Hepatitis C viral markers in patients who received blood that was positive for hepatitis C virus core antibody, with genetic evidence of hepatitis C virus transmission

Hepatitis C virus transmission dynamics in injection drug users

Hepatitis C virus (HCV) presents several challenges to the development of prevention programs. HCV infection is persistent in up to 80% of cases, and viremic individuals may transmit infection to others. With 65-90% of injection drug users anti-HCV positive, a large reservoir of infection exists in most drug-injector populations. Studying the genetic variability of HCV infections could permit researchers to reconstruct chains of viral transmission in IDUs. However, the relationship of HCV to HIV epidemiology remains unclear and may depend on whether the proportions of infectious persons in the population are similar for both viruses.

Mode of hepatitis C virus infection, epidemiology, and chronicity rate in the general population and risk groups

Since the discovery of the hepatitis C virus (HCV), it has become evident that this infectious agent is a primary cause of posttransfusion and sporadic non-A, non-B hepatitis. Identification and introduction of surrogate markers for posttransfusion hepatitis and later introduction of anti-HCV screening has decreased the incidence of posttransfusion hepatitis. Community-acquired HCV infection is less common than posttransfusion HCV hepatitis. HCV infection may lead to liver cirrhosis without prior evidence of laboratory or histologic infection. Populations at risk for HCV infection include patients receiving organ transplants, health care workers, infants born to HCV-infected mothers, and hemodialysis patients. Intravenous drug abusers and their sexual partners also demonstrate a high rate of HCV infection. Nosocomial HCV transmission may occur despite the observance of universal precautions. Dental or surgical intervention, salivary inoculation, family members infected with HCV, cocaine abuse, HIV infection, and lower socioeconomic status also each correlate with an increased risk of infection. HCV infection is associated with many immune-mediated diseases. There may also be some relationship between human leukocyte antigens and HCV infection. Since there currently is no HCV vaccine, prevention of exposure remains the only possibility for reducing HCV transmission and prevalence.

Virology of hepatitis C virus

Hepatitis C virus (HCV) has been identified as the main causative agent of posttransfusion non-A, non-B hepatitis. Through recently developed diagnostic assays, routine serologic screening of blood donors has prevented most cases of posttransfusion hepatitis. The purpose of this paper is to comprehensively review current information regarding the virology of HCV. Recent findings on the genome organization, its relationship to other viruses, the replication of HCV ribonucleic acid, HCV translation, and HCV polyprotein expression and processing are discussed. Also reviewed are virus assembly and release, the variability of HCV and its classification into genotypes, the geographic distribution of HCV genotypes, and the biologic differences between HCV genotypes. The assays used in HCV genotyping are discussed in terms of reliability and consistency of results, and the molecular epidemiology of HCV infection is reviewed. These approaches to HCV epidemiology will prove valuable in documenting the spread of HCV in different risk groups, evaluating alternative (nonparenteral) routes of transmission, and in understanding more about the origins and evolution of HCV.

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.