MJA: Moaven, Should we be screening blood donors for hepatitis G virus?

Should we be screening blood donors for hepatitis G virus?

The case for screening

We should not take the risk that this virus may cause serious disease

Len D Moaven

MJA 1998; 169: 373-374
For the case against, see Wong et al

Introduction - Transfusion transmission of HGV - Effects of HGV - Screening issues - Costs of screening - Conclusion - References - Authors' details
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Introduction
Hepatitis G virus (HGV) and its strain variant, GB virus C, were discovered by workers looking for novel parenterally spread hepatotropic agents.^1,2 Currently, the only method of detecting HGV-infected individuals is by using nucleic acid amplification methods, such as the reverse transcription polymerase chain reaction (RT-PCR), to test for HGV RNA. Results from these methods suggest that 1%-4% of volunteer blood donors in developed countries are HGV RNA positive,^3-6 and that most of these donors are chronic carriers.⁶ It is not yet known why there is such a high prevalence of chronic HGV carriage in blood donors. Mother-to-baby⁷ and sexual transmission⁸ may be important in the transmission of this virus; however, HGV is known to be transmitted by blood transfusion.⁹ This has been carefully documented by studying HGV-infected donors and the recipients of their blood and demonstrating a temporal relationship between donation of blood products and acquisition of HGV.^3,5,10-12 In some studies, this has been further confirmed by sequencing the HGV isolates and demonstrating a close relationship between viruses in the donor and recipient.^5,11,12
Transfusion transmission of HGV
Approximately three-quarters of those who acquire HGV by blood transfusion will resolve their infection, and this appears to be associated with a protective immune response.^10,12,13 So not all recipients of HGV-infected blood will become chronic carriers of the virus; either they will resolve their infection or they will have been previously exposed and are immune to re-infection. Other host factors also play a role; for example, if the recipient is immunosuppressed it is more likely that viraemia will not resolve.¹² Even so, assuming that 15% of recipients are immune or already infected with HGV¹³ (unpublished data) and that only a quarter of the remainder will become chronic carriers (and that acute resolving infection has no effect on morbidity or mortality), that would still leave about one in five recipients of HGV-infected blood becoming chronic carriers and possibly suffering from the unknown sequelae of chronic HGV infection.
Effects of HGV
Currently, HGV is only associated with a mild rise in transaminases during acute infection -- not unusual for an acute viral infection.³ Persistent infection is probably not associated with significant liver disease, although some groups disagree.¹⁴ There is a contentious association with non-A-E fulminant hepatic failure,^15,16 but researchers in Australia, the United Kingdom and Japan have not found a direct causal link with fulminant liver disease.^12,17,18 The high prevalence of HGV infection in the general population makes demonstration of disease association particularly difficult. Hence, many researchers have argued that this virus is not currently of concern to transfusion medicine.^4,9
Although the evidence suggests that HGV is probably not hepatotropic, the virus is replicating somewhere in the infected individual. Many researchers have argued that HGV may be a latent, well adapted virus of low virulence.¹⁹ HGV is a positive-strand RNA virus and I would argue that it is unlikely that this type of virus could cause chronic infection and not be associated with a disease syndrome.⁶ The only other example of a positive-strand RNA virus (which commonly causes chronic infection in man) is hepatitis C virus (HCV). There are examples of so-called latent RNA infections in relatively short-lived animals, but it is difficult to imagine that these accurately reflect infection in man for many years. In any case, during this persistent infection HGV is not quiescent -- individuals have serum viraemias greater than 10⁷ genome equivalents per millilitre.