An outbreak of enterically transmitted non-A, non-E viral hepatitis

Synthetic rabbit-human antibody conjugate as a control in immunoassays for immunoglobulin M specific to hepatitis E virus

Background

In assays for anti-hepatitis E virus (HEV) immunoglobulin M (IgM), large volumes of the patient's sera cannot be easily obtained for use as a positive control. In this study, we investigated an alternative chemical method in which rabbit anti-HEV IgG was conjugated with human IgM and was used as a positive control in the anti-HEV IgM assay. Rabbit anti-HEV IgG was isolated from immune sera by chromatography on protein A-Sepharose and was conjugated with human IgM by using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) as a crosslinker.

Results

The specific anti-HEV IgG antibody titer was 100,000 times that of the negative control, i.e., prebleed rabbit serum. The results of anti-HEV IgM enzyme-linked immunosobent assay showed that the antibody conjugate was similar to anti-HEV IgM antibodies produced in humans. The results of a stability experiment showed that the antibody conjugate was stable for use in external quality assessment or internal quality control trials.

Conclusions

We concluded that the chemically conjugated rabbit-human antibody could be used instead of the traditional serum control as a positive control in the anti-HEV IgM assay.

Detection of TT virus by single-primer sequence-independent amplification in multiple samples collected from an outbreak of gastroenteritis

A panel of gastroenteritis outbreak samples was subjected to a virus purification and concentration algorithm followed by a sequence-independent amplification method devised to detect viral enteric pathogens. The application of these methods allowed the identification of torque teno virus (TTV) in one outbreak. The complete genome sequence of 3,260 nt was obtained through "genome walking", and four open reading frames were deduced from the genomic sequence. Phylogenetic analysis grouped this virus in TTV genetic group 3, clustering with genotype 27, with 85% similarity at the nt level with strain SAa-01.

Chapter 7 Global Supply of Virus-Safe Drinking Water

This chapter illustrates the recommendations and guidelines of the World Health Organization (WHO) concerning water, sanitation, and health. The recommendations and guidelines are evaluated in the light of disease caused by human pathogenic viruses. The guidelines outline a preventive management framework for safe drinking water. The framework includes health-based targets to assist national authorities who are normally responsible to set the targets for the protection of public health from risks by exposure to drinking water. Assessing the adequacy of systems, defining and monitoring control measures, and establishing management plans are the three components of the so-called water safety plans. Achievement of health-based targets may be verified by independent surveillance to assess the safety of the drinking water through additional verification or audit-based approaches. This framework for safe drinking water can be adapted according to environmental, social, economic, and cultural circumstances of drinking water provision on the national, regional, and local level. The chapter concludes that viruses could be considered as biocolloids with specific properties such as size, shape, structure, charge, composition, and genome. These viral characteristics determine their behavior in the environment, resistance to natural inactivation and treatment, and disinfection processes. For each (re-)emerging virus these properties may be known or could be assessed predicting the effectiveness of possible intervention measures for prevention of waterborne disease.

Replication of TT virus in hepatocyte and leucocyte cell lines

The TT virus (TTV) is a non-enveloped, single-stranded, circular, DNA virus, first isolated from a patient with hepatitis of unexplained etiology. The much deliberated pathological role of the virus continues to be conjectural in the absence of a suitable in vitro replication model. So far, the liver and the bone marrow have been shown to be the main sites of TTV replication. In this study, the human cell lines HepG2 and Chang Liver, the rat hepatoma cell line MH1C1, phytohemagglutinin (PHA)-stimulated TTV-negative peripheral blood mononuclear cell (PBMC) cultures and the B lymphoblast cell line, Raji were investigated as potential in vitro replication systems for TTV. The cell lines were infected with an inoculum prepared by pooling TTV genotype1 DNA positive sera and monitored for virus replication. Of the three hepatocyte cell lines, while the HepG2 and MH1C1 cell lines did not support TTV replication, the Chang Liver cell line showed clear morphological changes as a result of the in vitro infection, which included clumping and granular degeneration of the entire cell sheet over a period of 6 days. The infected cells also showed presence of virus-specific mRNA representative of viral transcription. The consistent presence of infectious viral particles in the supernatant culture fluid at 24-hr fluid replacement intervals indicated limited extra-cellular release of viral particles. The PHA-stimulated TTV-negative PBMC cultures and the Raji cell line were also able to support TTV replication and released significant levels of infectious viral particles into the supernantant culture fluid.

