New insights into the hepatitis E virus genotype 3 phylodynamics and evolutionary history

Hepatitis E virus (HEV) is an emergent hepatotropic virus endemic mainly in Asia and other developing areas. However, in the last decade it has been increasingly reported in high-income countries. Human infecting HEV strains are currently classified into four genotypes (1–4). Genotype 3 (HEV-3) is the prevalent virus genotype and the mostly associated with autochthonous and sporadic cases of HEV in developed areas. The evolutionary history of HEV worldwide remains largely unknown. In this study we reconstructed the spatiotemporal and population dynamics of HEV-3 at global scale, but with particular emphasis in South America, where case reports have increased dramatically in the last years. To achieve this, we applied a Bayesian coalescent-based approach to a comprehensive data set comprising 97 GenBank HEV-3 sequences for which the location and sampling date was documented. Our phylogenetic analyses suggest that the worldwide genetic diversity of HEV-3 can be grouped into two main Clades (I and II) with a Ƭ_mrca dated in approximately 320 years ago (95% HPD: 420–236 years) and that a unique independent introduction of HEV-3 seems to have occurred in Uruguay, where most of the human HEV cases in South America have been described. The phylodynamic inference indicates that the population size of this virus suffered substantial temporal variations after the second half of the 20th century. In this sense and conversely to what is postulated to date, we suggest that the worldwide effective population size of HEV-3 is not decreasing and that frequently sources of error in its estimates stem from assumptions that the analyzed sequences are derived from a single panmictic population.Novel insights on the global population dynamics of HEV are given. Additionally, this work constitutes an attempt to further describe in a Bayesian coalescent framework, the phylodynamics and evolutionary history of HEV-3 in the South American region.     

Phylogeography and phylodynamics of European genotype 3 hepatitis E virus

Hepatitis E virus is classified into four genotypes that have different geographical and host distributions. The main cause of sporadic autochthonous type E acute hepatitis in developed countries is genotype 3, which has a worldwide distribution and widely infects pigs. The aim of this study was to make hypotheses concerning the origin and global dispersion routes of this genotype by reconstructing the spatial and temporal dynamics of 208 HEV genotype 3 ORF-2 sequences (retrieved from public databases) isolated in different geographical areas.The evolutionary rates, time of the most recent common ancestors (tMRCAs), epidemic growth and phylogeography of HEV-3 were co-estimated using a MCMC Bayesian method.The maximum clade credibility tree showed the existence of two distinct main clades: clade A, which consists of only European subtypes (HEV-3e and 3f), and clade B, which consists of European subtype 3c and all of the Asian subtypes (3a, 3b and 3d) sharing a common ancestor, which most probably existed in Asia in 1920s. All of the North American isolates belonged to Asian subtype 3a.On the basis of our time-scaled phylogeographical reconstruction, we hypothesise that after originating in the early 1800s in Europe, HEV reached Asia in the first decades of 1900, and then moved to America probably in the 1970s–1980s.Analysis of the skyline plot showed a sharp increase of the number of infections between the 1980s and 2005, thus suggesting the intervention of new and highly efficient routes of transmission possibly related to changes in the pig industry.     

Molecular epidemiology of hepatitis B virus in Paraguay

Hepatitis B virus (HBV) infection is a leading cause of severe chronic liver disease worldwide. The HBV epidemiology in Latin American countries is complex and the data is still scanty and fragmentary. The aim of this study was to investigate the distribution of HBV genotypes in Paraguay and to estimate the viral population dynamic and spread pattern of the main phylogenetic group. To this end, partial and complete genome sequences were obtained from 60 blood donor candidates and analysed by phylogenetic and Bayesian phylodynamic approaches.The phylogenetic analysis based on sequences of partial Polymerase/Pre-S1 overlapping region showed a predominance of the Native American subgenotype F4 (81.7%), the presence of the European subgenotypes A2 (1.7%) and D3 (8.3%), the African subgenotype A1 (3, 5%) and the Asian subgenotypes B2 (1.7%) and C2 (1.7%). The distribution of HBV genotypes was in accordance with the ethnic composition of the population.The phylogeographic analysis of subgenotype F4 complete genomes suggests that this lineage emerged and spread in the last 300 years. Paraguay was the most probable location of the common ancestor. The lineage diverged into two main clades and spread to neighbor regions, mainly Bolivia and Northwest Argentina, and Buenos Aires. The phylogeny showed a scanty geographical structure and a complex migratory pattern.In conclusion, the HBV genotypes circulating in Paraguay reflect the ethnic origin of the population. The distribution of genotypes and the phylogeographic reconstruction showed the impact of both global and local migrations in shaping the HBV molecular epidemiology in the region.     

