Viral diseases of the respiratory system

Molecular Detection of Respiratory Tract Viruses in Chickens at the Point of Need by Loop-Mediated Isothermal Amplification (LAMP)

Accurate and timely molecular diagnosis of respiratory diseases in chickens is essential for implementing effective control measures, preventing the spread of diseases within poultry flocks, minimizing economic loss, and guarding food security. Traditional molecular diagnostic methods like polymerase chain reaction (PCR) require expensive equipment and trained personnel, limiting their use to centralized labs with a significant delay between sample collection and results. Loop-mediated isothermal amplification (LAMP) of nucleic acids offers an attractive alternative for detecting respiratory viruses in broiler chickens with sensitivity comparable to that of PCR. LAMP's main advantages over PCR are its constant incubation temperature (∼65 °C), high amplification efficiency, and contaminant tolerance, which reduce equipment complexity, cost, and power consumption and enable instrument-free tests. This review highlights effective LAMP methods and variants that have been developed for detecting respiratory viruses in chickens at the point of need.

A critical assessment of the cellular defences of the avian respiratory system: are birds in general and poultry in particular relatively more susceptible to pulmonary infections/afflictions?

In commercial poultry farming, respiratory diseases cause high morbidities and mortalities, begetting colossal economic losses. Without empirical evidence, early observations led to the supposition that birds in general, and poultry in particular, have weak innate and adaptive pulmonary defences and are therefore highly susceptible to injury by pathogens. Recent findings have, however, shown that birds possess notably efficient pulmonary defences that include: (i) a structurally complex three-tiered airway arrangement with aerodynamically intricate air-flow dynamics that provide efficient filtration of inhaled air; (ii) a specialised airway mucosal lining that comprises air-filtering (ciliated) cells and various resident phagocytic cells such as surface and tissue macrophages, dendritic cells and lymphocytes; (iii) an exceptionally efficient mucociliary escalator system that efficiently removes trapped foreign agents; (iv) phagocytotic atrial and infundibular epithelial cells; (v) phagocytically competent surface macrophages that destroy pathogens and injurious particulates; (vi) pulmonary intravascular macrophages that protect the lung from the vascular side; and (vii) proficiently phagocytic pulmonary extravasated erythrocytes. Additionally, the avian respiratory system rapidly translocates phagocytic cells onto the respiratory surface, ostensibly from the subepithelial space and the circulatory system: the mobilised cells complement the surface macrophages in destroying foreign agents. Further studies are needed to determine whether the posited weak defence of the avian respiratory system is a global avian feature or is exclusive to poultry. This review argues that any inadequacies of pulmonary defences in poultry may have derived from exacting genetic manipulation(s) for traits such as rapid weight gain from efficient conversion of food into meat and eggs and the harsh environmental conditions and severe husbandry operations in modern poultry farming. To reduce pulmonary diseases and their severity, greater effort must be directed at establishment of optimal poultry housing conditions and use of more humane husbandry practices.

Genome Sequencing and Characterization of an Avian Orthoavulavirus 1 VG/GA-like Isolate with a Unique Fusion Cleavage Site Motif

A complete genome sequence of a VG/GA -like strain of avian orthoavulavirus 1 (AOAV-1) was identified by nontargeted next-generation sequencing of an oropharyngeal swab sample collected from a carcass of a 12-mo-old backyard chicken. The isolate has a fusion (F) protein cleavage site motif consistent with a low virulent AOAV-1, but it has a unique motif with phenylalanine at position 117 (¹¹²G-R-Q-G-R↓F¹¹⁷), which is typical for virulent AOAV-1 strains. The one nucleotide difference at the cleavage site compared to other low-virulence viruses made the isolate detectable by F-gene-specific real-time reverse transcription-PCR (rRT-PCR) developed as a diagnostic test to specifically detect virulent strains. The mean death time determined in eggs and intracerebral pathogenicity index determined in chickens classified the isolate as lentogenic. This is the first report of a lentogenic VG/GA-like virus with a phenylalanine residue at position 117 of the F protein cleavage site in the United States. In addition to concern for potential pathogenic shift of the virus through additional changes at the cleavage site, our finding warrants increased awareness of diagnosticians of potential false positive F-gene rRT-PCR tests.

Vaccines against Major Poultry Viral Diseases: Strategies to Improve the Breadth and Protective Efficacy

The poultry industry is the largest source of meat and eggs for human consumption worldwide. However, viral outbreaks in farmed stock are a common occurrence and a major source of concern for the industry. Mortality and morbidity resulting from an outbreak can cause significant economic losses with subsequent detrimental impacts on the global food supply chain. Mass vaccination is one of the main strategies for controlling and preventing viral infection in poultry. The development of broadly protective vaccines against avian viral diseases will alleviate selection pressure on field virus strains and simplify vaccination regimens for commercial farms with overall savings in husbandry costs. With the increasing number of emerging and re-emerging viral infectious diseases in the poultry industry, there is an urgent need to understand the strategies for broadening the protective efficacy of the vaccines against distinct viral strains. The current review provides an overview of viral vaccines and vaccination regimens available for common avian viral infections, and strategies for developing safer and more efficacious viral vaccines for poultry.

