- Short report
- Open Access
Recombination analysis reveals a double recombination event in hepatitis E virus
© Wang et al; licensee BioMed Central Ltd. 2010
- Received: 25 January 2010
- Accepted: 14 June 2010
- Published: 14 June 2010
Recombination of Hepatitis E Virus (HEV) has rarely been reported. In the present study, phylogenetic and recombination analyses were performed on 134 complete HEV genomes. Three potentially significant recombination events, including both intra-genotype and one inter-genotype, were identified by recombination detection analysis. Recombination events I and II occurred intra-genotype and inter-genotype, respectively, among three isolates, including the lineage represented by CHN-XJ-SW13 (GU119961, swine isolate), E067-SIJ05C (AB369690, human isolate), and JJT-Kan (AB091394, human isolate), and lead to the recombinant swine isolate swCH31 (DQ450072). Recombination event III occurred between the lineage represented by the NA1 (M73218) and K52-87 (L25595), which resulted in the recombinant Xingjiang-1 (D11092). Our analyses proved that that recombination could occur between human and swine HEV strains, double recombination events existed in HEV, and recombination event could happen within ORF2 region of HEV. These results will provide valuable hints for future research on HEV diversity.
- Recombination Event
- Minor Parent
- Capsid Gene
- Double Recombination Event
- Significant Recombination Event
Hepatitis E virus (HEV), a member of the genus Hepevirus, is a non-enveloped virus with a positives-stranded RNA genome of approximately 7.2 kb in length (Reyes et al., 1990). HEV is believed to be transmitted by the faecal-oral route and its infection affects primarily young adults and is generally mild [1, 2]. The mortality rate of HEV infection is higher among women, and hepatitis E virus infection is highly prevalent among pregnant women [3, 4]. HEV and antibodies to HEV have been reportedly found in a wide variety of animals, especially swine [5–8]. A hypothesis has arisen that zoonosis is involved in the transmission of HEV.
The HEV genome has three partially overlapped open reading frames (ORFs). ORF1 is located at the 5'-terminus of the genome and encodes non-structural proteins. ORF2 is at the 3'-terminus of the HEV genome and encodes the viral capsid protein which has three glycosylation sites. ORF3 overlaps with either ORF1 or ORF2 . HEV isolates were divided into four distinct genotypes according to sequence and phylogenetic analyses. Genotype 1 was previously believed to only infect humans, but reportedly detected from a pig in Cambodia recently . Genotype 2 has only been identified in humans in Mexico and Africa (Nigeria, Chad). Genotype 3 is prevalent in swine herds and humans all over the world. Genotype 4 HEV is mainly distributed in China, Japan, India, Indonesia, and Vietnam. Genotype 4 HEV has a wide host range, being prevalent in humans, swine, and some other animals. These four types of virus are thought to comprise a single serotype .
Recombination is a relatively common phenomenon in positive-sense RNA viruses [11–13] and understanding recombination can be helpful in unravelling the evolution of pathogens and drug resistance. So far, two reports revealed the presence of HEV recombination. However, one of them was performed in 2005, when there were only about 30 HEV strains with full genome available in GenBank ; the other one was focused on the open reading frame structure analysis . In the present study, therefore, we analyze the available complete HEV genome sequences in GenBank in order to systematically investigate the presence of recombination among HEV strains.
