Efficacy, immunogenicity, and virus shedding in broiler chickens inoculated with live attenuated fowl adenovirus serotype 8b propagated a bioreactor

Background

Fowl adenovirus (FAdV) 8b causes huge economic losses in the poultry industry worldwide. Attenuated FAdV 8b could be useful in preventing FAdV infections globally and scale-up obstacles could be solved by bioreactor technology.

Aim

This study was carried out to attenuate the FAdV 8b isolate, propagate it in a bioreactor, molecularly characterize the passage isolates, and determine the immunogenicity, efficacy, and shedding of the virus of chickens.

Methods

FAdV serotype 8b (UPM11142) isolate was passaged on chicken embryo liver (CEL) cells until attenuation and propagated in a bioreactor (UPM11142P20B1). Hexon and fiber genes of the isolates were sequenced and analyzed. UPM11142P20B1 was administered to 116-day-old broiler chickens divided into four groups, A (control), B (non-booster), C (booster with UPM11142P20B1), and D (booster with inactivated UPM11142P5B1). Eight chickens from each group were challenged. Body weight (BW) and liver weight (LW), liver: BW ratio (LBR), FAdV antibody titer, T lymphocyte sub-populations in the liver, spleen and thymus; and challenge virus load in the liver and shedding in cloaca were measured at weekly intervals.

Results

The isolate caused typical cytopathic effects on CEL cells typical of FAdV. Novel molecular changes in the genes occurred which could be markers for FAdV 8b attenuation. BW, LW, and LBR were similar among groups throughout the trial but the uninoculated control-challenged group (UCC) had significantly higher LBR than the inoculated and challenged groups at 35 dpi. Non-booster group had higher FAdV antibodies at all time points than the uninoculated control group (UCG); and the challenged booster groups had higher titer at 35 dpi than UCC. T lymphocytes increased at different time-points in the liver of inoculated chickens, and in the spleen and thymus as well, and was higher in the organs of inoculated challenged groups than the UCC. There was a significantly higher challenge virus load in the liver and cloaca of UCC chickens than in the non-booster chickens.

Conclusion

UPM11142P20B1 was safe, efficacious, significantly reduced shedding, and is recommended as a candidate vaccine in the prevention and control of FAdV 8b infections in broiler chickens.

TaqMan probe-based qPCR method for specific detection and quantification of Fowl adenovirus 8b challenge from chickens inoculated with live attenuated or inactivated virus

Background: Fowl adenovirus (FAdV) 8b and other serotypes cause inclusion body hepatitis (IBH) in chickens. Specific detection of aetiologic serotype in mixed infection and vaccine failure could be difficult. Aim: The objective of this study was to develop a TaqMan probe-based qPCR method for the detection and quantification of the FAdV 8b challenge virus. Methods: Forty-eight broiler chickens inoculated with live attenuated or inactivated FAdV 8b strains at day 1 of age either with or without booster at day 14 post-inoculation were used. The chickens were challenged with a pathogenic strain of FAdV 8b at day 28 of age. Liver and cloacal swabs were collected on days 7 and 14 post-challenge. Primers and probe were designed, specificity confirmed, and used to carry out qPCR amplification. Results: The assay amplified the FAdV DNA challenge virus, but not that of the live attenuated virus. It could detect FAdV 8b DNA as low as 0.001ng/µl in liver and cloacal swab samples. Copy numbers obtained indicate virus load and shedding. Conclusions: It shows that a selective detection of FAdV 8b within serotype is possible. It can be useful for rapid detection and diagnosis of the disease, virus quantification and differentiation within species, determination of vaccination failure and efficacy especially the virus load in the target organ and shedding.

Efficacy, humoral, and cell-mediated immune response of inactivated fowl adenovirus 8b propagated in chicken embryo liver cells using bioreactor in broiler chickens

Background and Aim

Fowl adenovirus (FAdV) 8b causes inclusion body hepatitis, resulting in major economic losses globally among chickens. The objectives were to inactivate FAdV 8b isolate propagated in chicken embryo liver (CEL) cells using a stirred tank bioreactor (UPM08136P5B1) and determine the humoral and cell-mediated immune response, efficacy, and virus shedding in broiler chickens.

Materials and Methods

The FAdV 8b isolate UPM08136P5B1 was inactivated using binary ethyleneimine, adjuvanted with Montanide 71VG, inoculated into day-old broiler chickens in a booster group (BG) and non-booster group (NBG), and challenged with a pathogenic FAdV 8b strain. Clinical signs, gross lesions, body weight (BW), liver: body weight ratio, FAdV antibody titer using enzyme-linked immunosorbent assay, and histopathological changes were recorded. The CD3+, CD4+, and CD8+ T-lymphocyte profiles of the liver, spleen, and thymus using flow cytometry, and viral load in liver and cloacal shedding using quantitative polymerase chain reaction were evaluated.

Results

Chickens in the challenged control group (CCG) exhibited mild clinical signs, gross lesions, and histopathological changes, which were absent in the inoculated groups, and had lower BW and higher liver BW ratio than chickens in the unchallenged control group (UCG); BG and NBG on 35- and 42-days post-inoculation (DPI). Chickens in NBG and BG had higher antibodies than UCG on 7, 21, 35, and 42 DPI. The challenged BG and NBG produced higher antibodies than the CCG on 35 DPI. T-lymphocytes were higher among the inoculated groups than UCG in the liver, spleen, and thymus. Inoculated challenged groups recorded higher CD3+, CD4+, and CD8+ T-lymphocytes on 35 and 42 DPI than CCG. The challenged control group had a significantly higher viral load in the liver than challenged that in BG on 35 DPI and BG and NBG on 42 DPI. The challenged control group had significantly higher challenge FAdV shedding than challenged inoculated groups on 35 and NBG on 42 DPI.

Conclusion

UPM08136P5B1 was successfully inactivated and mixed with Montanide 71VG. The inactivated vaccine candidate that induced humoral and cellular immunity was effective, reduced FAdV load in the liver, and shedding in the cloaca, and could be useful against FAdV 8b infections in chickens.

Expression Profiles of Immune-Related Genes and Apoptosis Study of Avian Intraepithelial-Natural Killer Cells in Chickens Inoculated with Vaccine Strain of Newcastle Disease Virus (NDV) and Challenged with Virulent NDV

In spite of the available information on the role of natural killer (NK) cells in several viral infections, the interactions between chicken intraepithelial-NK (IEL-NK) cells and Newcastle disease virus (NDV) are poorly understood. In this study, we investigated these interactions following the inoculation of chickens with NDV vaccine strain LaSota and subsequent challenge with velogenic NDV (vNDV) genotype VII (GVII) and VIII (GVIII), through quantification of IEL-NK cell's apoptosis and expression profiling of its surface receptors. Specific-pathogen-free chickens were randomly divided into six groups, as follows: one group of an uninfected control, one group infected with NDV LaSota, two groups each infected with either GVII or GVIII, and two groups inoculated with NDV LaSota and challenged with either GVII (LaSota-genotype VII [LSGVII]) or GVIII (LaSota-genotype VIII [LSGVIII]). Avian intraepithelial lymphocytes (IEL) were isolated from the duodenal loops, and CD3- cells were characterized. Immunophenotyping and apoptosis analysis of CD3-/CD25+/CD45+IEL NK cells were conducted using a flow cytometer. In addition, a gene expression study was conducted using real-time quantitative PCR. Data were analyzed using two-way analysis of variance. The results showed that vNDV GVII or GVIII caused apoptosis of IEL-NK cells; however, following inoculation of LSGVII or LSGVIII, the effect of vNDV GVII and GVIII to cause a reduction in the population of viable IEL-NK cells was significantly reduced. Furthermore, the expression profiles of activating receptors CD69, NK-lysin, and IFN-γ, were generally upregulated in chickens inoculated with LSGVII or LSGVIII. In contrast, B-NK, an inhibitory receptor, was downregulated in these treatment groups. In NDV GVII- and GVIII-challenged groups, however, B-NK was upregulated, whereas the other receptors were generally downregulated. The findings of this study showed that NDV vaccine strain LaSota may prevent apoptosis and cause upregulation of activating receptors of chicken IEL-NK cells in velogenic virus-challenged settings.

