The cellular immune recognition of proteins expressed by an African swine fever virus random genomic library

The cellular immune recognition of peptides expressed by an African swine fever virus (ASFV) random genomic library has been studied. DNA from the Malawi (LIL20/1) ASFV isolate was randomly sheared by sonication, cloned into a plasmid vector downstream of a bacteriophage T7 promoter, and 72 recombinant plasmids were arbitrarily selected. These plasmids were transiently expressed following transfection into major histocompatibility complex (MHC) class I + class II − matched pig skin cells, which had been co-infected with vTF7-3, a recombinant vaccinia virus encoding bacteriophage T7 RNA polymerase. Such cells served as antigen presenting cells and each recombinant plasmid was screened in a proliferation assay for recognition by CD8 + lymphocytes from inbred pigs previously exposed to ASFV. This assay was demonstrated to measure CD8 + T cell proliferation, as predicted by the phenotype of the antigen presenting cell. Of the 72 randomly selected clones, 14 were reproducibly recognised by immune pig lymphocytes and 10 corresponded to non-overlapping and distinct nucleic acid sequences. This high frequency of ASFV encoded antigenic epitopes supports the concept that cellular immunity to the virus may play an important role in resistance to ASF.