Hepatitis E virus (HEV) capsid antigens derived from viruses of human and swine origin are equally efficient for detecting anti-HEV by enzyme immunoassay

The recombinant truncated ORF2 (capsid) antigen derived from the Meng strain of swine hepatitis E virus (HEV) differs from that of the Sar-55 strain of human HEV by approximately 5% at the amino acid level. Serial serum samples from two chimpanzees and six rhesus monkeys experimentally infected with HEV were tested with one enzyme immunoassay (EIA) based on the Sar-55 antigen and with a second EIA based on the Meng antigen. We obtained 98% agreement (kappa = 0.952) by direct comparison. The virtually identical results obtained with these antigens in detecting seroconversion following infection with HEV suggests that they were reacting with antibodies that detect the same or very similar epitopes of HEV. We then tested human and swine serum samples for anti-HEV in EIAs that utilized one or the other of the two ORF2 antigens and showed that these results were also virtually identical. The specimens tested included swine sera from the United States, Canada, China, Korea, and Thailand and sera from veterinarians, U.S. and non-U.S. volunteer blood donors, and U.S. and non-U.S. animal handlers. We tested 792 swine sera and obtained 93% agreement (kappa = 0.839). We similarly tested 882 human sera and obtained 99% agreement (kappa = 0.938). Moreover, we found virtually no difference in the levels of prevalence of anti-HEV as measured by the two tests, again suggesting that the antigens derived from human and swine HEV contain the same immunodominant epitopes.     

Ongoing subclinical infection of hepatitis E virus among blood donors with an elevated alanine aminotransferase level in Japan

Ongoing subclinical infection of hepatitis E virus (HEV) has not been fully studied. In the present study, serum samples were collected from 6700 voluntary blood donors with an elevated alanine aminotransferase (ALT) level of 61-476 IU/l at a Japanese Red Cross Blood Center, and were tested for the presence of IgG, IgM and IgA classes of antibodies to HEV (anti-HEV) by in-house ELISA and HEV RNA by nested RT-PCR. Overall, 479 blood donors (7.1%) were positive for anti-HEV IgG, including 8 donors with anti-HEV IgM and 7 donors with anti-HEV IgA. Among the nine donors with anti-HEV IgM and/or anti-HEV IgA, six had detectable HEV RNA. The presence of HEV RNA was further tested in 10-sample minipools of sera from the remaining 6691 donors, and three donors including one without anti-HEV IgG were found to be positive for HEV RNA. When stratified by ALT level, the prevalence of HEV RNA was significantly higher among the 109 donors with ALT > or = 201 IU/l than among the 6591 donors with ALT of 61-200 IU/l (2.8% vs. 0.1%, P < 0.0001). The HEV isolates obtained from the nine viremic donors segregated into genotype 3, shared a wide range of identities of 85.6-98.5% and were 87.3-93.9% similar to the Japan-indigenous HEV strain (JRA1), in the 412-nucleotide sequence of open reading frame 2. This study suggests that approximately 3% of Japanese individuals with ALT > or = 201 IU/l have ongoing subclinical infection with various HEV strains.     

Experimental infection of pigs with the newly identified swine hepatitis E virus (swine HEV), but not with human strains of HEV

Summary.  A novel virus of pigs, swine hepatitis E virus (swine HEV), was recently identified and shown to be antigenically and genetically related to human HEV. In the present study, we attempted to infect specific-pathogen-free (SPF) pigs experimentally with swine HEV or with human strains of HEV. Serum samples collected from naturally infected pigs were used as the source of swine HEV. Pigs inoculated intravenously with serum samples containing swine HEV seroconverted to anti-HEV 4 to 8 weeks postinoculation, and the virus spread to an uninoculated pig. Swine HEV was detected in nasal and rectal swab materials as early as 2 weeks postinoculation and for 4 to 8 weeks thereafter. Viremia appeared 4 to 6 weeks postinoculation and lasted 1 to 3 weeks. The inoculated pigs appeared clinically normal and serum liver enzymes were not significantly elevated. In contrast, pigs were not infected when inoculated intravenously with about 10⁵ monkey infectious doses of one of two human strains of HEV (Sar-55 or Mex-14). Received December 9, 1997 Accepted February 18, 1998     

