In vitro amplification of hepatitis B virus sequences from liver tumour DNA and from paraffin wax embedded tissues using the polymerase chain reaction

CD34(+) Liver Cancer Stem Cells Were Formed by Fusion of Hepatobiliary Stem/Progenitor Cells with Hematopoietic Precursor-Derived Myeloid Intermediates

A large number of cancer stem cells (CSCs) were identified and characterized; however, the origins and formation of CSCs remain elusive. In this study, we examined the origination of the newly identified CD34(+) liver CSC (LCSC). We found that CD34(+) LCSC coexpressed liver stem cell and myelomonocytic cell markers, showing a mixed phenotype, a combination of hepatobiliary stem/progenitor cells (HSPCs) and myelomonocytic cells. Moreover, human xenografts produced by CD34(+) LCSCs and the parental cells, which CD34(+) LCSC was isolated from, coexpressed liver cancer and myelomonocytic markers, also demonstrating mixed phenotypes. The xenografts and the parental cells secreted albumin demonstrating their hepatocyte origin and also expressed cytokines [interleukin (IL)-1b, IL-6, IL-12A, IL-18, tumor necrosis factor-alpha (TNF-α), and CSF1] and chemokines (IL-8, CCL2, and CCL5). Expression of these cytokines and chemokines responded to the stimuli [interferon-γ (INF-γ), IL-4, and lipopolysaccharide (LPS)]. Furthermore, human xenografts and the parental cells phagocytized Escherichia coli. CD34(+) LCSC coexpressed CD45, demonstrating that its origin appears to be from a hematopoietic precursor. The percentage of cells positive for OV6, CD34, and CD31, presenting the markers of HSPC, hematopoietic, and myelomonocytic cells, increased under treatment of CD34(+) LCSC with a drug. Cytogenetic analysis showed that CD34(+) LCSC contained a greater number of chromosomes. HBV DNA integrations and mutations in CD34(+) LCSC and the parental cells were identical to those in the literature or the database. Thus, these results demonstrated that CD34(+) LCSCs were formed by fusion of HSPC with CD34(+) hematopoietic precursor-derived myeloid intermediates; it appears that this is the first report that human CSCs have been formed by the fusion. Therefore, it represents a significant step toward better understanding of the formation of human CSC and the diverse origins of liver cancers.

Genetic variability and integration of Merkel cell polyomavirus in Merkel cell carcinoma

Merkel cell polyomavirus (MCPyV) is associated to Merkel cell carcinoma (MCC). We studied 113 MCC tumoral skin lesions originating from 97 patients. MCPyV detection was higher in fresh-frozen (FF) biopsies (94%) than in formalin-fixed paraffin-embedded biopsies (39-47%). Mean viral load in FF tumor was of 7.5 copies per cell with a very wide range (0.01-95.4). Nineteen complete sequences of LTAg were obtained, mainly from FF biopsies when the viral load was high. Seventeen showed stop codons, all localized downstream of the pRb protein binding domain. Sequence comparison and phylogenetic analysis showed that all sequences clustered in the large C clade of MCPyV strains. MCPyV integration was demonstrated in 19 out of 27 FF MCC DNA biopsies without evidence of specific host cellular genome integration site. In 13/19 cases, the viral junction was located within the second exon of the LTAg, after the pRB binding domain.

Low prevalence of HBV DNA in the liver allograft from anti-HBc-positive donors: a single-center experience

Allografts from donors positive for antibody to hepatitis B core antigen (anti-HBc(+)) can transmit hepatitis B virus (HBV) to the recipients. We aimed to study the prevalence of HBV DNA in liver allografts from anti-HBc(+) donors. Between January 2003 and December 2008, this retrospective study identified 18 patients who received a liver from an anti-HBc(+) donor. Pre- and post-transplantation HBV serology and serum HBV DNA level of the study subjects were reviewed. DNA extracted from liver biopsy tissue was used for PCR assay. Immunohistochemistry was also performed to determine viral protein expression. We observed a low prevalence of HBV DNA in allografts from anti-HBc(+) donors even among patients who did not receive prophylaxis. Only one of 18 patients had detectable HBV DNA in the liver allograft. This recipient was seronegative for HBV before transplantation and did not receive prophylaxis after transplantation, and developed de novo hepatitis B. Of the five patients who were positive for both antibody to hepatitis B surface antigen and anti-HBc before transplantation and did not receive prophylaxis after transplantation, none developed HBV infection. Prophylaxis for HBV is important for seronegative recipients receiving a liver from an anti-HBc(+) donor. Such prophylaxis may not be necessary for recipients who do not have detectable HBV DNA in the liver allograft.

Molecular pathology in anatomic pathology practice: a review of basic principles

Molecular testing in pathology emerged shortly after polymerase chain reaction became a standard molecular biology assay. Testing efforts began in the clinical laboratories primarily with assays for genetically inherited diseases and assays for clonality in hematologic malignancies. Today, the field has evolved into "molecular diagnostics," which encompasses testing in almost every area of anatomic pathology. Molecular testing is now even making its way definitively into both surgical pathology and cytopathology, although molecular anatomic pathology is still young with few standard tissue-based molecular assays. As more clinically valuable information is gained from molecular pathology testing of tissues, unique challenges are also becoming apparent at the intersection between tissue diagnosis and DNA diagnosis. This review focuses on basic molecular pathology concepts, with particular emphasis on the challenge of tissue-based testing in anatomic pathology.

Dendritic cell therapy with improved outcome in glioma multiforme--a case report

Malignant gliomas are the most devastating tumors in clinical practice and have poorest survival. Immunological treatment of such patients may likely increase the survival and quality of life. Dendritic cells (DCs), most potent antigen presenting cells in combination with oral chemotherapeutic agents may be tried for patients giving consent to such treatment. We have successfully combined the two therapies in an adult male patient who was on downhill course after being operated on once with post operation chemotherapy and radiotherapy for glioma in the left parietal area. He received five dendritic cell therapy vaccines in combination with oral chemotherapy and responded dramatically having near normal quality of life for an additional five months with this regime, increasing the survival after operation to 11 months. This therapy is continuing with radiological betterment of the lesion. The DCs are matured with antigen extracted from wax embedded tissue at 6th day of culture. We feel that the treatment can be given to more number of patients to establish its efficacy for the dreaded cancer glioblastoma multiforme.

