Deletion of B125R increases protection induced by a genotype II African swine fever vaccine candidate.

A modified live attenuated African swine fever genotype II virus, GΔDKE-CmutQ96R/K108D, with deletions of three genes, DP148R, EP153R, and K145R and expressing a mutated CD2v protein with a non-haemadsorbing phenotype, was further modified by first removing two reporter gene cassettes expressing fluorescent proteins. The B125R gene was then deleted and one reporter cassette was reinserted as a marker. Groups of pigs were immunised with this virus using a range of doses from 100 to 10,000 infectious particles. One pig immunised with the lowest dose reached a moderate severity humane endpoint. The other pigs showed mild or no clinical signs. Low levels of the virus used for immunisation were detected post-immunisation. After challenge with virulent virus, all pigs were protected, and few clinical signs were observed. Low levels of replication of the challenge virus were detected in seven from the twenty-three challenged pigs and no virus in the remaining pigs.