Detection of hepatitis B virus sequences in serum by using in vitro enzymatic amplification

Nitrocellulose-bound achromopeptidase for point-of-care nucleic acid tests

Enzymes are the cornerstone of modern biotechnology. Achromopeptidase (ACP) is a well-known enzyme that hydrolyzes a number of proteins, notably proteins on the surface of Gram-positive bacteria. It is therefore used for sample preparation in nucleic acid tests. However, ACP inhibits DNA amplification which makes its integration difficult. Heat is commonly used to inactivate ACP, but it can be challenging to integrate heating into point-of-care devices. Here, we use recombinase polymerase amplification (RPA) together with ACP, and show that when ACP is immobilized on nitrocellulose paper, it retains its enzymatic function and can easily and rapidly be activated using agitation. The nitrocellulose-bound ACP does, however, not leak into the solution, preventing the need for deactivation through heat or by other means. Nitrocellulose-bound ACP thus opens new possibilities for paper-based Point-of-Care (POC) devices.

Design, implementation, and interpretation of amplification studies for prion detection

Amplification assays for transmissible spongiform encephalopathies have been in development for close to 15 years, with critical implications for the postmortem and antemortem diagnosis of human and animal prion diseases. Little has been published regarding the structured development, implementation and interpretation of experiments making use of protein misfolding cyclic amplification (PMCA) and real time quaking-induced conversion (RT-QuIC), and our goal with this Perspectives manuscript is to offer a framework which might allow for more efficient expansion of pilot studies into diagnostic trials in both human and animal subjects. This framework is made up of approaches common to diagnostic medicine, including a thorough understanding of analytical and diagnostic sensitivity and specificity, an a priori development of amplification strategy, and an effective experimental design. It is our hope that a structured framework for prion amplification assays will benefit not only experiments seeking to sensitively detect naturally-occurring cases of prion diseases and describe the pathogenesis of TSEs, but ultimately assist with future endeavors seeking to use these methods more broadly for other protein misfolding disorders, including Alzheimer's and Parkinson's disease.

Changing prevalence of hepatitis B virus genotypes in Iceland

At present eight hepatitis B virus (HBV) genotypes have been characterized: A to H. The most common genotype in Northern Europe is genotype A. So far there is no record of the specific HBV genotype distribution in Iceland. Iceland has a small population whose homogeneity has changed due to increasing migration during the past decades. The distribution of HBV genotypes in Iceland was analyzed using sera from 170 Icelandic patients. The samples were obtained before 1989, during an HBV epidemic among intravenous drug users in 1989 to 1992 and after 1994. A fragment of the HBV S-gene was amplified, sequenced and subjected to phylogenetic analysis. Among samples derived before 1989 genotypes A, C, and D were found. Most of the samples diagnosed during the epidemic belonged to genotype D and a smaller portion to genotype A. This suggests that the epidemic was most likely caused either by an endogenous HBV strain or by a strain imported from Europe or the USA. Among samples obtained after 1994, genotypes A to E and G were found, but the majority were of genotypes A, C, and D. This is consistent with an increase in migration and immigration from regions in Asia and Africa during the past 10 years. Thus, the changing prevalence of HBV genotypes in a small isolated community such as Iceland reflects the influence of migration and increasing contacts with regions outside the Western World.

Role of polymerase chain reaction and liver biopsy in the evaluation of patients with asymptomatic transaminitis: implications in diagnostic approach

BACKGROUND AND AIM

Detection of an asymptomatic rise in the hepatic aminotransferase (ARHA) value has become a distinct and frequent clinical problem. We evaluated a three-step diagnostic algorithm in such patients for maximum yield.

METHODS

Consecutive patients with an ARHA value 1.5-fold the upper limit of normal for at least 4 weeks and who were apparently healthy were included in the study. Each patient underwent standard biochemical investigations and a stepwise investigative protocol. In the first step, serological markers for hepatitis viruses, serum ferritin, 24-h urinary copper, alpha-1-antitrypsin phenotyping, and autoimmune markers were carried out. In step two, patients who tested negative for all the above markers had polymerase chain reaction (PCR) analysis for hepatitis B virus (HBV)-DNA and hepatitis C virus (HCV)-RNA. Patients without a diagnosis despite the above investigations underwent a liver biopsy as part of step three.

RESULTS

Of 105 patients with ARHA, 38 were excluded for various reasons and 67 were included for the final analysis. The mean age was 35.11 +/- 11.96 years and 56 patients were men. The mean body mass index was 24.17 +/- 3.2 kg/m(2). The stepwise diagnostic algorithm achieved a diagnosis in 65/67 (97%) patients. Non-alcoholic steatohepatitis (NASH) and chronic viral hepatitis were the most common diagnoses, in 24 (36%) patients each. Using the diagnostic algorithm a diagnosis was reached in 34% of patients with only serological and biochemical investigations, whereas PCR for HBV and HCV could further detect the presence of active HBV or HCV viremia in 21% (14/97) and a liver biopsy was necessary to establish the diagnosis in 28/67 (42%) patients.

CONCLUSIONS

A stepwise diagnostic algorithm in patients with ARHA resulted in an optimal use of PCR and invasive tests such as liver biopsy. Cryptic HBV and HCV infection was frequent among these patients and PCR was necessary in such cases. NASH and chronic viral hepatitis were the most frequent causes of ARHA.

Occult hepatitis B virus infection in chronic liver disease: full-length genome and analysis of mutant surface promoter

BACKGROUND AND AIMS

Genome sequence of hepatitis B virus (HBV) from occult chronic infection is scarce. Fifty-six (9.4%) of 591 patients seronegative for hepatitis B surface antigen (HBsAg) with chronic liver disease were positive for HBV DNA. The complete HBV genome from 9 of these patients (S1-S9) and 5 controls positive for HBsAg (SWT.1-SWT.5) were analyzed.

METHODS

Overlapping genome fragment amplification, cloning, and sequencing was performed on these cases. Functional analysis of surface promoter was conducted using fusion construct.

RESULTS

All patients with occult infection except one (S8) had a low viral titer. Eight patients had infection with genotype A (S1-S5, SWT.1-2, SWT.5) and 6 had infection with genotype D (S6-S9, SWT.3-4). S4 and S5.1 of genotype A had the characteristic nucleotide deletions in core and pre-S1 region seen in genotype D. The major observations in patients with occult HBV infection were as follows: frequent quasispecies variation, deletions in pre-S2/S region affecting the surface promoters (nt 3025-54) and pre-S protein (S3, S5, S6, S8), truncated precore (S6, S8, S7.1) and core (S9) owing to stop signal, alternate start codon for the Polymerase gene (S3, S9), and YMDD mutation (S1, S4, S9) in patients not on antiviral therapy. HBsAg and core proteins could be shown immunohistochemically in 3 of 5 liver biopsy specimens available. The mutant surface promoters (pre-S2 and S) on functional analysis showed alterations in HBsAg expression.

