Non-A, non-B epidemic hepatitis: visualization of virus-like particles in the stool by immune electron microscopy

Direct exposure of the head to solar heat radiation impairs motor-cognitive performance

Health and performance impairments provoked by thermal stress are societal challenges geographically spreading and intensifying with global warming. Yet, science may be underestimating the true impact, since no study has evaluated effects of sunlight exposure on human brain temperature and function. Accordingly, performance in cognitively dominated and combined motor-cognitive tasks and markers of rising brainstem temperature were evaluated during exposure to simulated sunlight (equal to ~1000 watt/m²). Acute exposure did not affect any performance measures, whereas prolonged exposure of the head and neck provoked an elevation of the core temperature by 1 °C and significant impairments of cognitively dominated and motor task performances. Importantly, impairments emerged at considerably lower hyperthermia levels compared to previous experiments and to the trials in the presents study without radiant heating of the head. These findings highlight the importance of including the effect of sunlight radiative heating of the head and neck in future scientific evaluations of environmental heat stress impacts and specific protection of the head to minimize detrimental effects.

Biliary Secretion of Quasi-Enveloped Human Hepatitis A Virus

Hepatitis A virus (HAV) is an unusual picornavirus that is released from cells cloaked in host-derived membranes. These quasi-enveloped virions (eHAV) are the only particle type circulating in blood during infection, whereas only nonenveloped virions are shed in feces. The reason for this is uncertain. Hepatocytes, the only cell type known to support HAV replication in vivo, are highly polarized epithelial cells with basolateral membranes facing onto hepatic (blood) sinusoids and apical membranes abutting biliary canaliculi from which bile is secreted to the gut. To assess whether eHAV and nonenveloped virus egress from cells via vectorially distinct pathways, we studied infected polarized cultures of Caco-2 and HepG2-N6 cells. Most (>99%) progeny virions were released apically from Caco-2 cells, whereas basolateral (64%) versus apical (36%) release was more balanced with HepG2-N6 cells. Both apically and basolaterally released virions were predominantly enveloped, with no suggestion of differential vectorial release of eHAV versus naked virions. Basolateral to apical transcytosis of either particle type was minimal (<0.02%/h) in HepG2-N6 cells, arguing against this as a mechanism for differences in membrane envelopment of serum versus fecal virus. High concentrations of human bile acids converted eHAV to nonenveloped virions, whereas virus present in bile from HAV-infected Ifnar1^−/−Ifngr1^−/− and Mavs^−/− mice banded over a range of densities extending from that of eHAV to that of nonenveloped virions. We conclude that nonenveloped virions shed in feces are derived from eHAV released across the canalicular membrane and stripped of membranes by the detergent action of bile acids within the proximal biliary canaliculus.

HAV is a hepatotropic, fecally/orally transmitted picornavirus that can cause severe hepatitis in humans. Recent work reveals that it has an unusual life cycle. Virus is found in cell culture supernatant fluids in two mature, infectious forms: one wrapped in membranes (quasi-enveloped) and another that is nonenveloped. Membrane-wrapped virions circulate in blood during acute infection and are resistant to neutralizing antibodies, likely facilitating HAV dissemination within the liver. On the other hand, virus shed in feces is nonenveloped and highly stable, facilitating epidemic spread and transmission to naive hosts. Factors controlling the biogenesis of these two distinct forms of the virus in infected humans are not understood. Here we characterize vectorial release of quasi-enveloped virions from polarized epithelial cell cultures and provide evidence that bile acids strip membranes from eHAV following its secretion into the biliary tract. These results enhance our understanding of the life cycle of this unusual picornavirus.

