Biomedical subjects
Publications and source records attributed to G J Dawson.
A patient who had recently traveled from India to Tennessee was found to have acute hepatitis E. Improved recognition and serologic testing have increased the diagnosis of hepatitis E in the United States. For those at risk, hepatitis E should be considered in the differential diagnosis of acute hepatitis.
Sequences from the putative 5' nontranslated region of GB virus A were isolated from mystax, owl monkeys, and tamarins. Though sequences of isolates from each animal species are virtually identical at the nucleotide level (95%), isolates from different species are dramatically different (52 to 79% identical) and genetically cluster on this basis.
The hepatitis E virus (HEV) is a cause of severe liver disease in humans, especially in developing countries. Several assays are available to detect the HEV genome and specific antibodies against HEV (anti-IgG, IgA and IgM). Different serological patterns enable the diagnostician to differentiate remote from recent infections. In order to avoid diagnostic errors based on incomplete serological diagnosis, these patterns are shown with their specific serological marker.
Explore the source record for details and available documents.
A subtractive PCR methodology known as representational difference analysis was used to clone specific nucleotide sequences present in the infectious plasma from a tamarin infected with the GB hepatitis agent. Eleven unique clones were identified, seven of which were examined extensively. All seven clones appeared to be derived from sequences exogenous to the genomes of humans, tamarins, Saccharomyces cerevisiae, and Escherichia coli. In addition, sequences from these clones were not detected in plasma or liver tissue of tamarins prior to their inoculation with the GB agent. These sequences were detected by reverse transcription-PCR in acute-phase plasma of tamarins inoculated with the GB agent. Probes derived from two of the seven clones detected an RNA species of > or = 8.3 kb in the liver of a GB-agent-infected tamarin by Northern blot hybridization. Sequence analysis indicated that five of the seven clones encode polypeptides that possess limited amino acid identity with the nonstructural proteins of hepatitis C virus. Extension of the sequences found in the seven clones revealed that plasma from an infected tamarin contained two RNA molecules > 9 kb long. Limited sequence identity with various isolates of hepatitis C virus and the relative positions of putative RNA helicases and RNA-dependent RNA polymerases in the predicted protein products of these molecules suggested that the GB agent contains two unique flavivirus-like genomes.
Two flavivirus-like genomes have recently been cloned from infectious tamarin (Saguinus labiatus) serum, derived from the human viral hepatitis GB strain, which is known to induce hepatitis in tamarins. In order to study the natural history of GB infections, further transmission studies were carried out in tamarins. Reverse-transcription-polymerase chain reaction and enzyme-linked immunosorbant assays were developed for the detection of RNA and antibodies associated with the two agents, GB virus-A and GB virus-B. The infectivity of both of these agents was demonstrated in tamarins to be filterable through a 0.1 micron filter. Two distinct genomes were identified in the serum of eight of the infected tamarins, while in four tamarins, the genomes were detected independently of each other. Although specific antibodies to the GB virus-B epitopes were detected in the serum of animals inoculated with both agents or GB virus-B alone, antibodies to putative epitopes specific to GB virus-A were not detected in any of the animals. All tamarins inoculated with serum containing GB virus-B exhibited an elevation in liver enzyme levels after inoculation. Elevations of serum liver enzyme levels did not occur when GB virus-A was the only agent detected in the serum. Infection with the original infectious tamarin inoculum conferred protection from reinfection with GB virus-B but not with GB virus-A.
Two viruses, GB virus A (GBV-A) and GB virus B (GBV-B), were recently identified in the GB hepatitis agent. Human sera containing antibodies that recognize GBV-A and/or GBV-B recombinant proteins were subjected to polymerase chain reaction studies with degenerate oligonucleotides capable of amplifying a segment of the putative helicase genes from GBV-A, GBV-B or hepatitis C virus. Novel sequences related to members of the Flaviviridae were identified in sera from 12 individuals including 4 individuals with hepatitis. The limited nucleotide sequence identity between GBV-A, GBV-B and HCV sequences suggests that a novel virus, tentatively named GB virus C, may be responsible for some cases of non-A, non-B, non-C, non-D, non-E hepatitis.