CONCLUSIONS

These changes in the regulatory region with possible alterations in the ratio of large and small surface proteins along with other mutations in the genome may decrease the circulating HBsAg level synergistically, making the immunodetection in serum negative.

Evaluation of serologic screening of blood donors in India reveals a lack of correlation between anti-HBc titer and PCR-amplified HBV DNA

BACKGROUND

Transfusion associated-HBV (TAHBV) is estimated at approximately 1.5 percent in postsurgical recipients and 50 percent or more in multiple-transfusion recipients in India. Not transfusing blood with high-titer anti-HBc, which reportedly correlates with the presence of HBV DNA, helped reduce TAHBV in Japan. This study tested anti-HBc-reactive donors for PCR-amplified HBV DNA and its correlation with anti-HBc titers.

STUDY DESIGN AND METHODS

In total, 30,853 donors from Cohort 1 (24,694 in 2001) and Cohort 2 (6159 in 2000) were screened for anti-HBc and anti-HBs. Amplification of HBV DNA was performed on an unselected subset of 147 out of 3304 anti-HBc-only sera from Cohort 1 and 230 out of 6159 from Cohort 2. Correlation of anti-HBc titers in DNA positive (n = 48), DNA negative (n = 40), anti-HBs reactive (n = 44), and HBsAg reactive (n = 45) donors was by Fisher's exact test.

RESULTS

In Cohort 1, 2673 (10.82%) donors were reactive for anti-HBc, of whom 1038 (4.20%) were anti-HBc only. HBV DNA was detected in 40 out of 147 (27.21%) and 48 out of 230 (20.87%) donors with anti-HBc only from the two cohorts. Anti-HBc titers detected no significant difference between the first three groups.

CONCLUSION

Cryptic HBV infection was observed in approximately 25 percent of anti-HBc-only donors. No correlation was established between HBc titers and presence of HBV DNA.

Investigation of alcohol metabolizing enzyme genes in Chinese alcoholics with avascular necrosis of hip joint, pancreatitis and cirrhosis of the liver

AIMS AND METHODS

Alcoholism may cause a range of diseases including avascular necrosis of the hip joint (AVN), cirrhosis of the liver, pancreatitis and oesophageal carcinoma. Chinese alcoholic patients diagnosed with AVN have a higher incidence of cirrhosis than of acute pancreatitis or oesophageal cancer. Thus, the aim of this study was to investigate genetic differences in polymorphisms of the alcohol-metabolizing enzymes ADH2, ADH3, ALDH2 and P4502E1 for subgroups of Chinese alcoholic patients, defined by diagnoses of AVN (n = 51), acute pancreatitis (n = 92) and liver cirrhosis (n = 159), and for 280 non-alcoholic patients.

RESULTS

Analysis revealed that ADH2*1 allele frequency was significantly lower for the alcoholic AVN than for the cirrhosis subgroup. However, no significant difference was found between the alcoholic AVN and pancreatitis subgroups. Furthermore, ALDH2*2 prevalence was not found to differ significantly between the alcoholic subgroups. When compared with our previously published data for alcoholic patients with oesophageal carcinoma, ADH2*1 carriage was significantly less frequent for the alcoholic AVN patients in the current study. Further, ALDH2*2 carriage was significantly less frequent for the alcoholic AVN subgroup than for the oesophageal carcinoma patients.

CONCLUSIONS

The allele frequencies for ADH2*1 and ALDH2*2 are different when comparing subpopulations of alcoholics defined by presence of specific alcohol-induced diseases, suggesting that genetic variation in alcohol-metabolizing enzyme genes accounts for, at least in part, the specific types of organ damage observed. We also found the combination of AVN and cirrhosis to be more prevalent than that of AVN and acute pancreatitis. In contrast, the ADH2 and ALDH2 allele frequencies for the AVN subgroup were more similar to those of the acute-pancreatitis than to the cirrhosis subgroup. These data indicate the possibility that other genetic variations may also influence the type of organ-specific complications in Chinese alcoholics.

Selective detection of individual DNA molecules by capillary polymerase chain reaction

On-line capillary polymerase chain reaction (PCR) coupled with laser-induced fluorescence detection was successfully demonstrated for individual DNA molecules. A single 30-microm-i.d. fused-silica capillary was used both as the reaction vessel and for isolating single molecules. SYBR green I dye was added into the reaction mixture for dynamic fluorescent labeling. Because of the small inside diameter of the capillary, PCR-amplified DNA fragments from single molecules were localized in the capillary, providing discrete product zones with concentrations at readily detectable levels. By counting the number of peaks in the capillary via electromigration past a detection window, the number of starting DNA molecules could be determined. With selective primer design, only the molecule of interest was detected. Amplification of the 110-bp fragment from an individual human beta-globin gene and the 142-bp fragment from an individual HIV-1 DNA was demonstrated. This opens the possibility of highly selective and sensitive disease diagnosis at a very early stage.

Hepatitis B virions isolated with antibodies to the pre-S1 domain reveal occult viremia by PCR in Alaska Native HBV carriers who have seroconverted

BACKGROUND

Occult viremia occurring before the appearance of HBsAg or after the disappearance of HBsAg is detectable by gene amplification technologies whose efficiency depends on nucleic acid preparation.

STUDY DESIGN AND METHODS

To isolate HBV DNA from viremic plasma, immunoaffinity capture (IAC) of intact HBV with biotinylated pre-S1 antibodies coupled to streptavidin-coated magnetic beads was evaluated. IAC was compared with a silica-gel method (Qiagen [QSG]) and its two modifications wherein the samples were heated with lysis buffer at 60(o)C for 10 minutes (QSG-60) or at 58 degrees C for 60 minutes with proteinase-K (QSG-PK). Each HBV DNA sample was tested by heminested PCR amplification of the HBV gene sequences. A total of 36 coded serum samples were tested, including three HBsAg-positive controls and 33 former chronic HBV carriers who had seroconverted (developed antibody to HBsAg [anti-HBs]). Commercially available seroconversion panels (PHM 907, 911, and 922) were similarly tested for window-period viremia.