Identification of European-type hepatitis E virus subtype 3e isolates in Japanese wild boars: Molecular tracing of HEV from swine to wild boars

Nucleotide sequences of hepatitis E virus (HEV) isolates infecting wild boars in Mie prefecture, which is located in the central region of Japan and is far from the most prevalent regions of HEV infection in Japan, were determined and characterised. Among 144 serum samples of wild boars captured in Mie prefecture, 7 were positive for HEV-RNA. The nucleotide sequence of nearly the entire genome was determined for 4 of the 7 positive samples. Phylogenetic tree analyses indicated that 6 samples were subtype 3e and 1 was subtype 3a among the 7 isolates. We identified the indigenization of subtype 3e isolates in Japanese wild boars. Furthermore, 5 subtype 3e isolates were closely related and were located in the peripheral branch of subtype 3e isolates from European countries in the phylogenetic tree. The structure indicated that the ancestor of the 5 subtype 3e isolates originated in Europe. The phylogenetic structure and coalescent analyses suggested that the subtype 3e isolates entered Japan from Europe by importation of large-race pigs around 1966. The results also indicated that several lineages of subtype 3e expanded to a wide area of Japan around 1992 and 1 of the lineages was indigenized in wild boars in Mie prefecture between 1992 and 2009. The appearance of a wild boar cluster in the peripheral branch in the phylogenetic lineage may indicate the direction of gene flow of HEV subtype 3e from swine to wild boars. Clarification of the transmission direction or route should be helpful to prevent a future endemic or epidemic of HEV infection.     

Molecular epidemiology and genetic diversity of hepatitis B virus in Mar del Plata city,Argentina

The aim of this work was to describe the current molecular epidemiology and genetic diversity of HBV in Mar del Plata, an important Argentinean touristic city. The phylogenetic analysis of 29 HBV DNA positive serum samples showed that F1b was the predominant subgenotype (sgt, 62.1%), followed by sgt A2 (13.8%) and sgt F4, gt D and gt G (6.9% each). Among anti-HBc IgM positive samples, 75.0% were sgt F1b, followed by sgt F4 (12.5%), sgt A2 (6.25%) and sgt D (6.25%). Three recombinant full length genomes were found: two G/F1b (some of the first gt G detected in Argentina) and one F4/D2. The circulation of clinical important mutations in the city was described. Mutations at the HBsAg were detected in 34.5% of the analyzed samples, associated with laboratory diagnosis and antiviral treatment failures, immune escape and hepatocellular carcinoma. Most of the samples presented wild type BCP/PC sequences. Coalescence analysis for the most prevalent sgt F1b estimated that the diversification mainly occured during mid '90s and the tMRCA was estimated in 1987. Finally, the high presence of the autochthonous sgt F1b, associated with the anti-HBc IgM positive infection and its present-day diversification process, shows the strong impact of internal human migratory movements into the current population of Mar del Plata.     

Molecular epidemiology of hepatitis B virus in Misiones,Argentina

Hepatitis B virus (HBV) infection is a major public health problem worldwide. The aims of this study were to describe the molecular epidemiology of HBV in the Province of Misiones, Argentina and estimate the phylodynamic of the main groups in a Bayesian coalescent framework. To this end, partial or complete genome sequences were obtained from 52 blood donor candidates.The phylogenetic analysis based on partial sequences of S/P region showed a predominance of genotype D (65.4%), followed by genotype F (30.8%) and genotype A as a minority (3.8%). At subgenotype level, the circulation of subgenotypes D3 (42.3%), D2 (13.5%), F1b (11.5%) and F4 (9.6%) was mainly identified.The Bayesian coalescent analysis of 29 complete genome sequences for the main groups revealed that the subgenotypes D2 and D3 had several introductions to the region, with ancestors dating back from 1921 to 1969 and diversification events until the late ‘70s. The genotype F in Misiones has a more recent history; subgenotype F4 isolates were intermixed with sequences from Argentina and neighboring countries and only one significant cluster dated back in 1994 was observed. Subgenotype F1b isolates exhibited low genetic distance and formed a closely related monophyletic cluster, suggesting a very recent introduction.In conclusion, the phylogenetic and coalescent analyses showed that the European genotype D has a higher circulation, a longer history of diversification and may be responsible for the largest proportion of chronic HBV infections in the Province of Misiones. Genotype F, especially subgenotype F1b, had a more recent introduction and its diversification in the last 20 years might be related to its involvement in new transmission events.     

