Abstract
BackgroundWild boar-derived hepatitis E (HEV) genotype 3 virus has been successfully isolated in cell lines of human origin only. Considering the zoonotic potential and possible extrahepatic localisation of genotype 3 strain, it is important to investigate the viability of cell lines of different animal and tissue origins. Therefore, the objective of the present study was to determine the permissiveness of non-human primate (MARC-145 and Vero) and swine (PK-15) cell lines of kidney origin, and a mouse neuroblastoma (Neuro-2a) cell line for isolation of wild boar-derived HEV genotype 3.ResultsThis study showed that MARC-145, PK-15, Neuro-2a and Vero cell lines were permissive to wild boar-derived HEV genotype 3 subtype 3i harbouring viral genome equivalents of 1.12 × 107 copies/ml, 2.38 × 105 copies/ml, 2.97 × 107 copies/ml and 4.01 × 107 copies/ml after five serial passages respectively. In all permissive cell lines, HEV was continuously recovered from growth medium between five and at least 28 days post-infection. Peak loads of HEV genome equivalents were observed on days 7, 12, 19 and 30 in MARC-145 (2.88 × 107 copies/ml), Vero (4.23 × 106 copies/ml), Neuro-2a (3.15 × 106 copies/ml) and PK-15 (2.24 × 107 copies/ml) cell lines respectively. In addition, successful virus isolation was confirmed by immunofluorescence assay targeting HEV capsid protein and sequencing of HEV isolate retrieved from cell cultures.ConclusionsThis study showed that wild boar-derived HEV genotype 3 subtype 3i strain was capable of infecting cell lines of animal origin, including primate and porcine kidney cells (MARC-145, PK-15 and Vero), and mouse neuroblastoma cells (Neuro-2a), supporting the notion of the capacity of HEV genotype 3 to cross the species barrier and extra-hepatic localisation of the virus. These findings warrant further studies of tested cell lines to investigate their capacity as an efficient system for HEV propagation. HEV isolates from other wild animal hosts should be isolated on tested cell lines in order to generate more data on HEV transmission between wild animal populations and their role as sources of human infections.
Highlights
Wild boar-derived hepatitis E (HEV) genotype 3 virus has been successfully isolated in cell lines of human origin only
Hepatitis E virus (HEV) Ribonucleic acid (RNA) was first detected in growth medium 5 days after inoculation, and remained present until day 33 and 28 in Neuro-2a and vervet monkey (Vero) cell lines respectively, and until day 35 in MARC-145 and PK-15 cell lines (Fig. 2)
Changes in viral loads throughout the incubation period varied between cells, with peak loads observed on days 7, 12, 19 and 30 in MARC-145 (2.88 × 107 copies/ml), Vero (4.23 × 106 copies/ml), Neuro-2a (3.15 × copies/ml) and PK-15 (2.24 × copies/ml) cell lines respectively
Summary
Wild boar-derived hepatitis E (HEV) genotype 3 virus has been successfully isolated in cell lines of human origin only. A limited number of cell lines originating from non-human animal tissue have been employed for isolation of HEV genotypes 3 and 4. There is currently no information available on the capacity of HEV strains circulating in European wild boar populations to infect cell lines of animal or human origin. HEV is known to manifest extra-hepatic localisation in infected individuals, suggesting the capacity of the virus to infect cell lines of different tissue origin. There have been no successful attempts to use animal cell lines originating from tissues other than liver or lungs for wild boar-derived HEV isolation
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