Evaluation of classical swine fever E2 (CSF-E2) subunit vaccine efficacy in the prevention of virus transmission and impact of maternal derived antibody interference in field farm applications

Table 1 Pig groups and experiment schedules in the study

Trials	Categories	Groups	Animal number	Vaccines^a	Vaccination program	Challenge^b/booster^c	Serum sampling
I	SPF	A	4	CSF-E2	6 and 9 weeks old	CSFV ALD strain	0, 4, 7, 12, 17, 25 DPC
		B	4	–	–	Cohabitation at 4 DPC	4, 7, 12, 17 DPC
		C	2	Placebo	6 and 9 weeks old	CSFV ALD strain	0, 4, 7 DPC
II	Sow	D	25	CSF-E2	−5 and −3 weeks before parturition	–	3 days after parturition
	Sow	E	35	LPC	Once before insemination	–	3 days after parturition
	Piglet	F^d	20	–	–	–	1, 4, 8,12 weeks old
	Piglet	G^e	20	–	–	–	1, 4, 8,12 weeks old
III	Piglet^d	H	6	CSF-E2	3 and 6 weeks old	LPC vaccine	6, 9, 12, 16, 20 weeks old
		I	6	LPC	3 and 6 weeks old	LPC vaccine	6, 9, 12, 16, 20 weeks old
		J	6	Placebo	3 and 6 weeks old	LPC vaccine	6, 9, 12, 16, 20 weeks old
IV	Piglet^d	K	10	CSF-E2	3 weeks old	–	4, 8, 12, 16, 20 weeks old
		L	10	LPC	12 and 15 weeks old	–	4, 8, 12, 16, 20 weeks old
		M	10	Placebo	3 weeks old	–	4, 8, 12, 16, 20 weeks old

^aCSF-E2 vaccine, baculovirus-expressed CSF-E2 subunit protein emulsified with water-in-oil (W/O) adjuvant; LPC vaccine, live attenuated CSF vaccine; Placebo, 0.9% saline emulsified with the W/O adjuvant
^bGroups A and C were challenged with 1 × 10⁵ TCID₅₀ CSFV (ALD strain) intramuscularly on the neck behind the ear at 12 weeks old
^cGroup H-J pigs were immunized with one dose of LPC vaccine at 16 weeks old as a booster
^dOffspring from 5 sows in group D with CSF-specific antibody blocking percentage over 85% were assigned to group F (4 piglets per litter)
^eOffspring from 5 sows in group E with CSF-specific antibody blocking percentage over 85% were assigned to group G (4 piglets per litter)

ISSN: 2055-5660