Alteration in the Population of Intraepithelial Lymphocytes and Virus Shedding in Specific-Pathogen-Free Chickens Following Inoculation with Lentogenic and Velogenic Newcastle Disease Virus Strains

Intraepithelial lymphocytes (IELs) provide the first line of immunological defense after the invasion of the intestine by a pathogen. To understand the changes of IEL response in chickens, we measured the population of different subsets of avian IELs at different time points after primary inoculation of Newcastle disease virus (NDV) lentogenic strain (LaSota) and subsequent challenge with NDV velogenic strain- genotypes VII and VIII. Furthermore, NDV shed after each treatment was quantified. Specific-pathogen-free chickens were randomly divided into six groups of chickens, one to six, inoculated with phosphate buffered saline; NDV lentogenic strain (LaSota); genotype VII (GVII); LaSota and challenged with GVII (LSGVII); genotype VIII (GVIII); and group of LaSota and challenged with GVIII (LSGVIII). The chickens were euthanized at 12, 36, and 60 h postchallenge. Immunophenotyping of CD25⁺ IEL, CD3⁺ cells, CD4⁺ cells, and CD8⁺ cells was conducted using flow cytometer. Furthermore, virus shedding was measured using reverse transcriptase-quantitative polymerase chain reaction. Data were analyzed using a two-way analysis of variance (ANOVA). The results showed that the percentage population of IEL subsets was generally lower in the chickens inoculated with GVII or GVIII when compared with LaSota, LSGVII and LSGVIII inoculated groups. The NDV copy number was significantly higher in chickens challenged with NDV GVII or GVIII when compared with chickens inoculated with LaSota, LSGVII or LSGVIII. Taking together, NDV velogenic strain caused decrease in the population of subsets of chickens' IEL. However, inoculation of NDV LaSota may increase the population of avian IEL subsets and decrease shedding of virulent NDV.

Comparative Pathogenicity of Malaysian variant and very virulent infectious bursal disease viruses in chickens

Variant infectious bursal disease virus (vaIBDV) has been identified in various countries with significant economic losses. Recently, the first identification of variant strain in Malaysia was reported. The pathogenicity of the Malaysian variant, UPM1432/2019 and very virulent infectious bursal disease virus (vvIBDV), UPM1056/2018 strains were comparatively evaluated in specific-pathogen-free (SPF) chickens based on gross and histopathological examinations and viral load. Four-week-old SPF chickens were randomly divided into 3 groups; Group 1 served as the control, while groups 2 and 3 birds were challenged with the vaIBDV and vvIBDV, respectively. Three birds from each group were weighed, euthanised and necropsied at 2-, 3-, 4-, 5-, 7- and 21-days post-challenge (dpc). Unlike UPM1056/2018 group, birds from UPM1432/2019 group did not show clinical signs or death. UPM1056/2018 strain caused 11% mortality rate in the infected chickens. The bursal body index (BBIX) for UPM1432/2019- and UPM1056/2018 groups was < 0.7 from 2 dpc and continued to decrease to 0.49 and 0.45, respectively at 21 dpc. UPM1432/2019 strain was more persistent in the bursa than UPM1056/2018 strain. Both strains induced similar pathological lesions in SPF chicks. These results indicate that the Malaysian vaIBDV severely damaged the immune organs of chickens and was more persistent in bursal tissue than vvIBDV. The study provides insight into the pathogenicity of the variant strain as further study may be required to evaluate the efficacy of the current available IBD vaccines in Malaysia against the strain.

A recent perspective on fiber and hexon genes proteins analyses of fowl adenovirus toward virus infectivity-A review

Fowl adenovirus (FAdV) is a double-stranded DNA virus with a non-enveloped structure comprising three major proteins known as hexon, penton, and fiber. Molecular analysis which emphasizes on hexon and fiber proteins is currently the major focus of curiosity for FAdV antigenicity and pathogenicity. Recently, disease outbreaks associated with FAdV infections such as inclusion body hepatitis, hepatitis hydropericardium syndrome, and gizzard erosion, were commonly reported and continue to increase worldwide. Studies on the virulence gene of the virus were intensively conducted to provide a better understanding on the role of these major capsid proteins in the development of a safe and effective vaccine against the disease in the poultry industry. This paper highlights the variations of the fiber and hexon genes, their importance in genotypes and serotypes differentiation, and infectivity between FAdV strains. It appears that the L1 loop of hexon and the knob of fiber genes are the infectivity markers for FAdV infection. The fiber-2 protein plays a major role in FAdV pathogenicity than the hexon protein, while the fiber-1 protein is important for viral replication and assembly, regardless of virulence capability instead of infectivity. The hexon protein plays a major role in virus infectivity and tissue tropism. These findings could further enhance the knowledge of FAdV strains’ classification and evolution, diagnosis, and strategies to prevent and control FAdV infection and outbreaks in chicken farms.

Functional prediction of de novo uni-genes from chicken transcriptomic data following infectious bursal disease virus at 3-days post-infection

BACKGROUND

Infectious bursal disease (IBD) is an economically very important issue to the poultry industry and it is one of the major threats to the nation's food security. The pathogen, a highly pathogenic strain of a very virulent IBD virus causes high mortality and immunosuppression in chickens. The importance of understanding the underlying genes that could combat this disease is now of global interest in order to control future outbreaks. We had looked at identified novel genes that could elucidate the pathogenicity of the virus following infection and at possible disease resistance genes present in chickens.

RESULTS

A set of sequences retrieved from IBD virus-infected chickens that did not map to the chicken reference genome were de novo assembled, clustered and analysed. From six inbred chicken lines, we managed to assemble 10,828 uni-transcripts and screened 618 uni-transcripts which were the most significant sequences to known genes, as determined by BLASTX searches. Based on the differentially expressed genes (DEGs) analysis, 12 commonly upregulated and 18 downregulated uni-genes present in all six inbred lines were identified with false discovery rate of q-value < 0.05. Yet, only 9 upregulated and 13 downregulated uni-genes had BLAST hits against the Non-redundant and Swiss-Prot databases. The genome ontology enrichment keywords of these DEGs were associated with immune response, cell signalling and apoptosis. Consequently, the Weighted Gene Correlation Network Analysis R tool was used to predict the functional annotation of the remaining unknown uni-genes with no significant BLAST hits. Interestingly, the functions of the three upregulated uni-genes were predicted to be related to innate immune response, while the five downregulated uni-genes were predicted to be related to cell surface functions. These results further elucidated and supported the current molecular knowledge regarding the pathophysiology of chicken's bursal infected with IBDV.

CONCLUSION

Our data revealed the commonly up- and downregulated novel uni-genes identified to be immune- and extracellular binding-related, respectively. Besides, these novel findings are valuable contributions in improving the current existing integrative chicken transcriptomics annotation and may pave a path towards the control of viral particles especially towards the suppression of IBD and other infectious diseases in chickens.