RESULTS

In the 33 former chronic HBV carriers who had seroconverted, IAC revealed HBV DNA in 17 samples, whereas it was revealed in only 11 samples by QSG-PK (p = 0.031), 10 by QSG-60 (p = 0.016), and 9 by QSG (p = 0.0078). However, HBV DNA was not amplified from the 17 samples at 1-in-10 dilutions; thus, they were considered to have low-level viremia. IAC revealed HBV DNA as early as or earlier than the other methods in PHM 907, 911, and 922 panels.

CONCLUSION

IAC is apparently an optimal method of sample preparation for amplification of HBV DNA in patients in the pre-HBsAg window period, and for detecting low-level viremia persistent in several individuals who were former chronic HBV carriers who had seroconverted (developed anti-HBs).

Elevation of TFF1 gene expression during healing of gastric ulcer at non-ulcerated sites in the stomach: semiquantification using the single tube method of polymerase chain reaction

BACKGROUND

The Trefoil factor family 1 (TFF1), one of the trefoil peptides, has been considered to play protective and reparative roles of experimentally induced ulcers in the stomach. However, the alteration of the TFF1 mRNA in the non-ulcerated areas of living human gastric mucosa in gastric ulcer is not well known. We examined TFF1 gene expression at non-ulcerated sites during the healing of a gastric ulcer by semiquantitative determination of the TFF1 mRNA.

METHODS

Gastric mucosal biopsy specimens were taken before and after the healing of the gastric ulcer from seven consecutive patients and from seven patients diagnosed with non-ulcer dyspepsia (NUD). The relative value of TFF1 mRNA (RTFF1) was calculated by the single tube method of polymerase chain reaction (ST-PCR) and Southern hybridization. Immunohistochemistry using monoclonal antibodies was performed to confirm the presence of the TFF1 peptide. The status of Helicobacter pylori and the severity of gastritis were investigated simultaneously.

RESULTS

The mean relative values of TFF1 mRNA at both the gastric angle (RTFF1AS) and the gastric body (RTFF1BS) of patients with gastric ulcers at the healed stage were significantly higher than those at the open stage (P< 0.05). The mean RTFF1AS at both the open and healed stages were lower than those of RTFF1BS at the open and healed stages, respectively, The mean RTFF1B at the open stage was lower than that in NUD (not significant), but the mean of RTFF1B at the healed stage was significantly higher than that in NUD. The RTFF1AS and RTFF1BS of all patients did not correlate with H. pylori status nor with the severity of gastritis. The induction of TFF1 mRNA at the non-ulcerated background sites seemed not to be related to the status of H. pylori or to the severity of gastritis.

CONCLUSIONS

These results suggest that the increased levels TFF1 mRNA during the healing of gastric ulcers might be closely related to the protection and the cell differentiation at the non-ulcerated areas of living human gastric mucosa.

Quantitation of porcine cytokine and beta 2-microglobulin mRNA expression by reverse transcription polymerase chain reaction

A quantitative reverse transcription polymerase chain reaction (Q-RT-PCR) method was developed to measure pig cytokine mRNA expression. The method utilized an internal control with primer sequences for interleukin (IL)-1alpha, 2, 4, 6, 8, 10, tumor necrosis factor (TNF)-alpha, TNF-beta, interferon (IFN)-gamma and beta-2 microglobulin (beta(2)-m). The control was modified by insertion of sequences for IL-12 (p35 and p40). Pig blood mononuclear cells (BMCs) were stimulated in vitro with phytohemagglutinin-P (PHA-P) or bacterial lipopolysaccharide and cytokine or beta(2)-m mRNA quantified. To evaluate method performance and the use of beta(2)-m as a housekeeping gene (HKG), beta(2)-m mRNA expression was examined. Quantitative analysis was achieved at up to threefold differences between control and target for beta(2)-m. Results were reproducible with coefficients of variations (CVs) ranging between 12.5% and 22.4%. There were no significant differences in beta(2)-m mRNA between treated and untreated cells or between untreated cells of three pigs (p>/=0.05) suggesting that beta(2)-m can be used as a HKG. The method allows quantitation of multiple cytokine mRNAs using a single internal control subjecting target and control to the same conditions throughout the Q-RT-PCR. The system is versatile since the control plasmid can be modified by insertion or deletion of sequences.

Post-transfusion hepatitis type B following multiple transfusions of HBsAg-negative blood

BACKGROUND/AIMS

Post-transfusion hepatitis continues to occur, though with decreasing frequency, even after screening donor blood for HBsAg, anti-HBc, anti-HCV and alanine aminotransferase activity. Data from developing countries on the frequency and type of post-transfusion hepatitis are scarce. We undertook this prospective study to determine the incidence and type of post-transfusion hepatitis at our center after transfusion of blood negative for HBsAg by ELISA.

METHODS

Forty-one patients undergoing open-heart surgery, who had received 3 or more units of HBsAg-negative blood, were followed up. Serum samples of donor units transfused to recipients who developed post-transfusion hepatitis-B were subjected to HBV DNA amplification by the polymerase chain reaction, using two sets of X-gene specific primers which amplified a 250-bp fragment of the HBV DNA.

RESULTS

We found that six of the 41 patients (14.6%) developed post-transfusion hepatitis; four of them (66.6%) developed icteric post-transfusion hepatitis B, whereas two (33.3%) developed anicteric post-transfusion hepatitis C. These six recipients received a total of 48 units of blood and 30 of these 48 units could be subjected to HBV DNA amplification by polymerase chain reaction. Eleven donor samples were polymerase chain reaction positive and had been transfused to three of the four patients who had developed post-transfusion hepatitis B.

CONCLUSIONS

We conclude that post-transfusion hepatitis B continues to be the most common cause of post-transfusion hepatitis in India. Screening of donor units for HBsAg by ELISA does not exclude all blood units infectious for hepatitis B virus. Additional measures to ensure safety of blood supply should be sought.

Comparison of hepatitis B virus DNA extractions from serum by the QIAamp blood kit, GeneReleaser, and the phenol-chloroform method

The abilities of GeneReleaser and QIAamp to extract the hepatitis B virus (HBV) DNA template from serum for amplification by PCR were evaluated and compared with that of the standard phenol-chloroform method. Differences in the sensitivities of the three methods were revealed by nested PCR of HBV DNA extracted from serially diluted hepatitis B e antigen (HBeAg)-positive (high-titer) serum. Phenol-chloroform was found to be the most sensitive extraction method but was time-consuming and labor intensive, and the many steps required increased the possibility of contamination. In a titration of HBeAg-negative (low-titer) serum, all three methods coupled with nested PCR were capable of detecting low levels of HBV DNA. In the case of QIAamp and GeneReleaser, the extraction was relatively simple and rapid. The higher quantity of serum (200 microliters) used in the QIAamp extraction did not provide higher sensitivity, possibly because of incomplete removal of Taq polymerase inhibitors from the serum or inadequate disruption of the virion. GeneReleaser was more efficient because it gave the same detection limit in low-titer serum as phenol-chloroform even though it utilizes only 5 microliters of serum. However, it did not produce consistent amplifications of HBV DNA, giving false-negative results in 7 of the 50 cases (14%) in one experiment. Use of a larger volume of serum and replicate extractions may overcome this problem. Advantages thus exist in each of the extraction methods, and these should be weighed against the disadvantages when deciding which extraction method is appropriate.

