Biomedical subjects

K Krawczynski

Publications and source records attributed to K Krawczynski.

At least 19 recordsLinked to original sources

PubMed1996

Effect of immune globulin on the prevention of experimental hepatitis C virus infection.

The efficacy of postexposure prophylaxis for the prevention of hepatitis C virus (HCV) infection was studied in experimentally infected chimpanzees. Three chimpanzees were inoculated with HCV: Two were treated 1 h later with anti-HCV--negative intravenous immune globulin (IGIV) or hepatitis C immune globulin (HCIG), and a third animal was not treated. HCV infection was detected in all 3 animals within a few days of inoculation. Once passively transferred anti-HCV declined in the HCIG-treated animal, there was an increase of HCV antigen (Ag)--positive hepatocytes followed by reappearance of anti-HCV; HCV Ag disappeared concordant with the development of acute hepatitis. Acute hepatitis C developed in both the IGIV-treated and untreated chimpanzees, with peak liver enzyme activity on day 59, but was delayed in the HCIG-treated animal until day 146. Postexposure HCIG treatment markedly prolonged the incubation period of acute hepatitis C but did not prevent or delay HCV infection. IGIV had no effect on the course of HCV infection.

Animals↗

PubMed1995

Volunteer blood donors with antibody to hepatitis C virus: clinical, biochemical, virologic, and histologic features. The Hepatitis C Study Group.

OBJECTIVE: To assess the clinical significance of antibody to hepatitis C virus (anti-HCV) in volunteer blood donors. DESIGN: Prospective cohort study. SETTING: National Institutes of Health Clinical Center, a tertiary referral research hospital. PATIENTS: 60 anti-HCV-positive blood donors, divided into three groups of 20 persons each: Group I had normal alanine aminotransferase levels, group II had levels elevated to values less than twice the normal range, and group III had levels elevated to values greater than twice the normal range. MEASUREMENTS: Medical history, results of laboratory and virologic testing, and percutaneous liver biopsy findings. RESULTS: Participants with normal alanine aminotransferase levels were older and more often female than those with abnormal levels. The source of infection, duration of disease, symptom score, and amount of alcohol consumed were similar in the three groups. Hepatitis C virus RNA was detectable in 85% of participants, more commonly in the groups with elevated alanine aminotransferase levels (95%) than in the group with normal levels (65%); however, titers were similar in all groups. Examination of liver biopsy specimens showed chronic hepatitis in 54 participants (90%) and cirrhosis in 1 participant. The only normal liver biopsy specimens (n = 3) were those from participants who were HCV RNA negative and had normal alanine aminotransferase levels. CONCLUSIONS: Most blood donors with anti-HCV have chronic hepatitis C regardless of their serum alanine aminotransferase levels. Donors with normal alanine aminotransferase levels and no HCV RNA in their serum generally have normal liver histologic findings or minimal changes and have probably recovered from HCV infection.

Adult↗

PubMed1994

Case report: role of hepatitis E virus in the etiology of community-acquired non-A, non-B hepatitis in Greece.

The aim of this study was to determine the frequency of hepatitis E virus (HEV) infection in a population of Greek adults with community-acquired (sporadic) non-A, non-B hepatitis found to be seronegative for antibodies to hepatitis C virus (anti-HCV). All patients admitted to the Liver Unit of Western Attica General Hospital and diagnosed as having acute community-acquired non-A, non-B hepatitis between February, 1986, and May, 1990, were enrolled in follow up studies (n = 66). Nineteen patients with HCV infection and 11 patients with acute non-A, non-B, non-C hepatitis that progressed to chronicity were excluded. Convalescent sera were tested for antibody to HEV (anti-HEV) by a fluorescent antibody blocking assay in 33 of 36 eligible patients. One of the 33 (3%) patients was found to be positive for anti-HEV. Anti-HEV testing of all 20 available serum specimens from this patient showed evidence of anti-HEV seroconversion at the fourth week after the onset of hepatitis. The patient had not travelled abroad or within Greece or had not had apparent contact with people from foreign countries for the previous 3 months. These data show that HEV infection is not a major cause of community-acquired non-A, non-B hepatitis in Greece. However, the reported case of HEV hepatitis suggests that HEV may retain a low endemicity in Greece. More extensive seroprevalence studies are needed for an accurate estimation of the extent of HEV infection in the southeastern European countries.

Adolescent↗

PubMed1994

Effect of postexposure vaccination in a chimpanzee model of hepatitis A virus infection.