Reconstruction of the epidemic history of hepatitis B virus genotype D in Albania

Despite a recent decrease in the prevalence of HBsAg in the general population, Albania is still highly endemic for HBV infection. Genotype D is the most prevalent HBV strain in the Mediterranean area. We studied the prevalence and distribution of HBV genotypes and subgenotypes in a total of 73 HBsAg-positive patients living in Albania, and reconstructed the epidemiological history of the most prevalent HBV D subgenotype using a "phylodynamic" framework. A time-scaled genealogy of the Albanian patients' and reference P gene sequences with known sampling dates was reconstructed using an MCMC Bayesian approach that allows population growth to be estimated on the basis of coalescent theory. All of the Albanian subjects were infected with the HBV D genotype, and a percentage varying from 44.4% to 100% (depending on the ethnic or risk group) were infected with subgenotype D2, the most prevalent in the study population (72.4%). The other subgenotypes present in a minority of subjects were D1 (13.8%) and D3 (13.8%). The Bayesian skyline plot population dynamics analysis showed that genotype D2 entered the Albanian population in the late 1960s, and that the effective number of infections grew gradually until the second half of the 1980s and more rapidly until the mid-1990s, when it reached a plateau that still persists today. Our data suggest that political and socio-economic factors played an important role in determining the rapid spread of HBV infection in Albania.     

淮安市戊型病毒性肝炎人畜共患性及病毒基因型研究

目的探讨淮安市戊型病毒性肝炎病例与猪之间的联系,为控制HEV在人畜间的传播提供依据。方法在淮安市收集急性戊肝、肝炎未分型病例血液标本193份,同期在屠宰场收集生猪胆囊标本510份,采用Real-time RT-PCR和RT-PCR提取目标核苷酸,测定序列后进行分析。结果所有标本共分离出HEV-4型毒株20株,分4个亚型,HEV-4d型为优势流行毒株亚型;人源与猪源HEV毒株间的同源性为:80.3%～97.7%。结论淮安市戊肝病例与生猪感染的HEV高度同源,生猪是戊肝传播过程中一种重要的动物宿主。     

猪源乙型肝炎病毒的分子流行病学调查

目的 了解猪HBV的感染情况,探讨猪作为乙型肝炎病毒感染动物模型的可行性.方法 采用酶联免疫吸附试验(ELISA)法对血清中的HBV血清标志物进行检测,分别用S区和C区引物对血清和白细胞中HBV-DNA进行聚合酶链式反应(PCR)以检测HBV的感染情况.结果 ①234份血清标本进行了HBV血清标志物的检测,HbsAg、HBsAb、HBcAb、HBeAg、HBeAb的阳性率分别为4.70％ (11/234)、29.06％ (68/234)、79.91％ (187/234)、2.99％ (7/234)、15.81％ (37/234),血清标记物全阴性16.67％ (39/234);②血清HBV-DNA的PCR扩增结果:S区引物扩增阳性率3.4％ (8/234),C区引物扩增阳性率20％ (47/234);③白细胞DNA PCR扩增,S区扩增阳性率10.9％ (17/156),C区扩增阳性率51.3％ (80/156);④白细胞中HBV-DNA的检出率高于血清HBV-DNA的检出率,二者差异有统计学意义(P＜0.001);⑤HBV-DNA的C区检出率高于S区检出率,二者差异有统计学意义.结论 ①HBV在屠宰生猪中有较高的感染率;②白细胞中HBV-DNA的检出率高于血清HBV-DNA的检出率;③HBV-DNA的C区检测比S区检测更为敏感.     

Molecular epidemiology of chronic hepatitis C (HCV) virus

Hepatitis C virus (HCV) is a major etiologic causative agent of chronic hepatitis, cirrhosis with its attendant risks of hepatocellular carcinoma. Efforts to isolate the virus by standard immunologic and virologic techniques were unsuccessful and HCV was finally identified by direct cloning and sequencing of its genome. Although the virus was identified 15 years ago, its pathogenesis and replication are not fully understood. Progress in the molecular biology of HCV was achieved by expressing viral recombinant proteins in culture cells and utilizing recombination DNA techniques. An important feature of HCV is that the viral genomes display extensive genetic heterogeneity at the local as well as the global level. Within a host, the HCV genome population circulates as a 'quasi-species' of closely related sequences. Worldwide, a high degree of genetic variation exists resulting in at least six major genotypes of more distantly related subtypes. It has been reported, that the prevalence of each subtype varies in different geographical areas and that virus pathogenicity and sensitivity to interferon treatment, appear to vary with different subtypes.     

