Abstract
BackgroundThe ongoing African swine fever virus (ASFv) epidemic has had a major impact on pig production globally and biosecurity efforts to curb ASFv infectivity and transmission are a high priority. It has been recently identified that feed and feed ingredients, along with drinking water, can serve as transmission vehicles and might facilitate transboundary spread of ASFv. Thus, it is important to test the antiviral activity of regulatory compatible, antiviral feed additives that might inhibit ASFv infectivity in feed. One promising group of feed additive candidates includes medium-chain fatty acids (MCFA) and monoglyceride derivatives, which are known to disrupt the lipid membrane surrounding certain enveloped viruses and bacteria.ResultsThe antiviral activities of selected MCFA, namely caprylic, capric, and lauric acids, and a related monoglyceride, glycerol monolaurate (GML), to inhibit ASFv in liquid and feed conditions were investigated and suitable compounds and inclusion rates were identified that might be useful for mitigating ASFv in feed environments. Antiviral assays showed that all tested MCFA and GML inhibit ASFv. GML was more potent than MCFA because it worked at a lower concentration and inhibited ASFv due to direct virucidal activity along with one or more other antiviral mechanisms. Dose-dependent feed experiments further showed that sufficiently high GML doses can significantly reduce ASFv infectivity in feed in a linear manner in periods as short as 30 min, as determined by infectious viral titer measurements. Enzyme-linked immunosorbent assay (ELISA) experiments revealed that GML treatment also hinders antibody recognition of the membrane-associated ASFv p72 structural protein, which likely relates to protein conformational changes arising from viral membrane disruption.ConclusionTogether, the findings in this study indicate that MCFA and GML inhibit ASFv in liquid conditions and that GML is also able to reduce ASFv infectivity in feed, which may help to curb disease transmission.
Highlights
The African swine fever virus (ASFv) causes lethal disease in pigs with mortality rates that can approach 100% in naïve pig populations [1, 2]
Solution-phase virucidal assay experiments identified that all tested medium-chain fatty acids (MCFA) and glycerol monolaurate (GML) inhibited ASFv at 5 mmol/L compound concentrations while more detailed investigations showed that only GML maintained a similar level of virucidal activity at 250 μmol/L compound concentration
An MCFA mixture and GML were tested as two feed additive candidates to inhibit ASFv infectivity in feed, as measured by infectious viral titer measurements
Summary
The African swine fever virus (ASFv) causes lethal disease in pigs with mortality rates that can approach 100% in naïve pig populations [1, 2]. Niederwerder et al showed that ASFv can be transmitted orally in liquids and in plant-based feed [13], which fits with epidemiological findings linking feed transmission to a past ASFv outbreak in Latvia [14] Such findings motivate the development of mitigation strategies to reduce the infectivity of virus-contaminated feed and decrease feed-mediated infection probability, i.e., suppress growth of virus particle and infected cell populations in pigs [15]. While formaldehyde is approved as a swine feed additive in the United States, it is banned as a feed additive in some jurisdictions such as the European Union [Regulation (EU) 2018/183], which has led to the exploration of other regulatory acceptable feed additives with potential antiviral properties In this regard, one promising class of feed additives consists of medium-chain fatty acids (MCFA), which are 6–12 carbon long saturated fatty acids. One promising group of feed additive candidates includes medium-chain fatty acids (MCFA) and monoglyceride derivatives, which are known to disrupt the lipid membrane surrounding certain enveloped viruses and bacteria
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