Double-antigen enzyme-linked immunosorbent assay for detection of hepatitis E virus-specific antibodies in human or swine sera

Hepatitis E virus in wild and domestic rabbits from Portugal: a combined molecular and longitudinal serological study

Hepatitis E virus (HEV), species Paslahepevirus balayani, poses a global public health threat, especially in developing countries, by causing acute enterically transmitted hepatitis. HEV infects various mammalian hosts and belongs to the genus Paslahepevirus in the family Hepeviridae. While swine are recognized as the main hosts of HEV, rabbits, which can also be affected by swine HEV-3 related strains, serve as the primary reservoir for the distinct emerging and zoonotic HEV-3ra subtype. In Portugal, where the European wild rabbit is abundant, their role in HEV epidemiology remains unclear. The primary aim of the present research was to evaluate the circulation and the potential for HEV infection within these species. This study employed a molecular and longitudinal serological approach to investigate HEV in Portuguese rabbits. Among the 205 wild rabbits tested, a seroprevalence of 2.44% (95% CI: 0.80-5.60) was found, with no significant associations with age, sex, localization, or sampling dates. Seropositive animals were found in the south and center regions of the country. HEV RNA was not detected in 120 fecal samples, suggesting a natural, low level, and widespread viral circulation. The study underscores the need for further research to comprehend HEV dynamics in these species, which is crucial for assessing potential transmission risks to humans.

Serological and Molecular Survey of Hepatitis E Virus in Small Ruminants from Central Portugal

Hepatitis E virus (HEV) is currently recognized as an emerging problem and a growing concern for public health in developed countries, with HEV infections mainly attributable to foodborne transmission of HEV-3. The zoonotic HEV genotype 3 infects a wide range of mammalian hosts, with swine considered as the primary host. This study investigates the occurrence of HEV among small ruminants in Portugal. The primary aim of the present research was to evaluate the circulation and the potential for HEV infection among sheep and goats. A total of 400 bile samples and 493 blood samples were collected from sheep and goats at a slaughterhouse in the center region of Portugal, between January 2022 and March 2023. The HEV RNA detection in bile samples was performed using a nested broad-spectrum RT-PCR targeting the ORF1 region. Serological analysis to detect anti-HEV antibodies was conducted using a commercial double-antigen sandwich multi-species ELISA. The HEV RNA was not detected in any bile samples using the nested broad-spectrum RT-PCR. Serological analysis revealed an overall HEV antibody seroprevalence of 2% (10/493, 95% CI: 0.98-3.70) among the small ruminants, namely 2.2% in goats and 2.0% in sheep. Curiously, no statistically significant association among the factors, age, sex and species and HEV seroprevalence was observed. Although HEV RNA was not detected in the bile of sheep and goats, this study the evidence of seroprevalence in these small ruminant species. Further research could provide additional insights into the factors influencing HEV transmission dynamics in small ruminants in Portugal and its potential implications for public health.

Epidemiological survey and risk factors associated with Paslahepevirus balayani in equines in Europe

Paslahepevirus balayani (HEV) is an important emerging zoonotic virus in Europe. Although domestic pigs and wild boar are the main reservoirs of this pathogen, susceptibility to this virus has been confirmed in a growing number of animal species, including equines. However, their role in the epidemiology of this virus remains poorly understood. Our aim was to assess HEV circulation and identify potential risk factors associated with exposure in equid species in different European countries. A total of 596 equines, including 496 horses, 63 donkeys and 37 mules/hinnies bred in four European countries (Spain, Italy, United Kingdom and Ireland) were sampled. Thirty-three animals (5.5%; 95%CI: 3.7-7.4) had anti-HEV antibodies. Seropositivity was found in 4.6% of horses, 11.1% of donkeys and 8.1% of mules/hinnies tested. By country, 6.3%, 5.4%, 5.0% and 4.0% of the equines sampled in Spain, Italy, United Kingdom and Ireland, respectively, were seropositive, respectively. Statistical analysis showed that "species" and "drinking water from ponds and streams" were potential risk factors associated with HEV seropositivity in equines in Europe. HEV RNA was not detected in any (0.0%; 95%CI: 0.0-1.8) of the 202 equines tested. Our results provide evidence of a low, spatially homogeneous and widespread viral circulation that is not equal across species in equid populations in the European countries analyzed and indicate that these species appear to play a limited role in the epidemiology of this virus. Further studies are required to elucidate the differences in seroprevalence between donkeys, mules/hinnies and horses and to determine the risk of zoonotic transmission of this pathogen from equid species.

Unraveling swine hepatitis E in the central region of Argentina through ELISA development and epidemiological insights

Hepatitis E virus (HEV) is a public health concern globally, causing acute viral hepatitis in humans. Genotype-3 HEV (HEV-3), the most frequently genotype detected in South America, is zoonotic and the main reservoirs are the domestic pig and wild boar. Circulation of HEV-3 in Argentina has been confirmed in humans as well as in pig herds, wild boar and environmental waters. However, data are scarce mainly due to the inaccessibility of serological assays in this country. In order to provide insights in the epidemiology of HEV in swine in Argentina, we developed an indirect ELISA based on the native recombinant protein ORF2 and conducted a serological survey to determine the prevalence of seropositive swine in small-scale pig farms in the central region of Argentina. The method was evaluated in a panel of 157 serum samples, resulting in relative sensitivity of 98.6 % (95 % CI 95 %-100 %) and relative specificity of 97.7 % (95 % CI 94 %-100 %) compared to a commercial test. An almost perfect agreement was obtained between the two tests (Kappa index of 0.961). A survey on 294 samples from 49 small-scale farms resulted in a seropositivity rate of 54 %. Seropositive animals were found in 34 out of 49 (69.4 %) farms. Most of the farms (70.6 %) had over 50 % of seropositive animals. The wide spreading of HEV in the swine population of Tandil, Argentina, underscore the need to better understand the epidemiology of HEV in the region, enabling the implementation of targeted interventions to mitigate the impact of this virus on public health.

First serological and molecular investigation of hepatitis E virus infection in dromedary camels in Algeria

Hepatitis E is an acute self-limited or fulminant infection in humans, caused by the hepatitis E virus (HEV). This member of the Hepeviridae family has been identified in a wide range of domestic and wild animals all over the world, with a possible transmission to humans through fecal oral route, direct contact and ingestion of contaminated meat products, making it one of the global zoonotic and public health major concerns. Since there is no monitoring program and a lack of data on HEV in animals in Algeria, the current preliminary survey has been undertaken to elucidate the exposure to the virus in camels at abattoirs of six southern provinces of Algeria. Two-hundred and eight sera/plasma were collected and analyzed (by double antigen sandwich ELISA) for the presence of total anti-HEV antibodies, among which 35.1% were positive, but no HEV RNA could be isolated from them (by two pan-HEV nested RT-PCR and broad range real-time reverse transcription RT-PCR). The univariate analysis showed significant associations (p < 0.05) between HEV seroprevalence and province of origin, age, and sex of camels, whereas the multivariable logistic regression analysis revealed a negative impact of camels' age on it. The obtained results confirm that HEV infection is widespread established in the camelid population of Algeria.

A multispecies competitive nanobody-based ELISA for the detection of antibodies against hepatitis E virus

The hepatitis E virus (HEV) is an emergent zoonotic virus causing viral hepatitis worldwide. Clinically, hepatitis E is not easily distinguished from other types of acute viral hepatitis. There is a need for HEV diagnostic assays to detect and prevent interspecies transmission among susceptible populations. Nanobodies (Nbs) are expressed recombinantly in different systems, produced with high yields, and have superior physicochemical properties compared with conventional antibodies (Ab). Several Nbs against ORF2, the capsid protein and main antigen, were selected and produced in E. coli. Nb39 and Nb74 specifically recognized HEV ORF2 (genotypes 3 and 4). A competitive ELISA (cELISA) was developed and validated using a reference panel of human (n = 86) and swine sera (n = 116) tested in comparison with a commercial kit. The optimal cutoff values determined by ROC analysis were 69.16% (human) and 58.76% (swine); the sensitivity and specificity were high: 97.4% (95% CI 86.5-99.5%) and 95.8% (95% CI 86.0-98.8%) for human vs. 100% (95% CI 93.5-100%) and 98.3% (95% CI 91.0-99.7%) for swine. Further, the cELISA detected total anti-HEV antibodies in wild boar, deer, and mice. To our knowledge, this is the first report of production of Nbs against HEV-3 ORF2 for diagnostic purposes.

