Table 3.

Comparison of SBV replication efficiency. Infectious sera from Swiss SBV cases were passaged once. (A) comparison of titers and viral RNA before and after passaging in SK-6 cells of those samples that were used for complete genome sequencing and serial passaging (one titration only). (B) Comparison of replication efficiency of SK-6 versus BHK-21 cells determined by passaging five additional SBV viremic sera once. The progeny virus titer of these samples was determined by three independent titrations on both cell lines; viral RNA was quantified by three independent RT-qPCRs as well.

A
Sample no.	Infectious virus (log TCID50/mL)		Viral RNA (50 − Cq)
	Viremic serum	1 Passage in SK-6 cells	Viremic serum	1 Passage in SK-6 cells
B80/11-4*	4.9	5.6	31.5	37.4
79.4	3.9	4.7	25.9	39.5
91.1	na	na	30.6	27.3
96.1	3.5	5.7	27.5	34.5
100.3	2.5	5.1	28.4	30.5
102.2	na	na	20.6	16.8
175.2**	2.5	5.1	30.2	33.4
200.2**	3.5	4.9	27.9	30.2

B
Sample no.	Infectious virus (log TCID50/mL)						Viral RNA (50 − Cq)
	Viremic serum		1 Passage in SK-6 cells		1 Passage in BHK-21 cells		Viremic serum	1 Passage in SK-6 cells	1 Passage in BHK-21 cells
	SK-6*	BHK-21*	SK-6*	BHK-21*	SK-6*	BHK-21*
91.1	<1.0	<1.0	<1.0	<1.0	<1.0	<1.0	27.0 ± 0.5	16.7 ± 0.5	no Cq
91.2	<1.0	<1.0	<1.0	<1.0	<1.0	<1.0	26.4 ± 0.2	13.4 ± 1.2	no Cq
96.2	2.6 ± 0.2	<1.0	3.0 ± 0.2	<1.0	<1.0	<1.0	30.3 ± 0.5	29.8 ± 0.2	7.4 ± 1.4
96.3	<1.0	<1.0	<1.0	<1.0	<1.0	<1.0	30.1 ± 0.5	16.2 ± 1.6	no Cq
109.1	<1.0	<1.0	<1.0	<1.0	<1.0	<1.0	25.8 ± 0.5	no Cq	no Cq

na: No infectious virus detected.

^*Previously passaged once in KC and once in BHK-21 cells, obtained from FLI, Riems, Germany.

^**Samples taken from two individual animals from the same cattle herd.

^* Cells used for titration, mean value and standard deviation from 3 independent titrations.