Hepatitis E: Discovery, global impact, control and cure

Hepatitis E was identified as an epidemic of non-A, non-B hepatitis from Kashmir, India in 1978. Hepatitis E virus (HEV), the etiological agent is the sole member of family Hepeviridae. The virus has marked heterogeneity and infects many animals like bats, camel, chicken, deer, boar, mongoose, pigs, rats, rabbit and cutthroat trout. Hepatitis E is a disease with a major global impact and has two distinct epidemiological patterns. Hepatitis E is an imperative health issue in developing nations, transmitted through sullied water and happens most every now in young adults. The disease is particularly severe during pregnancy and in people with underlying liver cirrhosis. Autochthonous hepatitis E is increasingly recognized in developed countries. The virus infects domestic pigs, wild boar and Sika deer in these countries. HEV infections in humans occur by eating the undercooked game flesh, raw liver from supermarkets and Figatelli sausages. Blood transfusion-associated HEV infections occur in many countries and screening of donors for HEV RNA is under consideration. Hepatitis E causes a number of extrahepatic diseases, including a wide spectrum of neurological syndromes. HEV genotype 3 causes prolonged viremia, chronic hepatitis, liver fibrosis and cirrhosis in organ transplant patients. The virus is amenable to ribavirin monotherapy and most patients clear the virus in a few weeks. Hepatitis E vaccine -239, marketed in China, has shown high efficacy with sustained protection for over four years.

Lessons learned from successful human vaccines: Delineating key epitopes by dissecting the capsid proteins

Recombinant VLP-based vaccines have been successfully used against 3 diseases caused by viral infections: Hepatitis B, cervical cancer and hepatitis E. The VLP approach is attracting increasing attention in vaccine design and development for human and veterinary use. This review summarizes the clinically relevant epitopes on the VLP antigens in successful human vaccines. These virion-like epitopes, which can be delineated with molecular biology, cryo-electron microscopy and x-ray crystallographic methods, are the prerequisites for these efficacious vaccines to elicit functional antibodies. The critical epitopes and key factors influencing these epitopes are discussed for the HEV, HPV and HBV vaccines. A pentamer (for HPV) or a dimer (for HEV and HBV), rather than a monomer, is the basic building block harboring critical epitopes for the assembly of VLP antigen. The processing and formulation of VLP-based vaccines need to be developed to promote the formation and stabilization of these epitopes in the recombinant antigens. Delineating the critical epitopes is essential for antigen design in the early phase of vaccine development and for critical quality attribute analysis in the commercial phase of vaccine manufacturing.

Hepatitis E Virus and Related Viruses in Animals

Hepatitis E is an acute human liver disease in healthy individuals which may eventually become chronic. It is caused by the hepatitis E virus (HEV) and can have a zoonotic origin. Nearly 57,000 people die yearly from hepatitis E-related conditions. The disease is endemic in both developing and developed countries with distinct epidemiologic profiles. In developing countries, the disease is associated with inadequate water treatment, while in developed countries, transmission is associated with animal contact and the ingestion of raw or uncooked meat, especially liver. All human HEV are grouped into at least four genotypes, while HEV or HEV-related viruses have been identified in an increasing number of domestic and wild animal species. Despite a high genetic diversity, only one single HEV serotype has been described to date for HEV genotypes 1-4. The discovery of new HEV or HEV-related viruses leads to a continuing increase in the number of genotypes. In addition, the genome organization of all these viruses is variable with overlapping open reading frames (ORF) and differences in the location of ORF3. In spite of the role of some domestic and wild animals as reservoir, the origin of HEV and HEV-related viruses in humans and animals is still unclear. This review discusses aspects of the detection, molecular virology, zoonotic transmission and origin of HEV and HEV-related viruses in the context of 'One Health' and establishes a link between the previous and the new taxonomy of this growing virus family.

Naked Viruses That Aren't Always Naked: Quasi-Enveloped Agents of Acute Hepatitis

Historically, viruses were considered to be either enveloped or nonenveloped. However, recent work on hepatitis A virus and hepatitis E virus challenges this long-held tenet. Whereas these human pathogens are shed in feces as naked nonenveloped virions, recent studies indicate that both circulate in the blood completely masked in membranes during acute infection. These membrane-wrapped virions are as infectious as their naked counterparts, although they do not express a virally encoded protein on their surface, thus distinguishing them from conventional enveloped viruses. The absence of a viral fusion protein implies that these quasi-enveloped virions have unique mechanisms for entry into cells. Like true enveloped viruses, however, these phylogenetically distinct viruses usurp components of the host ESCRT system to hijack host cell membranes and noncytolytically exit infected cells. The membrane protects these viruses from neutralizing antibodies, facilitating dissemination within the host, whereas nonenveloped virions shed in feces are stable in the environment, allowing for epidemic transmission.