High prevalence of anti-hepatitis E virus antibodies in blood donors from South West France

Cases of autochthonous acute hepatitis E occur in most industrialized countries and are frequent in the South West of France. The prevalence of anti-hepatitis E virus (HEV) IgG antibodies in blood donors in this area was determined. A total of 529 samples from rural and urban blood donors were tested. The overall prevalence was 16.6%, 19.1% of rural donors and 14.2% of urban donors had anti-HEV antibodies (P = 0.13). The antibodies were widely distributed among all age groups and the sex ratio of the anti-HEV positive blood donors was 1.12 (P = 0.57). Hunting was the only pastime or profession associated with a high prevalence of anti-HEV antibodies (P = 0.038). The frequency of anti-HEV antibodies in blood donors could reflect active autochthonous transmission in this area of France. As the risk factors for HEV infection in industrialized countries are still unknown, further studies are needed to clarify the epidemiology of HEV infection in the Midi-Pyrénées region.     

无偿献血人群戊型肝炎病毒感染情况调查

目的调查绍兴市街头无偿献血者戊型肝炎病毒感染情况。方法3701例无偿献血者标本采用ELISA方法检测抗-HEV IgG和抗-HEV IgM,RT-PCR检测抗-HEV IgM阳性血清HEV RNA。结果本市无偿献血者抗-HEV IgG阳性率为29.91%(1107/3701);抗-HEVIgM阳性率为1.35%(50/3701);HEV RNA阳性6例,检出率为0.16%(6/3701),均为HEV基因1型;各季节抗-HEV IgG和抗-HEV IgM的阳性检出率无显著差异。结论加强对献血者感染HEV情况的检测和研究,对保证用血安全,完善安全输血的保障体系有切实的意义。     

Seroprevalence of antibodies to hepatitis E virus in the normal blood donor population and two aboriginal communities in Malaysia.

The prevalence of antibodies to hepatitis E virus (HEV) has been examined in many countries, but such studies have generally been limited to majority populations such as those represented in healthy blood donors or cross sections of urban populations. Due to its major route of enteric transmission, large differences in HEV prevalence might be expected between populations in the same country but with different living conditions. Using an ELISA based on GST-ORF2.1 antigen, the prevalence of IgG-class antibodies to HEV was examined in three distinct populations in Malaysia: the normal (urban) blood donor population and two aboriginal communities located at Betau, Pahang and Parit Tanjung, Perak. IgG anti-HEV was detected in 45 (44%) of 102 samples from Betau and 15 (50%) of 30 samples from Parit Tanjung, compared to only 2 (2%) of 100 normal blood donors. The distribution of sample ELISA reactivities was also consistent with ongoing sporadic infection in the aboriginal communities, while there was no significant relationship between HEV exposure and age, sex, or malaria infection. The high prevalence of antibodies to HEV in the two aboriginal communities indicates that this group of people are at high risk of exposure to HEV compared to the general blood donors, and the results suggest that studies of HEV seroprevalence within countries must take into account the possibility of widely varying infection rates between populations with marked differences in living conditions.     

猪、羊、鸡抗-HEV抗体流行率调查

目的 探讨猪、羊、鸡群中抗-HEV抗体流行率。方法从新疆、广西、广东、北京和河北收集猪、羊、鸡的血清标本498份，应用双抗原夹心酶联免疫法(ELISA)检测抗-HEV抗体。结果 猪抗-HEV阳性率为67．53％(104／154)，其中新疆4～5个月龄猪血清抗-HEV阳性率为100．00％，广西3个月龄以下仔猪抗-HEV阳性率为36．00％(9／25)，6月龄以上猪阳性率为71．67％(86／120)；新疆108份绵羊血清抗-HEV抗体全部阴性；236份鸡血清标本的抗-HEV阳性率仅为1．27％(3／236)。广东罗定、深圳和广西柳州郊区鸡血清标本中各检测出一份抗-HEV阳性，阳性率分别为4．00％(1／25)、1．49％(1／67)、1．49％(1／67)。北京郊区25份和河北52份鸡血清抗-HEV检测全部阴性。结论 猪、鸡群中存在HEV感染，猪抗-HEV抗体流行率最高。猪和鸡在传播人HEV中的作用值得进一步研究。     