Sero-prevalence of Newcastle disease and associated risk factors in chickens at backyard chicken production Kindo Koisha, Wolaita zone, Southern Ethiopia

Newcastle disease (ND) is a serious infectious disease of poultry caused by virulent strains of Avian Paramyxovirus-1 and has a substantial impact on villages where people's livelihood depends upon poultry farming in several developing countries including Ethiopia. In the district of the study area, no previous studies have been conducted. Thus, the aim of the present study was to estimate individual and household flock level seroprevalence and risk factors for ND in unvaccinated backyard chickens in Kindo Koisha district, Wolaita zone, Ethiopia. A cross-sectional study design was conducted. For the study, household flocks were sampled as a cluster, and backyard chickens within the cluster with an age of more than 3 months were sampled. A total of 598 blood samples were collected from 86 household flocks during the study period. Serum samples were tested for ND antibodies using an Indirect-Enzyme Linked Immuno Sorbent Assay. The overall seroprevalence of ND virus at individual and flock level was 17.06% (95% CI: 14.25-20.29%) and 73.26% (95% CI: 62.79-81.64%), respectively. The ND seropositivity and associated risk factors were assessed at the individual bird and flock level by using ordinary and mixed effect logistic regression, respectively. Ordinary logistic regression revealed that crossbreed chickens had significantly higher odds of ND seropositivity than local breeds, with an odds ratio of 2.15 (95% CI: 1.54-3.00; p < 0.001). The odds of ND seropositivity was significantly higher in backyard chickens which belongs flock size >9 in comparison to <9 with an odds ratio of 3.7 (95% CI: 1.12-12.30; p < 0.031). The potential flock level risk factors related to ND seropositivity in this study were flock size, chicken house cleaning frequency, water source for chickens, dead chicken disposal practice, and distance to the next neighbor household, mixing with wild birds and owning pets. In conclusion, the current study generates significant information on the seroprevalence and the potential risk factors associated with ND at individual and flock level in Kindo Koisha district, Wolaita zone. Consequently, ND vaccination campaigns should be launched, and effective extension programs should also be provided to raise awareness about the disease.

Laboratory Diagnosis of HEV Infection

Serological and nucleic acid tests for detecting hepatitis E virus (HEV) have been developed for both epidemiologic and diagnostic purposes. The laboratory diagnosis of HEV infection depends on the detection of HEV antigen or HEV RNA in the blood, stool, and other body fluids, and serum antibodies against HEV (immunoglobulin [Ig]A, IgM, and IgG). Anti-HEV IgM antibodies and low avidity IgG can be detected during the acute phase of the illness and can last approximately 12 months, representing primary infection, whereas anti-HEV IgG antibodies can last more than several years, representing remote exposure. Thus, the diagnosis of acute infection is based on the presence of anti-HEV IgM, low avidity IgG, HEV antigen, and HEV RNA, while epidemiological investigations are mainly based on anti-HEV IgG. Although significant progress has been made in developing and optimizing different formats of HEV assays, improving their sensitivity and specificity, there are many shortcomings and challenges in inter-assay concordance, validation, and standardization. This article reviews the current knowledge on the diagnosis of HEV infection, including the most common available laboratory diagnostic techniques.

Development and evaluation of recombinant E2 protein based IgM capture enzyme-linked immunosorbent assay (ELISA) and double antigen sandwich ELISA for detection of antibodies to Chikungunya virus

BACKGROUND

Chikungunya virus (CHIKV) reemerged and caused millions of human infections since 2004. The disease could be established, when the virus has been introduced to areas where the appropriate vectors are endemic. The differential diagnosis of CHIKV infection varies based on place of residence, travel history, and exposures. Serological tests are commonly used to diagnose CHIKV infection, but their availability and assessments of the performance of the diagnostics have been limited.

OBJECTIVES

To develop and evaluate antibodies detection methods for chikungunya diagnosis and serological investigation.

METHODS

Recombinant E2 protein based IgM capture enzyme-linked immunosorbent assay (Mac-ELISA) and double antigen sandwich ELISA (Das-ELISA) for detection of antibodies to Chikungunya virus were developed and evaluated. The repeatability was evaluated by testing of three reference sera at single dilutions in triplicated for 5 times. The sensitivity, specificity, accuracy, and agreement of the MAC-ELISA and Das-ELISA were obtained by comparing the detection results of 225 serum samples (45 positive; 180 negative) with a real-time RT-PCR assay and an IFA commercial tests manufactured by Euroimmun.

RESULTS

The established ELISA assays were standardized by determining the optimal concentrations of the key reagents. The coefficient values of repeat testing were within 10% and 20% for intraassay and interassay precision, respectively. A sensitivity of 60.0% and 52.5%, a specificity of 96.2% and 96.8%, and an accuracy of 89.8% and 88.9% were obtained for the Mac-ELISA and Das-ELISA, respectively, when compared to a CHIKV qRT-PCR method. And a sensitivity of 100%, a specificity of 97.5% and 99.5%, and an accuracy of 97.8% and 99.6% were yielded respectively when using the IIFT as a reference method, which showed a highly consistence to the commercial IIFT assay with a Kappa value greater than 0.90.

CONCLUSIONS

The Mac-ELISA and Das-ELISA based on recombinant E2 protein of CHIKV were developed and standardized, which could detect IgM or total antibodies against CHIKV in 2-3 hours with acceptable sensitivities and specificities. These assays can be used for laboratory diagnosis and serological investigation of CHIKV infections to evaluate the risk of CHIKV transmission.

Serological, Virological Investigation and Hepatic Injury Evaluation for Hepatitis E Virus in Hunting Dogs

Hepatitis E virus (HEV) is a quasi-enveloped single-stranded positive-sense RNA virus belonging to the Orthohepevirus A genus within the Hepeviridae family. The most common transmission route of this virus is fecal–oral, although zoonotic transmission by contact with infected animals has also been described. In this study, 80 sera and rectal swabs were collected from dogs during the 2019/2020 and 2020/2021 wild boar hunting season in Tuscany. All dogs were submitted for serological screening to detect the presence of anti-HEV antibodies. To evaluate the circulation of HEV, rectal swabs from both seropositive dogs and dogs living in the same kennels were examined by One-Step RT-qPCR. In addition, the presence of markers of hepatic damage in dogs’ sera was investigated. Results indicated the presence of anti-HEV antibodies in 4/80 subjects (5%). However, neither HEV RNA nor signs of hepatic damage were found. In conclusion, although HEV can stimulate a specific immuno-response in dogs, this species does not seem to play an important role in HEV epidemiology.

Epidemiological survey and risk factors associated with hepatitis E virus in small ruminants in southern Spain

Autochthonous cases of hepatitis E (HE) associated with zoonotic genotypes HEV-3 and HEV-4 have significantly increased in industrialized countries over the last decade. Suidae are generally recognized as the main reservoirs of these genotypes. Susceptibility to HE virus (HEV) infection and zoonotic potential have also been confirmed in other species, including sheep and goat. However, the information about their role in the epidemiology of HEV remains very scarce. The objective of this study was to assess the prevalence, spatial distribution and risk factors associated with HEV exposure in sheep and goats in southern Spain, the country with the highest census of small domestic ruminants in the European Union. Blood samples from 240 sheep and 240 goats were collected between 2015 and 2017. Sera were analysed in parallel using a commercial double-antigen ELISA and real-time PCR. A total of 38 (7.9%; 95%CI: 5.5-10.3) out of 480 sampled animals showed anti-HEV antibodies. By species, the seroprevalences found in sheep and goats were 2.1% (5/240; 95%CI: 0.3-3.9) and 13.8% (33/240; 95%CI: 9.4-18.1) respectively. Anti-HEV antibodies were found on 19 (59.4%; 95%CI: 42.4-76.4) of the 32 sampled farms. The GEE model showed that species (goat) and number of small ruminants in the farm (≤348 animals and ≥538 animals) were risk factors potentially associated with HEV exposure in small ruminants in the study area. HEV RNA was not detected in any of the 480 (0.0%; 95%CI: 0.0-0.8) tested animals. Our results confirm that sheep and goats are naturally, but not equally exposed to HEV and indicate the widespread spatial distribution of HEV among small ruminant populations in southern Spain. Further studies are required to elucidate the role of sheep and goat in the epidemiology of HEV and their potential implications for public health.