Molecular characterization of the S1 gene in GI-17 and GI-13 type isolates of avian infectious bronchitis virus (IBV) in Costa Rica, from 2016 to 2019

Avian infectious bronchitis is one of the most important respiratory diseases affecting poultry production worldwide. The etiological agent of this disease is the avian infectious bronchitis virus (IBV). We analyzed 14 isolates of IBV obtained from poultry farms in Costa Rica, from 2016 through 2019. We sequenced the S1 region of the genome and the sequences obtained were submitted to GenBank. Phylogenetic analyses showed that the isolates obtained during 2016-2017 belong to the GI-17 lineage and are related to the Georgia 13-type Ga-13/14255/14 and CK/CR/1160/16 variants, with a 96.90-100% nucleotide sequence identity and a 92.25-100% amino acid sequence identity. The main differences were detected in the RBD and HVR-3 regions, where a series of mutations eliminate an N-glycosylation site in 10 out of 11 isolates. The isolates obtained during 2018-2019 belong to the GI-13 lineage and are closely related to the 4/91 vaccine variant, with over 98% sequence identity at the nucleotide and amino acids levels. Variations were detected in the RBD and HVR regions, with a possible N-glycosylation site detected in isolate CK/CR/0632/19. These results indicate that a GA13-like pathogenic variant circulated during the 2016-2017 period and that the 4/91 variant was detected after the introduction of the vaccine. The variations shown in both the GA13-like and 4/91 isolates examined, reveal the need for continuous surveillance of IBV in Costa Rica, to detect new variants that may be introduced to the country or develop during outbreaks. This information is highly relevant for vaccination planning and disease management programs.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13337-022-00762-2.

Infectious Bronchitis Virus Infection Increases Pathogenicity of H9N2 Avian Influenza Virus by Inducing Severe Inflammatory Response

Infectious bronchitis virus (IBV) and H9N2 avian influenza virus (AIV) are frequently identified in chickens with respiratory disease. However, the role and mechanism of IBV and H9N2 AIV co-infection remain largely unknown. Specific-pathogen-free (SPF) chickens were inoculated with IBV 2 days before H9N2 virus inoculation (IBV/H9N2); with IBV and H9N2 virus simultaneously (IBV+H9N2); with H9N2 virus 2 days before IBV inoculation (H9N2/IBV); or with either IBV or H9N2 virus alone. Severe respiratory signs, pathological damage, and higher morbidity and mortality were observed in the co-infection groups compared with the IBV and H9N2 groups. In general, a higher virus load and a more intense inflammatory response were observed in the three co-infection groups, especially in the IBV/H9N2 group. The same results were observed in the transcriptome analysis of the trachea of the SPF chickens. Therefore, IBV might play a major role in the development of respiratory disease in chickens, and secondary infection with H9N2 virus further enhances the pathogenicity by inducing a severe inflammatory response. These findings may provide a reference for the prevention and control of IBV and H9N2 AIV in the poultry industry and provide insight into the molecular mechanisms of IBV and H9N2 AIV co-infection in chickens.

Quantitative real-time PCR assays for the concurrent diagnosis of infectious laryngotracheitis virus, Newcastle disease virus and avian metapneumovirus in poultry

Newcastle disease (ND), infectious laryngotracheitis (ILT) and avian metapneumovirus (aMPV) can be similar making it critical to quickly differentiate them. Herein, we adapted pre-existing molecular-based diagnostic assays for NDV and ILTV, and developed new assays for aMPV A and B, for use under synchronized thermocycling conditions. All assays performed equivalently with linearity over a 5 log₁₀ dynamic range, a reproducible (R² > 0.99) limit of detection of ≥ 10 target copies, and amplification efficiencies between 86.8%–98.2%. Using biological specimens for NDV and ILTV showed 100% specificity. Identical amplification conditions will simplify procedures for detection in diagnostic laboratories.

Development and application of a novel triplex protein microarray method for rapid detection of antibodies against avian influenza virus, Newcastle disease virus, and avian infectious bronchitis virus

Avian influenza virus (AIV), Newcastle disease virus (NDV), and avian infectious bronchitis virus (IBV) inflict immense damage on the global poultry industry annually. Serological diagnostic methods are fundamental for the effective control and prevention of outbreaks caused by these viruses. In this study, a novel triplex protein microarray assay was developed and validated for the rapid and simultaneous visualized detection of antibodies against AIV, NDV, and IBV in chicken sera. The AIV nuclear protein (NP), NDV phosphoprotein (P), and IBV nonstructural protein 5 (nsp5) were produced in a prokaryotic expression system, purified, and immobilized onto an initiator integrated poly(dimethylsiloxane) (iPDMS) film as probes to detect antibodies against these viruses in chicken sera. After optimization of the reaction conditions, no cross-reactivity was detected with infectious bursal disease virus, avian leukosis virus subgroup J and chicken anemia virus antisera. The lowest detectable antibody titers in this assay corresponded to hemagglutination inhibition (HI) titers of 2⁴ and 2¹ for AIV and NDV, respectively, and to an IDEXX antibody titer of 10³ for IBV, using the HI assay and IDEXX commercial ELISA kit as the reference methods. When156 serum samples were tested using the new assay, the HI test and the IBV IDEXX ELISA kit, the assay showed 96.8% (151/156), 97.4% (152/156) and 99.4% (155/156) diagnostic accuracy for detection of AIV, NDV and IBV antibody, respectively. The current study suggests that the newly developed triplex microarray is rapid, sensitive, and specific, providing a viable alternative assay for AIV, NDV, and IBV antibody screening in epidemiological investigations and vaccination evaluations.

Evaluation of humoral immune responses to enterotropic lentogenic VG/GA vaccine of Newcastle disease in commercial turkey poults (Meleagris gallopavo)

Background

Villegas-Glisson/University of Georgia (VG/GA) strain of Newcastle disease virus (NDV) is recommended for the initial vaccination of commercially reared turkey poults. However, the vaccine-induced antibody responses have not been studied in this species. The level of systemic humoral immune responses against the NDV was investigated in commercial turkey poults vaccinated with the VG/GA vaccine. One hundred eighty-two hybrid strain of turkey poults (Meleagris gallopavo) were divided randomly into vaccinated and unvaccinated groups. The vaccinated group was given the VG/GA vaccine at 10 and 20 days of age. To investigate the vaccine immunity, the level of specific IgY and IgA in serum samples were determined using ELISA and haemagglutination inhibition assays (HI). The biological half-life of maternal antibodies was also determined before the immunization.

