DNA vaccination against hepatitis E virus infection in cynomolgus macaques

Background : The feasibility of DNA vaccination against hepatitis E in non‐human primates has not been evaluated. In the present study a full‐length hepatitis E virus (HEV) open reading frame (ORF)2 (Burmese strain) was assembled, cloned, and used for genetic immunization of cynomolgus macaques (cynos), which were subsequently challenged with a heterologous HEV strain (Mexico). Methods : Four cynos were vaccinated intramuscularly with the HEV ORF2 DNA cassette and one animal was vaccinated with a mock DNA construct. Results : Following vaccination anti‐HEV antibodies were detected in the four HEV‐DNA‐vaccinated cynos, but not in the control animal. When challenged, two of the four HEV‐DNA‐vaccinated cynos were protected against HEV infection and had no elevated alanine aminotransferase activity, viremia, or fecal shedding. The two other DNA‐vaccinated animals developed HEV infection and disease. Conclusion : These findings demonstrate the feasibility of DNA vaccination for the protection of HEV infection and warrant further studies to explore routes other than intramuscular for induction of a stronger and efficacious immune response. © 2002 Blackwell Publishing Asia Pty Ltd     

Hepatitis E virus chimeric DNA vaccine elicits immunologic response in mice

AIM: To construct the plasmid pcHEV23 containing fragments of HEV ORF2 and ORF3 chimeric gene and to assess its ability to elicit specific immunologic response in mice.METHODS: The gene encoding the structural protein of HEV ORF2 fragment and full-length ORF3 was amplified by PCR. The PCR products were cloned into an eucaryotic expression plasmid pcDNA3. The resulting plasmid pcHEV23 was used as a DNA vaccine to inoculate BALB/c mice intramuscularly thrice at a dose of 100 or 200 μg.Mice injected with empty pcDNA3 DNA or saline served as control and then specific immune responses in the mice were detected.RESULTS: After 2-3 times of inoculation, all mice injected with pcHEV23 had anti-HEV IgG seroconversion and specific T lymphocyte proliferation. The lymphocyte stimulation index in the group immunized with pcHEV23(3.1±0.49) was higher than that in the control group (0.787±0.12, P＜0.01). None in the control group had a detectable level of anti-HEV IgG.CONCLUSION: DNA vaccine containing HEV ORF2 and ORF3 chimeric gene can successfully induce specific humoral and cellular immune response in mice.     

Retrospective serological analysis of hepatitis E patients: a long-term follow-up study

The aim of this study was to evaluate the persistence and protective role of antibodies to hepatitis E virus (anti-HEV) after natural hepatitis E infection. A retrospective analysis of immunoglobulin G (IgG) anti-HEV was performed in 37 patients followed-up for 5 years after epidemics of HEV. Two patients with sporadic hepatitis E (HE) were followed-up for 12 and 8 years. All patients infected during epidemics of HE were positive for IgG anti-HEV at 5 years of follow-up (geometric mean titre: 174.75). The two patients with sporadic HE were positive for IgG anti-HEV at the end of 12 and 8 years of follow-up (the IgG anti-HEV titre was 1 : 200 in each patient). This study showed protection against disease by antibodies to HEV. It was therefore concluded that hepatitis E may be preventable by an efficacious vaccine.     

Antibodies against hepatitis E virus in old world monkeys

SUMMARY. To examine whether Indian monkeys are infected with hepatitis E virus (HEV) in nature, serum samples from wild rhesus (Macaca mullata) , bonnet (M. radiata) and langur (Presbytes entellus) monkeys were screened for anti-HEV IgG antibodies in recombinant antigen-based ELISA assays. The positivity rates were 36.7%. 19.1% and 2% respectively. The protection of such antibodies against human HEV was studied in four rhesus monkeys. Of the two rhesus monkeys with anti-HEV titres of 100 and 1000 respectively which were inoculated with the KOL-91 strain of HEV, the former demonstrated a 10-fold rise in anti-HEV titres. Anti-HEV titre in the second rhesus monkey remained unchanged. Neither of the monkeys showed any rise in serum alanine transaminase (ALT) or presence of virus in the faeces, as tested by polymerase chain reaction (PCR). Two other rhesus monkeys with anti-HEV titres of 10000 and 100 respectively were inoculated with the AKL-90 strain of HEV. Serum ALT levels and anti-HEV titres remained unchanged in the first monkey. Excretion of virus in faeces was not noted (PCR). The second monkey developed a typical HEV infection. HEV infection could be produced in anti-HEV negative control monkeys inoculated with both strains of HEV. These results show that either human or simian HEV, or a closely related agent, is circulating among Indian macaques. Titre-dependent protection of naturally occurring anti-HEV antibodies supports this view.     