The genomes of two positive-strand RNA viruses have recently been cloned from the serum of a GB agent-infected tamarin by using representational difference analysis. The two agent, GB viruses A and B (GBV-A and GBV-B, respectively), have genomes of 9,493 and 9,143 nucleotides, respectively, and single large open reading frames that encode potential polyprotein precursors of 2,972 and 2,864 amino acids, respectively. The genomes of these agents are organized much like those of other pestiviruses and flaviviruses, with genes predicted to encode structural and nonstructural proteins located at the 5' and 3' ends, respectively. Amino acid sequence alignments and subsequent phylogenetic analysis of the RNA-dependent RNA polymerases (RdRps) of GBV-A and GBV-B show that they possess conserved sequence motifs associated with supergroup II RNA polymerases of positive-strand RNA viruses. On the basis of similar analyses, the GBV-A- and GBV-B-encoded helicases show significant identity with the supergroup II helicases of positive-strand RNA viruses. Within the supergroup II RNA polymerases and helicases, GBV-A and GBV-B are most closely related to the hepatitis C virus group. Across their entire open reading frames, the GB agents exhibit 27% amino sequence identity to each other, approximately 28% identity to hepatitis C virus type 1, and approximately 20% identity to either bovine viral diarrhea virus or yellow fever virus. The degree of sequence divergence between GBV-A and GBV-B and other Flaviviridae members demonstrates that the GB agents are representatives of two new genera within the Flaviviridae family.
The seroprevalence of antibodies to HEV was determined in three different Italian populations (volunteer blood donors, normal healthy individuals, and intravenous drug users [IVDUs]). The seroprevalence in the populations ranged from 0.74% to 1.94%, with higher rates among IVDUs and individuals over 40 years of age. None of 35 patients diagnosed with acute hepatitis A but 10 of 153 (6.5%) patients with acute nonA, nonB, nonC hepatitis were found to be positive for anti-HEV antibody. One of these antibody positive cases was linked to travel, while the remaining 9 were not associated with travel to endemic areas. These data suggest a possible low circulation of HEV in Italy.
A solid phase enzyme linked immunosorbent assay (ELISA) that detects IgM and IgG to hepatitis E virus (HEV) was used to study seroepidemiology in 40 healthy subjects and 227 consecutive patients with liver diseases in an endemic area. Fifty-two of the liver diseases patients (22.9 percent) had acute hepatitis E. In contrast, none of the 40 healthy subjects were positive for IgM anti-HEV, validating the ELISA assay. Twenty-three of 25 (92%) patients with epidemic non-A, non-B hepatitis were confirmed as having acute hepatitis E. Only 1 of the 10 patients with sporadic, fulminant hepatic failure of non-A, non-B, non-C etiology was positive for IgM anti-HEV. Five (31.2%) of the 16 patients with acute hepatitis in HBsAg carriers were positive for IgM anti-HEV. One patient with acute hepatitis B was coinfected with acute hepatitis E. Acute hepatitis was a disease of the adult population, with peak attack rates in the second and third decades of life. This disease was seen in only 4 (16%) of the 25 patients with acute viral hepatitis occurring below 14 years of age. Cholestasis was predominant in 25% of patients, enzyme elevation was monophasic, and all patients had clinical and biochemical recovery from the disease. The data suggest that the majority of patients with acute sporadic non-A, non-B, non-C hepatitis in India have hepatitis E. However, fulminant hepatic failure to sporadic nature is rarely from hepatitis E.
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.
Recombinant antigens from hepatitis E virus (HEV) open-reading frames 2 and 3 were expressed in Escherichia coli as cytidine monophosphate-2-keto-3-deoxyoctulosonic acid synthetase (CKS) fusion proteins, purified, and used to develop an EIA for the detection of antibodies. Serologic results were compared with those of previous assays by testing 102 samples from an HEV outbreak in Somalia. This CKS/HEV EIA detected anti-HEV in all 97 sera found reactive previously and in an additional 2 samples, which were shown to be true HEV-positive samples by supplemental peptide and Western blot tests. The CKS/HEV EIA and supplemental assays were then used to determine seroprevalence of HEV worldwide. HEV seroprevalence ranged from 1% to 25%, with higher rates found in Middle Eastern countries. Also, 7%-14% of acute cases of non-A, -B, or -C hepatitis were HEV-positive. Thus, this CKS/HEV EIA appears useful for detecting anti-HEV in various populations.
