A competitive reverse transcription-polymerase chain reaction assay for quantitation of GB virus C/hepatitis G virus RNA that circumvents heteroduplex artifact

The Kunkel legacy and hepatitis C virus infection

In commemoration of Henry Kunkel's 100th birthday, the effect of his legacy on the investigation of hepatitis C virus is recounted. The delineation of a major cross-idiotype (WA) among patients with essential mixed cryoglobulinemia led to the discovery that HCV was the etiologic agent for this disease. Studies of the cryoglobulins led to the discovery that WA RF reacted specifically with HCV-VLDL like particles that on electronmicroscopy and binding studies appeared to be the virion within a lipid shell. This particle mediates cell entry via LDLr and may serve to avoid the immune response by masking the virion. In addition, the WA B cell may be a prognostic marker for cutaneous vasculitis and B cell malignancy in HCV-infected patients. In commemoration of Henry Kunkel's 100th birthday, this is an account of how his legacy had a role in the investigation of hepatitis C virus (HCV) infection. There is a bit of a historical basis for the legacy of this great immunologist having a role in virology. He began his research career studying hepatitis. Later he worked with HCV in his studies of mixed cryoglobulins although he didn't know it at the time. There may also have been a Kunkel historical basis for why he accepted me as fellow in his laboratory considering that my credentials paled in comparison with those of the fellows and PhD students in his laboratory. Like Henry I was drafted into the Navy following my internship, I had had minimal research experience in medical school and only one minor publication, and I had a passion for clinical investigation. It may have been fortuitous that while on active duty at the Bayonne NJ Naval Base I visited Henry Kunkel in my Navy uniform and told him I was interested in studying SLE. I did not know at the time the dramatic role the Navy had played in his career or that one of his major training goals was to teach MDs to use clinical observation as a focus for delineating disease mechanisms in the laboratory. When I started work in the laboratory on discharge from the Navy, the first thing he told me was that it took five years to make a clinical investigator so I might as well get a Rockefeller University PhD while working in his laboratory. I was sure I would leave the laboratory after two years so I declined his offer. I did not leave until six years later!

Design, development and evaluation of a competitive RT-PCR for quantitation of GBV-C RNA

Although GB virus C (GBV-C) hepatocyte pathogenicity is still controversial, it appears that at least some strains of this virus are lymphotropic. During the past few years, several reports have documented an apparently beneficial role played by GBV-C in the course of HIV-1 infection. At present, a commercial kit for GBV-C RNA quantitation is not available. In this study, a competitive RT-PCR method for GBV-C in serum samples is described. The sensitivity of the assay proved to be 10(4) and 10(3) genomic equivalents for positive and negative sense RNAs, respectively. This method will discriminate specifically between positive and negative strand RNAs with a discrimination index of at least five log10. Out of 60 samples from different hematological disorders (n = 49), HIV-1 positive patients (n = 7), and blood donors (n = 4), 10 proved to be GBV-C RNA positive. Viral load ranged from 1.1 x 10(7) to 2.34 x 10(8) genomic equivalents/ml. Such values correlated linearly (r = 0.986) with those obtained by a 10-fold serial dilution method. In studies exploring the GBV-C pathogenicity, the measurement of viral load may contribute to understand the possible mechanisms involved.

Hepatitis C virus and other flaviviridae viruses enter cells via low density lipoprotein receptor

Endocytosis of the Flaviviridae viruses, hepatitis C virus, GB virus C/hepatitis G virus, and bovine viral diarrheal virus (BVDV) was shown to be mediated by low density lipoprotein (LDL) receptors on cultured cells by several lines of evidence: by the demonstration that endocytosis of these virus correlated with LDL receptor activity, by complete inhibition of detectable endocytosis by anti-LDL receptor antibody, by inhibition with anti-apolipoprotein E and -apolipoprotein B antibodies, by chemical methods abrogating lipoprotein/LDL receptor interactions, and by inhibition with the endocytosis inhibitor phenylarsine oxide. Confirmatory evidence was provided by the lack of detectable LDL receptor on cells known to be resistant to BVDV infection. Endocytosis via the LDL receptor was shown to be mediated by complexing of the virus to very low density lipoprotein or LDL but not high density lipoprotein. Studies using LDL receptor-deficient cells or a cytolytic BVDV system indicated that the LDL receptor may be the main but not exclusive means of cell entry of these viruses. Studies on other types of viruses indicated that this mechanism may not be exclusive to Flaviviridae but may be used by viruses that associate with lipoprotein in the blood. These findings provide evidence that the family of LDL receptors may serve as viral receptors.

Hepatitis C virus but not GB virus C/hepatitis G virus has a role in type II cryoglobulinemia

OBJECTIVE

Hepatitis C virus (HCV) infection is associated with type II cryoglobulinemia. HCV is specifically concentrated in type II cryoglobulins and has been implicated in the cutaneous vasculitis associated with the disease. In contrast to HCV, a role for hepatitis G virus (HGV) in type II cryoglobulinemia has not been defined, although prevalences as high as 43% of HGV infections in type II cryoglobulinemia have also been reported.

METHODS

We studied 34 patients with type II and 29 patients with type III cryoglobulinemia associated with HCV infection, 6 patients with essential mixed cryoglobulinemia (EMC; all with type II), 50 hospital control patients, and 125 normal individuals. Serum HCV and HGV RNA were detected by reverse transcription-polymerase chain reaction (RT-PCR). In coinfected sera, HCV and HGV were quantitated by competitive RT-PCR assays. One coinfected patient was studied longitudinally for 6 years.

RESULTS

Two (5.9%) of 34 patients with HCV-infected type II cryoglobulinemia, none of 29 patients with type III cryoglobulinemia, and none of 6 patients with EMC were positive for HGV RNA, for an overall prevalence of 3.0% in mixed cryoglobulinemia. None of the control populations were positive for HGV. No statistical difference was seen between the prevalence in patients with type II cryoglobulinemia and the other populations studied. In coinfected sera, HCV, but not HGV, was concentrated in cryoglobulins, and HCV, but not HGV, correlated with cryoglobulinemia in a longitudinal study.

CONCLUSION

There is a low prevalence of coinfection with HGV in patients with mixed cryoglobulinemia and HCV infection in the United States. HCV is selectively precipitated by type II cryoglobulins in coinfected sera. HGV infection does not appear to have a role in mixed cryoglobulinemia.