Genetic Diversity of Recent Infectious Bursal Disease Viruses Isolated From Vaccinated Poultry Flocks in Malaysia

Vaccination is an essential component in controlling infectious bursal disease (IBD), however, there is a lack of information on the genetic characteristics of a recent infectious bursal disease virus (IBDV) that was isolated from IBD vaccinated commercial flocks in Malaysia. The present study investigated 11 IBDV isolates that were isolated from commercial poultry farms. The isolates were detected using reverse transcription-polymerase chain reaction (RT-PCR) targeting the hypervariable region (HVR) of VP2. Based on the HVR sequences, five isolates (IBS536/2017, IBS624/2017, UPM766/2018, UPM1056/2018, and UPM1432/2019) were selected for whole-genome sequencing using the MiSeq platform. The nucleotide and amino acid (aa) sequences were compared with the previously characterized IBDV strains. Deduced aa sequences of VP2HVR revealed seven isolates with 94–99% aa identity to very virulent strains (genogroup 3), two isolates with 97–100% aa identity to variant strains (genogroup 2), and two strains with 100% identity to the vaccine strain (genogroup 1) of IBDV. The phylogenetic analysis also showed that the isolates formed clusters with the respective genogroups. The characteristic motifs 222T, 249K, 286I, and 318D are typical of the variant strain and were observed for UPM1219/2019 and UPM1432/2019. In comparison, very virulent residues such as 222A, 249Q, 286T, and 318G were found for the vvIBDV, except for the UPM1056/2018 strain with a A222T substitution. In addition, the isolate has aa substitutions such as D213N, G254D, S315T, S317R, and A321E that are not commonly found in previously reported vvIBDV strains. Unlike the other vvIBDVs characterized in this study, UPM766/2018 lacks the MLSL aa residues in VP5. The aa tripeptides 145/146/147 (TDN) of VP1 were conserved for the vvIBDV, while a different motif, NED, was observed for the Malaysian variant strain. The phylogenetic tree showed that the IBDV variant clustered with the American and Chinese variant viruses and are highly comparable to the novel Chinese variants, with 99.9% identity. Based on the sequences and phylogenetic analyses, this is the first identification of an IBDV variant being reported in Malaysia. Further research is required to determine the pathogenicity of the IBDV variant and the protective efficacy of the current IBD vaccines being used against the virus.

Evaluation of the antigen relatedness and efficacy of a single vaccination with different infectious bronchitis virus strains against a challenge with Malaysian variant and QX-like IBV strains

BACKGROUND

The predominant infectious bronchitis virus (IBV) strains detected in chickens in Malaysia are the Malaysian variant (MV) and QX-like, which are associated with respiratory distress, nephropathy, and high mortality. On the other hand, the antigenic relatedness and efficacy of IBV vaccines against these 2 field IBV strains are not well characterized.

OBJECTIVES

This study aimed to determine the antigen relatedness and efficacy of different IB vaccine strains against a challenge with MV and QX-like strains.

METHODS

The antigen relatedness and the ability of different IB vaccine strains in conferring protection against MV and QX-like were assessed based on the clinical signs, macroscopic lesions, and ciliary activity.

RESULTS

The MV strain IBS037A/2014 showed minor antigenic subtype differences with the vaccine virus Mass H120 and 4/91 strains but showed major antigenic subtype differences with the K2 strain. The Malaysian QX-like strain IBS130/2015 showed major antigenic subtype differences with the MV strain IBS037A/2014 and the vaccine strains except for K2. Chickens vaccinated once with Mass (H120) or with non-Mass (4/91 and K2) developed antibody responses with the highest antibody titer detected in the groups vaccinated with H120 and 4/91. The mean ciliary activities of the vaccinated chickens were between 56 to 59% and 48 to 52% in chickens challenged with IBS037A/2014 and IBS130/2015, respectively. The vaccinated and challenged birds showed mild to severe lesions in the lungs and kidneys.

CONCLUSIONS

Despite the minor antigenic subtype differences, a single inoculation with Mass or non-Mass vaccines could not protect against the MV IBS037A/2014 and QX-like IBS130/2015.

Development of an Effective and Stable Genotype-Matched Live Attenuated Newcastle Disease Virus Vaccine Based on a Novel Naturally Recombinant Malaysian Isolate Using Reverse Genetics

Genotype VII Newcastle disease viruses are associated with huge economic losses in the global poultry industry. Despite the intensive applications of vaccines, disease outbreaks caused by those viruses continue to occur frequently even among the vaccinated poultry farms. An important factor in the suboptimal protective efficacy of the current vaccines is the genetic mismatch between the prevalent strains and the vaccine strains. Therefore, in the present study, an effective and stable genotype-matched live attenuated Newcastle disease virus (NDV) vaccine was developed using reverse genetics, based on a recently isolated virulent naturally recombinant NDV IBS025/13 Malaysian strain. First of all, the sequence encoding the fusion protein (F) cleavage site of the virus was modified in silico from virulent polybasic (RRQKRF) to avirulent monobasic (GRQGRL) motif. The entire modified sequence was then chemically synthesized and inserted into pOLTV5 transcription vector for virus rescue. A recombinant virus termed mIBS025 was successfully recovered and shown to be highly attenuated based on OIE recommended pathogenicity assessment indices. Furthermore, the virus was shown to remain stably attenuated and retain the avirulent monobasic F cleavage site after 15 consecutive passages in specific-pathogen-free embryonated eggs and 12 passages in one-day-old chicks. More so, the recombinant virus induced a significantly higher hemagglutination inhibition antibody titre than LaSota although both vaccines fully protected chicken against genotype VII NDV induced mortality and morbidity. Finally, mIBS025 was shown to significantly reduce both the duration and quantity of cloacal and oropharyngeal shedding of the challenged genotype VII virus compared to the LaSota vaccine. These findings collectively indicate that mIBS025 provides a better protective efficacy than LaSota and therefore can be used as a promising vaccine candidate against genotype VII NDV strains.

Exploring the Prospects of Engineered Newcastle Disease Virus in Modern Vaccinology

Many traditional vaccines have proven to be incapable of controlling newly emerging infectious diseases. They have also achieved limited success in the fight against a variety of human cancers. Thus, innovative vaccine strategies are highly needed to overcome the global burden of these diseases. Advances in molecular biology and reverse genetics have completely restructured the concept of vaccinology, leading to the emergence of state-of-the-art technologies for vaccine design, development and delivery. Among these modern vaccine technologies are the recombinant viral vectored vaccines, which are known for their incredible specificity in antigen delivery as well as the induction of robust immune responses in the vaccinated hosts. Although a number of viruses have been used as vaccine vectors, genetically engineered Newcastle disease virus (NDV) possesses some useful attributes that make it a preferable candidate for vectoring vaccine antigens. Here, we review the molecular biology of NDV and discuss the reverse genetics approaches used to engineer the virus into an efficient vaccine vector. We then discuss the prospects of the engineered virus as an efficient vehicle of vaccines against cancer and several infectious diseases of man and animals.

