread through respiratory droplets, and their transmission risk increases with increasing stocking density. While other pathogens (e.g., infectious bursal disease virus and Salmonella spp.), to persist long-term in the environments, for example, feed and litter, increasing the probability to persist long-term in the environments, for example, feed and litter, increasing the probability of infection. The long-term resilience of pathogens in multiple pathogens in various environmental conditions highlights the role of biosecurity, sanitation, and hygiene controls in preventing disease outbreaks. High stocking density in production systems, suboptimal ventilation, and inadequate biosecurity controls further increase transmission risks. This paper summarizes important disease transmissions and reinforces the need for strict biosecurity protocols and routine health monitoring to prevent the spread of pathogens within and beyond poultry facilities. These strategies can support safe poultry production, address growing global demand, and ensure food safety and public health.

Recombinant infectious bronchitis virus containing mutations in non-structural proteins 10, 14, 15, and 16 and within the macrodomain provides complete protection against homologous challenge

Infectious bronchitis virus (IBV) is the etiological agent of infectious bronchitis, an acute highly contagious economically important disease of chickens. Vaccination uses live attenuated vaccines (LAVs) that are generated via serial passage of a virulent field isolate through embryonated hens' eggs, typically 80-100 times. The molecular basis of attenuation is unknown and varies with each attenuation procedure. To investigate specifically targeted attenuation, we utilized reverse genetics to target the macrodomain 1 (Mac1) domain within non-structural protein 3 of the virulent M41 strain. Macrodomains are found in a variety of viruses, including coronaviruses, and have been associated with the modulation of the host's innate response. Two recombinant IBVs (rIBVs) were generated with specific single point mutations, either Asn42Ala (N42A) or Gly49Ser (G49S), within the Mac1 domain generating rIBVs M41K-N42A and M41K-G49S, respectively. Replication in vitro was unaffected, and the mutations were stably maintained during passaging in vitro and in ovo. While M41K-N42A exhibited an attenuated phenotype in vivo, M41K-G49S was only partially attenuated. The attenuated in vivo phenotypes observed do not appear to be linked to a reduction in viral replication and additionally M41K-N42A highlighted the N42A mutation as a method of rational attenuation. Vaccination of chickens with either rIBV M41K-N42A or a rIBV containing the Mac1 N42A mutation and our previously identified attenuating Nsp10 and 14 mutations, Pro85Leu and Val393Leu respectively, offered complete protection from homologous challenge. The presence of multiple attenuating mutations did not appear to negatively impact vaccine efficacy.

IMPORTANCE

Infection of chickens with the Gammacoronavirus infectious bronchitis virus (IBV) causes an acute respiratory disease, resulting in reduced weight gain and reductions in egg laying making it a global concern for poultry industries and food security. Vaccination against IBV uses live attenuated viruses (LAVs), generated by multiple passages of a virulent virus through embryonated hens' eggs. The molecular basis of attenuation is unknown and unpredictable requiring a fine balance between loss of virulence and vaccine efficacy. In this study, we targeted the macrodomain of IBV for rational attenuation demonstrating a single point mutation can result in loss of pathogenicity. An IBV vaccine candidate was subsequently generated containing three specific attenuating mutations, to reduce the risk of reversion, which completely protected chickens. The targets in this study are conserved among IBV strains and the coronavirus family offering a potential method of rational attenuation that can be universally applied for vaccine development.

Isolation, molecular identification, and phylogenetic analysis of infectious bronchitis virus from commercial chicken farms in Mekele and Bishoftu, Ethiopia, 2023-2024

BACKGROUND

Avian infectious bronchitis (IB) is a highly contagious respiratory disease that affects the poultry industry globally. The disease is caused by avian infectious bronchitis virus (IBV), member of the genus Gammacoronavirus. In Ethiopia, IBV has been reported in both commercial and backyard chickens based on clinical observation. The objectives of this study were to isolate the virus, conduct molecular based identification, and phylogenetic analysis of the circulating IBV isolates.

METHODS AND MATERIALS

A cross-sectional study was conducted between November 2023 and May 2024 in Mekele and Bishoftu, Ethiopia. A total of 49 clinical samples were collected, comprising 12 tissue samples and 39 pooled swab samples. Of these, 6 samples-specifically, 5 swab samples and 1 tissue sample-tested positive for infectious bronchitis virus (IBV) through virus-specific conventional RT-PCR and real-time PCR. Nested PCR was performed using serotype-specific primers. The purified PCR products, which targeted the spike glycoprotein S1 subunit gene and the 3' UTR of the IBV, were sequenced, followed by phylogenetic tree analysis.

