Immunohistochemical detection of the human herpes virus 8 (HHV8) latent nuclear antigen-1 in Kaposi's sarcoma

AIMS: The molecular genetics of the human herpes virus 8 (HHV8) has now been characterised and the virus appears to be important in the pathogenesis of Kaposi's sarcoma (KS). This study attempts to determine the rate of HHV8 infection in KS in an Australian cohort. METHODS: Routine streptavidin-biotin-peroxidase immunostaining with diaminobenzidine was performed on paraffin-embedded archival tissues of 37 KS cases using a murine monoclonal antibody directed against the C-terminus of the latent nuclear antigen-1 molecule of HHV8 (clone 13B10; Novocastra) at 1:50 dilution. RESULTS: Positive HHV8 nuclear staining was detected in the nuclei of the spindle cells and endothelial cells of the vascular channels in about 78% (29/37) of all cases. HHV8 staining was absent in the non-neoplastic vessels in the adjacent tissue (P=0.0001, chi(2)=44.46; chi(2)-test with continuity correction) and the negative control cases of Merkel cell carcinoma (P=0.02, chi(2)=5.07; chi(2)-test with continuity correction). HHV8 staining was detected in 80% (8/10 cases) of the patch stage, 88% (7/8 cases) of the plaque stage and 74% (14/19 cases) of the late stage. No significant difference was found between HHV8 positivity and HIV status, age, gender, tumour recurrence, multiplicity or site of the lesions. CONCLUSIONS: The latent nuclear antigen-1 of HHV8 can be detected by immunohistochemistry in the majority of human KS lesions, raising the possibility of its future potential use as an adjunct for the diagnosis of KS in problematic cases.     

Immunostaining for human herpesvirus 8 latent nuclear antigen-1 helps distinguish Kaposi sarcoma from its mimickers

We assessed the usefulness of a mouse monoclonal antibody (13B10) against human herpesvirus 8 (HHV-8) latent nuclear antigen-1 (LNA-1) in diagnosis of Kaposi sarcoma (KS) and for distinguishing it from various mimickers by studying 50 cases of KS and 53 mimickers (angiosarcoma, 15; kaposiform hemangioendothelioma, 6; spindle cell hemangioma, 3; reactive angioendotheliomatosis, 3; bacillary angiomatosis, 4; acroangiomatous dematitis, 2; microvenular hemangioma, 2; hobnail hemangioma, 2; pyogenic granuloma, 5; dermatofibroma, 8; arteriovenous hemangioma, 1; verrucous hemangioma, 1; nonspecific vascular proliferation, 1) from patients with or without acquired HIV infection. Immunohistochemical staining was performed on formalin-fixed, paraffin-embedded tissue sections. All 50 cases of KS were positive for HHV-8 LNA-1, with immunolocalization in the nuclei of the spindle cells and cells lining the primitive and thin-walled vascular channels, whereas all 53 mimickers (including 4 lesions from HIV-positive patients) tested negative. The results idicate that positive immunostaining for HHV-8 LNA- 1 exhibits high sensitivity and specificity for the diagnosis of KS and is, thus, useful for distinguishing it from the mimickers.     

PCR diagnosis of sequences of a novel human herpes virus type 8 in patients with Kaposi sarcoma in Russia

Associations of a new human herpesvirus type 8 (HHV-8) with different forms of Kaposi's sarcoma (KS) in Russia have been studied. Search for this virus genetic information has been carried out in biopsy specimens of benign and malignant tumors other than KS, and probable sites of HHV-8 latency in human body have been checked. HHV-8 sequences were detected by polymerase chain reaction (PCR). HHV-8 sequences were most often detected in idiopathic (80.6%), AIDS-associated (80%), and immunosuppressive (100%) KS. The results indicate a selective association of HHV-8 with KS. No probable sites of the virus latency were detected in peripheral blood cells of patients with KS and in the prostate of patients with chronic prostatitis. The only exception was the husband of a patient with KS: HHV-8 sequences were detected in his prostatic secretion by nested PCR.     