Peek-a-boo: membrane hijacking and the pathogenesis of viral hepatitis

Historically, animal viruses have been classified on the basis of the presence or absence of an envelope - an external lipid bilayer membrane typically carrying one or more viral glycoproteins. However, growing evidence indicates that some 'non-enveloped' viruses circulate in the blood of infected individuals enveloped in host-derived membranes that provide protection from neutralizing antibodies. In this opinion article, we discuss this novel strategy for virus survival and consider how it contributes to the pathogenesis of acute viral hepatitis. The acquisition of an envelope by non-enveloped viruses profoundly influences their interaction with the host at both the cellular and system level and challenges how we think about vaccine protection against these infections.

Seroprevalence of hepatitis E virus in humans and geographically matched food animals in Egypt

The aim of current study was to investigate the epidemiology of Hepatitis E virus (HEV) in humans and geographically matched food animals as a novel zoonotic assessment in Egypt. Blood samples were collected from patients who had a history of jaundice and attended to fever and general hospitals. Animal blood samples were collected from cows, buffaloes, sheep and goats convenient to HEV seropositive humans. Enzyme Immuno Assay (EIA) protocol was used to determine IgG anti-HEV. Sex and pregnancy were investigated as potential risk factors for HEV infection. Of 134 examined humans, 51 (38.1%) were positive for IgG anti-HEV. The males showed 26.8% seropositivity while the recorded female seropositivity was 50.8%, with a significant difference at P = 0.005, Odds Ratio (OR) = 0.35 at 95% confidence interval (CI): 0.17-0.73. There was a significant difference at P = 0.02 between seropositivity in pregnant (25%) and non-pregnant women (59.6%); OR was 0.23 (95% CI: 0.06-0.81). Anorexia was the most common symptom whereas paraesthesia and back pain were the least within icteric seropositive HEV humans. Hepatitis E virus seropositivity was recorded in 21.6%, 14%, 4.4% and 9.4% from examined cows, buffaloes, sheep and goats, respectively. The infected food animals were convenient to positive HEV humans who may declare the epidemiological picture of potential zoonotic HEV.

Hepatitis E virus enters liver cells through receptor-dependent clathrin-mediated endocytosis

We investigated the virus-host interaction for hepatitis E virus (HEV) by performing competitive binding assays using in vitro assembled virus-like particles (VLPs). We used Escherichia coli expressed native capsid protein (pORF2) and its mutants with an attached Gly((5))-Ala (linker) reporter [enhanced green fluorescent protein (EGFP)/firefly luciferase (Fluc)]. Transmission electron microscopy and nanoparticle tracking showed near uniform particles of approximately 30-35 nm in diameter for pORF2 VLPs and 60-100 nm for reporter-linked VLPs. Binding of reporter-linked full-length (1-660aa) and N-terminal truncated (Δ1-112aa) pORF2 VLPs to Huh7 cell surfaces was found to be specific with 1.92 ± 0.065 × 10(5) sites per cell. Saturation binding indicated an equilibrium dissociation constant (K(d)) of 121.1 ± 23.83 and 123.8 ± 16.15 nm for pORF2-linker-EGFP and pORF2-linker-Fluc VLPs respectively. A similar binding pattern was observed for Δ1-112aa pORF2-linker-EGFP and Δ1-112aa pORF2-linker-Fluc VLPs with K(d) values of 123.6 ± 10.60 and 135.6 ± 16.19 nm respectively. The affinity (log K(i)) of pORF2 binding on Huh7 cells in the presence of EGFP-tagged and Fluc-tagged pORF2 VLPs was found to be approximately 2.0. However, no VLP formation or binding was observed with refolded C-terminal truncated (Δ458-660aa) pORF2. We investigated HEV internalization using fluorescent VLPs (EGFP-VLPs), which showed vesicle-mediated uptake starting at 5 min post-incubation. The uptake of VLPs could be stopped by inhibitors for clathrin-dependent endocytosis, but not by caveosome inhibitors. No binding and uptake of EGFP-VLPs were observed on non-hepatic cell lines (HeLa and SiHa). These findings suggest that HEV attaches to the host cell via a specific high affinity receptor and enters the cytoplasm by clathrin-mediated endocytosis.

