Recombinant immunoblot assay reaction patterns and hepatitis C virus RNA in blood donors and non-A, non-B hepatitis patients

Antigenicity of a recombinant NS3 protein representative of ATPase/helicase domain from hepatitis C virus

It has been shown that the Hepatitis C virus nonstructural NS3 protein possesses at least two enzymatic domains: a serine-protease domain and an adenosine triphosphatase (ATPase)/helicase domain. In this report, a truncated fragment of NS3 (26 kDa), representing main epitopes from the (ATPase)/helicase domain, has been expressed in Escherichia coli. The recombinant protein was purified by Ion Metal Affinity Chromatography (IMAC) with more than 90% purity. The recognition of B-cell linear epitopes in the NS3 protein was evaluated by immunoblot. The recombinant NS3 protein was reduced and carboxymethylated, and the recognition of either conformational and/or linear B-cell determinants was evaluated by ELISA. The inclusion of the recombinant NS3 protein in a third-generation diagnostic system UltraMicroELISA (UMELISA) allowed an increase in the sensitivity, due to the detection of a new variety of false-negative sera in blood donor test samples.

Relevance of reactivity in commercially available hepatitis C virus antibody assays

Sera from 2,148 patients were tested with a third-generation microparticle enzyme immunoassay (MEIA), a confirmatory assay, and a reverse transcription-PCR. Overall, 85.6% of reactivities were confirmed, 13.2% were shown to be unspecifically reactive, and 1.2% were indeterminate. The rate of confirmed MEIA reactivities clearly depended on the strength of the reactivity.

Development of low cost peptide-based anti-hepatitis C virus screening and confirmatory assays: comparison with commercially available tests

Screening and confirmatory low cost reagent tests have been developed for detection of anti-hepatitis C virus (HCV). Assays are based on the use of specific synthetic peptides from several structural and non-structural viral proteins. The efficacy of the screening anti-HCV EIA-Spep assay was compared with both Abbott EIA 2.0 (Abbott Laboratories, North Chicago, IL) and Ortho EIA 2.0 (Ortho Diagnostic Systems, Raritan, NJ) anti-HCV detection kits and the confirmatory EIA-Cpep assay was compared with the Abbott Matrix anti-HCV confirmation test. In the EIA-Spep, a pool of 3 peptides was added to each well of a microtiter plate. In EIA-Cpep, each well was separately coated with 1 of 4 peptides and 1 recombinant protein. A total of 867 blood donor samples from Costa Rica tested simultaneously with the 3 screening assays yielded the same specificity and negative predictive values of > or =99.9% and 100%, respectively. A comparative study on voluntary blood donor samples from Honduras, Nicaragua, and El Salvador using the 2 anti-HCV confirmatory assays revealed different patterns that are 46% positive, 24% indeterminate, and 30% negative with the EIA-Cpep assay vs. 31% positive, 48% indeterminate, and 21% negative with the Matrix assay. A study of 71 patient samples from Costa Rica showed a higher correlation between initially reactive samples when analyzed by the Abbott and Ortho kits, than when the assay results were compared between the Abbott and EIA-Spep kits; the latter detected 7 and 15 non-reactive samples, respectively. These results could reflect the use of a similar antigen source for the 2 commercial assays. The presence of HCV RNA in a group of 29 samples analyzed was related to the simultaneous reactivity in all 3 screening assays. None of the discordant samples had detectable levels of HCV RNA. Economic difficulties for health care services in the developing countries of Central America have prevented implementation of routine anti-HCV blood donor screening tests. This is likely to be the primary reason for uncontrolled dissemination of HCV, and the lack of identification of potential high risk groups. Alternative low cost reagents developed locally as described in this article could be a useful tool in the control of HCV spread throughout the developing world.

High rate of chronicity in HCV infection determined by antibody confirmatory assay and PCR in 4110 patients during long-term follow-up

BACKGROUND

It is still unclear how many patients with hepatitis C virus (HCV) antibodies have viremia and hence are infectious.

OBJECTIVES

To determine the chronicity of HCV infection by correlation of HCV antibodies with presence of viremia in long-term follow-up.

STUDY DESIGN

In a longitudinal study sera of 4110 patients were analyzed with second generation HCV-enzyme immunoassay (EIA) and polymerase chain reaction (PCR). Only those patients were included in this study in whom sequential serum samples over a period of 2 years were available. To avoid preanalytical and analytical failures, we used a transport solution to prevent RNA degradation and a four-antigen recombinant immunoblot assay, established in our laboratory, for confirmation of antibody reactivity.

