IgM antibody to hepatitis C virus in acute and chronic hepatitis C

The variability of the serological response to SARS-corona virus-2: Potential resolution of ambiguity through determination of avidity (functional affinity)

Data on the serological response toward severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) in 16 recent reports were analyzed and a high degree of variability was shown. Immunoglobulin M (IgM) responses were either found earlier than IgG, or together with IgG, later than IgG, or were missing. Therefore, clear distinctions between early, intermediate, and past infections are obviously not possible merely on the basis of IgM and IgG determinations. A review of publications on the serology of other virus groups shows that variable IgM responses can be found as well and therefore are not unique for SARS‐CoV‐2 infections. A model to explain this variability is proposed. The inclusion of avidity determination into regular diagnostic procedures has allowed to resolve such “atypical” serological constellations. The potential use of avidity determination for the diagnosis of COVID‐19, for risk assessment, epidemiological studies, analysis of cross reactions, as well as for the control of vaccination programs is suggested and discussed.

The serological response to SARS CoV‐2 infection is highly variable.

The mere detection of specific IgM and IgG does not allow to distinguish between acute and past infection.

The variable IgM and IgG responses after SARS CoV‐2 infection are analogous to serological findings in other virus systems.

Variable IgM and IgG responses can be rationally explained by models that describe immunoglobulin production by the immune system.

Avidity determination of SARS CoV‐2 IgG is suggested for resolution of diagnostic ambiguity.

Laboratory Diagnosis and Monitoring of Viral Hepatitis

Many microbes, toxins, autoimmune diseases, and neoplastic diseases may cause liver inflammation; however, 5 viruses whose main pathogenesis is liver disease are referred to as hepatitis A, B, C, D, and E viruses. These viruses cause a significant burden of global illness. With the exception of hepatitis A virus, all may cause chronic infection potentially leading to cirrhosis and hepatocellular carcinoma. Excellent serologic and nucleic acid detection methods are available for determining the precise cause and, in some cases, the duration of infection. Diagnostics are critical for identifying individuals needing treatment and for monitoring the treatment success.

Detection of virus-specific polymeric immunoglobulin A in acute hepatitis A, C, E virus serum samples using novel chimeric secretory component

Objective

To conduct a proof-of-concept study on preferential binding of polymeric IgA (pIgA) using a novel recombinant rabbit/human chimeric secretory component (cSC) and preliminary assessment of the diagnostic potential of virus-specific pIgA in discriminating acute hepatitis A, E, and C (HAV, HEV, HCV) patients and uninfected controls using an indirect enzyme-linked immunoassay.

Results

cSC binds > 0.06 μg/ml of purified human and mouse pIgA with negligible cross-reactivity against IgM and IgA. Virus-specific pIgA was significantly higher in serum of acute HAV (n = 6) and HEV (n = 12) patients than uninfected samples (HEV: p < 0.001; HAV: p = 0.001), and had low correlation with virus-specific IgM (HEV r: − 0.25, 95% CI − 0.88 to 0.71, p = 0.636; HAV r: 0.05, 95% CI − 0.54 to 0.60, p: 0.885). Anti-HCV pIgA peaked early in HCV seroconversion panels (n = 14), and was undetectable after 4 weeks post-primary bleed, even in ongoing infections, while serum anti-HCV IgA, IgG and IgM persisted. Patients with early acute HCV infection had significantly higher levels of anti-HCV pIgA compared to those with chronic infections (p < 0.01). The use of novel cSC demonstrates the presence of virus-specific pIgA in sera of patients with acute HAV, HEV, and HCV infection, and posits its potential utility as a diagnostic biomarker that warrants further validation on larger sample populations.

Novel evolved immunoglobulin (Ig)-binding molecules enhance the detection of IgM against hepatitis C virus

Detection of specific antibodies against hepatitis C virus (HCV) is the most widely available test for viral diagnosis and monitoring of HCV infections. However, narrowing the serologic window of anti-HCV detection by enhancing anti-HCV IgM detection has remained to be a problem. Herein, we used LD5, a novel evolved immunoglobulin-binding molecule (NEIBM) with a high affinity for IgM, to develop a new anti-HCV enzyme-linked immunosorbent assay (ELISA) using horseradish peroxidase-labeled LD5 (HRP-LD5) as the conjugated enzyme complex. The HRP-LD5 assay showed detection efficacy that is comparable with two kinds of domestic diagnostic kits and the Abbott 3.0 kit when tested against the national reference panel. Moreover, the HRP-LD5 assay showed a higher detection rate (55.9%, 95% confidence intervals (95% CI) 0.489, 0.629) than that of a domestic diagnostic ELISA kit (Chang Zheng) (53.3%, 95% CI 0.463, 0.603) in 195 hemodialysis patient serum samples. Five serum samples that were positive using the HRP-LD5 assay and negative with the conventional anti-HCV diagnostic ELISA kits were all positive for HCV RNA, and 4 of them had detectable antibodies when tested with the established anti-HCV IgM assay. An IgM confirmation study revealed the IgM reaction nature of these five serum samples. These results demonstrate that HRP-LD5 improved anti-HCV detection by enhancing the detection of anti-HCV IgM, which may have potential value for the early diagnosis and screening of hepatitis C and other infectious diseases.

How to use virological tools for the optimal management of chronic hepatitis C

Approximately 180 million individuals are chronically infected with hepatitis C, which is strongly associated with the development of cirrhosis, end-stage liver disease and hepatocellular carcinoma. Several virological tools (anti-HCV antibody assays, measurement of HCV-RNA, HCV-genotyping) are useful in management of hepatitis C infected patients. The primary goal of antiviral therapy in chronic hepatitis C is a sustained virological response (SVR). The HCV genotype should be determined in every patient considered for antiviral therapy because the currently recommended treatment duration and ribavirin doses differ among HCV genotypes. Exact subtyping might gain increased importance for future therapies with direct-acting antiviral agents (DAA) because of differences of antiviral activities and barriers to resistance among HCV subtypes. Monitoring HCV RNA by a highly sensitive assay (LOD ≤ 15 IU/ml) is the basis for management of response guided therapy of chronic hepatitis C with pegylated IFN plus ribavirin. Rules for early discontinuation of antiviral therapy in non-responders and determination of optimal treatment durations in virologic responders have been developed for application of individualized treatment strategies.