Cutaneous leishmaniasis: evaluation by polymerase chain reaction in the Cukurova region of Turkey

The diagnosis of cutaneous leishmaniasis (CL) may depend on the detection of the parasite in histologic sections, the growth of the promastigotes in culture, or the identification of parasite by other techniques. We performed polymerase chain reaction (PCR) on paraffin-embedded biopsies to determine the validity of this technique for diagnosis of CL. PCR was used to detect the parasite using 2 different DNA extraction methods. PCR was positive in all 20 cases when the Leishmania parasite was detected by light microscopy. Twenty-seven of 34 cases that were negative microscopically for the parasite were positive using PCR. The first extraction method of DNA identified leishmanial DNA in 41 of 54 cases (75.9%); the second extraction of DNA was positive in 47 of 54 cases (87%). PCR was negative in all of the nonleishmaniasis cases. The PCR-based method appears to be a useful diagnostic approach for identification of suspected cases of CL.

Design and standardization of PCR primers and protocols for detection of clonal immunoglobulin and T-cell receptor gene recombinations in suspect lymphoproliferations: report of the BIOMED-2 Concerted Action BMH4-CT98-3936

In a European BIOMED-2 collaborative study, multiplex PCR assays have successfully been developed and standardized for the detection of clonally rearranged immunoglobulin (Ig) and T-cell receptor (TCR) genes and the chromosome aberrations t(11;14) and t(14;18). This has resulted in 107 different primers in only 18 multiplex PCR tubes: three VH-JH, two DH-JH, two Ig kappa (IGK), one Ig lambda (IGL), three TCR beta (TCRB), two TCR gamma (TCRG), one TCR delta (TCRD), three BCL1-Ig heavy chain (IGH), and one BCL2-IGH. The PCR products of Ig/TCR genes can be analyzed for clonality assessment by heteroduplex analysis or GeneScanning. The detection rate of clonal rearrangements using the BIOMED-2 primer sets is unprecedentedly high. This is mainly based on the complementarity of the various BIOMED-2 tubes. In particular, combined application of IGH (VH-JH and DH-JH) and IGK tubes can detect virtually all clonal B-cell proliferations, even in B-cell malignancies with high levels of somatic mutations. The contribution of IGL gene rearrangements seems limited. Combined usage of the TCRB and TCRG tubes detects virtually all clonal T-cell populations, whereas the TCRD tube has added value in case of TCRgammadelta(+) T-cell proliferations. The BIOMED-2 multiplex tubes can now be used for diagnostic clonality studies as well as for the identification of PCR targets suitable for the detection of minimal residual disease.

Prevalence of BK virus and JC virus in peripheral blood leukocytes and normal arterial walls in healthy individuals in China

Several studies have demonstrated that BK virus (BKV) and JC virus (JCV) establish latent infection in peripheral blood leukocytes (PBLs) of healthy individuals; however, the main populations studied are European. In this study, the prevalence of BKV and JCV DNA in PBLs from healthy adult individuals and umbilical cord blood from newborn children in China was detected by semi-nested polymerase chain reaction (snPCR) followed by restriction enzyme analysis. The results suggest that the healthy adult Chinese population harbors BKV and JCV DNA in peripheral leukocytes. Overall, the prevalence of BKV and JCV DNA in PBLs of healthy adult individuals was 42.1% and 7.8%, respectively. The overall prevalence of BKV DNA was significantly higher than that of JCV DNA. None of the umbilical cord blood samples from newborn children were positive for BKV and JCV DNA. To understand further the target tissues involved in establishment of BKV and JCV latency in healthy individuals, the presence of DNA from both viruses was detected in normal arterial wall samples from 20 young trauma victims by the same method used for leukocyte DNA. BKV DNA was detected alone in 20% of samples tested; JCV DNA was not detected alone in any of the samples. DNA from both viruses was found in 5% of samples. This is the first report to show that normal arterial walls of healthy individuals may be another target site of latency for BKV and JCV.

Prevalence and distribution of human herpesvirus 6 variants A and B in adult human brain

The presence of human herpesvirus 6 (HHV-6) in brain tissues of 40 consecutive post-mortem cases was examined. For each case, autopsy samples were collected from the cerebellum, frontal, temporal, parietal and occipital lobes of both sides of the brain. HHV-6 DNA was detected by nested polymerase chain reaction and characterised into variants A and B. Overall, 97/400 (24.3%) samples were positive for HHV-6 DNA with 16 being variant A and 81 being variant B, but none of the samples harboured both variants. When analysed by patient, 34/40 (85%) had HHV-6 DNA detected in the brain. The viral DNA positivity did not show significant variation with gender and age. Four patients harboured variant A, 23 harboured variant B, and seven had both variants at different positions. The results indicate that both HHV-6A and HHV-6B are neurotropic and human brain may be another site for latency. HHV-6B was detected in brain tissues of a majority (75%) of the studied population and with a widespread distribution within the brain. Although the observed prevalence of HHV-6A in brain is lower (27.5%), in view of its lower seroprevalence, the neuroinvasive potential of variant A may be comparable to that of variant B. Although both variants are potential pathogens for the nervous system, the fact that they can exist, probably for most of the time, as commensals in human brain needs to be considered when interpreting their roles in neuropathology.

Association of human beta-herpesviruses with the development of cervical cancer: bystanders or cofactors

BACKGROUND/AIM

Human papillomaviruses (HPVs) are important, but not sufficient, for the development of cervical cancer. All three human beta-herpesviruses--cytomegalovirus (CMV) and human herpesviruses (HHV) types 6 and 7--have been detected in the cervix. In addition, CMV and HHV-6 can interact with HPVs in vivo. This study examined the possible role of beta-herpesviruses in cervical cancer development.

METHODS

HPV, CMV, HHV-6, and HHV-7 were detected by the polymerase chain reaction using cervical scrapes taken at colposcopy from 388 women. HPV types were identified using restriction fragment length polymorphisms. Colposcopy guided biopsies were taken from abnormal areas, and the histological findings were regarded as the final diagnoses. The associations between herpesvirus infection and the degree of cervical lesion were analysed with respect to HPV status.