RESULTS

Of 2815 patients with confirmed HCV antibodies 2784 (98.9%) were also positive in HCV-PCR assay. False reactive EIA results were detected in 177 (13.7%) individuals as shown by confirmatory assay and PCR. Only one patient (0.04%) spontaneously lost detectable HCV viremia and subsequently HCV-specific antibodies.

CONCLUSIONS

Our study clearly demonstrates that presence of confirmed HCV-specific antibodies correlates significantly (98.9%; P < 0.001) with HCV viremia, and that spontaneous loss of viremia is a very rare event in HCV infection. We also found that elimination of HCV infection is not sufficiently predicted by the loss of detectable viremia in PCR, but can be concluded from the disappearance of virus-specific antibodies.

Definition of false-positive reactions in screening for hepatitis C virus antibodies

The rate of false-positive hepatitis C virus enzyme immunoassay results was determined to be at least 10% among 1,814 reactive serum samples based on (i) negative results in an independent confirmation assay, (ii) negative PCR results, and (iii) no patients developing clinical or biochemical signs of hepatitis during a 1-year follow-up.

Use and interpretation of HCV diagnostic tests in the clinical setting

The rapidly emerging and sometimes complicated field of HCV diagnostics can be simplified by classification of tests into two general categories: serologic tests which screen for anti-HCV antibodies, and molecular tests which are used to assess HCV viremia and characterize viral infection at the genetic level. Antibody tests include the highly sensitive screening enzyme immunoassays (current versions: EIA-2 and EIA-3), and supplemental tests such as the recombinant immunoblot assay (RIBA-2). Molecular assays such as HCV RNA polymerase chain reaction (PCR) may play an important role in confirming HCV infection in several clinical situations, such as immunosuppressed patients with chronic hepatitis C, patients with acute hepatitis who might be in the diagnostic "window" period prior to seroconversion, and seropositive patients with normal ALT values. Quantitative HCV-RNA tests, such as quantitative PCR (Q-PCR) and branched DNA (bDNA), provide valuable tools for assessing the level of HCV viremia prior to and during therapy. Genotype tests allow classification of HCV infection in one of six distinct HCV genotypes, although the clinical relevance of HCV genotype tests has not been established.

High throughput PCR detection of HCV based on semiautomated multisample RNA capture

An amplification procedure based on a semiautomated 60-sample RNA capture, including combined reverse transcription/polymerase chain reaction (RT-PCR) and nested PCR/Taqman amplicon detection. is described. It can be completed within a working day and is suitable for the development of a fully automated system. HCV RNA-specific capture is independent of the sequence variations as it targets the poly(U) tract commonly present at the 3'-end of the HCV genome (U-capture). The type specificity of the assay determined in a panel of 56 confirmed HCV antibody-positive samples (genotypes 1-6) was slightly better when compared to a commercial assay. The sensitivity evaluated on serial dilutions of representative samples was equal for genotypes 1, 2, 5, 6, or increased for genotypes 3 and 4 with the U-capture assay.

Look-back of anti-HCV ELISA-positive, HCV-RNA PCR-negative donors and recipients of their blood products

BACKGROUND AND OBJECTIVES

To establish the infectivity of anti-HCV ELISA-positive, but cDNA-PCR-negative blood components transfused before the introduction of routine anti-HCV blood donor screening, we enrolled recipients of such blood products in a look-back programme.

MATERIALS AND METHODS

The blood components were donated by (A) RIBA-2-indeterminate and cDNA-PCR-negative donors, and (B) RIBA-2 and cDNA-PCR-negative donors. The look-back comprised 214 blood products from group A donors and 278 from group B.

RESULTS

Of 211 recipients of group A components, 66 (31.3%) were available for testing. All other recipients could not be traced, had died, or refused collaboration. Of these 66, 3 patients had independent risk factors for HCV infection and were excluded. All remaining 63 recipients were anti-HCV ELISA-negative. Of 274 recipients of group B components, 84 (30.7%) were available for testing. All others could not be traced, had died, or refused collaboration. Of these 84, six patients had an independent risk factor for HCV infection and were excluded. All remaining 78 recipients were anti-HCV ELISA-negative. None of the recipients of blood products from previous donations of anti-HCV ELISA-positive, cDNA-PCR-negative, and RIBA-2-indeterminate or negative donors were HCV-infected.