河南地区不同月龄猪戊型肝炎病毒感染情况调查

目的 调查河南地区不同月龄猪戊型肝炎病毒(HEV)感染情况.方法 从河南五个地区共采集623份猪血清,其中3月龄以下血清113份,3月龄以上血清510份,酶联免疫诊断试剂盒分别检测HEV抗原和抗体.对抗原阳性者用套式RT-PCR检测HEV核酸,并对核酸阳性者进行克隆和序列分析.结果 3月以下组和3月以上组的抗体阳性率分别为90.27%和92.55%,差异无统计学;而两组的抗原阳性率分别为15.93%和5.69%,差异有统计学意义(P＜0.001).各地区间的抗原和抗体阳性率存在明显的统计学差异.在47份抗原阳性样本中,检出5例为HEV核酸阳性,序列分析显示4例为HEV4型,1例为HEV 1型.结论 河南地区猪的HEV感染率较高,而且不同地区存在明显差异.     

Investigation of hepatitis E virus infection in swine from Hunan province, China

Nine hundred and four serum samples were collected from pigs from 16 pig farms in China's Hunan province and tested for anti-hepatitis E virus (HEV) antibody and the HEV capsid antigen using EIAs. Of the 904 samples, 617 (68.3%) and 57 (6.3%) were positive for anti-HEV antibody and antigen, respectively. The prevalence of HEV antibodies and detection of antigen varied significantly among pigs from different farms (P < 0.01). The positivity rate for anti-HEV antibody and occurrence of high titer antibody were significantly higher in pigs above, than in those below, 3 months of age, whilst the detection of antigen did not differ significantly between the two groups. Based on these data, 481 serum samples that were positive for HEV antigen or with an S/CO < or =10 for anti-HEV were tested for HEV RNA using real-time RT-PCR; 28 of 481 (5.8%) were positive. The positivity rate of HEV RNA was much higher for the HEV antigen positive sera (40.1%) than the anti-HEV antibody positive (1.4%) or negative (1.1%), antigen negative samples. Sixteen of the 28 samples were positive for HEV RNA using nested RT-PCR and their products were cloned and sequenced. These 16 isolates belonged to HEV genotype 4, including 12 that did not belong to any subtype of HEV genotype 4 reported previously. Thus, the infection rate of HEV in pigs is high and the HEV antigen has a close relationship with HEV RNA. The HEV genotype infecting the pigs was genotype 4 and a novel subtype may exist in Hunan province.     

Hepatitis E virus infection prevalence among selected populations in Iowa.

BACKGROUND: HEV causes an enteric infectious disease endemic in developing areas with hot climate. A case of endogenous HEV infection has been reported in the US. Recently, HEV-like virus was isolated from swine in Iowa. Swine production is a major industry in Iowa with the potential for human exposure to swine in and around industrial and family farm operations. OBJECTIVE: The study objective was to determine whether individuals in Iowa are exposed to HEV. STUDY DESIGN: Anti-HEV antibody prevalence in four selected Iowa populations was determined. Sera were collected from 204 patients with non-A, non-B, non-C hepatitis (non-A-C); 87 staff members of the Department of Natural Resources (DRN); 332 volunteer blood donors in 1989; and 111 volunteer blood donors in 1998. All sera were tested for anti-human HEV IgM and IgG by ELISA with confirmation of positivity by a peptide neutralization test. RESULTS: Both the patients with non-A, non-B, non-C hepatitis (4.9%) and the healthy field workers from the Iowa DNR (5.7%) showed significantly higher prevalence of anti-HEV IgG antibodies compared to normal blood donor sera collected in 1998 (P < 0.05). CONCLUSIONS: Human HEV or a HEV-like agent circulates in the Iowa geographical area. At-risk human populations with occupational exposure to wild animals and environmental sources of domestic animal wastes or with unexplained hepatitis have increased seroprevalence of HEV antibodies.     

