A small animal model of chronic hepatitis E infection using immunocompromised rats

Siddharth Sridhar; Shusheng Wu; Jianwen Situ; Estie Hon-Kiu Shun; Zhiyu Li; Anna Jin-Xia Zhang; Kyle Hui; Carol Ho-Yan Fong; Vincent Kwok-Man Poon; Nicholas Foo-Siong Chew; Cyril Chik-Yan Yip; Wan-Mui Chan; Jian-Piao Cai; Kwok-Yung Yuen

doi:10.1016/j.jhepr.2022.100546

A small animal model of chronic hepatitis E infection using immunocompromised rats

JHEP Rep. 2022 Aug 10;4(10):100546. doi: 10.1016/j.jhepr.2022.100546. eCollection 2022 Oct.

Authors

Siddharth Sridhar^{1

2

3}, Shusheng Wu¹, Jianwen Situ¹, Estie Hon-Kiu Shun¹, Zhiyu Li¹, Anna Jin-Xia Zhang¹, Kyle Hui¹, Carol Ho-Yan Fong¹, Vincent Kwok-Man Poon¹, Nicholas Foo-Siong Chew¹, Cyril Chik-Yan Yip¹, Wan-Mui Chan¹, Jian-Piao Cai¹, Kwok-Yung Yuen^{1

2

3

4}

Affiliations

¹ Department of Microbiology, School of Clinical Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China.
² State Key Laboratory of Emerging Infectious Diseases, The University of Hong Kong, Hong Kong, China.
³ Carol Yu Centre for Infection, The University of Hong Kong, Hong Kong, China.
⁴ The Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, The University of Hong Kong, Hong Kong, China.

Abstract

Background & aims: HEV variants such as swine genotypes within Paslahepevirus species balayani (HEV-A) and rat HEV (Rocahepevirus ratti; HEV-C1) cause chronic hepatitis E in immunocompromised individuals. There are few reliable and accessible small animal models that accurately reflect chronic HEV infection. We aimed to develop an immunocompromised rat model of chronic hepatitis E infection.

Methods: In this animal model infection study, rats were immunosuppressed with a drug combination (prednisolone, tacrolimus, and mycophenolate mofetil) commonly taken by transplant recipients. Rats were challenged with human- and rat-derived HEV-C1 strains or a human-derived HEV-A strain. Viral load, liver function, liver histology, humoural, and cellular immune responses were monitored.

Results: A high-dose (HD) immunosuppressive regimen consistently prolonged human- and rat-derived HEV-C1 infection in rats (up to 12 weeks post infection) compared with transient infections in low-dose (LD) immunosuppressant-treated and immunocompetent (IC) rats. Mean HEV-C1 viral loads in stool, serum, and liver tissue were higher in HD regimen-treated rats than in LD or IC rats (p <0.05). Alanine aminotransferase elevation was observed in chronically infected rats, which was consistent with histological hepatitis and HEV-C1 antigen expression in liver tissue. None (0/6) of the HD regimen-treated, 5/6 LD regimen-treated, and 6/6 IC rats developed antibodies to HEV-C1 in species-specific immunoblots. Reversal of immunosuppression was associated with clearance of viraemia and restoration of HEV-C1-specific humoural and cellular immune responses in HD regimen-treated rats, mimicking patterns in treated patients with chronic hepatitis E. Viral load suppression was observed with i.p. ribavirin treatment. HD regimen-treated rats remained unsusceptible to HEV-A infection.

Conclusions: We developed a scalable immunosuppressed rat model of chronic hepatitis E that closely mimics this infection phenotype in transplant recipients.

Lay summary: Convenient small animal models are required for the study of chronic hepatitis E in humans. We developed an animal model of chronic hepatitis E by suppressing immune responses of rats with drugs commonly taken by humans as organ transplant rejection prophylaxis. This model closely mimicked features of chronic hepatitis E in humans.

Keywords: ALT, alanine aminotransferase; HD, high dose; HEV; HEV, hepatitis E virus; HEV-A, Paslahepevirus balayani; HEV-C1; HEV-C1, Rocahepevirus ratti genotype 1; IC, immunocompetent; IFN-γ, interferon-γ; Immunosuppression; LD, low dose; MMF, mycophenolate mofetil; Orthohepevirus C; PBS, phosphate buffered saline; Rat hepatitis E; Ribavirin; Rocahepevirus ratti; VTM, virus transport medium; dpi, days post infection; rRT-PCR, real-time reverse-transcription PCR.