THE CLASSICAL SWINE FEVER VIRUS LPC VACCINE AND E2 GLYCOPROTEINS PROTECT FROM CHALLENGE WITH GENOTYPICALLY HOMOLOGOUS VIRUSES

Abstract

Classical swine fever (CSF) is an acute viral disease that has high contagion and high mortality in domestic pigs and wild boars. In Taiwan, classical swine fever virus (CSFV) of subgroup 3.4 (Native strain; 94.4/IL/94/TWN) was almost 100% isolated before 1993. In 1994, Subgroup 2.1 (Exotic strain; TD/96/TWN) was first detected, and since a severe outbreak in 1995, it has dominated the field. There is a concern that the Lapinized Philippines Coronel (LPC) of genotype 1.1, widely used in Taiwan, may not completely protect animals from the currently prevalent genotype 2.1 CSFV in the field. In this study, pigs were immunized by LPC vaccine and E2 glycoprotein expressed from cloned genes of LPC, TD/96, and 94.4 viruses, respectively before challenge with genotypically homologous viruses. The viral distributions and intensity after challenge were analyzed by using reverse transcription polymerase chain reaction (RT-PCR) and immunohistochemistry (IHC). Both LPC vaccine and E2 glycoproteins provided significant protection potency from CSFV. However, the LPC vaccine antigen was noted, although to a significantly milder degree (p < 0.05) than in the positive control, in lymphoid follicles of the lymph node and in various organs after the vaccinated animals were challenged with virulent ALD strain. Tissues from all experimental groups were tested negative by RT-PCR. In conclusion, the LPC attenuated virus and E2 glycoproteins offer protection against their genotypically homologous viruses. A change of vaccine seed to genotype 2.1 may be an option to combat the currently prevalent genotype 2.1 CSFVs in the field.