Passive transfer of antibodies to hepatitis A virus (HAV) in immune globulin (IG) effectively prevents hepatitis A when given after exposure, but does not provide lasting protection from infection. Hepatitis A vaccines have been shown to generate quickly levels of antibody equivalent to those found after IG administration. The effect of hepatitis A vaccine in preventing infection following fecal-oral exposure was evaluated in a chimpanzee model of HAV infection. Two animals were vaccinated 1 and 3 days, respectively following inoculation and two inoculated animals served as unprotected controls. Of the two immunized animals, one had no evidence of HAV infection, while the other had an attenuated infection with no evidence of virus shedding. These results suggest that while postexposure hepatitis A vaccination may be infection permissive, it attenuates disease expression and prevents virus shedding.

Alanine Transaminase↗

PubMed1994

Viral specificity of hepatitis E virus antigens identified by fluorescent antibody assay using recombinant HEV proteins.

A fluorescent antibody (FA) assay for hepatitis E virus antigen (HEVAg) in infected liver tissue was used to confirm the presence of virus-specific antigens in hepatocytes during the course of infection. With the cloning of the HEV genome it is now possible to determine which viral antigens are recognized by this FA assay. Recombinant HEV proteins covering the carboxyl half of HEV open reading frame 2 (ORF2) were used in this study to demonstrate that some of the most immunoreactive virus-specific antigens detected by FA are contained within this region of ORF2 (nucleotides 6169-7126).

Animals↗

PubMed1994

Hepatitis E.

With the introduction of new, albeit noncommercial, diagnostic tests for the detection of HEV, our understanding of this virus has been greatly enhanced. With these tests, it has been possible to begin a delineation of the process of pathogenesis in infected humans. These tests have also shown us that, at least in some individuals, an IgG response to HEV is long lasting and may confer immunity, and it may be possible to develop a recombinant vaccine against HEV. Contrary to past results, HEV appears to be the most common cause of acute sporadic hepatitis in pediatric populations in endemic regions. HEV has been shown to be a positive-sense single-stranded RNA virus that has been tentatively classified as a calicivirus, although its nonstructural proteins exhibit sequence similarity to rubella virus and furoviruses. Despite these advances in our understanding of HEV, it is still necessary to depend on exclusion of hepatitis caused by other viruses to diagnose a hepatitis E infection; however, this situation should change with the anticipated release of commercially available diagnostic tests.

Child↗

PubMed1993

Hepatitis E and hepatitis C virus infections among French soldiers with non-A, non-B hepatitis.

Serologic markers of HCV and HEV were investigated in 74 French soldiers with non-A, non-B hepatitis and in 18 patients involved in an outbreak of non-A,non-B hepatitis in Algeria. Moreover, anti-HCV antibodies were detected in 13 patients with non-A,non-B hepatitis of parenteral origin. HEV antibodies were investigated in 61-65% of patients involved in the 2 enterically transmitted outbreaks of non-A,non-B hepatitis observed in Algeria and Chad. The third cluster of non-A,non-B hepatitis observed in French soldiers serving in French Guyana is more likely to be attributed to malaria prophylactic treatment with Amodiaquine than to a viral origin. HCV infection was observed in 93% of acute or chronic cases associated with blood transfusion or parenteral drug abuse. Among acute cases, none of the soldiers who contracted the disease in Africa or in French Guyana was found to be anti-HCV positive compared to 78% of those who contracted the disease in France. HCV infections resulted in chronic hepatitis in 61% of cases.

Adult↗

PubMed1993

Preliminary evidence that a trpE-HEV fusion protein protects cynomolgus macaques against challenge with wild-type hepatitis E virus (HEV).

Immunization of two cynomolgus macaques (cynos) with trpE-C2 protein, a trpE-HEV fusion protein that represents the carboxyl two thirds of the putative capsid protein, prevented development of biochemical evidence of viral hepatitis in these primates after challenge by wild-type HEV from either a Burmese or Mexican stool isolate. Neither of the immunized animals showed any elevation of alanine aminotransferase activity after challenge with wild-type HEV in marked contrast with the unimmunized (control) cynos. In the case of the Burmese HEV challenged cyno, the protective effect was complete with the animal failing to demonstrate any evidence of HEV infection. The immunized cyno challenged with Burmese HEV did not exhibit any HEV RNA in its stools or HEV antigen in its liver. The immunized cyno (#8902) challenged with Mexican virus exhibited HEV RNA in its stools and HEV antigen in its liver; however, microscopic examination of liver biopsy specimens from this cyno failed to detect histopathologic evidence of viral hepatitis. All of the animals (naive and immunized) developed anti-HEV IgM and IgG responses after HEV challenge. Our preliminary studies indicate that the trpE-C2 protein is a promising candidate HEV vaccine.