CONCLUSIONS

Donors and patients with such reactivities in anti-HCV ELISA, RIBA-2, and cDNA-PCR can be assured that they are not infected with HCV. The donors involved can re-enter the donor pool, provided that future donations are anti-HCV ELISA-negative.

[Screening and confirmation of anti-HCV antibodies in Tunisian blood donors]

Antibodies to Hepatitis C virus (HCV) were tested in 43000 Tunisian blood donors by using enzyme immuno-assay. Our results show that 0.7% (304/43000) were anti-HVC positive. Of these 304.78 were confirmed anti-HCV positive (0.18%) by immuno-blot, and 99 displayed an indeterminate profile. Different immune responses were observed: In donors with positive serologic pattern (78/304), 25.6% response towards whole antigens (C + NS3 + NS4 + NS5) was frequently observed (44/78) 56.4%. Reactivity to 2 antigens was observed in 28.2% (22/78) and with 3 antigens in only 15.4% (12/78), with systematic reactivity to core. In donors with indeterminate serologic pattern (99/304) 32.5%, reactivity to non-structural antigen NS5 was the most frequently observed (54/99) 54.5%, reactivity to non-structural NS3 antigen was noted in 27.3% (27/99) and to core antigen in 18.2% (18/99). No donors with isolated reactivity to NS4 were observed in our series.

Analytical and laboratory evaluation of a new fully-automated third generation enzyme immunoassay for the detection of antibodies to the hepatitis C virus

An analytical and laboratory evaluation of a newly-developed fully-automated third generation ELISA for the detection of anti-HCV (Cobas Core Anti-HCV EIA, Roche) was undertaken. Coefficients of variation (CVs) calculated on positive control and serum samples ranged from 5.9 to 9.8% in the intra-assay precision test and from 3.9 to 11.3% in the inter-assay evaluation. With regard to the study of clinical laboratory performance, five groups of sera pre-screened with two third generation ELISA (Ortho HCV 3.0 ELISA; Innotest HCV Ab III) were assayed: anti-HCV negative samples (n = 932); anti-HCV positive samples (n = 449); difficult sera of different origin (n = 113); sera with discrepant results in the two ELISAs (n = 50); sera with an indeterminate result in one or more confirmatory test (n = 34). The overall concordance between the Roche anti-HCV EIA and the two reference assays was 97.5 and 97.8% for the Ortho and for the Innogenetics assays, respectively. Although it is not possible to provide absolute figures for clinical sensitivity and specificity, the results of the study on discrepant samples show that the Cobas Core Anti-HCV gives a number of negative results with positive or indeterminate confirmatory anti-HCV tests, which is intermediate between the Ortho and the Innogenetics assay. In contrast, only 5% Cobas Core Anti-HCV reactive sera are not positive or clear-cut single band reactive by supplemental assays. The results show that the new fully-automated third generation anti-HCV test is a valid alternative to other commercially available assays for screening of antibodies to the hepatitis C virus.

Nucleotide sequences of the hepatitis C virus core region in patients without anti-core antibody

Second-generation assays for detection of hepatitis C virus (HCV) infection that include reactivity of antibodies to core, NS3, NS4 are used because of their high sensitivity. Among these antibodies, anti-core antibody seems to be the most sensitive. However, there are some patients without anti-core antibodies, although HCV RNA is detectable by reverse transcription-polymerase chain reaction and branched DNA assay. The mechanism for the absence of anti-core antibody on its own is unclear. We therefore determined the nucleotide and deduced amino acid sequences of the core region obtained from two anti-core antibody-negative patients with HCV RNA (genotype 1b) and compared them with those of four anti-core antibody-positive patients and a previously reported sequence. Amino acids spanning 1-47, which seemed to exist in major B cell epitopes, were found to be completely conserved among these patients. Furthermore, the predictive binding motif to HLA DR4 (a.a 81-90) was completely conserved in both of the anti-core antibody-negative patients. There were various mutations in the residual amino acids spanning 49-108, but specific mutations could not be found in anti-core antibody-negative patients. These data indicate that the absence of anti-core antibody in two patients is not due to the presence of some formerly unknown viral variants, but due to a possible defect in the host's immune system.