Double-antigen sandwich ELISA based on chimeric antigens for detection of antibodies to Trypanosoma cruzi in human sera

Background

Enzyme-linked immunosorbent assays (ELISA) are generally the chosen test for Chagas disease (CD) diagnosis; however, its performance depends on the antigen preparation adsorbed to the solid phase, which may lead to false-positive results and cross-reactions. The use of chimeric recombinant antigens can overcome this limitation. Four chimeric antigens from Trypanosoma cruzi (IBMP-8.1, IBMP-8.2, IBMP-8.3 and IBMP-8.4) were developed and evaluated in phase I, II and III studies using indirect ELISA as diagnostic platform. However, peroxidase-labeled secondary anti-human IgG antibody, which is employed in indirect ELISAs, limits its use for the detection of species-specific and class-specific antibodies. To overcome this limitation, peroxidase-labeled antigens can be utilized, diagnosing both acute or chronic infection, in a species and immunoglobulin class-independent manner, through the use of a double-antigen sandwich ELISA (DAgS-ELISA). We aimed to evaluate and validate the diagnostic performance of the chimeric antigens IBMP-8.1, IBMP-8.2, IBMP-8.3 and IBMP-8.4 in the DAgS-ELISA platform.

Methodology/Principal findings

DAgS-ELISA was optimized by checkerboard titration. In phase I study, 207 positive and 205 negative samples were evaluated. Cross-reactivity to other infections was also assessed using 68 samples. The selected conditions for the tests utilized 25 ng of antigen per well and the conjugate diluted at 1:2,000 for all molecules. In the phase I study, the areas under the curve of IBMP-8.1, IBMP-8.2, IBMP-8.3 and IBMP-8.4 were 98.7%, 99.5%, 98.6% and 98.8%, respectively. Among the positive samples, IBMP-8.1 antigen classified 53 (25.6%) as false negative, IBMP-8.2, 27 (13%), IBMP-8.3, 24 (11.6%) and IBMP-8.4, 43 (20.8%), giving sensitivities of 74.4%, 87%, 88.4% and 79.2%, respectively. The only antigen that did not reach 100% specificity was IBMP-8.3, with 96.6%. IBMP-8.3 was also the only molecule to show cross-reactivity with HTLV.

Conclusions/Significance

DAgS-ELISA is a promising tool for immunodiagnosis, and despite the high AUC values, the performance of this assay was different from the values obtained by our group when using these antigens in the indirect ELISA, for this reason, improvements are being considered to increase the sensitivity of the DAgS-ELISA.

Indirect immunoassays are the recommended method for chronic Chagas disease diagnosis and its performance relies on the employed antigen preparation. Chimeric antigens have been successfully utilized for chronic CD in vitro diagnosis and efficiently addresses commonly encountered hurdles arising from the use of recombinant and native antigens. Thus, our group developed four Trypanosoma cruzi chimeric antigens and evaluated their diagnostic potential in an indirect Enzyme-linked immunosorbent assays (ELISA) design; however, this design restricts detection to a single antibody class and for a single species. To overcome this, we utilized conjugated antigens in a double-antigen sandwich ELISA (DAgS-ELISA) design, which is able to detect both acute and chronic infections, in a species and immunoglobulin class-independent manner. Despite their high discrimination levels, as illustrated through elevated AUC values, our results were different from those obtained previously, especially regarding sensitivity. Specificity values remained elevated, reaching 100% for 3 out of 4 antigens. As such, improvements are being considered to increase the sensitivity of the DAgS-ELISA.

Serological and molecular survey of hepatitis E virus in cats and dogs in Spain

Hepatitis E virus (HEV) is an emerging zoonotic pathogen that is currently recognized as one of the major causes of acute human hepatitis worldwide. In Europe, the increasing number of hepatitis E cases is mainly associated with the consumption of animal food products or contact with infected animals. Dogs and cats have been suggested as a zoonotic source of HEV infection. The aim of this study was to assess Orthohepevirus circulation, including HEV-A, HEV-B and HEV-C species, in sympatric urban cats and dogs in southern Spain. Between 2017 and 2020, blood samples were collected from 144 stray cats and 152 dogs, both strays and pets. The presence of antibodies against HEV were tested using a double-antigen sandwich ELISA and seropositive samples were further analyzed by western blot. A RT-PCR was performed to detect RNA of Orthohepevirus species (HEV-A, HEV-B and HEV-C). A total of 19 (6.4%; 95%CI: 3.6-9.2) of the 296 animals tested showed anti-HEV antibodies by ELISA. Seropositivity was significantly higher in dogs (9.9%; 15/152; 95%CI: 5.1-14.6) than in cats (2.8%; 4/144; 95%CI: 0.1-5.5). Ten out of the 18 ELISA-positive animals that could be further analyzed by western blot, reacted against HEV-3 and/or HEV-C1 antigens, which suggest circulation of both genotypes in urban cats and dogs in the study area. However, HEV-A, HEV-B and HEV-C RNA was not detected in any of the tested sera. This is the first study to assess HEV circulation in both stray cats and dogs in Europe. Our results provide evidence of HEV exposure in sympatric urban cat and dog populations in southern Spain. Further studies are needed to determine the role of these species in the epidemiology of HEV. This article is protected by copyright. All rights reserved.

Vertical Flow Cellulose-Based Assays for SARS-CoV-2 Antibody Detection in Human Serum

Rapid and inexpensive serological tests for severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) antibodies are essential to conduct large-scale seroprevalence surveys and can potentially complement nucleic acid or antigen tests at the point of care. During the COVID-19 pandemic, extreme demand for traditional lateral flow tests has stressed manufacturing capacity and supply chains. Motivated by this limitation, we developed a SARS-CoV-2 antibody test using cellulose, an alternative membrane material, and a double-antigen sandwich format. Functionalized SARS-CoV-2 antigens were used as both capture and reporter binders, replacing the anti-human antibodies currently used in lateral flow tests. The test could provide enhanced sensitivity because it labels only antibodies against SARS-CoV-2 and the signal intensity is not diminished due to other human antibodies in serum. Three-dimensional channels in the assay were designed to have consistent flow rates and be easily manufactured by folding wax-printed paper. We demonstrated that this simple, vertical flow, cellulose-based assay could detect SARS-CoV-2 antibodies in clinical samples within 15 min, and the results were consistent with those from a laboratory, bead-based chemiluminescence immunoassay that was granted emergency use approval by the US FDA.

Advances in Hepatitis E Virus Biology and Pathogenesis

Hepatitis E virus (HEV) is one of the causative agents for liver inflammation across the world. HEV is a positive-sense single-stranded RNA virus. Human HEV strains mainly belong to four major genotypes in the genus Orthohepevirus A, family Hepeviridae. Among the four genotypes, genotype 1 and 2 are obligate human pathogens, and genotype 3 and 4 cause zoonotic infections. HEV infection with genotype 1 and 2 mainly presents as acute and self-limiting hepatitis in young adults. However, HEV infection of pregnant women with genotype 1 strains can be exacerbated to fulminant hepatitis, resulting in a high rate of case fatality. As pregnant women maintain the balance of maternal-fetal tolerance and effective immunity against invading pathogens, HEV infection with genotype 1 might dysregulate the balance and cause the adverse outcome. Furthermore, HEV infection with genotype 3 can be chronic in immunocompromised patients, with rapid progression, which has been a challenge since it was reported years ago. The virus has a complex interaction with the host cells in downregulating antiviral factors and recruiting elements to generate a conducive environment of replication. The virus-cell interactions at an early stage might determine the consequence of the infection. In this review, advances in HEV virology, viral life cycle, viral interference with the immune response, and the pathogenesis in pregnant women are discussed, and perspectives on these aspects are presented.

A multi-target lateral flow immunoassay enabling the specific and sensitive detection of total antibodies to SARS COV-2

A rapid test for detecting total immunoglobulins directed towards the nucleocapsid protein (N) of severe acute syndrome coronavirus 2 (SARS CoV-2) was developed, based on a multi-target lateral flow immunoassay comprising two test lines. Both test lines bound to several classes of immunoglobulins (G, M, and A). Specific anti-SARS immunoglobulins were revealed by a colorimetric probe formed by N and gold nanoparticles. Targeting the total antibodies response to infection enabled achieving 100% diagnostic specificity (95.75-100, C.I. 95%, n = 85 healthy and with other infections individuals) and 94.6% sensitivity (84.9-98.9, C.I. 95%, n = 62 SARS CoV-2 infected subjects) as early as 7 days post confirmation of positivity. Agreeing results with a reference serological ELISA were achieved, except for the earlier detection capability of the rapid test. Follow up of the three seroconverting patients endorsed the hypothesis of the random rise of the different immunoglobulins and strengthened the 'total antibodies' approach for the trustworthy detection of serological response to SARS CoV-2 infection.

