Live Attenuated Classical Swine Fever Vaccine Based in Genetic Manipulation of a Putative Fusion Peptide Area in the Virus Structural Glycoprotein E2

Abstract

The role of a specific E2 region, 869CKWGGNWTCV878, containing a putative fusion peptide (FP) sequence was evaluated. FPs critically contribute to the interaction between proteins and the membrane system of the host cell. Reverse genetics utilizing a full-length infectious clone of the highly virulent CSFV strain Brescia (BICv) was used to evaluate how amino acid substitutions within this region of E2 may affect replication of BICv in cell cultures and affect virus virulence in swine. A recombinant CSFV (FPi.c) containing mutations in three amino acid residues within the E2 protein area comprised CSFV amino acid residues 869-878 was constructed: W871T, W875D, and V878T. Interestingly, mutated virus FPi.c was completely attenuated when inoculated intranasally at a dose of 105 TCID50 in swine. Importantly, animals infected with FPi.c virus were protected against the virulent challenge with Brescia virus at 3 and 28 days after vaccination. Protection was evidenced by absence of clinical signs related with CSF as well as the absence of viremia produced by the challenge virulent virus.

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