Animals↗

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

Changes in hepatitis C virus antigen in liver with antiviral therapy.

BACKGROUND: Although it has recently become possible to detect hepatitis C viral antigens in liver biopsy specimens, the frequency and clinical significance of this finding remains uncertain. Therefore, 49 liver biopsy specimens from 35 patients with hepatitis C were studied to make these assessments. METHODS: Hepatitis C virus antigen was detected by immunofluorescence staining of snap-frozen liver biopsy sections. RESULTS: Hepatitis C virus antigen was present in 86% of patients; the amount and pattern of hepatitis C virus antigen staining did not correlate with the degree of hepatic injury as assessed by serum aminotransferase levels or liver histology or with the level of viral replication assessed by the titer of HCV RNA in serum. Patients who had a beneficial response to antiviral therapy had significantly less hepatitis C virus antigen staining in pretreatment liver biopsy specimens than those who did not respond. The degree of hepatitis C virus antigen staining decreased significantly following interferon alfa therapy but not after ribavirin therapy. Hepatic hepatitis C virus antigen became undetectable after therapy in those patients who had a long-term beneficial response to therapy. CONCLUSIONS: Hepatic hepatitis C virus staining may be useful in predicting and monitoring the response to antiviral therapy.

Adult↗

PubMed1993

Hepatitis E virus infection in pregnancy in Ethiopia.

Thirty-two pregnant and 34 nonpregnant Ethiopian women between 15 and 45 years of age with sporadic acute viral hepatitis were studied consecutively. Demographic data including family size, monthly income and nutritional status as well as hepatitis virus markers were compared in the pregnant and nonpregnant groups. Only 3 nonpregnant women had hepatitis A infection. Hepatitis B infection was diagnosed in 4 pregnant and 9 nonpregnant women. Nineteen (59%) pregnant women had hepatitis E virus (HEV) infection as compared to 7 (22%) in the nonpregnant group (Relative risk = 2.88; 95% Confidence interval = 1.4-5.9). The remaining 9 pregnant and 15 nonpregnant women had non-A, non-B, non-E (NANBNE) hepatitis. Of a total of 10 maternal deaths, 9 occurred (7 during the third trimester) in the pregnant group, 8 in association with HEV infection. Two deaths, one from each group, were due to NANBNE hepatitis. In addition to 6 foetal losses as a result of maternal death, there were 2 foetal deaths and 7 premature deliveries as a direct result of acute viral hepatitis, all but 2 associated with HEV infection. Comparison of socioeconomic and nutritional status, clinical features, mean aminotransferase and bilirubin levels did not show differences in the two groups. Thus, pregnant women are more at risk to acquire HEV infection than nonpregnant women and HEV infection in this group of Ethiopian pregnant women is associated with high maternal mortality and neonatal complications.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗

PubMed1993

Hepatitis E.

Explore the source record for details and available documents.

Animals↗

PubMed1992

The natural history of community-acquired hepatitis C in the United States. The Sentinel Counties Chronic non-A, non-B Hepatitis Study Team.

BACKGROUND: Chronic liver disease develops in more than half of patients with post-transfusion hepatitis C, but little is known about the natural history of community-acquired hepatitis C. METHODS: In 1985 and 1986 we identified adults with acute non-A, non-B hepatitis in four counties in the United States and followed them prospectively. We used three markers to detect hepatitis C virus (HCV) infection in stored samples of serum: antibody to HCV (anti-HCV) detected by second-generation serologic assays; HCV RNA detected by polymerase-chain-reaction assay; and antibody to HCV antigen (anti-HCVAg) detected by fluorescent-antibody-blocking assay. RESULTS: Of 130 patients with non-A, non-B hepatitis, 106 (82 percent) had HCV infection, 93 were positive for anti-HCV, and 13 were positive only for HCV RNA or anti-HCVAg. Chronic hepatitis developed in 60 (62 percent) of 97 HCV-infected patients followed for 9 to 48 months, with no relation to the risk factors for infection. Ten of the 30 patients who had liver biopsies had chronic active hepatitis. In samples collected 42 to 48 months after the onset of hepatitis, HCV RNA was detected in 12 of 13 tested patients with chronic hepatitis and in all 15 tested patients with hepatitis that had resolved. Anti-HCV persisted in all but two of the initially positive patients, for a rate of antibody loss of 0.6 per 100 person-years. CONCLUSIONS: Patients with community-acquired hepatitis C have a high rate of chronic hepatitis. HCV may be a major cause of chronic liver disease in the United States, and in most patients HCV infection seems to persist for at least several years, even in the absence of active liver disease.

