“ASF vaccine possible within reasonable timeframe”


In December, the news broke that a potentially new vaccine for African Swine Fever (ASF) had been created by researchers from the USDA’s Ag- ricultural Research Service. An article appeared on the website Biorxiv, mentioning that the researchers had found a previously uncharacter- ised virus gene, called I177L, which when deleted completely attenu- ates an isolate of the ASF virus obtained from the country Georgia. Dr Douglas Gladue, senior scientist at Plum Island Animal Disease Center, part of the ARS, is one of the lead scientists behind the publication.


Pig Progress: What have the reactions been to your discovery so far? Dr Douglas Gladue: “Our results with our new experimental vaccine AS- Fv-G-ΔI177L have been very promising, and has characteristics that ex- perimentally outperform our previously discovered vaccine candidates.”


Has the newly developed vaccine also been tested in farm conditions? “ASFv-G-ΔI177L has only been tested under experimental controlled conditions.”


What about scaling up production at this stage? “Our vaccine is still in the experimental stages and will require regulato- ry approval; this approval varies between countries. Currently there is no stable cell line capable of supporting ASFv vaccine growth, growing of our vaccine currently relies on isolation of primary swine macrophages.”


There have already been quite a few people asking me when this vac- cine would be available for use. Perhaps its early days, but could you say anything about that at all at this stage? “ASFv-G-ΔI177L is still in the experimental stage, so far it has been very promising, the time frame for regulatory approval and commercialisa- tion is unknown, but we believe it could be possible in a reasonable timeframe.”


Has there been contact with commercial pharmaceutical parties about marketing it? If so, which?


Molecular Biology Center in Madrid, Spain, are working to iden- tify which of ASFv’s, about 150 proteins are important for viru- lence, research that could lead to the development of a subunit vaccine, i.e. a vaccine to one or more specific proteins that could confer immunity to infection via neutralising antibodies. Dr Juergen Richt and his colleagues at Kansas State Univer- sity (KSU) are also focused on determining the appropriate combinations of ASFv proteins and how best to deliver them for a safe and effective vaccine.


Company attempts to control ASF If there are for-profit companies working on developing a vaccine to ASFv, they are keeping a low profile. Flow Pharma is developing a 100% synthetic vaccine


The research team at Plum Island Animal Disease Center that authored the article. Dr Gladue is seated front right.


“Currently we do not have a commercial partner for ASFv-G-ΔI177L.”


In the light of the developments in Europe and Asia, I could imagine there is massive interest from many corners of the world. Has there been contact with authorities of countries? “None that I am currently aware of.”


What made you look into this particular gene? “ASF has over 150 predicted genes, the exact number of genes varies by isolate. Very few of these genes have been studied experimentally, with some having a predicted function due to similarity with other genes (cellular or viral). Using a bioinformatics pipeline, we ranked genes with a high likelihood of being important for immune evasion. Our top-three candidates were genes Ep152R, L83L, and I177L. Ep152R we determined was an essential gene and could not be deleted (PMID 27497620). L83L we were able to delete but there was no effect on vi- rus virulence (PMID 29605728). I177L, our third candidate, when delet- ed was fully attenuated and became our vaccine candidate.”


containing peptides, specifically class 1 and class 2 epitopes, that represent various ASFv proteins. The company believes that the key to generating protective immunity is not only what is delivered but how it is delivered soh that the immune system has the best chance of responding. And while peptides have been studied as vaccines for many years, the literature is replete with failures. This is because most peptides by themselves are not immunogenic enough to stimulate an immune response. The delivery system uses peptides and adjuvants encapsulat- ed in PLGA microparticles of a specific size to target macro- phages and other antigen presenting cells. The company is in the process of identifying reactive class 1 and class 2 epitopes so that a protective challenge study of ASFv in pigs can be performed in the very near future.


▶PIG PROGRESS | Volume 36, No. 1, 2020 23


ILLUSTRATION: SHUTTERSTOCK


PHOTO: ARS-USDA


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