Colocalization of the viral interleukin-6 with latent nuclear antigen-1 of human herpesvirus-8 in endothelial spindle cells of Kaposi's sarcoma and lymphoid cells of multicentric Castleman's disease

Human herpesvirus-8 (HHV-8) also called Kaposi's sarcoma-associated herpesvirus infects spindle cells in Kaposi's sarcoma (KS) and lymphoid cells in multicentric Castleman's disease (MCD). In KS cells, HHV-8 is mainly latent with the expression of latent nuclear antigen-1 (LNA-1), whereas in MCD both lytic and latent antigens are produced by lymphoid cells. We show by immunohistochemical labeling that in KS viral interleukin-6 (vIL-6) is expressed in rare spindle cells, whereas in MCD, vIL-6 is detectable in lymphoid cells around lymphoid follicles but also within the follicular dendritic reticulum cell network. The staining of apoptotic bodies with anti IL-6 antibody suggests the achievement of a complete lytic cycle in a subset of lymphoid cells. Interestingly, in MCD, some areas contained vascular spindle cells latently infected by HHV-8 on the basis of LNA-1 expression. This finding might imply that in MCD, both vascular and lymphoid cells proliferate in response to the viral infection. Double immunostaining with anti LNA-1 and anti vIL-6 in MCD and KS identifies 2 subsets of HHV-8 infected (vascular and lymphoid) cells, some with exclusive expression of LNA-1 and some with coexpression of vIL-6 and LNA-1. This suggests that in vivo the regulation of the expression vIL-6 and LNA-1 protein varies with the cell type. In addition, the detection of infected endothelial cells in MCD may indicate that these cells belong to the reservoir for HHV-8.     

In cis inhibition of antigen processing by the latency-associated nuclear antigen I of Kaposi sarcoma herpes virus

Kaposi sarcoma Herpes virus (KSHV), also known as human Herpes virus 8 (HHV8), can persist as episome in target cells. The latency-associated nuclear antigen 1 (LANA-1) is a key component of the latency process, and may be a functional equivalent of the EBNA-1 protein of Epstein-Barr virus. EBNA-1 can subdue immune recognition by virtue of a long glycine and alanine-rich repeat, which interferes with the proteasomal degradation of EBNA-1 and in this way averts the presentation of antigenic peptides derived from it. LANA-1 contains a strongly acidic-repeat region of approximately 580 amino acids, which consists almost exclusively of aspartic acid, glutamine, and glutamic acid residues. The LANA-1 repeat is not similar to the EBNA-1 Gly-Ala-rich repeat. We demonstrate that this acidic region could inhibit antigen processing in cis. Upon transfection of expression vectors containing LANA-1-eGFP fusion genes the cells did not present an ovalbumin-derived H2K(b)-restricted CTL epitope inserted at the carboxyl terminus of the GFP reporter. Deletion of the central acidic-repeat region of LANA-1 abolished the capacity of LANA-1 to block antigen presentation. Similar to the EBNA-1-derived Gly-Ala-rich repeat, the LANA-1 repeat does not inhibit presentation in trans: co-transfection of LANA-1 expression vectors does not inhibit presentation of the ova epitope from the GFP(Ova) fusion protein. These data demonstrate for the first time that the acidic-repeat region of LANA-1 could function as an in cis acting inhibitor of antigen presentation. This may contribute to the immune evasion of cells latently infected by KSHV.     

Human herpesvirus 8 and iron staining are useful in differentiating Kaposi sarcoma from interstitial granuloma annulare

We studied 20 granuloma annulare (GA) cases (10 interstitial and 10 palisaded) and 19 Kaposi sarcoma (KS) cases (9 "early" and 10 typical). Tissue sections were stained for iron, Hale colloidal iron, human herpesvirus 8 (HHV-8), CD31, CD34, CD68, collagen IV, factor XIIIa, and MIB-1. Iron staining of dermal tissue associated with the lesion was confirmed in all KS cases and no GA cases. Immunohistochemical stains for HHV-8 were positive in all 9 cases of early KS and most cases (9/10) of typical KS. All 20 cases of GA were HHV-8-. CD31, CD34, CD68, factor XIIIa, and MIB-1 were also stained but were difficult to interpret and did not seem specific for GA or KS. Iron staining and immunohistochemical HHV-8 staining in combination were reliable markers for KS compared with interstitial GA. MIB-1 fractions of less than 5% favored a diagnosis of GA, whereas fractions greater than 10% favored a diagnosis of KS. This study provides novel data characterizing iron staining in KS and details the use of iron staining, HHV-8, and MIB-1 to distinguish KS from GA.     