Quantitative molecular methods in virology

During the past few years, significant technical effort was made to develop molecular methods for the absolute quantitation of nucleic acids in biological samples. In virology, semi-quantitative and quantitative techniques of different principle, complexity, and reliability were designed, optimized, and applied in basic and clinical researches. The principal data obtained in successful pilot applications in vivo are reported in this paper and show the real usefulness of these methods to understand more details of the natural history of viral diseases and to monitor specific anti-viral treatments in real time. Theoretical considerations and practical applications indicate that the competitive polymerase chain reaction (cPCR) and competitive reverse-transcription PCR (cRT-PCR) assay systems share several advantages over other quantitative molecular methodologies, thus suggesting that these techniques are the methods of choice for the absolute quantitation of viral nucleic acids present in low amounts in biological samples. Although minor obstacles to a wide use of these quantitative methods in clinical virology still remain, further technical evolution is possible, thus making the quantitative procedures easier and apt to routine applications.

Typing and subtyping of influenza viruses in clinical samples by PCR

Type A and B influenza viruses can cause a wide spectrum of illness, and these viruses are responsible for considerable mortality and morbidity. Rapid typing of isolates is desirable when amantadine treatment or prophylaxis of contacts of type A influenza virus carriers is considered, but the available rapid techniques lack sensitivity and standard diagnostic methods require expansion of virus in tissue culture or embryonated hens' eggs. We developed a series of oligonucleotide primers able to detect, type, and subtype type A influenza viruses in a single reverse transcription-PCR. RNA was isolated from clinical specimens, and cDNA was generated with random primers. PCR was carried out with a mixture of primers specific for influenza viruses of types B, A/H1 and A/H3, and subtyping of the neuraminidase was carried out on the same cDNA template under identical conditions. Amplified products were detected by ethidium bromide staining of amplified products after agarose gel electrophoresis. When it was used to test 98 clinical specimens, this method was comparable to standard culture techniques in the detection, typing, and subtyping of influenza viruses.

Hepatitis B virus precore mutations and HBeAg negative reactivation of chronic hepatitis B after interferon therapy

The objective of this study was to look for HBV precore mutations in three patients with chronic active hepatitis B who developed HBV-DNA-positive/HBeAg-negative reactivation after HBe seroconversion induced by interferon therapy. Direct sequencing of polymerase chain reaction products was performed on serum collected before and after HBe seroconversion. In two patients precore sequence showed only wild-type HBV before and after interferon therapy. In one patient, precore sequence showed only wild-type HBV before interferon therapy and a mixed infection by wild-type HBV and precore mutant viruses (1858 and 1896 nucleotide mutations) after treatment. The presence of HBeAg/anti-HBe immune complexes was found after HBe seroconversion in all cases. Our results suggest that: 1) precore mutations are not always found in patients with chronic hepatitis B who develop HBV DNA-positive/HBeAg-negative reactivation; and 2) HBeAg negativity, despite the presence of wild-type HBV, might be due to HBeAg/anti-HBe immune complexes. We speculate that the production of these immune complexes may be favored by interferon therapy.

Evaluation of SHARP signal system for enzymatic detection of amplified hepatitis B virus DNA

The sensitivity, specificity, reproducibility, detection level, and quantification potential of the SHARP Signal System for enzymatic detection of amplified hepatitis B virus (HBV) DNA in clinical samples were evaluated by testing 104 samples in parallel in a SHARP PCR, an in-house HBV PCR, and a dot blot hybridization assay for semiquantification. SHARP PCR showed a sensitivity of 100%, a specificity of 92.3% (resolved, 100%), a reproducibility of 92.3% (all discrepant serum samples involved very low levels of HBV DNA), and a detection level of at least 3.5 pg/ml. Clinically relevant quantification of the amplified products was not feasible.

Affinity capture-polymerase chain reaction for quantitation of hepatitis B virus DNA

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Genetic diversity of hepatitis B virus strains isolated in Rio de Janeiro, Brazil

Hepatitis B virus (HBV) genomes have been classified into six groups, A-F, group F being the most divergent. South America has provided the smallest number of strains studied at the genome level. The only HBV strain from this region sequenced completely has been classified in group F, and contains the most divergent of the HBV genomes presently known [Naumann et al. (1983): Journal of General Virology 74:1627-1632]. To evaluate genetic relatedness between strains isolated in South America and in the rest of the world, a restriction endonuclease analysis was carried out on 14 HBV strains (4 adw2, 3 adw4, 3 ayw2, and 4 ayw3) isolated in Rio de Janeiro, Brazil. C, pre-S, and X genes along with the 5' part of the P gene from these strains were amplified by the polymerase chain reaction. The DNA fragments were digested by BamHI, BstEII, EcoRI, HhaI, and TaqI endonucleases. The restriction patterns obtained were compared with those deduced from the nucleotide sequence of 26 HBV strains isolated in other continents. The results showed a large genetic variability of Brazilian strains. Taking into account that all the samples examined possessed the w antigenic subdeterminant, the number of different restriction patterns of strains isolated in Rio de Janeiro was at least as large as that of the reference strains isolated in the rest of the world. Some original restriction patterns were found in adw4 and ayw2 HBV strains.

