Virus replicon particles expressing porcine reproductive and respiratory syndrome virus proteins elicit immune priming but do not confer protection from viremia in pigs

Table 3 Seroconversion after vaccination of pigs with VSVΔG(GP5/M) + VSVΔG(GP4/GP3/GP2) followed by PRRSV challenge.

Ab against PRRSV Ag (by ELISA)	Vaccine	ELISA	Days after PRRSV challenge infection
Ab against PRRSV Ag (by ELISA)	Vaccine	ELISA	0	2	4	7	9	11	14	24
GP5	VSVΔG(GP5/M) + VSVΔG(GP4/GP3/GP2)	Positive/total pigs	0/4	0/4	0/4	2/4	2/4	4/4	4/4	4/4
		% Competition^a (positive pigs)	0	0	0	44 ± 0.6	48 ± 4	55 ± 10	89 ± 13	89 ± 11
		Range (positive pigs)	0	0	0	43–44	45–51	45–65	72–102	77–100
	VSV*ΔG (control)	Positive/total pigs	0/3	0/3	0/3	0/3	0/3	0/3	0/3	1/3
		% Competition (positive pigs)	0	0	0	0	0	0	0	42
		Range (positive pigs)	0	0	0	0	0	0	0	42
GP3	VSVΔG(GP5/M) + VSVΔG(GP4/GP3/GP2)	Positive/total pigs	0/4	0/4	0/4	3/4	4/4	4/4	4/4	4/4
GP3	VSV*ΔG (control)	Positive/total pigs	0/3	0/3	0/3	0/3	0/3	0/3	0/3	2/3
GP4	VSVΔG(GP5/M) + VSVΔG(GP4/GP3/GP2)	Positive/total pigs	0/4	0/4	0/4	0/4	0/4	0/4	1/4	2/4
GP4	VSV*ΔG (control)	Positive/total pigs	0/3	0/3	0/3	0/3	0/3	0/3	0/3	1/3
N	VSVΔG(GP5/M) + VSVΔG(GP4/GP3/GP2)	Positive/total pigs	0/4	0/4	0/4	0/4	0/4	0/4	1/4	4/4
		S/P ratio^b (positive pigs)	0	0	0	0	0	0	0.5	1.4 ± 0.4
		Range (positive pigs)	0	0	0	0	0	0	0.5	0.9–1.9
	VSV*ΔG (control)	Positive/total pigs	0/3	0/3	0/3	0/3	1/3	1/3	1(1)/3	3/3
		S/P ratio (positive pigs)	0	0	0	0	0.5	0.7	0.8	1.4 ± 0.7
		Range (positive pigs)	0	0	0	0	0.5	0.7	0.8	0.8–2.1

^a% Competition = (negative control mean [mean of optical absorbance] − sample mean)/(negative control mean − positive control mean) × 100. The mean values are indicated with the standard deviation.
^bS/P ratio = (sample mean [mean of optical absorbance] − negative control mean)/(positive control mean − negative control mean). IDEXX X3 kit S/P ratios of >0.4 are considered positive. The mean values are indicated with the standard deviation.

ISSN: 1297-9716