Results

VG/GA-specific antibodies were detected in the vaccinated turkey poults and were significantly higher in the vaccinated group compared to the unvaccinated group. IgY and IgA antibodies showed a significant increase in titers 14 days after the second vaccination and reached a peak on day 35 of age. The correlation coefficient and intra-rater reliability showed a significant correlation between the HI titers and IgY/IgA ELISA values. Maternal IgY and IgA levels were found to decline in the serum with half-lifes of 7.68 ± 2.35 and 2.18 ± 0.82 days, respectively.

Conclusions

Enterotropic lentogenic VG/GA vaccine induced a marked humoral immune response against the NDV in turkey poults. The positive correlation between IgY and IgA highlights the role of these two antibody classes in controlling the Newcastle disease in turkey poults.

Presence of Newcastle disease viruses of sub-genotypes Vc and VIn in backyard chickens and in apparently healthy wild birds from Mexico in 2017

Virulent Newcastle disease viruses (NDV) have been present in Mexico since 1946, and recently, multiple outbreaks have been reported in the country. Here, we characterized eleven NDV isolated from apparently healthy wild birds and backyard chickens in three different locations of Jalisco, Mexico in 2017. Total RNA from NDV was reverse-transcribed, and 1285 nucleotides, which includes 3/4 of the fusion gene, was amplified and sequenced using a long-read MinION sequencing method. The sequences were 99.99-100% identical to the corresponding region obtained using the Illumina MiSeq. Phylogenetic analysis using MinION sequences demonstrated that nine virulent NDV from wild birds belonged to sub-genotypes Vc and VIn, and two backyard chicken isolates were of sub-genotype Vc. The sub-genotype Vc viruses had nucleotide sequence identity that ranged from 97.7 to 98% to a virus of the same sub-genotype isolated from a chicken in Mexico in 2010. Three viruses from pigeons had 96.3-98.7% nucleotide identity to sub-genotype VIn pigeon viruses, commonly referred to as pigeon paramyxovirus, isolated in the USA during 2000-2016. This study demonstrates that viruses of sub-genotype Vc are still present in Mexico, and the detection of this sub-genotype in both chickens and wild birds suggests that transmission among these species may represent a biosecurity risk. This is the first detection and complete genome sequencing of genotype VI NDV from Mexico. In addition, the utilization of an optimized long-read sequencing method for rapid virulence and genotype identification using the Oxford nanopore MinION system is demonstrated.

Occurrence of infectious bronchitis in layer birds in Plateau state, north central Nigeria

A flock of 54 wk-old layer birds exhibiting signs of respiratory distress, greenish diarrhea, and drop in egg production was investigated. A marked drop in egg production (55%) was recorded with eggs appearing white and soft-shelled. Mortality was in the range of 1%–2% with post-mortem lesions revealing cloudy air sacs, frothy, and congested lungs. Viral RNA was extracted from pooled tissue samples (trachea, lungs, spleen, and liver) and tested for Avian influenza virus (AIV), Newcastle disease virus (NDV), and infectious bronchitis virus (IBV) by reverse transcriptase-polymerase chain reaction (RT-PCR). In addition, virus isolation was attempted in 9–11 day-old embryonating chicken eggs (ECE). In order to determine the prevalence of IBV serotype(s) in the flock, serum samples were screened by hemagglutination-inhibition (HI) test using IBV antigens and antisera (Arkansas, Connecticut, and Massachusetts). Neither AIV nor NDV but IBV was detected in the tissue samples by RT-PCR. In addition, virus isolate obtained after four serial passages in ECE produced dwarfed, stunted, and hemorrhagic embryos, and the isolate was confirmed by RT-PCR to be IBV. The serum samples were 100% seropositive for three serotypes with HI titres ranging from 5 to 12 Log². In this study, IBV was confirmed as the causative agent of the observed respiratory distress and drop in egg production. Also, the evidence of co-circulation of multiple IBV serotypes was established, this to the best of our knowledge is the first of such report in Nigeria. We recommend extensive molecular and sero-epidemiology of circulating IBV genotypes and serotypes in Nigeria with the aim of developing better control strategies, including vaccination.

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

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

Innocuity and anti-Newcastle-virus-activity of Cladosiphon okamuranus fucoidan in chicken embryos