The global burden of hepatitis E virus genotypes 1 and 2 in 2005

We estimated the global burden of hepatitis E virus (HEV) genotypes 1 and 2 in 2005. HEV is an emergent waterborne infection that causes source-originated epidemics of acute disease with a case fatality rate thought to vary by age and pregnancy status. To create our estimates, we modeled the annual disease burden of HEV genotypes 1 and 2 for 9 of 21 regions defined for the Global Burden of Diseases, Injuries, and Risk Factors Study (the GBD 2010 Study), which represent 71% of the world's population. We estimated the seroprevalence of anti-HEV antibody and annual incidence of infection for each region using data from 37 published national studies and the DISMOD 3, a generic disease model designed for the GBD Study. We converted incident infections into three mutually exclusive results of infection: (1) asymptomatic episodes, (2) symptomatic disease, and (3) death from HEV. We also estimated incremental cases of stillbirths among infected pregnant women. For 2005, we estimated 20.1 (95% credible interval [Cr.I.]: 2.8-37.0) million incident HEV infections across the nine GBD Regions, resulting in 3.4 (95% Cr.I.: 0.5-6.5) million symptomatic cases, 70,000 (95% Cr.I.: 12,400-132,732) deaths, and 3,000 (95% Cr.I.: 1,892-4,424) stillbirths. We estimated a probability of symptomatic illness given infection of 0.198 (95% Cr.I.: 0.167-0.229) and a probability of death given symptomatic illness of 0.019 (95% Cr.I.: 0.017-0.021) for nonpregnant cases and 0.198 (95% Cr.I.: 0.169-0.227) for pregnant cases.

CONCLUSION

The model was most sensitive to estimates of age-specific incidence of HEV disease.

Structure of hepatitis E viral particle

Hepatitis E is acute hepatitis caused by infection of hepatitis E virus (HEV) via a fecal-to-oral or zoonotic route. HEV is a small, non-enveloped virus containing positive strand RNA as a genome. Recently, the three-dimensional structures of the HEV-like particles and spike domain protruded from the surface of the particle expressed by recombinant baculovirus or bacteria have been revealed. Based on these reports, the structural features of the HEV capsid subunit and viral particle are reviewed to give insights to the mechanisms underlying the particle assembly, antigenicity, host cell attachment and native virion packaging.

Detection of hepatitis E virus in samples of animal origin collected in Hungary

Hepatitis E virus (HEV) is an enterically transmitted human pathogen. HEV infections are mainly associated with acute, self-limited, icteric hepatitis with an average mortality rate of 1%. Animal reservoirs are considered to play an important role in the maintenance of the virus and in the spread of HEV to humans. HEV-induced seroconversion was described in several species, however clinical hepatitis in animals has not been observed to date. HEV strains from animals are genetically closely related to human HEV isolates, which supports the opinions on the zoonotic transmission of the virus. In this expansive study the occurrence of HEV was investigated in Hungarian wild and domesticated animal samples. HEV RNA was detected by reverse transcription-polymerase chain reaction in liver samples of wild boars, roe deer, and deer. The investigations of domestic swine samples detected HEV in 39% of the investigated Hungarian pig farms. Simultaneous investigation revealed no definite difference between liver and faeces samples of domestic pigs in the frequency of HEV positivity. The highest (36%) incidence of HEV infection was found among the 11-16-week-old pigs. Samples from domestic cattle and rodents collected in pig farms, forests and meadows were tested negative for HEV RNA. Phylogenetic analysis of partial sequences amplified within the ORF1 and ORF2 regions of selected strains revealed that the detected viruses belong to three subgroups of the third genogroup of HEV, and are closely related to human and swine HEV strains detected in different countries. The investigations revealed widespread distribution of HEV in Hungarian wild ungulate and domesticated swine populations, with considerable genetic diversity among the strains.