Management of acute hepatitis C

The World Health Organization estimates that about 170 million people are infected with hepatitis C virus (HCV). Blood transfusions from unscreened donors and unsafe therapeutic procedures are the major modes of HCV transmission in the developing world, and injection drug use accounts for most newly diagnosed HCV infections in the developed countries. Acute infection with HCV leads to symptomatic hepatitis in only a minority of patients, and recent studies suggest that spontaneous clearance of virus is higher in symptomatic acute hepatitis C infection. Pooled data from various studies suggest that higher sustained viral clearance rates could be achieved with a shorter course of antiviral treatment in the early stages of chronic HCV infection. This article examines the diagnosis of acute infection and critically appraises the various treatment regimens.

Acute hepatitis C

Symptomatic acute hepatitis C occurs in only about 15% of patients who are infected with hepatitis C virus (HCV). Acute hepatitis C is most often diagnosed in the setting of post-exposure surveillance, or seroconversion in high-risk individuals (eg, health-care professionals or injecting drug users) previously known to be seronegative. Although transmission via transfusion and injecting drug use has declined in developed countries, unsafe blood products and medical practices continue to increase transmission of HCV in many developing countries. Clinically, acute hepatitis C can increase concentrations of alanine aminotransferase to ten times the upper limit of normal but almost never causes fulminant hepatic failure. Diagnosis of HCV infection in the acute phase is difficult since production of antibodies against HCV can be delayed by up to 12 weeks, and about a third of infected individuals might not have detectable antibody at the onset of symptoms. Therefore, testing for HCV RNA by PCR is the only reliable test for the diagnosis of acute infection. Symptomatic patients with jaundice have a higher likelihood of spontaneous viral clearance than do asymptomatic patients, and thus should be monitored for at least 12 weeks before initiating antiviral therapy. By contrast, asymptomatic patients have a much lower chance of spontaneous clearance, and might benefit from early antiviral therapy. Antiviral therapy for 12 weeks is generally effective in treating patients who are HCV RNA negative after 4 weeks of treatment; lengthier courses could be needed for those who relapse or fail to show early virological clearance.

[Acute hepatitis C in 2005]

There have been numerous new data in the field of acute hepatitis C in the past few years. The goal of this study was to gather recent results in the literature to determine the best current therapeutic strategy of acute hepatitis C. Epidemiology has made enormous progress with the disappearance of acute post transfusion hepatitis C. Infection by intravenous drug-addiction has became prevalent, and nosocomial and sexual modes of transmissions are now seen. At the same time, the average age of the infected patients has dropped by 13 years, and the proportion of acute forms with a spontaneously favourable outcome have increased compared to the period before 1995. Understanding of the predictive factors of cure have become important, particularly not to treat acute hepatitis C which will have a spontaneously favorable outcome. Waiting from 8 to 12 weeks after jaundice or symptomatic forms is recommended. The decision to treat must be made in the first 6 months, since the results are better compared to a late and longer treatment. Monotherapy by pegylated interferon for 6 months ensures more than 90% of sustained viral response. Shorter treatment is possible but high daily doses of interferon are necessary, reducing tolerance. Finally bi therapy with a interferon and ribavirin is not beneficial

Current issues in the diagnosis of hepatitis B and C virus infections

Diagnostic tests for hepatitis B virus infection are well established, although development of format and components continues. Variants of HBV with amino acid changes in the major antigenic determinant of the surface protein (HBsAg), and which may escape neutralisation by anti-HBs, have been described in many countries. The increasing reliance on monoclonal antibodies in the formulation of new assays for HBsAg raises the question of whether these surface variants may escape detection. The prevalence of variants which are unable to synthesise the e antigen (precor mutants), especially in certain geographical areas, means that the absence of HBeAg in carriers, with or without anti-HBe, does not necessarily indicate clearance of viraemia. The discovery of hepatitis C virus was followed rapidly by evidence of considerable sequence variation among different isolates. At least six major genotypes of HCV are recognised worldwide. Nonetheless, current assays seem reliable for detection of antibodies to this diverse virus. Assays for antigen are not available and diagnosis of viraemia requires sensitive detection of the viral genome, for example using reverse transcription and the polymerase chain reaction (RT-PCR). Evaluation of the efficacy of anti-viral therapy requires quantitative assays, adding a further degree of complexity. Other tests, such as the branch DNA (bDNA) assays are available, but lack sensitivity. Whether different genotypes of HCV vary in their pathogenicity and response to therapy remains contentious and convenient methods for determination of the genotype (or equivalent serotyping assays) are required to resolve this issue.

Virus-specific antibody titres in different phases of hepatitis C virus infection

This study aimed to examine anti hepatitis C virus (HCV) antibody titres, their changes and differences in acute, chronic and past HCV infection and to examine them after IFN-alpha-therapy. Ninety five patients were studied in a cross-sectional investigation and 18 of them were followed long-term. Titres of IgM and IgG antibodies against core, NS3, NS4 (A + B), NS5A proteins were determined by the third generation enzyme immunoassays. Patients with acute hepatitis C developed IgG antibodies against core protein in titres 1/5-1/800 and against individual NS proteins at the same titres. During the first to second month of acute hepatitis C IgG antibody titres to HCV proteins were very low, but they had risen considerably by the fourth to sixth month. Anti-HCV IgM antibodies were found in half the acute hepatitis serum samples, titres were 1/5-1/40. Sixty individuals with chronic hepatitis C showed IgG antibodies against core in titres 1/800-1/40,000 and against individual NS proteins in titres 1/5-1/20,000. Eight patients with chronic hepatitis C had invariable anti-HCV IgG antibodies over 2-3 years. About 81.7% of chronically infected patients had anti-HCV IgM antibodies in titres 1/5-1/160. Patients with resolution of HCV infection showed only anti-core IgG antibodies (titres 1/5-1/200) or no virus-specific antibodies. Individuals with different response to IFN-alpha-therapy showed two distinct patterns of anti-HCV antibody titres. Acute and chronic HCV infection may be distinguished by anti-core titres.