Explore the source record for details and available documents.
An outbreak of an acute sporadic viral hepatitis occurring at three villages in the lower Shebli region of southern Somalia was studied. Sera were examined for antibodies to hepatitis E virus (HEV) antigen by a recently developed enzyme-linked immunosorbent assay. The prevalence of anti-HEV ranged from 77.8% to 94.0% among the three villages. Anti-HEV prevalence did not differ significantly with age or sex. HEV infections were widely distributed among all age groups, without a preponderance in any specific age category. Overall, 97.6% of afflicted patients who were examined 6-10 days after onset of jaundice developed either IgM or IgG anti-HEV.
A newly developed assay for IgA class antibody to hepatitis E virus (IgA anti-HEV) was used to study 145 serum samples collected during an outbreak of an enterically transmitted hepatitis that occurred in 3 villages in the lower Shebeli region of Southern Somalia between January, 1988 and November, 1989. A total of 52.4% of the afflicted patients were found positive for IgA anti-HEV, and 73.1% of these were also positive for IgM. Both antibodies disappeared during the convalescence period. Similar results were also seen in serum obtained from sporadic cases of acute waterborne hepatitis in Pakistan.
OBJECTIVE: Markers of HIV disease progression such as soluble p24 antigen detection and CD4 lymphocyte depletion are most useful in the later stages of HIV disease and are relatively insensitive as therapeutic monitors. Flow cytometric detection of HIV-1 replication in CD4 lymphocytes was evaluated for use as a marker in predicting disease progression earlier in the course of HIV disease. DESIGN: To determine whether the number of HIV-1-infected CD4 cells, as measured by p24 antigen detection, can be correlated with disease progression, we used flow cytometry to detect intracellular HIV-1 p24 in CD4 lymphocytes from HIV-1-seropositive subjects at all stages of HIV disease. METHODS: Mononuclear cells from HIV-1-seropositive subjects and uninfected control subjects were permeabilized and stained with anti-HIV-1 p24 monoclonal antibodies. The cells were then stained with a fluorescein isothiocyanate-conjugated goat antimurine immunoglobulin G followed by a phycoerythrin-conjugated monoclonal anti-CD4 antibody. The percentage of p24-positive CD4 lymphocytes was compared with absolute CD4 counts, soluble p24 detection and Walter Reed classification. RESULTS: CD4 lymphocyte absolute counts and the percentage of CD4 lymphocytes declined as the Walter Reed classification indicated disease progression. The mean percentage of p24 antigen-positive CD4 lymphocytes increased with disease progression. Only 30% of Walter Reed stage 6 subjects were soluble p24 antigen-positive, whereas 68% were cellular p24 antigen-positive. CONCLUSION: The percentage of p24 antigen-positive CD4 lymphocytes increased as HIV disease progressed. Flow cytometric quantitation of p24 antigen-positive CD4 cells is a useful method of monitoring in vivo HIV replication and disease progression.
Explore the source record for details and available documents.
Recently, identification and molecular cloning of a host cellular gene designated GOR from chimpanzees experimentally infected with non-A, non-B hepatitis (NANBH) agent was reported. It was further demonstrated that there is a close association between the immune response to an antigenic peptide of GOR (GOR2) and NANBH. In order to define the specificity of the immune response, in the present study we have identified an additional epitope in the GOR gene sequence, upstream from GOR2, and studied its correlation with the immune response to hepatitis C virus (HCV) in NANBH patients. An enzyme-linked immunoassay (EIA) was developed which utilizes synthetic peptides designated spGOR346 and spGOR2 as the serological target for the detection of anti-GOR antibodies in patient serum samples from various hepatic and non-hepatic disease categories. GOR peptides identified 80-90% of the NANBH samples that were positive for HCV C100-3 and about 70% of the NANBH samples that were positive by Abbott prototype second-generation HCV antibody assay. Among a normal donor population(s), only 2-3% of the samples were positive for antibodies to GOR sequences, whereas from the patient categories unrelated to viral hepatitis as well as various nonhepatic diseases, the immune response to both GOR peptides was closely associated with the presence of antibodies to HCV. The data indicate that antibodies to GOR is a marker associated with NANBH.