Full-length sequence of genotype 3 hepatitis E virus derived from a pig in Thailand

Hepatitis E virus (HEV) infection in pigs was investigated in two principal swine farming areas in Thailand. Anti-HEV antibodies and HEV RNA in sera were examined in 258 pigs reared on five commercial farms from age 1 to 6.5 months and sows. Overall, 167 of 258 (64.7%) pigs were positive for anti-HEV IgG, while 20 of 258 (7.75%) had detectable HEV RNA. Sequence analysis of 20 HEV isolates obtained from viremic pigs revealed that they were 92.3-100% identical to each other and had 82.2-88.2% nucleotide similarity to other reported genotype 3 isolates in 415 nucleotide sequences within ORF2 region. Further characterization by sequencing the complete genome of the Thai swine HEV isolate (named Thai-swHEV07) and phylogenetic analysis showed that Thai-swHEV07 segregated into a cluster consisting of swine isolates from Japan, Mongolia, and Kyrgyzstan within the HEV genotype 3. The Thai-swHEV07 had a genomic length of 7,229 nt excluding the polyadenylated region at 3' terminus of the genome. Comparison of Thai-swHEV07 and 27 reported strains of genotype 3 revealed 80.4-85.9% nucleotide identity, with the highest identity of 85.9% to the novel swHEV strain from Mongolia. These findings suggest that genotype 3 HEV isolates are markedly heterogeneous.

Purification of a baculovirus-expressed hepatitis E virus structural protein and utility in an enzyme-linked immunosorbent assay

We report on the purification of the full-length structural protein encoded by open reading frame 2 (ORF-2) of hepatitis E virus. The ORF-2 protein, expressed in Sf9 cells by using a recombinant baculovirus vector system, was successfully purified to homogeneity. Gel electrophoresis of the purified ORF-2 protein showed a single polypeptide of 75 kDa by Coomassie blue staining and by Western blot (immunoblot) analysis. We demonstrated that the partially purified ORF-2 protein could be used successfully in a sensitive and specific enzyme-linked immunosorbent assay for the detection of antibodies to hepatitis E virus.

Diagnosis of acute hepatitis E infection utilizing enzyme immunoassay

Acute hepatitis E infection was diagnosed in a Pakistani immigrant admitted to the University of Illinois Hospital. Utilizing enzyme immunoassay (EIA) tests, specific IgG and IgM class antibodies to three different epitopes of hepatitis E virus (HEV) were detected 12 weeks after the onset of illness and in the early convalescent stage. Sixteen months after the onset of hepatitis, IgM anti-HEV was no longer detectable. Low levels of IgG class anti-HEV antibodies continued to be detected. We demonstrate the utility of the EIA HEV assay to diagnose prospectively acute HEV infection.

Expression and diagnostic utility of hepatitis E virus putative structural proteins expressed in insect cells