衢州地区献血者戊型肝炎流行病学及其亚临床感染和病毒血症情况调查

目的 调查浙江衢州地区戊型肝炎的感染情况.方法 对2006年4月至2007年4月间衢州市中心血站的献血者进行整群抽样,检测抗HEV IgG以及IgM抗体,并对抗HEV IgM阳性的标本进行RT-PCR检测,经测序后分析其基因型及序列同源性.结果 4860例无偿献血者中,HEV IgG阳性率为40.62%,其中男性感染率显著高于女性感染率(43.09%vs.36.09%)(x2=22.6,P＜0.01).感染率随年龄的增长而升高.在抗HEV IgG抗体阳性者中,抗体滴度与年龄、性别并无显著相关性.IgM阳性率为0.43%,IgM阳性的亚临床感染者较IgM阴性的人群有较高的HEV IgG阳性率及抗体滴度(P＜0.05).21例IgM阳性者中发现2例HEV PCR阳性.献血者中病毒血症总阳性率为0.4‰.2例病毒血症者均为HEV Ⅳ型.结论 衢州地区戊型肝炎感染与年龄和性别显著相关,且感染主要发生在成年之后.在献血者中,HEV病毒血症并不罕见.     

Identity of a novel swine hepatitis E virus in Taiwan forming a monophyletic group with Taiwan isolates of human hepatitis E virus

Recently, we found that more than 10% of the cases of acute non-A, non-B, non-C hepatitis in Taiwan were caused by a novel strain of hepatitis E virus (HEV). Since none of these patients had a history of travel to areas where HEV is endemic, the source of transmission remains unclear. The recent discovery of a swine HEV in herd pigs in the United States has led us to speculate that HEV may also circulate in herd pigs in Taiwan and may serve as a reservoir for HEV in Taiwan. Of 275 herd pigs obtained from 10 pig farms in Taiwan, 102 (37%) were seropositive for serum anti-HEV immunoglobulin G (IgG). A 185-bp genomic sequence within the ORF-2 of the HEV genome was amplified and cloned from serum samples of an anti-HEV positive pig and subsequently from serum samples of a patient with acute hepatitis E. Sequence comparison revealed that the swine and human isolates of HEV share 97.3% identity. Phylogenetic analyses further showed that the Taiwan swine and human isolates of HEV form a distinct branch divergent from all other known strains of HEV, including the U.S. swine strain. To examine the potential risk of cross-species transmission of swine HEV to humans, the seroprevalences of anti-HEV IgG in 30 swine handlers, 20 pork dealers, and 50 control subjects were assessed and were found to be 26.7, 15, and 8%, respectively (for swine handlers versus controls, P = 0.048). Our findings may help provide an understanding of the modes of HEV transmission and may also raise potential public health concerns for HEV zoonosis.     

Prevalence of hepatitis E virus among swine and humans in two different ethnic communities in Indonesia

The purpose of this study was to investigate the prevalence of hepatitis E virus (HEV) infection in swine and humans in different environments in Java and Bali, Indonesia. The prevalence of anti-HEV antibodies in people over 20?years old living in communities in Bali was significantly higher than that in Java. While 68.8% and 90.0% of swine in Bali were anti-HEV positive at 1 and 2?months of age, respectively, swine in Java were at significantly lower risk of HEV infection by the age of 2?months. Our present data suggest that substantial differences in swine-breeding conditions and human living environments affect the rate of HEV infection in humans and swine.     

