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Published on: July 11, 2015
Differences in cellular function and viral protein expression between IgMhigh and IgMlow B-cells in bovine leukemia
Ryoyo Ikebuchi1, Satoru Konnai1, Tomohiro Okagawa1
1Department of Disease Control, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Hokkaido, Japan.
Insights
Bovine leukemia virus (BLV) infects B-cells in cattle, leading to lymphoma. This study identifies IgM(high) B-cells as primarily BLV-expressing and IgM(low) B-cells as BLV-silencing, offering new diagnostic markers.
Area of Science:
- Veterinary Virology
- Immunology
- Oncology
Background:
- Bovine leukemia virus (BLV) causes B-cell proliferation and lymphoma in cattle.
- BLV provirus integrates into the host genome, but viral protein expression is typically low in vivo.
- BLV-infected B-cells exist in both silencing and expressing states, with unclear differentiation mechanisms.
Purpose of the Study:
- To identify markers distinguishing BLV-expressing from BLV-silencing B-cells in infected cattle.
- To characterize cellular behavior and gene expression differences between these B-cell subsets.
Main Methods:
- Analysis of B-cell markers and viral antigen expression in blood lymphocytes from BLV-infected cattle.
- Flow cytometry to quantify IgM(high) and IgM(low) B-cell populations.
- Real-time PCR and microarray analysis to assess proto-oncogene expression.
- Examination of B-cell subsets in lymphoma tissues.
Main Results:
- Proportions of IgM(high) B-cells increased in BLV-infected cattle.
- IgM(high) B-cells predominantly expressed BLV antigens, while IgM(low) B-cells did not, despite equivalent provirus loads.
- IgM(low) B-cells showed higher expression of proto-oncogenes like Maf, Jun, and Fos compared to IgM(high) B-cells.
- Lymphoma cells were exclusively IgM(low) or IgM(-).
Conclusions:
- IgM(high) B-cells are primarily BLV-expressing cells.
- IgM(low) B-cells represent a significant population of BLV-silencing cells.
- This differentiation based on IgM expression provides a potential marker for BLV-infected B-cell subsets and disease progression.
Abstract:
Bovine leukemia virus (BLV) induces abnormal B-cell proliferation and B-cell lymphoma in cattle, where the BLV provirus is integrated into the host genome. BLV-infected B-cells rarely express viral proteins in vivo, but short-term cultivation augments BLV expression in some, but not all, BLV-infected B-cells. This observation suggests that two subsets, i.e. BLV-silencing cells and BLV-expressing cells, are present among BLV-infected B-cells, although the mechanisms of viral expression have not been determined. In this study, we examined B-cell markers and viral antigen expression in B-cells from BLV-infected cattle to identify markers that may discriminate BLV-expressing cells from BLV-silencing cells. The proportions of IgM(high) B-cells were increased in blood lymphocytes from BLV-infected cattle. IgM(high) B-cells mainly expressed BLV antigens, whereas IgM(low) B-cells did not, although the provirus load was equivalent in both subsets. Several parameters were investigated in these two subsets to characterize their cellular behaviour. Real-time PCR and microarray analyses detected higher expression levels of some proto-oncogenes (e.g. Maf, Jun and Fos) in IgM(low) B-cells than those in IgM(high) B-cells. Moreover, lymphoma cells obtained from the lymph nodes of 14 BLV-infected cattle contained IgM(low) or IgM(-) B-cells but no IgM(high) B-cells. To our knowledge, this is the first study to demonstrate that IgM(high) B-cells mainly comprise BLV-expressing cells, whereas IgM(low) B-cells comprise a high proportion of BLV-silencing B-cells in BLV-infected cattle.
