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Biomedical subjects

L H Barbosa

Publications and source records attributed to L H Barbosa.

At least 19 recordsLinked to original sources
PubMed2001

Parvovirus B19: implications for transfusion medicine. Summary of a workshop.

This 1-day workshop showed that the infectivity of B19 DNA in donor blood and the neutralizing action of different antibodies present in the donated blood are not yet fully understood. It is possible that B19-induced anemia and reticulocytopenia are not being recognized in transfused recipients other than those in specific risk groups. The testing of blood components for any infectious agent is usually clinically driven, and, if B19 NAT were recommended at the present time in other than plasma products, a CMV-like model might prove appropriate; that is, virus screening would be performed on blood components destined for high-risk groups only. Currently, there is insufficient evidence to recommend universal testing, especially for single units. Workshop participants recommended that basic research continue in the scientific areas addressed. If clinical trials were to be developed, participants recommended that they include special risk groups such as seronegative pregnant women and children with malignancies who are receiving chemotherapy.

Animals↗
PubMed1997

An ELISA for detection of antibodies to the E2 protein of GB virus C.

An ELISA was developed for detection of antibodies to GB virus C (GBV-C) using a recombinant E2 protein expressed in CHO cells. Seroconversion to anti-E2 positivity was noted among several persons infected with GBV-C RNA-positive blood through transfusion. Of 6 blood recipients infected by GBV-C RNA-positive donors, 4 (67%) became anti-E2 positive and cleared their viremia. Thus, anti-E2 seroconversion is associated with viral clearance. The prevalence of antibodies to E2 was relatively low (3.0%-8.1%) in volunteer blood donors but was higher in several other groups, including plasmapheresis donors (34.0%), intravenous drug users (85.2%), and West African subjects (13.3%), all of whom tested negative by GBV-C reverse-transcription polymerase chain reaction (RT-PCR). These data demonstrate that testing for anti-E2 should greatly extend the ability of RT-PCR to define the epidemiology and clinical significance of GBV-C.

Africa↗
PubMed1996

Donor levels of serum alanine aminotransferase activity and antibody to hepatitis B core antigen associated with recipient hepatitis C and non-B, non-C outcomes.

BACKGROUND: Hepatitis virus(es) that are neither hepatitis B (HBV) nor hepatitis C (HCV) (non-B, non-C [NBNC]) may be transmitted by transfusion. The present study assessed donor values for alanine aminotransferase (ALT) and antibody to hepatitis B core antigen (anti-HBc) for their association with HCV and NBNC hepatitis outcomes among allogeneic blood recipients. STUDY DESIGN AND METHODS: Data on blood donors and recipients enrolled in the Transfusion- Transmitted Viruses Study in four United States cities from 1974 through 1980 were supplemented by anti-HBc testing of donors and anti-HCV evaluation of recipients. Two statistical approaches estimated the value of these indirect tests in detecting donors associated with HCV seroconversion and NBNC hepatitis in recipients. RESULTS: For HCV cases, donor ALT alone (at > or = 60 IU/L) had a sensitivity and a specificity of 30 and 96 percent, respectively, and anti-HBc alone (at > or = 60% inhibition) had a sensitivity and specificity of 53 and 86 percent, respectively. The two markers combined had a sensitivity and a specificity of 69 and 83 percent. For NBNC hepatitis cases, each measure had low sensitivity (20%) that was not improved by using both (28%) [corrected]. CONCLUSION: The indirect tests proved to be equal in sensitivity to the first-generation anti-HCV tests. The positive predictive power of these indirect tests in the 1980s was sufficient to affect HCV incidence in studies during that period. Improved anti-HCV assays, however, replaced the need for indirect tests. The sensitivity of indirect tests for NBNC hepatitis contributed little.

Alanine Transaminase↗
PubMed1995

Donor screening for antibody to hepatitis B core antigen and hepatitis B virus infection in transfusion recipients.