Molecular Characterization of QX-Like and Variant Infectious Bronchitis Virus Strains in Malaysia Based on Partial Genomic Sequences Comprising the S-3a/3b-E-M-Intergenic Region-5a/5b-N Gene Order

Infectious bronchitis virus (IBV) is one of the major poultry pathogens of global importance. However, the prevalence of IBV strains in Malaysia is poorly characterized. The partial genomic sequences (6.8 kb) comprising the S-3a/3b-E-M-intergenic region-5a/5b-N gene order of 11 Malaysian IBVs isolated in 2014 and 2015 were sequenced using next-generation sequencing technology. Phylogenetic and pairwise sequence comparison analysis showed that the isolated IBVs are divided into two groups. Group 1 (IBS124/2015, IBS125/2015, IBS126/2015, IBS130/2015, IBS131/2015, IBS138/2015, and IBS142/2015) shared 90%-95% nucleotide and deduced amino acid similarities to the QX-like strain. Among these isolates, IBS142/2015 is the first IBV detected in Sarawak state located in East Malaysia (Borneo Island). Meanwhile, IBV isolates in Group 2 (IBS037A/2015, IBS037B/2015, IBS051/2015, and IBS180/2015) were 91.62% and 89.09% identical to Malaysian variant strain MH5365/95 (EU086600) at nucleotide and amino acid levels, respectively. In addition, all studied IBVs were distinctly separate from Massachusetts (70%-72% amino acid similarity) and European strains including 793/B, Italy-02, and D274 (68%-73% amino acid similarity). Viruses in Group 1 have the insertion of three amino acids at positions 23, 121, and 122 of the S1 protein and recombinant events detected at nucleotide position 4354-5864, with major parental sequence derived from QX-like (CK-CH-IBYZ-2011) and a minor parental sequence derived from Massachusetts vaccine strain (H120). This study demonstrated coexistence of the IBV Malaysian variant strain along with the QX-like strain in Malaysia.

Velogenic newcastle disease virus tissue tropism and pathogenesis of infection in chickens by application of in situ PCR, immunoperoxase staining and HE staining

Limited deep studies are available in the field of early stages of pathogenesis of Newcastle disease virus (NDV) infection and tissue tropism of NDV. In this study, 24 specific pathogen free (SPF) chickens of white leghorn breed were infected with Newcastle disease (ND) by intranasal administration of 10⁵ 50% EID50/0.1 mL of velogenic NDV (vNDV). A second group of 15 chickens were kept as a control group. Chickens were monitored every day to record clinical signs. Infected chickens were euthanized by cervical dislocation at successive times, namely at hours (hrs) 2, 4, 6, 12, days 1, 2, 4, and 6 post-inoculation (pi). Whereas, control group chickens were euthanized on days 0, 1, 2, 4, and 6 pi. Tissues of brain, trachea, lung, caecal tonsil, liver, kidney, spleen, heart, proventriculus, intestine, and thymus were collected, fixed in 10% buffered formalin, embedded in paraffin, and sectioned. HS staining, immunoperoxidase staining (IPS) and in situ PCR were applied. It was concluded that at hr 2 pi, virus seemed to be inclined to trachea and respiratory tract. Meanwhile, it attacked caecal tonsils, intestine and bursa of Fabricus. While primary viraemia was ongoing, virus created footing in kidney and thymus. At hr 4 pi, proventriculus, liver, and spleen were attacked. However, at hr 6 pi, brain and heart were involved. Secondary viraemia probably started as early as hr 12 pi since all collected tissues were positive. Tissue tropism was determined in trachea, caecal tonsil, liver, bursa of Fabricius, intestine, proventriculus, lung, spleen, thymus, kidney, heart, and brain.

Differential activation of intraepithelial lymphocyte-natural killer cells in chickens infected with very virulent and vaccine strains of infectious bursal disease virus

To gain insights into the role of CD3^-/28.4⁺ intraepithelial lymphocytes-natural killer (CD3^-/28.4⁺IEL-NK) cells during infectious bursal disease virus (IBDV) infection, characterisation of the cells was performed following infection with different strains of the virus. In vitro treatment with IL-18 or ionomycin/PMA successfully stimulated and activated the cells via a significant increase in the expression of CD69, B-Lec, CHIR-AB1 and NK-lysin. Similarly, chickens infected with the vaccine strain of IBDV also up-regulated the expression of CD69, B-Lec, CHIR-AB1 and NK-lysin in CD3^-/28.4⁺ IEL-NK cells up to 3 days post infection (dpi) and down-regulated the expression of the inhibitory receptor B-NK at 3 dpi. On the contrary, infection with the very virulent IBDV (vvIBDV) strain lead to a reduced activation of the cells by down-regulating the expression of the CD69, CHIR-AB1 and NK-lysin especially at 1 dpi. These findings altogether demonstrate the differential activation of CD3^-/28.4⁺IEL-NK cells in chicken following infection with the vaccine or very virulent strains of IBDV. The study therefore provides an important clue into the differential pathogenesis of IBDV infection in chicken. Further studies are however required to determine the functional importance of these findings during IBDV vaccination and infection.

Comparative Pathogenicity of Malaysian QX-like and Variant Infectious Bronchitis Virus Strains in Chickens at Different Age of Exposure to the Viruses

Infectious bronchitis viruses (IBVs) circulating in Malaysia are classified into two groups as Malaysian QX-like and variant strains. In this study, the pathogenicity of IBS130/2015 (QX-like) and IBS037A/2014 (variant) IBVs in 1-day-old and 30-day-old specific pathogen free (SPF) chickens was characterized. Both strains caused respiratory and kidney infections based on immunohistochemistry (IHC), real-time quantitative polymerase chain reaction (qPCR) and a ciliostasis study; however, the results showed that the QX-like strain was more pathogenic, caused higher mortality and showed higher tissue tropism for the kidney than the variant strain. In contrast, despite causing low or no mortality depending on the age of the infected chickens, the Malaysian variant strain showed high tissue tropism for the respiratory tract compared with the QX-like strain. IHC and qPCR indicated the presence of both IBV strains in the epithelial lining of villi in the jejunum and the caecal tonsil; however, no pathological changes were detected in these organs. Both the Malaysian QX-like and variant IBV strains are able to infect the respiratory tract and kidney of chickens irrespective of age.

Bursal immunopathology responses of specific-pathogen-free chickens and red jungle fowl infected with very virulent infectious bursal disease virus

Very virulent infectious bursal disease virus (vvIBDV) targets B lymphocytes in the bursa of Fabricius (BF), causing immunosuppression and increased mortality rates in young birds. There have been few studies on the host immune response following vvIBDV infection at different inoculum doses in chickens with different genetic backgrounds. In this study, we characterized the immune responses of specific-pathogen-free (SPF) chickens and Malaysian red jungle fowl following infection with vvIBDV strain UPM0081 at 10^3.8 and 10^6.8 times the 50% embryo infectious dose (EID₅₀). The viral burden, histopathological changes, immune cell populations, and expression of immune-related genes were measured and compared between infected and uninfected bursa at specific intervals. The populations of KUL1⁺, CD3⁺CD4⁺ and CD3⁺CD8⁺ cells were significantly increased in both types of chickens at 3 dpi, and there was significant early depletion of IgM⁺ B cells at 1 dpi in the red jungle fowl. vvIBDV infection also induced differential expression of genes that are involved in Th1 and pro-inflammatory responses, with groups receiving the higher dose (10^6.8 EID₅₀) showing earlier expression of IFNG, IL12B, IL15, IL6, CXCLi2, IL28B, and TLR3 at 1 dpi. Although both chicken types showed equal susceptibility to infection, the red jungle fowl were clinically healthier than the SPF chickens despite showing more depletion of IgM⁺ B cells and failure to induce IFNB activation. In conclusion, high-dose vvIBDV infection caused an intense early host immune response in the infected bursa, with depletion of IgM⁺ B cells, bursal lesions, and cytokine expression as a response to mitigate the severity of the infection.