Approaches of the diagnosis of hepatitis viruses

Hepatitis virus infection occurs in close to a billion people worldwide at some point in their lifetimes. Hepatitis B and C viruses together account for infections in half a billion people and are considered the most carcinogenic of any known biological agent. The diagnostic approaches to detect hepatitis viruses are discussed.

Diagnostic tests for hepatitis C

Two categories of virological assays are in practice used for the diagnosis and management of hepatitis C virus (HCV) infection, including serological and molecular biology-based assays. Serological assays include: screening tests based on enzyme immunoassays (EIAs); supplemental "analytical" assays based on immunoblot testing; and serological assays detecting genotype-specific antibodies for the serological determination of HCV genotype, so-called "serotyping" assays. Molecular assays include: qualitative assays, detecting HCV RNA in body fluids; quantitative assays measuring HCV viral load, a parameter that estimates the level of HCV replication in the liver; and tests analyzing the sequence of HCV genomes (genotyping assays).

Diagnostic value of anti-hepatitis C virus (HCV) core immunoglobulin M in recurrence of HCV infection after orthotopic liver transplantation

The significance of anti-hepatitis C virus (HCV) core immunoglobulin M (IgM) and its relationship with genotypes, alanine aminotransferase abnormality, and histological data were studied for 18 patients who had undergone orthotopic liver transplantation due to HCV-related end-stage disease. During follow-up, IgM response seemed to be associated with the recurrence of HCV infection but did not correlate with abnormal alanine aminotransferase levels and histological data. In addition, the results of this study indicated that the detection of HCV RNA is critical for diagnosis of reinfection in liver transplantation.

Significance of IgM anti-HCV core level in chronic hepatitis C

AIM

To investigate the significance of IgM antibody to hepatitis C virus (HCV) core antigen (IgM anti-HCV core) in chronic hepatitis C.

METHODS

In a group of 112 patients with histologically proven chronic hepatitis C positive for HCV RNA, IgM anti-HCV core level was studied by a sensitive semi-quantitative enzyme immunoassay. Quantitation of serum HCV RNA was done by a second generation bDNA assay and determination of HCV genotype by RT-PCR and reverse hybridization.

RESULTS

IgM anti-HCV core was detected in 72 (64.3%) of the 112 patients. ALT levels were significantly higher in IgM anti-HCV core positive than negative patients. No other significant difference was observed in any of the patients' characteristics between IgM anti-HCV core positive and negative groups. On the contrary, IgM anti-HCV core level was found to be significantly higher in females than in males, in patients with moderate or severe chronic hepatitis, in patients with high HCV RNA levels and in patients infected with HCV genotype 1b. Moreover, IgM anti-HCV core level was significantly correlated with age and ALT level. Multiple regression analysis showed that IgM anti-HCV core level was significantly related only to the HCV genotype (p=0.001), histological grade (p=0.017) and ALT level (p=0.038).

CONCLUSIONS

Our data support the hypothesis that IgM anti-HCV core level is associated mainly with HCV genotype and secondly with liver disease necroinflammatory activity. These associations may have implications in the pathogenesis of chronic hepatitis C.

The presence of rheumatoid factor in sera from anti-HCV positive blood donors interferes with the detection of HCV-specific IgM. Trent HCV Study Group

BACKGROUND/AIMS

IgM anti-HCV has been reported as a useful marker of disease activity and of likely response to interferon therapy in patients with chronic hepatitis C virus infection. Sera from patients with hepatitis C virus infection may contain rheumatoid factor. This study was designed to investigate the possible effect of rheumatoid factor in an IgM anti-HCV assay.

METHODS

Sera from 75 blood donors with chronic hepatitis C virus infection were tested for the presence of IgM anti-HCV using a core-derived peptide as antigen, before and after removal of IgG. These sera and appropriate control sera were also tested for the presence of rheumatoid factor.

RESULTS

Removal of IgG prior to IgM testing resulted in a significant loss of reactivity in the IgM anti-HCV assay in 30/41 sera that were positive in this assay when tested untreated. Seventy per cent of anti-HCV positive sera were also positive for rheumatoid factor.

CONCLUSIONS

Rheumatoid factor causes significant false positive reactivity in IgM anti-HCV detection assays. The results of assays that do not account for this interference should be viewed with caution.

Serologic diagnosis of viral hepatitis

Viral hepatitis has become a difficult field in which clinical and laboratory skills are needed to establish the correct diagnosis and plan for the appropriate therapy. For example, it is no longer enough to diagnose chronic hepatitis B or C. Now, the viral titer or viral genotype must be known. The laboratory test then must be understood in the context of the clinical presentation. This article helps the clinician to acquire such working knowledge. It summarizes available data for hepatitis A, B, C, D, and E. It also includes the recently discovered viral agents, hepatitis G and the hepatitis GB agents.

