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Identification of a novel virulence determinant within the E2 structural glycoprotein of classical swine fever virus
G R Risatti1, L G Holinka, C Carrillo
1Department of Pathobiology and Veterinary Science, University of Connecticut, Storrs, CT 06269, USA. guillermo.risatti@uconn.edu
Abstract:
Classical swine fever virus (CSFV) E2 glycoprotein contains a discrete epitope (TAVSPTTLR, residues 829-837 of CSFV polyprotein) recognized by monoclonal antibody (mAb) WH303, used to differentiate CSFV from related ruminant pestiviruses, Bovine Viral Diarrhea Virus (BVDV) and Border Disease Virus (BDV), that infect swine without causing disease. Progressive mutations were introduced into mAb WH303 epitope in CSFV virulent strain Brescia (BICv) to obtain the homologous amino acid sequence of BVDV strain NADL E2 (TSFNMDTLA). In vitro growth of mutants T1v (TSFSPTTLR), T2v (TSFNPTTLR), T3v (TSFNMTTLR) was similar to parental BICv, while mutants T4v (TSFNMDTLR) and T5v (TSFNMDTLA) exhibited a 10-fold decrease in virus yield and reduced plaque size. In vivo, T1v, T2v or T3v induced lethal disease, T4v induced mild and transient disease and T5v induced mild clinical signs. Protection against BICv challenge was observed at 3 and 21 days post-T5v infection. These results indicate that E2 residues TAVSPTTLR play a significant role in CSFV virulence.
Insights
Classical swine fever virus (CSFV) E2 glycoprotein mutations impact virulence. Specific E2 epitope changes in CSFV significantly affect its ability to cause disease in swine.
Area of Science:
- Veterinary Virology
- Molecular Biology
- Immunology
Background:
- Classical swine fever virus (CSFV) poses a significant threat to swine populations globally.
- The CSFV E2 glycoprotein contains a critical epitope recognized by monoclonal antibody WH303, essential for differentiating CSFV from related pestiviruses like BVDV and BDV.
- Understanding CSFV E2 glycoprotein's role in virulence is crucial for developing effective control strategies.
Purpose of the Study:
- To investigate the role of specific amino acid residues within the CSFV E2 glycoprotein epitope in viral virulence.
- To analyze the impact of mutations in the CSFV E2 epitope on viral growth in vitro and pathogenicity in vivo.
- To assess the potential of modified CSFV strains for inducing protective immunity.
Main Methods:
- Site-directed mutagenesis was used to introduce progressive mutations into the CSFV E2 glycoprotein epitope of the virulent Brescia strain (BICv).
- Mutant viruses (T1v-T5v) were generated with amino acid sequences homologous to BVDV E2.
- In vitro viral growth kinetics and plaque formation were assessed.
- In vivo pathogenicity and protection against challenge with the parental BICv strain were evaluated in animal models.
Main Results:
- Mutants T1v, T2v, and T3v showed similar in vitro growth to the parental BICv.
- Mutants T4v and T5v exhibited reduced virus yield and plaque size in vitro.
- In vivo, T1v, T2v, and T3v induced lethal disease, T4v caused mild transient disease, and T5v resulted in mild clinical signs.
- Infection with T5v conferred protection against challenge with the virulent BICv strain at 3 and 21 days post-infection.
Conclusions:
- The specific amino acid sequence TAVSPTTLR within the CSFV E2 glycoprotein epitope is critical for CSFV virulence.
- Modifications in this epitope can significantly attenuate CSFV, leading to reduced pathogenicity.
- The attenuated T5v mutant demonstrates potential as a vaccine candidate for inducing protection against CSFV.