Presence of human herpesvirus 8 DNA sequences in renal transplantation-associated pleural Kaposi sarcoma

OBJECTIVE: To describe one case of symptomatic skin and pleural Kaposi sarcoma (KS) associated with kidney transplantation. Diagnosis was supported by morphologic study and human herpesvirus 8 (HHV-8) detection in both tissues. Pulmonary involvement was not present. DESIGN: The presence of HHV-8 DNA sequences was proved using polymerase chain reaction (PCR), Southern blot hybridization, and in situ hybridization. SETTING: Human herpesvirus 8 is found in most KS from patients with and without the acquired immunodeficiency syndrome. Clinically significant pulmonary infiltration by KS is diagnosed uncommonly antemortem, and pleural disease is exceptional. PATIENT: A 49-year-old man who had renal transplant with immunosuppressive therapy (tacrolimus and prednisone) and developed a cutaneous KS. A pleural effusion appeared without pulmonary involvement. Both lesions disappeared when immunosuppressive drugs were suspended. Later, the pleural effusion and the cutaneous lesions reappeared. Pleural biopsy specimens showed KS infiltration. OUTCOME: The patient refused treatment and was lost to follow-up. RESULTS: The skin and pleural biopsies showed a proliferation of spindle-shaped cells positive for CD34. The HHV-8 sequences were detected by nested PCR. No amplification was detected in uninvolved skin from the patient or in peripheral blood mononuclear cells from 10 healthy individuals used as controls. The Southern blot hybridization confirmed these results. CONCLUSIONS: To our knowledge, this is the first report of HHV-8 in symptomatic pleural KS, which was probably associated with immunosuppression after kidney transplantation. The demonstration of HHV-8 DNA in biopsy material in the appropriate cells could be diagnostic when the morphologic setting is consistent with KS.     

Latency-associated nuclear antigen expression and human herpesvirus-8 polymerase chain reaction in the evaluation of Kaposi sarcoma and other vascular tumors in HIV-positive patients.

Human herpesvirus-8 (HHV-8) latency-associated nuclear antigen (LANA) is expressed in endothelial and spindle cells of nearly all Kaposi sarcomas, and the presence of this antigen in serum is strongly correlated with the risk of developing Kaposi sarcoma in immunocompromised individuals. Studies of vascular tumors occurring in the general population show LANA expression to be specific for Kaposi sarcoma. No study to date, however, has examined whether non-Kaposi sarcoma vascular tumors arising in immunocompromised patients may express LANA, possibly reflecting origin from an HHV-8-infected endothelial progenitor cell. The objective of this study was to evaluate the specificity of LANA expression for Kaposi sarcoma in immunocompromised patients by LANA immunohistochemistry and real-time polymerase chain reaction (PCR) for HHV-8. A total of 13 cases of non-Kaposi sarcoma vascular tumors (12 hemangiomas and one epithelioid hemangioendothelioma) and 24 cases of Kaposi sarcoma, all from known HIV-positive patients, were immunostained for LANA and evaluated for the presence of HHV-8 DNA by real-time PCR. LANA expression was seen in 22 of 24 (92%) of Kaposi sarcoma cases and in 0 of 13 non-Kaposi sarcoma cases. Real-time PCR detected HHV-8 in all of the Kaposi sarcoma cases and in four of the non-Kaposi sarcoma cases (all hemangiomas). LANA expression appears to be a highly sensitive and specific marker of Kaposi sarcoma in both the general population and in HIV-positive patients. This is in contrast to HHV-8 PCR, which is positive in a small subset of non-Kaposi sarcoma vascular tumors, most likely due to detection of HHV-8 within intratumoral blood mononuclear cells by the highly sensitive real-time PCR technique. For this reason, LANA immunohistochemistry is preferable to HHV-8 PCR for the evaluation of problematic vascular proliferations in HIV-positive individuals.     

