Effects of ribavirin on the replication and genetic stability of porcine reproductive and respiratory syndrome virus

Table 2 Mutation frequencies of plaque-cloned, ribavirin-resistant mutants (RVRp13-P and RVRp22-P) and VR2332-p after 10 passages in MARC-145 cells

Sequenced region		VR2332-p	RVRp13-p	RVRp22-p
nsp2	Total no. of clones sequenced^a	15	15	15
	Total no. of nucleotides sequenced (3588 nt per clone)	53820	53820	53820
	Total no. of mutations	175	98	51
	Total no. of nucleotide deletions in sequenced length	63	0	6
	Mutation rate/10³ nt	3.25	1.82^*	0.94^**
	Total no. of amino acids sequenced (1196 aa per clone)	17940	17940	17940
	Total no. of mutations	96	70	24
	Total no. of amino acid deletions in sequenced length	21	0	2
	Mutation rate/10³ aa	5.35	3.90^*	1.33^**
ORF5	Total no. of clones sequenced	15	15	15
	Total no. of nucleotides sequenced (603 nt per clone)	9045	9045	9045
	Total no. of mutations	51	57	6
	Mutation rate/10³ nt	5.64	6.30	0.66^**
	Total no. of amino acids sequenced (201 aa per clone)	3015	3015	3015
	Total no. of mutations	32	29	4
	Mutation rate/10³ aa	10.61	9.61	1.32^**

a: The numbers of nucleotide mutations and amino acid substitutions were determined by sequencing 15 plaque-purified virus clones from cell culture fluids collected at the completion of 10 passages of each virus and comparing those samples to the original viruses not submitted to sequential cell passages.
nt: nucleotide, aa: amino acid, significance levels when comparing a drug-resistant strain with VR2332 are indicated by asterisks: *p < 0.05, **p < 0.001.

ISSN: 1746-6148