African Swine Fever Vaccine Candidate ASFV-G-ΔI177L Produced in the Swine Macrophage-Derived Cell Line IPKM Remains Genetically Stable and Protective against Homologous Virulent Challenge

ASFV vaccine candidate ASFV-G-Delta I177L has been shown to be highly efficacious in inducing protection against challenges with the parental virus, the Georgia 2010 isolate, as well as against field strains isolated from Vietnam. ASFV-G-Delta I177L has been shown to produce protection even when used at low doses (10(2) HAD(50)) and shows no residual virulence even when administered at high doses (10(6) HAD(50)) or evaluated for a relatively long period of time (6 months). ASFV-G-Delta I177L stocks can only be massively produced in primary cell macrophages. Alternatively, its modified version (ASFV-G-Delta I177L/Delta LVR) grows in a swine-derived cell line (PIPEC), acquiring significant genomic modifications. We present here the development of ASFV-G-Delta I177L stocks in a swine macrophage cell line, IPKM, and its protective efficacy when evaluated in domestic pigs. Successive passing of ASFV-G-Delta I177L in IPKM cells produces minimal genomic changes. Interestingly, a stock of ASFV-G-Delta I177L obtained after 10 passages (ASFV-G-Delta I177Lp10) in IPKM cells showed very small genomic changes when compared with the original virus stock. ASFV-G-Delta I177Lp10 conserves similar growth kinetics in primary swine macrophage cultures than the original parental virus ASFV-G-Delta I177L. Pigs infected with 10(3) HAD(50) of ASFV-G-Delta I177Lp10 developed a strong virus-specific antibody response and were completely protected against the challenge with the parental virulent field isolate Georgia 2010. Therefore, IPKM cells could be an effective alternative for the production of ASFV vaccine stocks for those vaccine candidates exclusively growing in swine macrophages.