中国发现基因3型戊型肝炎病毒

目的通过对中国华东地区分离出的2株基因3型戊型肝炎病毒株进行同源性分析，探讨其分子起源和传播问题。方法收集华东某地区13个养猪场的133份猪粪便标本，利用巢式RT—PCR技术扩增戊肝病毒基因组的开放读码区2（ORF2）和RNA依赖的RNA聚合酶区（RdRp，ORF1），并进行基因同源性分析。结果戊肝病毒RNA检出率为43．61％（58／133）。其中，在同一个养猪场检出的2份阳性标本与23条戊肝病毒基因3型全长序列在ORF2和ORF1区的同源性分别为77．10％～92．64％和77．49％～91．14％，被划分为基因3型。另外12个养猪场的56份阳性标本均为基因4型。同时发现，某些日本分离的基因3型病毒株比其他基因3型株更接近本次分离的病毒株。结论这是在中国大陆地区首次发现基因3型戊肝病毒。同时证明在一个较为局限的群体中基因3型和4型病毒可以共存。     

Seroepidemiology and genetic characterization of hepatitis E virus in the northeast of china

The aim of this study was to analyze the prevalence of infection and genotype of hepatitis E virus (HEV) in people and animals in the northeast of China (Heilongjiang, Jilin and Liaoning provinces). This seroepidemiological study was conducted using enzyme immunoassays and human sera positive for HEV antigen or anti-HEV IgM, and animal sera positive for HEV antigen or with an S/CO ≤10 for anti-HEV were tested for HEV RNA using real-time RT-PCR and nested RT-PCR. In humans, the overall prevalence of anti-HEV IgG was 31.6% (311/985), 28.6% (147/514) and 21.1% (841/3994) in individuals frequent, infrequent, and very rare contact with swine, respectively. The overall prevalence of anti-HEV was 81.6% (1737/2127) in pigs above 3 months of age, 66.4% (1644/2473) in pigs below 3 months of age, 18.7% (301/1612) in cattle and 12.4% (162/1302) in sheep. 1211 samples were tested for HEV RNA using real-time RT-PCR and 71 were positive. 30 of the 71 samples also were positive for HEV RNA using nested RT-PCR. These 30 isolates shared 81.2–100% sequence identity with each other at the nucleotide level and belonged to HEV genotype 4, regardless whether from human or animals. The results indicate that HEV infection is widely spread in the northeast of China. The prevalence of anti-HEV in individuals with frequent contact with pigs was significantly higher than those without and the HEV sequences isolated from such individuals were related more closely to isolates from pigs. These support strongly the hypothesis of a zoonotic origin of hepatitis E.     

戊型肝炎病毒基因分型及动物感染率的研究进展

戊型肝炎(戊肝)病毒(HEV)主要经粪-口途径传播,多发生在卫生条件较差的发展中国家,常因水源被污染而造成大规模的流行;发达国家主要是散发病例,多由食入污染的食物引起[1].     

Hepatitis E virus genotype 3 in humans and Swine, Bolivia

We determined the seroprevalence of hepatitis E virus (HEV) in persons in 2 rural communities in southeastern Bolivia and the presence of HEV in human and swine fecal samples. HEV seroprevalence was 6.3%, and HEV genotype 3 strains with high sequence homology were detected.     

A hepatitis E outbreak by genotype 4 virus in Shandong province,China

Hepatitis E vaccine was available in China in 2012, but the priority population for immunization is not clear. In 2013, a hepatitis E outbreak occurred in a company of Shandong province, China where most employees moved from other provinces and dined at the company’s cafeteria. A total of fourteen (19%, 14/73) case-patients were identified, and three of them had symptomatic infection with one death. The proportion of symptomatic infection was much higher among those aged ⩾50 years than those aged <50 years (2/2 vs. 1/12, P = 0.03), and higher in males than females (3/8 vs. 0/6, P = 0.21). Food in the company’s cafeteria might be the possible source of the outbreak. The findings from this outbreak investigation indicate that individuals aged ⩾50 years, particularly males, might be the population of top priority for hepatitis E vaccination in China.