Seroepidemiology and genetic characterization of hepatitis E virus in western Yunnan Province

Objective:To investigate the seroepidemiology and genetic characterization of hepatitis E virus(HEV) in western Yunnan Province.Methods:Questionnaire survey was conducted among1638 residents in western Yunnan Province using stratified sampling method.Enzyme-linked immunosorbent assay was used to detect serum anti-HEV IgG and IgM.HEV RNA was extracted from patients with serum anti-HEV IgM positive.The open reading flame 2(ORF2) of HEV that was amplified by nested RT-PCR was sequenced and compared with standard HEV genotypes 1-4.Results:Serum anti-HEV positive was found in 13.929(228/1638) residents.The HEV infection rate in males was significantly higher than that in females with a ratio of 1.47(P0.01).20-30 and30-40 years old young men showed the highest incidence.20.57%and 20.78%.respectively.While10-20 and 20-30 years old young women exhibited the highest infection rate,11.85%and 15.60%,respectively.According to occupation,the highest HEV infection rate was observed in farmers(20.35%) and migrants(16.50%).We isolated 10 individual HEV isolates from 31 patients with serum anti-HEV IgM positive.Homology analysis and phylogenetic analysis indicated that these10 HEV isolates belonged to HEV genotype 4 with the homology of 78.65%-94.71%.Conclusions:The HEV infection rate is high in western Yunnan Province.HEV genotype 4 is the leading cause of HEV infection and young farmers and migrants are the main infected population.     

Epidemic of hepatitis E in a military unit in Abbotrabad,Pakistan

An outbreak of hepatitis caused by hepatitis E virus (HEV) in Abbottabad, Pakistan was traced to fecal contamination of a water system. Of 109 men hospitalized with hepatitis, 104 (95%) had serologic evidence of acute hepatitis E (IgM antibody to HEV [anti-HEV]), three (3%) probably had acute hepatitis E (high titers of IgG anti-HEV without IgM), and two had acute hepatitis A. Among a subset of 44 men with acute hepatitis E from whom three serum specimens were obtained over a four-month period, the anti-HEV IgG geometric mean titers (GMTs) decreased from 1,519 during the outbreak to 657 at four months. The IgM anti-HEV was detected in 40 (91%) of 44 sera obtained at admission (GMT = 533 during acute disease), but in only six (14%) four months later. The prevalence of anti-HEV in this population before the outbreak was estimated to be 30%. The presence of IgG anti-HEV appeared to protect against clinical hepatitis or development of serologic evidence of new infection with HEV. This is the second major epidemic of hepatitis E in the Pakistani military confirmed by an anti-HEV enzyme-linked immunosorbent assay (ELISA). Evidence that pre-existing antibody as measured by this ELISA protects against disease is important for assessment of vaccine development.     

Pandemic influenza 1918 H1N1 and 1968 H3N2 DNA vaccines induce cross-reactive immunity in ferrets against infection with viruses drifted for decades