Development and evaluation of a double-antigen sandwich ELISA to identify Anaplasma marginale-infected and A. centrale-vaccinated cattle

Bovine anaplasmosis is a worldwide infectious disease caused by the intraerythrocytic bacterium Anaplasma marginale, which is transmitted by ticks and fomites. A. centrale is a less virulent subspecies used as a live vaccine in cohorts of 8- to 10-mo-old calves that did not naturally reach enzootic stability. We developed 3 variants of a double-antigen sandwich ELISA (dasELISA) using a recombinant major surface protein 5 (MSP5) from A. marginale (dasELISAm) or from A. centrale (dasELISAc) or using MSP5 from both organisms (dasELISAmc). Each dasELISA was tested for the detection of antibodies against A. marginale and A. centrale. The tests were validated using serum samples from cattle not infected with Anaplasma spp. (n = 388), infected with A. marginale (n = 436), and vaccinated with A. centrale (n = 358), confirmed by nested PCR. A total of 462 samples were compared with a commercial competitive ELISA (cELISA). For dasELISAm, dasELISAc, and dasELISAmc, specificities were 98.7%, 98.7%, and 97.4%, and overall sensitivities were 92.6%, 85.7%, and 97.4%, respectively. For A. marginale-infected and A. centrale-vaccinated cattle, sensitivities were 97.7% and 86.3% for dasELISAm, and 77.7% and 95.5% for dasELISAc, respectively. Sensitivity of dasELISAmc was similar for both groups (>96%). The agreement rate between dasELISAmc and cELISA was 96.3% (κ = 0.92); the former test allowed earlier detection of seroconversion of vaccinated cattle than did cELISA. Based on these results, the test could be used to 1) determine the enzootic stability or instability of anaplasmosis in calves, 2) conduct epidemiologic studies, and 3) evaluate the immunogenicity of A. centrale live vaccine.

Low Serologic Prevalences Suggest Sporadic Infections of Hepatitis E Virus in Chamois (Rupicapra rupicapra) and Red Deer (Cervus elaphus) in the Italian Alps

Hepatitis E virus (HEV) is a worldwide public health concern, with an increase in human autochthonous cases in Europe. Although domestic pigs and wild boar (Sus scrofa) are the main reservoirs of HEV, the constant expansion of wild ruminants increases the potential for HEV transmission. We investigated HEV infection in chamois (Rupicapra rupicapra) and red deer (Cervus elaphus) in the Italian Alps using an enzyme-linked immunosorbent assay (ELISA). We detected HEV antibodies from 2013 to 2015 in both host species, with seroprevalences of 1.2% and 0.8% in chamois and red deer, respectively. All serum samples that were positive to HEV antibodies by ELISA were negative when tested by real-time reverse-transcriptase PCR to detect HEV RNA. The observed low seroprevalence of HEV suggested a sporadic circulation of HEV in the alpine environment, and it was consistent with the low seroprevalence observed in wild boar in the Alps. Our observations supported the role of chamois and red deer as spillover hosts of HEV infections in the Italian Alps.

Natural viral co-infections in pig herds affect hepatitis E virus (HEV) infection dynamics and increase the risk of contaminated livers at slaughter

Hepatitis E virus (HEV) is a zoonotic pathogen, in particular genotype 3 HEV is mainly transmitted to humans through the consumption of contaminated pork products. This study aimed at describing HEV infection patterns in pig farms and at assessing the impact of immunomodulating co-infections namely Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) and Porcine Circovirus Type 2 (PCV2), as well as other individual factors such as piglets' immunity and litters' characteristics on HEV dynamics. A longitudinal follow-up was conducted in three farrow-to-finish farms known to be HEV infected. Overall, 360 piglets were individually monitored from birth to slaughter with regular blood and faecal sampling as well as blood and liver samples collected at slaughterhouse. Virological and serological analyses were performed to detect HEV, PCV2 and PRRSV genome and antibodies. The links between 12 explanatory variables and four outcomes describing HEV dynamics were assessed using cox-proportional hazard models and logistic regression. HEV infection dynamics was found highly variable between farms and in a lower magnitude between batches. HEV positive livers were more likely related to short time-intervals between HEV infection and slaughter time (<40 days, OR = 4.1 [3.7-4.5]). In addition to an influence of piglets' sex and sows' parity, the sequence of co-infections was strongly associated with different HEV dynamics: a PRRSV or PCV2/PRRSV pre- or co-infection was associated with a higher age at HEV shedding (Hazard Ratio = 0.3 [0.2-0.5]), as well as a higher age at HEV seroconversion (HR = 0.5 [0.3-0.9] and HR = 0.4 [0.2-0.7] respectively). A PCV2/PRRSV pre- or co-infection was associated with a longer duration of shedding (HR = 0.5 [0.3-0.8]). Consequently, a PRRSV or PCV2/PRRSV pre- or co-infection was strongly associated with a higher risk of having positive livers at slaughter (OR = 4.1 [1.9-8.9] and OR = 6.5 [3.2-13.2] respectively). In conclusion, co-infections with immunomodulating viruses were found to affect HEV dynamics in the farrow-to-finish pig farms that were followed in this study.

Construction of an HRP-streptavidin bound antigen and its application in an ELISA for porcine circovirus 2 antibodies

A fusion protein SBP-Cap∆41, consisting of Cap∆41 (without 41 amino acids at the N-terminus) protein of porcine circovirus 2 (PCV2) and a streptavidin binding peptide (SBP), was constructed. This fusion protein binds to HRP-labeled streptavidin (HRP-SA) through high affinity between SBP and SA, forming an HRP-streptavidin bound antigen (Hsb-Ag) with both immunoreactivity and enzymatic activity, which can be used in a double-antigen sandwich ELISA for detection of PCV2 antibodies. Comparison of the characteristics of the HSb-Cap∆41 and chemical conjugates of the recombinant Cap∆41 protein showed that the HSb-Cap∆41 based double-antigen sandwich ELISA (HBDS-ELISA) had higher specificity and sensitivity. Use of the HBDS-ELISA detected PCV2-IgG in 9 injected pigs as early as 10 days p.i., 3 days earlier than both a double-antigen sandwich ELISA (DS-ELISA) based on a chemically conjugated antigen, and a commercial indirect ELISA kit.

Laboratory Diagnosis of HEV Infection

Serological and nucleic acid tests for detecting hepatitis E virus (HEV) have been developed for both epidemiologic and diagnostic purposes. The laboratory diagnosis of HEV infection depends on the detection of HEV antigen, HEV RNA, and serum antibodies against HEV (immunoglobulin [Ig]A, IgM, and IgG). Anti-HEV IgM antibodies can be detected during the acute phase of the illness and can last approximately 4 or 5 months, representing recent exposure, whereas anti-HEV IgG antibodies can last more than 10 years, representing remote exposure. Thus, the diagnosis of acute infection is based on the presence of anti-HEV IgM, HEV antigen, and HEV RNA, while epidemiological investigations are mainly based on anti-HEV IgG. Although significant progress has been made in developing and optimizing different formats of HEV assays, improving their sensitivity and specificity, there are many shortcomings and challenges in inter-assay concordance, validation, and standardization. This article reviews the current knowledge on the diagnosis of HEV infection, including the most common available laboratory diagnostic techniques.

