Hepatitis E is an acute disease of humans caused by a small RNA virus, the hepatitis E virus (HEV). Four mammalian HEV genotypes are recognized. Genotype 1 and 2 are restricted to humans and consist of epidemic strains circulating in developing countries, mainly associated to waterborne outbreaks. Genotype 3 and 4 infect both humans and many animal species (pig, deer, wild boar, and rabbit) and circulate in developed countries. These two latter genotypes are considered zoonotic, for which pigs and less frequently other animal species (wild boar, deer) are reservoirs. Based on sequence analysis and intra-genotype variability, genotypes are divided into sub-genotypes. Thegenotype 3 can be divided into 10 sub-genotypes (3a–3j). In this study, hepatitis E infection was investigated in piglets affected with diarrhea in two small farms in Italy. The virus was detected in 11 out of 14 animals tested. Based on sequence analysis the 6 Italian strains examined belonged to two clusters that contain both swine and human strains from Europe and Japan, belonging to genotype 3 sub-genotypes e and f. The two Italian clusters shared a nucleotide identity of 81.8% in the 400bp ORF2 (capsid protein) fragment and 87.5% in the 400bp ORF1 (RdRp) fragment, confirming that genotypes 3 circulating in pigs in Italy are heterogeneous. The complete genome of a g3e strain and the complete coding regions (partial ORF1, complete ORF2 and ORF3) of a representative g3f strain were obtained and compared to other HEV full length or partial sequences available on line. Results obtained revealed that porcine strains clustered together with human and swine strains detected in Europe. The analyses conducted showed that most changes in the coding regions correspond to synonymous mutations, whereas only a small ORF1 region and the ORF3 showed sites subjected to positive selection. Further analyses are needed to understand the possible different clinical significance of HEV genotypes and sub-genotypes.
COMPLETE GENOME SEQUENCE OF A GENOTYPE 3 HEPATITIS E STRAIN IDENTIFIED IN A SWINE FARM IN ITALY
OSTANELLO, FABIO
2015
Abstract
Hepatitis E is an acute disease of humans caused by a small RNA virus, the hepatitis E virus (HEV). Four mammalian HEV genotypes are recognized. Genotype 1 and 2 are restricted to humans and consist of epidemic strains circulating in developing countries, mainly associated to waterborne outbreaks. Genotype 3 and 4 infect both humans and many animal species (pig, deer, wild boar, and rabbit) and circulate in developed countries. These two latter genotypes are considered zoonotic, for which pigs and less frequently other animal species (wild boar, deer) are reservoirs. Based on sequence analysis and intra-genotype variability, genotypes are divided into sub-genotypes. Thegenotype 3 can be divided into 10 sub-genotypes (3a–3j). In this study, hepatitis E infection was investigated in piglets affected with diarrhea in two small farms in Italy. The virus was detected in 11 out of 14 animals tested. Based on sequence analysis the 6 Italian strains examined belonged to two clusters that contain both swine and human strains from Europe and Japan, belonging to genotype 3 sub-genotypes e and f. The two Italian clusters shared a nucleotide identity of 81.8% in the 400bp ORF2 (capsid protein) fragment and 87.5% in the 400bp ORF1 (RdRp) fragment, confirming that genotypes 3 circulating in pigs in Italy are heterogeneous. The complete genome of a g3e strain and the complete coding regions (partial ORF1, complete ORF2 and ORF3) of a representative g3f strain were obtained and compared to other HEV full length or partial sequences available on line. Results obtained revealed that porcine strains clustered together with human and swine strains detected in Europe. The analyses conducted showed that most changes in the coding regions correspond to synonymous mutations, whereas only a small ORF1 region and the ORF3 showed sites subjected to positive selection. Further analyses are needed to understand the possible different clinical significance of HEV genotypes and sub-genotypes.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