Please cite this paper as: Bragstad et al. (2010) Pandemic influenza 1918 H1N1 and 1968 H3N2 DNA vaccines induce cross‐reactive immunity in ferrets against infection with viruses drifted for decades. Influenza and Other Respiratory Viruses 5(1), 13–23. Background Alternative influenza vaccines and vaccine production forms are needed as the conventional protein vaccines do not induce broad cross‐reactivity against drifted strains. Furthermore, fast vaccine production is especially important in a pandemic situation, and broader vaccine reactivity would diminish the need for frequent change in the vaccine formulations. Objective In this study, we compared the ability of pandemic influenza DNA vaccines to induce immunity against distantly related strains within a subtype with the immunity induced by conventional trivalent protein vaccines against homologous virus challenge. Methods Ferrets were immunised by particle‐mediated epidermal delivery (gene gun) with DNA vaccines based on the haemagglutinin (HA) and neuraminidase (NA) and/or the matrix (M) and nucleoprotein genes of the 1918 H1N1 Spanish influenza pandemic virus or the 1968 H3N2 Hong Kong influenza pandemic virus. The animals were challenged with contemporary H1N1 or H3N2 viruses. Results We demonstrated that DNA vaccines encoding proteins of the original 1918 H1N1 pandemic virus induced protective cross‐reactive immune responses in ferrets against infection with a 1947 H1N1 virus and a recent 1999 H1N1 virus. Similarly, a DNA vaccine, based on the HA and NA of the 1968 H3N2 pandemic virus, induced cross‐reactive immune responses against a recent 2005 H3N2 virus challenge. Conclusions DNA vaccines based on pandemic or recent seasonal influenza genes induced cross‐reactive immunity against contemporary virus challenge as good as or superior to contemporary conventional trivalent protein vaccines. This suggests a unique ability of influenza DNA to induce cross‐protective immunity against both contemporary and long‐time drifted viruses.     

Comparative efficacy of the Schistosoma mansoni nucleic acid vaccine,Sm23, following microseeding or gene gun delivery

Sm23 is an integral membrane protein expressed widely in the human parasitic worm Schistosoma mansoni. Sm23 has already been shown to elicit protective immune responses following immunization with peptides or DNA constructs. In this study, we evaluated the immunogenicity and the protective efficacy of the Sm23 DNA vaccine using two different intradermal DNA delivery methods: microseeding and gene gun. Using both techniques, all mice immunized with the Sm23-pcDNA construct generated Sm23-specific immunoglobulin (Ig)G antibody, while mice immunized with the control plasmid, pcDNA, did not. Antibody isotypes analysis revealed that microseeding elicited mainly IgG2a and IgG2b antibodies, with relatively low levels of IgG1 and IgG3. The relative IgG1/IgG2a ratio was 0.03, indicative of a Th1 type immune response. In contrast, gene gun immunization resulted in significantly higher levels of IgG1 and IgG3. The relative IgG1/IgG2a ratio in this case was 11, indicative of a Th2 type immune response. No significant difference in the levels of IgG2b was observed. Coimmunization with plasmid DNA encoding either interleukin (IL)-12 or IL-4 by microseeding did not affect the levels of IgG1, while the levels of IgG2a and IgG2b were reduced. On the other hand, the levels of IgG3 were significantly increased by IL-4, but unchanged by IL-12. Importantly, in all experiments, the Sm23-pcDNA vaccine provided statistically significant levels of protection against challenge infection. Microseeding immunizations resulted in higher levels of protection (31-34% protection) than gene gun immunization (18% protection). This suggests that the Th1 type immune response elicited by microseeding immunization was responsible for the higher protection levels. However, the protective effect of the vaccine was not affected by coadministering plasmids encoding either IL-12 or IL-4 using the microseeding technique.     

戊型肝炎病毒变异株的血清学特征

探讨戊型肝炎病毒（ＨＥＶ）患者血清学特征。方法用逆转录聚合酶链反应法（ＲＴ－ＰＣＲ）检测ＨＥＶＲＮＡ,并对阳性产物进行克隆和测序;对部分ＨＥＶＲＮＡ阳性者进行追踪并检测抗一ＨＥＶ。结果１５例（２３.４％）为ＨＥＶＲＮＡ阳性,其中９例为典型的中国ＨＥＶ株基因序列,６例变异较大,与典型的中国株基因序列的同源性仅为８０％左右。感染原型ＨＥＶ株的４例中,３例于１月后抗一ＨＥＶ阳转;而２例感染变异ＨＥＶ株的患者于１月或３月时,抗－ＨＥＶ仍为阴性。结论现行的抗一ＨＥＶＥＩＡ试剂尚不能诊断变异的ＨＥＶ株。     

