African Swine Fever Virus MGF-110-9L-deficient Mutant Has Attenuated Virulence in Pigs

African swine fever virus (ASFV) is the etiological agent of African swine fever (ASF), an often lethal disease in domestic and wild pigs. ASF represents a major threat to the swine industry worldwide. Currently, no commercial vaccine is available because of the complexity of ASFV or biosecurity concerns. Live attenuated viruses that are naturally isolated or genetically manipulated have demonstrated reliable protection against homologous ASFV strain challenge. In the present study, a mutant ASFV strain with the deletion of ASFV MGF-110-9L (ASFV-Delta 9L) was generated from a highly virulent ASFV CN/GS/2018 parental strain, a genotype II ASFV. Relative to the parental ASFV isolate, deletion of the MGF-110-9L gene significantly decreased the ability of ASFV-Delta 9L to replicate in vitro in primary swine macrophage cell cultures. The majority of animals inoculated intramuscularly with a low dose of ASFV-Delta 9L (10 HAD(50)) remained clinically normal during the 21-day observational period. Three of five ASFV-Delta 9L-infected animals displayed low viremia titers and low virus shedding and developed a strong virus-specific antibody response, indicating partial attenuation of the ASFV-Delta 9L strain in pigs. The findings imply the potential usefulness of the ASFV-Delta 9L strain for further development of ASF control measures.

Automated summary

This study generated a mutant ASFV strain, ASFV-Delta 9L, with partial attenuation in pigs by deleting the ASFV MGF-110-9L gene. The findings suggest the potential usefulness of ASFV-Delta 9L strain for further development of ASF control measures.