RESULTS

Of the 388 women, 51.8% had a normal cervix, 14.4% had cervical intraepithelial neoplasia grade 1 (CIN1), 8.2% had CIN2, 19.3% had CIN3, and 6.2% had invasive carcinoma. Overall, the positive rates for high, intermediate, and low risk HPVs were 18.8%, 21.4%, and 5.2%, respectively. Fifteen patients harboured HPVs for which the genotype could not be identified. Positive rates for CMV, HHV-6, and HHV-7 were 9.5%, 3.6%, and 3.4%, respectively. HPV positive patients carried a higher risk for high grade lesions (CIN2/3 or carcinoma) (odds ratio (OR), 5.24; 95% confidence interval (CI), 3.19 to 8.62; chi 2 = 51.79; p < 0.001), whereas those positive for CMV, HHV-6, or HHV-7 did not. Thirteen of 131 patients with high grade lesions had HPV/herpesvirus coinfections, but no association with the cervical lesion was noted. Furthermore, positive rates for herpesviruses among HPV negative, high/intermediate risk HPV negative, and high risk HPV negative subgroups were similarly low and without a significant association.

CONCLUSIONS

The ubiquitous nature of herpesviruses may pose difficulty in elucidating their pathogenic role. These results indicate that CMV, HHV-6, and HHV-7 are bystanders rather than cofactors in the oncogenesis of cervical cancer.

Prevalence and distribution of human herpesvirus 7 in normal brain

Although it has been recognised that human herpesvirus 7 (HHV-7) establishes latent infection in CD4+ T lymphocytes and productive infection in salivary glands, recent data suggest that its in vivo tropism may be more widespread. In this study, the prevalence and distribution of HHV-7 in brain tissues of 30 consecutive post-mortems were examined by nested polymerase chain reaction. For each post-mortem, 10 fresh autopsy tissue samples were collected respectively from the cerebellum, frontal, temporal, parietal, and occipital lobes of both cerebral hemispheres. These patients were aged from 20-95 years (mean = 61.4, SD = 20.2) with a male:female ratio of 2:1. Three patients died of intracranial haemorrhage, the others died of causes unrelated to the central nervous system. Overall, 5% (15/300) of the brain tissue samples were positive for HHV-7 DNA. The positive rates with respect to anatomical positions were similar (0-3/30). When analysed by patient, 36.7% (11/30) were HHV-7 DNA positive. The viral DNA-positive and -negative groups did not show a significant difference in gender or age distribution. The majority (81.8%) of viral DNA-positive patients had HHV-7 DNA detected at only one anatomical position; only two patients had viral DNA detected simultaneously at three anatomical sites. These results suggest that HHV-7 persists in brain tissues of a substantial proportion of the adult population, and in most individuals, its distribution is probably confined to one site rather than pervasive. Further studies to elucidate the role of this ubiquitous virus in neuropathology are warranted.

Use of the polymerase chain reaction assay for the detection of Mycobacterium avium subspecies paratuberculosis in blood and liver biopsies from experimentally infected sheep

OBJECTIVE

To evaluate a polymerase chain reaction-based assay for the detection of Mycobacterium avium subsp paratuberculosis in blood and liver biopsies from subclinically infected sheep.

STUDY DESIGN

A direct PCR assay for the detection of M a paratuberculosis was applied to liver biopsy specimens and to samples of blood that were sequentially collected over 53 weeks from 14 sheep infected experimentally with the organism.

RESULTS

Of 117 blood samples from the 14 experimentally infected sheep, two tested positive in the PCR assay. Both positive results were obtained in two subclinically infected sheep that had paratuberculosis later confirmed by histological examination at necropsy. However, the assay failed to detect the target DNA in samples of blood from five other sheep with histologically confirmed paratuberculosis. Similarly, the PCR assay on liver biopsy specimens collected 32 weeks after administration of M a paratuberculosis gave only two positive results, both of which were obtained in sheep with histological evidence of paratuberculosis.

CONCLUSIONS

The PCR assay on blood and liver biopsies does not provide a useful method for the diagnosis of M a paratuberculosis infection in subclinically infected sheep.

Survey for the presence and distribution of human herpesvirus 8 in healthy brain

Brain tissues from both sides of the cerebellum and frontal, temporal, parietal, and occipital lobes were collected postmortem from 30 patients for human herpesvirus 8 (HHV-8) detection by PCR. Overall, 42 of 300 (14.0%) samples were positive, with similar rates for each position. Nineteen patients (63.3%) were positive and showed a significant increase in positivity with age (P = 0.007). The results indicate a neuroinvasive and neuropersistent potential of HHV-8.

Hepatitis C virus from the hearts of patients with myocarditis and cardiomyopathy

The myocardium may be the target of several types of viral infections. The importance of hepatitis C virus (HCV) infection has been recently noted in patients with myocarditis and in patients with dilated or hypertrophic cardiomyopathy. The present study sought to detect HCV genomes in formalin-fixed paraffin sections of autopsied hearts from patients with myocarditis and patients with dilated or hypertrophic cardiomyopathy. Paraffin sections were deparaffinized, RNA was extracted, and the positive and negative strands of HCV RNA were detected by performing reverse transcription and nested polymerase chain reaction. The polymerase chain reaction products were cloned and sequenced. beta-actin gene was used as a control for the successful amplification of a housekeeping gene. Among 106 hearts examined, beta-actin gene was amplified in 61 hearts (57.5%). Among the latter, HCV RNA was detected in 13 hearts (21.3%), and negative strands in 4 hearts (6.6%). HCV RNA was found in 4 hearts (33.3%) with myocarditis, in 3 hearts (11.5%) with dilated cardiomyopathy, and in 6 hearts (26.0%) with hypertrophic cardiomyopathy. The sequences recovered from nine patients were highly homologous to the standard strain of HCV. HCV genomes were not found in either 35 hearts from patients with myocardial infarction or 20 hearts from patients with noncardiac diseases. These HCV RNA positive samples were obtained from 1 heart in 1979, 7 hearts between 1980 and 1989, and 5 hearts since 1990, indicating that HCV RNA can be amplified from paraffin-embedded hearts preserved for many years. This method of detecting HCV genomes in formalin-fixed paraffin cardiac specimens has enabled us to widen our research into HCV infection and has been helpful in identifying the presence of HCV infection in cardiac myopathic disorders.

