Systematic Pathogenesis and Replication of Avian Hepatitis E Virus in Specific-Pathogen-Free Adult Chickens

Abstract

Hepatitis E virus (HEV) is an important human pathogen. Due to the lack of a cell culture system and a practical animal model for HEV, little is known about its pathogenesis and replication. The discovery of a strain of HEV in chickens, designated avian HEV, prompted us to evaluate chickens as a model for the study of HEV. Eighty-five 60-week-old specific-pathogen-free chickens were randomly divided into three groups. Group 1 chickens (n ‫؍‬ 28) were each inoculated with 5 ؋ 10 4.5 50% chicken infectious doses of avian HEV by the oronasal route, group 2 chickens (n ‫؍‬ 29) were each inoculated with the same dose by the intravenous (i.v.) route, and group 3 chickens (n ‫؍‬ 28) were not inoculated and were used as controls. Two chickens from each group were necropsied at 1, 3, 5, 7, 10, 13, 16, 20, 24, 28, 35, and 42 days postinoculation (dpi), and the remaining chickens were necropsied at 56 dpi. Serum, fecal, and various tissue samples, including liver and spleen samples, were collected at each necropsy for pathological and virological testing. By 21 dpi, all oronasally and i.v. inoculated chickens had seroconverted. Fecal virus shedding was detected variably from 1 to 20 dpi for the i.v. group and from 10 to 56 dpi for the oronasal group. Avian HEV RNA was detected in serum, bile, and liver samples from both i.v. and oronasally inoculated chickens. Gross liver lesions, characterized by subcapsular hemorrhages or enlargement of the right intermediate lobe, were observed in 7 of 28 oronasally and 7 of 29 i.v. inoculated chickens. Microscopic liver lesions were mainly lymphocytic periphlebitis and phlebitis. The lesion scores were higher for oronasal (P ‫؍‬ 0.0008) and i.v. (P ‫؍‬ 0.0029) group birds than for control birds. Slight elevations of the plasma liver enzyme lactate dehydrogenase were observed in infected chickens. The results indicated that chickens are a useful model for studying HEV replication and pathogenesis. This is the first report of HEV transmission via its natural route in a homologous animal model. Hepatitis E virus (HEV), the causative agent of hepatitis E, is responsible for the majority of enterically transmitted cases of non-A and non-B hepatitis (2,34,35). HEV is a singlestranded, positive-sense, nonenveloped RNA virus with a genome of about 7.2 kb (34). The genome contains three open reading frames (ORFs) and short 5Ј and 3Ј untranslated regions. ORF1, the largest of the three ORFs, encodes nonstructural proteins, and ORF2 encodes the putative capsid protein.The small ORF3, which partially overlaps ORF1 and ORF2, encodes a cytoskeleton-associated phosphoprotein (34,35). Hepatitis E is epidemic and endemic in many developing countries.

Prolonged Fecal Shedding of Hepatitis E Virus (HEV) during Sporadic Acute Hepatitis E: Evaluation of Infectivity of HEV in Fecal Specimens in a Cell Culture System

“…One of the most remarkable results of this study was that HEV RNA was detectable in the fecal specimen obtained from a patient (patient 1) even on day 121 after the presumed onset of hepatitis, or 109 days after the day on which the peak ALT level of 620 IU/liter was observed. Recently, prolonged fecal virus shedding (beyond 56 dpi) was observed in only 2 of 15 pigs experimentally infected with genotype 3 HEV (14) and only one of nine chickens experimentally infected with avian HEV (6). The observation of prolonged fecal virus shedding from a natural case of human hepatitis E, coupled with similar observations in HEV infections from a very small number of experimentally infected animals, indicates that, indeed, prolonged fecal shedding does occur during HEV infection.…”

Avian hepatitis E virus infection and possible associated clinical disease in broiler breeder flocks in Hungary

“…Recent experimental infections with aHEV have concentrated on virus kinetics (Billam et al, 2005) rather than on gross pathological features. Further confirmation by experimental infections using an infectious clone of aHEV similar to the methodology of Huang et al (2005) is needed to prove causation, but variation in viral virulence and tropism, host genotype, timing and dose of infection and interaction with other management factors, pre-existing immunity and agents may explain the variation in clinical effects of infection between flocks and even individual birds.…”

Initiation at the Third In-Frame AUG Codon of Open Reading Frame 3 of the Hepatitis E Virus Is Essential for Viral Infectivity In Vivo

“…Increasing evidence indicates that hepatitis E is a zoonotic disease, and animal reservoirs for HEV exist (17,19,22,24,31). We recently discovered and characterized two animal strains of HEV that are genetically and antigenically closely related to human HEV: swine HEV from pigs (15)(16) and avian HEV from chickens (1,(7)(8). We subsequently demonstrated that swine HEV can cross species barriers and infect nonhuman primates (16) and that pig handlers in the United States and other countries are at increased risk of zoonotic HEV infection (18).…”