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Biomedical subjects

H A Fields

Publications and source records attributed to H A Fields.

At least 55 records · Page 3Linked to original sources
PubMed1994

Chemiluminescent hybridization assay for hepatitis delta virus RNA in serum.

A nonradioactive hybridization assay for the detection of hepatitis delta virus RNA in serum is described. This assay utilizes a digoxigenin-labeled RNA hybridization probe and chemiluminescent immunodetection. The probe can detect as little as 0.4 pg of cDNA with a 60-min exposure. Results obtained are in agreement with serological indicators of hepatitis delta virus infection and are comparable to those obtained by hybridization assays employing radioactively labeled RNA.

Evaluation Studies as Topic↗
PubMed1994

Artificial mosaic protein containing antigenic epitopes of hepatitis E virus.

A synthetic gene encoding an artificial polypeptide composed of antigenic epitopes of the hepatitis E virus (HEV) proteins was constructed from short oligodeoxyribonucleotides by using PCR. The polypeptide comprises a mosaic of three antigenically active dominant regions from the protein encoded by open reading frame 2 (ORF2), one antigenically active region from the protein encoded by ORF3 of the Burmese HEV strain, and one antigenically active region from the protein encoded by ORF3 of the Mexican HEV strain. The mosaic protein was expressed in Escherichia coli as a chimera with glutathione S-transferase or beta-galactosidase. Guinea pig sera containing antibodies to the corresponding HEV synthetic peptides were used to demonstrate by Western immunoblot analysis and enzyme immunoassay the presence and accessibility of all HEV-specific antigenic epitopes introduced into the mosaic protein. Both the glutathione S-transferase and beta-galactosidase hybrid proteins were analyzed by using a panel of human anti-HEV-positive and -negative sera. The data obtained strongly indicate a diagnostic potential for the mosaic protein.

Amino Acid Sequence↗
PubMed1993

Synthetic gene for the hepatitis C virus nucleocapsid protein.

A synthetic gene encoding the hepatitis C virus (HCV) nucleocapsid protein was constructed and expressed in E. coli. To synthesize this gene, we developed a new method that results in the enzymatic synthesis of long polydeoxyribonucleotides from oligodeoxyribonucleotides. The method, designated as the 'Exchangeable Template Reaction' (ETR), uses oligonucleotides as templates for DNA polymerase. A special mechanism was designed to exchange the templates during the polymerase reaction. The mechanism relies on the formation of a single-stranded 3'-protrusion at the 'growing point' of the elongating DNA such that it can be subsequently annealed, in a sequence-specific manner, with the next synthetic oligonucleotide. When annealed to the 3'-protrusion, the added oligonucleotide becomes a template for DNA polymerase, and the protruding 3'-end of the double-stranded DNA is used as the primer. The HCV nucleocapsid gene was assembled with DNA ligase from three fragments synthesized by ETR. The data verify that this method is efficient. The main advantage of ETR is the ability to combine more than two oligonucleotides in one tube together with polymerase and an enzymatic activity that produces a 3'-protrusion (e.g., BstXI) rather than the sequential addition of each component. The data demonstrate that as many as five oligonucleotides can be used simultaneously, resulting in a synthesized DNA fragment of designed sequence. The synthetic gene expressed in E. coli produced a 27 kDa protein that specifically interacted with antibodies from sera obtained from HCV-infected individuals.

Amino Acid Sequence↗
PubMed1993

Epitope mapping in proteins of hepatitis E virus.

A series of synthetic peptides derived from proteins encoded by open reading frames 2 and 3 (ORF2 and ORF3) of the hepatitis E virus was used in an enzyme immunoassay to determine the localization of epitopes in these proteins. Five peptides spanning almost the entire ORF3 protein sequence and 12 peptides from the ORF2 protein were synthesized. Serum samples collected from outbreaks in three different regions of the world (Turkmenistan, Kenya, and Mexico) were analyzed by a peptide-based enzyme immunoassay. Primary analysis of the peptides was accomplished with the use of serum samples obtained from Middle Asia. Four of 5 peptides from the ORF3 protein and 4 of 12 peptides from the ORF2 protein specifically reacted with antibody from sera of HEV-infected patients. Peptides representing immunodominant epitopes were used for the analysis of serum samples from outbreaks in Kenya and Mexico. The data indicate that these synthetic peptides may be used to develop a diagnostic test to detect antibody to the hepatitis E virus.