Presence of human herpesviruses 6, 7, and 8 DNA sequences in normal brain tissue

The three novel human herpesviruses (HHV) 6, 7, and 8 are predominantly, but not exclusively, lymphotropic. In an attempt to elucidate their neurotropism in vivo, viral DNA sequences present in fresh autopsy cortical brain tissues obtained from 84 consecutive Chinese subjects (mean age, 66.9 years; range, 21-98 years) were detected by a nested polymerase chain reaction. These patients were apparently immunocompetent and free of clinical signs of viral diseases. HHV-6 DNA was detected in 36 of 84 (42.9%) patients, and the DNA-positive and -negative groups did not show a significant difference in age or sex distribution. Of the 36 HHV-6 DNA-positive cases, 9 (25%) were variant A and 27 (75%) were variant B. In view of the lower prevalence of variant A than variant B in the adult population, the two variants may share a comparable neuroinvasive potential. HHV-7 and HHV-8 DNA were detected respectively in three and two patients. The low positive rates of HHV-7 and HHV-8 may represent a relatively lower neuroinvasive potential of the viruses. Alternatively, the localization of HHV-7 and HHV-8 may be more restricted and the sampled cortical tissues may not represent the most abundant site of persistence in the nervous system. The results provide molecular evidence of the presence of the three newly identified herpesviruses in brain tissue. The pathogenic role for HHV-7 and HHV-8, as with HHV-6, in neurological diseases should not be overlooked.

Detection of human herpesviruses 6 and 7 genomic sequences in brain tumours

BACKGROUND

Human herpesviruses 6 and 7 (HHV-6, HHV-7) are ubiquitous, with primary infection occurring early in life followed by persistence, which may involve neural tissue. While HHV-6 and HHV-7 are predominantly T lymphotropic, the extent of tissue tropism in persistent infection is not known.

AIM

To investigate neuropersistence and the role of HHV-6 and HHV-7 in brain tumorigenesis.

METHODS

Nested polymerase chain reaction was used to detect HHV-6 and HHV-7 genomic sequences in preparations of total DNA extracted from 98 formalin fixed, paraffin embedded primary brain tumours. HHV-6 detected was further characterized into variants A and B by restriction fragment length analysis.

RESULTS

HHV-6 was detected in 8.2% of cases and HHV-7 in 14.3% (14/98). None of the positive samples contained both viruses. Among the eight HHV-6 positive tumours, three harboured variant A and five variant B. Four of the five ependymomas studied contained viral DNA. Otherwise, both HHV-6 and HHV-7 were present at similar low frequencies in most of the tumour types investigated.

CONCLUSIONS

The findings do not support an aetiological role of HHV-6 and HHV-7 in primary brain tumour, but they suggest that HHV-6 and HHV-7 are neurotropic in vivo and that the central nervous system seems to be one of the reservoirs for persistent infection.

Pretreatment with restriction enzyme or bovine serum albumin for effective PCR amplification of Epstein-Barr virus DNA in DNA extracted from paraffin-embedded gastric carcinoma tissue

An association between Epstein-Barr virus (EBV) and gastric carcinoma has been studied through the EBV genome present in the carcinoma cells. Recently, we found that EBV DNA in paraffin-embedded gastric carcinoma tissue was detected effectively by PCR after pretreatment of the extracted DNA with a restriction enzyme, BamHI or EcoRI. Here, we show that the PCR amplification was also enhanced by pretreatment of the DNA with other restriction enzymes or with bovine serum albumin and several other proteins. Treatment with these proteins may remove a PCR inhibitor(s) in the DNA samples extracted from the paraffin blocks.

Correlation between the detection of viral DNA by the polymerase chain reaction in peripheral blood leukocytes and serological responses to human herpesvirus 6, human herpesvirus 7, and cytomegalovirus in renal allograft recipients

Diagnosis of significant infections by human herpesvirus 6 (HHV6) and 7 (HHV7) in transplant patients has proved difficult because both viruses are ubiquitous and can cause persistent infections in their hosts. The significance of viral DNA detected in peripheral blood leukocytes (PBLs; DNAemia) by PCR is therefore unclear. The interpretation of serological results is complicated by the fact that both primary and secondary infections with other herpesviruses may be associated with a concurrent antibody response to HHV6. Fifty-four renal allograft recipients were studied prospectively and their serological response to HHV6, HHV7 and CMV were compared with the detection of viral DNAemia from the homologous and heterologous viruses. Serum and heparinished blood samples were collected prospectively from 54 renal allograft recipients. DNA was extracted from PBLs and tested for the presence of HHV6, HHV7 and CMV DNA by PCR. Antibodies to HHV6 and HHV7 were measured by an indirect immunofluorescence test and to CMV by an anticomplement immunofluorescence (ACIF) test. CMV IgM antibodies were detected by a commercial enzyme immunoassay. CMV and HHV7 DNAemia were each significantly associated with serological responses to the homologous virus but no such association was found for HHV6 DNAemia. However, patients with consecutively positive DNAemia to any of the viruses (including HHV6) were more likely to have a homologous serological response. Patients who had detectable CMV IgM without a concurrent rise in CMV antibodies were significantly less likely to have CMV DNAemia (odds ratio = 0.16; 95% CI 0.02-0.9). CMV IgM antibodies may be associated with HHV6 or HHV7 DNAemia (odds ratio 2.3; 95% CI 0.5-15). This serological profile may reflect a crossreactive response to HHV6, HHV7 or other herpesviruses. CMV IgM should not be used in isolation for the diagnosis of CMV infection or disease in this group of patients.

Detection of Mycobacterium avium subsp. paratuberculosis in ovine tissues and blood by the polymerase chain reaction

A direct polymerase chain reaction (PCR) test was applied to DNA extracted from blood, liver, ileocecal lymph node and ileum from twelve ewes in poor condition with histologically confirmed paratuberculosis and ten clinically normal sheep which had no evidence of paratuberculosis. The assay was compared with four serological tests: complement fixation test (CFT), gel diffusion test (AGID) and two enzyme-linked immunosorbent assays (ELISA). The PCR detection rate of Mycobacterium avium subsp. paratuberculosis, when results of single tests were interpreted in duplicate, was 72% for ileocecal lymph node, 90% for liver, and 100% for ileum in sheep with confirmed paratuberculosis. A single PCR test detected the target DNA in 66% of 0.5 ml blood samples. Sensitivities of serological tests compared with histological diagnosis were: 33% for CFT, 66% for AGID, 75% for the Central Animal Health Laboratory (CAHL) ELISA, and 83% for the 'modified' Commonwealth Serum Laboratories (CSL) ELISA. The PCR assay gave no positive reaction in samples collected from 10 sheep considered to be free of paratuberculosis. Similarly, all four serological tests were also 100% specific. The results raise some hope for the development of a PCR-based test using liver biopsy specimens, or possibly blood, in the diagnosis of paratuberculosis in sheep.