The full-length putative structural proteins encoded by open reading frame 2 (ORF2) and ORF3 of hepatitis E virus have been cloned and expressed in recombinant baculovirus. Sera obtained from 28 Sudanese pediatric patients with acute hepatitis and 19 pediatric control patients were analyzed for reactivity to hepatitis E virus by using the baculovirus-expressed ORF2 and ORF3 proteins in a Western blot (immunoblot) format. Seventeen of the 18 patients classified as having non-A, non-B hepatitis, without acute antibody markers for hepatitis A, B, or C viruses, Epstein-Barr virus, or cytomegalovirus, were shown to have immunoglobulin M (IgM) antibodies to the recombinant ORF2 protein, as did two patients with chronic hepatitis B, three of seven patients with acute hepatitis A, and one patient with acute hepatitis B. None of the 19 control patients had IgM antibodies against the ORF2 or ORF3 proteins. The Western blot assay using the baculovirus-expressed ORF3 protein did not appear to be as sensitive as the assay based on the ORF2 protein. Only 10 of the patients classified as having non-A, non-B hepatitis had IgM antibodies to the baculovirus-expressed ORF3 protein. We conclude that a Western blot assay which uses a baculovirus-expressed ORF2 protein is both sensitive and specific for diagnosing acute hepatitis E.

The complete nucleotide sequence of a feline calicivirus

We have determined the complete sequence of a feline calicivirus. The virus genome is 7690 bases long and contains two large open reading frames. Proteins specified by these have similarity to those encoded in the corresponding regions of a candidate calicivirus rabbit hemorrhagic disease virus, but are distinctly different from those specified by another such virus, hepatitis E virus. A third, small open reading frame at the 3' end of the genome is present in both feline and rabbit viruses but is absent from hepatitis E. These findings suggest that the calicivirus family, which consists of a single genus, may require subdivision.

Common aetiological agent for epidemic and sporadic non-A, non-B hepatitis

Enterovirus-like particles have been reported in the acute phase of both epidemic and sporadic non-A, non-B (NANB) hepatitis. To examine whether these particles were the causative agent in the two types of disease, 29 patients with acute viral hepatitis in a north Indian epidemic outbreak and 9 with sporadic acute disease were investigated. 25 (86%) of 29 patients with epidemic hepatitis and 5 (56%) of 9 with sporadic disease were diagnosed as having enterically-transmitted-NANB hepatitis by exclusion. Virus-like particles (VLP) of 30-34 nm were detected in stool of 1 patient with epidemic and 1 with sporadic hepatitis. The VLPs crossreacted serologically and a specific IgM response was seen in acute epidemic and sporadic serum samples. After inoculation with infected stool rhesus monkeys had a mild rise in liver enzymes, and bile samples contained VLPs. These results suggest that the aetiological agent in epidemic and sporadic disease is the same.

Expression of a hepatitis E virus (HEV)-trpE fusion protein containing epitopes recognized by antibodies in sera from human cases and experimentally infected primates

A 1700 base cDNA fragment coding for the putative structural gene(s) of hepatitis E virus (HEV) was inserted into the pATH 10 expression vector. The fusion protein (C2) expressed by this plasmid was found to contain epitopes recognized by anti-HEV antibodies. C2 protein was used in a Western blot format to examine its usefulness in detecting anti-HEV antibodies in well documented human cases of HEV and non-human primates infected with HEV. Both IgM and IgG anti-HEV could be detected in our Western blot assay. This Western blot assay was found not to detect antibodies from acute-phase sera from patients with either HAV or HBV. The C2 protein contains broadly cross-reactive epitopes, and the Western blot assay was able to detect anti-HEV antibodies in patient sera from Asia, Africa, and North America. The optimum serum dilution for the detection of both IgM and IgG was 1:25.

Enzyme-linked immunosorbent assay for diagnosis of acute sporadic hepatitis E in Egyptian children

Hepatitis E virus (HEV) is thought to be a cause of enterically transmitted non-A, non-B (ET-NANB) hepatitis. Waterborne epidemics have been recorded in many developing countries, mainly affecting young-to-middle-aged adults; sporadic infection and overt illness in children are rare. However, a convenient and sensitive diagnostic test for HEV infection is not yet available. We now report the use of a solid-phase enzyme-linked immunoassay (ELISA) that detects IgM and IgG antibody to HEV. In a prospective study of endemic acute hepatitis during 1986 in rural Benha, Egypt, 15 (42%) of 36 children with NANB hepatitis (from whom convalescent-phase sera were available every 3 months to 9 or 12 months) were positive for anti-HEV-IgG by ELISA. Of 20 sera from healthy Benha children (controls), 5 (25%) were also positive for anti-HEV-IgG. When evaluated for anti-HEV-IgM, 6 of the 15 IgG-positive children, but none of the controls, were IgM positive and were thus regarded as having confirmed acute HEV infections. These 6 cases together with 2 presumptive cases (IgM negative, IgG seroconversion from positive to negative) presented sporadically over 9 months. This ELISA is a convenient method for the diagnosis of HEV infection; we have shown that the disease is present in Egypt, that it can occur endemically as sporadic cases, and that children do have overt infection.

