Table 2.

TBE virus mutants

Mutant virusEngineered mutation(s)aSpontaneous mutation(s)dInfectivity titer of stock solution (PFU/ml)Plaque morphologyf at:
NucleotidebAmino acidcNucleotidebAmino acidc37°C40°C
E(Δ309/F332Y)Δ1897–1899Δ309 Lys1967 T→A332 Phe→Tyr3 × 108 WTWT
E(K309L)1897 A→T309 Lys→LeuNone1 × 108 WTWT
1898 A→T
E(D308E)1894 G→A308 Asp→Lys1894 A→G308 Lys→Glu5 × 108 WTWT
1896 C→G
E(K311E)1903 A→G311 Lys→GluNone4 × 108 WTWT
E(D308K/K311E)1894 G→A308 Asp→LysNone3 × 108 (S, T)g S, T
1896 C→G
1903 A→G311 Lys→Glu
E(T310K)1901 C→A310 Thr→Lys1859 A→G296 Lys→Arg5 × 109 SS, T
1903 A→G311 Lys→Glu
E(T310K/K311E)1901 C→A310 Thr→LysNone5 × 108 WTWT
1903 A→G311 Lys→Glu
E(T310K)3′(Δ10847)1901 C→A310 Thr→LysNone4 × 107 SS, T
E(T310K)3′(Δ10919)1901 C→A310 Thr→LysNone2 × 108 S, TS, T
  • a E protein mutations engineered into plasmid pTNd/5′ (15); 3′-NCR deletion mutations engineered into plasmid pTNd/3′ were as described previously (16). Δ, Deletion.

  • b Numbers are according to TBE virus genomic sequence GenBank accession no. U27495.

  • c Numbers starting from the amino terminus of protein E.

  • d Mutations emerged during baby mouse brain passages [in the cases of mutants E(Δ309/F332Y) and E(D308E)] or infection of an adult mouse [in the case of E(T310K)].

  • e Deletions in the 3′-NCR as described previously (16).

  • f WT, wild-type morphology (clear plaques, diameter of 2 to 4 mm); S, small plaques (diameter of <2 mm); T, turbid plaques.

  • g Heterogeneous morphology with some clear and large plaques.