Reduced IL-2 and IL-4 mRNA expression in CD4+ T cells from bovine leukemia virus-infected cows with persistent lymphocytosis.

Abstract

The role of T-helper (Th) responses in the subclinical progression of bovine leukemia virus (BLV) infection was explored by determining the contribution of CD4+ T cells to the expression of mRNAs encoding interferon-gamma (IFN-gamma), interleukin-2 (IL-2), interleukin-4 (IL-4), and interleukin-10 (IL-10) in BLV-infected cattle. Relative levels of mRNA encoding IFN-gamma, IL-2, IL-4, and IL-10 were measured in fresh and concanavalin A (Con A) activated peripheral blood mononuclear cells (PBMCs) and purified CD4+ T cells from cows seronegative to BLV (BLV-), seropositive without persistent lymphocytosis (BLV+PL-), and seropositive with PL (BLV+PL+) using a semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) assay. The expressions of IFN-gamma, IL-2, and IL-4 mRNAs were significantly reduced in the PBMCs from BLV+PL+ cows as compared to BLV- cows. Reduced levels of IL-2 and IL-4 mRNAs were detected in fresh CD4+ T cells from BLV+PL+ cows. In contrast, Con A stimulated PBMCs and CD4+ T cells did not differ significantly in expression of IFN-gamma, IL-2, IL-10, or IL-4 mRNAs among the BLV infection groups. Using flow-sorted CD4+ T cells and semiquantitative RT-PCR the frequencies of CD4+ T cells transcribing IFN-gamma, IL-2, IL-4, and IL-10 mRNAs in the peripheral blood of BLV-, BLV+PL-, and BLV+PL+ cows were determined. There were no significant differences in the frequencies of CD4+ T cells expressing these cytokine mRNAs among animals in the different BLV infection categories. Thus, the observed differences in IL-2 and IL-4 mRNAs in CD4+ T cells were due to changes in steady-state mRNA levels expressed by individual cells and not to changes in the frequency of cells transcribing IL-2 and IL-4 mRNAs. These results demonstrate that the progression of BLV infection to PL is associated with reduced expression of classical Th1 and Th2 cytokines by CD4+ T cells, thus suggesting aberrant Th regulation in subclinically infected animals.

• Authors: Marcel Amills, Vijayakumar Ramiya, Junzo Norimine, Colleen A Olmstead, Harris A Lewin
• Journal: Virology (Virology) Vol. 304 Issue 1 Pg. 1-9 (Dec 05 2002) ISSN: 0042-6822 [Print] United States
• PMID: 12490398 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, Non-P.H.S.)

Chemical References

• Interleukin-2
• RNA, Messenger
• Interleukin-4

Topics

• Animals
• CD4-Positive T-Lymphocytes (immunology, metabolism)
• Cattle
• Enzootic Bovine Leukosis (immunology, metabolism, pathology, virology)
• Female
• Gene Expression
• Interleukin-2 (biosynthesis, genetics, immunology)
• Interleukin-4 (biosynthesis, genetics, immunology)
• Leukemia Virus, Bovine
• Lymphocytosis (immunology)
• RNA, Messenger (biosynthesis)