Role of African swine fever virus (ASFV) proteins EP153R and EP402R in reducing viral persistence and virulence from attenuated BeninΔDP148R

The limited knowledge on the role of many of the approximately 170 proteins encoded by African swine fever virus restricts progress towards vaccine development. In this study we investigated the effect of deleting combinations of different genes from a previously attenuated virus, Benin{Delta}DP148R on: virus replication in macrophages, virus persistence and clinical signs post immunization, and induction of protection against challenge. Deletion of either EP402R or EP153R genes individually or in combination from Benin{Delta}DP148R did not reduce virus replication in vitro. However, deletion of EP402R dramatically reduced viral persistence in vivo, whilst maintaining high levels of protection against challenge. The additional deletion of EP153R (Benin{Delta}DP148R{Delta}EP153R{Delta}EP402R) further attenuated the virus and no viremia or clinical signs were observed post immunization. This was associated with decreased protection and detection of moderate levels of challenge virus in blood. Interestingly, the deletion of EP153R alone from Benin{Delta}DP148R did not result in further virus attenuation and a slight increase in virus genome copies in blood was observed at different times post immunization when compared with Benin{Delta}DP148R. These results show that EP402R and EP153R have a synergistic role in promoting viremia, however EP153R alone does not seem to have a major impact on virus levels in blood.