Polymerase-chain-reaction-based semi-quantification of hepatitis D viraemia in patients treated with high doses of alpha 2b interferon

To study the antiviral efficacy of high doses of alpha 2b interferon (alpha 2b-IFN) for chronic hepatitis D treatment, we used polymerase-chain-reaction(PCR)-based semi-quantitative detection of HDV RNA. The semi-quantification method used was based on the appearance of a positive amplification signal as a function of the number of PCR cycles. By amplifying dilutions (10(-1)-10(-8)) of an HDV-positive woodchuck liver RNA, we confirmed that exponential amplification efficacy occurred at between 20 and 30 cycles. Positive signals were observed from dilution 10(-2) (gel electrophoresis after 20 cycles of PCR) to dilution 10(-7) (hybridization after 30 cycles of PCR). To characterize the HDV RNA level in sera of 8 patients treated with alpha 2b-IFN (10 MU/3 times a week) for 1 year, we extracted RNA from serum samples taken every 6 months. All samples were amplified in parallel for 20 and 30 PCR cycles. Analysis of HDV cDNA after ethidium bromide/agarose gel electrophoresis and after molecular hybridization (100 times more sensitive than gel analysis), enabled us to grade the signals observed from negative to positive as 1+, 2+, 3+ and 4+, with all results being positive. Three types of evolution of HDV viraemia were evidenced among the 8 treated patients. HDV replication continued to occur at a high level at the 6th and 12th month in 2 patient sera. For 2 other patients, an HDV RNA decrease or disappearance was evidenced in the serum at the 6th month; however, viral replication recurred at a higher level at the 12th month.(ABSTRACT TRUNCATED AT 250 WORDS)

High prevalence of HBV infectivity in blood donors detected by the dot blot hybridisation assay

Hepatitis B virus (HBV) continues to be a significant cause for post-transfusion hepatitis in India, in spite of the introduction of compulsory hepatitis B surface antigen (HBsAg) screening. To understand the true HBV-infective pool in the blood donor population, HBV DNA was detected by a 32P-labelled dot blot hybridisation assay in 605 donor units that were negative for HBsAg by a third-generation Elisa. Serum alanine aminotransferase (ALT) was estimated in all these samples and correlated with DNA positivity. The frequency of HBV DNA positivity in HBsAg-negative units was very high (9.91%) and correlated well with the elevation in ALT (p < 0.00005). However, the frequency of elevated ALT was high (11.9%), using the locally determined upper limit of normal, and half of the DNA-positive samples had a normal ALT. Thus, ALT is a poor surrogate marker for HBV infectivity and efforts should be made to apply DNA detection systems in blood banks.

Detection of hepatitis B virus DNA and determination of surface antigen expression in peripheral blood mononuclear cells from patients with AIDS

The polymerase chain reaction (PCR) was used to analyze the presence of hepatitis B virus (HBV) DNA in serum and peripheral blood mononuclear cells (PBMCs) from 20 patients with AIDS with and without conventional HBV serological markers. DNA sequences of HBV were detected in PBMCs from 13 patients, nine of whom were positive for anti-HBc only and four of whom were also positive for anti-HBs. When PBMCs from patients were activated in culture with phytohemagglutinin, the presence of HBsAg could be detected in the culture supernatants from four of 13 patients with HBV DNA in their PBMCs; for two of the four, HBV DNA could also be detected in the culture supernatant after DNA amplification. It was observed that HBV DNA sequences found in PBMCs can be reactivated by mitogen stimulation in some HIV-1 infected patients.

Competitive polymerase chain reaction and analysis of viral activity at the molecular level

Due to the high sensitivity level (which can be pushed to the limit of one molecule) and its extraordinary flexibility, the polymerase chain reaction (PCR) is the method of choice for the detection of nucleic acids present in very low concentration in biological samples. Since the qualitative features of PCR amplification have limited its use, several PCR-based approaches for the quantitation of low-abundance nucleic acid species have been planned and proposed in the last few years. Recently, different lines of evidence have indicated that competitive PCR and competitive reverse-transcription-PCR share several advantages over other quantitative approaches. This evidence opens up unexpected possibilities in many biological fields, including virology; in fact, availability of reliable techniques for the absolute quantitation of DNA and RNA species may be the key to a better understanding of the pathogenic steps of most viral diseases and for a more precise monitoring of patients treated with specific antiviral compounds. In this review article, we summarize the procedures adopted for this quantitative molecular approach; additionally, several important technical aspects to plan novel competitive PCR-based applications are analyzed, and early results obtained using cPCR for the direct evaluation of viral activity in vivo are discussed.

Detection of Theileria sergenti infection in cattle by polymerase chain reaction amplification of parasite-specific DNA

A pair of synthetic oligonucleotide primers, designed from the gene encoding a 32-kDa intraerythrocytic piroplasm surface protein of Theileria sergenti, were used to amplify parasite DNA from the blood of T. sergenti-infected cattle by means of the polymerase chain reaction (PCR). PCR-amplified DNA was examined by electrophoresis and by dot blot or microplate hybridization using a parasite-specific cDNA probe. PCR was specific for T. sergenti, since no amplification was detected with DNA from Anaplasma centrale, Babesia ovata, uninfected erythrocytes, and leukocytes. This method was sensitive enough to detect about 4.5 parasites per microliters of blood with a 10-microliters sample volume. Moreover, of 66 specimens from grazing cattle, 40 were microscopically positive, whereas PCR revealed that 54 samples were positive. Therefore, PCR provides a useful diagnostic tool for detecting T. sergenti-infected cattle, and it is significantly more sensitive than the current methods.

Suppression of the inhibitory effect of denatured albumin on the polymerase chain reaction by sodium octanoate: application to routine clinical detection of hepatitis B virus at its infectivity threshold in serum

Ten to fifteen percent of posttransfusion viral hepatitis cases are still caused by HBV despite mandatory third generation screening procedures for HBsAg. There is thus an urgent need for a simple, time-cost-effective, but very sensitive test for routine HBV DNA detection in serum. Nested-primed PCR has been shown to detect purified HBV DNA at its infectivity threshold in serum. Since this is too labor-intensive for routine testing, we assessed the efficiency of a Fast PCR procedure, of three pairs of primers, and of thirty-five simple serum pretreatments with the aim to achieve the same sensitivity level. Using ten-fold dilution in phosphate buffered saline as pretreatment and Fast PCR for 99 cycles, we were able to detect HBV DNA at the 2 x 10(3)/ml level in serum. Using either NaOH denaturation or sodium octanoate thermoprotection as pretreatment and Fast PCR for 99 cycles, we were able to detect HBV DNA at its infectivity threshold in serum, while the classical phenol/chloroform/isoamylic alcohol/isopropanol/ethanol DNA purification procedure enabled us to reach the 10 virus particles/ml level. These results suggest that denatured albumin is responsible for the well known inhibitory effect of serum proteins on Taq polymerase. Because of its simplicity and its lower risk of sample-to-sample cross-contamination, the sodium octanoate thermoprotection method was chosen for routine clinical detection of HBV in serum. The clinical usefulness of this approach is demonstrated by the results obtained with HBsAg-negative acute hepatitis B incubation sera and with anti HBe-positive chronic hepatitis B sera.