BACKGROUND: Testing for antibody to hepatitis B core antigen (anti-HBc) as a surrogate for hepatitis C viremia is no longer needed for blood donor screening. Currently, the important question is how much its use supplements hepatitis B surface antigen (HBsAg) donor screening in preventing transfusion-transmitted hepatitis B virus (HBV) infection. STUDY DESIGN AND METHODS: In a study conducted in the 1970s, 64 blood donors were associated with 15 cases of HBV (1.0%) in 1533 transfusion recipients. Sera from 61 donors at donation and 29 follow-up visits were available for present-day assays for HBsAg, HBV DNA, anti-HBc, and antibody to HBsAg (anti-HBs). RESULTS: HBsAg was found in four previously negative blood donors; HBV DNA was limited to three of these four. Anti-HBc was detected in six HBsAg-negative donors. Two other donors were negative in all assays at donation, but positive for anti-HBc and anti-HBs 2 to 4 months later. The remaining donors were negative for all HBV markers, which left five recipient cases unexplained. No HBV transmission was observed when anti-HBs sample-to-negative control values were > or = 10. CONCLUSION: Some 33 to 50 percent of cases of hepatitis B that could be transmitted by transfusion of blood from HBsAg-negative donors are prevented by anti-HBc screening. Anti-HBc-positive donors unequivocally positive for anti-HBs should be considered noninfectious for HBV and should be allowed to donate. Anti-HBc screening of paid plasmapheresis donors, supplemented by anti-HBs testing, would reduce the amount of HBV to be processed by virus inactivation and increase the content of anti-HBs in plasma pools.

Blood Donors↗
PubMed1993

Effect of concurrent acute infection with hepatitis C virus on acute hepatitis B virus infection.

OBJECTIVE: To investigate the possible interference with acute hepatitis B virus infection by co-infection with hepatitis C virus. DESIGN: Analysis of stored sera collected for transfusion transmitted viruses study in 1970s. SETTING: Four major medical centres in the United States. PATIENTS: 12 recipients of blood infected with hepatitis B virus. MAIN OUTCOME MEASURES: In 1970s, presence of antibodies in hepatitis B virus and raised serum alanine aminotransferase concentration; detection of antibodies to hepatitis C virus with new enzyme linked immunoassays. RESULTS: Five of the 12 patients were coinfected with hepatitis C virus. Hepatitis B surface antigen was first detected at day 59 in patients infected with hepatitis B virus alone and at day 97 in those coinfected with hepatitis C virus (p = 0.01); median durations of antigenaemia were 83 and 21 days respectively (p = 0.05), and the antigen concentration was lower in the coinfected patients. Alanine aminotransferase patterns were uniphasic when hepatitis B virus infection occurred alone (range 479-2465 IU/l) and biphasic in patients with combined acute infection (no value > 380 IU/l; p = 0.0025). Four coinfected recipients developed chronic hepatitis C virus infection. The fifth patient was followed for only four months. CONCLUSIONS: Acute coinfection with hepatitis C virus and hepatitis B virus inhibits hepatitis B virus infection in humans, and onset of hepatitis B may reduce the severity of hepatitis C virus infection but not frequency of chronicity. Alanine aminotransferase concentration showed a biphasic pattern in dual infection.

Acute Disease↗
PubMed1991

Hepatitis C virus infection in post-transfusion hepatitis. An analysis with first- and second-generation assays.

