Assessment of hepatitis B virus DNA stability in serum by the Chiron Quantiplex branched-DNA assay

Molecular Techniques for Blood and Blood Product Screening

Blood product safety is a high priority for manufacturing industries, hospitals, and regulatory agencies. An important step in ensuring safety is the screening of donated blood for infectious diseases. Molecular technologies for screening infectious diseases have improved remarkably over the years. Molecular biological assay significantly reduced the risk of transfusion-transmitted infections. Unlike previous methods, molecular technologies for screening infectious diseases are specific, efficient, easy to use, and economical. A new era in molecular biology is coming to the field of blood safety.

Molecular Techniques for Blood and Blood Product Screening

The Food and Drug Administration (FDA) is responsible for ensuring the safety of the more than 15 million units of blood and blood components donated each year in the United States. “Blood banking has become a manufacturing industry, an industry that must conform to high standards and quality control requirements comparable to those of pharmaceutical companies or other regulated industries,” said David A. Kessler, MD, former FDA commissioner [1]. Screening donated blood for infectious diseases that can be transmitted through blood transfusion is a very important step in ensuring safety. The United States has the safest blood supply in the world [1] and the FDA is striving to keep it safe by decreasing the risk of infectious disease transmission. The regulatory agency is continuously updating its requirements and standards for collecting and processing blood. As mentioned earlier, an important step in ensuring safety is the screening of donated blood for infectious diseases. In the United States, tests for infectious diseases are routinely conducted on each unit of donated blood, and these tests are designed to comply with regulatory requirements (Table 28.1). The field of clinical microbiology and virology are now focusing on molecular technology. Currently, nucleic acid testing techniques have been developed to screen blood and plasma products for evidence of very recent viral infections that could be missed by conventional serologic tests. It is time for all blood safety procedures to include molecular detection techniques. This approach can significantly aid in blood safety to reduce the risk of transmission of serious disease by transfusion. This chapter reviews the current antigen/antibody-based technology, molecular biological technology, and published regulatory policy data for blood safety.

Short-term stability of pathogen-specific nucleic acid targets in clinical samples

The stability of pathogen-specific DNA or RNA amplification targets in clinical samples following short-term storage at room temperature, 4°C, and -80°C was assessed by real-time PCR. In purified nucleic acid extracts, both DNA and RNA targets were stable for up to 30 days, irrespective of storage temperature. In unextracted samples, temperature-dependent loss of targets (P < 0.05) was observed in serum and cerebrospinal fluid specimens, while no changes were observed for EDTA blood samples.

Evaluation of dual priming oligonucleotide-based multiplex PCR for detection of HBV YMDD mutants

We evaluated the usefulness of dual priming oligonucleotide (DPO)-based multiplex PCR, Seeplex HBV Lami-DR assay (Seegene Institute of Life Sciences, Seoul, Korea), to detect lamivudine-resistant HBV mutants in a comparison with the use of TRUGENE HBV genotyping and restriction fragment mass polymorphism (RFMP). Sera from 44 chronic hepatitis B patients were analyzed for the presence of mutations at codons 180 and 204 by performing DPO-based multiplex PCR, RFMP, and TRUGENE. The overall concordance rate among the three assays was 40.9% (18/44). Concordance rates between multiplex PCR and RFMP or multiplex PCR and TRUGENE were 61.4% (27/44) and 50.0% (22/44), respectively. In ten patients, multiplex PCR identified additional mutants not found using the other two methods. DPO-based multiplex PCR is a highly sensitive method to identify minor mutant populations and could be a practical tool in the monitoring of lamivudine resistance.

Molecular methods used in clinical laboratory: prospects and pitfalls

The role of molecular detection, identification and typing or fingerprinting of microorganisms has shifted gradually from the academic world to the routine diagnostic laboratory. Molecular methods have been used increasingly over the past decade to improve the sensitivity, specificity and turn-around time in the clinical laboratory. Molecular methods have also been used to identify new and nonculturable agents. Many high-throughput molecular tests are now available commercially, which impacts on the infrastructure in many of the diagnostic laboratories. In this paper, we take an overall look at the use of molecular methods (prospects vs. pitfalls) based on our clinical and public health experience, particularly as they related to Borrelia burgdorferi, a vector-borne pathogen, Treponema pallidum, a re-emerging sexually transmitted global pathogen, and West Nile virus, a newly recognized virus in North America.