Successful rescuing a pregnant woman with severe hepatitis E infection and postpartum massive hemorrhage

AIM: To sum up the experience of the successful therapy for the severe hepatitis of pregnant woman with postpartum massive hemorrhage.

METHODS: The advanced therapeutic methods including the bilateral uterine artery embolism, hemodialysis and artificial liver support therapy were performed with comprehensive medical treatments and the course of the successful rescuing the patient was analyzed.

RESULTS: Through the hospitalization of about two mouths the patient and her neonatus had gotten the best of care in our department and pediatric department separately. Both of them were discharged in good condition.

CONCLUSION: The key points for a successful therapy of the pregnant woman with severe hepatitis are termination of the pregnancy and the control of their various complications. It was suggested that the proper combination of these measures of modern therapy would race against time for renewing of hepatic and renal functions.

Polymerase chain reaction-based prevalence of hepatitis A, hepatitis E and TT viruses in sewage from an endemic area

BACKGROUND/AIMS

Hepatitis A and E viruses (HAV, HEV) are transmitted enterically and are highly endemic in India. This study aims to evaluate prevalence of these and TT virus (TTV) in the sewage.

METHODS

Influent and effluent samples from a sewage treatment plant from Pune, India were collected twice a week for 1 year and subjected to nested polymerase chain reaction (PCR) for the detection of HAV RNA, HEV RNA and TTV DNA. HAV and HEV PCR products were sequenced. Effluent samples were not collected for 5 months as the plant was non-functional.

RESULTS

The overall prevalence was 24.42% (21/86, HAV), 10.98% (9/82, HEV) and 12.7% (8/63, TTV). Prevalence of HAV was significantly higher than HEV (P=0.023). During summer months, significantly higher HAV RNA positivity was noted (P<0.01). A substantial reduction in HAV RNA positivity (15/48 vs. 2/48, P=0.0008) was recorded for treated sewage samples. However, HEV RNA or TTV DNA positivity did not reduce significantly. Of the 17 HAV and HEV RNA negative sewage samples concentrated using ultracentrifugation, 13 and none were positive for HAV and HEV RNA, respectively. Phylogenetic analyses grouped these viruses in IB and Ia, respectively, the genotypes most prevalent in India.

CONCLUSIONS

Sewage may play an important role in maintaining hyper-endemicity of these infections. Sustained efforts are obligatory to render sewage less/non-infectious.

Novel variants related to TT virus distributed widely in China

TTV is a DNA virus with high genetic heterogeneity. To investigate the novel isolates of the virus, blood samples were collected from subjects who lived in various parts of China and suffered from hepatitis or were asymptomatic carriers. Nested PCR was carried out to amplify a 3.2-kb fragment using primers deduced from the prototype TTV (TA278). The ten entire 3.2-kb nt sequences were aligned with isolate TA278, SANBAN, TUS01, and SENV retrieved from GenBank, and a phylogenetic tree was constructed by Neighbor-Joining method. The analysis indicated that five novel variants of the present study have not been described before, and all TTV-related isolates could be classified into three groups. The isolate TCHN-A, B and TUS01 were included in a group, and the remaining novel isolates together with SANBAN and TA278 clustered into another group, while SEN virus formed a distinct group. The genetic distances of the five novel variants were 0.5507-0.8476 to TA278, 0.4635-0.7877 to SANBAN, 0.6064-0.7834 to TUS01 and 0.6936-0.8236 to SENV. Of these novel variants, the ORF1 consisted of 426-772 aa and ORF2 of 141-156 aa. The nt identities of ORF1 and ORF2 between those variants and TA278, SANBAN, and TUS01 were 46.1-60.8 and 48.7-63.6%, and those of aa sequences were only 27.1-52.4 and 28.9-45.5%, respectively. The first 65 aa of ORF1 were rich in arginine and most conserved with homology of 56.5-70.0%. There was a hypervariable region from aa 286 to 403 with merely 17.7-27.0% of identity. Despite a low aa identity between TA278 and the variants, they have similar hydrophilicity profiles of ORF1. There were 2-10 N-glycosylation motifs found in these variants. In conclusion, despite the high divergence, sequences of all these isolates shared common genome organisation, ORF structure, hydrophilicity patterns, and some potential motifs with TTV prototype. It is suggested that various TTV and TTV-related isolates belong to a very large and complex family, which remains to be studied.