International collaborative study on the second EUROHEP HCV-RNA reference panel

Eighty-six laboratories participated in a collaborative study and tested the second EUROHEP HCV-RNA reference panel. The coded panel comprised 4 HCV-RNA positive plasma samples (one weak positive), 6 HCV-RNA negative plasma samples and two dilution series of HCV-RNA genotype 1 and 3 plasma standards. The 86 laboratories submitted 136 coded data forms for evaluation. Of these data sets 99 were tested using a PCR assay developed in-house, 28 using a commercially available HCV-PCR test (AMPLICOR, Roche Diagnostic Systems) and 9 using other amplification methods. Twenty-two data forms (16%) had faultless results, 39 (29%) missed the weak positive sample only and 75 data sets (55%) had false positive and/or false negative results. Participants using the commercial HCV-PCR test tended to reach a sufficient quality score more often than investigators using assays developed in-house (64% versus 45%, P = 0.11). The UNG system in the commercial HCV-PCR test did not prevent five laboratories generating false-positive results in the 6 HCV-RNA negative samples. Among the laboratories with satisfactory results, up to 10000-fold differences in sensitivity were observed in the dilution series. The 50% and 90% laboratories detection endpoints in the dilution series of the HCV genotype 1 plasma standard were approximately 600 genome equivalents per ml (geq/ml) and 7750 geq/ml according to a standard applied in a signal amplification assay (bDNA, Chiron). Our results suggest that the detection efficiency for genotype 3 by commercial HCV-RNA assays is lower than by the in-house assays. Internationally characterized HCV-RNA plasma standards should be made available for validation and standardization of HCV-RNA assays for HCV diagnosis and virological safety testing of blood products.

HCV-Infection in blood donors: association between anti-HCV core IgM antibodies and serum HCV RNA

Among 47 blood donors tested positive with HCV EIA 2.0 Abbott, 27 (57.4%) also reacted with four ¿third-generation' EIAs. The presence of anti-HCV antibodies was confirmed with 3 different immunoblot assays in 16 of 27 sera (34.0%) while 10 samples (21.3%) had indeterminate profile with antibodies usually directed against structural core antigen. Anti-HCV core IgM response was found in 12 of 47 sera (25.5%) and HCV viremia detected by the polymerase chain reaction (PCR) procedure was observed in 15 samples (31.9%). A comparative study of the different markers confirmed a good correlation between a strong antibody response in EIAs and immunoblot assays and the presence of HCV RNA in the serum; only 2 immunoblot indeterminate samples were PCR positive. An association was observed between IgM antibodies against "core' epitopes and HCV RNA carriage: all IgM-positive sera were found positive by PCR. However, the direct detection of viral genome remains the best method for identifying HCV carriers in the blood donor population.

Significance of indeterminate third-generation hepatitis C virus recombinant immunoblot assay

Indeterminate hepatitis C virus (HCV) third-generation recombinant immunoblot assay (RIBA3.0; Ortho Diagnostic Systems) patterns were arbitrarily defined by the manufacturer as the detection of only one antibody out of the four that were sought, namely, c100 (NS4 encoded), c22 (core encoded), c33c (NS3 encoded), and NS5 (NS5 encoded). The aims of the present study were (i) to determine the prevalence of indeterminate RIBA3.0 patterns in patients consecutively tested for anti-HCV antibodies in a university hospital; (ii) to evaluate the significance of these patterns in terms of viral replication, liver disease, and risk factors for HCV; and (iii) to get an insight into the mechanism underlying this peculiar immune response. Among 3,074 serum samples consecutively tested for anti-HCV antibodies, 588 were found to be positive by screening assays. Fifty-nine of them (10%) were RIBA3.0 indeterminate and were compared with 59 RIBA3.0-positive ones. Thirty-one RIBA3.0-indeterminate and 53 RIBA3.0-positive serum samples were HCV RNA positive by PCR (53 versus 90%; P < 10(-6). RIBA3.0-indeterminate and RIBA-3.0-positive patients with positive PCR results were not significantly different for the prevalence of risk factors for HCV infection and elevated serum alanine aminotransferase activities. Immunosuppression, attributable to coexisting human immunodeficiency virus infection, organ transplantation, or the administration of immunosuppressive drugs, was significantly more frequent in PCR-positive, RIBA3.0-indeterminate patients than in PCR-negative, RIBA3.0 indeterminate patients (P < 0.001) and PCR-positive patients with a positive RIBA3.0 result (P < 0.01). The distribution of HCV genotypes did not differ significantly between HCV RNA-positive patients with indeterminate or positive RIBA3.0 results. In conclusion, the prevalence of indeterminate RIBA3.0 patterns in virology laboratories is about 10%; in about half of these patients HCV replication is detected by PCR; the main factor responsible for indeterminate RIBA3.0 patterns could be immunosuppression, whereas HCV genotypes do not seem to play major role.

