Characterization of the African swine fever virion protein j18L

Institute for Animal Health, Pirbright Laboratory, Ash Road, Pirbright, Woking, Surrey GU24 0NF, UK The African swine fever virus (ASFV) open reading frame (ORF) that is named j18L in the Malawi (LIL20/1) isolate and E199L in the Ba71V isolate encodes a cysteine rich protein of 195 amino acids with a predicted molecular mass of 21·7 kDa and a hydrophobic domain near the C terminus. There are several possible motifs for glycosylation, phosphorylation and myristoylation. Rabbit antisera and monoclonal antibodies raised against a recombinant ASFV j18L protein expressed as a fusion protein with glutathione S -transferase (GST) identified proteins of 19·0–20 kDa in cells infected with different ASFV strains and with a recombinant vaccinia virus expressing j18L. The monoclonal antibodies detected a protein of 20·0 kDa whereas rabbit antisera detected two proteins with relative molecular masses of 15·0 and 20·0 kDa in purified extracellular ASF virions. In ASFV-infected cells, the j18L protein was expressed late post-infection and was localized mainly in the viral factories. * Author for correspondence. Fax +44 1483 232448. e-mail Linda.Dixon@BBSRC.AC.UK Received 13 November 1995; accepted 15 January 1996.