Hepatitis E virus in bottlenose dolphins Tursiops truncatus

Hepatitis E virus (HEV) infects several animal species that act as zoonotic reservoirs for viral transmission. Solid and liquid residues from infected animals could lead to HEV contamination of food and surface waters. Evidence of human HEV infection through ingestion of seafood (shellfish, mussels) has been reported. Dolphins generally feed on fish and squid but are able to adapt to an environment and consume whatever prey is available. Clinical signs of infected dolphins include lethargy, inappetence, behavioral aberrations and increased serum alanine aminotransferase (ALT). The dolphins examined in this study were maintained at the National Aquarium, Havana, Cuba. A total of 31 dolphins were evaluated for HEV markers. Sera were collected and screened for total immunoglobin (Ig) anti-HEV. Sera and liver homogenate were tested for HEV RNA by nested RT-PCR using primers targeting the open reading frame 1. Phylogenetic analysis was performed using partial nucleotide sequences at the amplified RNA-dependent RNA polymerase gene. Total anti-HEV Ig was detected in 32.2% (10 of 31), and 16.1% (5 of 31) of these dolphins were positive by both serology and HEV RNA testing. Nucleotide sequence analyses revealed that HEV strains identified in dolphins were genotype 3. This virus may represent an environmental contamination of food or wastewater as a source of HEV exposure and infection. Our findings provide evidence that HEV is associated with liver disorders in cetaceans and that it is advisable to screen for exposure of this virus in captive dolphins, particularly animals with elevated serum ALT or compromised liver function test results of undetermined cause.

The double-antigen ELISA concept for early detection of Erns -specific classical swine fever virus antibodies and application as an accompanying test for differentiation of infected from marker vaccinated animals

Emergency vaccination with live marker vaccines represents a promising control strategy for future classical swine fever (CSF) outbreaks, and the first live marker vaccine is available in Europe. Successful implementation is dependent on a reliable accompanying diagnostic assay that allows differentiation of infected from vaccinated animals (DIVA). As induction of a protective immune response relies on virus-neutralizing antibodies against E2 protein of CSF virus (CSFV), the most promising DIVA strategy is based on detection of E^rns -specific antibodies in infected swine. The aim of this study was to develop and to evaluate a novel E^rns -specific prototype ELISA (pigtype CSFV E^rns Ab), which may be used for CSF diagnosis including application as an accompanying discriminatory test for CSFV marker vaccines. The concept of a double-antigen ELISA was shown to be a solid strategy to detect E^rns -specific antibodies against CSFV isolates of different genotypes (sensitivity: 93.5%; specificity: 99.7%). Furthermore, detection of early seroconversion is advantageous compared with a frequently used CSFV E2 antibody ELISA. Clear differences in reactivity between sera taken from infected animals and animals vaccinated with various marker vaccines were observed. In combination with the marker vaccine CP7_E2alf, the novel ELISA represents a sensitivity of 90.2% and a specificity of 93.8%. However, cross-reactivity with antibodies against ruminant pestiviruses was observed. Interestingly, the majority of samples tested false-positive in other E^rns -based antibody ELISAs were identified correctly by the novel prototype E^rns ELISA and vice versa. In conclusion, the pigtype CSFV E^rns Ab ELISA can contribute to an improvement in routine CSFV antibody screening, particularly for analysis of sera taken at an early time point after infection and is applicable as a DIVA assay. An additional E^rns antibody assay is recommended for identification of false-positive results in a pig herd immunized with the licensed CP7_E2alf marker vaccine.

Susceptibility of Pigs to Zoonotic Hepatitis E Virus Genotype 3 Isolated from a Wild Boar

In Europe, zoonotic hepatitis E virus (HEV) genotype 3 strains mainly circulate in humans, swine and wild boar. The aim of this study was to investigate the potential transmission of a wild boar originating HEV strain (WbHEV) to swine by intravenous or oral inoculation and to study the consequences of infection of a WbHEV strain, a WbHEV strain previously passaged in a pig and a swine HEV strain after oral inoculation. Firstly, an intravenous infection was performed for which five piglets were divided into two groups with three pigs inoculated with a WbHEV field strain and two pigs inoculated with a HEV-negative swine liver homogenate. All pigs were necropsied 8, 9 and 10 days post-inoculation. Secondly, an oral infection of 56 days was performed on 12 piglets divided into four groups inoculated with a WbHEV strain, a WbHEV strain previously passaged in swine, a swine HEV strain or a HEV-negative swine liver homogenate. After intravenous inoculation, HEV RNA was detected in serum, bile, liver, spleen, duodenum, jejunum, colon, lung, gastro-hepatic lymph nodes and faeces in all infected piglets. After oral inoculation, HEV RNA was detected in serum, bile, liver, gastro-hepatic lymph nodes and faeces. Most of HEV-inoculated pigs became seropositive at day 15. This study provides experimental evidence of early viral spread throughout the organism after intravenous infection with a WbHEV strain and supports the notion that such a zoonotic strain could be transmitted via the natural faecal-oral route of infection between wild boar and pigs but also between pigs.

Chlamydia trachomatis Pgp3 Antibody Persists and Correlates with Self-Reported Infection and Behavioural Risks in a Blinded Cohort Study

Chlamydia trachomatis (Ct) serological studies in populations could help monitor changes in lifetime cumulative risk of infection. We developed a double-antigen sandwich ELISA based on the Ct-specific Pgp3 antigen, then tested blind stored sera from over 800 participants in a New Zealand birth cohort from Dunedin at ages 26, 32 and 38. The double-antigen sandwich ELISA was more sensitive than our previously characterised indirect Pgp3 ELISA. Pgp3 antibody was detected more often in women compared to men and correlated with increasing numbers of sexual partners, self-reported Ct, and younger age at sexual debut in both women and men. At age 26, 24.1% (99/411) of women were Pgp3 seropositive, as were 79.5% (35/44) of those reporting Ct infection; Pgp3 antibody persisted to age 38 in 96.5% (83/86). In men at age 26, the figures were 10.7% (47/442) and 25.0% (6/24), respectively, with high (83.9%) antibody persistence to age 38. At age 38, among those Pgp3 seropositive, 63.3% of women and 83.1% of men had not reported Ct infection. Thus, Ct-specific Pgp3 antibody was detected in most women reporting Ct infection and correlated with risk of infection in those who did not, with most infections remaining undetected. As this antibody persisted for at least twelve years in 96% of these women, serology could be used to evaluate Ct prevention programmes among women.

Anti-HCV immunoassays based on a multiepitope antigen and fluorescent lanthanide chelate reporters

There is a need for simple to produce immunoassays for hepatitis C virus (HCV) antibody capable of detecting all genotypes worldwide. Current commonly used third generation immunoassays use three to six separate recombinant proteins or synthetic peptides. We have developed and expressed in Escherichia coli a single recombinant antigen incorporating epitopes from different HCV proteins. This multiepitope protein (MEP) was used to develop two types of HCV antibody immunoassays: a traditional antibody immunoassay using a labeled secondary antibody (indirect assay) and a double-antigen assay with the same MEP used as capture binder and labeled binder. The secondary antibody assay was evaluated with 171 serum/plasma samples and double-antigen assay with 148 samples. These samples included an in-house patient sample panel, two panels of samples with different HCV genotypes and a seroconversion panel. The secondary antibody immunoassay showed 95.6% sensitivity and 100% specificity while the double-antigen assay showed 91.4% sensitivity and 100% specificity. Both assays detected samples from all six HCV genotypes. The results showed that combining a low-cost recombinant MEP binder antigen with a high sensitivity fluorescent lanthanide reporter can provide a sensitive and specific immunoassay for HCV serology. The results also showed that the sensitivity of HCV double-antigen assays may suffer from the low avidity immune response of acute infections.

Belgian Wildlife as Potential Zoonotic Reservoir of Hepatitis E Virus

Hepatitis E is an acute human liver disease in healthy individuals but may become chronic in immunocompromised patients. It is caused by the hepatitis E virus (HEV) and can have a zoonotic origin, particularly in high-income countries. In this study, 383 sera from wild boars were selected for serology; for virological analyses, 69 sera and 61 livers from young wild boars were used. A total of 189 and 235 sera of, respectively, red deer and roe deer were collected for serological analysis. For virological analyses, 84 and 68 sera and 29 and 27 livers from, respectively, red and roe deer were sampled. An apparent seroprevalence of 34% (95% CI 29.71-39.46) was found in wild boars, of 1% (95% CI 0-2.4) in red deer and 3% (95% CI 0.8-4.2) in roe deer. To assess the ELISA screening prevalence, Western blot (WB) analyses were carried out, a receiver operating characteristic curve analysis was performed and different scenarios with varying ELISA specificities relative to WB were analysed. Seroprevalence remained high whatever the scenario in the wild boar population. In wild boar, 4 of 69 sera and 4 of 61 livers were detected as positive for HEV RNA. All sequences obtained from sera belonged to genotype HEV-3. HEV RNA, belonging to genotype HEV-3, was detected in one of 29 red deer livers. Wild boar can be considered as a host reservoir of the virus in Belgium. However, in contrast to the epidemiological role played by them in other countries, the low prevalence in deer makes these species an unlikely reservoir. This evidence needs further investigation to determine in which situation deer can serve as reservoir. These results also raise the question of the dynamics of HEV infection between wild fauna, domestic pigs and humans.

