In vivo characterization of the superior fitness of classical swine fever virus genotype 2.1 to genotype 3.4

Hsin-Meng Liu; Ming-Chung Deng; Yu-Liang Huang; Kuo-Jung Tsai; Hui-Wen Chang; Chia-Yi Chang

doi:10.1016/j.vetmic.2023.109854

In vivo characterization of the superior fitness of classical swine fever virus genotype 2.1 to genotype 3.4

Vet Microbiol. 2023 Oct:285:109854. doi: 10.1016/j.vetmic.2023.109854. Epub 2023 Aug 22.

Authors

Hsin-Meng Liu¹, Ming-Chung Deng², Yu-Liang Huang², Kuo-Jung Tsai², Hui-Wen Chang³, Chia-Yi Chang⁴

Affiliations

¹ School of Veterinary Medicine, National Taiwan University, No. 1, Section 4, Roosevelt Rd., Taipei 106319, Taiwan, ROC; Veterinary Research Institute, Ministry of Agriculture, 376 Chung-Cheng Road, Tansui, New Taipei City 25158, Taiwan, ROC.
² Veterinary Research Institute, Ministry of Agriculture, 376 Chung-Cheng Road, Tansui, New Taipei City 25158, Taiwan, ROC.
³ School of Veterinary Medicine, National Taiwan University, No. 1, Section 4, Roosevelt Rd., Taipei 106319, Taiwan, ROC.
⁴ School of Veterinary Medicine, National Taiwan University, No. 1, Section 4, Roosevelt Rd., Taipei 106319, Taiwan, ROC. Electronic address: chiayichang@ntu.edu.tw.

PMID: 37633061
DOI: 10.1016/j.vetmic.2023.109854

Abstract

Classical swine fever (CSF), caused by classical swine fever virus (CSFV), is a highly contagious disease in pigs. In Taiwan, the emerging genotype 2.1 (G2.1) CSFV caused sporadic outbreaks in 1994 and replaced the previous G3.4 CSFV in the field. The shift of CSFV genotypes to G2 CSFV was also observed in several CSFV-affected countries. The present study aimed to explore the mechanism of the genotype shift of CSFV. Two groups of specific pathogen-free (SPF) pigs were first inoculated with either G2.1 or G3.4 CSFV (single-inoculated group) and housed together with naïve SPF pigs (cohabitating group). The results showed that peak viremia, viral loads in blood and tissues, and viral shedding of G2.1 were consistently higher than those of G3.4 CSFV in single-inoculated and cohabitating pigs. The phenomenon of superinfection exclusion (SIE), characterized by the prevention of secondary infection by a primary infection, was readily observed in CSFV single-inoculated pigs. Interestingly, coinfection of both genotypes of CSFV was observed in 3 out of 4 cohabitating pigs, while only one pig was infected with G2.1 CSFV alone. These findings suggest that the genetic shift in CSFV in the field may be in part the consequence of SIE.

Keywords: Classical swine fever virus; Cohabitation; Genotype; Superinfection exclusion; Transmission; Virus shift.