First study on in vitro antiviral and virucidal effects of flavonoids against feline infectious peritonitis virus at the early stage of infection

Chanittha Triratapiban; Varanya Lueangaramkul; Nantawan Phecharat; Achiraya Pantanam; Porntippa Lekcharoensuk; Sirin Theerawatanasirikul

doi:10.14202/vetworld.2023.618-630

First study on in vitro antiviral and virucidal effects of flavonoids against feline infectious peritonitis virus at the early stage of infection

Vet World. 2023 Mar;16(3):618-630. doi: 10.14202/vetworld.2023.618-630. Epub 2023 Mar 26.

Authors

Chanittha Triratapiban¹, Varanya Lueangaramkul¹, Nantawan Phecharat¹, Achiraya Pantanam¹, Porntippa Lekcharoensuk^{1

2}, Sirin Theerawatanasirikul³

Affiliations

¹ Department of Microbiology and Immunology, Faculty of Veterinary Medicine, Kasetsart University, Bangkok 10900, Thailand.
² Center for Advanced Studies in Agriculture and Food, Kasetsart University Institute for Advanced Studies, Kasetsart University, Bangkok 10900, Thailand.
³ Department of Anatomy, Faculty of Veterinary Medicine, Kasetsart University, Bangkok 10900, Thailand.

Abstract

Background and aim: Feline infectious peritonitis (FIP), one of the most important infectious diseases in cats is caused by FIP virus (FIPV), a mutated variant of feline coronavirus. Feline infectious peritonitis has a negative impact on feline health, with extremely high mortality in clinical FIP-infected cats, particularly young cats. There are no approved drugs for FIP treatment, and therapeutic possibilities for FIP treatment are limited. This study aimed to utilize nature-derived bioactive flavonoids with antiviral properties to inhibit FIPV infection in Crandell-Rees feline kidney (CRFK) cells.

Materials and methods: The cytotoxicity of 16 flavonoids was evaluated on CRFK cells using a colorimetric method (MTS) assay. Viral kinetics of FIPV at 50 tissue culture infectious dose (TCID₅₀)/well was determined during the first 24-h post-infection (HPI). Antiviral activity was evaluated based on the replication steps of the virus life cycle, including pre-compound, attachment, penetration, post-viral entry, and virucidal assays. The antiviral efficacy of flavonoids against FIPV was determined based on positive FIPV-infected cells with the immunoperoxidase monolayer assay and viral load quantification using reverse transcription-quantitative polymerase chain reaction.

Results: Two flavonoids, namely, isoginkgetin and luteolin, inhibited FIPV replication during post-viral entry in a dose-dependent manner, with 50% maximal effective concentrations = 4.77 ± 0.09 and 36.28 ± 0.03 μM, respectively. Based on viral kinetics, both flavonoids could inhibit FIPV replication at the early stage of infection at 0-6-HPI for isoginkgetin and 2-6-HPI for luteolin using a time-of-addition assay. Isoginkgetin exerted a direct virucidal effect that reduced the viral titers by 2 and 1.89 log₁₀ TCID₅₀/mL at 60 and 120 min, respectively.

Conclusion: Isoginkgetin interfered with FIPV replication during both post-viral infection and virucidal experiments on CRFK cells, whereas luteolin inhibited the virus after infection. These results demonstrate the potential of herbal medicine for treating FIP.

Keywords: antiviral; feline coronavirus; feline infectious peritonitis virus; flavonoids; infectious disease.