Viral and Antibody Prevalence of Hepatitis E in European Wild Boars (Sus scrofa) and Hunters at Zoonotic Risk in the Latium Region

Hepatitis E virus (HEV) is a member of the genus Hepevirus within the family Hepeviridae. Hepatitis E is recognized as a zoonosis, and swine and wild boars (Sus scrofa) are known reservoirs of HEV infection. The aim of this study was to investigate the presence of HEV in wild boars and hunters exposed to infection in central Italy (Latium region). During the hunting season, blood samples were collected from 228 wild boars and 20 hunters. The seroprevalence of HEV infection was determined using a commercial enzyme-linked immunosorbent assay, previously validated for use in man, pigs and wild boars. The estimated HEV seroprevalence in wild boars and in hunters was 40.7% (93/228; 95% confidence interval [CI] 34.4-47.1%) and 25% (5/20; 95% CI 6.1-43.9%), respectively. Liver samples were collected from the boars and HEV RNA was detected by nested reverse transcriptase polymerase chain reaction. Fifty-five of 164 tested wild boar liver samples (33.5%; 95% CI 26.2-40.7%) and three of 20 (15.0%; 95% CI 1.3-28.7%) tested human serum samples were positive for HEV RNA. Phylogenetic analysis of the nucleotide sequences obtained from PCR products indicated that the HEV strains present in wild boars and the human population all belonged to genotype 3, supporting the zoonotic role of wild boars in the spread of HEV infection.

Estimation of hepatitis E virus (HEV) pig seroprevalence using ELISA and Western blot and comparison between human and pig HEV sequences in Belgium

Zoonotic transmission of hepatitis E virus (HEV) is of special concern, particularly in high income countries were waterborne infections are less frequent than in developing countries. High HEV seroprevalences can be found in European pig populations. The aims of this study were to obtain prevalence data on HEV infection in swine in Belgium and to phylogenetically compare Belgian human HEV sequences with those obtained from swine. An ELISA screening prevalence of 73% (95% CI 68.8-77.5) was determined in Belgian pigs and a part of the results were re-evaluated by Western blot (WB). A receiver operating characteristic curve analysis was performed and scenarios varying the ELISA specificity relative to WB were analysed. The seroprevalences estimated by the different scenarios ranged between 69 and 81% and are in agreement with the high exposure of the European pig population to HEV. Pig HEV sequences were genetically compared to those detected in humans in Belgium and a predominance of genotype 3 subtype f was shown in both swine and humans. The high HEV seroprevalence in swine and the close phylogenetic relationships between pig and human HEV sequences further support the risk for zoonotic transmission of HEV between humans and pigs.

Hepatitis E virus serosurvey among pet dogs and cats in several developed cities in China

Infection by Hepatitis E virus (HEV), as a zoonotic disease virus, is well studied in pigs in China, but few studies in pets have been performed. This study was designed to characterize the prevalence of HEV infection among pet dogs and cats in major metropolitan areas of China. We conducted a seroepidemiological survey from 2012 to 2013 in 5 developed cities, Beijing, Shanghai, Canton, Shenzhen and Macao, by enzyme-linked immunosorbent assay (ELISA). The overall HEV seroprevalence in 658 dog and 191 cat serum samples was 21.12% and 6.28%, respectively. The analysis in dogs suggested that there were significant differences among cities, and the positive rate of HEV-specific antibody in all cities ranged from 6.06% (Shenzhen) to 29.34% (Beijing). Older pet cats have a high risk (OR, 10.25) for HEV seropositivity, but no strong relationship was observed between different genders and age groups. Additionally, it was revealed that stray dogs, omnivorous pet dogs and pet cats who share food, such as kitchen residue, with the general population would have a higher risk for HEV seropositivity. The odds ratios for these groups are 2.40, 2.83 and 5.39, respectively, compared with pet dogs and cats fed on commercial food. In this study, we first report that HEV is prevalent in pet dogs and cats in several large cities in China. Swill and kitchen residue may be a potential risk for HEV transmission from human to pets. As the sample size was relatively small in this study and may not be fully representative of China, further investigation is required to confirm the conclusions.

Seroprevalence of hepatitis E virus in pigs from different farming systems in The Netherlands

Sporadic nontravel-related hepatitis E virus (HEV) infections have been reported in industrialized countries. These infections are caused by zoonotic HEV genotypes 3 and 4 that circulate in swine, wild boar, and deer. In The Netherlands, HEV RNA has been detected in >50% of the pig farms, and HEV-specific antibodies were detected in ∼70% of the slaughter pigs. In the current study, HEV seroprevalences were investigated in pigs raised on conventional, free-range, and organic farms in The Netherlands. Differences in seroprevalence may indicate different exposure routes or transmission dynamics within pig herds for HEV. In 2004, serum samples of 846 fattening pigs were obtained from farms that applied conventional (265 pigs at 24 farms), organic (417 pigs at 42 farms), and free-range (164 pigs at 12 farms) farming. HEV-specific antibodies were detected in samples from all conventional and free-range pig farms and in 41 of 42 organic pig farms, indicating that the probability of introducing HEV on a farm appeared to be equal for the different farming types. The estimated average within-herd seroprevalence was significantly higher for pigs raised on organic farms (89%) than for pigs raised on conventional farms (72%, P = 0.04) and nearly significant for pigs raised on free-range farms (76%, P = 0.06). Six of ten organic farms were estimated to have a withinherd seroprevalence of >95%, compared with 1 of 10 and 4 of 10 of the free-range and conventional pig farms, respectively. This suggests a higher force of infection with HEV for pigs reared on organic farms compared with pigs reared on conventional or free-range farms. This may be due to repetitive exposure to HEV caused by farming system-specific housing conditions, such as a greater contact frequency between pigs and more exposure to pig manure, increasing the transmission rate.

Hepatitis E in Australian HIV-infected patients: an under-recognised pathogen?

Background Hepatitis E virus (HEV) infection has been found to cause chronic hepatitis in HIV-infected patients. In Australia, where HEV is nonendemic, background seroprevalence is reportedly low but has not been evaluated in the HIV-infected population. The study aimed to assess the seroprevalence of HEV in a cohort of HIV-infected patients with normal liver function and in another group with biochemical hepatitis.

METHODS

Patients were selected from the Victorian HIV Blood and Tissue Storage Bank and stored plasma was tested. Positive HEV antibody specimens were examined for HEV RNA by polymerase chain reaction.

RESULTS

A total of 191 HIV patients were tested for HEV by serology. Eight of 100 (8%) HIV-infected patients with normal liver function and 4 of 91 (4.4%) of those with biochemical hepatitis had HEV antibodies. All four patients with abnormal liver function and positive HEV serology were coinfected with hepatitis C and were significantly more likely to have higher median alanine aminotransferase levels (382 vs 139UL(-1), P=0.01). HEV-positive patients with normal liver function were more likely to be born outside Australia (P=0.004). Two of four patients with biochemical hepatitis who were seropositive for HEV had detectable HEV RNA.

CONCLUSIONS

The seroprevalence of HEV in this Australian HIV-infected cohort is higher than the estimated background prevalence in the HIV-negative population. In patients coinfected with hepatitis C, the degree of alanine aminotransferase elevation was significantly worse. HEV may contribute to the development of abnormal liver function.

Use of immuno-dominant epitope derived from genotype 4 as a diagnostic reagent for detecting the antibodies against Hepatitis E Virus

Background

Despite the genotype 4 has become the dominant cause of hepatitis E disease in China, none antigen derived from genotype 4 of hepatitis E virus (HEV) was used in current commercial anti-HEV immunoassay, and the serological reactivity of antigen derive from genotype 4 is not well-charactered.

Methods

We expressed and purified the 4 main immuno-dominant epitopes derived from genotype 1 and 4 including ORF2 (410-621aa) of genotype 4, ORF3 (47-114aa) of genotype 4, ORF2 (396-606aa) of genotype 1 and ORF3 (56-123aa) of genotype 4.