The average P-value of three recombinant events analyzed by six recombination detection methods
3.59 × 10-12
5.56 × 10-24
1.31 × 10-39
8.31 × 10-18
7.55 × 10-10
1.52 × 10-17
4.18 × 10-19
1.25 × 10-25
1.26 × 10-45
1.67 × 10-16
3.77 × 10-18
5.69 × 10-16
6.73 × 10-10
1.78 × 10-6
6.57 × 10-10
5.76 × 10-6
4.31 × 10-5
1.47 × 10-4
Recombination within the capsid gene has been suggested for other positive-strand RNA virus such as norovirus [24, 25]. The recombination of the virus capsid gene may play a key role in virulence, allowing new recombinants to evade immune response and possible viral extinction. ORF2 of HEV encodes the capsid protein, which contains the antigenic regions and partial nucleotide sequence of ORF2 is predicted to be well suited for phylogenetic classification of HEV [26, 27]. In the present study, we detected that recombination event II occurred within the capsid gene of HEV (Fig 2A), and such mutations in the capsid gene will produce a protein which is better able to evade the host immune response, thereby allowing higher viral titer and greater overall fitness. Moreover, we should notice that recombination event II happened between human (E067-SIJ05C) and swine (CHN-XJ-SW13) HEV isolates. This suggested that recombination of HEV can occurred between viruses infecting different host species, which needs to be recorded, as they have serious implications for the future evolution of infectious agents.
In our study, Uigh179 (D11093) was revealed to be a potential recombinant (Additional file 1: Fig.S1), which is consistent with a previous report . However, the potential parental strains of this recombinant were different between the present study and previous study. Van's study didn't include the strain Xingjiang-1(D11092) which was indicated to be one of the most probable parental strains in the present study. The strain information of Uigh179 and Xingjiang-1 showed that the two strains were sequenced in the same lab in Nihon University School of Medicine in 1992. Therefore, it should be cared whether this recombination event non-naturally occurred by sequencing error and/or contamination in the lab. A genotype 3 HEV strains swJ13-1 (AB097811) was also found to be a potential recombinant in the present study (Additional file 2: Fig S2). It was isolated from a 4-month-old pig in 2002 in Japan . Our study suggested this recombination event occurred between HE-JA1 (AB097812) and swJB-H7 (AB481227). The potential recombinant swJ13-1 and its parental strain HE-JA1, which was isolated from a Japanese patient, were determined in the same lab and shared 99.0% sequence identity over the complete genome. The ORF2 and ORF3 of the two strains were even identical to each other . It is therefore tempting to speculate that this recombination event might happen non-naturally in the lab.
Taken together, we analyzed 134 non-redundant HEV complete genomes using detailed phylogenetic and recombination analytic methods and identified two recombinants (swCH31 and Xingjiang-1), and swCH31 was proved to be produced by double recombination events which occurred among three potential parental strains belonging to two different genotypes. Moreover, it should be noted that recombination could occur between human and swine HEV strains, double recombination events existed in HEV, and recombination event can happen within ORF2 region of HEV. Other two isolates (AB097811 and D11093) may be potential non-natural recombinants happened in the lab. The present study could reminder us that recombination also contribute to the genetic variety of HEV.