BACKGROUND: The causes of post-transfusion non-A, non-B hepatitis are still not fully defined, nor is it clear how accurate the tests are that are used to screen blood donors for hepatitis C virus (HCV) and to diagnose post-transfusion hepatitis caused by infected blood. METHODS: We used two first-generation enzyme-linked immunoassays (EIAs) and one second-generation immunoassay to test for anti-HCV antibodies in serum samples collected between 1976 and 1979 in the Transfusion-Transmitted Viruses Study (from 1247 patients who underwent transfusion and 1235 matched control subjects who did not receive transfusions). We tested serum collected before and after infection from the patients in whom non-A, non-B hepatitis developed, serum from their blood donors, and serum from 41 of the control subjects who had hepatitis unrelated to transfusion. RESULTS: Of the 115 patients in whom post-transfusion non-A, non-B hepatitis developed, the initial serum samples of 111 were anti-HCV-negative; after hepatitis developed in these 111 patients, the first-generation EIAs detected anti-HCV in 51 (46 percent), and the second-generation assay detected anti-HCV in an additional 16 (14 percent), for a total of 60 percent. Of 40 controls, 37 were anti-HCV-negative initially, and none seroconverted after hepatitis developed. If the 3 percent rate of non-A, non-B, non-C hepatitis among the controls (37 of 1235) was applied to the 1247 transfusion recipients, only 74 of the 111 cases of hepatitis were attributable to the transfusion. Thus, 91 percent (67 of 74) of the cases of post-transfusion hepatitis were caused by HCV. Of the 99 donors, 60 were HCV-positive (9 on second-generation tests only) and 39 were not. CONCLUSIONS: Nearly all cases of non-A, non-B post-transfusion hepatitis are caused by HCV. Screening with a second-generation assay improves the rate of detection of HCV infection in patients with post-transfusion hepatitis and in blood donors. The use of this test showed a 3.6 percent risk of non-A, non-B, non-C hepatitis, which was not significantly different from the rate in the controls (3.0 percent).

Blood Donors↗
PubMed1991

Evaluation of a chimpanzee colony for antibodies to hepatitis C virus.

The chimpanzee is the only species other than man that is generally susceptible to infection by hepatitis C virus (HCV). Aspects of future studies on vaccines and therapeutics for HCV may continue to depend on the chimpanzee. In an attempt to determine the HCV status of the animals in a chimpanzee colony, the recently developed enzyme immunoassay (EIA) for antibodies to HCV was used. The results of the assay indicated that only 31.3% of the animals that had previously been inoculated with a non-A, non-B hepatitis agent were currently positive in the assay. A retrospective analysis suggested that an additional 20% of the chimpanzees had been positive at some time following infection. Seroconversion to an anti-HCV antibody response using this assay did not appear to correlate with the severity of the initial disease or the development of chronic liver damage. Examination of the EIA-positive samples using the second generation recombinant immunoblot assay (RIBA) containing four HCV antigens suggested that chimpanzees responded differentially to these antigens. Examination of serum samples from 139 uninoculated animals by EIA revealed seven positive samples and ten samples with borderline values. The nature of the reactivities in most of the positive samples could not be resolved, but analysis by RIBA indicated that at least one animal in the breeder colony had been exposed to HCV. Due to the low seroconversion rate and the uncertainties surrounding many of the positive reactions, this assay cannot be used to determine the initial source or extent of spread of HCV infections in the uninoculated animals.

Animals↗
PubMed1990

Non-A, non-B hepatitis and antibody to hepatitis C virus.

Stored serum samples from the Transfusion-transmitted Viruses Study in the 1970s were tested for the presence of antibody to hepatitis C virus (anti-HCV). Single specimens from five control subjects who did not receive transfusions tested negative for anti-HCV. Of four control subjects who did not receive transfusions and who developed non-A, non-B (NANB) hepatitis after hospitalization, three remained anti-HCV negative; the fourth person with postoperative NANB hepatitis tested anti-HCV positive before the operation. Five transfusion recipients with posttransfusion hepatitis B virus infection remained seronegative; a sixth with NANB hepatitis as well as hepatitis B virus infection had seroconversion for anti-HCV. Five of nine transfusion recipients with NANB hepatitis had anti-HCV seroconversion. These results show that present anti-HCV testing demonstrates an etiologic basis for approximately half of the cases of transfusion-associated NANB hepatitis, particularly those that develop chronicity. Although cases of NANB hepatitis without seroconversion may be explained otherwise, they may be caused by another, presently unidentified, virus.

