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

Variability of IgM response in hepatitis C virus infection

The IgM and IgG antibody response to various hepatitis C virus (HCV) antigens was studied in 8 patients who acquired posttransfusion HCV infection. IgM anti-HCV was detectable in only 4 of these patients, coincident with (1 patient) or later than (3 patients) the IgG anti-HCV response. Seven patients had initially decreasing IgG anti-HCV titres, indicating passive transfer of antibodies from donor to recipient. All 8 patients showed active IgG seroconversion, as demonstrated by increasing IgG anti-HCV titres, on average, 75 days after infection. Five years after infection, all patients were still reactive for IgG anti-HCV antibodies and 7 were positive for HCV RNA by the polymerase chain reaction (PCR). Two of these PCR positive patients were also reactive for IgM anti-HCV. It is concluded that the serology of HCV infection does not follow the classical pattern of IgM response preceding detection of IgG. The IgM response may be absent, late, or persistent after HCV infection. The serological diagnosis of recent HCV infection should be based on the polymerase chain reaction or rising IgG titres in at least 2 sequential patient blood samples.

Expression in E. coli and purification of a chimeric p22-NS3 recombinant antigen of hepatitis C virus (HCV)

A recombinant antigen (p22-NS3), possessing putative HCV nucleocapsid protein (p22) and non-structural protein 3 (NS3) epitopes, was heavily expressed in E. coli and purified. The p22-NS3 purified recombinant antigen strongly reacts with sera containing human antibodies directed against p22 and NS3 providing a starting point for the design of an HCV single all-encompassing antigen for a blood screening assay.

Immunoglobulin M antibodies against hepatitis C virus antigens: significance and applications

The immunoglobulin M antibody against hepatitis C viral capsid (core) antigen has been found to be a possible marker for acute infection in post-transfusion hepatitis C. We extended this observation to a sporadic hepatitis C. In addition, a modified recombinant immunoblot assay (RIBA) that contained three HCV antigens (capsid, NS3 and NS5) in one strip was developed and used to study the antibody response among patients. This allowed a simultaneous comparison of either immunoglobulin M or G specific to individual HCV antigen and yielded more information. The assay was found useful in the diagnosis of acute hepatitis C in clinically uncertain cases.

Molecular characterization of hepatitis C and E viruses

The molecular features of each of the major viruses of non-A, non-B hepatitis, namely hepatitis C virus (HCV) and hepatitis E virus (HEV) are briefly described. The organization of the genome of each of these viruses is discussed and compared to those of other related or distantly related viruses that contain single-stranded, positive-sense RNA genomes. HCV has been tentatively classified as a separate genus within the Flaviviridae, whereas HEV has been loosely associated with caliciviruses and subsequently assigned to the Caliciviridae, although it does possess unique genetic features not found in other caliciviruses.

Community acquired viral hepatitis B and C in the United States

In the United States, most reported cases of hepatitis B occur in adults as a result of behavioural, lifestyle, or occupational exposures, but a significant number of children also become infected in well defined settings. Although only 1-3% of acute hepatitis B virus (HBV) infections occur in children under 5 years of age, they account for 20-30% of all chronic infections. A new strategy for HBV prevention in the USA includes integration of HBV vaccine into childhood immunisation schedules. Vaccination strategies that target high risk groups have not been effective. To determine the frequency and severity of community acquired chronic hepatitis C, patients with acute non-A, non-B hepatitis identified in four sentinel counties in the United States were followed prospectively. Hepatitis C virus (HCV) infection was found in 106 (82%) of 130 patients. Ninety three per cent of the HCV positive patients had a risk factor for their infection: 59% parenteral, 6% sexual or household, and 28% low socioeconomic level. Chronic hepatitis developed in 62%, independently of the risk factor for infection. HCV-RNA persisted in most patients, including those with biochemical resolution of their hepatitis. This study suggests that HCV may be a major cause of liver disease and persistent viraemia in the United States.

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

BACKGROUND

Chronic liver disease develops in more than half of patients with post-transfusion hepatitis C, but little is known about the natural history of community-acquired hepatitis C.

METHODS

In 1985 and 1986 we identified adults with acute non-A, non-B hepatitis in four counties in the United States and followed them prospectively. We used three markers to detect hepatitis C virus (HCV) infection in stored samples of serum: antibody to HCV (anti-HCV) detected by second-generation serologic assays; HCV RNA detected by polymerase-chain-reaction assay; and antibody to HCV antigen (anti-HCVAg) detected by fluorescent-antibody-blocking assay.

RESULTS

Of 130 patients with non-A, non-B hepatitis, 106 (82 percent) had HCV infection, 93 were positive for anti-HCV, and 13 were positive only for HCV RNA or anti-HCVAg. Chronic hepatitis developed in 60 (62 percent) of 97 HCV-infected patients followed for 9 to 48 months, with no relation to the risk factors for infection. Ten of the 30 patients who had liver biopsies had chronic active hepatitis. In samples collected 42 to 48 months after the onset of hepatitis, HCV RNA was detected in 12 of 13 tested patients with chronic hepatitis and in all 15 tested patients with hepatitis that had resolved. Anti-HCV persisted in all but two of the initially positive patients, for a rate of antibody loss of 0.6 per 100 person-years.

CONCLUSIONS

Patients with community-acquired hepatitis C have a high rate of chronic hepatitis. HCV may be a major cause of chronic liver disease in the United States, and in most patients HCV infection seems to persist for at least several years, even in the absence of active liver disease.

Recent developments in the molecular cloning and characterization of hepatitis C and E viruses

The molecular properties of the genomes of both hepatitis C virus (HCV) and hepatitis E virus (HEV), the major etiologic agents of non-A, non-B hepatitis, are briefly described. The organization of the genome of each of these viruses is discussed and compared to those of other related or distantly related viruses that contain single-stranded, positive-sense RNA genomes. In the case of HEV, the reactivity of expressed proteins and genetic divergence of geographically distinct isolates are also described within the context of sequence variation, type-common epitopes and type-specific epitopes.