Current status of the molecular genetics of hepatitis C virus and its utilization in the diagnosis of infection.

BACKGROUND: Since the discovery of hepatitis C virus (HCV) as a major cause of non-A non-B hepatitis, advances have been made in our understanding of the molecular biology of HCV and its relatedness to the flaviviruses and pestiviruses. The use of molecular techniques to construct an antibody assay has enabled the accumulation of information concerning the natural history and pathogenesis of HCV infection. OBJECTIVES: The objective was to review the literature to March 1994 on the structure, function and genetics of HCV and to correlate these findings with approaches to diagnosis that have contributed to our understanding of HCV infections. STUDY DESIGN: We reviewed the virological and medical literature from 1988 to March of 1994 with a focus on the stated objectives. RESULTS: Although the structure of HCV has been well-defined, our knowledge of the function of all the genes of HCV is incomplete. Structural core and envelope proteins as well as enzymes have been described. The 5' end of the polypeptide is most conserved. Genotyping of isolates varies according to the part of the gene examined. Several genotypes exist and tend to predominate in global populations. Antibodies to the various proteins can be measured by EIA assays and positive specimens often require confirmatory testing. Uniquely sensitive nucleic acid detection systems for RNA amplified by PCR have enabled a better understanding of the natural history, epidemiology and responses to treatment. CONCLUSIONS: Well-designed studies for the detection of nucleic acid, antibodies and antigens using a variety of viral gene products will provide even more information about HCV infections and help lead to treatment and prevention.

Enzyme immunoassays and related procedures in diagnostic medical virology.

This review article describes several applications of the widely used enzyme immunoassay (EIA) procedure. EIA methods have been adapted to solve problems in diagnostic virology where sensitivity, specificity, or practicability is required. Concurrent developments in hybridoma and conjugation methods have increased significantly the use of these assays. A general overview of EIA methods is given together with typical examples of their use in diagnostic medical virology; attention is drawn to possible pitfalls. Recent advances in recombinant DNA technology have made it possible to produce highly specific nucleic acid probes that have a sensitivity approximately 100 times greater than that of EIA. Some applications of these probes are described. Although the non-labelled nucleic acid probes for use in the field are not as refined as non-labelled immunoassays, their range of applications is expected to expand rapidly in the near future.

[Detection of intracellular herpes virus antigens by immuno-enzyme procedures]. / Détection des antigènes intracellulaires des virus herpès par procédés immuno-enzymatiques.

The antigens of herpes simplex virus types 1 and 2 are detected and localized in vitro in Hep-2 cells by indirect and direct immunoperoxidase. The direct procedure is applied successfully for the diagnosis of genital disease on cytosmears of cervical cells of patients with herpes simplex type 2 infection. With other procedures, as anti-complement immunoperoxidase (ACIP) and anti-IgG immunoperoxidase (AIIP) the Epstein-Barr Nuclear Antigen (EBNA) was detected precisely in EB3, Jijoye and Raji lymphocytes using anti-EBNA antibodies from patients with nasopharyngeal carcinoma or Burkitt lymphoma, in dilution 1:10-1:5120. The indirect immunoperoxidase localized intracytoplasmic early antigen (EA) in 5% of EA--positive Raji cells induced by superinfection of EBV. The viral capsid antigen (VCA) is detected by this method in 5%-10% of virus producing cell lines Jijoye and P3HR-1. The standardized kits of immunoperoxidase procedures for diagnosis of intracellular viral antigens using monoclonal antibodies are under investigation.

Detection of Epstein-Barr virus antigens and antibodies by peroxidase-labeled specific immunoglobulins.

Detection of the Epstein-Barr (EBV) antigens, early antigen (EA), viral capsid antigen (VCA), and nuclear antigen (EBNA) by the indirect immunoperoxidase technique was highly sensitive. Antibody titers to EBNA, EA, and VCA were determined in more than 25 sera of patients with Burkitt lymphoma (BL), nasopharyngeal carcinoma (NPC), or normal persons. A good correlation between the titers of these antigens was obtained by the immunoperoxidase and immunofluorescence methods. The indirect (anti-IgG) immunoperoxidase technique for the detection of EBNA is, in contrast to the indirect immunofluorescence method, highly sensitive. EBNA was associated with the chromosomes in cells arrested in the metaphase with colchicine.

[Zona ophthalmica and dendritic keratitis]. / Zona ophtalmique et kératite dendritique

Two cases of herpes zoster ophthalmicus with dendritic keratitis are reported. Virological studies confirmed the double infection with herpes simplex type 1 virus in the corneal lesions and herpes zoster virus in the cutaneous lesions. We suggest the use of the immunoperoxidase test to identify the viral agent mainly because of its rapid and specific results. We are against the use of local steroids in dendritic keratitis unless the etiological agent is proved to be herpes zoster virus and not herpes simplex virus.