RESULTS

The six positive samples propagated into specific pathogen free embryonated eggs and exhibited characteristic IBV lesions and mortality observed over five consecutive passages. IBV isolates from Bishoftu (n = 4) and Mekele (n = 2) were amplified using one-step RT-PCR to target 466 bp of the S1 subunit gene and 433 bp of the 3'UTR. A BLAST search on the S1 partial gene and 3'UTR sequences, nested PCR, and phylogenetic analysis revealed that the present IBV isolates are genetically similar to the Massachusetts serotype. The S1 gene sequences of the five IBV isolates were deposited in GenBank with accession numbers PQ389500 to PQ389504.

CONCLUSIONS

This is the first detailed study on IB virus isolation, molecular detection, sequencing, and phylogenetic analysis in Ethiopia. The findings revealed that the outbreaks were caused by the IB virus, which created a serious health risk and economic losses in the chicken industry. To the author's knowledge, this is the first comprehensive study on the isolation and genetic analysis of IBV in Ethiopia. Further research on the economic impact of IBV in chicken production, farm biosecurity, serotyping of circulating IB virus, and vaccine development based on the local serotypes is recommended.

Some novel field isolates belonging to lineage-1 of the genotype GI-avian infectious bronchitis virus (AIBV) show strong evidence of recombination with field/vaccinal strains

Avian infectious bronchitis virus (AIBV) infection remains one of the significant challenges for the poultry industry due to the high rates of morbidity, mortality, and poor production performance. The AIBV genome is prone to frequent changes due to the possibility of drift and recombination between various genotypes. Despite the massive administration of several types of vaccines, many outbreaks of AIBV continue to be reported worldwide. One of the major goals of this study was to monitor genetic changes in the viral genomes of some recent field isolates of the AIBV from broiler chickens. To achieve these goals, we tested several pools of tissue specimens (trachea and kidneys) from some suspected AIBV outbreaks in broiler chickens by quantitative real-time PCR (q-RT-PCR). We selected two samples, one from the trachea (IBV-4) and one from the kidney (AIBV-6), for the next-generation sequencing (NGS). The full-length genomes of these two isolates were deposited in the GenBank (Accession Numbers: PQ468962 and PQ468963). The viral genome size of AIBV-4 and AIBV-6 was 27,475 and 27,469 nucleotides in length. AIBV-4 have typical AIBV genome organization (5'UTR, ORF1a, ORF1b, S, 3a, 3b, E, M, 4b, 5a, 5b, N, and 3'UTR), while AIBV-6 lack 5b. These two AIBV isolates belong to sublineage-1 of the genotype GI-1 based on the phylogenetic using the full-length, the S, and the N protein sequences. The S1/S2 cleavage sites show polybasic amino acid sequences (RR-F-RR) as direct evidence of virulence of these isolates. The analysis shows multiple recombination events of these isolates with some natural and vaccine strains. The potential major parent for both AIBV-4 and AIBV-6 was AIBV Beaudette. Active and vigilant monitoring of the AIBV sequences of the currently circulating strains in chickens is highly encouraged to help develop novel vaccines and diagnostic assays that match the field circulating strains.

Revealing a novel GI-19 lineage infectious bronchitis virus sub-genotype with multiple recombinations in South Korea using whole-genome sequencing

Infectious bronchitis (IB), caused by the infectious bronchitis virus (IBV), is a highly contagious chicken disease, causing economic losses worldwide. New IBV strains and variants continue to emerge despite using inactivated and live-attenuated vaccines to prevent or control IB. In this study, the S1 genes of 46 IBV strains, isolated from commercial chicken flocks between 2003 and 2024 in Korea were sequenced and genetically characterized. The IBV isolates belonged to Korean group II (K-II), which was included in the GI-19 lineage. The K-II was divided into five sub-genogroups (a-e) based on phylogenetic tree analysis results and nucleotide identification of the S1 gene. Of these, K-IId was the most common genotype in Korea; however, eight novel isolates belonging to the K-IIe sub-genotype were discovered. The nucleotide and amino acid identities of the other four K-II sub-genotypes and the eight isolates were 84.42-95.89 % and 84.02-95.86 %, respectively. The complete genomes of the eight K-IIe isolates were obtained using next-generation sequencing. Various recombination patterns were observed despite the high homology of the S1 gene among the eight IBV strains. Among the eight K-IIe isolates, six were recombinants, exhibiting recombinations between K-IIe and K-IIc, K-IIe and K-IIa, and with the live vaccine strain. Most recombination breakpoints were detected in the nsp2 region of the ORF1a, S2, and M genes. The present study proposed new classification criteria for the K-II belonged to the GI-19 lineage prevalent in South Korea and revealed the recombination patterns of recently identified novel isolates, providing important information on novel viral sub-genotype strains and IBV evolution.