Results

The ORF2 of genotype 4 displayed good diagnostics performance according to ROC analysis using in-house panel, and the immunoassays based the ORF2 of genotype 4 was then developed to detect the anti-HEV IgG antibodies and evaluated further in 530 anti-HEV IgG positive specimens and 380 negative specimens. The sensitivity and the specificity is 98.1% (520/530) and 94.7% (360/380) for immunoassay based on ORF2 of genotype 4, 96.6% (512/530) and 92.6% (352/380) for commercial immunoassay based on genotype 1. It is noted that all of the positive samples will be detected by combing two assays together. The anti-HEV immunoassays based on genotype 4 are in accordance with Chinese anti-HEV national standard,and show an good agreement of 95.8% with commercial assay (kappa=0.913, P=0.014).

Conclusions

The immunoassay based on ORF2G4 displays good performance, and combining assay based on genotype 1 together with genotype 4 will benefit the HEV diagnosis in large scale samples.

Hepatitis E virus seroprevalence and risk factors for individuals in working contact with animals

BACKGROUND

In industrial countries genotypes 3 and 4 of HEV are detected in swine, wild boar, deer and rabbits, and they are associated with autochthonous infections suggesting the existence of zoonotic HEV infections, compatible with the putative involvement of undercooked pork and big game products as a source of infection.

OBJECTIVES

To evaluate the prevalence of anti-HEV antibodies in different population groups in contact with animals and to investigate risk factors for HEV infection.

STUDY DESIGN

Serum samples were collected from 859 healthy French subjects, including pig farm workers, forestry workers and individuals without working contact with animals (control group). In addition, 58 swine veterinarians were included in the study. Subjects were interviewed using a structured questionnaire, and anti-HEV antibodies were investigated using a sensitive and specific sandwich ELISA.

RESULTS

Anti-Hepatitis E virus (HEV) antibodies were detected in 26% of control population, and in 36% and 44% of forestry and pig farm workers, respectively. In addition, an increase in seroprevalence from the north to the south of France was observed (30.2% versus 40.7%). Consumption of pork liver sausage (AOR 4.4, p < 10(-4)), occupational contact with animals (AOR 1.58, p = 0.038 for forestry workers and AOR 2.51, p < 10(-4) for pig farm workers), and living in southern France (AOR 1.47, p = 0.02), were independent risk factors. Wearing working gloves and boots might reduce HEV infection.

CONCLUSIONS

Occupational exposure to animals and consuming raw or undercooked pork liver sausage or pork liver play a significant role in HEV transmission in industrial countries.

Diagnosis of hepatitis E

Hepatitis E, caused by infection with hepatitis E virus (HEV), is a common cause of enterically-transmitted acute hepatitis in developing countries. Occasional cases of sporadic hepatitis E have been increasingly recognized in developed countries over the past decade. These cases differ from those in developing countries in being possibly caused by zoonotic transmission, often affecting people with a suppressed immune system and occasionally leading to persistent HEV infection. The commonly used tests for HEV infection include detection of IgM and IgG anti-HEV antibodies and detection of HEV RNA. IgM anti-HEV antibodies can be detected during the first few months after HEV infection, whereas IgG anti-HEV antibodies represent either recent or remote exposure. The presence of HEV RNA indicates current infection, whether acute or chronic. Although several diagnostic assays for anti-HEV antibodies are available, they have undergone fairly limited testing and often provide discordant results, particularly for IgG antibodies. Thus, although the available antibody assays might be useful for case diagnosis in areas with high disease endemicity, their use for case diagnosis in areas with low endemicity and for seroprevalence studies remains problematic. Improved validation of existing anti-HEV antibody assays or development of new assays with superior performance characteristics is urgently needed.

Development and application of a double-antigen sandwich enzyme-linked immunosorbent assay for detection of antibodies to porcine circovirus 2

A double-antigen sandwich enzyme-linked immunosorbent assay (ELISA) is described for detection of porcine circovirus 2 (PCV2) antibodies using the well-characterized recombinant PCV2 capsid protein. In a comparative test of 394 pig sera against an indirect immunofluorescence (IIF) test and a commercial ELISA kit (also based on the recombinant PCV2 capsid protein), the results showed that the diagnostic sensitivity, specificity, and accuracy of the assay were, respectively, 90.61, 94.02, and 91.62% compared with IIF and 94.38, 95.28, and 94.67% compared with the commercial ELISA kit. Assay of 12 PCV-free pigs over a 5-week period produced only PCV2-negative titers by all 3 methods. These results and the seroprofiles of 4 pig farms obtained by both the commercial ELISA kit and the double-antigen sandwich ELISA indicate that the sandwich ELISA is a reliable method for detection of antibodies to PCV2. Additionally, the method described here permits the use of undiluted test serum samples simultaneously loaded with horseradish peroxidase (HRP)-conjugated antigen into the test well, and the complete test procedure can be performed in less than 90 min. This double-antigen sandwich ELISA should be a useful tool to aid swine industry professionals in deciding the intervention strategies for the control of PCV2-associated diseases.

High hepatitis E virus seroprevalence in forestry workers and in wild boars in France

Hepatitis E virus (HEV) is a fecally and orally transmitted human pathogen of worldwide distribution. In industrial countries, HEV is observed in an increasing number of autochthonous cases and is considered to be an emerging pathogen. A growing body of evidence suggests that HEV is a zoonotic disease, and pig handlers and pig veterinarians have been reported to be high-risk groups for HEV infection. The aims of the present study were to establish the prevalence of anti-HEV in wild boars in France and to identify whether forestry workers are at a higher risk of HEV infection. Three different anti-HEV tests were used to compare their effectiveness in detecting anti-HEV in the general population. The most sensitive test was then used to investigate HEV seroprevalence in 593 forestry workers and 421 wild boars. Anti-HEV was detected in 31% of the forestry workers and 14% of the wild boars. Detection of anti-HEV in humans was correlated with age, geographical location, and occupational activity and in wild boars was correlated with geographical location. HEV infection is frequent in woodcutters in France, and it varies geographically. Further studies are needed to confirm these findings and to elucidate the transmission route and the exact virus reservoirs.

Seroprevalence study in forestry workers from eastern Germany using novel genotype 3- and rat hepatitis E virus-specific immunoglobulin G ELISAs

Hepatitis E virus (HEV) is the causative agent of an acute self-limiting hepatitis in humans. In industrialized countries, autochthonous cases are linked to zoonotic transmission from domestic pigs, wild boar and red deer. The main route of human infection presumably is consumption of contaminated meat. Farmers, slaughterers and veterinarians are expected to be risk groups as they work close to potentially infected animals. In this study, we tested four Escherichia coli-expressed segments of the capsid protein (CP) of a German wild boar-derived HEV genotype 3 strain for their diagnostic value in an indirect immunoglobulin G (IgG) ELISA. In an initial validation experiment, a carboxy-terminal CP segment spanning amino acid (aa) residues 326-608 outperformed the other segments harbouring aa residues 112-608, 326-660 and 112-335. Based on this segment, an indirect ELISA for detection of anti-HEV IgG antibodies in human sera was established and validated using a commercial line immunoassay as reference assay. A total of 563 sera from forestry workers of all forestry offices of Brandenburg, eastern Germany and 301 sera of blood donors from eastern Germany were surveyed using these assays. The commercial test revealed seroprevalence rates of 11% for blood donors and 18% for forestry workers. These rates are in line with data obtained by the in-house test (12 and 21%). Hence, the in-house test performed strikingly similar to the commercial test (sensitivity 0.9318, specificity 0.9542). An initial screening of forestry worker and blood donor sera with a corresponding CP segment of the recently discovered Norway rat-associated HEV revealed several strong positive sera exclusively in the forestry worker panel. Future investigations have to prove the performance of this novel IgG ELISA in large-scale seroepidemiological studies. In addition, the observed elevated seroprevalence in a forestry worker group has to be confirmed by studies on groups of forestry workers from other regions. The epidemiological role of ratHEV in human disease should be assessed in a large-scale study of risk and non-risk groups.