Chronic variant of myocarditis associated with hepatitis C virus infection

BACKGROUND

Although molecular biological studies suggest a pathogenic link between enterovirus infection and dilated cardiomyopathy (DCM), the frequency of detection of enteroviral RNA is not consistently high in myocardial tissue from patients with DCM. A recent study has suggested that hepatitis C virus (HCV) may also be involved in the development of DCM.

METHODS AND RESULTS

We performed genomic analysis for HCV in three patients with chronic active myocarditis. In all three patients, serum aminotransferase activities remained within normal ranges until the terminal stage of heart failure. At necropsy, all three livers showed evidence of tissue damage caused by chronic congestion, and one liver had evidence of chronic hepatitis. Routinely processed, paraffin-embedded tissue blocks of myocardium and liver were analyzed. Renal specimens were also analyzed to exclude the possibility of myocardial contamination with HCV material from the circulating blood. RNA extracted from the heart, liver, and kidney was subjected to strand-specific reverse transcription and amplified by semi-nested polymerase chain reaction. The target nucleotide sequence was a 178-bp fragment of the highly conserved 5'-noncoding region. Both positive- (genomic) and negative-strand RNA (replicative intermediates) were present in myocardial and liver tissue samples from all three patients. However, negative-strand RNA was undetectable in renal tissue from one patient.

CONCLUSIONS

These findings suggest that HCV replicated in myocardial tissue of these patients with myocarditis. Thus, HCV infection may contribute to the development of this unusual form of myocarditis.

Feasibility of archival non-buffered formalin-fixed and paraffin-embedded tissues for PCR amplification: an analysis of resected gastric carcinoma

Although several factors affecting the sensitivity of polymerase chain reaction (PCR) amplification from formalin-fixed tissues have been investigated mostly by experiments, the feasibility of archival formalin-fixed, paraffin-embedded tissue samples stored in pathology departments for PCR amplification has rarely been examined directly. Thus, the feasibility of 74 archival unbuffered 10% formalin-fixed, paraffin-embedded tissues for PCR amplification with primers producing a 190 b.p. DNA segment of p53 exon 5 was investigated. Fixation time was the critical factor influencing the sensitivity of PCR amplification. All (6/6) of the samples fixed for only 1 day, 44% (7/16) of the samples fixed for 2-3 days and 14% (4/28) of the samples fixed for 4-6 days showed successful amplification, while no amplification was obtained for the samples fixed for 7 days or more. The peak size of DNA extracted from the archival tissues decreased as the fixation time became longer. Experiments using xenografted tumor tissues fixed for various times showed longer permissible fixation time; up to 9 days of fixation, decreasing amounts of PCR products were obtained while no amplification was obtained for the samples fixed for 12 days or more. The time in paraffin seemed to be a minor factor for PCR amplification since all of the 1 day fixation samples, including those that had been embedded for up to 5 years, resulted in efficient amplification. The size of the amplified DNA segments, however, could be another factor influencing the sensitivity of amplification because even the 1 day fixation samples showed less amplification of 345 b.p. DNA compared with those of 167 and 262 b.p. DNA. Additionally, a point mutation was detected in the amplified p53 products from archival tissues using a non-isotopic method, temperature gradient gel electrophoresis. In conclusion, archival tissue samples that had been fixed immediately for only up to 1 day were constantly available for PCR amplification of approximately 200 b.p. DNA segments, suggesting that surgical specimens should be subjected to cutting and paraffin embedding just after 1 day or less fixation for subsequent use in PCR amplification.

"Cytomegalovirus disease" in renal allograft recipients: is human herpesvirus 7 a co-factor for disease progression?

Fifty-six renal allograft recipients were studied prospectively for 3 months or longer after transplant. The polymerase chain reaction (PCR) was used to screen peripheral blood leucocyte (PBL) specimens for CMV, human herpesvirus 6 (HHV6) and human herpesvirus 7 (HHV7) DNA (DNAemia) in 67 healthy controls and in serial (fortnightly) PBL specimens from the 56 allograft recipients. None of the healthy controls had detectable CMV DNAemia, although HHV6 and HHV7 DNAemia was found in 7% and 9% of individuals respectively. In contrast, DNAemia due to CMV, HHV6 and HHV7 was found in 50%, 36% and 39% of patients respectively, at some time during the post-transplant period. Of the 28 patients who had CMV DNAemia, eight developed "CMV disease". The risk of progression to "CMV disease" was increased in patients with concurrent DNAemia to all three viruses (relative risk 3.7; 95% CI 1.3-10.5). The relative risk of "CMV disease" for patients with concurrent CMV and HHV7 was also increased (RR = 3.5; 95% CI = 1.1-11.6), while the association between CMV and HHV6 was inconclusive (RR = v2.1; 95% CI = 0.7-6.6). The first 26 patients recruited to the study also had serial serum samples tested for antibody responses to the three viruses. "CMV disease" was associated with rising antibody titres to HHV7 (Fisher's exact test, P = 0.02), and weakly so with HHV6 (P = 0.07). It is concluded that in patients with CMV DNAemia, concurrent infection/reactivation HHV7 (and possibly HHV6) is associated with an increased risk of progression to "CMV disease".

PCR analysis of hepatitis B virus DNA in paraffin-embedded liver tissue from patients with chronic liver disease

We described a nested polymerase chain reaction protocol to detect hepatitis B viral DNA in paraffin-embedded liver tissue and tried to determine whether this virus was associated with non-B chronic liver disease. Fifty-five samples were obtained from 28 patients with B, and 27 patients with non-B chronic liver disease (35 cirrhosis, 4 hepatocellular carcinoma and 16 chronic hepatitis). The two sets of primers amplify a sequence located in a conserved polymerase/surface region of the viral genome. Reaction products were analysed using a nonisotopic hybridization method. None of the 27 (0%) seronegative samples and 20 of the 28 (71%) seropositive specimens were positive for hepatitis B virus DNA. There were 4 false negatives in which beta-globin PCR was positive. Although its sensitivity is reduced in formalin-fixed paraffin-embedded tissue, nested PCR allows rapid detection of HBV DNA sequences and can be a useful tool if no frozen tissue is available.

Amplification of plasmid and chromosome Chlamydia DNA in synovial fluid of patients with reactive arthritis and undifferentiated seronegative oligoarthropathies

OBJECTIVE

To investigate the hypothesis that whole bacteria might be found in the joints of patients with Chlamydia-associated reactive arthritis.

METHODS

The presence of 2 plasmid- and 2 chromosome-specific sequences of Chlamydia DNA was investigated by amplification with the polymerase chain reaction, in synovial fluid (SF) samples from 71 patients with various arthropathies.