Novel TTV variants isolated in an epidemic of hepatitis of unknown etiology

TT virus (TTV) is a recently discovered single-stranded DNA virus that has been reported to be associated with elevated transminase levels in the patients with posttransfusion hepatitis of unknown etiology. TTV prevalence is very high in the common population and its pathogenicity remains unclear. In this study, we performed an epidemiological study to investigate the infection rate of TTV and its role in an epidemic of unknown-etiology hepatitis. Moreover, two TTV isolates named L01 and L02 were cloned from the serum of a patient with unknown-etiology hepatitis. Eighty-one subjects were included in the study and were divided into two groups: 18 in the case group and 63 in the control group. TTVDNA was detected by nested PCR from sera samples. The infection rates of TTV in case and control groups were 33.3 and 38.9%, respectively. There was no significant difference between the two groups. Homology analysis showed that L01 had a very poor homology with other TTV isolates and L02, and L02 was 75.5% identical to JA10. The result does not support TTV as a causative agent in this epidemic. The genetic divergence between L01 and other TTV isolates beyond genotype, so it represents a new genotype of TTV.

Clinicopathological study on TTV infection in hepatitis of unknown etiology

AIM: To investigate the state of infection, replication site, pathogenicity and clinical significance of transfusion transmitted virus (TTV) in patients with hepatitis, especially in patients of unknown etiology.

METHODS: Liver tissues taken from 136 cases of non-A non-G hepatitis were tested for TT virus antigen and nucleic acid by in situ hybridization (ISH) and nested-polymerase chain reaction (PCR). Among them, TT virus genome and its complemental strand were also detected in 24 cases of autopsy liver and extrahepatic tissues with ISH. Meanwhile, TTV DNA was detected in the sera of 187 hepatitis patients by nested-PCR. The pathological and clinical data of the cases infected with TTV only were analyzed.

RESULTS: In liver, the total positive rate of TTV DNA was 32.4% and the positive signals were located in the nuclei of hepatocytes. In serus, TTV DNA was detected in 21.4% cases of hepatitis A-G, 34.4% of non-A non-G hepatitis and 15% of healthy donors. The correspondence rate of TTV DNA detection between liver tissue with ISH and sera with PCR was 63.2% and 89.3% in the same liver tissues by ISH and by PCR, respectively. Using double-strand probes and single-strand probes designed to detect TTV genome, the correspondence rate of TTV DNA detected in liver and extrahepatic tissues was 85.7%. Using single-strand probes, TTV genome could be detected in liver and extrahepatic tissues by PCR, but its complemental strands (replication strands) could be observed only in livers. The liver function of most cases infected with TTV alone was abnormal and the liver tissues had different pathological damage such as ballooning, acidophilia degeneration, formation of apoptosis bodies and focus of necrosis, but the inflammation in the lobule and portal area was mild.

CONCLUSION: The positive rate of TTV DNA among cases of hepatitis was higher than that of donors, especially in patients with non-A non-G hepatitis, but most of them were coinfected with other hepatitis viruses. TTV can infect not only hepatocytes, but also extrahepatic tissues. However, the chief replication place may be liver. The infection of TTV may have some pathogenicity. Although the pathogenicity is comparatively weak, it can still damage the liver tissues. The lesions in acute hepatitis (AH) and chronic hepatitis (CH) are mild, but in severe hepatitis (SH), it can be very serious and cause liver function failure, therefore, we should pay more attention to TTV when studying the possible pathogens of so-called “Liver hepatitis of unknown etiology”.