Comparison of Mass Spectrometric Analysis and TRUGENE™ HBV Genotyping for Monitoring Lamivudine Resistance in Chronic Hepatitis B Patients

Background

There is an increasing need for the early detection of emerging mutations in the tyrosine-methionine-aspartate-aspartate (YMDD) motif of hepatitis B virus (HBV) DNA polymerase with using sensitive molecular methods.

Methods

We evaluated the usefulness of monitoring lamivudine resistance using a matrix-assisted laser desorption/ionization time-of-flight mass spectrometry-based assay (the restriction fragment mass polymorphism; RFMP) in comparison with the direct sequencing assay, the TRUGENE™ HBV genotyping kit. We also investigated the treatment responses in relation to the presence of YMDD mutants. The sera from 50 chronic HBVs patients were analysed for the presence of YMDD mutants by performing RFMP and TRUGENE. The results at codons 180 and 204 were compared for 46 patients.

Results

The concordance rate between the two assays was 65.2% (30/46). All the discordance corresponded to the detection of additional virus populations by RFMP. Early detection of mutants before viral breakthrough was accomplished by RFMP in two patients. Persistence of very low viraemia was observed in five patients who harboured mutant virus populations. Additional information was provided by TRUGENE in eight patients.

Conclusions

RFMP showed a superior ability for detecting minor mutant virus populations compared with TRUGENE. However, the results of highly sensitive RFMP should be interpreted carefully because lamivudine could be effective despite the presence of mutants. RFMP could be a practical tool in conjuction with regular measurements of the HBV viral load for the early detection of lamivudine resistance and the timely introduction of new antiviral drugs.

Natural history of patients with recurrent chronic hepatitis C virus and occult hepatitis B co-infection after liver transplantation

It is uncertain whether occult hepatitis B virus co-infection will hasten progressive liver disease in chronic hepatitis C patients after liver transplantation. This study evaluated fibrosis progression and severe fibrosis in 118 consecutive hepatitis B surface antigen-negative patients with virological and histological evidence of recurrent chronic hepatitis C infection co-infected with occult hepatitis B virus after liver transplantation. HBV DNA was detected from serum at the time of recurrent chronic hepatitis C infection by polymerase chain reaction. Each subject underwent a repeat liver biopsy 5 years post-liver transplantation. Occult hepatitis B virus co-infection was present in 41 of the 118 (34.7%) patients. At 5 years post-liver transplantation, 13 of the 41 occult hepatitis B virus co-infected patients compared with 16 of the 77 patients without occult hepatitis B virus co-infection developed fibrosis progression (31.7% vs. 20.8%, respectively, p = 0.39). Eight of 41 the occult hepatitis B virus co-infected patients compared with 13 of the 77 patients without occult hepatitis B virus co-infection had severe fibrosis (19.5% vs. 16.9%, respectively, p = 0.97). In conclusion, occult hepatitis B virus co-infection in patients with recurrent chronic hepatitis C infection was not associated with accelerated fibrosis progression or severe fibrosis after liver transplantation.

Molecular Techniques for Blood and Blood Product Screening

“Blood banking has become a manufacturing industry, an industry that must conform to high standards and quality control requirements comparable to those of pharmaceutical companies or other regulated industries,” said David A. Kessler, M.D., former FDA commissioner (Revelle, 1995). Screening donated blood for infectious diseases that can be transmitted through blood transfusion is very important in ensuring safety. The United States has the safest blood supply in the world (Revelle, 1995), and the Food and Drug Administration (FDA) is striving to keep it safe by decreasing the risk of infectious disease transmission. The regulatory agency is continuously updating its requirements and standards for collecting and processing blood. An important step in ensuring safety is the screening of donated blood for infectious diseases. In the United States, tests for infectious diseases are routinely conducted on each unit of donated blood, and these tests are designed to comply with regulatory requirements (Table 21.1). The field of clinical microbiology and virology is now moving into the focus of molecular technology. Currently, nucleic acid testing techniques have been developed to screen blood and plasma products for evidence of very recent viral infections that could be missed by conventional serologic tests. It is time for all blood safety staffs to use molecular detection techniques. This approach can significantly aid in blood safety to reduce the risk of transmission of serious disease by transfusion. This chapter will review the current antigen/antibody–based technology, molecular biological technology, and published regulatory policy data for blood safety.