Amino Acid Sequence↗
PubMed1993

A small open reading frame of the hepatitis delta virus antigenomic RNA encodes a protein that elicits antibodies in some infected patients.

A small open reading frame (ORF) was found in the hepatitis delta virus (HDV) antigenomic RNA encoding a short peptide that shares structural similarity with a region of the hepatitis B virus terminal protein. Analysis of all published HDV genome sequences indicates a high degree of conservation for the small ORF. This ORF is located at the 3'-terminal region of the gene encoding the hepatitis delta antigen (HDAg). We speculated that a peptide encoded by this ORF can be represented as the C-terminal domain of a new protein called HDAg'. This protein contains almost the entire sequence represented in the small form of HDAg and a peptide as an additional 'extension' sequence at the C-terminus. Two long synthetic peptides representing the two different types of peptides encoded by the small ORF were synthesized. These peptides were used for the development of an immunoassay for the detection of antibody to the HDAg' specific domain in sera of patients with HDV infection. Among 162 serum samples analyzed, 13 were found to be positive for an antibody reactive with these synthetic peptides. These antibodies were identified in patients with HDV infections and were not found in patients infected with hepatitis B virus, hepatitis C virus, or non-A,non-B,non-C virus. Thus, these data support the identification and existence of a new antigen encoded by the antigenomic RNA of the HDV.

Amino Acid Sequence↗
PubMed1993

Delta hepatitis: molecular biology and clinical and epidemiological features.

Hepatitis delta virus, discovered in 1977, requires the help of hepatitis B virus to replicate in hepatocytes and is an important cause of acute, fulminant, and chronic liver disease in many regions of the world. Because of the helper function of hepatitis delta virus, infection with it occurs either as a coinfection with hepatitis B or as a superinfection of a carrier of hepatitis B surface antigen. Although the mechanisms of transmission are similar to those of hepatitis B virus, the patterns of transmission of delta virus vary widely around the world. In regions of the world in which hepatitis delta virus infection is not endemic, the disease is confined to groups at high risk of acquiring hepatitis B infection and high-risk hepatitis B carriers. Because of the propensity of this viral infection to cause fulminant as well as chronic liver disease, continued incursion of hepatitis delta virus into areas of the world where persistent hepatitis B infection is endemic will have serious implications. Prevention depends on the widespread use of hepatitis B vaccine. This review focuses on the molecular biology and the clinical and epidemiologic features of this important viral infection.

Animals↗
PubMed1992

Hepatitis C virus in the etiology of chronic hepatitis and liver cirrhosis: possibility of mixed viral infections due to parenteral transmission.

Sera obtained from 381 patients with chronic liver disease from four cities within the USSR were studied for HBV, HDV, and HCV markers of infection. Anti-HCV activity was detected in 41.2% of non-A, non-B cases. The etiological distribution of chronic hepatitis in Moscow and Dushanbe was similar with an approximate 20% prevalence for HBV, HDV, and HCV infections, whereas in Yakutsk 40% of cases were caused by HDV infections. The etiology of disease remained unrecognized in approximately 40% of patients with chronic liver disease in Moscow and Dushanbe and in 15% in Yakutsk. Anti-HCV activity was detected in 18.8% of patients with chronic HBV infections and in 8.3% of patients with chronic HDV infections. Anti-HCV activity was detected in 41% of patients without markers of HBV or HDV infections. The reasons for the observed differences in HCV prevalence among patients chronically infected with HDV are discussed.

Hepacivirus↗
PubMed1992

Serologic identification of hepatitis E virus infections in epidemic and endemic settings.