Preparation and evaluation of recombinant severe fever with thrombocytopenia syndrome virus nucleocapsid protein for detection of total antibodies in human and animal sera by double-antigen sandwich enzyme-linked immunosorbent assay

The recent emergence of the human infection confirmed to be caused by severe fever with thrombocytopenia syndrome virus (SFTSV) in China is of global concern. Safe diagnostic immunoreagents for determination of human and animal seroprevalence in epidemiological investigations are urgently needed. This paper describes the cloning and expression of the nucleocapsid (N) protein of SFTSV. An N-protein-based double-antigen sandwich enzyme-linked immunosorbent assay (ELISA) system was set up to detect the total antibodies in human and animal sera. We reasoned that as the double-antigen sandwich ELISA detected total antibodies with a higher sensitivity than traditional indirect ELISA, it could be used to detect SFTSV-specific antibodies from different animal species. The serum neutralization test was used to validate the performance of this ELISA system. All human and animal sera that tested positive in the neutralization test were also positive in the sandwich ELISA, and there was a high correlation between serum neutralizing titers and ELISA readings. Cross-reactivity was evaluated, and the system was found to be highly specific to SFTSV; all hantavirus- and dengue virus-confirmed patient samples were negative. SFTSV-confirmed human and animal sera from both Anhui and Hubei Provinces in China reacted with N protein in this ELISA, suggesting no major antigenic variation between geographically disparate virus isolates and the suitability of this assay in nationwide application. ELISA results showed that 3.6% of the human serum samples and 47.7% of the animal field serum samples were positive for SFTSV antibodies, indicating that SFTSV has circulated widely in China. This assay, which is simple to operate, poses no biohazard risk, does not require sophisticated equipment, and can be used in disease surveillance programs, particularly in the screening of large numbers of samples from various animal species.

Restricted enzooticity of hepatitis E virus genotypes 1 to 4 in the United States

Hepatitis E is recognized as a zoonosis, and swine are known reservoirs, but how broadly enzootic its causative agent, hepatitis E virus (HEV), is remains controversial. To determine the prevalence of HEV infection in animals, a serological assay with capability to detect anti-HEV-antibody across a wide variety of animal species was devised. Recombinant antigens comprising truncated capsid proteins generated from HEV-subgenomic constructs that represent all four viral genotypes were used to capture anti-HEV in the test sample and as an analyte reporter. To facilitate development and validation of the assay, serum samples were assembled from blood donors (n = 372), acute hepatitis E patients (n = 94), five laboratory animals (rhesus monkey, pig, New Zealand rabbit, Wistar rat, and BALB/c mouse) immunized with HEV antigens, and four pigs experimentally infected with HEV. The assay was then applied to 4,936 sera collected from 35 genera of animals that were wild, feral, domesticated, or otherwise held captive in the United States. Test positivity was determined in 457 samples (9.3%). These originated from: bison (3/65, 4.6%), cattle (174/1,156, 15%), dogs (2/212, 0.9%), Norway rats (2/318, 0.6%), farmed swine (267/648, 41.2%), and feral swine (9/306, 2.9%). Only the porcine samples yielded the highest reactivities. HEV RNA was amplified from one farmed pig and two feral pigs and characterized by nucleotide sequencing to belong to genotype 3. HEV infected farmed swine primarily, and the role of other animals as reservoirs of its zoonotic spread appears to be limited.

Serological diagnostics of hepatitis E virus infection

Development of accurate diagnostic assays for the detection of serological markers of hepatitis E virus (HEV) infection remains challenging. In the course of nearly 20 years after the discovery of HEV, significant progress has been made in characterizing the antigenic structure of HEV proteins, engineering highly immunoreactive diagnostic antigens, and devising efficient serological assays. However, many outstanding issues related to sensitivity and specificity of these assays in clinical and epidemiological settings remain to be resolved. Complexity of antigenic composition, viral genetic heterogeneity and varying epidemiological patterns of hepatitis E in different parts of the world present challenges to the refinement of HEV serological diagnostic assays. Development of antigens specially designed for the identification of serological markers specific to acute infection and of IgG anti-HEV specific to the convalescent phase of infection would greatly facilitate accurate identification of active, recent and past HEV infections.

Differences in capabilities of different enzyme immunoassays to detect anti-hepatitis E virus immunoglobulin G in pigs infected experimentally with hepatitis E virus genotype 3 or 4 and in pigs with unknown exposure

Hepatitis E virus (HEV), a major cause of acute viral hepatitis in humans in many developing countries, is highly prevalent in the pig population worldwide. The objective of this study was to assess the capability of three porcine prototypes of a human enzyme-linked immunosorbent assay (ELISA), an in-house ELISA and a line-immunoassay (LIA) to detect anti-HEV antibodies in pigs infected experimentally with HEV (n = 57), known to be negative for HEV infection (n = 27), or with unknown exposure to HEV infection (field samples, n = 90). All 27 samples from non-infected pigs were negative with all five assays. The earliest detection of anti-HEV antibodies occurred at 14 days post-inoculation (dpi) with four of five assays. From 42 dpi, all samples from infected pigs were detected correctly as anti-HEV positive. Kappa analysis demonstrated substantial agreement among tests (0.62-1.00) at 14 dpi and complete agreement (1.00) at 56 dpi. The overall area under the curve for all quantitative tests as determined by receiver operator characteristic analysis ranged from 0.794 to 0.831 indicating moderate accuracy. The results showed that all five assays can detect anti-HEV IgG antibodies accurately in pigs infected experimentally with HEV. In field samples, a higher prevalence of anti-HEV IgG was found in breeding herds than in growing pigs (100% versus 66.7-93.9%). These serological assays should be very useful in veterinary diagnostic labs for HEV diagnosis in swine.

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.

Seroprevalence and molecular detection of hepatitis E virus in wild boar and red deer in The Netherlands

To date, sources of hepatitis E virus (HEV) in the Netherlands, including swine and wild boar, have been identified, but no direct attribution to Dutch hepatitis E cases have been demonstrated. Other animal sources may exist. To identify these species, HEV RNA detection by RT-PCR is required, but complicated. A preselection based on serology may be useful. Therefore, wildlife species were studied by serology and molecular methods. Using a species-independent double-antigen sandwich ELISA, HEV-specific antibodies were detected in sera from 12% of 1029 wild boar (Sus scrofa scrofa), in 5% of 38 red deer (Cervus elaphus) and in none of 8 studied roe deer (Capreolus capreolus). Differences in background signals were observed between species and accounted for by fitting finite mixture distributions. HEV RNA was detected in 8% of 106 wild boars, in 15% of 39 red deer and in none of 8 roe deer. In conclusion, HEV was shown to be present in European red deer for the first time. This preselection based on species-independent serological assays may be beneficial to identify new potential animal reservoirs of HEV. The consumption of Dutch undercooked wild boar and red deer meat may lead to human exposure to HEV.

Multispecies detection of antibodies to influenza A viruses by a double-antigen sandwich ELISA

A double-antigen sandwich ELISA was developed for the detection of antibodies to influenza A viruses. A recombinant nucleoprotein (rNP) of influenza A virus was used as a capture antigen and an HRP-conjugate for detecting the antibodies. A total of 125 serum samples from birds of different species including chickens, geese, open-billed storks, Khaki Campbell ducks, lesser whistling ducks, and pigeons with known antibodies were tested by ELISA. The sensitivity and the specificity of ELISA were found to be 98% and 97.3%, respectively. The assay was able to detect the presence of influenza A antibodies as early as the fourth day post-inoculation in ducks infected experimentally with influenza A (H5N1) virus. Excellent agreement (97.6%) was obtained between this sandwich ELISA and the hemagglutination inhibition (HI) tests (kappa=0.95). The double-antigen sandwich ELISA correlated well with a commercial avian influenza (AI) multispecies ELISA and was slightly more sensitive than the AI multispecies ELISA. These findings indicate that the double-antigen sandwich ELISA based on rNP may offer an effective screening method for serodiagnosis of influenza A virus. The double-antigen sandwich ELISA also enables the detection of antibodies to influenza A viruses in different species without the need for species-specific secondary antibodies.

Good performance of immunoglobulin M assays in diagnosing genotype 3 hepatitis E virus infections

We have evaluated three anti-hepatitis E virus (anti-HEV) immunoglobulin M (IgM) assays, the EIAgen HEV IgM assay (Adaltis), the HEV IgM enzyme-linked immunosorbent assay 3.0, and the Assure HEV IgM rapid test (MP Diagnostics), for the routine detection of acute genotype 3 HEV. Their sensitivities were fairly good (90%, 88%, and 82%), and their specificities were excellent (100%, 99.5%, and 100%).