Prevalence of hepatitis E virus in Egyptian children presented with minor hepatic disorders

Hepatitis E virus (HEV) is considered as one of the common causes of particular hepatitis in developing countries. It is transmitted in a fecal-oral manner. It causes sporadic infections and large epidemics. To estimate the prevalence of anti-HEV IgG and IgM antibodies to ORF3 peptide of Hepatitis E virus genome in an age of children, study subjects (100 children) between 6 months and 10 years with minor, hepatic illnesses were recruited for the study during the period from September 2004 to September 2005. Serum anti-HEV IgG and anti-HEV IgM antibodies were screened in all subjects, anti-HEV IgM antibodies were assayed as an indicator of recent infection. Serum transaminases (AST and ALT) were estimated in positive subjects. Out of 100 subjects recruited, 26 subjects (26%) demonstrated anti-HEV IgG and 6 (6 %) were anti-HEV IgM and IgG positive. Anti-HEV IgG were present since the first year of age till 10 years of age and increased with advancing age. Serum transaminases were raised in one (17%) of subjects with anti-HEV IgM antibodies. CONCLUSIONS: Children are susceptible to HEV infection since early infancy. Seropositivity to HEV antibodies increased by over 2 times beyond 4 years of age as compared to younger age.     

Evaluation of heterologous vaginal SHIV SF162p4 infection following vaccination with a polyvalent Clade B virus-like particle vaccine

The vast diversity of HIV-1 infections has greatly impeded the development of a successful HIV-1/AIDS vaccine. Previous vaccine work has demonstrated limited levels of protection against SHIV/SIV infection, but protection was observed only when the challenge virus was directly matched to the vaccine strain. As it is likely impossible to directly match the vaccine strain to all infecting strains in nature, it is necessary to develop an HIV-1 vaccine that can protect against a heterologous viral challenge. In this study we investigated the ability of polyvalent and consensus vaccines to protect against a heterologous clade B challenge. Rhesus macaques were vaccinated with ConB or PolyB virus-like particle vaccines. All vaccines were highly immunogenic with high titers of antibody found in all vaccinated groups against SIV Gag. Antibody responses were also observed against a diverse panel of clade B envelopes. Following vaccination nonhuman primates (NHPs) were challenged via the vaginal route with SHIV(SF162p4). The PolyB vaccine induced a 66.7% reduction in the rate of infection as well as causing a two log reduction in viral burden if infection was not blocked. ConB vaccination had no effect on either the infection rate or viral burden. These results indicate that a polyvalent clade-matched vaccine is better able to protect against a heterologous challenge as compared to a consensus vaccine.     