Recombinant chimeric protein C2 containing the N-terminal region of trpE (37 kilodaltons [kDa]) and the C-terminal half (46.8 kDa) of the polypeptide encoded by ORF2 of the hepatitis E virus (HEV) genome was used for the construction of a Western blot diagnostic test for IgG and IgM antibodies to the virus (anti-HEV). (The C2 protein and the trpE protein devoid of C2 activity and used as a control for non-specific reactions were purified by recovery from sodium dodecyl sulfate-polyacrylamide gel electrophoresis [SDS-PAGE] and used for preparation of strips). Specificity of the test was proven with sera obtained from patients with acute hepatitis non-A, non-B, non-C (NANBNC) from outbreaks in different geographic regions of the world. IgG antibodies reactive to the recombinant C2 protein were detected in 93% of patients with acute hepatitis NANBNC and remained detectable in 89-100% of these patients 1-24 months after onset of jaundice. IgM antibodies were detected in 73% of patients within 26 days after onset of jaundice, in 50% 1-4 months after onset, in 6% 6-7 months after onset, and in no patients by 8 months after onset. When this test was used to identify sporadic hepatitis E cases in different regions of the world, such cases were found almost exclusively in areas where outbreaks of the disease had occurred and rarely in any other regions.

Adolescent↗
PubMed1991

Evaluation of enzyme immunoassay (EIA) as a screening method for hepatitis B markers in an open population.

Commercially available kits for detection of hepatitis B surface antigen (HBsAg) and hepatitis B surface antibody (anti-HBs) by enzyme immunoassay (EIA) were evaluated in American Samoa during a public health programme to eliminate the transmission of hepatitis B. The first 19,184 serum specimens obtained, representing 68% of the total cooperating population, were initially tested for anti-HBs, and those without detectable antibody were tested for HBsAg. All the antigen-positive serum samples, and a selection of the antigen- and antibody-negative specimens were tested by radioimmunoassay (RIA) for detection of both markers. Compared with the standard tests, the EIA kits for anti-HBs and HBsAg performed well; sensitivity and specificity were 90.3 and 96.0%, respectively, for antibody, and 97.8 and 97.9% respectively for antigen. Substantial disagreement between the EIA and RIA tests for HBsAg was found only for specimens considered weakly reactive by EIA. Few differences were found between three EIA method options for follow-up HBsAg testing of weakly reactive serum specimens; each option contributed about equally to improved test specificity for these 'borderline' specimens. Based on their demonstrated equivalence to the standard RIA tests, we conclude that the EIA kits for anti-HBs and HBsAg detection are suitable for use in hepatitis B control programmes in open populations.

Evaluation Studies as Topic↗
PubMed1990

Risk factors for acute non-A, non-B hepatitis in the United States and association with hepatitis C virus infection.

The Centers for Disease Control conducted intensive surveillance for acute non-A, non-B hepatitis in four sentinel counties over a 7-year period. Testing for antibody to hepatitis C virus was performed with the newly developed enzyme immunoassay. The incidence of non-A, non-B hepatitis remained relatively stable (average, 7.1 cases per 100,000, but there were significant changes in disease transmission patterns. The proportion of patients with a history of blood transfusion declined from 17% to 6%, but the proportion with a history of parenteral drug use increased from 21% to 42%. The proportion of patients with histories of sexual exposure (6%), household exposure (3%), occupational exposure to blood (2%), or hemodialysis (0.6%) did not change over time. Antibody to hepatitis C virus was found in 45% of patients within 6 weeks of onset of illness and in 68% of patients followed up for at least 6 months. Patients with no history of transfusions were just as likely to be positive for antibody to hepatitis C virus as patients with transfusion-associated hepatitis, indicating that hepatitis C virus is the major causative agent of all non-A, non-B hepatitis in the United States.

Acute Disease↗
PubMed1990

Immunoglobulin and hepatitis B surface antigen-specific circulating immune complexes in chronic hepatitis with hepatitis delta virus infection.

