Submitted to: Virus Research
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/13/2008
Publication Date: 8/1/2008
Citation: Neill, J.D., Ridpath, J.F. 2008. Increase in proto-oncogene mRNA transcript levels in bovine lymphoid cells infected with a cytopathic type 2 bovine viral diarrhea virus. Virus Research. 135(2):326-331. Interpretive Summary: Bovine viral diarrhea virus (BVDV) is a ubiquitous virus of ruminants. Infection by these viruses can have different outcomes depending on the circumstances. If a pregnant cow is infected between 75 and 150 day of gestation, the calf may be born infected with the virus and spread it for the rest of its life. If a cow is infected, or in some cases just following vaccination with a live vaccine, the cow may have an impaired immune system for short period of time that may allow other pathogens to infect the cow or make the second infection worse. How BVDV is able to do these things is unknown. To begin to understand what is happening, we have use serial analysis of gene expression (SAGE) to look at the gene expression patterns in normal and BVDV-infected cells to see how these patterns are affected. We found changes in the amount of proteins that affect the way in which the cell is able to grow and perhaps survive the viral infection. These changes may be a result of the virus protecting its genomic RNA from the cell's natural protective mechanisms. This may indicate a way that the virus is able to establish a chronic infection. These findings will be the basis of further studies to see what role these changes play in disease caused by BVDV.
Technical Abstract: Infection of susceptible animals with bovine viral diarrhea viruses (BVDV) can result in an array of disease symptoms that are dependent on the strain of infecting virus and the physiological status of the host. Cytopathic BVDV kill cells outright while noncytopathic strains can readily establish persistent infections. The molecular mechanisms behind these affects are unknown. To gain a better understanding of the mechanisms of disease, serial analysis of gene expression (SAGE), a powerful method for global gene expression analysis, was employed to examine gene expression changes in BL3 cells, a bovine B-cell lymphosarcoma cell line, following infection with BVDV2. SAGE libraries were constructed from mRNA derived from BL3 cells that were noninfected or infected with the cytopathic BVDV2 strain 296c. Analysis of the SAGE data showed the expression of many of the genes that are characteristic of B cells and integral to their function. Comparison of the SAGE databases also revealed a number of genes that were differentially expressed. Of particular interest was the increased numbers of transcripts encoding proto-oncogenes (c-fos, c-jun, junB, junD) in 296c-infected cells, all of which are constituents of the AP-1 transcriptional activation complex. Real-time RT-PCR confirmed these results and indicated that the actual increase was larger than that indicated by SAGE. Interestingly, there was no corresponding increase in protein levels, but rather a significant decrease of c-jun and junB protein levels in the infected BL3 cells. Rather than an increase in transcription of these genes, it appeared that the transcripts encoding these proto-oncogenes accumulate in the BVDV2-infected cells.