Bursal transcriptome profiling of different inbred chicken lines reveals key differentially expressed genes at 3 days post-infection with very virulent infectious bursal disease virus

Infectious bursal disease is a highly contagious disease in the poultry industry and causes immunosuppression in chickens. Genome-wide regulations of immune response genes of inbred chickens with different genetic backgrounds, following very virulent infectious bursal disease virus (vvIBDV) infection are poorly characterized. Therefore, this study aims to analyse the bursal tissue transcriptome of six inbred chicken lines 6, 7, 15, N, O and P following infection with vvIBDV strain UK661 using strand-specific next-generation sequencing, by highlighting important genes and pathways involved in the infected chicken during peak infection at 3 days post-infection. All infected chickens succumbed to the infection without major variations among the different lines. However, based on the viral loads and bursal lesion scoring, lines P and 6 can be considered as the most susceptible lines, while lines 15 and N were regarded as the least affected lines. Transcriptome profiling of the bursa identified 4588 genes to be differentially expressed, with 2985 upregulated and 1642 downregulated genes, in which these genes were commonly or uniquely detected in all or several infected lines. Genes that were upregulated are primarily pro-inflammatory cytokines, chemokines and IFN-related. Various genes that are associated with B-cell functions and genes related to apoptosis were downregulated, together with the genes involved in p53 signalling. In conclusion, bursal transcriptome profiles of different inbred lines showed differential expressions of pro-inflammatory cytokines and chemokines, Th1 cytokines, JAK-STAT signalling genes, MAPK signalling genes, and their related pathways following vvIBDV infection.

Induction of a robust immune response against avian influenza virus following transdermal inoculation with H5-DNA vaccine formulated in modified dendrimer-based delivery system in mouse model

This study was aimed to evaluate the immunogenicity of recombinant plasmid deoxyribonucleic acid (DNA), pBud-H5-green fluorescent protein (GFP)-interferon-regulatory factor (IRF)3 following delivery using polyamidoamine (PAMAM) dendrimer and transactivator of transcription (TAT)-conjugated PAMAM dendrimer as well as the effect of IRF3 as the genetic adjuvant. BALB/c mice were vaccinated transdermally with pBud-H5-GFP, PAMAM/pBud-H5-GFP, TAT-PAMAM/pBud-H5-GFP, and TAT-PAMAM/pBud-H5-GFP-IRF3. The expression analysis of H5 gene from the blood by using quantitative real-time reverse transcriptase polymerase chain reaction confirmed the ability of PAMAM dendrimer as a carrier for gene delivery, as well as the ability of TAT peptide to enhance the delivery efficiency of PAMAM dendrimer. Mice immunized with modified PAMAM by TAT peptide showed higher hemagglutination inhibition titer, and larger CD3⁺/CD4⁺ T cells and CD3⁺/CD8⁺ T cells population, as well as the production of cytokines, namely, interferon (IFN)-γ, interleukin (IL)-2, IL-15, IL-12, IL-6, and tumor necrosis factor-α compared with those immunized with native PAMAM. These results suggest that the function of TAT peptide as a cell-penetrating peptide is able to enhance the gene delivery, which results in rapid distribution of H5 in the tissues of the immunized mice. Furthermore, pBud-H5-GFP co-expressing IRF3 as a genetic adjuvant demonstrated the highest hemagglutination inhibition titer besides larger CD3⁺/CD4⁺ and CD3⁺/CD8⁺ T cells population, and strong Th1-like cytokine responses among all the systems tested. In conclusion, TAT-PAMAM dendrimer-based delivery system with IRF3 as a genetic adjuvant is an attractive transdermal DNA vaccine delivery system utilized to evaluate the efficacy of the developed DNA vaccine in inducing protection during challenge with virulent H5N1 virus.

Characterization of Chicken Splenic-Derived Dendritic Cells Following Vaccine and Very Virulent Strains of Infectious Bursal Disease Virus Infection

Studies have shown that infectious bursal disease virus (IBDV) infects lymphoid cells, mainly B cells and macrophages. This study was aimed to examine the involvement of chicken splenic-derived dendritic cells (ch-sDCs) in specific-pathogen-free chickens following inoculation with IBDV vaccine strain (D78) and a very virulent (vv) strain (UPM0081). Following IBDV infection, enriched activated ch-sDCs were collected by using the negative selection method and were examined based on morphology and immunophenotyping to confirm the isolation method for dendritic cells (DCs). The presence of IBDV on enriched activated ch-sDCs was analyzed based on the immunofluorescence antibody test (IFAT), flow cytometry, and quantitative real-time PCR (RT-qPCR) while the mRNAs of several cytokines were detected using RT-qPCR. The isolated ch-sDCs resembled typical DC morphologies found in mammals by having a veiled shape and they grew in clusters. Meanwhile, the expression of DC maturation markers, namely CD86 and MHCII, were increased at day 2 and day 3 following vvIBDV and vaccine strain inoculation, respectively, ranging from 10% to 40% compared to the control at 2.55% (P < 0.05). At day 3 postinfection, IBDV VP3 proteins colocalized with CD86 were readily detected via IFAT and flow cytometry in both vaccine and vvIBDV strains. In addition, enriched activated ch-sDCs were also detected as positive based on the VP4 gene by RT-qPCR; however, a higher viral load was detected on vvIBDV compared to the vaccine group. Infection with vaccine and vvIBDV strains induced the enriched activated ch-sDCs to produce proinflammatory cytokines and Th1-like cytokines from day 3 onward; however, the expressions were higher in the vvIBDV group (P < 0.05). These data collectively suggest that enriched activated ch-sDCs were permissive to IBDV infection and produced a strong inflammatory and Th1-like cytokine response following vvIBDV infection as compared to the vaccine strain.

Global distributions and strain diversity of avian infectious bronchitis virus: a review

The poultry industry faces challenge amidst global food security crisis. Infectious bronchitis is one of the most important viral infections that cause huge economic loss to the poultry industry worldwide. The causative agent, infectious bronchitis virus (IBV) is an RNA virus with great ability for mutation and recombination; thus, capable of generating new virus strains that are difficult to control. There are many IBV strains found worldwide, including the Massachusetts, 4/91, D274, and QX-like strains that can be grouped under the classic or variant serotypes. Currently, information on the epidemiology, strain diversity, and global distribution of IBV has not been comprehensively reported. This review is an update of current knowledge on the distribution, genetic relationship, and diversity of the IBV strains found worldwide.

In vitro characterization of chicken bone marrow-derived dendritic cells following infection with very virulent infectious bursal disease virus

Infectious bursal disease is caused by infectious bursal disease virus (IBDV), an immunosuppressive virus that targets immune cells such as B cells and macrophages. However, the involvement of dendritic cells (DCs) during IBDV infection is not well understood. In this study the in vitro effects of live and inactivated very virulent IBDV (vvIBDV) UPM0081 on bone marrow-derived DCs (BM-DC) were characterized and compared with BM-DC treated with lipopolysaccharide (LPS). Morphologically, BM-DC treated with LPS and vvIBDV showed stellate shape when compared to immature BM-DC. In addition, LPS-treated and both live and inactivated vvIBDV-infected BM-DC expressed high levels of double positive CD86 and major histocompatibility complex class II antigens (>20%). vvIBDV-infected BM-DC showed significantly higher numbers of apoptotic cells compared to LPS. Replication of vvIBDV was detected in the infected BM-DC as evidenced by the increased expression of VP3 and VP4 IBDV antigens based on flow cytometry, real-time polymerase chain reaction and immunofluorescence tests. Levels of different immune-related genes such as interleukin-1β (IL-1β), CXCLi2 (IL-8), IL-18, interferon gamma (IFN-γ, IL-12α, CCR7 and Toll-like receptor-3 (TLR3) were measured after LPS and vvIBDV treatments. However, marked differences were noticed in the onset and intensity of the gene expression between these two treatment groups. LPS was far more potent than live and inactivated vvIBDV in inducing the expression of IL-1β, IL-18 and CCR7 while expression of Th1-like cytokines, IFN-γ and IL-12α were significantly increased in the live vvIBDV treatment group. Meanwhile, the expression of TLR3 was increased in live vvIBDV-infected BM-DC as compared to control. Inactivated vvIBDV-treated BM-DC failed to stimulate IFN-γ, IL-12α and TLR3 expressions. This study suggested that BM-DC may serve as another target cells during IBDV infection which require further confirmation via in vivo studies.

