E2 is one of the three envelope glycoproteins of
Classical Swine Fever Virus (CSFV). E2 is involved in several functions including
virus attachment and entry to target cells, production of antibodies, induction of protective immune response in swine, and
virulence. Seven putative
glycosylation sites in E2 were modified by
site directed mutagenesis of a CSFV Brescia infectious clone (BICv). A panel of
virus mutants was obtained and used to investigate whether the removal of putative
glycosylation sites in the E2
glycoprotein would affect viral
virulence /
pathogenesis in swine. We observed that rescue of viable
virus was completely impaired by removal of all putative
glycosylation sites in E2, but restored when
mutation N185A reverted to wild-type
asparagine produced viable virus that was attenuated in swine. Single mutations of each of the E2 glycosylation sites showed that
amino acid N116 (N1v virus) was responsible for BICv attenuation. N1v efficiently protected swine from challenge with virulent BICv at 3 and 28 days post-infection suggesting that glycosylation of E2 could be modified for development of CSF live-attenuated vaccines. Additionally, a new developed virus, contained deletions of putative glycosylation sites N1 in E2 and N1 in E0 (6b), called N1E0 / 2v, induce a
solid protection against the challenge at 3 and 28 days post-
inoculation.