Mutation of E1 glycoprotein of classical swine fever virus affects viral virulence in swine.
Transposon linker insertion mutagenesis of a full-length infectious clone (IC) (pBIC) of the pathogenic classical swine fever virus (CSFV) strain Brescia was used to identify genetic determinants of CSFV virulence and host range. Here, we characterize a virus mutant, RB-C22v, possessing a 19-residue insertion at the carboxyl terminus of E1 glycoprotein. Although RB-C22v exhibited normal growth characteristics in primary porcine macrophage cell cultures, the major target cell of CSFV in vivo, it was markedly attenuated in swine. All RB-C22v-infected pigs survived infection remaining clinically normal in contrast to the 100% mortality observed for BICv-infected animals. Comparative pathogenesis studies demonstrated a delay in RB-C22v spread to, and decreased replication in the tonsils, a 10(2) to 10(7) log10 reduction in virus titers in lymphoid tissues and blood, and an overall delay in generalization of infection relative to BICv. Notably, RB-C22v-infected animals were protected from clinical disease when challenged with pathogenic BICv at 3, 5, 7, and 21 days post-RB-C22v inoculation. Viremia, viral replication in tissues, and oronasal shedding were reduced in animals challenged at 7 and 21 DPI. Notably BICv-specific RNA was not detected in tonsils of challenged animals. These results indicate that a carboxyl-terminal domain of E1 glycoprotein affects virulence of CSFV in swine, and they demonstrate that mutation of this domain provides the basis for a rationally designed and efficacious live-attenuated CSF vaccine.
Risatti
G R
GR
Plum Island Animal Disease Center, USDA/ARS/NAA, P.O. Box 848, Greenport, NY 11944-0848, USA. Guillermo.Risatti@uconn.edu
Holinka
L G
LG
Lu
Z
Z
Kutish
G F
GF
Tulman
E R
ER
French
R A
RA
Sur
J H
JH
Rock
D L
DL
Borca
M V
MV
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001769:Blood / Q000821:virology; D002460:Cell Line; D006691:Classical Swine Fever / Q000517:prevention & control / Q000821:virology; D006692:Classical Swine Fever Virus / Q000235:genetics* / Q000302:isolation & purification / Q000472:pathogenicity*; D004195:Disease Models, Animal; D007958:Leukocyte Count; D018655:Lymphocyte Count; D008221:Lymphoid Tissue / Q000821:virology; D008264:Macrophages / Q000821:virology; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D014066:Palatine Tonsil / Q000821:virology; D010976:Platelet Count; D012367:RNA, Viral / Q000032:analysis; D016019:Survival Analysis; D013552:Swine; D014613:Vaccines, Attenuated; D010948:Viral Plaque Assay; D015678:Viral Structural Proteins / Q000032:analysis / Q000235:genetics* / Q000302:isolation & purification / Q000502:physiology*; D014765:Viral Vaccines; D014774:Virulence / Q000235:genetics*; D014779:Virus Replication; D017201:Virus Shedding
D012367:RNA, Viral; D014613:Vaccines, Attenuated; D015678:Viral Structural Proteins; D014765:Viral Vaccines; C107842:protein E1, Classical swine fever virus