Novel vaccines against M. tuberculosis

CDC and ACET in U.S.A. reported that novel vaccines instead of BCG are required for the protection against infection of Mycobacterium tuberculosis worldwide. However, no novel vaccine for clinical use has not yet been developed in the world including U.S.A. and Europe. We have developed two novel tuberculosis (TB) vaccines; a DNA vaccine combination expressing mycobacterial heat shock protein 65 (HSP 65) and interleukin-12 (IL-12) by using the hemagglutinating virus of Japan (HVJ)-liposome (HSP 65 + IL-12/HVJ). A mouse IL-12 expression vector (mIL-12 DNA) encoding single-chain IL-12 proteins comorised of p40 and p35 subunits were constructed. In a mouse model, a single gene gun vaccination with the combination of HSP 65 DNA and mIL-12 DNA provided a remarkably high degree of protection against challenge with virulent Mycobacterium tuberculosis; bacterial numbers were 100 fold lower in the lungs compared to BCG-vaccinated mice. To explore the clinical use of the DNA vaccines, we evaluated HVJ-liposome encapsulated HAP 65 DNA and mIL-12 DNA (HSP 65 + mIL-12/ HVJ). The HVJ-liposome method improved the protective efficacy of the HSP 65 DNA vaccine compared to gene gun vaccination. This vaccine provide remarkable protective efficacy in mouse and guinea pig models, as compared to the current by available BCG vaccine. HSP 65 + IL-12/HVJ vaccine induced CD8+cytoxic T lymphocyte activity against HSP 65 antigen. Protective efficacy of this vaccine was associated with the emergence of IFN-gamma-secreting T cells and activation of proliferative T cells as well as CTL induction upon stimulation with the HSP 65 and antigens from M. tuberculosis. Furthermore, we extended our studies to a cynomolgus monkey model, which is currently the best animal model of human tuberculosis, to evaluate the HSP 65 + IL-12/HVJ vaccine. Vaccination with HSP 65 + IL-12/HVJ provided better protective efficacy as assessed by the Erythrocyte Sedimentation Rate, chest X-ray findings, and immune responses than BCG. Most importantly, HSP 65 + IL-12/HVJ resulted in an increased survival for over a year. This is the first report of successful DNA vaccination against M. tuberculosis in the monkey model. Novel TB vaccines using the monkey model will be discussed in this issue. The development of novel vaccines against tuberculosis was also studied in murine and cynomolgus monkey systems. Four distinct methods; DNA vaccination (1. plasmid, 2. adenovirus vector, 3. adenoassouated virus), 4. recombinant BCG, and 5. subunit (recombinant protein) were used for the development of novel vaccines. Genes (HSP 65 gene, IL-12 gene as well as Ag 85A-, 85B-, MPB51-gene) and IL-6 related genes (IL-6 gene + IL-6R gene +gp130 gene) were administered into the Balb/c mice infected (i.v. or intra-tracheal injection) with Mycobacterium tuberculosis (M. tuberculosis). Elimination of M. tuberculosis in lungs, liver, and spleen of these mice and survival were studied in these models. HSP 65 gene + IL-12 gene vaccination, or recombinant BCG (BA51 : Antigen 85B(-) + Antigen 85A(-) + MPB51-gene recombinant BCG) were more prophylactically efficient than parental BCG Tokyo vaccination. In contrast, IL-6 related genes vaccination using adenovirus vector showed therapeutic effect on M. tuberculosis infected mice. Cytotoxic T cells (CTL) activity against M. tuberculosis in the spleen cells from mice treated with IL-6 related genes vaccination were significantly augmented. Furthermore, NOD-SCID-PBL/hu mice treated with anti-IL-2 receptor beta-chain antibody provide an useful tool for analyzing in vivo human T cell immunity against tuberculosis. In conclusion, we demonstrate the development of a novel HVJ-liposome DNA vaccine encapsulating HSP 65 DNA plus IL-12 DNA. These results suggest that HSP 65 + IL-12/HVJ could be a promising candidate for a new tuberculosis DNA vaccine, which is superior to the currently available BCG vaccine. The goal of our study is to develop a new tuberculosis vaccine superior to BCG. To this aim, we believe that the protective efficacy and protective immune responses for vaccine candidates should be addressed in larger animals, such as nonhuman primates, before proceeding to human clinical trials. Although other DNA vaccine candidates that appear to protect against virulent M. tuberculosis in mice better than BCG have failed to provide better protection than BCG in guinea pigs against aerosol challenge of a low dose of virulent M. tuberculosis, some of them are being prepared to enter early human clinical trials. More recently, we evaluated the HSP 65 + hIL-12/HVJ vaccine in the cynomolgus monkey model, which is currently the best non-human primate animal model of human tuberculosis. Monkeys were subsequently challenged with virulent M. tuberculosis by the intra-tracheal route after the third vaccination. This challenge dose normally causes death from acute respiratory infection within 4-6 months. In this particular experiment, monkeys vaccinated with HSP 65 + hIL-12/HVJ induced HSP 65-specific T-cell proliferation and improvement of chest X-P findings, resulting in an increased survival for over a year, superior to BCG group. Thus, we are taking advantage of the availability of multiple animal models (mouse, guinea pig, and monkey) to accumulate essential data of the HVJ-liposome DNA vaccine, including the vaccine efficacy and safety, for up-coming Phase I clinical trials.     

