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

May 21, 2021 — 

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 genetically modified virulent parental virus. Recently we developed a vaccine candidate, ASFV-G-ΔI177L, by deleting the I177L gene from the genome of the highly virulent pandemic ASFV strain Georgia (ASFV-G). ASFV-G-ΔI177L is safe and highly efficacious in challenge studies using parental ASFV-G. Large-scale production of ASFV-G-ΔI177L has been limited because it can only efficiently replicate in primary swine macrophages. Here we present the development of an ASFV-G-ΔI177L derivative strain, ASFV-G-ΔI177L/ΔLVR, that efficiently replicates in a stable porcine cell line. In challenge studies, ASFV-G-ΔI177L/ΔLVR maintained the same level of attenuation, immunogenic characteristics and protective efficacy as ASFV-G-ΔI177L. ASFV-G-ΔI177L/ΔLVR is the first rationally designed ASF vaccine candidate that can be used for large-scale commercial vaccine manufacturing. Importance: African swine fever is currently causing a pandemic causing devastating losses to the swine industry. Experimental ASF vaccines rely on the production of vaccine in primary swine macrophages, which are difficult to use to produce a vaccine on a commercial level. Here we report a vaccine for ASFV with a deletion in the Left Variable Region. 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.

Borca M, Rai A, Ramirez-Medina E, Silva E, Velazquez-Salinas L, Vuono E, Pruitt S, Espinoza N, Gladue D. A cell culture-adapted vaccine virus against the current pandemic African swine fever virus strain. J Virol. May 2021. https://doi.org/10.1128/JVI.00123-21