Liver-infiltrating and circulating CD4+ T cells in chronic hepatitis C: immunodominant epitopes, HLA-restriction and functional significance

The aim was to assess the specificity and functional significance of liver-infiltrating and peripheral blood T cells in chronic hepatitis C. Peripheral blood mononuclear cells hepatitis C virus from 50 of 58 (86.2%) patients with chronic hepatitis C virus infection and 6 of 28 (21.4%) controls showed a proliferative T cell response to at least one of 16 synthetic peptides covering highly conserved regions of the core, envelope (El) and non-structural regions (NS4) of hepatitis C virus. However, six immunodominant peptides were exclusively recognized by the proliferating blood mononuclear cells from 46 patients with chronic hepatitis C virus infection (79.3%). Fine specificity and HLA-restriction were studied with 15 peptide-specific CD4+ T cell lines and 23 T cell clones isolated from liver tissue and peripheral blood of 12 patients with chronic hepatitis C. It was demonstrated that the peptide-specific response of CD4+ T cells was restricted to the presence of autologous accessory cells and HLA-DR and -DP molecules. Eight peptide-specific T cell lines and five T cell clones derived from liver tissue and peripheral blood, released interferon-gamma (200-6600 pg/ml) and tumor necrosis factor-alpha (100-400 pg/ml) and no or little interleukin-4 (< 140 pg/ml) after peptide-specific or mitogeneic stimulation, thus resembling a Th1-like cytokine profile. Patients with active liver disease showed significantly higher proliferative responses to hepatitis C virus core peptides than asymptomatic hepatitis C virus carriers or complete responders to interferon therapy. In conclusion, class II-restricted CD4+ T cell responses to some immunodominant epitopes within the hepatitis core region correlated with disease activity in chronic hepatitis C virus infection. Functionally, liver-infiltrating and peripheral blood T cells released Th1-like cytokines in response to the specific stimulus. Thus, it can be suggested that CD4+ T cells can mediate the pathogenesis of chronic hepatitis C virus induced liver disease.

Demonstration of specific detection of anti-HCV IgM core antibodies

The specificity of IgM isotype response directed against the putative core of hepatitis C virus (HCV core IgM) was demonstrated in HCV IgM EIA reactive samples. No interference was noted when samples with increasing levels of rheumatoid factor (RF) alone, or in combination with graded concentrations of anti-HCV IgG (HCV IgG), were tested. No deterioration in assay specificity was seen in 30 sera from patients wih monoclonal gammapathies (all isotypes). With Protein G affinity chromatography, RF/HCV IgG immune complexes and HCV core IgM antibodies displayed different binding characteristics, HCV core IgM appeared in the buffer eluate while HCV IgG/RF remained bound. With sucrose density gradient centrifugation HCV core IgM sedimented at 17-19S.

Disease markers in blood donors at King Fahad Hospital, Al Baha

A total of 4683 donated blood units were screened for HCV-Ab, HBs-Ag, VDRL, malaria parasites and ALT between January 1993 and April 1994. Of the blood units, 7.7% were positive for one or two hepatitis markers (HCV-Ab, HBs-Ag), while 4.6% were positive for HCV antibody, and 3.3% of the 4.6% were accounted for by Egyptian blood donors. Thus, 73% of all positive blood units for HCV-Ab were from Egyptian donors, while the rate of positive blood units for Saudi blood donors was 0.9%. Three and one-tenth percent of the total blood units were positive for HBs antigen, 2.3% from the Saudi population. Thus, 75% of all positive blood units were from Saudi donors. The percentage for HBs-Ag blood units for Egyptians was 0.3%. The exact prevalence of HCV-Ab-positive blood units among Saudis was 1.2% and HBs-Ag-positive units was 3.3%. Prevalence of HCV-Ab-reactive blood units among Egyptians was 34% and HBs-Ag-positive units was 3.3%. HCV-RNA using PCR was detected in a total of 86% of the individuals reactive to HCV antibody. Forty-three percent of hepatitis-B- and/or C-reactive blood donors had elevated alanine aminotransferase (ALT). Elevated ALT was observed in a higher percentage among HCV-Ab-reactive blood donors as compared to HBs-Ag-reactive donors.

Quantitative assessment of hepatitis C virus RNA and IgM antibodies to hepatitis C core in chronic hepatitis C

BACKGROUND/AIMS

IgM antibodies to hepatitis C virus have been found in a variable proportion of patients with chronic hepatitis C. We have evaluated whether IgM anti-core antibodies correlate with viraemia or hepatic injury in chronic hepatitis C.

METHODS

Serum from 106 patients with chronic hepatitis C with varying stages of disease were tested for IgM anti-core hepatitis C virus by immunoassay. All patients were seropositive for IgG antibody to hepatitis C virus by second-generation ELISA; 25 had histologic cirrhosis and 57 chronic hepatitis. IgM anti-core was detected in 84/106 (79.2%) patients. HCV-RNA was tested by branched (bDNA) signal amplification assay or by polymerase chain reaction in 92 patients.

RESULTS

All IgM-anti-HCV positive patients had detectable HCV-RNA. Seventy of 87 (80.5%) HCV-RNA-positive patients were IgM anti-core positive. Levels of IgM anti-HCV were significantly higher in patients with HCV-RNA detected by bDNA than in those who were bDNA negative, but there was no correlation between HCV-RNA concentrations and IgM anti-HCV levels. Of the 84 patients with positive results for IgM anti-core hepatitis C virus, 59 (70.2%) had abnormal alanine aminotransferase levels. The levels of IgM anti-core hepatitis C virus were likewise significantly higher in those with abnormal alanine aminotransferase levels. There was no difference in the percentage of patients with a positive IgM anti-HCV, or in levels of IgM anti-core hepatitis C virus in those with chronic hepatitis versus cirrhosis.

CONCLUSIONS

These data suggest that the majority of patients with chronic hepatitis C virus infection are IgM anti-core hepatitis C virus positive, and the detection seems to be associated with viral replication and biochemical evidence of hepatic necrosis. IgM anti-core hepatitis testing may prove useful as an adjunct in the clinical assessment of patients with chronic hepatitis C.