This study evaluated the potential toxicity and antiviral activity of fucoidan from Cladosiphon okamuranus against Newcastle disease virus (NDV), one of the most serious threats to the poultry industry in the world. Toxicity was assayed on chicken embryo fibroblast (CEF) secondary cultures at concentrations ranging from 0.1 to 1500 μg per mL culture medium, assessing the cell viability by the yellow tetrazolium MTT (3-(4, 5-dimethylthiazolyl-2)-2, 5-diphenyltetrazolium bromide) assay, and on 9-day-old embryonated chicken eggs by inoculation of 2 to 500 μg doses in the allantoic cavity, assessing the embryos morphology and liver histology. At 48 h post-inoculation, viability of CEF exposed to concentrations up to 10 μg/mL was not significantly affected, and the 50% cytotoxic concentration was estimated as of 1062 μg/mL; after exposure in ovo, some chick embryos showed liver steatosis when treated with fucoidan doses over 20 μg per egg (15 to 28% at 200 μg, 27 to 56% at 500 μg), but no change was detected in their size or aspect. Antiviral activity was tested by treating 9-day-old embryos via the allantoic route with 0.25 to 16 μg fucoidan doses that were applied at different times (-1, 0 and +1 h) relative to the inoculation of 10,000 folds the 50% Tissue Culture Infective Dose (TCID50) of the NDV, La Sota strain. At 72 h post infection, virus titration in the allantoic fluid by hemagglutination assay (HA) showed a considerable and significant inhibition of infectivity for all doses, the best result (a 90% decrease) being obtained in embryos treated with 1 μg fucoidan one hour before infection. Viral RNA semi-quantification in pooled liver and small intestine of embryos that had been treated with 4 and 16 μg fucoidan 1 h before the infection showed reductions of the virus replication by 60 and 99.8%, respectively. Since this high anti-NDV activity in ovo was obtained with quite innocuous doses, fucoidan from C. okamuranus could be a potential low-toxicity antiviral compound to be used in areas exposed to NDV.

Characterization of Avian Influenza and Newcastle Disease Viruses from Poultry in Libya

On March 2013, the Libyan poultry industry faced severe outbreaks due to mixed infections of APMV-1 (Newcastle disease) and low pathogenic avian influenza (AI) of the H9N2 subtype which were causing high mortality and great economic losses. APMV-1 and H9N2 were isolated and characterized. Genetic sequencing of the APMV-1/chicken/Libya/13VIR/ 7225-1/2013 isolate revealed the presence of a velogenic APMV-1 belonging to lineage 5 (GRRRQKR*F Lin.5) or genotype VII in class II, according to the nomenclature in use. Three AI viruses of the H9N2 subtype, namely A/avian/Libya/13VIR7225-2/2013, A/avian/Libya/13VIR7225-3/2013, and A/avian/Libya/13VIR7225-5/2013, were isolated and found to belong to the G1 lineage. Analysis of amino acid sequences showed that the analyzed H9N2 viruses contained the amino acid Leu at position 226 (H3 numbering) at the receptor binding site of the HA, responsible for human virus-like receptor specificity. On March 2014, an outbreak of highly pathogenic avian influenza (HPAI) virus of the H5N1 subtype was diagnosed in a backyard poultry farm in an eastern region of Libya. The H5N1 isolate (A/chicken/Libya/14VIR2749-16/2014) was detected by real time RT-PCR (rRT-PCR). Genetic characterization of the HA gene revealed that the identified subtype was highly pathogenic, belonged to the 2.2.1 lineage, and clustered with recent Egyptian viruses. This study revealed the presence of a velogenic APMV-1 genotype and of two influenza subtypes, namely HPAI H5N1 and H9N2, which are of major interest for public and animal health. Considering these findings, more investigations must be undertaken to establish and implement adequate influenza surveillance programs; this would allow better study of the epidemiology of APMV-1 genotype VII in Libya and evaluation of the current vaccination strategies.

Molecular detection of infectious bronchitis and Newcastle disease viruses in broiler chickens with respiratory signs using Duplex RT-PCR

Infectious bronchitis (IB) and Newcastle disease (ND) are highly contagious and the most economically important diseases of the poultry affecting respiratory tract and causing economic losses in poultry industry throughout the world. In the present study, the simultaneous detection and differentiation of causative agents of these diseases were investigated using duplex-RT-PCR. RNA was extracted from vaccinal and reference strains of infectious bronchitis virus (IBV) and Newcastle disease virus (NDV) and then cDNA was synthesized. Using two universal primer sets for detection of IBV and NDV, the duplex-RT-PCR was developed. In order to assess the efficiency of the developed duplex RT-PCR, a number of 12 broiler farms with the symptoms of respiratory tract infection was sampled (trachea, lung and kidney were sampled from affected birds suspicious for IBV and NDV infections). After RNA extraction from tissues and cDNA synthesis, the presence of IBV and NDV genome were investigated using duplex-PCR. The results showed that three of twelve examined broiler farms were positive for IBV and two farms were positive for NDV and IBV. The results revealed that the duplex-RT-PCR is a quick and sensitive procedure for simultaneously detecting IBV and NDV in birds with respiratory infections.

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

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

Molecular characterization of chicken-derived genotype VIId Newcastle disease virus isolates in China during 2005-2012 reveals a new length in hemagglutinin-neuraminidase

Newcastle disease (ND) is one of the most important diseases of poultry, and causes severe economic losses in the global poultry industry. Although all Newcastle disease virus (NDV) isolates belong to a single serotype, significant genetic diversity has been described between different NDV isolates. Here, we report the molecular characterization of 23 virulent genotype VIId NDV isolates of class II circulating in China. Phylogenetic construction and analysis revealed the existence of distinctly genomic and amino acid differences that clearly distinguished these isolates from other typical NDV genotypes and vaccine strains. We also report a new 582-amino-acid hemagglutinin-neuraminidase in genotype VII NDV strains. This is believed to be the first study to investigate systematically the most predominant NDV strains, and provides more information on the genetic nature of genotype VIId NDV of class II circulating in China.