Association of hepatitis E virus with an outbreak of hepatitis in Pakistan: serologic responses and pattern of virus excretion

Hepatitis E virus (HEV), a positive-strand RNA agent, has been associated with enterically transmitted non-A, non-B hepatitis in Asia, Africa, and Mexico. To evaluate the role of HEV in an outbreak of hepatitis in Pakistan, we used immune electron microscopy to detect 1) antibody to HEV, for evidence of infection, and 2) virus, to determine the pattern of HEV excretion. Paired sera from 2 patients were assayed for antibody by using reference HEV: one seroconverted, an atypical finding for HEV infections; the other had high levels of anti-HEV in both sera. Virus particles with the size (29 x 31 nm) and morphology of HEV were detected in feces from 10 of 85 patients and serologically identified as HEV by using reference antibodies from an HEV-infected chimpanzee. One of these HEV-containing specimens was collected 9 days before the onset of jaundice; it was among feces from 38 outpatients with nonspecific symptoms and biochemical hepatitis, 12 of whom subsequently developed jaundice. The other 9 feces with HEV were among 36 collected within 7 days of the onset of acute icteric hepatitis; all 11 feces from days 8 to 15 were negative for HEV. Fecal concentrations of HEV appeared to be lower than those of many enteric viruses: only one specimen contained as many as 5 particles per EM grid square. It is concluded that HEV was etiologically associated with the epidemic and was predominantly excreted at very low levels during the first week of jaundice.

Negative staining in the detection of viruses in clinical specimens

Viruses have unique morphology and are therefore good candidates for negative staining. Negative staining with phosphotungstic acid (PTA) or uranyl acetate has facilitated the detection of many viruses in clinical specimens. Enhancement procedures have included the use of centrifugation and agar diffusion for concentrating virus particles, the use of solid phase capture reagents to trap virus particles and the use of secondary antibodies and electron dense markers to help visualize them. Techniques currently in use and employing negative staining include direct EM, immune electron microscopy (IEM), solid phase immune electron microscopy (SPIEM), colloidal gold-labeled protein A (PAG), solid phase IEM employing a second decorator antibody (SPIEMDAT), and solid phase IEM using colloided gold-labeled secondary antibodies (SPEIMDAGT). IEM methods assist with the detection of small viruses or viruses present in low numbers while PAG offers increased sensitivity over direct EM and IEM. In our experience the serum-in-agar (SIA) method is the most sensitive of the PAG IEM techniques for detection of rotavirus particles in clinical specimens. SPIEMDAT enhances the detection of small viruses which are often missed by other techniques due to background staining in specimens. SPEIMDAGT employing colloidal gold-labeled secondary antibody has increased sensitivity and offers the advantage of detecting viral antigen when whole virus particles are not visible. IEM techniques have recently been used for typing viruses using either monospecific antisera or monoclonal antibodies and colloidal gold-labeled secondary antibody.