Occurrence of hepatitis E virus IgM, low avidity IgG serum antibodies, and viremia in sporadic cases of non-A, -B, and -C acute hepatitis

Serum samples were taken from 57 patients with sporadic non-A, -B, and -C (Non A, B, C) acute hepatitis at different times after onset of the disease and tested for the presence of the hepatitis E virus (HEV) RNA, IgM, and low avidity IgG antibodies. The viral antibodies were detected using two ELISA. One assay (GL) was produced using a mixture of recombinant peptides specified by ORF2 and ORF3 of the viral genome. The other was produced with an ORF2 specified peptide, pE2. The latter occurs naturally as homodimer, it is recognized strongly in its dimeric form by human sera and, in the primate model, it confers protection against experimental HEV infection. Nineteen samples were positive for one or more of these acute markers of HEV infection, 14 of which were acute sera with elevated ALT levels and 5 were convalescent sera with normal ALT level. The results showed that icteric phase of sporadic hepatitis lasts for about 17 days and it coincides with a period when viremia is subsiding as HEV antibodies are developing. Viremia was intermittent and all but one of the 5 instances were confined to the icteric phase with elevated ALT levels. On two of these occasions, viremia preceded detection of HEV antibody, on another 2 occasions it was concurrent with the detection of pE2 specific IgM and/or low avidity IgG and only in one case of protracted viremia was the viral genome detected concurrently with avid pE2 IgG antibody. Ten (71%) of the 14 acute sera were reactive for pE2 IgM, eight (57%) were reactive for low avidity pE2 IgG, and six (43%) for the GL IgM. The sensitivity for the diagnosis of acute hepatitis E may be increased to 87% by combining pE2 IgM and viremia. GL IgM was detected later, but persisted for a longer period of time than the pE2 antibodies, and it was the only acute antibody detected in the convalescent sera.

Molecular properties, biology, and clinical implications of TT virus, a recently identified widespread infectious agent of humans

TT virus (TTV) was first described in 1997 by representational difference analysis of sera from non-A to non-G posttransfusion hepatitis patients and hence intensively investigated as a possible addition to the list of hepatitis-inducing viruses. The TTV genome is a covalently closed single-stranded DNA of approximately 3.8 kb with a number of characteristics typical of animal circoviruses, especially the chicken anemia virus. TTV is genetically highly heterogeneous, which has led investigators to group isolates into numerous genotypes and subtypes and has limited the sensitivity of many PCR assays used for virus detection. The most remarkable feature of TTV is the extraordinarily high prevalence of chronic viremia in apparently healthy people, up to nearly 100% in some countries. The original hypothesis that it might be an important cause of cryptogenic hepatitis has not been borne out, although the possibility that it may produce liver damage under specific circumstances has not been excluded. The virus has not yet been etiologically linked to any other human disease. Thus, TTV should be considered an orphan virus.

Prevalence and phylogenetic analysis of TT virus DNA in Western India

In western India, TT virus (TTV) DNA positivity varied from 6.7% (5 of 75) in chronic hepatitis patients to 24.4% (10 of 41) in hemophiliacs; 7.4% (4 of 54) of voluntary blood donors had circulating TTV DNA. Phylogenetic analysis revealed a predominance of genotype 1a. In India, TTV is transmitted mainly by nonparenteral routes and is not an important cause of chronic liver diseases.