RESULTS

Chlamydia DNA was found in SF samples from 22 patients.

CONCLUSION

Whole chlamydiae are likely present in the SF of patients with Chlamydia-associated reactive arthritis.

HLA typing for DR3 and DR4 using artificial restriction fragment length polymorphism PCR from archival DNA

AIM

To develop polymerase chain reaction based artificial restriction fragment length polymorphism (artificial RFLP PCR) assays for DR3 and DR4 alleles of the multiallelic DRB1 locus and to apply them to paraffin wax embedded archival material.

METHODS

Sixty five samples from DRB1 typed cell lines were analysed using the artificial RFLP PCR method to determine the specificity and sensitivity of the system.

RESULTS

The artificial RFLP PCR method for typing the DRB1 locus showed 100% accuracy in the 65 samples previously typed using allele specific PCR and serology. The samples included 18 combinations of alleles that included DR3, 18 that included DR4, four that were DR3/DR4 heterozygotes, and 10 samples that were neither DR3 nor DR4. Typing of 10 paraffin wax embedded samples using artificial RFLP PCR was in complete agreement with previous typing at the DRB1 locus.

CONCLUSION

The application of artificial RFLP PCR for the analysis of multiallelic loci, such as those of the HLA system, in archival DNA samples has been achieved. Artificial RFLP PCR is a robust, easily implemented, non-isotopic system and may be useful for large retrospective studies.

Use of neuropathological tissue for molecular genetic studies: parameters affecting DNA extraction and polymerase chain reaction

Nuclear and mitochondrial DNA were extracted from gray matter of human cerebral cortex which had either been formalin-fixed and embedded into paraffin or stored in formalin for up to 26 years. Extraction conditions were optimized for proteinase K digestion, i.e., enzyme concentration, digestion temperature and incubation time. Using the polymerase chain reaction (PCR), DNA was successfully amplified from archival material and sequenced employing a direct nonradioactive cycle sequencing protocol. In general, tissue embedded into paraffin following brief fixation in formalin gave good quantitative results, i.e., up to 1 microgram DNA/mg tissue were extracted. This yield was at least one order of magnitude higher than that obtained with tissue stored in formalin. However, paraffin-embedded neuropathological material was found to contain an as-yet-unidentified PCR inhibitor, and a deleterious effect of long-term fixation in unbuffered low-grade formalin was clearly detectable. Importantly, both paraffin-embedded tissue blocks and human brain that had been stored in formalin for many years yielded DNA sufficient for qualitative analysis. The implications of these findings for the use of neuropathological material in molecular genetic studies are discussed.

Detection of reactivation and size variation in the regulatory region of JC virus in brain tissue

AIMS

To develop a sensitive and specific polymerase chain reaction (PCR) based system for detecting genomic variation in JC virus. To apply this system to formalin fixed, paraffin wax embedded brain tissue from patients with and without progressive multifocal leucoencephalopathy (PML).

METHODS

A pair of primers (JC1 and JC2) were designed to be complementary to the early and late regions of JC and BK polyomaviruses, respectively. A third primer (JC3), internal to JC1 and JC2, was designed to be specific for JC virus. The specificity of JC3 was investigated by amplifying plasmids with BK or JC virus genomes. Sensitivity was estimated by titration of a plasmid containing JC virus genome. Seven brains from patients with PML (PMLB) and 30 from patients without PML (non-PMLB) were amplified using JC1 and JC2, followed by JC1 and JC3. Amplification of the beta globin gene was used as an amplification control.

RESULTS

Amplification with JC1 and JC2 was common for JC and BK viruses, but with JC1 and JC3 it was specific for JC virus. The sensitivity of the system was 25 copies of JC plasmid per 10 microliters of digested tissue. Five out of seven PMLB and 28 of the 30 non-PMLB amplified for beta globin, but only the PMLB gave a signal with polyoma primers. Hypervariation of the length of the regulatory region of the JC isolates in the PML tissues was consistent with the presence of multiple strains of JC.

CONCLUSIONS

Variation in the regulatory region of JC virus can be specifically and sensitively detected from routinely processed, paraffin wax embedded brain tissue. Variation in the regulatory region is common in PML derived JC strains, but JC virus was not detectable in non-PMLB tissue.

Geographical variation in prevalence of hepatitis B virus DNA in HBsAg negative patients

AIMS--To study the geographical variation of the prevalence of hepatitis B virus (HBV) DNA in hepatitis B surface antigen (HBsAg) negative subjects. METHODS--A nested polymerase chain reaction (PCR) assay was used to amplify the core region of HBV. The assay was able to detect 10 molecules of a full length HBV plasmid. RESULTS--When applied to HBsAg negative paraffin wax embedded liver samples from Italy, Hong Kong, and the United Kingdom, a geographical variation in the prevalence of HBV-DNA positivity was noted. Two of 18 (11%) of Italian samples and 2/29 (6.9%) of Hong Kong samples were positive for HBV-DNA while none of the 70 cases from the United Kingdom was positive by nested PCR. Contamination by plasmid DNA was excluded using a novel method based on heteroduplex formation. One HBV-DNA positive case had idiopathic chronic active hepatitis, but the diagnoses in the other three HBV-DNA positive cases did not suggest any aetiological connection between HBV-DNA positivity and liver pathology. CONCLUSIONS--HBV-DNA could be detected in the liver tissues of a proportion of HBsAg negative subjects. The prevalence of such cases is related to the endemic rate of a geographical region. The use of HBV PCR on paraffin wax embedded tissues will be valuable for future studies on the molecular epidemiology of HBV.

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

Polymerase chain reaction is a highly sensitive technique for the detection of hepatitis B virus-DNA and hepatitis C virus-RNA in serum, liver tissue, and peripheral mononuclear blood cells. In chronic hepatitis B, it is particularly useful for identification of infectious subjects who are hepatitis B surface antigen positive and anti-hepatitis B e antigen antibody-positive, and for follow up of hepatitis B virus infections in liver transplantation programmes. Polymerase chain reaction detection of hepatitis C virus-RNA in serum may be the only means of confirming acute hepatitis C infection and also of identifying viraemia in the chronic disease, particularly in anti-hepatitis C virus antibody-negative individuals. It can also be used for direct evaluation of mother to child hepatitis C virus transmission. As in hepatitis B, polymerase chain reaction can be used for monitoring reinfection with hepatitis C virus after liver transplant, and has proved invaluable in identification of different hepatitis C virus genotypes. The efficacy of antiviral treatment can also be monitored using polymerase chain reaction. Polymerase chain reaction has thus shown numerous advantages for disease detection and monitoring despite the limitations imposed, for example, by possible contamination problems and semiquantitative evaluations.