Evaluation of a new automated third-generation anti-HCV enzyme immunoassay

The new Cobas Core Anti-HCV EIA was evaluated in two centers for its ability to detect antibodies directed to hepatitis C virus in human serum. This assay, which can be run fully automated on a random access analyzer, was compared with three other commercially available screening tests: the Ortho HCV 3.0 ELISA, the Murex anti-HCV, and the Abbott HCV EIA second generation. Positive or discrepant results were further investigated using the Wellcozyme HCV Western Blot or the Abbott Matrix HCV assays. The results obtained from analyzing 5045 serum samples showed a high correlation between the Cobas Core Anti-HCV EIA and the other screening assays, ranging from 98.9% to 99.9%. Diagnostic specificities and sensitivities ranged from 99.7% to 100% and from 98.8% to 100%, respectively. In this study, the Cobas Core Anti-HCV EIA proved to be a very convenient test, able to perform at the highest levels of sensitivity and specificity.

Clinical evaluation of a single reaction, diagnostic polymerase chain reaction assay for the detection of hepatitis C virus RNA

BACKGROUND/AIMS

In the past few years the detection of HCV-RNA by polymerase chain reaction has become a well-established diagnostic tool for patients with chronic hepatitis C. However, the lack of reproducible results between laboratories and the relatively high proportion of false-positive results, has indicated the need for a standardized and reliable polymerase chain reaction assay. In the present study we have analyzed the performance of a commercial, HCV-RNA polymerase chain reaction assay based on a single, combined reverse transcription and amplification reaction and on the use of Uracil-N-glycosilase to prevent carry-over contamination (Amplicor HCV, Roche Molecular Systems).

METHODS

In this assay the amplification products are detected in microwell plates using biotinylated primer and the HRP avidin colorimetric system. Serum samples collected from 446 patients, including 181 with chronic active hepatitis C, 50 with autoimmune chronic hepatitis, 117 in hemodialysis, 30 asymptomatic carriers of anti-HCV and 68 with indeterminate serology (RIBA indeterminate results), as well as from 121 controls were tested with the commercial, single-step assay and with nested polymerase chain reaction. Both techniques use primers located within the 5' non-coding region of the HCV genome.

RESULTS

In all cases a good concordance was observed between the commercial, single-step assay and nested polymerase chain reaction which, for patients with chronic active hepatitis, showed a sensitivity and specificity of 100% and 99.3% for the former and of 98.8% and 100% for the latter, when compared to clinical diagnosis taken as the gold standard. Most of the 11 discordant samples were seen in the group of RIBA-indeterminate cases and in patients with chronic active hepatitis C. Further analysis of these cases, based on repeat testing and clinical data showed that 64% and 36% of the discrepancies were due, respectively, to nested polymerase chain reaction and Amplicor inconsistent reactions. In hemodialyzed patients, patients with autoimmune hepatitis and asymptomatic carriers of anti-HCV, both assays produced results which were consistent with the clinical diagnosis. In the former group, polymerase chain reaction was able to identify the presence of active viral replication in some antibody negative samples.

CONCLUSIONS

Taken together, these results indicate that the commercial, single-step polymerase chain reaction assay has the same clinical sensitivity and specificity as nested polymerase chain reaction and that, because of its simplified procedures and fast turn-around time, it may be a valuable test for routine diagnostic applications.

Rapid HCV RNA detection by PCR followed by a new non-radioactive liquid hybridisation assay and comparison with RIBA

A one-stage polymerase chain reaction (PCR) followed by an automated liquid hybridisation assay was used to examine anti-HCV-positive patients. The presence of HCV-RNA in 251 randomly selected enzyme immunoassay (EIA) positive clinical specimens was compared to their RIBA pattern. An association of a RIBA pattern with presence or absence of HCV-RNA was not detected. One hundred of these samples were also evaluated after dividing them into normal and elevated serum alanin aminotransferase (ALT) levels. PCR results were obtained on the basis of amplification products from two different gene regions (5'-NC region and NS 3). To prove the specificity of the PCR products, a commercially available digoxigenin-based liquid hybridisation assay was evaluated. The sensitivity was comparable to the results obtained after nested PCR. Based on the results of the study, the two-stage PCR can be changed in favour of the easier one-step PCR which offers the advantage of fewer contamination problems.