Farming of Plant-Based Veterinary Vaccines and Their Applications for Disease Prevention in Animals

Plants have been studied for the production of pharmaceutical compounds for more than two decades now. Ever since the plant-made poultry vaccine against Newcastle disease virus made a breakthrough and went all the way to obtain regulatory approval, research to use plants for expression and delivery of vaccine proteins for animals was intensified. Indeed, in view of the high production costs of veterinary vaccines, plants represent attractive biofactories and offer many promising advantages in the production of recombinant vaccine proteins. Furthermore, the possibility of conducting immunogenicity and challenge studies in target animals has greatly exaggerated the progress. Although there are no edible plant-produced animal vaccines in the market, plant-based vaccine technology has great potentials. In this review, development, uses, and advantages of plant-based recombinant protein production in various expression platforms are discussed. In addition, examples of plant-based veterinary vaccines showing strong indication in terms of efficacy in animal disease prevention are also described.

Absorption and Bioavailability of Nano-Size Reduced Calcium Citrate Fortified Milk Powder in Ovariectomized and Ovariectomized-Osteoporosis Rats

The aim of this study was to evaluate the effects of fortification and nano-size reduction on calcium absorption and bioavailability of milk powder formula in sham, ovariectomized, and ovariectomized-osteoporosis rats as a menopause and menopause-osteoporosis model. Skim milk powder and skim milk powder fortified with calcium citrate and the suitable doses of inulin, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), and vitamins D3, K1, and B6 were formulated based on the North American and Western European recommended dietary allowances. Optimization on cycle and pressure of high-pressure homogenizer was done to produce nano-fortified milk powder. In vivo study demonstrated that fortification and calcium citrate nano-fortified milk powder increased absorption and bioavailability of calcium, as well as bone stiffness and bone strength in sham, ovariectomized, and ovariectomized-osteoporosis rats. This study successfully developed an effective fortified milk powder for food application.

Detection and molecular characterization of infectious spleen and kidney necrosis virus from major ornamental fish breeding states in Peninsular Malaysia

'Gold standard' OIE reference PCR assay was utilized to detect the presence of infectious spleen and kidney necrosis virus (ISKNV) in freshwater ornamental fish from Malaysia. From total of 210 ornamental fish samples representing 14 species, ISKNV was detected in 36 samples representing 5 fish species. All positive cases did not show any clinical signs of ISKNV. Three restriction enzymes analyses showed that the fish were infected by identical strains of the same virus species within Megalocytivirus genus. Major capsid protein (MCP) genes of 10 ISKNV strains were sequenced and compared with 9 other reference nucleotide sequences acquired from GenBank. Sequence analysis of MCP gene showed that all strains detected in this study were closely related to the reference ISKNV with nucleotide sequence identity that was ranging from 99.8% to 100%. In addition, phylogenetic analysis of MCP gene revealed that viruses from genus Megalocytivirus can be divided into three genotypes: genotype 1 include reference ISKNV and all other strains that were detected in this study, genotype 2 include viruses closely related to red sea bream iridovirus (RSIV), and genotype 3 include viruses closely related turbot reddish body iridovirus (TRBIV).

Simvastatin modulates cellular components in influenza A virus-infected cells

Influenza A virus is one of the most important health risks that lead to significant respiratory infections. Continuous antigenic changes and lack of promising vaccines are the reasons for the unsuccessful treatment of influenza. Statins are pleiotropic drugs that have recently served as anti-influenza agents due to their anti-inflammatory activity. In this study, the effect of simvastatin on influenza A-infected cells was investigated. Based on the MTT cytotoxicity test, hemagglutination (HA) assay and qPCR it was found that simvastatin maintained cell viability and decreased the viral load significantly as compared to virus-inoculated cells. The expression of important pro-inflammatory cytokines (tumor necrosis factor-α, interleukin-6 and interferon-γ), which was quantified using ELISA showed that simvastatin decreased the expression of pro-inflammatory cytokines to an average of 2-fold. Furthermore, the modulation of actin filament polymerization was determined using rhodamine staining. Endocytosis and autophagy processes were examined by detecting Rab and RhoA GTPase protein prenylation and LC3 lipidation using western blotting. The results showed that inhibiting GTPase and LC3 membrane localization using simvastatin inhibits influenza replication. Findings of this study provide evidence that modulation of RhoA, Rabs and LC3 may be the underlying mechanisms for the inhibitory effects of simvastatin as an anti-influenza compound.

Prophylactic effect of herbal-marine compound (HESA-A) on influenza A virus infectivity

Background

Influenza virus is still a severe respiratory disease affecting human and other species. As conventional drugs are not recommended for long time because of side effects and drug resistance occurrence, traditional medication has been focused as alternative remedy. HESA-A is a natural compound from herbal-marine origin. Previous studies have reported the therapeutic properties of HESA-A on psoriasis vulgaris and different types of cancers and we also showed its anti-inflammatory effects against influenza A infection.

Methods

This study was designed to investigate the potential properties of HESA-A as prophylaxis or treatment. To investigate the prophylaxis or treatment activities of HESA-A, Madin-Darby Canine Kidney (MDCK) cells were exposed to HESA-A and influenza A virus in different manners of exposure and different time intervals. The results were evaluated by MTT and HA assays.

Results

It was found that HESA-A is much more effective against influenza cytopathic effects when it is applied for prophylaxis and also in concurrent treatment (p ≤ 0.05) but not in post-infection treatment (p ≥ 0.05).

Conclusion

In conclusion, HESA-A is significantly effective against influenza replication in prophylaxis application affecting the virus penetration/adsorption to the cell without any toxic effect on the cell viability.

Dietary putrescine effects on performance parameters, nutrient digestibility, intestinal morphology and tissue polyamine content of broilers fed low protein diet

This study was carried out to investigate the effects of dietary putrescine (PUT) on broiler's response fed low crude protein (CP) diets. A total of 192 male day old chicks were fed with four dietary treatments including two levels of PUT (0 and 0.03%) and two levels of CP (normal and low) with factorial combinations. Weekly growth performance, nutrient digestibility and intestinal morphology (at the age of 21 days) and liver and intestinal tissue polyamines content were measured. As a result of this study lower dietary CP had a significant (P<0.05) lower body weight gain (BWG) and improved protein efficiency ratio (PER). PUT improved energy efficiency ratio (EER) significantly (P<0.05). Dry matter (DM) digestibility was decreased by lower dietary CP whereas 0.03% PUT significantly (P<0.05) increased it. Low CP caused significant (P<0.05) greater calcium digestibility, while this effect was not found when PUT was added. PUT had no effect on intestine villous height and crypt depth. Polyamine content of intestine and liver was influenced by the age of the birds, while PUT had no effects on them. In conclusion, dietary PUT has beneficial effects on EER in chicks fed CP-deficient diet, indicating possible involvement of PUT in energy metabolism. PUT supplementation did not moderate the reduced BWG of the chicks fed low protein. Intestinal and liver polyamine concentration was mainly affected by dietary CP and age of the birds rather than dietary PUT.