Inactivated whole-virus vaccine derived from a proviral DNA clone of simian immunodeficiency virus induces high levels of neutralizing antibodies and confers protection against heterologous challenge.

We tested the ability of macaques vaccinated with inactivated whole simian immunodeficiency virus (SIV) to resist challenge with either homologous or heterologous cell-free uncloned SIV administered by the intravenous route. The vaccine virus was derived from a proviral DNA clone and thus was considered genetically homogeneous. Sixteen macaques received either hepatitis B surface antigen (n = 6) or the inactivated whole-SIV vaccine (n = 10) at weeks 0, 4, and 49 of the study. All SIV vaccine recipients developed high levels of homologous and heterologous neutralizing antibodies in response to vaccination. At the time of challenge (week 53), vaccinees were further stratified to receive either homologous (n = 10) or heterologous (n = 6) uncloned live SIV. The envelope glycoproteins of the homologous and heterologous challenge viruses were 94% and 81% identical to the vaccine virus, respectively. Regardless of challenge inoculum, all vaccinees in the control group (hepatitis B surface antigen) became infected, whereas all SIV vaccinees were protected against detectable infection. These data support the concept that an efficacious vaccine for HIV might be possible, and suggest that genetic variation of HIV might not be an insurmountable obstacle for vaccine development.     

猪戊型肝炎病毒IgG抗体检测和部分核酸序列分析

目的 了解猪戊型肝炎病毒(HEV)感染情况,探讨猪HEV基因型与人HEV的关系。方法用酶联免疫吸附法(ELISA)和逆转录巢式聚合酶链反应法(RT-nPCR)分别检测猪血清抗-HEV IgG抗体和猪HEV RNA,并用Vector NTI Suite 7和TreeView软件进行人与猪HEV核酸序列和基因进化树分析。结果 猪抗-HEV抗体阳性率为16.67%(18/108),并从18份抗-HEV IgG阳性的猪血清中扩增到2株(11.11%,分别命名为S18和S43)HEV 开放读码框(ORF)1片段(102～387bp),两者核苷酸序列同源性为99%,与HEV基因型1～8的核苷酸序列同源性分别为76%～77%、78%、76%～79%、85%～86%、77%、80%、79%和75%～79%。其中1株(S18)还扩增出HEV ORF2片段(5994～6297bp),与HEV基因型1～4的核苷酸序列同源性分别为76%～78%、74%、74%～77%、85%～94%。结论 分离的2株猪HEV属于HEV基因型4。     

Antigenic determinants of hepatitis E virus and vaccine-induced immunogenicity and efficacy

There is emerging evidence for an under-recognized hepatitis E virus (HEV) as a human pathogen. Among different reasons for this neglect are the unsatisfactory performance and under-utilization of commercial HEV diagnostic kits; for instance, the number of anti-HEV IgM kits marketed in China is about one-fifth of that of hepatitis A kits. Over the last two decades, substantial progress has been achieved in furthering our knowledge on the HEV-specific immune responses, antigenic features of HEV virions, and development of serological assays and more recently prophylactic vaccines. This review will focus on presenting the evidence of the importance of HEV infection for certain cohorts such as pregnant women, the key antigenic determinants of the virus, and immunogenicity and clinical efficacy conferred by a newly developed prophylactic vaccine. Robust immunogenicity, greater than 195-fold and approximately 50-fold increase of anti-HEV IgG level in seronegative and seropositive vaccinees, respectively, as well as impressive clinical efficacy of this vaccine was demonstrated. The protection rate against the hepatitis E disease and the virus infection was shown to be 100 % (95 % CI 75–100) and 78 % (95 % CI 66–86), respectively.     