Altered pro-inflammatory cytokine mRNA levels in chickens infected with infectious bronchitis virus

Infectious bronchitis virus (IBV) replicates primarily in the respiratory tract and grows in various organs in chickens, with or without pathological effects. The diversity of this virus has been verified by sequence analysis of the S1 glycoprotein gene, but this method must be supplemented with further analysis for characterization of the agent. To increase our understanding of the pathogenesis of the disease caused by this virus, we investigated the response of chickens to 2 IBV with different genotypes, KIIa and ChVI. The clinical signs induced by the viruses were observed. In addition, the mRNA levels of the pro-inflammatory cytokines, IL-6, IL-1β, and lipopolysaccharide-induced tumor necrosis factor-α factor and the serum levels of α₁-acid glycoprotein, which is a major acute phase protein, were measured. The KIIa genotype (Kr/ADL110002/2011) induced clinical signs accompanied by the excessive production of pro-inflammatory cytokines and a higher viral load. In chickens infected with this isolate, simultaneous peaks in the viral copy number and cytokine production were observed at 7 dpi in the trachea and 9 d postinoculation in the kidney. On the other hand, the chickens infected with the ChVI genotype (Kr/ADL120003/2012) did not show a response other than a mild upregulation of cytokines at 1 d postinoculation, which appears to indicate the invasion of the virus. In summary, we confirmed a differential innate response following infection with distinct IBV. We hypothesize that an excessive innate response contributes to the scale of the pathophysiologic effect in chickens.

Genome-wide association study of antibody response to Newcastle disease virus in chicken

Background

Since the first outbreak in Indonesia in 1926, Newcastle disease has become one of the most common and contagious bird diseases throughout the world. To date, enhancing host antibody response by vaccination remains the most efficient strategy to control outbreaks of Newcastle disease. Antibody response plays an important role in host resistance to Newcastle disease, and selection for antibody response can effectively improve disease resistance in chickens. However, the molecular basis of the variation in antibody response to Newcastle disease virus (NDV) is not clear. The aim of this study was to detect genes modulating antibody response to NDV by a genome-wide association study (GWAS) in chickens.

Results

To identify genes or chromosomal regions associated with antibody response to NDV after immunization, a GWAS was performed using 39,833 SNP markers in a chicken F₂ resource population derived from a cross between two broiler lines that differed in their resistance. Two SNP effects reached 5% Bonferroni genome-wide significance (P<1.26×10^-6). These two SNPs, rs15354805 and rs15355555, were both on chicken (Gallus gallus) chromosome 1 and spanned approximately 600 Kb, from 100.4 Mb to 101.0 Mb. Rs15354805 is in intron 7 of the chicken Roundabout, axon guidance receptor, homolog 2 (ROBO2) gene, and rs15355555 is located about 243 Kb upstream of ROBO2. Rs15354805 explained 5% of the phenotypic variation in antibody response to NDV, post immunization, in chickens. Rs15355555 had a similar effect as rs15354805 because of its linkage disequilibrium with rs15354805 (r²=0.98).

Conclusion

The region at about 100 Mb from the proximal end of chicken chromosome 1, including the ROBO1 and ROBO2 genes, has a strong effect on the antibody response to the NDV in chickens. This study paves the way for further research on the host immune response to NDV.

In vitro characterization of the antiviral activity of fucoidan from Cladosiphon okamuranus against Newcastle Disease Virus

BACKGROUND

Newcastle Disease Virus (NDV) causes a serious infectious disease in birds that results in severe losses in the worldwide poultry industry. Despite vaccination, NDV outbreaks have increased the necessity of alternative prevention and control measures. Several recent studies focused on antiviral compounds obtained from natural resources. Many extracts from marine organisms have been isolated and tested for pharmacological purposes, and their antiviral activity has been demonstrated in vitro and in vivo. Fucoidan is a sulfated polysaccharide present in the cell wall matrix of brown algae that has been demonstrated to inhibit certain enveloped viruses with low toxicity. This study evaluated the potential antiviral activity and the mechanism of action of fucoidan from Cladosiphon okamuranus against NDV in the Vero cell line.

METHODS

The cytotoxicity of fucoidan was determined by the MTT assay. To study its antiviral activity, fusion and plaque-forming unit (PFU) inhibition assays were conducted. The mechanism of action was determined by time of addition, fusion inhibition, and penetration assays. The NDV vaccine strain (La Sota) was used in the fusion inhibition assays. PFU and Western blot experiments were performed using a wild-type lentogenic NDV strain.

RESULTS

Fucoidan exhibited antiviral activity against NDV La Sota, with an obtained IS50 >2000. In time of addition studies, we observed viral inhibition in the early stages of infection (0-60 min post-infection). The inhibition of viral penetration experiments with a wild-type NDV strain supported this result, as these experiments demonstrated a 48% decrease in viral infection as well as reduced HN protein expression. Ribavirin, which was used as an antiviral control, exhibited lower antiviral activity than fucoidan and high toxicity at active doses. In the fusion assays, the number of syncytia was significantly reduced (70% inhibition) when fucoidan was added before cleavage of the fusion protein, perhaps indicating a specific interaction between fucoidan and the F0 protein.

CONCLUSION

The results of this study suggest that fucoidan from C. okamuranus represents a potential low-toxicity antiviral compound for the poultry industry, and our findings provide a better understanding of the mode of action of sulfated polysaccharides.

Biological and phylogenetic characterization of a genotype VII Newcastle disease virus from Venezuela: efficacy of field vaccination

Here we report the biological and molecular characterization of a virulent genotype VII Newcastle disease virus (NDV) circulating in Venezuela and the assessment of the vaccination efficacy under field conditions compared to controlled rearing conditions. Biological pathotyping showed a mean embryo dead time of 50 h and an intracerebral pathogenicity index of 1.86. Sequence-based phylogenetic analysis demonstrated that the virus belongs to genotype VII in class II (a genotype often found in Asia and Africa), representing the first report of the presence of this genotype in the continent of South America. A vaccine-challenge trial in commercial broilers reared in fields or in a experimental setting included dual (live/killed) priming of 1-day-old chicks plus two live NDV and infectious bursal disease virus (IBDV) field vaccinations at days 7 and 17, followed by a very stringent genotype VII NDV challenge at day 28. Serology for NDV and IBDV, bursal integrity, and protection against NDV lethal challenge were assessed. At 28 days, field vaccinates showed significantly lower NDV (1,356 versus 2,384) and higher IBD (7,295 versus 1,489) enzyme-linked immunosorbent assay (ELISA) antibody titers than the experimentally reared birds. A lower bursal size and bursa-body weight ratio (P < 0.05) and higher bursa lesion score were also detected in the field set. Only 57.1% of field vaccinates survived the lethal challenge, differing (P < 0.05) from 90.5% survival in the experimental farm. Overall, results confirmed the presence of the genotype VII viruses in South America and suggest that field-associated factors such as immunosuppression compromise the efficacy of the vaccination protocols implemented.