Intrahepatic transfusion-transmitted virus detected by in situ hybridization in patients with liver diseases

Transfusion-transmitted virus (TTV) has been identified from patients with post-transfusion hepatitis of unknown aetiology, but the clinical relevance remains unclear. The aim of this study was to evaluate TTV in liver. We studied 15 patients with hepatitis non-A-E and 44 with hepatitis B virus (HBV). The nested polymerase chain reaction (PCR) with primers corresponding to the conserved region of the published TTV genome was employed to amplify TTV fragments in serum, and in situ hybridization was used to detect TTV in biopsied liver specimens. TTV DNA was detected in serum from six (40%) of 15 patients with hepatitis of unknown aetiology and from 16 (36.4%) of 44 patients with chronic hepatitis B, respectively. The intrahepatic viral fragment was detected in 17 (77.3%) of 22 patients with TTV in serum. There was no statistical difference in the prevalence of TTV infection between the two groups (hepatitis non-A-E 40% vs HBV 25%, P > 0.75). When patients in both groups, with and without TTV, were compared, no differences were found in serum alanine aminotransferase (ALT) levels (hepatitis non-A-E: 131.5 +/- 66.6 vs 244.2 +/- 257.4, P=0.955; HBV: 240.1 +/- 418.9 vs 214.6 +/- 276.7 U l(-1), P=0.761) or histological activity index (grade) score (hepatitis non-A-E: 6.4 +/- 5.5 vs 5.6 +/- 5.9, P=0.689; HBV: 5.6 +/- 3.7 vs 5.5 +/- 3.7, P=0.345). HBV DNA levels in patients with and without TTV co-infection did not differ significantly (300 +/- 776.4 microg ml(-1) vs 97.1 +/- 160.5 microg ml(-1), P=0.980). Hence, TTV does exist in liver, but plays no role in hepatitis or aggravation of liver damage when co-infected with HBV.

Epidemiological survey and follow-up of transfusion-transmitted virus after an outbreak of enterically transmitted infection

An outbreak of enterically transmitted hepatitis occurred during 1996 among students at a vocational school. Viral fragments homologous to transfusion-transmitted virus (TTV) were detected in faeces. To elucidate the endemic status, an epidemiological survey and case follow-up after the outbreak were carried out. During and after the outbreak, virus carriers among staff were, respectively, 32.1% and 31.3% in serum, and 24.6% and 18.2% in faeces. After the last outbreak, attacks were still occurring among new students with an incidence of 2.4% in 1997 and 2.3% in 1998. There was also a small-scale outbreak in 1998 with a prevalence of 17.9%. On follow-up at 6 and 18 months after onset, alanine aminotransferase (ALT) elevation was found in 29.7% and 13.9% of patients. At 6 months, viral fragments were detected in serum in 78.1% and 46.7% of patients, with and without ALT elevation, respectively. At 18 months the corresponding figures were 55.6% and 19.2%, respectively. At the 18-month follow-up, viral fragments were detected in faeces in 29.6% and 19.3% of patients with and without ALT elevation. In conclusion, this disease might be transmitted from asymptomatic virus carriers. According to the laboratory data, both parenteral and non-parenteral transmissions are involved, and the faecal-oral route might be more important.

Experimental infection of nonenveloped DNA virus (TTV) in rhesus monkey

Virus fragments homologous to TTV were detected previously from an enterically transmitted outbreak of non-A-E hepatitis [Luo et al., 1999]. To test the susceptibility of the Rhesus monkey to this virus and to establish its transmission routes, 6 Rhesus monkeys were inoculated, 3 orally and another 3 intravenously. The inoculum was prepared by extracting and filtering feces collected from a patient during the incubation period identified in the described outbreak. A second group of 3 monkeys was used for the passage study. The feces and blood samples were collected for detection of the virus by polymerase chain reaction (PCR). Four animals were subjected to liver biopsies and bile aspiration by open surgery for in situ virus detection. Viremia occurred in 4-7 days after intravenous and 7-10 days after oral inoculation. The virus was excreted in feces a few days after oral infection and simultaneously with viremia after intravenous inoculation. The virus was also detected in bile during the viremic phase. There was a prolonged carrier state with persistent viremia and virus excretion in feces for more than 6 months. Serum transaminase levels were not raised during the infection. The virus was present in both the cytoplasm and nuclei of hepatocytes, but no significant pathology was found. Therefore, the Rhesus monkey is susceptible to TT virus infection, but the virus seems nonpathogenic. Infection of the liver may be established either by oral or parenteral inoculation. The virus may be released from liver into the blood or via bile into feces, so it may be transmitted by both blood and fecal routes.