Fibrosis progression in chronic hepatitis C patients with occult hepatitis B co-infection

Occult hepatitis B virus (HBV) infection in individuals without hepatitis B surface antigen (HBsAg) can be identified in hepatitis C virus (HCV) infected patients. However, its role in fibrosis progression remains uncertain. This retrospective study compared the fibrosis progression (defined as fibrosis progression by at least one stage) and progression to severe fibrosis (fibrosis stage 3 or 4) in HCV patients with occult HBV infection. Occult HBV infection was diagnosed by the detection of HBV DNA in the serum of 74 consecutive anti-HCV positive patients by PCR. Thirty-one patients (41.9%) had occult HBV infection. All 74 patients had a median of 2 (range 2-3) liver biopsies. The median time between the first and last liver biopsy was 57.7 (range 15.0-132.8) months. Eleven of the 31 patients with occult HBV infection compared with 12 of the 43 patients without occult HBV infection had fibrosis progression (35.5% versus 27.9%, respectively, p=0.608). Six of the 31 patients with occult HBV infection compared with 8 of the 43 patients without occult HBV infection developed severe fibrosis (19.4% versus 18.6%, respectively, p=0.946). In conclusion, chronic HCV patients with occult HBV co-infection does not seem to progress more than patients without occult HBV infection. However, more large-scale studies are needed before a definite conclusion can be obtained.

Is there recent progress in the estimation of the postmortem interval by means of thanatochemistry?

Numerous methods have been proposed in the last 60 years for the determination of the time since death by chemical means. Many of them were reviewed by Schleyer in his monograph on the determination of the time since death by means of thanatochemistry about 40 years ago and none of these early methods has gained any practical value since they do not meet the demands in practice (being precise, reliable, giving an immediate result). While the earlier studies were mainly carried out on blood and cerebrospinal fluid (CSF) since the late 60s most investigations have been performed on vitreous humor (VH). This is mainly due to the fact that vitreous humor is topographically isolated and well protected, and thus, autolytic changes proceed slower compared to blood and CSF. The most studied parameter in VH is potassium and even nowadays reports on the postmortem rise of vitreous potassium are published, proposing new analytical methods or statistical evaluations. Chemical parameters studied for the determination of the time since death have to be differentiated according to the underlying process (catabolism, metabolic processes, pure autolysis and diffusion, putrefactive changes). In the present paper, recent studies on thanatochemistry are discussed regarding the underlying process, the analytical methods (for instance H magnetic resonance spectroscopy (1H MR spectroscopy), immunohistochemistry), the studied fluid compartment, the statistical evaluation and the precision of death time estimation. The value of chemical methods for the determination of the time since death is up to now very limited. This is supported by the fact that field studies on the reliability and precision of death time estimation by chemical means are still scarce in the literature.