Adolescent↗

PubMed1992

Human linear B-cell epitopes encoded by the hepatitis E virus include determinants in the RNA-dependent RNA polymerase.

Hepatitis E virus is responsible for both sporadic and epidemic hepatitis in developing countries. The nonenveloped virus is 27-34 nm in diameter and has been shown to contain a single-strand, positive-sense, polyadenylylated RNA genome of approximately 7.5 kilobases. The nucleotide sequence of the Burma strain of hepatitis E virus has been reported and three open reading frames (ORFs) have been identified. The deduced amino acid sequence from each of these ORFs was used to synthesize overlapping peptides (decamers overlapping at every fourth amino acid) on a solid phase. These peptides were then tested in an ELISA with pooled acute-phase sera from known cases of enterically transmitted non-A, non-B hepatitis collected in the Sudan. Linear B-cell epitopes were identified in all three ORFs. Epitopes were identified throughout the polyprotein encoded by ORF1, but they appeared to be particularly concentrated in the region of the RNA-dependent RNA polymerase. Distinct epitopes were identified in the presumed structural protein encoded by ORF2, and one epitope was identified close to the carboxyl terminus of the protein encoded by ORF3. These data precisely pinpoint linear B-cell epitopes recognized by antibodies from patients with acute hepatitis E and identify an antibody response directed against the RNA-dependent RNA polymerase.

Amino Acid Sequence↗

PubMed1992

Temporal relationships of hepatitis C virus RNA and antibody responses following experimental infection of chimpanzees.

Liver enzyme levels, viral RNA, and the immune response against both structural and nonstructural hepatitis C virus (HCV) proteins have been studied in experimentally infected chimpanzees in order to further understand the natural history of HCV infection. An ELISA for measuring both IgG and IgM responses to core (c22), 33c (NS3), and c100 (NS4) was employed. The IgG response rates were 5/8 for core, and 8/8 for both 33c and c100. Utilizing this antigen combination, at least one antibody response is measureable at, or within 3 weeks of, the major ALT peak. Although no individual antibody response is universally associated with initial detection of seroconversion, the combination of all three recombinant proteins measures seroconversion an average of 54 days earlier than with c100 alone, in 6/8 of the animals. IgM responses were measureable in 5/8 of the chimpanzees, were of shorter duration, and usually arose concomitantly with IgG responses. IgM appears to be a good indicator of primary infection since neither boosting nor recrudescence of disease during the chronic phase of disease elicited a secondary IgM response. Viral RNA can be measured 4-7 days (average = 9 days) postinfection with the period preceding the ALT peak being characterized by several PCR positive segments interrupted by periods in which no viral RNA can be measured. Following the ALT peak, chronically infected animals with recurring ALT elevations are generally PCR positive with intercedent PCR negative periods. Those animals that appear to have biochemically resolved disease generally have PCR negative profiles, although they still may periodically exhibit PCR positive sera. This indicates that with the recent advent of new screening techniques, a more stringent definition of HCV resolution will be required.

Animals↗

PubMed1992

Identification of HCV-associated antigen(s) in hepatocytes.

HCV-associated antigens (HCAg) were localized morphologically using immunofluorescence methods. Fluorescence was found in the cytoplasm of individual liver cells or in groups of cells. Nuclear fluorescence was not observed. Blocking and absorption studies suggest that HCAg is related to nucleocapsid or envelope proteins.

Animals↗

PubMed1992

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.

Animals↗

PubMed1992

Hepatitis C virus antigen in hepatocytes: immunomorphologic detection and identification.

Hepatitis C virus (HCV) antigen was detected immunohistochemically using fluorescein isothiocyanate-labeled immunoglobulin G fractions from chimpanzee and human sera strongly reactive with recombinant hepatitis C virus structural and non-structural proteins. The antigen was localized in the cytoplasm of hepatocytes in all 9 chimpanzees with acute hepatitis C, in 5 of 10 chimpanzees with chronic HCV infection, and in 11 of 12 patients with chronic hepatitis C. The specificity of the hepatocellular HCV and FITC-labeled probes for HCV was ascertained by blocking studies with paired serum samples obtained from 8 infected and uninfected chimpanzees or from 14 patients during the acute and chronic phases of HCV infection. Absorption experiments on FITC-labeled probes with selected host proteins (normal liver homogenate, plasma proteins, red blood cells) did not indicate cross reactivity of the probes with these antigens. Direct immunomorphologic evidence for the HCV specificity of hepatocellular HCV antigen deposits and the FITC-labeled polyclonal anti-HCVAg probe was established in absorption experiments using recombinant HCV nonstructural proteins. The putative HCV NS3 protein was the most prominent component of hepatocellular HCV antigen.

Adult↗