Relationships among viral diagnostic markers and markers of liver function in acute hepatitis E

Background  Diagnosis of acute hepatitis E has been based in many clinics predominantly on detection of anti-HEV (hepatitis E virus) antibody. Now, new assays have been developed to detect other HEV markers. Our aim was to investigate the relationships among HEV diagnostic markers and liver function markers in acute hepatitis E. Methods  Seventy serum samples were collected from non-A, non-B, non-C acute hepatitis patients and tested for HEV markers (HEV antigen and RNA and anti-HEV IgM) and markers of liver function [alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), total iron binding capacity (TBA), γ-glutamyl transferase (GGT), total bilirubin (TBIL), and direct bilirubin (DBIL)]. Partial open reading frame (ORF) 2 sequences from HEV RNA-positive samples were cloned and analyzed. Results  The concordances between HEV antigen and HEV RNA and between HEV antigen and anti-HEV IgM were 77.1% and 72.9%, respectively, with significant correlations, while that between HEV RNA and anti-HEV IgM was 61.4% with no significant correlation. Eleven of 25 samples negative for anti-HEV IgM were positive for HEV antigen. The ALT, AST, ALP, TBA, GGT, TBIL, and DBIL levels did not differ significantly between the anti-HEV IgM-positive and -negative groups. However, the ALT, AST, ALP, TBA, and GGT levels were significantly higher in the HEV antigen-positive group than in the HEV antigennegative group. All of the HEV isolates cloned belonged to genotype 4. Conclusions  HEV antigen was highly correlated with HEV RNA and elevated ALT, AST, ALP, TBA, and GGT levels. Testing for HEV antigen in combination with anti-HEV IgM is useful for the diagnosis of HEV infection.     

Prevalence of enteric hepatitis A and E viruses in the Mekong River delta region of Vietnam

A study of antibody prevalence for hepatitis A virus (HAV) and hepatitis E virus (HEV) was carried out in southwestern Vietnam in an area adjacent to a known focus of epidemic HEV transmission. The purpose of this investigation was first to provide a prevalence measure of hepatitis infections, and second to determine the outbreak potential of HEV as a function of the susceptible population. Blood specimens collected from 646 persons in randomly selected village hamlets were examined by an ELISA for anti-HEV IgG and anti-HAV IgG. The prevalences of anti-HEV IgG and anti-HAV IgG were 9% and 97%, respectively. There was a significant increase (P < 0.01) in age-specific anti-HEV IgG. A notable increase in anti-HAV IgG prevalence (P < 0.0001) occurred between child populations 0-4 (64%) and 5-9 (95%) years of age. No evidence of familial clustering of anti-HEV IgG-positive individuals was detected, and household crowding was not associated with the spread of HEV. Boiling of water was found to be of protective value against HEV transmission. A relatively low prevalence of anti-HEV indicates considerable HEV outbreak potential, against a background of 1) poor, water-related hygiene/sanitation, 2) dependence on a (likely human/animal waste)-contaminated Mekong riverine system, and 3) periodic river flooding.     

Consecutive evaluation of immunoglobulin M and G antibodies against hepatitis E virus

Hepatitis E virus (HEV) infection is sporadic in the Guangzhou city southern China. However, the evaluation of antibodies to HEV during consecutive time periods after infection has not been reported. We utilized enzyme immunosorbent assay (ELISA) to detect IgM and IgG anti-HEV in consecutive serum specimens from patients with acute hepatitis E and compared that data with detection rates of IgM and IgG anti-HAV in patients with acute hepatitis A. IgM anti-HEV can be detected as early as 4 days after onset of disease symptoms in some patients. The detection rate of IgM anti-HEV is significantly higher in specimens collected within 4 weeks (95%) of onset than in those specimens collected 4 to 18 weeks after onset (67.6%) (P<0.005). IgM anti-HEV had a similar pattern to IgM anti-HAV and can be used as a marker of acute HEV infection. In contrast with IgG anti-HAV, 56.8% of the specimens did not contain detectable levels of IgG anti-HEV (P<0.005). One should be cautioned against making a diagnosis of HEV infection solely by the currently available assays for IgG anti-HEV. In conclusion, IgM anti-HEV can be used as a reliable and sensitive marker for recent HEV infection, but serum specimens should be collected within 4 weeks after onset of symptoms to avoid false-negative results. In contrast, we should be aware of the failure to develop IgG anti-HEV in some patients. These patients carry the risk of reinfection.