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.

Detection of hepatitis B pre-core mutant by allele specific polymerase chain reaction

AIM

Development of a specific polymerase chain reaction (PCR) assay for detection of the pre-core, stop codon, mutant of hepatitis B virus (HBV).

METHODS

PCR primers, specific at the 3'-end for nucleotide 1896 of either the pre-core, stop codon, mutant or wild type HBV, were synthesised using published sequence data. Positive control templates for both types of virus were synthesised by the PCR, incorporating sequences specific for each virus type at the appropriate position. These templates were used to optimise the specificity of the procedure. Formalin fixed, paraffin wax embedded human tissue from acute or fulminant HBV hepatitis from Hong Kong or Oxford was then investigated for presence of mutant or wild type virus. The HBV DNA was amplified from this tissue using a two step procedure, with an initial amplification phase followed by a second diagnostic phase on optimally diluted target DNA.

RESULTS

Specific detection of mutant or wild type HBV was achieved. An important factor in determining specificity was the temperature of annealing, 70 degrees C proving to be highly specific. To overcome the inherent variation of target copy number in clinical samples and to provide an intrinsic positive control, it was important to generate and standardise the amount of target HBV used for the specific PCR. Two cases of fulminant hepatitis and four cases of acute hepatitis from Hong Kong, and one case of fulminant hepatitis from Oxford, contained only wild type HBV, with no evidence of a mutant virus.

CONCLUSION

This method can be applied to FFPE tissues. It is rapid, non-radioactive, and specific for the stop codon mutation at nucleotide 1896 of HBV. Preliminary investigation of a small number of cases of fulminant hepatitis from Oxford and Hong Kong showed only wild type virus. The result differs from results published from Japan and Israel.

Point mutations in the Ha-ras oncogene are detectable in formalin-fixed tissues of oral squamous cell carcinomas, but are infrequent in British cases

Oncogene expression in human neoplasia has been examined extensively in the past decade. More recently the advent of the polymerase chain reaction (PCR) has facilitated studies of oncogenes and other DNA structures. Those few studies which have so far searched for oncogene changes in oral cancer have utilized frozen specimens. We report here an adaptation of the PCR technique applicable to DNA extracted from archival specimens. Our data complement recent findings that Ha-ras mutations are infrequent in oral squamous cell carcinomas among white caucasoid populations.

Improved sensitivity of the polymerase chain reaction for detection of Toxoplasma gondii in biological and human clinical specimens

The aim of the present study was to improve the sensitivity of the polymerase chain reaction for detection of Toxoplasma gondii in biological and clinical specimens. Using a pair of primers amplifying a 634 bp fragment of the B1 gene of this parasite, it was possible to detect ten parasites in 100 microliters of sample suspensions containing a high concentration of concomitant host cells. A comparison of different DNA purification methods indicated that cell-rich clinical specimens intended for use as samples for the polymerase chain reaction should be digested with proteinase K prior to DNA amplification. By using the described sample preparation methods and the polymerase chain reaction, Toxoplasma gondii DNA was demonstrated in ten of 52 clinical specimens of patients with clinical or serological indications of toxoplasmosis.

Polymerase chain reaction detects hepatitis B virus DNA in paraffin-embedded liver tissue from patients sero- and histo-negative for active hepatitis B

The polymerase chain reaction (PCR) was used to analyse tissues from paraffin blocks of liver needle biopsies retrospectively. Biopsies of 29 patients with proven HBsAg and HBcAg expression in liver tissue and of 8 healthy volunteers served as positive (group 1) and negative tissue controls (group 2), respectively. These were compared with 16 patients with proven HBsAg expression in liver but lack of HBcAg (group 3), with 23 patients with anti-HBc as the only hepatitis B virus (HBV)-related marker (group 4) and with 21 patients with liver disease and without HBV markers in tissue or serum (group 5). PCR detected HBV sequences in all cases of the positive control group and in 94% of group 3, in 65% of group 4, and in 71.4% of group 5, whereas all healthy volunteers were negative. Our data show that PCR is able to detect HBV-DNA sequences in virtually all patients with active viral antigen expression but also in a high proportion of hepatitic patients who are silent for active HB but may or may not show signs of a contact with the HBV. Thus, PCR for HBV-DNA in paraffin sections might become a useful tool for identifying patients carrying HBV-DNA but not expressing HBV antigens.

Heteroduplex formation as a means to exclude contamination in virus detection using PCR

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Direct polymerase chain reaction test for detection of Helicobacter pylori in humans and animals

We designed a polymerase chain reaction (PCR) for amplifying the Helicobacter pylori gene encoding 16S rRNA. Primers for the specific detection of H. pylori were designed for areas of the 16S rRNA gene in which there is the least sequence homology between H. pylori and its closest relatives. The specificity of detection was confirmed by ensuring that the primers did not amplify DNA extracts from the campylobacters H. cinaedi, H. mustelae, and Wolinella succinogenes, which are the closest relatives of H. pylori, as determined by 16S rRNA sequencing. Serial dilution experiments revealed the detection of as little as 0.1 pg of DNA by PCR and 0.01 pg by nested PCR. H. pylori DNA was detected successfully in clinical paraffin-embedded and fresh gastric biopsy specimens from patients positive for the bacterium and also in fecal suspensions seeded with the organism. The DNA from the nonculturable coccoid form of H. pylori was also identified by the primers. Universal primers designed for highly conserved areas on the 16S rRNA gene enabled large amplification products to be produced for direct sequencing analysis. Gastric bacteria resembling H. pylori have been isolated from animals. DNA of these animal gastric bacteria amplified with H. pylori-specific primers yielded PCR products identical to those from human isolates of H. pylori, as confirmed by the use of a 20-base radiolabelled probe complementary to an internal sequence flanked by the H. pylori-specific primers. The results of PCR amplification and partial 16S rRNA gene sequence analysis strongly support the contention that the gastric organisms previously recovered from a pig, a baboon, and rhesus monkeys are H. pylori.

