Experimental infection of hepatitis E virus induces pancreatic necroptosis in miniature pigs

Abstract

infection by hepatitis e virus (HeV) via the oral route causes acute hepatitis. extra-hepatic manifestations of HeV infection may stem from various causes; however, its distribution in organs such as the liver, as well as the mechanisms underlying HeV-induced cell injury, remain unclear. the objective of this study was to determine the chronological distribution of HeV in various tissues of HeV-challenged miniature pigs and to investigate the mechanisms underlying HeV-induced cell death in the pancreas and liver. Virological and serological analyses were performed on blood and faecal samples. Histopathology of the liver and extra-hepatic tissues was analysed. cell death pathways and immune cell characterisation in inflammatory lesions were analysed using immunohistochemistry. The liver and pancreas displayed inflammation and cellular injury, and a large amount of HEV was observed in the lesions. The liver was infiltrated by T and natural killer cells. HEV was identified in all organs except the heart, and was associated with immune cells. Although the liver and the pancreas strongly expressed TNF-α and TRAIL, TUNEL assay results were negative. RIP3 and pMLKL were expressed in the pancreas. RIP3, but not pMLKL, was expressed in the liver. Pancreatitis induced in HeV-infected miniature pigs is associated with necroptosis. Worldwide, 14 million symptomatic infections, 5,200 stillbirths, and 300,000 deaths are attributed to hepatitis E virus (HEV) according to the World Health Organisation 1. While HEV infection is mostly associated with large epidemics in developing countries, autochthonous sporadic cases are on the rise in industrialised countries 2. In the UK, hepatitis E cases have been increasing since 2009, with an estimated annual infection rate of 200,000, which is largely attributed to the consumption of pork products 3,4. Clinical symptoms of HEV are mainly associated with acute hepatitis, fulminant hepatic failure, or chronic hepatitis in immunocompromised patients and the elderly. HEV genotype 1 and 2 infection is associated with high mortality rates (up to 25%) in pregnant women 5,6. Extra-hepatic lesions, including acute pancreatitis, renal failure, neurological diseases, haematological diseases, and the Guillain-Barre syndrome, are linked with HEV infection, cases of which are increasing. However, its pathogenesis is not well understood 7. Although several in vivo and in vitro models have been proposed for the purpose of cultivating HEV or mimicking HEV infection in laboratory animals, including rabbits, mice and rats, such in vivo models have not been successful in demonstrating the clinical symptoms of HEV infection 8-10. The use of non-human primates and conventional pig models is limited by high maintenance costs, difficulties in manipulation, and the need for many personnel 11,12. Miniature pigs have been experimentally infected with HEV genotypes 1, 3, and 4; they are susceptible to genotypes 3 and 4 13. Extra-hepatic manifestations have not yet been modelled because existing studies on miniature...

Hepatitis E and Pregnancy: An Unholy Alliance Unmasked from Kashmir, India

“…Recently the role of immune cells in the spread of HEV infection to various body organs has been studied. Immune cells are permissive to HEV and help the virus enter various body organs, as shown in vivo and in vitro studies [ 165 , 166 ]. It is possible that this may be one of the ways in which the virus reaches the maternal–fetal interface and causes vertical transmission.…”

Model systems for studying extrahepatic pathogenesis of hepatitis E virus. Current knowledge and future directions

“… 113 HEV may replicate in the immune cells circulating and/or residing in the lymph node such as T‐lymphocytes, B‐lymphocytes, plasma cells and macrophages. Jung and colleagues recently showed that HEV enters various organs via the immune cells 114 . They also reported that the lymphoid tissues of miniature pigs have the highest amounts of HEV antigens 114 …”

“…Jung and colleagues recently showed that HEV enters various organs via the immune cells 114 . They also reported that the lymphoid tissues of miniature pigs have the highest amounts of HEV antigens 114 …”

“…Jung and colleagues infected miniature pigs with swine‐derived HEV‐3, and signs of cytotoxicity and infiltration of the inflammatory cells were recorded in the pancreas of infected pigs 114 . Upregulation of TNF‐α and TNF‐related apoptosis‐inducing ligand (also known as death ligands) was observed in the infected pigs especially in acinar cells 114 .…”

“…Jung and colleagues infected miniature pigs with swine‐derived HEV‐3, and signs of cytotoxicity and infiltration of the inflammatory cells were recorded in the pancreas of infected pigs 114 . Upregulation of TNF‐α and TNF‐related apoptosis‐inducing ligand (also known as death ligands) was observed in the infected pigs especially in acinar cells 114 . In addition, HEV infection stimulated the key elements of necroptosis such as receptor‐interacting protein kinase 3 and phosphorylated mixed lineage kinase domain‐like protein suggesting that necroptosis is the main mechanism of HEV mediated pancreas injury 114 …”