Hepatitis C virus-specific B cell activation: IgG and IgM detection in acute and chronic hepatitis C

BACKGROUND/AIMS/METHODS

Immunological responses to hepatitis C virus infection have not been fully studied. In an attempt to clarify some immunopathogenetic aspects of B cell activation during acute and chronic hepatitis C virus infection and to identify markers of chronicity or of recovery, the humoral response in hepatitis C virus-infected patients was studied.

RESULTS

In children with acute jaundice, with negative markers of acute hepatitis A, B and E, six of 87 (6.9%) had detectable anti-HCV IgM, and only one (1.1%) had detectable anti-HCV IgG. In adults with acute jaundice, with negative markers of acute hepatitis A, B and E, ten of 23 (43.5%) had detectable anti-HCV IgM associated in eight patients with detectable anti-HCV IgG. In chronic hepatitis C virus-infected adult patients, all anti-HCV IgG seropositive, four of 14 (28%) patients had detectable HCV-IgM in serum. In vitro specific antibody production was inducible in a minority of patients. In acute and chronic hepatitis C virus-infection, IgM-HCV serology did not correlate with viremia as detected by polymerase chain reaction.

CONCLUSIONS

Therefore, the polymerase chain reaction remains at the moment the only direct marker to demonstrate hepatitis C virus viral replication in patients with acute and chronic hepatitis while anti-HCV IgM analysis alone has only a limited diagnostic value in hepatitis C virus-infection.

IgM anti-hepatitis C virus in patients with chronic non-A, non-B hepatitis and their relationship to viral replication

Patients with hepatitis C virus (HCV) infection may have different patterns of antibody response to various structural and non-structural viral antigens. We have correlated the serological patterns to the clinical features of chronic infection and to viral replication in 68 HCV-Ab-positive patients with chronic liver disease at different stages (19 with cirrhosis-hepatocellular carcinoma, 38 with chronic active hepatitis and 11 with chronic persistent hepatitis). Serum samples from each patient were assayed for HCV-IgM by enzyme immunoassay and for HCV-RNA by the polymerase chain reaction using primer sets derived from the 5'-non-coding region. The prevalence of HCV-IgM was high (54 patients (79.4%)) and the study showed a good correlation between high values of anti-HCV-IgM and the presence of HCV-RNA in serum, since HCV-RNA was detected in 35 of the 54 IgM-positive patients (64.8%) and notably in 19 of the 20 subjects with high levels of specific IgM. Conversely, all the 35 sera containing HCV-RNA were also reactive for HCV-IgM, while none of the HCV-IgM-negative sera was HCV-RNA reactive. Positivity rates for both HCV-RNA and IgM anti-HCV were higher in the more advanced stages of disease; thus, the clinical pattern of HCV chronic hepatitis seems to be strictly related to the serological pattern and the presence of HCV-RNA.

Levels of hepatitis C virus (HCV) RNA in serum and their relationship to levels of immunoglobulin M and G antibodies against HCV core protein

The presence and levels of hepatitis C virus (HCV) RNA and immunoglobulin M (IgM) and IgG antibodies against the virus core protein were determined in 449 serum specimens. Despite the fact that a relationship between the presence, but not the levels, of HCV RNA and HCV IgM was observed, the significance of HCV core IgM assays seems limited.

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.

Is the detection of anti-hepatitis C virus core IgM influenced by the presence of serum rheumatoid factor?

Rheumatoid factor (RF) induces false-positive results in the detection of serum antibodies, especially of the IgM type. About 70% of the patients with chronic hepatitis C have abnormal levels of serum RF. The aim of this study was to determine whether the presence of serum RF could influence the detection of anti-HCV core IgM, using an assay designed not to pick up RFs by the addition of goat antibodies directed against human IgG in the sample diluent. Serum anti-HCV core IgM antibodies and RF were sought in 60 patients with chronic hepatitis C. Serum anti-HCV IgG antibodies and anti-HCV core IgM antibodies were also sought in 101 patients with high levels of RF. Anti-HCV core IgM antibodies were found in 45% and serum RF in 72% of the patients with chronic hepatitis C. Neither the prevalence nor the levels of RF differed significantly between IgM positive and negative patients. Eight percent of the 101 patients with raised RF had anti-HCV antibodies and two of them had anti-HCV core IgM antibodies. No patient without anti-HCV antibodies had anti-HCV core IgM antibodies. These results show that: a) the detection of anti-HCV core IgM in patients with chronic hepatitis C is independent of the presence of serum RF; b) high titers of serum RF are not responsible for false-positive results of anti-HCV IgM tests. The study suggests that the test used could be a confident tool for studies on the significance of anti-HCV core IgM antibodies in chronic hepatitis C.

Significance of IgG and IgM HCV antibody secretion in vitro in patients with chronic hepatitis C: correlation with disease activity and response to interferon-alpha

Hepatitis C virus antibodies are found in the serum of most patients with chronic hepatitis C. However, the significance of the humoral response is still uncertain. In this study, in vitro IgG and IgM anti-hepatitis C virus secretion by peripheral blood mononuclear cells of patients with chronic hepatitis C was analyzed. Peripheral-blood mononuclear cells from 21 of 36 patients (58.3%) secreted IgG anti-hepatitis C virus in vitro, as demonstrated with anti-hepatitis C virus-specific enzyme immunoassays and recombinant immunoblot assays. Ten of the 36 patients (27.8%) showed both IgG and IgM anti-hepatitis C virus core in vitro. In 9 of these 10 patients, IgM anti-hepatitis C virus was also detected in serum. Patients with in vitro IgM or IgG anti-hepatitis C virus secretion had higher ALT levels in serum than did patients without such secretion in vitro (99.5 +/- 22.1 and 85.6 +/- 34.4 vs. 38.1 +/- 37.4 U/L; p < 0.0001, p < 0.001). Furthermore, with a histology activity score it was demonstrated that patients with in vitro IgM or IgG HCV antibodies (or both) had more severe chronic active hepatitis than did patients without in vitro hepatitis C virus antibody secretion (p < 0.01). To analyze the therapy outcome, we included in this study 18 patients who had received interferon-alpha previously. Seven of eight in vitro hepatitis C virus antibody-positive patients were nonresponders, whereas the in vitro hepatitis C virus antibody-negative patients were mostly complete therapy responders (8 of 10).(ABSTRACT TRUNCATED AT 250 WORDS)