Blood Transfusion↗
PubMed1989

Prevalence of antibodies to human immunodeficiency virus type 1 among blood donors prior to screening. The Transfusion Safety Study/NHLBI Donor Repository.

The Transfusion Safety Study (TSS) and the National Heart, Lung, and Blood Institute (NHLBI) established a repository of approximately 200,000 sera from blood donors in late 1984 and early 1985. Collections were made in the four metropolitan areas with the highest prevalence of AIDS. Retrospective testing showed an overall anti-HIV-1 prevalence of 16 cases per 10,000 donations. In this study, the predictive value of a negative initial enzyme-linked immunoassay was estimated from both quality control specimens and the rescreening of 13,461 sera to be greater than 99.99 percent with respect to technical error. Among anti-HIV-1-positive persons, there was a 1.3- to 1.5-fold excess of first-time donors. The anti-HIV-1 prevalence among donors showed that infection was more common among young men than suggested by national reporting of AIDS cases. Anti-HIV-1 prevalence varied among the four metropolitan areas less than did reported AIDS cases, but, by 1987, the differences in the latter had decreased. Anti-HIV-1 prevalence in collection areas outside of the four major cities differed much more widely than that among the cities themselves. The TSS/NHLBI Donor Repository will remain available for the indefinite future for further evaluation of screening procedures for HIV-1 and other viruses for which transfusion is found to be an important route of transmission.

Acquired Immunodeficiency Syndrome↗
PubMed1976

The effects of measles virus and various strains of SSPE virus on organotypic cultures of nervous tissue.

The neurotropic effects, virologic behaviors and morphologic appearances of 4 strains of subacute sclerosing panencephalitis (SSPE) virus have been examined in organotypic cultures of hamster cerebellar tissue and have been compared with the Edmonston strain of measles virus in the same system. While measles virus caused extensive damage to nervous tissue, the SSPE strains, in general, exerted a less deleterious effect. All of the SSPE viruses replicated in this tissue. The SSPE strains showed morphologic variation ranging from normal measles-type virions to apparently nucleocapsid deficient forms. It is speculated that some of these differences between measles and SSPE virus may account for the differences in the in vivo conditions with which they are associated.

Animals↗
PubMed1975

Immunoperoxidase labeling of subacute sclerosing panencephalitis virus in hamster acute encephalitis.

A hamster neuroadapted strain of subacute sclerosing panencephalitis (SSPE) virus induces in the newborn animal an acute encephalitis with ultrastructural features similar to those observed earlier in measles encephalitis and characteristic of a productive viral infection. The direct immunoperoxidase technique, using labeled SSPE gamma-globulin, was applied to formaldehyde-fixed thick sections. These were either chopped after perfusion of the animal or cryocut after quick freezing of the tissue and then fixed. The latter procedure showed good correlation with light microscopic immunoperoxidase or fluorescent antibody staining on paired thin cryostat sections, whereas the former procedure resulted in easier handling of the sections and better ultrastructural preservation, especially when the lysine-periodate-formaldehyde fixative was used. Under electron microscopy the plasma membrane of the nerve cells was often labeled on its inner side in areas where nucleocapsids accumulate to form buds. The membrane antigen appeared to be more focal than in productive SSPE infection in vitro. Within the cytoplasm, most of the tubular inclusions were stained with the label located on the external granular coat of the nucleocapsid. Nonstructural antigen was also detected in the rough endoplasmic reticulum membrane (often on the side of a tubular inclusion), in the cytoplasmic matrix, and sometimes in the nucleus and on the nuclear membrane of giant cells. It thus seems that SSPE gamma-globulin reacts with viral proteins close to the site of synthesis. Because of the high specificity and reproducibility of this method for the detection of intracellular viral antigens, its use is recommended for further studies of conventional and nonconventional viral central nervous system diseases in which an immune response is present.

Acute Disease↗