Current trends and future potential in the detection of avian coronaviruses: An emphasis on sensors-based technologies

Infectious bronchitis virus (IBV), an avian coronavirus, member of the genus Gammacoronavirus, poses significant threats to poultry health, causing severe respiratory, reproductive, and renal infections. The genetic diversity of IBV, driven by mutations, recombination and deletions, has led to the emergence of numerous serotypes and genotypes, complicating both diagnosis and control measures. Rapid and accurate diagnostic tools are essential for effective disease management and minimizing economic losses. Conventional diagnostic methods, such as PCR, virus isolation, and serological assays, are hindered by limitations in sensitivity, specificity, and turnaround time. In contrast, innovative biosensor platforms employing advanced detection mechanisms-including electrochemical, optical, and piezoelectric sensors-offer a transformative solution. These technologies provide portable, highly sensitive, and rapid diagnostic platforms for IBV detection. Beyond addressing the challenges of conventional methods, these biosensor-based approaches facilitate real-time monitoring and enhance disease surveillance. This review highlights the transformative potential of biosensors and their integration into diagnostic strategies for avian coronavirus infections, presenting them as a promising alternative for precise and efficient IBV detection.

Infectious Bronchitis Virus (IBV) in Vaccinated and Non-Vaccinated Broilers in Brazil: Surveillance and Persistence of Vaccine Viruses

Infectious bronchitis virus (IBV) poses a significant threat to poultry worldwide, necessitating robust surveillance and vaccination strategies. This study aimed to conduct IBV surveillance in Brazil, assess potential vaccine viral escapes, and evaluate vaccine persistence in vaccinated broilers. A total of 1000 tracheal swabs from 100 flocks across six states were analyzed using RT-PCR. The results showed that 91% of the flocks tested positive for IBV. The detected strains included GI-1, GI-11, and GI-23. Notably, 90% of batches received vaccines containing either GI-1 or GI-11 lineages. The study revealed vaccine persistence in 67 samples between days 16 and 32 post-vaccination. In contrast, unvaccinated batches had a high prevalence of IBV GI-11 strains (70%). These findings highlight widespread IBV circulation in Brazil with persistent viral presence in vaccinated birds and wild viruses in unvaccinated ones. Collectively, the data reveal a widespread presence of IBV in Brazil, characterized by prolonged viral persistence in vaccinated animals and the occurrence of wild viruses in both unvaccinated birds and those vaccinated against specific strains. It can be concluded from this study that there was a widespread occurrence of IBV in Brazil, providing long viral persistence in vaccinated animals, as well as the occurrence of wild virus in unvaccinated birds or birds vaccinated against individual strains.

The battle between infectious bronchitis virus and innate immunity: A mini review

Infectious bronchitis virus (IBV) is the causative agent of infectious bronchitis (IB), leading to acute or persistent infections in poultry. IBV triggers innate immune response, and the production of interferon (IFN) varies depending on the viral strains and host cell types. To evade the host immune system, IBV has developed numerous immune escape strategies. These include hijacking host proteins, modulating protein synthesis, antagonizing IFN production, promoting autophagosome formation and expansion, manipulating apoptosis, blocking antigen presentation, stabilizing viral mRNA, and inhibiting stress granule (SG) formation. The ongoing interaction between IBV and the host immune system reflects a dynamic battle, as the virus employs various tactics to ensure its replication. Understanding these pathogenic mechanisms of IBV is crucial for developing effective control measures.

Dynamic Immune Response Landscapes of Avian Peripheral Blood Post-Vaccination Against Infectious Bronchitis Virus Infection

Background/Objectives: Despite decades of extensive vaccinations against avian infectious bronchitis virus (IBV) infection, outbreaks caused by constantly emerging variants due to genome recombination between different viral strains, including vaccine strains, occur annually worldwide. The development of novel vaccines with favorable safety and effectiveness is required but is hindered by a limited understanding of vaccination against IBV. Methods: Here, we performed a comprehensive analysis of the in vivo dynamics of peripheral blood mononuclear cells (PBMCs) in specific pathogen-free chickens inoculated with the widely used live attenuated IBV vaccine strain H120 at single-cell level, using high-throughput single-cell transcriptome sequencing (scRNA-seq). Results: High-quality sequencing dataset for four scRNA-seq data containing the transcriptomes of 29,846 individual chicken PBMCs were obtained, defining 22 populations and 7 cell types based on distinct molecular signatures and known markers. Further integrative analysis constructed the time series dynamic cell transition and immune response landscapes within the two weeks post-prime vaccination against IBV. Enhanced crosstalk between antigen-presenting cells and T lymphocytes was revealed as early as four days post-vaccination. The specific immune cell populations and their comprehensive cellular and molecular networks involved in the initiation phase of antiviral adaptive immune responses were elucidated in details. Conclusions: Our study provides a comprehensive view of the dynamic initiation of immune responses in chickens against IBV infection at the cellular and molecular levels, which provides theoretical support and potential solutions for the future rational design of safe and effective vaccines, the augmentation of the efficacy of current vaccines, and the optimization of immune programs.