Hepatitis B virus occult infection in subjects with persistent isolated anti-HBc reactivity

The aim of this study was to investigate the presence of hepatitis B virus occult infection in asymptomatic subjects with persistent anti-HBc reactivity but no other hepatitis B virus serological markers, including HBsAg, anti-HBs, IgM anti-HBc and HBV-DNA. For this purpose we used both polymerase chain reaction assays in sera and immunohistochemistry for HBsAg and HBcAg in liver biopsy specimens. Twenty-four cases were studied: 15 were drug abusers or homosexuals (eight with normal alanine aminotransferase levels) and nine were heterosexuals with raised alanine aminotransferase levels (> 45 U/l) but with no history of blood transfusion or ethanol intake (< 80 g daily). In all but five cases, liver biopsy was performed in subjects with persistent elevated alanine aminotransferase levels. In 10 out of 24 cases (41.66%) hepatitis B virus infection was demonstrated by polymerase chain reaction or immunohistochemistry, and when results from both procedures were available (n = 11) hepatitis B virus infection was detected in 63.63% of the subjects. The only clinical feature associated with HBV infection was the presence of persistent elevated alanine aminotransferase levels (p < 0.05). In conclusion, persistent isolated anti-HBc reactivity may be a relatively common serologic pattern for hepatitis B virus occult infection, at least in patients with chronic liver disease.

Applications of polymerase chain reaction for identification of dengue viruses isolated from patient sera

A simple and sensitive procedure of reverse transcriptase polymerase chain reaction (RT-PCR) was developed previously such that all 4 serotypes of dengue viruses could be detected and their serotypes identified simultaneously in a single-step procedure. In this study we compared the RT-PCR with a conventional immunoperoxidase (PAP) staining method for the identification of dengue viruses currently isolated from patient sera. Sixty-six sera taken from dengue hemorrhagic fever (DHF) patients were subjected to virus isolation by inoculating onto C6/36 cell cultures. Screening for the presence of dengue viruses in culture fluids was done after 7 days of incubation by PAP staining using hyperimmune rabbit anti-dengue virus antibody as the primary reagent. Dengue viruses in positive cultures were further identified for their serotypes by PAP using type-specific monoclonal antibodies (MAb) and by RT-PCR. Thirty-two out of the 66 serum specimens tested (48.5%) were positive for dengue viruses. Of these, 5 were type 1 (DEN-1), 25 were type 2 (DEN-2) and 2 contained both DEN-1 and DEN-2. All cultures that were positive by PAP method were also positive by RT-PCR and vice versa. Thus, the results obtained by RT-PCR were in good agreement with those by PAP. It is important to point out that while all 5 DEN-1 isolates reacted readily with the MAb 1F1, only 2 of them could be identified by the MAb 15F3. Our data suggest that antigenic variation among DEN-1 isolates occur frequently and this should be taken into consideration in the selection of appropriate type-specific MAb for serotyping of dengue viruses.(ABSTRACT TRUNCATED AT 250 WORDS)

Polymerase chain reaction for the diagnosis of hepatitis B and C viral hepatitis

The detection of HBV, HCV, and HDV genomes through the use of the polymerase chain reaction (PCR) has made possible a new step in viral diagnosis. The main advantages of PCR are its extreme sensitivity and the possibility to develop rapid assays using non-radioactive probes. Several studies have now clearly shown its usefulness for the demonstration of viremias, the identification of seronegative viral carriers, and studies on mother-to-child transmission. Several limitations, however, still hamper the use of PCR and it should not yet be regarded as a routine test. The main developments to be expected in the near future deal with automatisation, prevention of contamination, and quantification.

DNA and RNA amplification in urology: the polymerase chain reaction

Polymerase chain reaction (PCR) technology is a promising molecular approach for diagnosis of genitourinary tract infections, inherited disorders, tumor-associated genetic alterations and tumor markers. Because it is based on exponential amplification, the technology is capable of ultimate theoretical sensitivity. Although not entirely free of technical limitations, PCR holds advantages over other diagnostic tests, including exquisite sensitivity, specificity, interchangeability and speed.

A one-tube, one manipulation RT-PCR reaction for detection of Ross River virus

A sensitive, single tube reverse transcription-polymerase chain reaction (RT-PCR) protocol for the detection of Ross River virus (RRV) is described. All components necessary for both reverse transcription and PCR were combined in a single tube, and reverse transcription and PCR carried out sequentially in a single, non-interrupted thermal cycling program. The antisense oligonucleotide from the two primers selected for use in the PCR also served to prime specifically for the reverse transcription. The 549 bp product was detected by electrophoresis and ethidium bromide staining. The detection limit using this system was 18 fg of purified viral RNA or 1.3 pfu of whole virus. Greater sensitivity cannot reasonably be expected unless a more sensitive method than electrophoresis and ethidium bromide staining is used for PCR product detection, such as nested PCR or hybridisation with labelled probe. This PCR detection system will be adapted for detection of RRV in mosquito populations for virus surveillance programs.

Use of quantitative polymerase chain reaction to quantitate cytokine messenger RNA molecules

A quantitative polymerase chain reaction (PCR) using an internal control (Standard) RNA was developed for precise quantitation of human cytokine mRNA. The target mRNA and internal control were simultaneously reverse transcribed and co-amplified using the same set of primers. The amount of specific target mRNA is then quantitated by extrapolating against the standard curve generated with the internal standard. The internal control RNA consisted of linearly connected sequences of the 5' primers of multiple cytokine genes followed by the complementary sequences to their 3' primers in the same order. This structure of the internal standard enables one to use the same internal standard for quantitating multiple cytokine mRNAs. Using this approach, we estimated the induced levels of cytokine mRNA, IL2, IL6, and TNF-alpha to be 2.8 x 10(6), 2.4 x 10(5) and 3.4 x 10(8) molecules per 1.0 microgram total cellular RNA of Jurkat, THP-1 and HL 60 cells, respectively. Comparable values were obtained when quantitation experiments were done on another batch of THP-1 and HL-60 total cellular RNA. The excellent sensitivity and reproducibility makes this approach a valuable one in following changes in cytokine gene expression in wide variety of conditions, both in vivo and in vitro.