Egg production, faecal pH and microbial population, small intestine morphology, and plasma and yolk cholesterol in laying hens given liquid metabolites produced by Lactobacillus plantarum strains

1. Various dosages of metabolite combinations of the Lactobacillus plantarum RI11, RG14 and RG11 strains (COM456) were used to study the egg production, faecal microflora population, faecal pH, small intestine morphology, and plasma and egg yolk cholesterol in laying hens. 2. A total of 500 Lohmann Brown hens were raised from 19 weeks to 31 weeks of age. The birds were randomly divided into 5 groups and fed on various treatment diets: (i) basal diet without supplementation of metabolites (control); (ii) basal diet supplemented with 0·3% COM456 metabolites; (iii) basal diet supplemented with 0·6% COM456 metabolites; (iv) basal diet supplemented with 0·9% COM456 metabolites; and (v) basal diet supplemented with 1·2% COM456 metabolites. 3. The inclusion of 0·6% liquid metabolite combinations, produced from three L. plantarum strains, demonstrated the best effect in improving the hens' egg production, faecal lactic acid bacteria population, and small intestine villus height, and reducing faecal pH and Enterobacteriaceae population, and plasma and yolk cholesterol concentrations. 4. The metabolites from locally isolated L. plantarum are a possible alternative feed additive in poultry production.

Pathogenicity of SspI-positive infectious bursal disease virus and molecular characterization of the VP2 hypervariable region

The pathogenicity of four isolates of infectious bursal disease virus (IBDV) that have restriction fragment length polymorphism patterns of very virulent IBDV (vvIBDV), based on the presence of SspI and TaqI sites in the VP2 hypervariable region, was studied in specific pathogen free chickens. Chickens inoculated with isolates 92/04, 94/B551 and 97/61 developed severe clinical signs with a high mortality ranging from 70 to 80%, whereas the 94/273 isolate caused 10% mortality. Regardless of the isolates, significant differences were noted in the bursal lesion scores and bursa:body weight ratio index in the infected groups in comparison with the control groups. However, the presence of lesions in non-bursal tissues, muscles, thymus and at the junction of the proventriculus and gizzard were found only in the 92/04, 97/61 and 94/B551 isolates. Restriction fragment length polymorphism and sequence analysis of the VP2 hypervariable region indicated that all the isolates can be classified as vvIBDV based on the presence of SspI and TaqI sites at nucleotide positions 1011 and 833, respectively. In addition, all the isolates had amino acid substitutions at P222A, V256I and L294I, which are characteristic for vvIBDV isolated from different parts of the world. All the isolates except 94/273 also had a StyI site at nucleotide position 888. The absence of a StyI site in this isolate was associated with amino acid substitution at 254 from G to S. The 94/273 also had an amino acid substitution at position 270 from A to E, which is variable in the STC, Cu1 and OH strains. The presence of amino acid substitutions from G254S andA270E in SspI- and TaqI-positive vvIBDV strains is very uncommon and has not been reported previously. These amino acid variations might have caused the 94/273 to become less virulent in specific pathogen free chickens and resemble a classical virulent IBDV strain.

Attenuation of influenza virus infectivity with herbal-marine compound (HESA-A): an in vitro study in MDCK cells

Background

The influenza virus is still one of the most important respiratory risks affecting humans which require effective treatments. In this case, traditional medications are of interest. HESA-A is an active natural biological compound from herbal-marine origin. Previous studies have reported that the therapeutic properties of HESA-A are able to treat psoriasis vulgaris and cancers. However, no antiviral properties have been reported.

Methods

This study was designed to investigate the potential antiviral properties of HESA-A and its effects in modulating TNF-α and IL-6 cytokine levels. HESA-A was prepared in normal saline as a stock solution (0.8 mg/ml, pH = 7.4). Percentages of cell survival when exposed to different concentrations of HESA-A at different time intervals was determined by MTT assay. To study the potential antiviral activity of HESA-A, Madin-Darby Canine Kidney (MDCK) cells were treated with the effective concentration (EC₅₀) of HESA-A (0.025 mg/ml) and 100 TCID₅₀/0.1 ml of virus sample under different types of exposure.

Results

Based on the MTT method and hemagglutination assay (HA), HESA-A is capable of improving cell viability to 31% and decreasing HA titre to almost 99% in co-penetration exposures. In addition, based on quantitative real-time PCR (qRT-PCR) and enzyme-linked immunosorbent assay (ELISA), it was found that HESA-A causes decrements in TNF-α and IL-6 cytokine expressions, which was significant for TNF-α (p ≤ 0.05) but not for IL-6.

Conclusion

In conclusion, HESA-A was effective against influenza infection through suppressing cytokine expression.

Immunochromatographic gold-based test strip for rapid detection of Infectious bursal disease virus antibodies

The immunochromatographic assay is an alternative method for simple and rapid detection of Infectious bursal disease virus (IBDV) in chickens using colloidal gold-antibody conjugate. The whole-virus antigen of IBDV (UPM04190 isolate) and the high-affinity polyclonal antibodies directed against IBDV were blotted onto nitrocellulose membranes for test and control lines, respectively. Evaluation of the strip was performed using serum samples from experimentally and naturally infected chickens. The results showed that the test strip was more sensitive than the commercial enzyme-linked immunosorbent assay (ELISA) because it could detect a dilution factor up to 120,000 (250 ELISA units) for positive samples. It was also specific, in that it detected IBDV antibodies and did not cross-react with antibodies to other chicken viruses. The method was rapid (2 min) in both clinical and field environments with samples needing only a minimum amount (50 µl) of blood to produce an acceptable detection signal. The pen-site test strip proved successful in monitoring the immune status of chickens against the IBDV infection.

Pathogenicity of fowl adenovirus in specific pathogen free chicken embryos

Inclusion body hepatitis (IBH) associated with fowl adenovirus (FAdV) infection has a worldwide distribution. The aim of the present study was to determine the pathogenicity of Malaysian FAdV serotype 9 (UPM04217) in specific pathogen free (SPF) embryonated chicken embryos. FAdV (titre 10(5.8)/ml) was inoculated into SPF embryonated chicken eggs (0.1 ml per egg) via the chorioallantoic membrane (CAM). There was 100% embryo mortality within 4-11 days post infection (dpi). The gross and microscopical lesions of the embryo were confined to the liver and were noted at 5, 7, 9 and 11 dpi. The liver was pale with multifocal areas of necrosis, fibrosis and haemorrhage. Microscopically, there was moderate to severe congestion and haemorrhage and severe and diffuse hepatocyte degeneration and necrosis, with intranuclear inclusion bodies (INIBs) and associated inflammation. Haemorrhage, congestion, degeneration, necrosis and hyperplasia of the CAM with INIBs were observed at 5, 7, 9 and 11 dpi. Varying degrees of congestion, haemorrhage, degeneration and necrosis were also observed in the yolk sac, kidney, spleen, heart and bursa of Fabricius. Ultrastructurally, numerous viral particles in the nucleus of hepatocytes were recorded at 7, 9 and 11 dpi, whereas at 5 dpi, fine granular and filamentous INIBs were observed. The INIBs in the CAM were present either as fine granular filamentous structures or as large viral inclusions. FAdV (UPM04217) is therefore highly pathogenic to SPF chicken embryos and the embryonic liver should be used for isolation and propagation of the virus.

