African swine fever virus gene j13L encodes a 25-27 kDa virion protein with variable numbers of amino acid repeats

Abstract

The African swine fever virus (ASFV)j 13L gene encodes a 177 amino acid protein (19.0 kDa) with a putative transmembrane domain between residues 32 and 52. There is a potential signal peptide cleavage site at residue 54 and several possible motifs for phosphorylation and myristylation. Rabbit antisera raised against a synthetic peptide from the C terminus of the j 13L ORF identified proteins of 25-27 kDa in cells infected with a recombinant vaccinia virus expressing the j 13L ORF, in ASFV-infected cells and in purified extracellular ASF virions. In ASFV-infected cells the jl3L protein was expressed late during infection and exhibited size variation (25-27 kDa) between the different ASFV strains. Nucleotide sequence analysis of the gene in these strains showed that these size differences were due to variation in the number and sequence of tandemly repeated amino acid repeats. Although ASFV-infected animals made antibodies to the jl3L protein, no protection was observed when pigs were vaccinated with a recombinant vaccinia virus expressing the j 13L ORF.

Expression of African swine fever virus envelope protein j13L inhibits vaccinia virus morphogenesis.

“…Immunoblotting with purified Ig against a C-terminal peptide from the j13L protein (Sun et al, 1995) identified proteins of 25, 27 and 23 kDa in cells infected with ASFV, vSJ1 and vSJ2, respectively, but not in wt VV-infected cells (Fig. 1 b).…”

“…To examine expression of the j13L protein, BSC-40 cells were infected with vSJ1, vSJ2 or wt VV, and as a control pig macrophages, prepared as described previously (Sun et al, 1995), were infected with ASFV Malawi LIL20\1. Immunoblotting with purified Ig against a C-terminal peptide from the j13L protein (Sun et al, 1995) identified proteins of 25, 27 and 23 kDa in cells infected with ASFV, vSJ1 and vSJ2, respectively, but not in wt VV-infected cells (Fig.…”

“…Cells were solubilized in Laemmli sample buffer (Laemmli, 1970) and proteins separated by SDS-PAGE on a 12 % gel. Proteins were transferred to nitrocellulose membranes which were incubated sequentially for 1 h at room temperature in PBS containing either 10 % FBS or 3 % (w\v) dried milk powder and 0n1% (v\v) Tween 20, and then in PBS and 0n1% (v\v) Tween 20 (washing buffer) containing a 1 : 1000 dilution of purified rabbit anti-j13L peptide immunoglobulin (Ig) (Sun et al, 1995). Bound antibodies were detected using goat anti-rabbit IgG-horseradish peroxidase conjugate and enhanced chemiluminescence (ECL, Amersham).…”

“…n-Mate! o et al, 1995 ;Sun et al, 1995Sun et al, , 1996. Virion membrane proteins are likely to affect virus entry, morphogenesis and egress and to elicit an immune response in infected pigs.…”

“…One virion membrane protein, called j13L (Sun et al, 1995) or p54 (Rodriguez et al, 1994, was predicted from nucleotide sequence data to be a 177 amino acid polypeptide in the ASFV strain Malawi LIL20\1 (Dixon et al, 1994) with a transmembrane domain (residues 32-52), followed by arrays of amino acid repeats which vary in number and sequence between different virus isolates (Rodriguez et al, 1994 ;Sun et al, 1995). This protein can induce antibodies that neutralize ASFV infectivity by blocking virus attachment to cells (Go!…”