²⁰ This is not indicative of a dormant infection,²¹ and it can be argued that such a viral burden must eventually have an adverse effect on the target organ of replication. Many HGV carriers appear to be healthy, but the same is true of HCV-infected blood donors and recipients. For example, Seeff et al failed to detect any significant increase in liver disease or mortality in HCV-infected blood recipients followed for almost 20 years.²² It is not until one looks in the gastroenterology or liver transplant clinics that an association between HCV and (liver) disease becomes evident. As the tissue tropism of HGV is yet to be defined, it is not surprising that the HGV syndrome has not yet been discovered. I believe that a significant disease association will be found -- perhaps we should look for it in the medical clinics (for example, the renal, rheumatoid or respiratory clinics) where people with the HGV syndrome may be ending up, rather than following them to see if they get there.
Screening issues
The RT-PCR test is a relatively expensive, technically demanding and time-consuming assay. It has been argued that this technology precludes mass screening of blood donors,^4,9 but these limitations can be overcome. There are now commercially available methods for RNA extraction, reverse transcription and polymerase chain reaction, and detection of RT-PCR products. These systems can overcome the problems of quality control, ease of use and reproducibility of the assay. By pooling serum samples (for example, pools of 10) economies can be made. For a blood transfusion service that processes about 250 000 donations per year, one could assume that this is made up of 125 000 regular blood donors (with 25 000 new donors every year). Assuming that the prevalence of HGV infection is relatively low in Australian blood donors,^6,12 that donors need only be screened once, and that 25 000 donations are used for blood products (incorporating sufficient inactivation steps so that HGV screening is not required), then initially only 100 RT-PCR reactions would need to be carried out each day, and this number would dramatically decrease over time. One could process these in "real-time", within 12-24 hours.
Costs of screening
Each RT-PCR test (including sample preparation and detection) would cost $35 using an automated station (Ms Dianne Young, Product Manager, Roche Diagnostics, personal communication). By adopting the above strategy the cost of reagents for a year would be in the order of $1 million for this service. This figure does not include labour or any other attendant costs. For comparison, the first generation anti-HCV testing would have cost, again for reagents alone, about $1.7 million in 1990 to screen 250 000 donations, using an assay that was only 70% sensitive. Although there is much resistance to nucleic acid testing as a screening method, I believe that it is the "ultimate" screening assay and that it will be introduced for currently screened pathogens within the next 18 months (Dr Peter Simmonds, Senior Lecturer, Edinburgh University, personal communication). Now is the time for blood banks to embrace this technology.
Another consideration regarding screening is what to tell individuals, for example blood donors, who are found to be HGV RNA positive. The paucity of information should not be an ethical dilemma. Individuals do not necessarily require "facts"; they need consistent information regarding the current state of knowledge. It is important for individuals to have reliable sources of information or contacts and to be followed up as new information is accrued.
Conclusion
Decision making under uncertainty is difficult, but we need to learn from the past.²³ Historically, many viruses are initially "orphaned" and are often described as latent or non-pathogenic during this period. It is perhaps instructive that this is true of some currently screened viruses -- including hepatitis B virus and HIV. The repercussions of not acting now and waiting for definitive data⁹ far outweigh the cost-benefits of any current actuarial decision. At the very least this debate should be widened to include the general community.²⁴ I, and others,¹¹ believe that the time has come to screen blood donors for hepatitis G virus.
References

