Porvac® Subunit Vaccine E2-CD154 Induces Remarkable Rapid Protection against Classical Swine Fever Virus

Abstract

Live attenuated C-strain classical swine fever vaccines provide early onset protection. These vaccines confer effective protection against the disease at 5-7 days post-vaccination. It was previously reported that intramuscular administration of the Porvac^® vaccine protects against highly virulent classical swine fever virus (CSFV) "Margarita" strain as early as seven days post-vaccination. In order to identify how rapidly protection against CSFV is conferred after a single dose of the Porvac^® subunit vaccine E2-CD154, 15 swine, vaccinated with a single dose of Porvac^®, were challenged intranasally at five, three, and one day post-vaccination with 2 × 10³ LD₅₀ of the highly pathogenic Cuban "Margarita" strain of the classical swine fever virus. Another five animals were the negative control of the experiment. The results provided clinical and virological data confirming protection at five days post-vaccination. Classical swine fever (CSF)-specific IFNγ T cell responses were detected in vaccinated animals but not detected in unvaccinated control animals. These results provided the first data that a subunit protein vaccine demonstrates clinical and viral protection at five days post-vaccination, as modified live vaccines.

Keywords: Porvac® subunit vaccine E2-CD154; T cell IFNγ responses; classical swine fever virus; early protection.

Figure 1

Clinical Score after intranasal challenge with “Margarita” strain of CSFV. (A) Group 1: Control animals, (B) Group 2: Animals immunized once five days before challenge, (C) Group 3: Animals immunized once three days before challenge, and (D): Group 4: Animals immunized once one day before challenge.

Figure 2

Rectal temperatures of animals post-challenge with “Margarita” strain of CSFV. (A) Group 1: control animals (B) Group 2: animals immunized once five days before challenge. (C) Group 3: animals immunized once three days before challenge. (D) Group 4: animals immunized once one day before challenge. The line represents the value of 40.2 °C, temperatures above which were considered as a sign of fever.

Figure 3

Neutralizing antibodies titres. Bars represent the geometric mean of the antibody titres plus the 95% confidence interval. Group 1: control animals. Group 2: animals immunized once five days before challenge. Group 3: animals immunized once three days before challenge. Group 4: animals immunized once one day before challenge. Dpc: days post-challenge. *** p < 0.001

Figure 4

IFNγ reading by ELISPOT. (A) Group 1: unvaccinated animals. (B) Group 2: animals immunized once five days before challenge. (C) Group 3: animals immunized once three days before challenge. (D) Group 4: animals immunized once one day before challenge. No statistical differences were detected between the vaccinated groups (Kruskal–Wallis test p > 0.05).