Persistence of hepatitis B virus DNA after reduction of viral replication in serum and liver

Liver and serum samples from 67 children with hepatitis B chronic infection, whether or not treated with recombinant interferon, were analyzed for the presence of hepatitis B virus DNA. After follow-up, 44/67 (66%) still had serum and liver viral DNA; 23/67 (34%) were negative for serum hepatitis B virus DNA. Of the 23 children in the latter group, liver biopsy was available in 21 and viral DNA was not detected by Southern-blot in 20. In the remaining patient, viral DNA was in an episomal nonreplicative form. Polymerase chain reaction was performed in the 21 serum samples negative for viral DNA by conventional techniques and in the 21 liver samples (20 negative for hepatitis B virus DNA and 1 with episomal nonreplicative form). All liver samples resulted in a positive reaction to viral DNA by this technique. Serum viral DNA by polymerase chain reaction was detected in 15/21 (71%) of these patients. The mean of alanine aminotransferase values was similar in patients with or without hepatitis B virus DNA in serum by polymerase chain reaction. In summary, in the majority of the patients who respond to the therapy, there is a persistence of viral replication detected by polymerase chain reaction. This fact explains the persistence of serum HBsAg in these patients. However, more studies are necessary to determine the meaning of the presence of hepatitis B virus DNA that is only detectable by polymerase chain reaction.

Detection of hepatitis B virus DNA in chronic carriers by the polymerase chain reaction

The polymerase chain reaction (PCR) was used to detect hepatitis B virus DNA (HBV-DNA) in serum samples of 104 chronic HBV carriers. Of 22 patients positive for both HBV surface (HBsAg) and HBVe (HBeAg) antigens, seven were positive for HBV-DNA on dot blot hybridisation, and all 22 positive in the PCR. Of 41 HBsAg positive patients who had antibodies against HBeAg (anti-HBe), only three were positive for DNA-HBV on dot blot hybridisation, however DNA was detected in 30 of them with the PCR. Similarly, of 41 individuals with antibodies against HBsAg (anti-HBs), 23 yielded positive results in the PCR technique, although dot blot hybridisation detected HBV-DNA in only one patient. These results indicate that while serological and conventional DNA hybridisation assays are not sensitive enough to determine the infectivity of HBV chronic carriers, PCR is an accurate method for establishing the status and progression of disease in these patients.

Chemiluminescent microtiter method for detecting PCR amplified HIV-1 DNA

A rapid and sensitive method for detecting HIV-1 DNA sequences amplified by polymerase chain reaction (PCR) is described. The method uses solution phase hybridization for rapid and efficient annealing between digoxigenin-labeled targets and biotinylated capture probes. Hybrids containing biotin are captured onto streptavidin coated microwells and all other PCR components are washed away, including spurious amplification products. The presence of the digoxigenin-labeled amplified HIV target is then detected by anti-digoxigenin-alkaline phosphatase conjugates using the chemiluminescent substrate PPD. This approach maintains high specificity by nucleic acid dependent capture, and high sensitivity by efficient solution hybridization. The method is rapid (2 hours), and capable of detecting 10 HIV targets.

Sequence analysis of the hepatitis B virus pre-C region in hepatocellular carcinoma [HCC] and nontumoral liver tissues from HCC patients

We investigated whether replication-competent pre-C/C defective mutants of hepatitis B virus (HBV) are detectable in primary human hepatocellular carcinoma (HCC) tissues from patients of a geographic area endemic for such mutants. DNAs extracted from formalin-fixed paraffin-embedded HCC samples were checked for the presence of specific HBV DNA sequences using the polymerase chain reaction (PCR). Amplified pre-C regions from nine HCC samples were directly sequenced as were samples of nontumoral liver tissues from five of these patients. The data show that hypervariable distal pre-C sequences were present in all nine HCC samples; this high variability was dependent on point mutations, which led to amino acid substitutions in nearly all cases. Interestingly, seven of the nine HBV DNA-positive samples from HCC tissues (but not samples from peritumoral liver tissue) showed mutations leading to amino acid substitution at the level of a distal cysteine residue. No mutation generating a translationally defective pre-C/C region was detectable in the tumor samples. Otherwise, in four of the six nontumoral liver tissues available from the same patients, a pre-C sequence with an in-frame TAG stop codon was detectable, although in three cases as a component of mixed population.

Transforming growth factor-beta 1 is decreased in remodeling hypertensive bovine pulmonary arteries

The development of pulmonary hypertension in hypoxic newborn calves is associated with a complex pattern of increased tropoelastin and type I procollagen synthesis and deposition by smooth muscle cells in large elastic pulmonary arteries compared to normoxic controls. We examined the possibility that transforming growth factor-beta 1 (TGF-beta 1) may be associated with the production of extracellular matrix protein in this model of pulmonary hypertension. Medial smooth muscle cells in both normotensive and hypertensive vessels, as assessed by immunohistochemistry, were the major source of TGF-beta 1. Staining was confined to foci of smooth muscle cells in the outer media and appeared greater in normotensive than hypertensive vessels. Consistent with the immunohistochemistry, a progressive, age-dependent increase in normotensive pulmonary artery TGF-beta 1 mRNA was observed after birth, whereas TGF-beta 1 mRNA remained at low, basal levels in hypertensive, remodeling pulmonary arteries. These observations suggest that local expression of TGF-beta 1 is not associated with increased extracellular matrix protein synthesis in this model of hypoxic pulmonary hypertension.

Long-term follow-up of hepatitis B chronic carriers who responded to interferon therapy

We studied the long-term outcome of patients with chronic hepatitis B virus (HBV) infection who responded to interferon (IFN) therapy. Between 1983 and 1988, 120 patients were included in 5 different protocols; 94 patients were treated with IFN and 26 were controls. Loss of serum HBV-DNA was considered a partial response and occurred in 34 of the treated patients and in 10 of the controls. Only the partial-response patients were followed up for 14-64 months (mean 46 months). HBeAg disappeared in 32/34 of the partial-response treated patients and in 9/10 of the controls. During the follow-up period, 6/34 (18%) treated patients and 1/10 controls suffered a reactivation of the disease with reappearance of HBV-DNA. Only 8/34 (23%) treated patients and 1/10 of the controls lost HBsAg; no statistical differences were observed in baseline characteristics between HBsAg-negative patients and patients who remained HBsAg-positive. Of eight HBsAg-negative treated patients, four were serum HBV-DNA-negative upon polymerase chain reaction and thus formed the HBsAg-negative control cases. Although the frequency of HBsAg loss in treated patients is relatively low, the improvement in liver disease obtained from IFN therapy is sustained over a long period.