Linnen J, Wages J Jr, Zhang-Keck ZY, et al. Molecular cloning and disease association of hepatitis G virus: a transfusion-transmissible agent. Science 1996; 271: 505-508.
Simons JN, Leary TP, Dawson JG, et al. Isolation of novel virus-like sequences associated with human hepatitis. Nat Med 1995; 1: 564-569.
Alter HJ, Nakatsuji Y, Melpolder J, et al. The incidence of transfusion-associated hepatitis G virus infection and its relation to liver disease. N Engl J Med 1997; 336: 747-754.
Roth WK, Waschk D, Marx S, et al. Prevalence of hepatitis G virus and its strain variant, the GB agent, in blood donations and their transmission to recipients. Transfusion 1997; 37: 651-656.
Yoshikawa A, Fukuda S, Itoh K, et al. Infection with hepatitis G virus and its strain variant, the GB agent (GBV-C), among blood donors in Japan. Transfusion 1997; 37: 657-663.
Moaven LD, Hyland CA, Young IF, et al. Prevalence of hepatitis G virus in Queensland blood donors. Med J Aust 1996; 165: 369-371.
Moaven LD, Tennakoon PS, Bowden DS, Locarnini SA. Mother-to-baby transmission of hepatitis G virus. Med J Aust 1996; 165: 84-85.
Stark K, Bienzle U, Hess G, et al. Detection of the hepatitis G virus genome among injecting drug users, homosexual and bisexual men, and blood donors. J Infect Dis 1996; 174: 1320-1323.
Alter HJ. G-pers creepers, where'd you get those papers? A reassessment of the literature on the hepatitis G virus. Transfusion 1997; 37: 569-572.
Pilot-Matias TJ, Carrick RJ, Coleman PF, et al. Expression of the GB virus C E2 glycoprotein using the Semliki Forest virus vector system and its utility as a serologic marker. Virology 1996; 225: 282-292.
Shimizu M, Osada K, Okamoto H. Transfusion-transmitted hepatitis G virus following open heart surgery [letter]. Transfusion 1996; 36: 937.
Moaven LD, Locarnini SA, Bowden DS, et al. Hepatitis G virus and fulminant hepatic failure: evidence for transfusion-related infection. J Hepatol 1997; 27: 613-619.
Moaven LD, Young IF, Bowden DS, Locarnini SA. Prevalence of hepatitis G virus antibodies in Queensland blood donors [letter]. Med J Aust 1997; 166: 507-509.
Colombatto P, Randone A, Civitico G, et al. Hepatitis G virus RNA in the serum of patients with elevated gamma glutamyl transpeptidase and alkaline phosphatase: a specific liver disease? J Viral Hepat 1996; 3: 301-306.
Yoshiba M, Okamoto H, Mishiro S. Detection of the GBV-C hepatitis virus genome in serum from patients with fulminant hepatitis of unknown aetiology. Lancet 1995; 346: 1131-1132.
Heringlake S, Osterkamp S, Trautwein C, et al. Association between fulminant hepatic failure and a strain of GBV virus C. Lancet 1996; 348: 1626-1629.
Kuroki T, Nishiguchi S, Tanaka M, et al. Does GBV-C cause fulminant hepatitis in Japan? [letter]. Lancet 1996; 347: 908.
Sallie R, Shaw J, Mutimer D. GBV-C virus and fulminant hepatic failure [letter]. Lancet 1996; 347: 1552.
Miyakawa Y, Mayumi M. Hepatitis G virus -- a true hepatitis virus or an accidental tourist? N Engl J Med 1997; 336: 795-796.
Hsieh SY, Yang PY, Chen HC, Liaw YF. Cloning and characterization of the extreme 5�-terminal sequences of the RNA genomes of GB virus C/hepatitis G virus. Proc Natl Acad Sci USA 1997; 94: 3206-3210.
Perelson AS, Neumann AU, Markowitz M, et al. HIV-1 dynamics in vivo: virion clearance rate, infected cell life-span, and viral generation time. Science 1996; 271: 1582-1586.
Seeff LB, Buskell-Bales Z, Wright EC, et al. Long-term mortality after transfusion-associated non-A, non-B hepatitis. The National Heart, Lung, and Blood Institute Study Group. N Engl J Med 1992; 327: 1906-1911.
Leveton LB, Sox HC Jr, Stoto MA. HIV and the blood supply: an analysis of crisis decision making. Transfusion 1996; 36: 919-927.
Kaldor JM. HTLV-I and blood safety: let the community decide. Med J Aust 1997; 166: 454-455.

