Estimation of bovine leukemia virus (BLV) proviral load harbored by lymphocyte subpopulations in BLV-infected cattle at the subclinical stage of enzootic bovine leucosis using BLV-CoCoMo-qPCR

Table 1 Outline of examined BLV-infected but clinically normal cattle

Cattle	Age (years)	WBC (/μl)	Lymphocyte (/μl) (%)	Clinical stage^a	ELISA^b	Proviral load^c (Copies/1 × 10⁵cells)	Syncytium assay^d (Number/5 × 10⁶cells)
BLV-free normal cattle
N790	2.5	9,540	6,382 (66.9)	-	-	0	0
N791	2.5	8,260	4,956 (60.0)	-	-	0	0
BLV-infected cattle
1) Cattle with < 100 proviral load
N818	2.0	9,410	5,147 (54.7)	AL	+	8	0
N789	2.5	5,472	5,472 (60.2)	AL	+	26	1
2) Cattle with > 100 proviral load
N787 N733	2.5	8,730	4,487 (51.4)	AL	+	294	250
N787 N733	2.5	8,230	6,313 (68.4)	AL	+	1,614	400
N823	2.0	9,340	6,239 (66.8)	AL	+	11,112	11,000
N788	2.5	9,620	5,435 (56.5)	AL	+	18,094	17,500
O10	15.0	12,200	7,900 (64.8)	PL	+	10,689	9,086

^aThe clinical stage of BLV infection was evaluated according to the lymphocyte count (per 1 μl), the detection of atypical mononuclear cells, and the age of the animal [19]. AL, BLV-infected but clinically and hematologically normal cattle; PL, BLV-infected but clinically normal cattle showing an increase in the number of apparently normal B lymphocytes. In the latter case, three separate lymphocyte counts were performed at different times and all yielded the same results.
^bELISA was performed using an anti-BLV ELISA kit according to the manufacturer’s instructions (JNC Inc., Tokyo, Japan). +, positive for anti-BLV antibodies; -, negative for anti-BLV antibodies.
^cThe proviral load (expressed as the copy number per 10⁵ peripheral blood mononuclear cells [PBMCs]) was evaluated by BLV-CoCoMo-qPCR as previously described [19].
^dPBMCs were mixed with CC81 cells and 4 μg/ml polybrene (Sigma, St. Louis, MO) and used in the syncytium formation assay [19]. Syncytia were counted under a light microscope.

ISSN: 1746-6148