Concomitant turkey herpesvirus-infectious bursal disease vector vaccine and oil-adjuvanted inactivated Newcastle disease vaccine administration: consequences for vaccine intake and protection

Hatchery vaccination protocols in day-old chicks are designed to provide early priming and protection against several poultry diseases including, but not limited to, Marek's disease (MD), infectious bursal disease (IBD), and Newcastle disease (ND). The constraint of concomitant administration of live MD and IBD vaccines plus ND inactivated oil-adjuvanted vaccines (IOAVs) requires improvements in vaccine technology. Single-needle concomitant subcutaneous (SC) application of IBD/MDV and killed NDV vaccine and the use of viral vectors for expression of immunogenic proteins are a current trend in the industry. The objective of this work was to assess the compatibility of a turkey herpesvirus (HVT)-infectious bursal disease (vHVT-IBD) vector vaccine applied simultaneously with IOAV and to evaluate the consequences for vaccine intake, the need for additional immunizations with the respective vaccines, and protection. Five separate trials were performed using double- and/or single-needle injectors. The levels and persistence of vaccine intake, serologic response, vHVT-IBD virus combination with the MD Rispens strain, and/or live NDV vaccination were also assessed. Histopathology and PCR at injection sites showed adequate vaccine intake detected up to 44 days postvaccination. Serologic evidence of vaccine priming was observed, and all vaccinated groups differed (P < 0.05) from the control at different time points. MD, NDV, and IBD protection results after concomitant double-shot single-needle vaccination were near 85%, 95%, and 100%, respectively. Taken together the results indicate no deleterious effects on the efficacy of the vHVT-IBD vaccine monitored by vaccine intake, serologic and challenge results, and combinations after concomitant live/killed vaccination, suggesting the suitability of its use in hatchery vaccination. All types of injectors used as well as injection techniques, vaccines injected separately or together, gave the same results.

Recombinational histories of avian infectious bronchitis virus and turkey coronavirus

Phylogenetic analysis of complete genomes of the avian coronaviruses avian infectious bronchitis (AIBV) and turkey coronavirus (TCoV) supported the hypothesis that numerous recombination events have occurred between these viruses. Although the two groups of viruses differed markedly in the sequence of the spike protein, the gene (S) encoding this protein showed no evidence of positive selection or of an elevated mutation rate. Rather, the data suggested that recombination events have homogenized the portions of the genome other than the S gene between the two groups of viruses, while continuing to maintain the two distinct, anciently diverged versions of the S gene. The latter hypothesis was supported by a phylogeny of S proteins from representative coronaviruses, in which S proteins of AIBV and TCoV fell in the same clade.

Biological and phylogenetic characterization of virulent Newcastle disease virus circulating in Mexico

In 2002-2003, velogenic Newcastle Disease Virus outbreaks, closely related to the Mexican isolates, were confirmed in the United States (U.S.) in southern California, Arizona, Nevada, and Texas. In this report, virulent NDVs isolated in Mexico between 1998 and 2006 were subjected to biologic characterization, using standard pathogenicity tests, and to phylogenetic analysis. Chicken embryo mean death time (MDT) test results ranged from 39.7 to 61.5 hours, and intracerebral pathogenicity index (ICPI) values were between 1.59 and 1.94, compared to a possible maximum value of 2.0. These isolates showed a dibasic amino acid motif at the fusion protein cleavage site sequence required for host systemic replication. Phylogenetic analysis indicated that the Mexican virulent NDVs belong to the class II, genotype V viruses and can be clearly divided in two groups as follows: isolates from 1998 to 2001 with close epidemiologic relationship with the latest U.S. NDV outbreaks, and phylogenetically distinct viruses, isolated from 2004 to 2006, which showed higher virulence. The assessment of the evolution of viruses from Mexico and other neighboring countries will aid in the U.S surveillance efforts for early detection of highly virulent NDV.

Genomic comparison of the complete coding and intergenic regions of the VG/GA Newcastle disease virus and its respirotropic clone 5

The complete genome of the Villegas-Glisson/University of Georgia (VG/GA) strain of Newcastle disease virus (NDV) and that of a plaque purified clone (clone 5) exhibiting a respiratory phenotype were sequenced and analyzed. The VG/GA strain, isolated from the intestine of healthy turkeys, replicates in the respiratory and intestinal tract of chickens. It is used worldwide as a vaccine strain and its tissue tropism is extremely important for protection against velogenic viscerotropic NDV which targets both intestinal and respiratory epithelia, inducing severe gross and microscopic damage. The clone 5, a plaque purified clone from the VG/GA strain, cannot be recovered from the intestine of infected birds, suggesting a respirotropic nature. A modified primer sequence-independent amplification method was used to sequence the complete coding regions of both viruses and to assess phylogenetic relationships and genomic basis for phenotype differences. The phylogenetic analysis grouped the VG/GA strain and the clone 5 within class II, genotype II viruses and showed that they are greater than 99.9% identical with only 5 nucleotides differences. Both are closely related to classic vaccine strains, such as LaSota and B1. Only 3 amino acid differences at the fusion protein differentiated the VG/GA strain from the clone 5. These differences may explain the differential phenotype observed in the VG/GA strain and are discussed.