IgM, IgG, and HBsAg containing circulating immune complexes (CIC) were determined, by conglutinin (K) and C1q assays, for assessing the role of CIC in hepatitis delta virus (HDV) infection in 54 HBsAg-negative controls and 85 HBsAg-positive patients with chronic hepatitis. The prevalence of HDV markers (HDV antigen and anti-HD) was 24.70% (21/85). CIC were a common feature of HDV infection with 95.24% of patients having at least one abnormal test result. The prevalence of elevated IgM-K, IgG-K, IgM-C1q, and IgG-C1q CIC were 85.71, 85.71, 57.14, and 85.71%, respectively. The prevalence of IgM class CIC were statistically higher in patients with HDV infection than in those without (P = .001 for the K assay and P = .023 for the C1q assay). There was no difference in the prevalence of IgG class CIC. Patients with HDV infection also have significantly higher median levels of IgM K-CIC (P = .002), IgG K-CIC (P = .049), and IgG C1q-CIC (P = .008). In patients with HDV infection, there was positive correlation between IgM C1q-CIC and transaminase levels (r = .519, P = .016 for AST; r = .500, P = .021 for ALT). There was no difference in the prevalence of HBsAg containing CIC between patients with HDV infection (76.19%) and those without (74.60%). In conclusion, IgM class CIC are the major CIC and correlate with disease activity in HDV infection. CIC may play a role in the pathogenesis of HDV infection.

Adult↗
PubMed1990

Recovery of hepatitis A virus from a water supply responsible for a common source outbreak of hepatitis A.

An outbreak of hepatitis A occurred in a north Georgia trailer park served by a private well. Of 18 residents who were serosusceptible to hepatitis A virus (HAV), 16 (89%) developed hepatitis A. Well water samples were collected 3 months after illness onset in the index case and 28 days after illness onset in the last trailer park resident. Hepatitis A virus antigen (HAVAg) was detected in the samples by enzyme immunoassay from three of the five cell lines following two 30-day passages and from a fourth cell line following a third passage of 21 days.

Adult↗
PubMed1990

Hepatitis delta virus superinfection among patients with chronic hepatitis B in southern Taiwan.

To study the prevalence of hepatitis delta virus (HDV) superinfection among patients with chronic hepatitis in southern Taiwan, total and IgM anti-delta antibody (anti-HD) and delta antigen (HDAg) were determined in 85 histology-proven patients with chronic hepatitis. There were 12/85 (14.1%) cases with total anti-HD; 3 of them were also positive for IgM anti-HD. Another 9 (10.6%) cases were positive for HDAg. Thus, the prevalence of HDV superinfection was 21/85 (24.7%), which was significantly higher than previous reports in southern Taiwan. The difference was not seen if anti-HD was used as the only detector. It is concluded that, when other methods are used than previously, HDV infection is more common than previously thought and there is no difference between different parts of Taiwan.

Adult↗
PubMed1989

Seroepidemiology of hepatitis B virus infection in the United States. 1976 to 1980.

The prevalence of hepatitis B virus (HBV) infection was determined using sera from persons participating in the second National Health and Nutrition Examination Survey, conducted from 1976 to 1980. Of 14,488 scientifically selected participants aged 12 to 74, 821 had evidence of past or present infection with HBV. In the white population, the weighted estimate of hepatitis B infection was 3.2 percent (95 percent confidence interval, 3.1 to 4.2). A steady increase with age was seen; by ages 65 to 74, the prevalence was 6.9 percent (95 percent confidence interval, 5.2 to 8.5). In the black population, the overall weighted estimate of prevalence was 13.7 percent (95 percent confidence interval, 11.6 to 15.8). In this racial group, there was a dramatic increase with age, with the oldest age groups having a prevalence of 39.6 percent (95 percent confidence interval, 29.1 to 50.0). In both racial groups, there was a low prevalence of infection in young children that began to rise between ages 12 and 18. In a multivariate analysis of factors associated with infection, there was an interaction of race with age; therefore, the odds ratio for race is presented for four ages. This ratio ranged from 3.0 (95 percent confidence interval, 1.8 to 4.2) for a 15-year-old to 8.2 (95 percent confidence interval, 6.5 to 10.3) for a 70-year-old. These relative odds estimates were not substantially affected by adjustment for the available information on risk factors for HBV infection. The results of this study in a representative sample of the United States population show that adult black Americans are at high risk for hepatitis B infection. Other independent predictors of HBV positivity include male sex; residing in the South, Northeast, or West; residing in a city of 250,000 or more people; serving in the armed forces; living below the poverty level; and having a positive treponemal test for syphilis. These data suggest that the immunization practices for controlling this disease should be re-examined.

