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Aberrant expression of immunoglobulin mRNA in bovine leukemia virus-infected cattle
1Department of Animal Sciences, University of Illinois at Urbana-Champaign 61801, USA.
Insights
Bovine leukemia virus (BLV) does not alter immune gene expression in infected cows. Instead, increased Ig-mu and decreased Ig-lambda mRNA in persistent lymphocytosis (PL) suggest a B cell differentiation state.
Area of Science:
- Veterinary Virology
- Immunology
- Molecular Biology
Background:
- Bovine leukemia virus (BLV) is a retrovirus causing persistent lymphocytosis (PL) in cattle.
- Understanding BLV's impact on host gene expression is crucial for managing infections and immune responses.
Purpose of the Study:
- To investigate if BLV integration and expression influence host immune response and cell proliferation genes.
- To determine the relationship between BLV infection, persistent lymphocytosis, and specific gene expression patterns in cattle.
Main Methods:
- Analysis of Ig-mu and Ig-lambda mRNA levels in mlgM+ cells from BLV-infected cows with and without persistent lymphocytosis.
- Assessment of Major Histocompatibility Complex (Mhc) Class I and Class II gene expression.
- Evaluation of c-fos mRNA expression in a BLV-infected cell line and peripheral blood B cells.
Main Results:
- Cows with persistent lymphocytosis showed increased Ig-mu mRNA and decreased Ig-lambda mRNA, irrespective of BLV status.
- BLV infection status did not correlate with Mhc Class I or Class II gene expression.
- BLV induction in mlgM+ cells did not significantly alter Mhc or Ig mRNA levels.
- c-fos expression was higher in a BLV-infected cell line but similar in peripheral blood B cells from infected and non-infected cows.
Conclusions:
- BLV early and late proteins do not affect immunoglobulin (Ig) or Mhc mRNA levels.
- Constitutive upregulation of Ig-mu and downregulation of Ig-lambda in mlgM+ cells from PL cows indicates a B cell differentiation state.
- The observed changes in B cells from PL cows are likely due to differentiation, not direct BLV trans-activation.
Abstract:
Our objective was to determine whether bovine leukemia virus (BLV) integration and expression affect the expression of host genes that function in immune responses and cell proliferation. Freshly isolated mlgM+ cells obtained from BLV-infected cows with persistent lymphocytosis (PL) expressed increased Ig-mu mRNA and decreased mRNA for Ig-lambda relative to infected and uninfected animals that had normal peripheral lymphocyte counts. In contrast, there was no correlation between BLV-infection status and expression of major histocompatibility complex (Mhc) Class I or Class II genes. The induction of BLV expression in mlgM+ cells from animals with PL did not affect significantly the levels of Mhc Class I, Class II, Ig-mu or Ig-lambda mRNA. Phorbol ester-induced c-fos mRNA expression was greater in the BLV-infected cell line BL3 degrees than the uninfected parental cell line BL3 degrees. However, the level of c-fos expression did not appear different compared with its induction in peripheral blood B cells from seronegative animals and animals with PL. We conclude that the BLV early and late phase proteins have no effect on Ig or Mhc mRNA levels, but that freshly isolated mlgM+ cells from PL animals constitutively express increased Ig-mu and decreased Ig-lambda mRNA. These data suggest that the increase in Ig-mu and mlgM on B cells from PL cows is related to a differentiation state rather than trans-activation by BLV.