Comparative histopathology of two serotypes of infectious bronchitis virus (T and n1/88) in laying hens and cockerels

The comparative and sequential histopathology of different tissues of unvaccinated laying hens and cockerels were studied in chickens exposed to T and N1/88 strain of infectious bronchitis virus (IBV). The Harderian gland and trachea of hens and cockerels in both T- and N1/88-infected groups were damaged to a similar extent. The cecum was unaffected for both strains of IBV in both hens and cockerels. The sequential histopathological changes in hens revealed that IBV multiplies initially in the Harderian gland, then in the tracheal mucosa and simultaneously in the kidney and regions of the oviduct such as the magnum, tubular shell gland, and shell gland pouch. In cockerels, IBV multiplies first in the Harderian gland, then simultaneously in the trachea and kidney. Overall, the severity and persistence of lesions were greater in the kidneys of T-infected hens as compared with N1/88-infected hens. However, pathological changes in the kidney were mild in T- and N1/88-infected cockerels.

Use of FTA filter paper for the molecular detection of Newcastle disease virus

The feasibility of using Flinders Technology Associates filter papers (FTA cards) to collect allantoic fluid and chicken tissue samples for Newcastle disease virus (NDV) molecular detection was evaluated. Trizol RNA extraction and one-step reverse transcriptase-polymerase chain reaction (RT-PCR) were used. FTA cards allowed NDV identification from allantoic fluid with a titre of 10(5.8) median embryo lethal doses/ml. The inactivated virus remained stable on the cards for 15 days. NDV was detected from FTA imprints of the trachea, lung, caecal tonsil and cloacal faeces of experimentally infected birds. RT-PCR detection from FTA cards was confirmed by homologous frozen-tissue RT-PCR and virus isolation. Direct nucleotide sequence of the amplified F gene allowed prediction of NDV virulence. No virus isolation was possible from the FTA inactivated samples, indicating viral inactivation upon contact. The FTA cards are suitable for collecting and transporting NDV-positive samples, providing a reliable source of RNA for molecular characterization and a hazard-free sample.

Oral immunoadjuvant activity of Lactobacillus casei subsp. casei in dextran-fed layer chickens

We recently reported that synbiotic Lactobacillus casei subsp. casei together with specific substrate dextran elicited an enhancement in humoral immune response against bovine serum albumin (BSA) as a model antigen in BALB/c mice. The present study was designed to evaluate the oral immunoadjuvant effects of the synbiotic in layer chickens. Using a PCR assay, L. casei subsp. casei was detected specifically in the intestinal chyme of chickens (10 d of age, Julia strain) fed ad libitum on a diet supplemented with 75 mg dextran/kg (dextran-supplemented diet, DSD) and administered orally with 10(7) colony-forming units (CFU) L. casei subsp. casei in 0.1 ml PBS with the aid of an intubation needle at 1, 2 and 3 d of age. Furthermore, oral administration of 10(7) CFU L. casei subsp. casei at 1-3 d of age significantly enhanced the production of anti-BSA antibody in DSD-fed chickens (60 d of age) administered orally with 1 mg BSA at 32 and 33 d of age and subcutaneously with 5 microg BSA at 33 d of age. In addition, among bacterial numbers tested, 10(6) CFU L. casei subsp. casei together with dextran induced an effective increase in humoral immune response to mixed inactivated vaccines against Newcastle disease and avian infectious bronchitis, and the treatment may be advantageous in protecting against these infectious diseases in chickens in actual application. These results suggest that dietary supplementation of L. casei subsp. casei with dextran leads to immunomodulation of humoral immune responses.

The avian lung-associated immune system: a review

The lung is a major target organ for numerous viral and bacterial diseases of poultry. To control this constant threat birds have developed a highly organized lung-associated immune system. In this review the basic features of this system are described and their functional properties discussed. Most prominent in the avian lung is the bronchus-associated lymphoid tissue (BALT) which is located at the junctions between the primary bronchus and the caudal secondary bronchi. BALT nodules are absent in newly hatched birds, but gradually developed into the mature structures found from 6-8 weeks onwards. They are organized into distinct B and T cell areas, frequently comprise germinal centres and are covered by a characteristic follicle-associated epithelium. The interstitial tissue of the parabronchial walls harbours large numbers of tissue macrophages and lymphocytes which are scattered throughout tissue. A striking feature of the avian lung is the low number of macrophages on the respiratory surface under non-inflammatory conditions. Stimulation of the lung by live bacteria but not by a variety of bacterial products elicits a significant efflux of activated macrophages and, depending on the pathogen, of heterophils. In addition to the cellular components humoral defence mechanisms are found on the lung surface including secretory IgA. The compartmentalisation of the immune system in the avian lung into BALT and non BALT-regions should be taken into account in studies on the host-pathogen interaction since these structures may have distinct functional properties during an immune response.

