USA, Washington. Researchers with the US Dept. of Agriculture’s Agricultural Research Service have developed a genetically modified virus that provides complete protection from a strain of ASF responsible for recent outbreaks in East Asia and Central Europe.
The pre-printed study published in bioRxiv is called “Development of a highly effective African swine fever virus vaccine by deletion of the I177L gene results in sterile immunity against the current epidemic Eurasia strain“ and was executed by Manuel V. Borca, Elizabeth Ramirez Medina, Ediane Silva, Elizabeth Vuono, Ayushi Rai, Sarah Pruitt, Lauren G. Holinka, Lauro Velazquez Salinas, James Zhu and Douglas P. Gladue.
African swine fever virus (ASFV) is the etiological agent of a contagious and often lethal disease of domestic pigs that has significant economic consequences for the swine industry. The disease is devastating the swine industry in Central Europe and East Asia, with current outbreaks caused by circulating strains of ASFV derived from the 2007 Georgia isolate (ASFV-G), a genotype II ASFV.
In the absence of any available vaccines, African Swine Fever (ASF) outbreak containment relies on control and culling of infected animals. Limited cross protection studies suggest that in order to ensure a vaccine is effective it must be derived from the current outbreak strain or at the very least from an isolate with the same genotype.
Here the researchers report the discovery that deletion of a previously uncharacterized gene, I177L, from the highly virulent ASFV-G produces complete virus attenuation in swine. Animals inoculated intramuscularly with the virus lacking the I177L gene, ASFV-G-ΔI177L, in a dose range of 102 to 106 HAD50 remained clinically normal during the 28 day observational period.
All ASFV-G-ΔI177L-infected animals had low viremia titers, showed no virus shedding, developed a strong virus-specific antibody response and, importantly, they were protected when challenged with the virulent parental strain ASFV-G. ASFV-G-ΔI177L is one of the few experimental vaccine candidate virus strains reported to be able to induce protection against the ASFV Georgia isolate, and the first vaccine capable of inducing sterile immunity against the current ASFV strain responsible for recent outbreaks.