Clinical, pathological, and genotypic analysis of infectious bronchitis virus in broiler chickens in the Abu Dhabi Emirate, United Arab Emirates

Background

Infectious Bronchitis (IB), caused by the infectious bronchitis virus (IBV), is a significant contagious respiratory disease in the poultry industry. The emergence of new variants represents a global challenge for the diagnosis and control of the disease. Despite vaccination efforts in poultry farms in the Abu Dhabi Emirate, United Arab Emirates (UAE), outbreaks continue to occur, raising concerns about the efficacy of vaccination protocols and the potential emergence of new viral strains. This study aims to provide information on clinical, pathological, and genotypes of IBV detected within the Abu Dhabi Emirate, during 2022-2023.

Methods

Epidemiological data were collected from twelve suspected IB outbreaks across seven broiler farms located in the Abu Dhabi Emirate. The cases were investigated through clinical and pathological examinations and Forty-six samples, including lung, spleen, kidney tissues, and oro-cloacal swabs, were collected for further analysis. The virus was detected by RT-qPCR assay, genotyping was determined by phylogenetic analysis of the Spike (S)-1 gene, and differentiation between field and vaccine strains was determined by comparing their sequences.

Results

The age of the affected flocks varies from 2 to 5 weeks. The highest morbidity, mortality and case fatality rates were 36, 33, and 95%, respectively. Necropsy examination revealed characteristic respiratory and renal pathological lesions. Phylogenetic analysis revealed a co-circulation of three lineages of IBV genotype GI-13 or 4/91 serotype (81.8%), GI-1 or Massachusetts serotype (9.1%) and GI-23 or Middle East serotype (9.1%). Approximately 90.9% of the strains classified within GI-1 and G1-13 lineages are 99 to 100% identical to 4/91 and Mass serotypes, respectively, and are considered as vaccine strains. Two strains (9.1%) classified within GI-23 lineage have a < 99% identity to the 4/91 and Mass serotypes vaccine strains and are considered as filed strains.

Conclusion

Co-circulation of three IBV lineages (GI-13, GI-1, and GI-23) in the Abu Dhabi broiler flocks showing IB symptoms were detected. This complex scenario of different IBV lineages circulation may account for the persistent outbreaks despite vaccination efforts. The results of the study are crucial for optimum IB vaccination and monitoring strategies or designing new vaccines based on local IBV field strains.

Laboratory safety and immunogenicity evaluation of live attenuated avian infectious bronchitis GI-23 virus vaccine

Avian infectious bronchitis virus (IBV) is responsible for a highly contagious disease that poses a significant threat to the poultry industry due to its high rates of evolution. The occurrence of vaccination failure can frequently be attributed to the emergence of novel strains that exhibit antigenic divergence from conventional vaccine strains. This study aims to evaluate the safety and efficacy of the Eg/1212B-based live attenuated virus vaccine indicated for immunization of chickens against nephropathogenic GI-23 variant strains reported globally. Studies were designed in compliance with European Pharmacopeia Ph. Eur. 0442. The attenuated vaccine virus did not exhibit any tendency to revert or increase in virulence after five back-passages in SPF chickens. Ciliostasis scores and kidney lesions (histology) were comparable between vaccinated and control birds. No chicken showed clinical signs of an infection with IBV or died from causes attributable to the vaccine after receiving a 10× overdose. A single vaccination was able to protect the birds in a challenge model with a recent European wild-type IBV strain. The study demonstrated an onset of immunity of 21 days and a duration of immunity lasting up to 56 days. Vaccination administered individually through the ocular route resulted in a protection rate of 100 % to 85 %, whereas mass application by spraying offered a protection rate of 85 % to 80 %. In conclusion, the safety and efficacy data confirm a positive benefit/risk balance, and the investigated product can be considered a suitable vaccine candidate for controlling avian infectious bronchitis nephropathogenic variant strains related to GI-23.

