A RAPID RESPONSE VACCINE DEVELOPMENT STRATEGY FOR NEWCASTLE DISEASE IN POULTRY
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Poultry is a major source of protein in sub-Saharan Africa and many other lower-income regions. Newcastle disease virus (NCDV) comprises a significant threat toward poultry production. While NCDV vaccines are routinely used in developed countries, those used in sub-Saharan Africa are mostly imported and are not specific to locally circulating strains. Indeed, the lack of rapid, field-based NCDV detection and the absence of costeffective production methods for pure, strain-specific vaccines hampers efficient poultry production throughout these regions. This remains a major problem for both subsistence and commercial farming. The aim for this study was firstly, to develop a field-based isothermal PCR assay for NCDV detection that employed a portable instrument and realtime data transfer application. Secondly, to use the nucleic acid sequence data obtained from field isolates to develop a protocol compatible with rapid emergency vaccine production for NCDV. To achieve this, the isothermal PCR detection assay was applied to field isolates from suspected NCDV outbreaks on commercial poultry farms in KwaZulu-Natal, South Africa, while for the vaccine development, the NCDV matrix gene of one of the isolates was sequenced and used to design primers for the recombinant cloning of this antigen into an adenoviral vector. This ‘vaccine vector' and a control adenoviral vector were each amplified in 293T cells and then used to infect both 293T cells as a production cell line and chicken embryo fibroblasts (CEF) as a preliminary model of the target host. Western blotting confirmed the successful expression of the V5 epitope tag by the control vector in both cell lines, which established the compatibility of the adenovirus vector as an appropriate carrier of the target antigen. Mass spectrometry confirmed expression of the NCDV matrix protein by the vaccine vector in both cell lines. In conclusion, the improved turnaround time from detection to the production of the vaccine antigen was under 6 weeks. The approach described here provides a rapid and cost-effective protocol for both the pathogen detection on-site and the production of pure vaccine antigens specific to an emerging field strain of NCDV within lower-income regions.
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