Spontaneously proliferating lymphocytes from bovine leukaemia virus-infected, lymphocytotic cattle are not the virus-expressing lymphocytes, as these cells are delayed in G0/G1 of the cell cycle and are spared from apoptosis

Abstract

Bovine leukaemia virus (BLV) is in the family of oncogenic retroviruses which includes human T cell leukaemia virus (HTLV). BLV infects B lymphocytes and induces

Disruption of B-cell homeostatic control mediated by the BLV-Tax oncoprotein: association with the upregulation of Bcl-2 and signaling through NF-κB

“…Tax enhances the viable B-cell numbers, increases proliferation, and alters the cell cycle phase distribution of B-cells BLV infection alters the B-cell homeostasis with both an increase in B-cell cycling and prolonged survival (Schwartz-Cornil et al, 1997;Stone et al, 2000), but it is not known whether this deregulation is associated with Tax. To further compare the B-cell growth in the presence and the absence of Tax, it was necessary to utilize both CD154 and g c -common cytokines to support the growth of the parental Clone-2 B-cells.…”

Leucose enzoótica bovina e vírus da leucemia bovina

“…Paralelamente, a proliferação de LB não infectados aumenta a população de células alvo. O conjunto destes efeitos leva o animal a apresentar o quadro de LP, sendo esta a principal via de transmissão do vírus aos animais não infectados (STONE et al, 2000).…”

“…A proliferação requereu contato direto entre as células, mas não foi associada com a expressão de proteína viral ou inibida através de anticorpos contra o BLV. Estas observações e a magnitude da resposta proliferativa sugerem que a ativação seja policlonal e envolva mecanismos diferentes da ativação antígeno-específica causada pelo BLV (STONE et al, 2000).…”

Proliferation response of lymphocytes in naturally BLV-infected cows with different phenotypes of blood leukocyte acid phosphatase

“…In other hand, blastogenic activity of unstimulated lymphocytes was significantly higher in the EBL-positive cows than in the clinically healthy animals (Table). It is postulated that the spontaneous lymphocyte proliferation in the BLV-infected PL cattle is mainly caused by B lymphocyte proliferation, which do not take part in viral antigen expression and to a lesser extent by a participation of proliferating T lymphocytes (STONE et al, 2000). The progression of BLV infection to PL is likely to be linked with a reduced expression of classical Th1 and Th2 cytokines by CD4+ T cells, which can indicate aberrant Th regulation in sublinically infected animals (AMILLS et al, 2002).…”

“…The progression of BLV infection to PL is likely to be linked with a reduced expression of classical Th1 and Th2 cytokines by CD4+ T cells, which can indicate aberrant Th regulation in sublinically infected animals (AMILLS et al, 2002). A significant role in the spontaneous lymphocyte proliferation is ascribed to interleukine 2 (IL-2), released mainly by Th1 lymphocytes (CD4+) activated by viral proteins (STONE et al, 1995(STONE et al, , 2000TRUEBLOOD et al, 1998). It is postulated that a positive feedback loop between IL-2 and viral expression and the increased T-lymphocyte expression of IL-2 in BLV-infected cows contributes to development and/or maintenance of persistent B lymphocytosis (STONE et al, 1995;TRUEBLOOD et al, 1998).…”