This work was supported by the Professional Research Foundation for Advanced Talents of Jiangsu University under Grant No.10JDG059 and Open Fund of State Key Laboratory of Veterinary Etiological Biology No. SKLVEB2010KFKT002.
- Aggarwal R, Krawczynski K: Hepatitis E: an overview and recent advances in clinical laboratory research. J Gastroenterol Hepatol 2000, 15: 9-20. 10.1046/j.1440-1746.2000.02006.xPubMedView ArticleGoogle Scholar
- Zhang W, Yang S, Shen Q, Liu J, Shan T, Huang F, Ning H, Kang Y, Yang Z, Cui L, Zhu J, Hua X: Isolation and characterization of a genotype 4 Hepatitis E virus strain from an infant in China. Virol J 2009, 6: 24. 10.1186/1743-422X-6-24PubMedPubMed CentralView ArticleGoogle Scholar
- Adjei AA, Tettey Y, Aviyase JT, Adu-Gyamfi C, Obed S, Mingle JA, Ayeh-Kumi PF, Adiku TK: Hepatitis E virus infection is highly prevalent among pregnant women in Accra, Ghana. Virol J 2009, 6: 108. 10.1186/1743-422X-6-108PubMedPubMed CentralView ArticleGoogle Scholar
- Caron M, Kazanji M: Hepatitis E virus is highly prevalent among pregnant women in Gabon, central Africa, with different patterns between rural and urban areas. Virol J 2008,22(5):158. 10.1186/1743-422X-5-158View ArticleGoogle Scholar
- Goens SD, Perdue ML: Hepatitis E viruses in humans and animals. Anim Health Res Rev 2004, 5: 145-156. 10.1079/AHR200495PubMedView ArticleGoogle Scholar
- Saad MD, Hussein HA, Bashandy MM, Kamel HH, Earhart KC, Fryauff DJ, Younan M, Mohamed AH: Infect Genet Evol. Hepatitis E virus infection in work horses in Egypt 2007, 7: 368-73.Google Scholar
- Schielke A, Sachs K, Lierz M, Appel B, Jansen A, Johne R: Detection of hepatitis E virus in wild boars of rural and urban regions in Germany and whole genome characterization of an endemic strain. Virol J 2009, 6: 58. 10.1186/1743-422X-6-58PubMedPubMed CentralView ArticleGoogle Scholar
- Zhang W, Shen Q, Mou J, Gong G, Yang Z, Cui L, Zhu J, Ju G, Hua X: Hepatitis E virus infection among domestic animals in eastern China. Zoonoses Public Health 2008, 55: 291-298. 10.1111/j.1863-2378.2008.01136.xPubMedView ArticleGoogle Scholar
- Panda SK, Thakral D, Rehman S: Hepatitis E virus. Rev Med Virol 2007, 17: 151-180. 10.1002/rmv.522PubMedView ArticleGoogle Scholar
- Caron M, Enouf V, Than SC, Dellamonica L, Buisson Y, Nicand E: Identification of genotype 1 hepatitis E virus in samples from swine in Cambodia. J Clin Microbiol 2006, 44: 3440-3442. 10.1128/JCM.00939-06PubMedPubMed CentralView ArticleGoogle Scholar
- Chare ER, Holmes EC: A phylogenetic survey of recombination frequency in plant RNA viruses. Arch Virol 2006, 151: 933-946. 10.1007/s00705-005-0675-xPubMedView ArticleGoogle Scholar
- Pickett BE, Lefkowitz EJ: Recombination in West Nile Virus: minimal contribution to genomic diversity. Virol J 2009, 6: 165. 10.1186/1743-422X-6-165PubMedPubMed CentralView ArticleGoogle Scholar
- Moreno P, Alvarez M, López L, Moratorio G, Casane D, Castells M, Castro S, Cristina J, Colina R: Evidence of recombination in Hepatitis C Virus populations infecting a hemophiliac patient. Virol J 2009, 6: 203. 10.1186/1743-422X-6-203PubMedPubMed CentralView ArticleGoogle Scholar
- van Cuyck H, Fan J, Robertson DL, Roques P: Evidence of recombination between divergent hepatitis E viruses. J Virol 2005, 79: 9306-9314. 10.1128/JVI.79.14.9306-9314.2005PubMedPubMed CentralView ArticleGoogle Scholar
- Fan J: Open reading frame structure analysis as a novel genotyping tool for hepatitis E virus and the subsequent discovery of an inter-genotype recombinant. J Gen Virol 2009, 90: 1353-1358. 10.1099/vir.0.009431-0PubMedView ArticleGoogle Scholar
- Tamura K, Dudley J, Nei M, Kumar S: MEGA4: Molecular evolutionary genetics analysis (MEGA) software version 4.0. Mol Biol Evol 2007, 24: 1596-1599. 10.1093/molbev/msm092PubMedView ArticleGoogle Scholar
