Development of a non-radioactive digoxigenin cDNA probe for the detection of avian encephalomyelitis virus

Progress in research on the molecular biological detection techniques of avian encephalomyelitis

Avian encephalomyelitis (AE) is a highly infectious disease caused by the avian encephalomyelitis virus (AEV), which primarily affects the central nervous system of 1- to 4-week-old chicks and causes significant economic losses in the worldwide poultry industry. Despite heavy dependency on vaccine immunization, AEV has persisted on farms for extended periods, which increases its virulence and makes quick and accurate detection crucial to preventing and controlling the disease. Classical diagnostic methods have been unable to meet the current requirements for rapid diagnosis of AE cases. To address this issue, this paper reviews the etiological and molecular biological detection techniques of AE, and it seeks to provide a reference for future research and to establish differential diagnostic techniques for AE epidemiological investigation, identification of epidemic strains, and early diagnosis of clinical cases. Through improving our understanding of AE, we can better combat the disease and protect the global poultry industry.

Structural Analysis of Avian Encephalomyelitis Virus Polyprotein for Development of Multi Epitopes Vaccine Using Immunoinformatics Approach

Avian Encephalomyelitis (AE) is the disease caused by avian encephalomyelitis virus (AEV). The disease mainly affects young birds nervous system worldwide causing high morbidity and variable mortality rate in chicks and noticed egg dropping and hatchability in mature hens. Vaccination is the only way to control AEV infection since there is no treatment yet to the avian encephalomyelitis. This study aimed to use immunoinformatics approaches to predict multi epitopes vaccine from the AEV polyprotein that could elicit both B and T cells. The vaccine construct comprises 482 amino acids obtained from epitopes predicted against B and T cells by IEDB server, adjuvant, linkers and 6-His-tag. The chimeric vaccine was potentially antigenic and nonallergic and demonstrated thermostability and hydrophilicity in protparam server. The solubility of the vaccine was measured in comparison to E. coli proteins. The stability was also assessed by disulfide bonds engineering to reduce the high mobility regions in the designed vaccine. Furthermore molecular dynamics simulation further strengthen stability of the predicted vaccine. Tertiary structure of the vaccine construct after prediction, refinement was used for molecular docking with chicken alleles BF2*2101 and BF2*0401 and the docking process demonstrated favourable binding energy score of -337.47 kcal/mol and -326.87 kcal/mol, respectively. Molecular cloning demonstrated the potential clonability of the chimeric vaccine in pET28a(+) vector. This could guarantee the efficient translation and expression of the vaccine within suitable expression vector.

Analysis of viral protein-2 encoding gene of avian encephalomyelitis virus from field specimens in Central Java region, Indonesia

Aim:

Avian encephalomyelitis (AE) is a viral disease which can infect various types of poultry, especially chicken. In Indonesia, the incidence of AE infection in chicken has been reported since 2009, the AE incidence tends to increase from year to year. The objective of this study was to analyze viral protein 2 (VP-2) encoding gene of AE virus (AEV) from various species of birds in field specimen by reverse transcription polymerase chain reaction (RT-PCR) amplification using specific nucleotides primer for confirmation of AE diagnosis.

Materials and Methods:

A total of 13 AEV samples are isolated from various species of poultry which are serologically diagnosed infected by AEV from some areas in central Java, Indonesia. Research stage consists of virus samples collection from field specimens, extraction of AEV RNA, amplification of VP-2 protein encoding gene by RT-PCR, separation of RT-PCR product by agarose gel electrophoresis, DNA sequencing and data analysis.

Results:

Amplification products of the VP-2 encoding gene of AEV by RT-PCR methods of various types of poultry from field specimens showed a positive results on sample code 499/4/12 which generated DNA fragment in the size of 619 bp. Sensitivity test of RT-PCR amplification showed that the minimum concentration of RNA template is 127.75 ng/µl. The multiple alignments of DNA sequencing product indicated that positive sample with code 499/4/12 has 92% nucleotide homology compared with AEV with accession number AV1775/07 and 85% nucleotide homology with accession number ZCHP2/0912695 from Genbank database. Analysis of VP-2 gene sequence showed that it found 46 nucleotides difference between isolate 499/4/12 compared with accession number AV1775/07 and 93 nucleotides different with accession number ZCHP2/0912695.

Conclusions:

Analyses of the VP-2 encoding gene of AEV with RT-PCR method from 13 samples from field specimen generated the DNA fragment in the size of 619 bp from one sample with sample code 499/4/12. The sensitivity rate of RT-PCR is to amplify the VP-2 gene of AEV until 127.75 ng/µl of RNA template. Compared to Genbank databases, isolate 499/4/12 has 85% and 92% nucleotide homology.

Development of a SYBR Green real-time RT-PCR assay for the detection of avian encephalomyelitis virus

Avian encephalomyelitis virus (AEV) causes epidemic diseases in poultry worldwide. A SYBR Green real-time reverse transcription-polymerase chain reaction (rRT-PCR) assay was developed for the rapid detection and quantitation of AEV in this study. A pair of specific primers was designed in the highly conserved VP1 gene of this virus. When comparing this assay with conventional RT-PCR, the rRT-PCR assay was 100 times more sensitive and could detect levels as low as 10 standard DNA copies of the AEV SX strain. The specificity of this technique was evaluated in five other avian pathogens. The AEV RNA was detected as early as three days post-infection in chicken embryos. All 18 clinical chicken brains collected from an AEV outbreak in Northwestern China were detected to be positive (100%) using the rRT-PCR assay. However, only 5 of the 18 samples were positive (28%) using the conventional RT-PCR. The results were confirmed by virus isolation in chicken embryos. This high sensitivity, specificity, and simplicity of the SYBR Green rRT-PCR approach can be a more effective method than the conventional one for AEV diagnosis and surveillance.