Antibody to hepatitis C virus second envelope (HCV-E2) glycoprotein: a new marker of HCV infection closely associated with viremia

The second envelope protein (E2) of the hepatitis C virus (HCV) was cloned and expressed in Chinese hamster ovary (CHO) cells. This E2 glycoprotein was purified using ion exchange and lectin chromatography and used to construct an enzyme immunoassay for HCV E2 antibodies. The assay was shown to have good specificity, and detection of E2 antibodies was positively correlated (97.3%) to the presence of HCV RNA in serum and plasma. A high concordance between HCV 2.0 and E2 EIA reactivities was also observed. E2 antibody was the first serological marker to appear in 3/5 HCV seroconversion panels. This work demonstrated that 42.4% of core and 15.4% of NS3 indeterminate specimens also contained antibodies to E2, suggesting that HCV infection had occurred in these individuals. The E2 antibody assay was used to evaluate HCV 2.0 EIA-positive, HCV 3.0 EIA-negative plasma donors with indeterminate reactivity on RIBA HCV 2.0 or MATRIX HCV 1.0. Several HCV 3.0-negative specimens were shown to contain E2 antibodies in addition to an original indeterminate serological marker, primarily core. It is concluded that anti-E2 is a useful marker for determining HCV infection, and that the presence of antibodies to two nonoverlapping viral gene products suggests true HCV exposure. New HCV 3.0 blood screening tests should detect HCV 2.0-positive donors who present with an indeterminate pattern by RIBA or MATRIX and who also carry E2 antibodies.

Hepatitis C infection and viremia in Dutch hemophilia patients

Serum samples from 316 patients visiting the Dutch National Hemophilia Center were collected from 1979 to 1993 and stored at -30 degrees C. Patients were placed into three different groups: 1) patients ever treated with large pool non-hepatitis C virus (HCV)-safe concentrate (n = 179); 2) patients treated with cryoprecipitate (n = 125); and 3) patients treated exclusively with HCV-save concentrate (n = 12). In order to examine the prevalence of HCV infection in the different treatment groups serum samples were tested retrospectively for anti-HCV antibody using second generation enzyme-linked immunosorbent assay (ELISA) and recombinant immunoblot assay (RIBA-2). Significant differences in the prevalence of HCV infection were found between these 3 groups (group 1: 99%, group 2: 66%, group 3: 0%). The safety of currently administered clotting products is demonstrated in 57 patients who remained without HCV markers between 1989 and 1993. To examine the natural course of HCV infection fresh-frozen plasma samples were obtained recently from a subgroup of 277 hemophilia patients for HCV-RNA detection by a well-validated cDNA-PCR assay. In contrast to other reports, no evidence was found for seronegative HCV carriers. None of 52 patients without anti-HCV had detectable HCV-RNA. Of 225 patients with anti-HCV, 182 (81%) were HCV-RNA positive. None of 39 anti-HCV positive patients with a negative HCV-RNA reaction had serum alanine aminotransferase (ALT) levels above 50 U/l, whereas 44% of HCV-RNA positive patients had persistently elevated ATL levels above 50 U/l.(ABSTRACT TRUNCATED AT 250 WORDS)

Long-term serologic follow-up of hepatitis C virus-seropositive homosexual men

Hepatitis C virus (HCV) infection may go undiagnosed and continue to present a source of community-acquired or transfusion-associated infection because of shortcomings in sensitivity, specificity, and reproducibility of serologic tests. This project was designed to longitudinally study persons who were HCV seropositive or were at risk for seroconversion to characterize the course of infection. Sequential serum samples obtained semiannually from 617 homosexual male volunteers were available for study from the Pittsburgh site of the Multicenter AIDS Cohort Study. Testing by anti-HCV enzyme immunoassay (EIA) was performed on baseline (1984 to 1985) and most-recent (censor date, August 1992) samples. Selected samples were also assayed for alanine aminotransferase and by recombinant immunoblot (RIBA II) and nested PCR. A total of 17 of 617 (2.8%) men were HCV seropositive at entry. Of the 600 seronegative men, 9 converted to HCV seropositive during the study interval. Parenteral sources of exposure could be identified in 6 of these 26 HCV-seropositive men. Four men were HCV seropositive at baseline and seronegative at their most recent visit. Of the 26 HCV-seropositive men, 12 were also seropositive for human immunodeficiency virus. EIA analysis of 298 longitudinal samples from the 26 men revealed three patterns of HCV seropositivity: persistent, intermittent, and rare. Nine men (35%) showed intermittent or rare seropositivity with periods of over 1 year between some seropositive samples. PCR was positive in 76% of the HCV EIA-positive and 84% of the RIBA-positive samples. Thus, a low but significant number of homosexual men were HCV seropositive with variable positivity over several years of follow-up. A portion of these men become HCV seronegative. Individuals who exhibit intermittent or rare seropositivity are a challenge to diagnosis.