The laboratory diagnosis of hepatitis B virus

Hepatitis B virus (HBV) chronically infects approximately 250,000 Canadians and 350 million people worldwide. Without intervention, approximately 15% to 40% of chronically infected individuals will eventually develop cirrhosis, end-stage liver disease or hepatocellular carcinoma, or require liver transplantation. The availability and extensive use of the HBV vaccine has dramatically reduced the number of incident infections in Canada and worldwide. Effective therapeutic agents have been and continue to be developed to treat chronic infection. The present review provides a comprehensive overview of diagnostic tests for HBV infection and immunity, and elaborates on HBV risk factors, vaccine prevention and therapeutic monitoring. HBV diagnosis is accomplished by testing for a series of serological markers of HBV and by additional testing to exclude alternative etiological agents such as hepatitis A and C viruses. Serological tests are used to distinguish acute, self-limited infections from chronic HBV infections and to monitor vaccine-induced immunity. Nucleic acid testing for HBV-DNA is increasingly being used to quantify HBV viral load and measure the effectiveness of therapeutic agents. Given the multitude of available tests and the complexity of clinical management, there is a critical need for greater coordination among clinicians, diagnostic laboratory personnel and researchers to define optimal laboratory diagnostic and monitoring assays so that the appropriate tests are used to maximize prevention and optimize treatment outcomes.

Serum hepatitis B DNA: stability in relation to multiple freeze-thaw procedures

Quantitation of hepatitis B virus (HBV) DNA is often performed in specimens that have been frozen and thawed more than once. It is important to establish whether viral load measurements are affected by repeated freeze-thaw cycles. The effect of multiple freeze-thaw cycles on HBV DNA quantitation was carried out by testing serum specimens subjected to 1 (baseline) to 10 cycles with the appropriate Digene Hybrid Capture System. Five HBV DNA-positive samples were selected at random from sera with concentrations ranging from 7 pg/ml to 3529 pg/ml and they were frozen and thawed up to 10 cycles and then tested for changes in HBV DNA levels. Negative control and positive standards were tested in triplicate; and all specimens were tested in duplicate. The stability of HBV DNA in serum was evaluated by scattergram analysis by determining the number of samples showing a > or =20% change in HBV DNA levels after freeze-thaw cycles. With the exception of one sample (7 pg/ml) 10 cycles of freezing and thawing did not change significantly the HBV DNA quantity in any of the samples tested. The results showed that the quantity of HBV DNA in four of five serum specimens subjected up to 10 freeze-thaw cycles was stable.

Biological qualification of blood units: considerations about the effects of sample's handling and storage on stability of nucleic acids

BACKGROUND

In transfusional setting introduction of nucleic amplification technique (NAT) for HBV-DNA, HCV-RNA and HIV-RNA in biological qualification of blood units suggest some problems. At first the opportunity to operate on mini-pool, at second the need to store the samples at +4 degrees C. The authors therefore have tried to estimate the impact of these conditions on the operativity of NAT testing in the transfusional setting.

METHODS

The following parameters has been estimated: distribution of viral-load in untreated subjects, stability of nucleic acids during storage at +4 degrees C, stability of nucleic acids after repeated cycles of freezing and defrosting, robustness of the test to the cross-contamination, definition of the detection-limit (95%). Quantitative tests has been performed by using the following kits: Cobas Amplicor HBV Monitor, Cobas Amplicor HCV Monitor, Cobas Amplicor HIV Monitor; the qualitative tests has been performed by using the following kits: Ampliscreen HBV, Ampliscreen HCV 2,0, Ampliscreen HIV 1,5 all supplied by Roche Molecular System (Brancburg, NJ).

RESULTS

Viral load in untreated subjects showed wide variation for HBV, HCV and HIV. HBV has been demonstrated much stable to the conservation +4 degrees C also until 168 h while for HCV and HIV a greater decrease of the viral-load was observed. For all and three virus the conservation to +4 degrees C until 72 h does not seem to involve meaningful fall in the viral-load. A remarkable reduction of the viral-load has been observed after five cycles of freezing and defrosting. All the tests showed a good robustness to cross-contamination. The detection-limit (95%) was 8 U/ml for HBV, 21 U/ml for HCV and 27 copy/ml for HIV.

CONCLUSIONS

Samples for NAT testing, can be stored until 72 h to +4 degrees C without appreciable lowering of the viral-load. Repeated cycles of changes of state should be avoided. The tests showed a good robustness to cross-contamination. NAT tests for biological qualification of blood units had a minimal sensibility around 50 (copy/unit/ml). In our experience the detection-limit (95%) was 21 U/ml for HCV, 27 copies/ml for HIV, 8 U/ml for HBV. The availability of NAT test for HBV-DNA, HCV-RNA e HIV-RNA, sensitive and reliable, together with epidemiological data, suggest the opportunity to place side by side, in the biological qualification of the blood units, to add the tests for HBV-DNA and HIV-RNA to the test for HCV-RNA mandatory by low, in Italy in the biological qualification of blood units.