Removal of inhibitor(s) of the polymerase chain reaction from formalin fixed, paraffin wax embedded tissues

A problem associated with use of the polymerase chain reaction to amplify specific DNA fragments from formalin fixed, paraffin wax embedded tissues is the not infrequent failure of amplification. One possible reason for this could be the presence of inhibitor(s), which interfere with the activity of the reaction. It has been shown that such inhibitor(s) exist when amplifying the human beta globin gene (which exists in human genomic DNA as a single copy gene) from routine clinical samples. A variety of methods to remove such inhibitor(s) were investigated. The results indicate that inhibitor(s) are removed by proteinase K digestion, followed by purification with phenol/chloroform, and centrifugation through a Centricon-30 membrane (30,000 molecular weight cut off). Other factors, including the length and concentration of the DNA sequence to be amplified, can also affect amplification.

Inhibitory effects of urine on the polymerase chain reaction for cytomegalovirus DNA

The inhibitory effects of urine samples taken from neonates and older children, some of which were known to be infected with cytomegalovirus, on the polymerase chain reaction (PCR) were investigated. Urea was the major inhibitory component of urine and inhibited the PCR at a concentration of more than 50 mM. Urine samples from older children were more inhibitory than those from neonates. This correlated with the higher concentration of urea generally found in urine samples from older children compared with neonatal urines. Two of 13 neonatal urine samples, however, were inhibitory despite low urea concentrations--presumably due to metabolites derived from parenteral nutrition. The inhibitory effects of urine were effectively removed by simple dialysis or ultrafiltration. The sensitivity and specificity of PCR for detecting cytomegalovirus DNA in urine were further improved by using "nested" primers and a modified PCR protocol entailing the use of reduced reactants in the first 20 cycles of a two-stage 50 cycle PCR.

Short PCR product yields improved by lower denaturation temperatures

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Simplified procedures for applying the polymerase chain reaction to routinely fixed paraffin wax sections

The polymerase chain reaction was applied to the analysis of DNA contained in archival paraffin wax embedded material. DNA suitable for the reaction was obtained from these tissues by simple extraction methods, without previous dewaxing of tissue sections. When compared with unfixed material, the reaction efficiency was compromised, so that an increased number of amplification cycles were required to produce equivalent amounts of amplified product. This in turn led to an increase in amplification artefacts, which can be minimised by a simple modification of the standard reaction. Amplification of relatively large DNA fragments was not always successful, and it seems prudent to bear this in mind when designing oligonucleotide primers which are to be used for the amplification of archival material. The efficiency of the procedure can be improved by dividing the amplification cycles into two parts: this reduces the amount of reagent needed, is relatively simple and inexpensive, and can be performed in one working day.

High quality of DNA retrieved for Southern blot hybridization from microwave-fixed, paraffin-embedded liver tissues

To overcome the degradation problem encountered in DNA extracted from formalin-fixed, paraffin-embedded tissue blocks, several methods of tissue fixation were examined in order to improve the quality of the DNA recovered for use in nucleic acid analysis. The fixation methods included formalin fixation alone, alcohol fixation alone, and microwave fixation with tissues immersed in phosphate-buffered saline (PBS), alcohol, or formalin. Unfixed fresh frozen tissue served as the control. Using hepatitis B virus (HBV) DNA sequences and the type I human procollagen gene as markers and liver tissue as a target, microwave fixation, with formalin omitted, not only preserved the DNA very well, but also the labile viral antigen. Both high molecular weight-integrated and free-form HBV DNAs were well preserved, and suitable for polymerase chain reaction and Southern blot analysis. The restriction enzyme fragment pattern of DNA recovered from these paraffin blocks was identical to that of unfixed fresh frozen tissue. Microwave fixation also preserved the labile preS2 epitope of the hepatitis B surface antigen (HBsAg) considerably better than formalin. These results suggest that microwave fixation is superior to routine formalin fixation for the preservation of excellent quality of genomic and viral DNAs for nucleic acid hybridization analysis. Alcohol, often used for nucleic acid purification, was also a good fixative for preserving DNA and the antigenicity of the labile antigen, especially when carried out in combination with microwave fixation.

The polymerase chain reaction: basic methodology and applications

The "polymerase chain reaction" (PCR) is a high-power molecular biology technique allowing in vitro enzymatic amplification of a given DNA sequence. This exponential amplification can reach 10(7)-10(9), even a single DNA molecule can be detected. Also the use of non-radioactive probes, considered to be less sensitive than their radioactive counterparts, is possible for the molecular hybridization, to retain a high level of sensitivity. PCR is defined as a "free bacteria" cloning technique, which has many applications in fundamental research and in the clinical analysis of genetic disease, infectious diseases and cancers. Thus PCR is a revolutionary method which is capable of greatly stimulating scientific research and modifying the diagnostic area in the near future.

The polymerase chain reaction: miracle or mirage? A critical review of its uses and limitations in diagnosis and research

Since publication of the polymerase chain reaction (PCR) technique in 1985 (Saiki et al. Science 1985; 230: 1350-1354), there has been an explosion of reports on its use in medicine and science. We critically review its use both as a diagnostic technique and as a research tool, and show the pathologist how to evaluate PCR data and how to avoid the pitfalls of overinterpretation. We discuss the value of PCR in the characterization of genetic defects, prenatal diagnosis, carrier testing, HLA typing, detecting micro-organisms, identifying activated oncogenes, and in the characterization of leukaemias and lymphomas, and summarize the main applications in biomedical research.

The 14;18 translocation in European cases of follicular lymphoma: comparison of Southern blotting and the polymerase chain reaction

The 14;18 chromosomal translocation is widely recognized as a cytogenetic abnormality associated with follicular lymphomas, but estimates of its frequency in this type of lymphoma vary widely from less than 50% to almost 90%. Furthermore, no extensive data have been published on the frequency of t(14;18) in European cases of follicular lymphoma. Lymph nodes from 51 patients with follicular lymphomas obtained from two European centres (Oxford and Copenhagen) were examined for the presence of this translocation. Southern blotting and the polymerase chain reaction (PCR) were used in 26 cases and the PCR alone in 25 cases (from which only degraded DNA or formalin fixed samples were available). DNA probes capable of detecting rearrangement at both the major and the minor breakpoint regions were employed. We could detect t(14;18) in only 21 out of 51 cases (41%). However, a review of the literature showed that comparable results have been obtained previously using both cytogenetic and molecular biological techniques and our results support the view that the global incidence of t(14;18) in follicular lymphoma is no greater than 70%. Furthermore, this study has indicated that the PCR is a reliable method for identifying t(14;18) when only formalin-fixed paraffin-embedded tissue or degraded DNA is available.