Morphologic and functional changes in bovine monocytes infected in vitro with the bovine leukaemia virus

Experiments on the host cell spectrum of bovine leukaemia virus (BLV), a re trovirus closely related to the human T-cell leukaemia virus (HTLV), have y ielded conflicting data. Currently, BLV is known to infect B cells, whereas its ability to infect other cell types, e.g. monocytes/macrophages, is dou btful. As monocytes/macrophages may have profound effects on the diversity of the T-cell response, we studied the possibility of in vitro infection, u sing bovine monocytes and SV40-transformed bovine macrophages. Proviral DNA was detected by nested polymerase chain reaction (PCR) from day 1 until th e end of the experiments at either day 5 or day 80, depending on the quanti ty of virus used for infection. In addition, the infection was associated w ith morphological changes in infected cells as revealed by electron microsc opy. The in vitro infection did not significantly change either the express ion of surface antigens (CD11b, CD32, and major histocompatibility complex (MHC) class II) or the amounts of cytokine transcripts (interleukin (IL)-1 beta, tumour necrosis factor (TNF)-alpha, IL-6 and IL-12p4O) with or withou t lipopolysaccharide (LPS) stimulation. The data suggest that BLV can infec t monocytes, but the infection does not seem to influence the function or t he phenotype of these cells. Infected monocytes may, however, play a role a s a viral reservoir in vivo.