Reverse transcriptase inhibits Taq polymerase activity

Detection of viral RNA by polymerase chain reaction (PCR) requires the prior reverse transcription of the viral RNA. In order to minimise the number of manual manipulations required for processing large numbers of samples, we attempted to design a system whereby all the reagents required for both reverse transcription and amplification can be added to one tube and a single, non-interrupted thermal cycling program performed. Whilst attempting to set up such a one-tube system with Taq polymerase (Taq; Biotech International) and avian myoblastosis virus (AMV) reverse transcriptase (RT), we noticed a substantial decrease in the sensitivity of detection of viral RNA. Investigation of this phenomenon has revealed direct interference of RT with Taq polymerase. Evidence supporting this conclusion includes the following observations: (1) increasing the ratio of Taq to RT improves sensitivity; (2) adding non-homologous RNA improves sensitivity; (3) RT that has been heat inactivated prior to Taq addition does not exert this effect; (4) the effect is not sequence restricted; (5) the Mg2+ ions are not sequestered by RT. In addition, the effect is not limited to AMV RT, Moloney murine leukaemia virus RT also affects Taq activity.

Prevention of pre-PCR mis-priming and primer dimerization improves low-copy-number amplifications

A Hot Start Polymerase Chain Reaction (PCR) entails the withholding of at least one reagent from the reaction mixture until the reaction tube temperature has reached 60-80 degrees C. Hot Start amplification with an AmpliWax vapor barrier uses a layer of solid wax to separate the retained reagent(s) and the test sample from the bulk of the reagents until the first heating step of automated thermal cycling melts the wax and convectively mixes the two aqueous layers. Wax-mediated Hot Start PCR greatly increases the specificity, yield, and precision of amplifying low copy numbers of three HIV targets. In the presence of 1 microgram of human placental DNA (1.6 x 10(5) diploid genomes) the specificity improvement entails considerable to complete reduction in the amplification of mis-primed sequences and putative primer oligomers. When mis-priming is negligible, the procedural improvement still suppresses putative primer oligomerization. Hot Start PCR with an AmpliWax vapor barrier permits routine amplification of a single target molecule with detection by ethidium stained gel electrophoresis; nonisotopically visualized probing suffices for confirmation. The improved amplification performance is evident for target copy numbers below approximately 10(3).

Molecular hybridization techniques in current diagnosis of chronic hepatitis B in childhood

Following the cloning and sequencing of the hepatitis B virus genome, molecular hybridization techniques have been established to detect hepatitis B virus (HBV) DNA in serum and liver tissue. Analyses can be performed by dot blot, Southern blot and in situ hybridization. HBV DNA is regarded to be the most sensitive marker of viral replication and infectivity which was previously related to the presence of hepatitis B e antigen in serum and hepatitis B core antigen in liver cells. In liver tissue different molecular patterns can be recognized as free viral DNA and integrated sequences. Furthermore, introduction of the polymerase chain reaction allows the detection of very small amounts of viral DNA and has markedly improved diagnostic sensitivity. Thus the study of HBV DNA has become a valuable part of the routine diagnosis in chronic hepatitis B, providing a more reliable evaluation of virus replication and infectivity, and facilitating more precise statements about course and prognosis of the disease.

Detection of serum HBV-DNA by polymerase chain reaction (PCR) in patients before reactivation of chronic hepatitis B

Reactivation of chronic hepatitis B is characterized by the reappearance of HBV-DNA in serum. The purpose of the study was to determine whether, before reactivation, HBV-DNA would be detectable in serum, using a sensitive procedure of detection, namely polymerase chain reaction (PCR). We studied 17 patients with chronic hepatitis B who experienced an episode of reactivation, defined by the reappearance of HBV-DNA in serum. None of these 17 sera had HBV-DNA demonstrable by dot-blot hybridization nor liquid hybridization in sera collected before reactivation. Using PCR, HBV-DNA was detected, before reactivation, in 13 of the 17 episodes of reactivation tested with Southern-blot and hybridization. HBV-DNA was not detectable with PCR in the serum of four patients who subsequently experienced an episode of reactivation. In conclusion, our results show low level HBV replication before reactivation in most, but not all, HBs-positive, HBV-DNA-negative patients. This suggests that reactivation may occur even in patients with no HBV-DNA demonstrable in serum with PCR prior to reactivation.

Demonstration of hepatitis B virus DNA by polymerase chain reaction in the serum and the liver after spontaneous or therapeutically induced HBeAg to anti-HBe or HBsAg to anti-HBs seroconversion in patients with chronic hepatitis B

The objective was to determine the proportion of patients with chronic hepatitis B in whom hepatitis B virus DNA is demonstrated by polymerase chain reaction after HBeAg to anti-HBe or HBsAg to anti-HBs spontaneous or therapeutically induced seroconversion. Polymerase chain reaction was performed on serum 6 and 12 mo after HBeAg to anti-HBe seroconversion in 12 patients and 2, 6 and 12 mo after HBsAg to anti-HBs seroconversion in 13 patients. Polymerase chain reaction was performed on liver tissue after HBeAg to anti-HBe seroconversion in five patients and after HBsAg to anti-HBs seroconversion in one patient. Serum HBV DNA was demonstrated by polymerase chain reaction in 83% of patients 6 or 12 mo after HBeAg to anti-HBe seroconversion and in 58%, 31% and 15% of patients at 2, 6 and 12 mo, respectively, after HBsAg to anti-HBs seroconversion. Liver HBV DNA was demonstrated by polymerase chain reaction in all patients tested. Our results show that (a) a reduced level of hepatitis B virus replication persists in most of the patients after HBeAg to anti-HBe seroconversion and might be predictive of reactivation, and (b) in contrast, hepatitis B virus replication progressively disappears in most of the patients after HBsAg to anti-HBs seroconversion.

Comparison of hepatitis B virus subtyping ofd/y determinants by radioimmunoprecipitation assay and the polymerase chain reaction

Using a double polymerase chain reaction a method was devised for detecting and subtyping hepatitis B virus DNA in serum samples. Primers from the S-gene were selected from the sequence analyses of five HBV HBsAg subtypes, to amplify HBV DNA and subtype for y specific DNA. Thirty-eight samples were subtyped for d and y determinants by radioimmunoprecipitation assay (RIPA) and the polymerase chain reaction (PCR). Subtyping by PCR and RIPA was in agreement in 100% of subtype y samples and 83.3% of subtype d, giving an overall correlation of 92.1%. As a third comparison, 12 amplified samples were digested by the restriction enzyme Sau 3A, which differentiates between subtypes y and d. The digest results agreed with PCR in 83.3% of the samples. In addition, we compared our standard phenol/chloroform extraction against a rapid one step method. The phenol/chloroform stage was found to be essential for the removal of nucleases and polymerase inhibitors present in sera.