Abstract
Currently, African swine fever virus (ASFV) represents one of the most important economic threats for the global pork industry. Recently, significant advances have been made in the development of potential vaccine candidates to protect pigs against this virus. We have previously developed attenuated vaccine candidates by deleting critical viral genes associated with virulence. Here, we present the development of the accompanying genetic tests to discriminate between infected and vaccinated animals (DIVA), a necessity during an ASFV vaccination campaign. We describe here the development of three independent real-time polymerase chain reaction (qPCR) assays that detect the presence of MGF-360-12L, UK, and I177L genes, which were previously deleted from the highly virulent Georgia strain of ASFV to produce the three recombinant live attenuated vaccine candidates. When compared with the diagnostic reference qPCR that detects the p72 gene, all assays demonstrated comparable levels of sensitivity, specificity, and efficiency of amplification to detect presence/absence of the ASFV Georgia 2007/1 strain (prototype virus of the Eurasian lineage) from a panel of blood samples from naïve, vaccinated, and infected pigs. Collectively, the results of this study demonstrate the potential of these real-time PCR assays to be used as genetic DIVA tests, supporting vaccination campaigns associated with the use of ASFV-ΔMGF, ASFV-G-Δ9GL/ΔUK, and ASFV-ΔI177L or cell culture adapted ASFV-ΔI177LΔLVR live attenuated vaccines in the field.
Highlights
African swine fever virus (ASFV), an arbovirus, and unique member of the Asfarviridae family, is a double-stranded DNA virus with a varying genome length that ranges between 170 and 193 kbp, encoding for between 150 and 167 open reading frames [1]
Just recently (07/15/2021), The Friedrich-Loeffler-Institute reported the first cases of ASFV in domestic pigs in Germany, and (7/28/2021) The U.S Department of Agriculture’s (USDA) Foreign Animal Disease Diagnostic Laboratory confirmed the presence of ASFV in Dominican Republic, being this first report of this genotype in the Americas
Recombinant viruses ASFV- MGF, ASFV-G- 9GL/ UK ASFV- I177L and ASFV- I177L LVR, all previously developed in our laboratory [10,11,12,13], as well as the parental virus ASFV Georgia 2007/1 strain (ASFV-G), a field isolate kindly provided by Nino Vepkhvadze from the Laboratory of the Ministry of Agriculture (LMA) in Tbilisi, Republic of Georgia were used to conduct this study
Summary
African swine fever virus (ASFV), an arbovirus, and unique member of the Asfarviridae family, is a double-stranded DNA virus with a varying genome length that ranges between 170 and 193 kbp, encoding for between 150 and 167 open reading frames [1]. A recent report of the World Organization for Animal Health (https://www.oie.int/app/uploads/2021/03/report-47global-situation-asf.pdf) regarding the global situation of ASFV between 2016 and 2020 indicates that ASFV is endemic in most Sub-Saharan African countries and is causing outbreaks throughout Europe and Asia resulting in the loss of more than 6,000,000 domestic pigs, representing 82% of global losses to ASF during this time period. In this context, the increased number of cases currently reported out of Africa are mostly attributed to the emergence of the Eurasian ASFV lineage (genotype II) [3], one of 23 ASFV genotypes [4].
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