Enterically transmitted non-A, non-B hepatitis: recovery of virus-like particles from an epidemic in south Delhi and transmission studies in rhesus monkeys

An epidemic of viral hepatitis, serologically characterized as due to non-A, non-B hepatitis, occurred in a village of South Delhi, India, in December, 1986, through January, 1987. Water contaminated with fecal matter was the apparent source of infection. Disease-associated virus-like particles were detected by immune electron microscopy in the feces of three patients within 5 days of illness. The virus-like particles were agglutinated by autologous acute-phase serum but not by convalescent serum. Rhesus monkeys inoculated with particle-containing fecal suspensions developed biochemical and morphologic features of acute, self-limited hepatitis. The findings in the present study and in earlier investigations of sporadic non-A, non-B hepatitis suggest that (i) the epidemic form and a proportion of sporadic cases of this infection in India may be related, both being enterically transmitted and associated with infection by a 27- to 32-nm virus-like particle, (ii) antibody responses to this virus occur early in disease and are transient and (iii) the rhesus monkey may prove to be a suitable model for studies of epidemic non-A, non-B hepatitis.

Enterically transmitted non-A, non-B hepatitis in cynomolgus monkeys: morphology and probable mechanism of hepatocellular necrosis

Two cynomolgus monkeys were inoculated with a stool extract originally derived from patients suffering from enterically transmitted non-A, non-B hepatitis. Subsequently, the primates developed self-limiting acute hepatitis and their liver tissues were obtained sequentially by needle biopsy or at sacrifice. Histologically, the liver tissues exhibited necroinflammation which appeared in parallel, both in time and magnitude, with elevation in serum aminotransferases. Necroinflammation was characterized by focal dropout of hepatocytes with accumulation of lymphocytes and macrophages. These lymphocytes were positive for a cytotoxic/suppressor immunophenotype. The hepatocytes surrounding these focal necroses showed depletion of glycogen granules and decrease in glucose-6-phosphatase and succinic dehydrogenase activities. Ultrastructurally, damaged hepatocytes around the focal necroses revealed marked dilatation of both rough and smooth endoplasmic reticula, swelling and disruption of the mitochondria and leakage of nuclear materials into the cytoplasm. Frequently, direct contact between the damaged hepatocytes and lymphocytes was noted. Virus-like particles measuring about 27 nm in diameter were observed singly or in small groups within the cytoplasm of damaged hepatocytes. Primary hepatocyte culture of a cynomolgus monkey, inoculated with a transmissible stool extract did not show any cytopathic change, although similar virus-like particles were recognized ultrastructurally in the cultured hepatocytes. Morphological analysis of in vitro and in vivo transmission studies in cynomolgus monkeys strongly supported the hypothesis of immune-mediated hepatocytolysis rather than a direct cytopathic effect of this hepatitis virus.

Epidemics of non-A, non-B hepatitis in Pakistan

Three epidemics of acute viral hepatitis which occurred in different areas of Pakistan, namely Quetta, Mardan and Rawalpindi were studied. All the cases presented with jaundice, anorexia and nausea. The liver function tests showed raised serum bilirubin, alkaline phosphatase and ALT levels. In all the patients except one, the serology was consistent with non-A, non-B (NANB) hepatitis, which was most likely waterborne. This study shows that, as in some other parts of Asia and North Africa, epidemics of waterborne NANB hepatitis, clinically resembling hepatitis A, also occur in Pakistan. These epidemics are probably due to faecal contamination of the water supply systems in some areas of Pakistan.

Aetiological association of a virus-like particle with enterically transmitted non-A, non-B hepatitis

Virus-like particles, approximately 27 nm in diameter, were identified in faeces from an Indian patient with enterically transmitted non-A, non-B (ENANB) hepatitis. They were serologically distinct from hepatitis A virus (HAV). Nucleic acid extracted from the particles did not hybridize with cDNA probes representing the genomes of HAV, enteroviruses, and cardioviruses. Chimpanzees were experimentally inoculated with faecal suspensions containing this 27 nm particle or with faeces from another case of ENANB hepatitis. Mild histological and biochemical hepatitis developed in these animals and there was serological evidence of infection with the virus-like particle as shown by immunoelectronmicroscopy (IEM). Serological analysis by IEM suggested that this agent or an antigenically similar virus was the aetiological agent of two epidemics and a sporadic case of ENANB hepatitis in India and of an epidemic of the illness in the USSR. Antibody to the particle was found in sera from patients with ENANB hepatitis from various geographic areas over a 30-year period.