Key result
A newly developed duplex droplet digital PCR assay demonstrated high sensitivity (limit of detection 52 and 8.6 copies/reaction for B646L and EP402R) for detecting and differentiating ASFV strains.
Why the study?
EP402R-deleted ASFV strains lack hemadsorption ability and low viral loads yield false negatives or retests on real-time PCR, creating a need for a new method to detect and differentiate wild-type and gene-deleted strains.
A novel duplex ddPCR assay provides a highly sensitive method to detect and differentiate wild-type and EP402R-deleted African swine fever virus strains.
Answers are grounded in this paper and cite their sources.
Supports sensitive ASFV detection in research models; leaves open validation for veterinary field use.
African swine fever (ASF) is a highly fatal porcine disease caused by the African swine fever virus (ASFV), and resulting in huge economic losses across the globe. ASF has been raging in China for 3 years, and recently EP402R-deleted ASFV strains emerged, showing sub-acute or chronic symptoms in pigs and providing novel difficulties to monitor and control the disease as EP402R-deleted strains possess no hemadsorption (HAD) ability. In addition, the gene deletion virus with low viral load is prone to results retest or false negative due to the high cycle threshold (Ct) value under the current real-time polymerase chain reaction (PCR) detection method. Thus, a new method is needed to detect and distinguish wild strains and gene-deleted viruses. In this study, a duplex droplet digital polymerase chain reaction (ddPCR) assay based on the ASFV B646L and EP402R genes was established and showed good linearity (R2 > 0.99). The limit of detection for duplex ddPCR was 52 copies per reaction and 8.6 copies per reaction for B646L and EP402R, respectively. No cross-reaction with other porcine viruses [classical swine fever virus (CSFV), porcine reproductive and respiratory syndrome virus (PRRSV), porcine epidemic diarrhea virus (PEDV), porcine parvovirus (PPV), Japanese encephalitis virus (JEV), and porcine circovirus type 2 (PCV2)] was identified by this assay. In addition, 44 ASFV-suspicious clinical samples as well as EP402R-deleted ASFV were tested in parallel by duplex real-time PCR and ddPCR, indicative of a higher sensitivity which belonged to the duplex ddPCR assay. In summary, this is the first time that duplex ddPCR assay has been successfully developed to provide an efficient method to detect and differentiate ASFV wild-type and gene-deleted strains.
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Zhu et al. (2022) studied African swine fever (n=44). Duplex droplet digital polymerase chain reaction (ddPCR) assay vs. Duplex real-time PCR was evaluated on Limit of detection for B646L and EP402R genes. A newly developed duplex droplet digital PCR assay demonstrated high sensitivity (limit of detection 52 and 8.6 copies/reaction for B646L and EP402R) for detecting and differentiating ASFV strains.
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