(Received 14 May 1997, accepted 4 Feb 1998)

Authors' details

St John of God Pathology, Midland, WA.
Len D Moaven, FRCPA, Clinical Microbiologist.

Reprints: Dr L D Moaven, St John of God Pathology, 243 Great Eastern Highway, Midland, WA 6056.
E-mail: profpukATopera.iinet.net.au

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Introduction	Hepatitis G virus (HGV) and its strain variant, GB virus C, were discovered by workers looking for novel parenterally spread hepatotropic agents.^1,2 Currently, the only method of detecting HGV-infected individuals is by using nucleic acid amplification methods, such as the reverse transcription polymerase chain reaction (RT-PCR), to test for HGV RNA. Results from these methods suggest that 1%-4% of volunteer blood donors in developed countries are HGV RNA positive,^3-6 and that most of these donors are chronic carriers.⁶ It is not yet known why there is such a high prevalence of chronic HGV carriage in blood donors. Mother-to-baby⁷ and sexual transmission⁸ may be important in the transmission of this virus; however, HGV is known to be transmitted by blood transfusion.⁹ This has been carefully documented by studying HGV-infected donors and the recipients of their blood and demonstrating a temporal relationship between donation of blood products and acquisition of HGV.^3,5,10-12 In some studies, this has been further confirmed by sequencing the HGV isolates and demonstrating a close relationship between viruses in the donor and recipient.^5,11,12
Transfusion transmission of HGV	Approximately three-quarters of those who acquire HGV by blood transfusion will resolve their infection, and this appears to be associated with a protective immune response.^10,12,13 So not all recipients of HGV-infected blood will become chronic carriers of the virus; either they will resolve their infection or they will have been previously exposed and are immune to re-infection. Other host factors also play a role; for example, if the recipient is immunosuppressed it is more likely that viraemia will not resolve.¹² Even so, assuming that 15% of recipients are immune or already infected with HGV¹³ (unpublished data) and that only a quarter of the remainder will become chronic carriers (and that acute resolving infection has no effect on morbidity or mortality), that would still leave about one in five recipients of HGV-infected blood becoming chronic carriers and possibly suffering from the unknown sequelae of chronic HGV infection.
Effects of HGV	Currently, HGV is only associated with a mild rise in transaminases during acute infection -- not unusual for an acute viral infection.³ Persistent infection is probably not associated with significant liver disease, although some groups disagree.¹⁴ There is a contentious association with non-A-E fulminant hepatic failure,^15,16 but researchers in Australia, the United Kingdom and Japan have not found a direct causal link with fulminant liver disease.^12,17,18 The high prevalence of HGV infection in the general population makes demonstration of disease association particularly difficult. Hence, many researchers have argued that this virus is not currently of concern to transfusion medicine.^4,9 Although the evidence suggests that HGV is probably not hepatotropic, the virus is replicating somewhere in the infected individual. Many researchers have argued that HGV may be a latent, well adapted virus of low virulence.¹⁹ HGV is a positive-strand RNA virus and I would argue that it is unlikely that this type of virus could cause chronic infection and not be associated with a disease syndrome.⁶ The only other example of a positive-strand RNA virus (which commonly causes chronic infection in man) is hepatitis C virus (HCV). There are examples of so-called latent RNA infections in relatively short-lived animals, but it is difficult to imagine that these accurately reflect infection in man for many years. In any case, during this persistent infection HGV is not quiescent -- individuals have serum viraemias greater than 10⁷ genome equivalents per millilitre.²⁰ This is not indicative of a dormant infection,²¹ and it can be argued that such a viral burden must eventually have an adverse effect on the target organ of replication. Many HGV carriers appear to be healthy, but the same is true of HCV-infected blood donors and recipients. For example, Seeff et al failed to detect any significant increase in liver disease or mortality in HCV-infected blood recipients followed for almost 20 years.²² It is not until one looks in the gastroenterology or liver transplant clinics that an association between HCV and (liver) disease becomes evident. As the tissue tropism of HGV is yet to be defined, it is not surprising that the HGV syndrome has not yet been discovered. I believe that a significant disease association will be found -- perhaps we should look for it in the medical clinics (for example, the renal, rheumatoid or respiratory clinics) where people with the HGV syndrome may be ending up, rather than following them to see if they get there.
Screening issues	The RT-PCR test is a relatively expensive, technically demanding and time-consuming assay. It has been argued that this technology precludes mass screening of blood donors,^4,9 but these limitations can be overcome. There are now commercially available methods for RNA extraction, reverse transcription and polymerase chain reaction, and detection of RT-PCR products. These systems can overcome the problems of quality control, ease of use and reproducibility of the assay. By pooling serum samples (for example, pools of 10) economies can be made. For a blood transfusion service that processes about 250 000 donations per year, one could assume that this is made up of 125 000 regular blood donors (with 25 000 new donors every year). Assuming that the prevalence of HGV infection is relatively low in Australian blood donors,^6,12 that donors need only be screened once, and that 25 000 donations are used for blood products (incorporating sufficient inactivation steps so that HGV screening is not required), then initially only 100 RT-PCR reactions would need to be carried out each day, and this number would dramatically decrease over time. One could process these in "real-time", within 12-24 hours.
