A Cell Culture-Adapted Vaccine Virus against the Current African Swine Fever Virus Pandemic Strain

African swine fever virus (ASFV) causes a virulent, deadly infection in wild and domestic swine and is currently causing a pandemic covering a contiguous geographical area from Central and Eastern Europe to Asia. No commercial vaccines are available to prevent African swine fever (ASF), resulting in devastating economic losses to the swine industry. The most advanced vaccine candidates are live attenuated strains developed using a genetically modified virulent parental virus. Recently, we developed a vaccine candidate, ASFV-G-Delta I177L, by deleting the I177L gene from the genome of the highly virulent ASFV pandemic strain Georgia (ASFV-G). ASFV-G Delta I177L is safe and highly efficacious in challenge studies using parental ASFV-G. Large-scale production of ASFV-G-Delta I177L has been limited because it can replicate efficiently only in primary swine macrophages. Here, we present the development of an ASFV-G-Delta I177L derivative strain, ASFV-G-Delta I177L/ALVR, that replicates efficiently in a stable porcine cell line. In challenge studies, ASFV-G-Delta I177L/ALVR maintained the same level of attenuation, immunogenic characteristics, and protective efficacy as ASFV-G-Delta I177L. ASFV-G-Delta I177L/ALVR is the first rationally designed ASF vaccine candidate that can be used for large-scale commercial vaccine manufacture. IMPORTANCE African swine fever is currently causing a pandemic resulting in devastating losses to the swine industry. Experimental ASF vaccines rely on the production of vaccine in primary swine macrophages, which are difficult to use for the production of a vaccine on a commercial level. Here, we report a vaccine for ASFV with a deletion in the left variable region (LVR). This deletion allows for growth in stable cell cultures while maintaining the potency and efficacy of the parental vaccine strain. This discovery will allow for the production of an ASF vaccine on a commercial scale.

Automated summary

African swine fever virus (ASFV) is causing devastating losses to the swine industry, but there is currently no commercial vaccine available. A newly developed ASF vaccine can replicate efficiently in stable porcine cell cultures while maintaining protective efficacy.