Adolescent↗
PubMed1989

Hepatitis D virus infection in Illinois state facilities for the developmentally disabled. Epidemiology and clinical manifestations.

OBJECTIVE: To define the epidemiology and clinical manifestations of hepatitis D virus infection in an institutionalized population. DESIGN: A case-control study of hepatitis B carriers with and without serologic evidence of hepatitis D virus infection. Demographic, institutional, and medical data were obtained through questionnaires and chart review. Clinical status was assessed by liver function assays. SETTING: Thirteen Illinois state facilities for the developmentally disabled. PARTICIPANTS: Clients (238) who were hepatitis B carriers. RESULTS: Antibody to hepatitis D virus (anti-HDV) was detected in 71 of 238 (30%) hepatitis B carriers. Nine of thirteen facilities housed positive clients. Previous residence at one facility, designated B, was the strongest correlate of anti-HDV positivity; 85% of positive persons had lived there compared with 16% of negative controls (odds ratio 28.3 [95% CI, 13.2 to 60.7], P less than 0.001). Past hepatitis episodes were more common among anti-HDV-positive clients (37% compared with 7%) (odds ratio, 7.5 [95% CI, 3.0 to 19.1], P less than 0.001) and occurred mainly at facility B from 1950 to 1975. Liver function tests were infrequently abnormal among anti-HDV-positive clients. CONCLUSIONS: Results show widespread hepatitis D virus infection in our institutionalized population and suggest that transmission occurred mainly in the past at the overcrowded facility B. The low prevalence of laboratory evidence of chronic liver disease in the anti-HDV-positive clients may be explained by increased mortality among those originally infected from 1950 to 1975.

Acute Disease↗
PubMed1989

Delta hepatitis in homosexual men in the United States.

To assess the incidence and prevalence of delta hepatitis in homosexual men, we tested serum specimens for delta markers in participants in two previous studies: a hepatitis B vaccine trial among homosexual men conducted in the early 1980's and the Centers for Disease Control sentinel counties hepatitis study for 1983-1984. In the vaccine trial, men found to be hepatitis B surface antigen positive at the time of enrollment and those men who had serologic evidence of new hepatitis B virus infection during follow-up were tested. In the sentinel counties study that determined risk factors for viral hepatitis in reported cases, all homosexual men with acute and chronic hepatitis B virus infections were tested for delta markers. Specimens were tested for delta antigen and IgM and total delta antibody. In seven different cities, among 321 men found to be HBsAg positive at the time of screening, eight (2%) were positive for any delta marker. Among 290 men with new hepatitis B virus infections during follow-up, three (two coinfections, one superinfection) had serologic evidence of delta hepatitis. In the sentinel counties study, 0/63 acute hepatitis B virus infections in homosexual men were associated with delta hepatitis. This study indicates that the delta agent is an infrequent cause of viral hepatitis in homosexual men in the United States.

Hepatitis D↗
PubMed1989

Replication kinetics and cytopathic effect of hepatitis A virus.

The replication kinetics and c.p.e. of hepatitis A virus (HAV) strain HM-175 were shown to depend upon the passage level of the cell line, and the passage level and method of selection of the virus population. Maximum virus production under single-step growth curve conditions occurred as early as 24 to 28 h or as late as 10 days post-infection. Although rapid replication of an isolate of HM-715 (pHM-175) occurred initially in BS-C-1 cells, its most pronounced c.p.e. was induced in FRhK-4 cells. The replication kinetics of pHM-175 in BS-C-1 cells were similar to those in FRhK-4 cells, although a higher yield of virus was obtained in the latter. The HAV that generated c.p.e. in FRhK-4 cells was obtained by two different selection processes: virus passage, or cloning of large focus-forming variants from the radioimmunofocus assay. The c.p.e. and yield of infectious pHM-175 in FRhK-4 cells could be reduced by 3 mM-guanidine. Another HAV isolate, strain MD-1, isolated directly from contaminated ground water in cell culture demonstrated c.p.e. in FRhK-4 cells after passage as persistently infected A-549 cells.

Animals↗