Submitted to: Virology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/21/2008
Publication Date: 3/1/2010
Citation: Gladue, D.P., Zhu, J.J., Holinka-Patterson, L.G., Fernandez-Sainz, I., Prarat, M.V., O'Donnell, V.K., Borca, M.V. 2010. Patterns of gene expression in swine macrophages infected with classical swine fever virus detected by microarray. Virology. 138(1-2):89-96. Interpretive Summary: Experimental exposure of swine to highly virulent Classical Swine Fever Virus (CSFV) strain Brescia causes an invariably fatal disease of all infected animals by 8 to 14 days post-infection. Host mechanisms involved in this severe outcome of infection have not been clearly established. To understand these mechanisms, we analyzed the pattern of gene expression in infected swine macrophages, a CSFV primary target cell, using a custom designed swine gene microarray during the infection with the Brescia strain. Changes in expression levels of 148 genes (77 up- and 71 down-regulated) during the first 48 hours post-infection were observed. Many of the genes with an altered pattern of activation are involved in development of an innate immune response or altering host DNA replication. Data gathered here suggests that the observed gene expression profile might explain immunological and pathological changes associated with virulent CSFV infections. Ethics information is valuable for other researchers to understand details of the infection.
Technical Abstract: Classical Swine Fever (CSF) is a highly contagious disease of swine that is characterized by fever, hemorrhage, leukopenia, abortion, and high mortality. The etiological agent, CSF virus (CSFV), is classified as a Pestivirus, along with Bovine Viral Diarrhea Virus (BVDV) and Border Disease Virus (BDV), within the family Flaviviridae. Like other members of the family, including the genera Flavivirus and Hepacivirus, pestiviruses are small, enveloped viruses with a positive, single-stranded RNA genome. The 12.5 kb CSFV genome consists of one large open reading frame (ORF) that encodes a 4000-amino-acid polyprotein which is co- and post-translationally processed into 11 to 12 final cleavage products using cellular and viral proteases. The ORF is flanked by untranslated regions (UTRs) that are highly conserved among virus isolates. Acute and chronic forms of CSF can be distinguished based on virulence and host range phenotype. Infection with highly virulent CSFV strains leads to morality rates approaching 100%, whereas isolates of moderate to low virulence induce a prolonged chronic disease. In addition, BVDV and BDV, etiologic agents of disease in bovine and ovine species, respectively, can also infect swine without inducing clinical disease. Despite the availability of various CSFV genomic sequences representing varying virulence phenotypes, the genetic basis of CSFV virulence in the natural host remains poorly understood. However, several viral determinants of virulence have been identified: in Npro. The Brescia strain of CSFV has a highly virulent pathotype; infected animals die within 8 to 14 days after exposure. Brescia represents the genotype 1 group of CSFV isolates that consists of virulent strains isolated before 1964 that presumably no longer are in global circulation among swine populations. Highly virulent CSFV strains, like Brescia, produce a consistent clinical outcome in swine, providing a reliable method for studying viral mechanisms underlying virulence, pathogenesis, and virus-host interactions. Here we have used the Brescia strain to study the response of swine macrophages, a CSFV primary target cell in vivo, upon infection. Cultured primary swine macrophages were infected with CSFV Brescia derived from an infectious cDNA clone, pBIC. Microarray analysis was implemented in order to characterize the in vitro macrophage response to infection by virulent CSFV Brescia by assessing changes in patterns of gene expression in peripheral blood-derived swine macrophages. Our results describe changes in levels of expression of 148 genes during the first 48 hours following the infection. The observed gene expression profile might explain the immunological and pathological changes characteristically associated with infection of pigs with CSFV Brescia.