Study on reliability of commercially available hepatitis C virus antibody tests

The serodiagnosis of hepatitis C virus (HCV) infection was analyzed by a recombinant immunoblot assay (RIBA) with recombinant proteins encoded by the viral RNA isolated from our patients in Hamburg, Germany. The HCV RNA was amplified by PCR, and proteins encoded by the viral core and the NS3, NS4, and NS5 regions were expressed subsequently in Escherichia coli. The results obtained with our UKE RIBA were compared with the results of the Abbott HCV second-generation enzyme immunoassay (EIA). Serum samples from 270 patients, which were sent to us on the suspicion of HCV hepatitis and which were negative for hepatitis A virus and hepatitis B virus antibodies, were examined. In 227 cases (84.1%), there were identical positive (204 cases, 75.6%) or negative (23 cases, 8.5%) results in both tests. In 32 cases (11.9%), the reactive Abbott second-generation HCV EIA results could not be confirmed by the UKE RIBA and the HCV PCR. In follow-up studies conducted over 1 year, these results did not change. In three cases (1.1%), the UKE RIBA presented a positive result while the Abbott second-generation HCV EIA was negative. All three cases were positive in the HCV PCR and showed seroconversion in an HCV EIA 4 to 6 weeks later. In addition, 33 patient serum samples were examined by UKE RIBA in parallel with the Ortho RIBA 2.0. In three cases (9.1%), a positive Ortho RIBA 2.0 result could not be confirmed by the UKE RIBA and the HCV PCR. All three patients were free of complaints. The UKE RIBA showed also a smaller number of indeterminate results (3.0%) than the Ortho RIBA 2.0 (24.2%). This comparison study demonstrates that the commercially available HCV antibody tests should be further improved.

Transmission of the hepatitis-C virus by tissue transplantation

The hepatitis-C virus has been the most prevalent cause of chronic hepatitis in both blood and organ recipients. The introduction of a second-generation immunoassay for antibodies to the hepatitis-C virus (HCV 2.0) provided the opportunity to determine if the hepatitis-C virus can be transmitted through tissue transplantation. Banked sera from tissue donors that had previously been found to be non-reactive to the first-generation hepatitis-C virus antibody assay (HCV 1.0) and non-reactive for antibodies to hepatitis-B core antigen were retested with HCV 2.0. The sera from two donors were reactive; the transplant records of recipients of tissues from these donors were reviewed, and the surgeons or hospitals were contacted. The tissue recipients were tested with HCV 2.0, and positive sera were tested for hepatitis-C virus RNA by polymerase chain reaction. Viral nucleic acids isolated from viremic donors and recipients were analyzed for identity by sequencing of the hepatitis-C virus envelope gene (E2) hypervariable region. There were twenty-one grafts, which had been treated with gamma radiation, from one donor; thirteen had been transplanted to twelve recipients. Serum samples from six of the recipients were tested; one was reactive. This patient had other risk factors for infection with the hepatitis-C virus, and sequence analysis demonstrated non-identity between the donor and recipient hepatitis-C virus isolates. Nine of twelve grafts from a second donor had been transplanted in nine recipients. Serum samples from five patients were tested with HCV 2.0; four were reactive. In three of the four patients, the sera were determined to be positive for the hepatitis-C virus by polymerase chain reaction. E2 sequence analyses of hepatitis-C virus RNA isolates from two of these recipients demonstrated sequence identity with the donor isolate. The results of the present report demonstrate that the hepatitis-C virus can be transmitted by bone, ligament, and tendon allografts. They also support the need for testing of all tissue donors for antibodies to the hepatitis-C virus before the tissue is released for transplantation. The results also suggest that seventeen kilo-gray of gamma radiation may inactivate the hepatitis-C virus in tissue.

