A549 and PLC/PRF/5 cells can support the efficient propagation of swine and wild boar hepatitis E virus (HEV) strains: demonstration of HEV infectivity of porcine liver sold as food

Abstract

Recent evidence has indicated the cross-species transmission of hepatitis E virus (HEV) from pigs and wild boars to humans, causing zoonosis, mostly via consumption of uncooked or undercooked animal meat/viscera. However, no efficient cell culture system for swine and boar HEV strains has been established. We inoculated A549 cells with 12 swine and boar HEV strains of liver, feces, or serum origin at an HEV load of ≥2.0 × 10(4) copies per well and found that the HEV progeny replicated as efficiently as human HEV strains, with a maximum load of ~10(8) copies/ml. However, the HEV load in the culture medium at 30 days post-inoculation differed markedly by inoculum, ranging from 1.0 × 10(2) to 1.1 × 10(7) copies/ml upon inoculation at a lower load of approximately 10(5) copies per well. All progeny were passaged successfully onto A549 and PLC/PRF/5 cells. In sharp contrast, no progeny viruses were detectable in the culture supernatant upon inoculation with 13 swine and boar HEV strains at an HEV load of <1.8 × 10(4) copies per well. The present study also demonstrates that swine liver sold as food can be infectious, supporting the risk of zoonotic food-borne HEV infection.

Zoonotic Hepatitis E Virus: Classification, Animal Reservoirs and Transmission Routes

“…Pigs inoculated intravenously with homogenates from contaminated pig livers sold in grocery stores in the United States became infected with HEV [148]. Moreover, HEV was successfully cultured in human cell lines inoculated with extracts from ficatelli sausages produced in France [152] or raw porcine liver purchased from grocery stores in Japan [153]. …”

Culture systems for hepatitis E virus

“…However, it remains unclear whether swine HEV strains of genotypes 3 and 4 recovered from domestic pigs and wild boar can grow as efficiently as human HEV strains in human cultured cells, irrespective of the source of the inoculum virus. Therefore, to investigate this problem, liver homogenate, serum and fecal specimens obtained from HEV-infected domestic pigs and wild boar were employed as inocula, and various swine and boar HEV strains were cultivated in A549 and PLC/PRF/5 cells and their replication efficiency was evaluated in relation to the viral load and origin of the inoculum [65]. …”

Hepatitis E

“…24 HEV grows poorly in vitro, but recently, several cell-culture systems have been developed for genotypes 3 and 4. 25,26 An important finding was the identification of short human-sequence inserts in HEV RNA; these inserts facilitated tissue-culture adaptation. Remarkably, similar human-sequence inserts have been identified in HEV RNA isolated directly from patients with striking neurologic complications of hepatitis E. 26 These findings suggest that recombination events may alter the replicative capacity, tissue specificity, and pathogenicity of HEV and make this agent unique among human hepatitis viruses.…”

“…23,[25][26][27][28] Some of these viruses may represent new HEV genotypes, but most resemble genotypes 3 and 4. Although several viruses have been shown to be infectious in pigs, the potential of these mammalian viruses to infect and cause disease in humans (i.e., their zoonotic potential) remains unclear.…”