Reduction of double-stranded RNA-activated protein kinase in hepatocellular carcinoma associated with hepatitis B virus

Chronic hepatitis B virus (HBV) infection is a major cause of hepatocellular carcinoma (HCC) in Asia. Double-stranded RNA (dsRNA)-activated protein kinase (PKR) is an interferon-induced, serine/threonine protein kinase. Recent studies have suggested that PKR is involved in the pathogenesis of HCC with hepatitis virus C infection by inhibiting viral and cellular proteins related to cell growth and proliferation. In the present study, PKR was examined in both tumor and non-tumor tissues from HCC livers infected with HBV. The expression of PKR was determined by TaqMan real-time PCR and immunohistochemical methods. The level of PKR was also analyzed in relation to pathological changes observed in HCC. The result showed that PKR was reduced in tumor tissues of HCC from HBV carriers with low serum viral load (<0.7 x 10(6) copies/ml) compared to those with higher serum viral load. However, the overall PKR level was much lower in tumor tissues than that in non-tumor tissues, irrespective of HBV carrier status or serum viral load. PKR level tended to be lower in HCC samples with alpha-fetoprotein (AFP) more than 500 ng/ml (mean: 4024.2 ng/ml) than those with AFP less than 500 ng/ml (mean: 50.6 ng/ml). There was no significant difference in the expression of PKR between tumor tissues with well differentiation and those with poor or moderate differentiation. In conclusion, the level of PKR was reduced in HCC tumor tissues, suggesting a possible role of PKR in promoting the growth of tumor. HBV may participate in altering the level of PKR, but factors other than HBV should play a more determining role in the regulation of PKR in HCC. The association between PKR and AFP levels may offer an alternative tumor marker for HCC.

Blood-borne viruses and their survival in the environment: is public concern about community needlestick exposures justified?

BACKGROUND

More than 30 million needle syringes are distributed per year in Australia as a component of harm-reduction strategies for injecting drug users (IDU). Discarded needle syringes create considerable anxiety within the community, but the extent of needlestick injuries and level of blood-borne virus transmission risk is unclear. We have undertaken a review of studies of blood-borne virus survival as the basis for advice and management of community needlestick injuries.

METHODS

A Medline review of published articles on blood-borne virus survival and outcome from community injuries.

RESULTS

Hepatitis B virus (HBV), hepatitis C virus (HCV) and human immunodeficiency virus (HIV) can all survive outside the human body for several weeks, with virus survival influenced by virus titer, volume of blood, ambient temperature, exposure to sunlight and humidity. HBV has the highest virus titers in untreated individuals and is viable for the most prolonged periods in needle syringes stored at room temperature. However, prevalence of HBV and HIV are only 1-2% within the Australian IDU population. In contrast, prevalence of HCV is 50-60% among Australian IDUs and virus survival in needle syringes has been documented for prolonged periods. There have been no published cases of blood-borne virus transmission following community needlestick injury in Australia.

CONCLUSION

The risk of blood-borne virus transmission from syringes discarded in community settings appears to be very low. Despite this, procedures to systematically follow up individuals following significant needlestick exposures sustained in the community setting should be developed.

Clinical evaluation of the COBAS Amplicor HBV monitor test for measuring serum HBV DNA and comparison with the Quantiplex branched DNA signal amplification assay in Taiwan

AIMS

To evaluate the performance characteristics and clinical usefulness of the COBAS Amplicor HBV monitor (COBAS-AM) test in Taiwan and to examine its correlation with the Quantiplex branched DNA signal amplification (bDNA) assay for measuring serum hepatitis B virus (HBV) DNA concentrations.

METHODS

HBV DNA was measured by the COBAS-AM test in 149 sera from chronic HBV infected patients that had previously been analysed by the bDNA assay.