Existing problems in the testing for infectious diseases

Current methods for testing donated blood for presence of infectious viral agents in the USA differ from those used in other countries because of the USA Food and Drug Administration's (FDA) control which inhibits rapid introduction of testing methods or improvements. Delays in FDA approval may occur because of concerns about methodology or the state of knowledge about the disease it is intended to detect as well as due to variability between manufacturers. Despite strict FDA control, testing problems continue to occur in the USA. No approved method detects infectious agents during the "window period," and variations in detection, i.e., false positives and false negatives (even with confirmatory testing), continue to occur. The effect of physical and chemical changes (e.g., various anticoagulants) on samples has not been thoroughly evaluated. Test performance problems include lapses in sample identification, failure to use routine laboratory controls, improper calculation and reporting of results, improper acceptance of test runs and failure to properly detect and retest samples when carryover from very reactive samples occurs. For these reasons, transfusion-related disease transmission continues to occur. The current USA emphasis on good manufacturing practices should provide continuous improvements.

Transmission of hepatitis C virus by transfusion in Orebro County, Sweden, 1990-1992

A retrospective study of hepatitis C virus (HCV) transmission by transfusion was conducted in Orebro county. Out of the 7,900 active, registered blood donors, 21 repeatedly anti-HCV reactive (RIVA 2 positive or indeterminate) donors were diagnosed. Their 84 recipients from January 1990 through June 1992 were identified and 41 (49%) were alive in December 1992. A total of 13 anti-HCV reactive (RIBA 2 positive or indeterminate) were diagnosed in 39 investigated recipients. Of these 11 were previously undiagnosed, and seven were HCV RNA-positive. In the donor population 1.03% were anti-HCV-positive by ELISA, but only 0.09% were RIBA and HCV RNA-positive. In 1990, 0.06% of the blood components came from the HCV RNA-positive donors, and none during the first 6 months of 1992. In order to identify transfusion-transmitted HCV infections that took place before the introduction of tests for anti-HCV antibodies, patients with a history of transfusion and symptoms and signs of liver dysfunction or damage should be thoroughly tested.

E2 and NS5: new antigens for detection of hepatitis C virus antibodies

The value of two new hepatitis C virus (HCV) antigens for detection of HCV antibodies was studied. These two recombinant antigens were derived from the nonstructural-5 (NS5) and envelope-2 (E2) region of the HCV genome. In a panel of 33 HCV-RNA positive samples with indeterminate Riba-2 confirmatory test results, 29 samples (88%) showed additional antibody reactivity against E2 and 12 samples (36%) showed additional reactivity against NS5. Among 39 HCV-RNA negative, Riba-2 indeterminate donor samples, no additional E2 or NS5 reactivity was found in 34 samples (87%); while 5 samples (13%) showed additional reactivity against NS5 and/or E2. E2 reactivity thus resolved the majority of hitherto indeterminate samples. In serial samples from nine posttransfusion hepatitis C patients, NS5 and E2 antibodies did not appear earlier than classical HCV antibodies. However, E2 antibodies eventually appeared in all nine patients. The recombinant E2 might be a candidate antigen for future HCV antibody assays.

Hepatitis C: progress and problems

The hepatitis C virus (HCV), a single-stranded RNA virus, is the major cause of posttransfusion hepatitis. HCV isolates differ in nucleotide and amino acid sequences. Nucleotide changes are concentrated in hypervariable regions and may be related to immune selection. In most immunocompetent persons, HCV infection is diagnosed serologically, using antigens from conserved regions. Amplification of RNA may be necessary to detect infection in immunosuppressed patients. Transmission by known parenteral routes is frequent; other means of spread are less common and may represent inapparent, percutaneous dissemination. Infection can lead to classical acute hepatitis, but most infected persons have no history of acute disease. Once infected, most individuals apparently remain carriers of the virus, with varying degrees of hepatocyte damage and fibrosis ensuing. Chronic hepatitis may lead to cirrhosis and hepatocellular carcinoma. However, disease progression varies widely, from less than 2 years to cirrhosis in some patients to more than 30 years with only chronic hepatitis in others. Determinants important in deciding outcome are unknown. Alpha interferon, which results in sustained remission in selected patients, is the only available therapy. Long-term benefits from such therapy have not been demonstrated. Prevention of HCV infection by vaccination is likely to be challenging if ongoing viral mutation results in escape from neutralization and clearance.