Immunohistochemical studies of human immunodeficiency virus-1 in liver tissues of patients with AIDS.

A wide spectrum of hepatic lesions has been reported in AIDS, but it is not known whether the changes are related to the presence of human immunodeficiency virus type 1 (HIV-1). Therefore, we examined liver sections from 15 consecutively autopsied patients with AIDS for the presence of HIV-1 antigens p24 (core) and gp41 (envelope) by the avidin-biotin-peroxidase complex method using monoclonal antibodies. The most common histologic abnormalities noted were steatosis, portal inflammation, Kupffer cell hyperplasia, and focal hepatocellular and bile duct damage. Intra-hepatic opportunistic organisms were detected in six of 15 (40%) cases, with Mycobacterium avium-intracellulare being the commonest (four cases). Immunoreactivity for HIV-1 antigens was demonstrated in 12 of 15 cases (80%), with staining limited to Kupffer cells and other mononuclear cells characterized by a lymphoid morphology. Approximately the same number and type of cells were stained with both monoclonal antibodies and did not bear any relation to the degree of histologic abnormalities nor to the presence of opportunistic infections. The data suggest that some pathologic changes in AIDS livers are more likely the result of an indirect effect mediated by infected resident and circulating mononuclear cells than a direct cytopathic effect of HIV-1.     

Immunohistochemical evidence for human immunodeficiency virus-1 infection of liver Kupffer cells

To investigate the possibility of human immunodeficiency virus-(HIV) 1 infection of liver cells, liver samples from 17 patients with either acquired immunodeficiency syndrome (AIDS, 13), AIDS-related complex (ARC, 3), or lymphadenopathy syndrome (LAS, 1) were studied. A monoclonal antibody directed against the p24 gag HIV-1 protein was used in an immunoperoxidase assay and yielded positive results in seven out of 17 samples. Staining by anti-p24 antibody was of three types: diffuse in Kupffer cells of most samples, inside granuloma in cells that were probably histiocytes, and in some sinusoidal cells whose origin was difficult to ascertain. Attempts to locate the CD4 membrane antigen showed that it was mainly present on endothelial sinusoidal cells. These results indicate that liver cells, including Kupffer cells, might be infected by HIV-1, and that these cells might be involved in certain liver lesions observed during HIV-1 infection, particularly sinusoidal abnormalities.     

A mu-capture immunoassay for detection of human herpes virus-6 (HHV-6) IgM antibodies in human serum.

BACKGROUND: Human herpes virus-6 (HHV-6) was first isolated in 1986. It has been shown to cause exanthema subitum and has been associated with various other diseases. HHV-6 infection is widespread, and more than 90% of the population have antibodies against HHV-6 at the age of 2 years. Once acquired, the virus remains latent in the body. This makes it difficult to draw any conclusions about a causal relationship between the demonstration of HHV-6 and a specific disease. OBJECTIVES: This work was to develop a mu-capture HHV-6 IgM enzyme linked immuno sorbent assay (ELISA) for use in routine diagnosis and for wide scale patient population analysis. STUDY DESIGN: A mu-capture HHV-6 IgM ELISA was established. A total of 682 sera consisting of 585 sera from Danish blood donors and 97 sera from patients with autoimmune antibodies were analysed in the HHV-6 IGM ELISA. One hundred and ninety-two sera had earlier been analysed for total HHV-6 antibody content in a competitive ELISA, 94 sera were analysed for cytomegalovirus (CMV) IgM and 57 sera for Epstein Barr virus (EBV) antibodies, using different ELISA assays. The results for 12 primary infections with HHV-6 are also reported. RESULTS: A HHV-6 IgM optical density (OD)-ratio was calculated according to a constant positive control. An empirical cut off of 0.5 HHV-6 IgM OD-ratio was chosen (with regard to the 10 HHV-6 seroconverters), which resulted in a specificity of 97.5% of the HHV-6 IgM ELISA. Two of the three donor sera with HHV-6 IgM OD-ratios more than 1.05 had total HHV-6 antibody titers significantly above the group with IgM OD-ratios below 0.7 consisting with HHV-6 reactivation. There was no cross reactions to EBV or CMV IgM positive sera. CONCLUSION: The HHV-6 IgM ELISA seems valid to diagnose primary HHV-6 infection in particular in combination with the HHV-6 total antibody assay.     