RESULTS

The COBAS-AM test showed good reproducibility, with acceptable intra-assay and interassay coefficients of variation (1.6% and 0.9%, respectively) and good linearity (r2=0.98). The overall sensitivity of the COBAS-AM test was significantly higher than that of the bDNA assay (95.3% v 83.2%): 69.6% of samples with HBV DNA below the detection limit of the bDNA assay could be measured by the COBAS-AM test. There was a significant correlation between the results of the two assays (r=0.901; p<0.0001). On average, the results derived from the COBAS-AM test were 0.55 log lower than those of the bDNA assay. HBV DNA concentrations were significantly higher among HBV e antigen (HBeAg) positive patients than negative ones, and higher among patients with abnormal alanine aminotransferase (ALT) concentrations than those with normal ALT concentrations (p=0.0003).

CONCLUSIONS

The COBAS-AM assay, more sensitive in HBeAg negative samples than the bDNA assay, can effectively measure HBV DNA concentrations in Taiwanese patients. HBV DNA values measured by the COBAS-AM test and bDNA assay correlate significantly.

Limitations and improvements of the quantiplex branched-DNA assay in Hepatitis B virus-infected patients receiving lamivudine

The branched DNA (bDNA) assay for hepatitis B virus (Chiron Corporation Emerville, USA) was investigated by application to HBV-infected patients in Taiwan, where the B and C genotypes of hepatitis B virus are most prevalent. The study group included sera with hepatitis B surface antigen (HBsAg) and e antigen (HBeAg); Group 1 (n=70) without treatment; Group 2 (n=28) lamivudine treatment less than 3 months; Group 3 (n=73) lamivudine treatment 3-12 months; Group 4 (n=45) HBeAg-negative sera after 1 year treatment with lamivudine; control group (n=36) HBsAg-negative sera. Comparison of identical-sample results showed a significantly higher coefficient of variation for low-level HBV DNA (<100 MEq/ml) than for high-level (> or =100 MEq/ml), indicating increasing assay inaccuracy uncertainty as the sample HBV DNA concentration decreased. It is thus concluded that low-titered sera should receive special careful pipetting and processing. It was also found that using the relative luminescence of the negative control plus two standard deviations (S.D.) as a new cutoff could promote sensitivity (97.1-->97.1%, 89.3-->100%, 76.7-->84.9%, and 17.8-->22.2% in Groups 1-4, respectively) and specificity (94.4-->97.2%). In summary, the bDNA HBV assay showed only moderate assay performance for samples with low HBV DNA levels. This problem can be improved partially by choosing a new cutoff value based on the relative luminescence of the negative controls in the kit.

Effect of multiple freeze-thaw cycles on hepatitis B virus DNA and hepatitis C virus RNA quantification as measured with branched-DNA technology

Quantification of hepatitis B virus (HBV) DNA and hepatitis C virus (HCV) RNA often is performed in specimens that have been frozen and thawed more than once. To ensure optimal therapeutic and prognostic value, it is important to establish whether viral load measurements are affected by repeated freeze-thaw (FT) cycles. We therefore evaluated the effect of multiple FT cycles on HBV DNA and HCV RNA quantification by testing serum specimens subjected to one (baseline), two, four, and eight FT cycles with the appropriate Chiron Quantiplex assay. Linear regression analysis showed minor increases of 1.7% per FT cycle for both HBV DNA and HCV RNA. The rise in HCV RNA levels was more pronounced among low-concentration samples, since further analysis revealed an increase of 3.2% per FT cycle among samples with 0.2 to 3.86 Meq of HCV RNA per ml. Given that the coefficient of variation for the Quantiplex assays is generally 10 to 15%, the minor increases in HBV DNA and HCV RNA levels with progressive FT cycles for the specimens tested were recognized only because analysis of variance revealed a statistically significant trend (P < 0.05). Due to the minor statistical trend, the clinical impact for individual patient specimens is likely to be limited, but it may deserve further study. In conclusion, the concentration of HBV DNA and HCV RNA in serum specimens subjected to up to eight short-term FT cycles was stable.