Cell culture propagation modifies the African swine fever virus replication phenotype in macrophages and generates viral subpopulations differing in protein p54.

We have detected 86 African swine fever (ASF) virus-induced proteins in infected pig macrophages by two-dimensional electrophoresis. No differences among protein patterns of wild-type viruses could be observed by this methodology. However, during cell culture adaptation and propagation we have characterized changes in the molecular weight of the ASF virus specified protein p54, which show direct correlation with both size and number of viral subpopulation variants generated during cell culture propagation. Passages in culture appear to select for viral subpopulations that specify p54 proteins with higher molecular weights than the wild-type virus. The virus propagation in cell culture also affected its replication phenotype in pig macrophages decreasing the viral titers in these cells between passage 44 and 81. Nevertheless, the changes observed in p54 did not imply differences in biological properties, such as infectivity, virulence or host cell range among viral clones isolated, each one specifying for only one p54 form with different molecular weight. This protein becomes then a valuable quantification marker to follow evolution and generation of ASF virus diversity in vitro.