Influenza Aviária: Uma Revisão dos Últimos Dez Anos

A influenza aviária é doença exótica no Brasil. O sistema de vigilância implementado pelo Programa Nacional de Sanidade Avícola (PNSA) mantém monitoração permanente das aves das principais espécies domésticas, tanto do material genético importado para a indústria avícola, por exemplo, da espécie das galinhas (Gallus gallus formadomestica), perus (Meleagris gallopavo formadomestica), codornas (Coturnix coturnix japonica), patos (Anas), primários (elite), bisavós e avós para postura ou corte, como aves de espécies de exploração mais recente, exóticas, por exemplo avestruzes (Struthio camelus) ou nativas, por exemplo emas (Rhea americana). Os plantéis de reprodutores em produção são também acompanhados por amostragens periódicas, conforme previsto no PNSA, além da monitoração das respostas aos programas de vacinação, por exemplo, contra bronquite infecciosa e doença infecciosa bursal. O PNSA estabelece as normas de atuação para o controle e erradicação da doença de Newcastle (ND) e Influenza Aviária (AI) (Projeto de Vigilância, 2001), a saber: I - Notificação de focos da doença (e confirmação laboratorial no LARA-Campinas); II - Assistência a focos; III - Medidas de desinfecção; IV - Sacrifício sanitário; V - Vazio sanitário; VI - Vacinação dos plantéis ou esquemas emergenciais; VII - Controle e fiscalização dos animais susceptíveis; VIII - Outras medidas sanitárias; A vigilância e atenção ao foco exige o diagnóstico laboratorial e diferencial de AI e ND, que segue as normas do PNSA, conforme o sumário abaixo: 1- Interdição e coleta de materiais para exame laboratorial oficial; 2- Registro das aves: espécie(s), categoria(s), número(s), manutenção de aves; utensílios e produtos no local; proibição de trânsito de e para a(s) propriedade(s) em um raio de 10 km; controle de todos os animais e materiais possíveis fontes de propagação; desinfecção de vias de entradas e saídas à(s) propriedade(s); inquérito epidemiológico. 3- Confirmação laboratorial: isolamento de agente letal hemaglutinante em ovos embrionados de galinhas SPF, não inibido (inibição da hemaglutinação) ou não neutralizado (soroneutralização) por soro específico para o vírus da doença de Newcastle; caracterização do agente como vírus da influenza aviária (AIV) por detecção de antígenos da nucleoproteína e/ou matriciais de AIV e de seu subtipo por ensaios específicos para a caracterização da hemaglutinina e neuraminidase (imunodifusão, imunoenzimáticos ou moleculares). 4- Abate e destruição imediata (cremação) de todas as aves, resíduos, carnes e ovos da(s) propriedade(s) atingida(s) e vizinhas (raio de 3 km); limpeza e desinfecção das instalações; vazio sanitário (mínimo 21 dias); 5- Permitir o transporte para o abate ou incubação dentro da zona de vigilância (raio de 10 km). 6- Proibir feiras, exposições, mercados na zona de vigilância (10 km). 7- Aplicar estas medidas por mínimo de 21 dias após a destruição das fontes de propagação e desinfecção das instalações, proibir a retirada de aves e produtos na zona de proteção (3 km) por 21 dias e 15 dias na zona de vigilância (10 km). A certificação de área livre segue as normas da OIE e PNSA, considerando AI exótica no Brasil (país livre), e exige: 1- AI de alta patogenicidade não diagnosticada pelo sistema de vigilância pelos últimos 3 anos; 2- Um período de 6 meses após o abate, destruição das aves e resíduos e desinfecção após surto; O sistema de criação da avicultura predominante no Brasil (galinhas e perus) emprega a mais atual tecnologia e conhecimento científico na produção, no qual os plantéis são gerenciados com biossegurança, avaliação permanente dos pontos críticos, sistema de qualidade total e programas de vacinações que garantem a prevenção de inúmeros problemas sanitários. A prevenção de influenza aviária é especialmente favorecida por essas características. O sistema e tipo de construção (galpões) para o alojamento dos plantéis dessas espécies dificultam também o desafio eventualmente imposto pelas aves de vida livre. A localização geográfica da avicultura nacional, localizada fora das rotas migratórias das aves-reservatório, pode também exercer papel importante na ausência de focos de influenza no Brasil. Além disso, o baixo índice de replicação dos AIV nas aves migratórias durante a estada na região subtropical também influi para a menor ocorrência. As espécies de aves domésticas de importância comercial mais sensíveis à infecção e potencialmente envolvidas no papel de fonte de infecção, conforme citadas na literatura internacional, perus e patos, são mantidas em galpões industriais com sistema de biossegurança e de distribuição geográfica bastante restrita, em contraste com as criações dos países com relatos permanentes de surtos, em que se associam as condições de desafio naturais geográficas ditadas pelas rotas migratórias, mais alta replicação na ave na estação (países temperados) e a criação em campo aberto.

Nonspecific cellular defense of the avian respiratory system: a review

The normal, steady-state, avian respiratory system has very low numbers of residing avian respiratory phagocytes (ARP). Birds must rely heavily on the influx of ARP to defend against infectious agents. The system is refractory to elicitation by inert stimulants, but responds efficiently to replicating bacteria, with very rapid influx of large numbers of activated ARP (polymorphonuclear neutrophils, heterophils, and macrophages) with increased phagocytic proportions and capacities. The numbers subside within a few a days. Activated ARP act in a non agent-specific manner: Pasteurella multocida-activated ARP can defend against a severe Escherichia coli airsacculitis. Parenteral routes of stimulation generally are not, respiratory routes are very, efficient in activating ARP. Heterophils are the most efficient in defensive reactions, such as oxidative burst, production of nitric oxide and killing of bacteria. Respiratory viruses may stimulate, but also may diminish some of the defensive functions of ARP. This is also true for attenuated, modified live virus vaccines. These vaccines must be used carefully in the presence of subclinical bacterial, mycoplasmal infections. Published literature on non-specific cellular defense of the avian respiratory system is very limited, particularly about interactions among multiple infectious agents and the system.