IgM and IgA antibodies generated against hepatitis C virus core antigen in patients with acute and chronic HCV infection

Antibody subclasses directed against the core protein (HCc) of hepatitis C virus (HCV) were measured in 27 patients with acute non-A, non-B (NANB) hepatitis, and 99 patients with chronic HCV-associated liver disease. IgM, IgA, and IgG anti-HCc responses were observed in 11 (40.7%), 7 (25.9%), and 18 (67%) patients with acute NANB hepatitis, respectively. Twenty-four (24.2%) and 40 (40.4%) patients with chronic HCV infection also had detectable IgM and IgA, respectively. IgM anti-HCc inconsistently detected acute infection, and HCV ribonucleic acid (RNA) could be detected preceding the rise in anti-HCc antibodies in five consecutive patients with acute hepatitis. IgM anti-HCc also could not distinguish acute from chronic infection and did not correlate with histologic progression. However, the form of IgA present (polymeric vs monomeric) did discriminate acute from chronic infection and the IgA anti-HCc titer correlated with histologic evidence of liver disease in patients with chronic HCV infection.

IgG and IgM core antibodies and viral replication in hepatitis C virus carriers

We studied IgG and IgM antibodies to hepatitis C virus core protein (anti-HCVcore) in relation to serum virus RNA levels in 71 hepatitis C virus carriers. Viremic levels ranged from 10(4)-10(9) copies/ml and were high in 34 chronic active hepatitis patients compared with 17 asymptomatic carriers and 20 cases of chronic persistent hepatitis (p < 0.01). IgG anti-HCVcore was found in 67/71 (94%), but four asymptomatic carriers with low levels of viremia (10(4)-10(5.5) copies/ml) tested negative. IgM anti-HCVcore was found in patients with high levels of viremia (10(8)-10(9) copies/ml), and one (6%) asymptomatic carrier and nine (26%) chronic active hepatitis patients tested positive. In chronic hepatitis patients, viremic levels were significantly higher in cases positive for IgM anti-HCVcore than in negative ones (p < 0.01). However, no correlation was found between the occurrence of IgM anti-HCVcore and serum aminotransferase levels or the histologic activity index. These findings suggest that although IgG anti-HCVcore is sensitive, low viremic patients can escape this screening, and that the IgM anti-HCVcore is induced in association with high levels of virus replication.

Hepatitis C virus infection in pregnant women: detection by different anti-HCV immunoassays and serum HCV-RNA

To assess the seroepidemiology of hepatitis C virus (HCV) infection in pregnant women and explore the correlation between different anti-HCV immunoassays, we investigated 2 independent groups in Taipei: 1,687 pregnant women without screening for serum alanine aminotransferase (ALT) (group A) and 260 pregnant women with elevated ALT activity (> 45 IU/l) screened from 15,978 cases (group B). In group A, 11 women (0.65%) were found to be anti-HCV-positive by first-generation tests and 21 (1.24%) by second-generation tests, while 7 (2.69%) and 15 (5.77%) of the group B subjects were positive, respectively. The results of the second-generation assays, based either on recombinant proteins or synthetic peptides, were identical. Among the 36 second-generation anti-HCV-positive cases, 18 (86%) of the 21 cases in group A and 13 (87%) of the 15 cases in group B contained serum HCV-RNA by RT-PCR. We conclude that the prevalence of anti-HCV in pregnant Taiwanese women is 1.24%, and the prevalence is 5.77% among those with an elevated ALT level. HCV-RNA is present in 86% of the cases positive for anti-HCV. The discrepancy between positive anti-HCV and negative HCV-RNA in some pregnant women suggests that anti-HCV positivity in such cases may merely represent a past HCV infection or a fluctuating viremia.

IgM antibody to a hepatitis C virus core peptide (CP14) for monitoring activity of liver disease in patients with acute or chronic hepatitis C

Antibodies to the hepatitis C virus (HCV) core of various immunoglobulin classes were determined by enzyme immunoassays with three synthetic peptides, CP14 (amino acids 5-40 of the core protein), CP10 (5-23), and CP9 (39-74). In 135 patients with chronic type C liver disease, anti-CP14, anti-CP10, and anti-CP9 of IgG class were detected in 99%, 94%, 82%, respectively; those of IgM class in 86%, 69%, and 39%; and those of IgA class in 56%, 40%, and 4%. Thus anti-CP14 was more prevalent than anti-CP10 or anti-CP9 in every immunoglobulin class. The prevalence of IgM anti-CP14 was much higher (P < 0.001) in patients (116/135 or 86%) than in asymptomatic carriers of HCV (13/39 or 33%). In seven patients with acute hepatitis C, IgM anti-CP14 continued to decrease in two in whom hepatitis resolved, but increased in five in whom hepatitis once resolved and then exacerbated. IgM anti-CP14 was followed in 30 patients with chronic hepatitis C during 24 weeks while they received recombinant interferon alpha-2a. IgM anti-CP14 decreased remarkably within 8 weeks in all of them. Thereafter, it continued to decrease in nine patients who responded to interferon and lost HCV RNA from circulation, but started to increase in five non-responders who continued to have high titers of HCV RNA. In the remaining 16 patients in whom HCV RNA decreased once and then increased, IgM anti-CP14 continued to decrease till 20 weeks and then increased.(ABSTRACT TRUNCATED AT 250 WORDS)

Establishment and application of SPA-co-operated ELISA for detection of anti-HCV-IgM