Costs of screening	Each RT-PCR test (including sample preparation and detection) would cost $35 using an automated station (Ms Dianne Young, Product Manager, Roche Diagnostics, personal communication). By adopting the above strategy the cost of reagents for a year would be in the order of $1 million for this service. This figure does not include labour or any other attendant costs. For comparison, the first generation anti-HCV testing would have cost, again for reagents alone, about $1.7 million in 1990 to screen 250 000 donations, using an assay that was only 70% sensitive. Although there is much resistance to nucleic acid testing as a screening method, I believe that it is the "ultimate" screening assay and that it will be introduced for currently screened pathogens within the next 18 months (Dr Peter Simmonds, Senior Lecturer, Edinburgh University, personal communication). Now is the time for blood banks to embrace this technology. Another consideration regarding screening is what to tell individuals, for example blood donors, who are found to be HGV RNA positive. The paucity of information should not be an ethical dilemma. Individuals do not necessarily require "facts"; they need consistent information regarding the current state of knowledge. It is important for individuals to have reliable sources of information or contacts and to be followed up as new information is accrued.
Conclusion	Decision making under uncertainty is difficult, but we need to learn from the past.²³ Historically, many viruses are initially "orphaned" and are often described as latent or non-pathogenic during this period. It is perhaps instructive that this is true of some currently screened viruses -- including hepatitis B virus and HIV. The repercussions of not acting now and waiting for definitive data⁹ far outweigh the cost-benefits of any current actuarial decision. At the very least this debate should be widened to include the general community.²⁴ I, and others,¹¹ believe that the time has come to screen blood donors for hepatitis G virus.
References	Linnen J, Wages J Jr, Zhang-Keck ZY, et al. Molecular cloning and disease association of hepatitis G virus: a transfusion-transmissible agent. Science 1996; 271: 505-508. Simons JN, Leary TP, Dawson JG, et al. Isolation of novel virus-like sequences associated with human hepatitis. Nat Med 1995; 1: 564-569. Alter HJ, Nakatsuji Y, Melpolder J, et al. The incidence of transfusion-associated hepatitis G virus infection and its relation to liver disease. N Engl J Med 1997; 336: 747-754. Roth WK, Waschk D, Marx S, et al. Prevalence of hepatitis G virus and its strain variant, the GB agent, in blood donations and their transmission to recipients. Transfusion 1997; 37: 651-656. Yoshikawa A, Fukuda S, Itoh K, et al. Infection with hepatitis G virus and its strain variant, the GB agent (GBV-C), among blood donors in Japan. Transfusion 1997; 37: 657-663. Moaven LD, Hyland CA, Young IF, et al. Prevalence of hepatitis G virus in Queensland blood donors. Med J Aust 1996; 165: 369-371. Moaven LD, Tennakoon PS, Bowden DS, Locarnini SA. Mother-to-baby transmission of hepatitis G virus. Med J Aust 1996; 165: 84-85. Stark K, Bienzle U, Hess G, et al. Detection of the hepatitis G virus genome among injecting drug users, homosexual and bisexual men, and blood donors. J Infect Dis 1996; 174: 1320-1323. Alter HJ. G-pers creepers, where'd you get those papers? A reassessment of the literature on the hepatitis G virus. Transfusion 1997; 37: 569-572. Pilot-Matias TJ, Carrick RJ, Coleman PF, et al. Expression of the GB virus C E2 glycoprotein using the Semliki Forest virus vector system and its utility as a serologic marker. Virology 1996; 225: 282-292. Shimizu M, Osada K, Okamoto H. Transfusion-transmitted hepatitis G virus following open heart surgery [letter]. Transfusion 1996; 36: 937. Moaven LD, Locarnini SA, Bowden DS, et al. Hepatitis G virus and fulminant hepatic failure: evidence for transfusion-related infection. J Hepatol 1997; 27: 613-619. Moaven LD, Young IF, Bowden DS, Locarnini SA. Prevalence of hepatitis G virus antibodies in Queensland blood donors [letter]. Med J Aust 1997; 166: 507-509. Colombatto P, Randone A, Civitico G, et al. Hepatitis G virus RNA in the serum of patients with elevated gamma glutamyl transpeptidase and alkaline phosphatase: a specific liver disease? J Viral Hepat 1996; 3: 301-306. Yoshiba M, Okamoto H, Mishiro S. Detection of the GBV-C hepatitis virus genome in serum from patients with fulminant hepatitis of unknown aetiology. Lancet 1995; 346: 1131-1132. Heringlake S, Osterkamp S, Trautwein C, et al. Association between fulminant hepatic failure and a strain of GBV virus C. Lancet 1996; 348: 1626-1629. Kuroki T, Nishiguchi S, Tanaka M, et al. Does GBV-C cause fulminant hepatitis in Japan? [letter]. Lancet 1996; 347: 908. Sallie R, Shaw J, Mutimer D. GBV-C virus and fulminant hepatic failure [letter]. Lancet 1996; 347: 1552. Miyakawa Y, Mayumi M. Hepatitis G virus -- a true hepatitis virus or an accidental tourist? N Engl J Med 1997; 336: 795-796. Hsieh SY, Yang PY, Chen HC, Liaw YF. Cloning and characterization of the extreme 5�-terminal sequences of the RNA genomes of GB virus C/hepatitis G virus. Proc Natl Acad Sci USA 1997; 94: 3206-3210. Perelson AS, Neumann AU, Markowitz M, et al. HIV-1 dynamics in vivo: virion clearance rate, infected cell life-span, and viral generation time. Science 1996; 271: 1582-1586. Seeff LB, Buskell-Bales Z, Wright EC, et al. Long-term mortality after transfusion-associated non-A, non-B hepatitis. The National Heart, Lung, and Blood Institute Study Group. N Engl J Med 1992; 327: 1906-1911. Leveton LB, Sox HC Jr, Stoto MA. HIV and the blood supply: an analysis of crisis decision making. Transfusion 1996; 36: 919-927. Kaldor JM. HTLV-I and blood safety: let the community decide. Med J Aust 1997; 166: 454-455. (Received 14 May 1997, accepted 4 Feb 1998)