Nutrition and immunity: the effects of the combination of arginine and tryptophan on growth performance, serum parameters and immune response in broiler chickens challenged with infectious bursal disease vaccine

To explore the effects of the combination of tryptophan (Trp) and arginine (Arg) on growth performance, serum parameters and immune response of broiler chickens challenged with intermediate plus strain of infectious bursal disease virus vaccine, an in vivo experiment was conducted. A corn-soybean meal-based diet containing different levels of Arg and Trp was used. Cobb500 male broiler chickens from 0 to 49 days of age were subjected to a diet supplemented with the combination of Trp and Arg. Growth performance parameters and serum parameters were measured at 27 and 49 days of age. To evaluate the immunomodulatory effects of the combination of Trp and Arg on the challenged chickens, we measured the serum levels of interferon-α, interferon-γ and immunoglobulin G at 27, 35, 42, and 49 days of age. The results showed that the three evaluated immune system parameters including interferon-α, interferon-γ and immunoglobulin G were significantly enhanced after treatment. This enhancement resulted in the recovery of infectious bursal disease virus-infected chickens compared with controls as confirmed by histopathological examinations. Moreover, serum parameters such as albumin and total protein increased, whereas the treatment decreased (P<0.05) the feed:gain ratio, aspartate amino-transferase, alkaline phosphatase, lactic dehydrogenase, triglyceride and cholesterol. These findings suggest that the combination of Arg and Trp has a regulatory effect on growth performance. Moreover, it modulates the systemic immune response against infectious bursal disease.

Efficacy of a bacteriophage isolated from chickens as a therapeutic agent for colibacillosis in broiler chickens

The efficacy of bacteriophage EC1, a lytic bacteriophage, against Escherichia coli O78:K80, which causes colibacillosis in poultry, was determined in the present study. A total of 480 one-day-old birds were randomly assigned to 4 treatments groups, each with 4 pens of 30 birds. Birds from the control groups (groups I and II) received PBS (pH 7.4) or 10(10) pfu of bacteriophage EC1, respectively. Group III consisted of birds challenged with 10(8) cfu of E. coli O78:K80 and treated with 10(10) pfu of bacteriophage EC1 at 2 h postinfection, whereas birds from group IV were challenged with 10(8) cfu of E. coli O78:K80 only. All the materials were introduced into the birds by intratracheal inoculation. Based on the results of the present study, the infection was found to be less severe in the treated E. coli-challenged group. Mean total viable cell counts of E. coli identified on eosin methylene blue agar (designated EMB + E. coli) in the lungs were significantly lower in treated, E. coli-challenged birds than in untreated, E. coli-challenged birds on d 1 and 2 postinfection. The EMB + E. coli isolation frequency was also lower in treated birds; no E. coli was detectable in blood samples on any sampling day, and E. coli were isolated only in the liver, heart, and spleen of treated chickens at a ratio of 2/6, 1/6, and 3/6, respectively, at d 1 postinfection. The BW of birds from the E. coli-challenged group treated with bacteriophage EC1 were not significantly different from those of birds from both control groups but were 15.4% higher than those of the untreated, E. coli-challenged group on d 21 postinfection. The total mortality rate of birds during the 3-wk experimental period decreased from 83.3% in the untreated, E. coli-challenged birds (group IV) to 13.3% in birds treated with bacteriophage EC1 (group III). These results suggest that bacteriophage EC1 is effective in vivo and could be used to treat colibacillosis in chickens.

Diagnostic methods for feline coronavirus: a review

Feline coronaviruses (FCoVs) are found throughout the world. Infection with FCoV can result in a diverse range of signs from clinically inapparent infections to a highly fatal disease called feline infectious peritonitis (FIP). FIP is one of the most serious viral diseases of cats. While there is neither an effective vaccine, nor a curative treatment for FIP, a diagnostic protocol for FCoV would greatly assist in the management and control of the virus. Clinical findings in FIP are non-specific and not helpful in making a differential diagnosis. Haematological and biochemical abnormalities in FIP cases are also non-specific. The currently available serological tests have low specificity and sensitivity for detection of active infection and cross-react with FCoV strains of low pathogenicity, the feline enteric coronaviruses (FECV). Reverse transcriptase polymerase chain reaction (RT-PCR) has been used to detect FCoV and is rapid and sensitive, but results must be interpreted in the context of clinical findings. At present, a definitive diagnosis of FIP can be established only by histopathological examination of biopsies. This paper describes and compares diagnostic methods for FCoVs and includes a brief account of the virus biology, epidemiology, and pathogenesis.

Gastrointestinal tract morphological alteration by unpleasant physical treatment and modulating role of Lactobacillus in broilers

1. An experiment was conducted to determine the effects of supposedly unpleasant physical treatment on broiler performance, small intestinal development and ameliorating role of probiotics. 2. The following treatments were applied from day one: (1) chicks exposed to normal human contact fed basal diet (control); (2) chicks were exposed to unpleasant physical treatment and fed basal diet (UPT-BD); and (3) chicks were exposed to unpleasant physical treatment and fed basal diet supplemented with Lactobacillus (UPT-BDL). Chicks were exposed to UPT from days 1 to 21. Different segments of gastrointestinal tract were sampled at 14, 28, 35 and 42 d of age. 3. Broilers of UPT-BD had lower feed consumption compared with control group at 7 d of age. Overall, UPT-BDL birds showed higher body weight gain (BWG) and better feed conversion ratio (FCR) over the course of the experiment. 4. Birds of UPT-BD had lower concentrations of lactic, propionic and butyric acids in the caecum as compared with other groups at 14 d of age. Acetic acid concentration was profoundly decreased in both UPT groups compared to the control. 5. Duodenal villus height of UPT-BD broilers showed a slight reduction compared to the control and UPT-BDL birds at 14 d of age. Afterwards until day 42, UPT-BDL birds showed the highest villus height among treatments in different parts of the small intestine. 6. The results suggested that, even though UPT did not have significant inhibitory effects on the development of the small intestine and broiler performance, it negatively affected bacterial metabolic end products in the caecum, which could be ameliorated by the addition of Lactobacillus.

Selected microbial groups and short-chain fatty acids profile in a simulated chicken cecum supplemented with two strains of Lactobacillus

Among the bacterial fermentation end products in the chicken cecum, butyrate is of particular importance because of its nutritional properties for the epithelial cell and pathogen inhibitory effects in the gut. An in vitro experiment, operated with batch bioreactor, was conducted to quantify butyric-producing bacteria in a simulated broiler cecum supplemented with Lactobacillus salivarius ssp. salicinius JCM 1230 and Lactobacillus agilis JCM 1048 during 24 h of incubation. Selected bacterial species were determined by real-time PCR and short-chain fatty acids and lactate concentrations were monitored. The results showed that after 24 h of incubation, Lactobacillus supplementation significantly increased the number of lactobacilli, bifidobacteria and Faecalibacterium prausnitzii in medium containing cecal content and lactobacilli supplementation (Cc + L) compared with the control (Cc). Addition of lactobacilli did not alter Escherichia coli and Clostridium butyricum, whereas it significantly (P < 0.05) reduced Salmonella in treatment Cc + L compared with the Cc treatment. Propionate and butyrate formation were significantly (P < 0.05) increased in treatment Cc + L as compared with the Cc treatment. Lactate was only detected in treatment containing 2 Lactobacillus strains. After 24 h of incubation, acetate concentration significantly (P < 0.05) decreased in all treatments. It was suggested that lactate produced by Lactobacillus in the cecal content improved the growth of butyric producers such as F. prausnitzii, which significantly increased butyrate accumulation. Additionally, the results showed that butyrate and propionate inhibited Salmonella without influencing the E. coli profile.