Experimental infection of calves with bovine leukemia virus (BLV): an applicable model of a retroviral infection

An experimental model of chronic infection with bovine leukemia virus (BLV) was established in young calves within a relatively short time. In the ser a of all infected calves, precipitating antibodies were detected within 5 w eeks after infection but upon disease progression pattern of cellular profi les varied. Three calves exhibited transient lymphocytosis 3-5 weeks after infection two became persistent lymphocytotic (PL+) by that time and one st ayed non-lymphocytotic (PL-) for 11 weeks and became PL+ after 4.5 months. Eventually all infected calves became PL+ by the end of the experiment, 6-1 2 months after infection. Increase of total counts of peripheral blood mono nuclear cells (PBMC) related to polyclonal expansion of B-cells. The latter was assessed in all infected calves where the expansion of CDS-bearing cel ls (B(+)CD5(+)) correlated with increase or decrease of total PBMC counts. Other cell populations such as CD4 and CD8 were also affected. Percentages decreased by 5 weeks after experimental infection to about half their origi nal values though actual cell numbers stayed relatively stable. The experim ental model we established compared well with field cases of naturally BLV- infected cattle and thus permitted the investigation of the disease at earl y stages of infection. (C) 1999 Elsevier Science B.V. All rights reserved.