Virus-like Particles Produced in Plants: A Promising Platform for Recombinant Vaccine Development

The capsid proteins of many viruses are capable of spontaneous self-assembly into virus-like particles (VLPs), which do not contain the viral genome and are therefore not infectious. VLPs are structurally similar to their parent viruses and are therefore effectively recognized by the immune system and can induce strong humoral and cellular immune responses. The structural features of VLPs make them an attractive platform for the development of potential vaccines and diagnostic tools. Chimeric VLPs can be obtained by attaching foreign peptides to capsid proteins. Chimeric VLPs present multiple copies of the antigen on their surface, thereby increasing the effectiveness of the immune response. Recombinant VLPs can be produced in different expression systems. Plants are promising biofactories for the production of recombinant proteins, including VLPs. The main advantages of plant expression systems are the overall low cost and safety of plant-produced products due to the absence of pathogens common to plants and animals. This review provides an overview of the VLP platform as an approach to developing plant-produced vaccines, focusing on the use of transient expression systems.

Detection and Molecular Characterization of GI-1 and GI-23 Avian Infectious Bronchitis Virus in Broilers Indicate the Emergence of New Genotypes in Bolivia

Infectious Bronchitis Virus (IBV) is a major threat to the poultry industry worldwide, causing significant economic losses. While the virus's genetic structure is well understood, the specific strains circulating in Bolivia have remained uncharacterized until now. This study aimed to identify and characterize new IBV strains in Bolivia. Tissue samples from broilers exhibiting clinical signs of Infectious Bronchitis were screened to detect IBV using real-time RT-PCR (RT-qPCR). Positive samples with low cycle threshold (Ct) values were selected for sequencing the full S1 gene. Of the 12 samples analyzed, 10 were determined to be positive for IBV. However, only four samples yielded sufficient genetic material for sequencing and subsequent phylogenetic analysis. The results revealed the presence of GI-1 and GI-23 lineages, both belonging to genotype I (GI). The GI-1 lineage showed >99% sequence identity to the H120 and Massachusetts vaccine strains, suggesting a close relationship. In contrast, the GI-23 lineage clustered with other IBV strains, showing a distinct subclade that is genetically distant from Brazilian strains. No evidence of recombination was found. Furthermore, amino acid substitution analysis identified specific mutations in the S1 subunit, particularly in the hypervariable regions 1, 2, and 3. These mutations could potentially alter the virus's antigenicity, leading to reduced vaccine efficacy. The findings of this study highlight the importance of continued and broad genomic surveillance of circulating IBV strains and the need to improve vaccination strategies in Bolivia.

Potential Transcriptional Enhancers in Coronaviruses: From Infectious Bronchitis Virus to SARS-CoV-2

Coronaviruses constitute a global threat to human and animal health. It is essential to investigate the long-distance RNA-RNA interactions that approximate remote regulatory elements in strategies, including genome circularization, discontinuous transcription, and transcriptional enhancers, aimed at the rapid replication of their large genomes, pathogenicity, and immune evasion. Based on the primary sequences and modeled RNA-RNA interactions of two experimentally defined coronaviral enhancers, we detected via an in silico primary and secondary structural analysis potential enhancers in various coronaviruses, from the phylogenetically ancient avian infectious bronchitis virus (IBV) to the recently emerged SARS-CoV-2. These potential enhancers possess a core duplex-forming region that could transition between closed and open states, as molecular switches directed by viral or host factors. The duplex open state would pair with remote sequences in the viral genome and modulate the expression of downstream crucial genes involved in viral replication and host immune evasion. Consistently, variations in the predicted IBV enhancer region or its distant targets coincide with cases of viral attenuation, possibly driven by decreased open reading frame (ORF)3a immune evasion protein expression. If validated experimentally, the annotated enhancer sequences could inform structural prediction tools and antiviral interventions.

Current Status of Poultry Recombinant Virus Vector Vaccine Development

Inactivated and live attenuated vaccines are the mainstays of preventing viral poultry diseases. However, the development of recombinant DNA technology in recent years has enabled the generation of recombinant virus vector vaccines, which have the advantages of preventing multiple diseases simultaneously and simplifying the vaccination schedule. More importantly, some can induce a protective immune response in the presence of maternal antibodies and offer long-term immune protection. These advantages compensate for the shortcomings of traditional vaccines. This review describes the construction and characterization of primarily poultry vaccine vectors, including fowl poxvirus (FPV), fowl adenovirus (FAdV), Newcastle disease virus (NDV), Marek's disease virus (MDV), and herpesvirus of turkey (HVT). In addition, the pathogens targeted and the immunoprotective effect of different poultry recombinant virus vector vaccines are also presented. Finally, this review discusses the challenges in developing vector vaccines and proposes strategies for improving immune efficacy.