- Martin D, Rybicki E: RDP: detection of recombination amongst aligned sequences. Bioinformatics 2000, 16: 562-563. 10.1093/bioinformatics/16.6.562PubMedView ArticleGoogle Scholar
- Padidam M, Sawyer S, Fauquet CM: Possible emergence of new geminiviruses by frequent recombination. Virology 1999, 265: 218-225. 10.1006/viro.1999.0056PubMedView ArticleGoogle Scholar
- Martin DP, Posada D, Crandall KA, Williamson C: A modified bootscan algorithm for automated identification of recombinant sequences and recombination breakpoints. AIDS Res Hum Retrovir 2005, 21: 98-102. 10.1089/aid.2005.21.98PubMedView ArticleGoogle Scholar
- Smith JM: Analyzing the mosaic structure of genes. J Mol Evol 1992, 34: 126-9.PubMedGoogle Scholar
- Posada D, Crandall KA: Evaluation of methods for detecting recombination from DNA sequences: computer simulations. Proc Natl Acad Sci USA 2001, 98: 13757-13762. 10.1073/pnas.241370698PubMedPubMed CentralView ArticleGoogle Scholar
- Gibbs MJ, Armstrong JS, Gibbs AJ: Sister-scanning: a Monte Carlo procedure for assessing signals in recombinant sequences. Bioinformatics 2000, 16: 573-582. 10.1093/bioinformatics/16.7.573PubMedView ArticleGoogle Scholar
- Martin DP, Williamson C, Posada D: RDP2: recombination detection and analysis from sequence alignments. Bioinformatics 2005, 21: 260-262. 10.1093/bioinformatics/bth490PubMedView ArticleGoogle Scholar
- Etherington GJ, Dicks J, Roberts IN: High throughput sequence analysis reveals hitherto unreported recombination in the genus Norovirus. Virology 2006, 45: 88-95. 10.1016/j.virol.2005.09.051View ArticleGoogle Scholar
- Phan TG, Kuroiwa T, Kaneshi K, Ueda Y, Nakaya S, Nishimura S, Yamamoto A, Sugita K, Nishimura T, Yagyu F, Okitsu S, Müller WE, Maneekarn N, Ushijima H: Changing distribution of norovirus genotypes and genetic analysis of recombinant GIIb among infants and children with diarrhea in Japan. J Med Virol 2006, 78: 971-978. 10.1002/jmv.20649PubMedView ArticleGoogle Scholar
- Ge SX, Guo QS, Li SW, Zhang J, Xia NS: Design and preliminary application of a set of highly sensitive universal RT-PCR primers for detecting genotype I/IV hepatitis E virus. Chin J Virol 2005, 21: 181-187.Google Scholar
- Cooper K, Huang FF, Batista L, Rayo CD, Bezanilla JC, Toth TE, Meng XJ: Identification of genotype 3 hepatitis E virus (HEV) in serum and fecal samples from pigs in Thailand and Mexico, where genotype 1 and 2 HEV strains are prevalent in the respective human populations. J Clin Microbiol 2005, 43: 1684-2688. 10.1128/JCM.43.4.1684-1688.2005PubMedPubMed CentralView ArticleGoogle Scholar
- Aye TT, Uchida T, Ma XZ, Iida F, Shikata T, Zhuang H, Win KM: Complete nucleotide sequence of a hepatitis E virus isolated from the Xinjiang epidemic (1986-1988) of China. Nucleic Acids Res 1992, 20: 3512. 10.1093/nar/20.13.3512PubMedPubMed CentralView ArticleGoogle Scholar
- Tam AW, Smith MM, Guerra ME, Huang CC, Bradley DW, Fry KE, Reyes GR: Hepatitis E virus (HEV): molecular cloning and sequencing of the full-length viral genome. Virology 1991, 185: 120-131. 10.1016/0042-6822(91)90760-9PubMedView ArticleGoogle Scholar
- Yin S, Purcell RH, Emerson SU: A new Chinese isolate of hepatitis E virus: comparison with strains recovered from different geographical regions. Virus Genes 1994, 9: 23-32. 10.1007/BF01703432PubMedView ArticleGoogle Scholar
- Nishizawa T, Takahashi M, Mizuo H, Miyajima H, Gotanda Y, Okamoto H: Characterization of Japanese swine and human hepatitis E virus isolates of genotype IV with 99% identity over the entire genome. J Gen Virol 2003, 84: 1245-1251. 10.1099/vir.0.19052-0PubMedView ArticleGoogle Scholar
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.