A staphylococcus aureus protein A co-operated ELISA (SPA-ELISA) for the detection of anti-HCV-IgM has been established using HCV antigenic polypeptide, SPA-bearing germs and horseradish peroxidase labelled anti-human IgM. The specificity of SPA-ELISA has been confirmed by some substitution tests, blocking tests and destroying test with 2-mercaptoethanol. The results showed that the rate of anti-HCV-IgG in a group of patients with acute hepatitis and there were significant difference in anti-HCV-IgM was higher than that of anti-HCV-IgM detected rates between patients with acute hepatitis and those with chronic hepatitis (32.26%, P < 0.01). On the other hand, the positive rates of anti-HCV-IgM were 53.66% and 63.41% in transfusion associated hepatitis, 38.10% and 42.86% in sporadic hepatitis, 6.11% and 16.33% in people who have had active social activities, 40.00% and 10.00% in a group of blood donors respectively. Furthermore, taking into account the characteristics of HCV polypeptide used, its easiness of manipulation, and elimination of the interference of anti-HCV-IgG in sera, the new SPA-ELISA is believed to be of practical value in clinical and epidemiological studies of hepatitis C.

Comparison of three different immunoassays and PCR for the detection of hepatitis C virus infection in pregnant women in Taiwan

To compare different hepatitis C virus (HCV) immunoassays and HCV-RNA in pregnant women, we investigated two independent groups: 1,687 cases without screening for serum alanine aminotransferase (ALT) (group A) and 333 cases with elevated ALT (> 45 IU/l) (group B), after screening 21,459 pregnant women. In group A, 11 (0.65%) and 21 (1.24%) were anti-HCV-positive by first- and second-generation tests, respectively, while in group B 8 (2.40%) and 19 (5.71%) were positive, respectively. The results revealed by second-generation assays based on either recombinant protein or synthetic peptides were identical, as were the anti-HCV titers in group B. Among 40 second-generation anti-HCV-positive cases, 18 (86%) of 21 in group A and 17 (89%) of the 19 in group B contained serum HCV-RNA by RT-PCR. Thus the prevalence of anti-HCV in Taiwanese pregnant women is 1.24% versus 5.71% in those with elevated ALT level.

Immunoglobulin M reactivity towards the immunologically active region sp75 of the core protein of hepatitis C virus (HCV) in chronic HCV infection

Serum samples from a cohort of patients with chronic hepatitis C virus (HCV) infection were assayed for IgM anti-HCV/core reactivity with a "site-specific" ELISA, in which the solid phase was charged with the synthetic polypeptide analogue corresponding to the first 75 amino acids of the HCV core antigen (sp75). Thirteen of 24 (54%) patients exhibited IgM anti-sp75 reactivity. Both high-titered (1/16,000-1/32,000) and low-titered (1/1,000-1/4,000) IgM anti-sp75 reactive sera were found. IgM anti-sp75 antibodies persisted in the circulation over a long period in patients with fluctuating abnormal ALT levels. There was a striking association between detection of specific IgM anti-sp75 reactivity and the presence of HCV RNA in serum. Thus 11 of 15 (73%) sera containing HCV RNA also contained IgM anti-sp75 antibodies, while none of the HCV RNA-negative sera were IgM anti-sp75 reactive. Five of 11 patients without detectable levels of specific IgM anti-sp75 antibodies had their ALT levels returned to normal within 8 months to 3 years. Furthermore, a significant correlation was noted between the specific IgM anti-sp75 titers and the concentration of total plasma IgM, indicating that the immunological active region sp75 within the capsid of HCV has the capacity to induce an IgM secretion, which constitutes a substantial portion of the total plasma IgM, in patients with chronic HCV infection.(ABSTRACT TRUNCATED AT 250 WORDS)

Routine laboratory diagnosis of hepatitis C virus infection

Hepatitis C virus (HCV) is the major cause of parenterally transmitted non-A, non-B hepatitis. The analysis of the genomic sequence of HCV has facilitated the development of a number of diagnostic assays for testing circulating antibodies in serum from patients with HCV infection. Besides the first-generation ELISA and RIBA, which employed the C100-3 non-structural polypeptide, second-generation tests employing both structural and non-structural polypeptides are being rapidly introduced. Several coded panels were employed in a comparative study of HCV-SP ELISA (utilizing a new synthetic peptide whose sequence was derived from the structural region) along with first- and second-generation tests. On the basis of the results, evidently antigens corresponding to the structural components of the virus are more sensitive and specific for the early detection of HCV antibodies than tests using non-structural epitopes. Additionally epitopes of the structural region elicit a very strong antibody response in laboratory animals. An example of one such application is the detection of HCV specific antigens in semen from patients diagnosed with non-A, non-B (NANB) hepatitis. Semen samples from 9 patients clinically diagnosed as having NANB hepatitis were tested by an ELISA using antibodies against HCV-specific structural antigens. The semen from all 9 patients had HCV-specific structural antigens in comparison to semen from 5 healthy donors. Semen from 5 of the 9 patients had significant levels of the HCV-specific antigen. This approach to detecting HCV antigens could, if rigorously tested, evolve into promising new assays for detecting HCV.

Serum IgM antibodies to hepatitis C virus in acute and chronic hepatitis C

A standardized commercially available immunoassay is not available for detection of IgM antibodies against hepatitis C virus antigens (IgM anti-HCV). Therefore, different "in-house" enzyme immunoassays have been assessed. These assays vary greatly in sensitivity, but specificity seems satisfactory in all of them. A typical IgM antibody response to HCV antigens is usually found in nearly all patients with acute hepatitis C. This antibody response rarely precedes the appearance of IgG anti-HCV, and it persists for a few months at high titer. Low titers of IgM anti-HCV are detectable in 50-80% of cases with chronic hepatitis C. IgM anti-HCV reactivity is typically found during acute exacerbation of chronic hepatitis C. Furthermore, many patients with chronic active hepatitis C without acute exacerbation also have IgM anti-HCV. In these patients a correlation exists between the titer of IgM anti-HCV and the biochemical parameters of liver disease. When alpha interferon therapy induces a sustained remission of liver disease activity, positivity for IgM anti-HCV disappears in more than 70% of cases. In contrast, patients who do not respond to therapy rarely loose IgM anti-HCV. In conclusion, serum IgM antibodies to HCV antigens are reliable markers of active HCV-induced liver disease both in acute and in chronic HCV infection.