Prevalence of hepatitis E virus infection in multiple transfused Brazilian patients with thalassemia and sickle cell disease

Hepatitis E virus (HEV) is a leading cause of acute hepatitis worldwide. The virus is acquired by fecal-oral route; however, it can also be transmitted by blood transfusion. The objective of the study was to examine anti-HEV immunoglobulin G and HEV RNA prevalence in multiple transfused patients with thalassemia and sickle cell disease (SCD), and in blood donors. The HEV seroprevalence in the patients was 13% (20% in thalassemics; 7.7% in SCD), and 11% in blood donors. No positive result for HEV RNA was obtained. This is a pioneer study examining HEV circulation in Brazilian patients with hemoglobinopathies.     

Hepatitis E virus immunoglobulin G antibodies in different populations in Campinas, Brazil

The seroprevalence of anti-hepatitis E virus (HEV) antibodies was investigated by enzyme immunoassay in 205 volunteer blood donors, 214 women who attended a center for anonymous testing for human immunodeficiency virus (HIV) infection, and 170 hospital employees in Campinas, a city in southeastern Brazil. The prevalence of anti-HEV antibodies ranged from 2.6% (3 of 117) in health care professionals to 17.7% (38 of 214) in women who considered themselves at risk for HIV. The prevalence of anti-HEV antibodies in health care professionals was not significantly different from that in healthy blood donors (3.0%, 5 of 165) and blood donors with raised alanine aminotransferase levels (7.5%, 3 of 40). The prevalence of anti-HEV antibodies (13.2%, 7 of 53) in cleaning service workers at a University hospital was similar to that among women at risk for HIV infection. These results suggest that HEV is circulating in southeastern Brazil and that low socioeconomic status is an important risk factor for HEV infection in this region.     

Molecular and serological survey of hepatitis E virus infection among domestic pigs in Inner Mongolia, China

To evaluate the prevalence and characteristics of swine hepatitis E virus (HEV) infection in Inner Mongolia, China, serum samples obtained from 356 2- to 4-month-old pigs on 14 farms in Inner Mongolia were tested for the presence of anti-HEV antibodies and HEV RNA. Overall, 186 pigs (52%) tested positive for anti-HEV antibodies, while 30 pigs (8%) had detectable HEV RNA levels. The 30 HEV isolates recovered from the viremic pigs were phylogenetically classified into genotype 4 and differed from each other by up to 15.3% in a 412 nt sequence within ORF2. The Inner Mongolian swine HEV strains were most similar to human or swine HEV strains isolated in the other provinces of China but differed by 15.9–18.9% from those in Mongolia (formerly known as Outer Mongolia). These results indicate that farm pigs in Inner Mongolia are frequently infected with markedly divergent genotype 4 HEV strains that may be indigenous to China.     

Clinical and epidemiological implications of swine hepatitis E virus infection

In nonendemic areas, most patients with acute hepatitis E were infected through traveling to endemic areas. However, some patients did not have a history of foreign travel before infection. Furthermore, high seroprevalence rates of antibody to hepatitis E virus (anti-HEV) were found in the general adult population in some countries without any recorded outbreak of hepatitis E. The significance of anti-HEV assay in these subjects remains obscure. To study if swine might be a source of HEV infection, HEV was tested in sera of 235 pigs in Taiwan, and from 5 patients with acute HEV infection who either denied or did not provide any foreign travel history. Three (1.3%) pigs had detectable swine HEV RNA. The swine and human HEV strains from Taiwan formed a monophyletic group, distinct from three previously reported groups: the United States human and swine HEV strains, the Mexico strain, and the largest group composed of the Asian and the African strains. The identity of nucleotide sequences was 84-95% between swine and human HEV strains in Taiwan, and 72-79% between Taiwan strains and those from different areas. The predicted amino acid sequence of a Taiwan swine HEV strain within the peptide 3-2 used in commercial anti-HEV assay showed a high identity (91-94%) with those of other human and swine HEV strains. Swine may be a reservoir of HEV and subclinical swine HEV infection may occur. Cross-reactivity of current anti-HEV assay may account for the high prevalence rate of anti-HEV in the general population in nonendemic areas.