Immunoglobulin M antibody to hepatitis C virus during interferon therapy for chronic hepatitis C

Testing for immunoglobulin (Ig) M antibody to hepatitis C virus (anti-HCV) as a predictive factor of therapeutic response to recombinant interferon alfa (rIFN-alpha) in chronic hepatitis C was evaluated in 122 patients with IgG anti-HCV. IgM anti-HCV was present in the pretreatment sample of 88% of patients who responded to treatment, including 20 of 21 (95%) long-term responders and 24 of 29 (83%) responders who had relapses after cessation of therapy. In contrast, IgM anti-HCV was present in only 23 of 39 (59%) nonresponders and 22 of 33 (66%) untreated controls (P less than 0.05). The number of cases with detectable IgM anti-HCV tended to decrease in responder patients, which was more evident for complete responders (42%) than for responders who relapsed (72%). During follow-up, the antibody became undetectable in the majority of long-term responders (28% were still IgM anti-HCV positive) but remained detectable in 69% of responders who relapsed (P less than 0.05). No special changes were noted in nonresponder or control patients. Thus, testing for IgM anti-HCV may help to identify a subset of patients who will benefit from rIFN-alpha therapy in chronic hepatitis C.

Hepatitis C virus RNA and hepatitis C virus antibody in the serum of patients with abnormal liver function

In order to elucidate the relation between hepatitis C virus (HCV) RNA and antibody to HCV (anti-HCV) in serum, we examined samples of serum collected from 228 HBsAg-negative patients, with abnormal alanine aminotransferase (ALT) values, for HCV-RNA by nested polymerase chain reaction (PCR) assay and for anti-HCV using C100 protein as the antigen. HCV-RNA was detected in 99 (92.5%) of 107 anti-HCV-IgG-positive samples, regardless of ELISA optical density cut-off value (ELISA ratio), and in 34 (28.1%) of 121 anti-HCV-IgG-negative samples in which the frequency of the presence of HCV-RNA became higher in proportion to the ELISA ratio. Among 42 discordant cases (34 anti-HCV-IgG-negative, RNA-positive cases and eight anti-HCV-IgG-positive, RNA-negative cases), 10 were positive for anti-HCV-IgM (8/34 and 2/8, respectively) irrespective of clinical status. These findings suggest that in patients with abnormal ALT values, even if they are anti-HCV-IgG negative, HCV infection cannot be excluded. Furthermore, PCR assay for detecting HCV-RNA may be more suitable for identifying patients with infectious virus than is detection of anti-HCV-IgG. Detection of anti-HCV-IgM may also be useful.

Treatment of chronic hepatitis C by continuous subcutaneous infusion of interferon-alpha

The effectiveness of a daily continuous infusion of interferon-alpha was evaluated in 12 patients (10 males, 2 females; mean age of 33 years, range 19-62) with biopsy-proven chronic active hepatitis C. Nine million units (MU) of recombinant interferon-alpha 2A (rIFN-alpha 2A) were administered by continuous subcutaneous infusion with a portable syringe pump, Graseby model MS 16A, for 24 h over 28 days. A significant decrease (P less than 0.01) in median serum alanine aminotransferase (ALT) levels was observed after the first week of treatment (96 IU/L, range 58-263) with respect to the pre-treatment values (188 IU/L, range 119-670). ALT became normal in four patients only by the fourth week. When IFN was interrupted, an increase in ALT was observed in all patients (1.5 to 5 times the pre-treatment values). The maximum decrease in ALT coincided with a significant increase in serum levels of the enzyme 2',5'-oligoadenylate (2-5A) synthetase (two to fourteen times the pretreatment values) and these parameters were inverse-correlated (r = -0.598, P less than 0.05). 2-5A synthetase levels returned to pre-treatment values after discontinuing IFN administration. Hepatitis C virus (HCV) RNA (as detected by the polymerase chain reaction using oligonucleotide primers of the NS5 region) was positive in all cases, remaining so during the treatment period. IgM antibody to HCV (as tested by ELISA) was present in 10/12 cases at baseline without changes throughout the study. No irreversible side effects were noted during therapy, which needed to modify the schedule.(ABSTRACT TRUNCATED AT 250 WORDS)

Transient immunoglobulin M antibody response to hepatitis C virus capsid antigen in posttransfusion hepatitis C: putative serological marker for acute viral infection

The development of serological assays for hepatitis C virus (HCV) has made specific diagnosis possible. However, markers useful in indicating acute-phase HCV infection have not been identified. By an immunoblotting method, we characterized the IgM and IgG antibody response against HCV capsid antigen in patients with HCV infection. Among 88% of patients with acute posttransfusion hepatitis C recruited in a prospective study, there was a transient IgM antibody response. The IgM antibody appeared shortly after onset of hepatitis (average 3.7 weeks), persisted for several months (average 18 weeks), and then disappeared. In contrast, the IgG antibody persisted long-term once it appeared. Among patients with chronic hepatitis C with milder disease activities (serum aminotransferase increase above normal levels of less than 4-fold), the IgM antibody was negative in the majority (72%). In those with acute exacerbations (aminotransferase increase of greater than 10-fold), about 55% were negative for the IgM antibody. The reactivity of the IgM antibody in the rest was weaker or became negative upon further dilution of serum. The results suggest that IgM anti-capsid antibody may serve as a marker indicating acute or active HCV infection.