Immunohistochemical detection of cdc2 is useful in predicting survival in patients with mantle cell lymphoma.

Recent cDNA microarray studies have reported the prognostic value of several genes in mantle cell lymphoma patients. We aimed to validate the prognostic significance of three of these genes: alpha-tubulin, cdc2, and CENP-F. The protein expression of alpha-tubulin, cdc2, and CENP-F was assessed using immunohistochemistry. Their immunoreactivity in 48 formalin-fixed/paraffin-embedded mantle cell lymphoma tumors was determined by estimating the percentage of positive cells. These results were correlated with the expression of proliferation marker Ki67 and survival. Of these 48 mantle cell lymphoma patients, 41 were men and seven were women. The median age at time of diagnosis was 64.5 years, and the overall median survival was 40 months. In benign lymph nodes, the expression of cdc2 and alpha-tubulin was restricted to the germinal centers; mantle zones were negative. Expression of CENP-F was more uniformly distributed. In mantle cell lymphoma, Ki67 significantly correlated with all three markers (P<0.05, Spearman), but only Ki67 (>50%) and cdc2 (>25%) significantly correlated with shorter survival (P<0.0006, Spearman). Of several clinical parameters examined, international prognostic index of >or=2 correlated with worse clinical outcome, and high clinical stage (ie 4 vs 相似文献   

Identification of a major latent nuclear antigen, LNA-1, in the human herpesvirus 8 genome

OBJECTIVES: Human herpesvirus 8 (HHV-8) is strongly associated with all forms of Kaposi's sarcoma (KS) and with primary effusion lymphomas (PEL). KS patients' sera are immunoreactive against discrete nuclear localizing antigens in PEL cell lines. This study sought to identify and characterize these nuclear localizing proteins. STUDY DESIGN/METHODS: KS patients' sera were used to screen a cDNA expression library derived from a PEL cell line (BCP-1) latently infected with HHV-8. RESULTS: An HHV-8-specific cDNA clone was isolated. It encoded one partial and two complete open reading frames (ORFs): ORF 73, ORF 72 (v-cyclin), and K13, respectively. The immunodominant epitope was mapped to the C-terminal domain of ORF 73. Analysis with the KS patients' sera of HEK 293 cells transfected with a clone encompassing the complete coding region of ORF 73, ORF 72, and K13 gave a nuclear immunofluorescence pattern similar to that observed in BCP-1 cells. Western blot analysis with KS patients' sera of transfected HEK 293 cells revealed an immunoreactive protein of 220 to 230 kD that was similar to that observed previously in PEL cell lines. After induction of lytic replication of HHV-8 in BCP-1 cells with n-butyrate, we observed a major reduction in the expression of an ORF 73-specific 6.6-kb mRNA, indicating that this region is under latent control. CONCLUSIONS: These data identify a region of HHV-8 encoding for a major immunoreactive latent nuclear antigen (LNA-1), analogous to the Epstein-Barr virus latent nuclear antigens.     

Cyclin D1 overexpression in AIDS-related and classic Kaposi sarcoma.

The anatomic distribution and rate of progression vary significantly between acquired immunodeficiency syndrome (AIDS)-related Kaposi sarcoma (KS) and classic KS. The reasons are unclear, but cyclin D1 overexpression is associated with tumor progression in other malignancies. Cyclin D has an important regulatory role in the progression of cell cycle at the G1-S phase due to its effect in phosphorylating the retinoblastoma gene product. Forty-one paraffin-embedded surgical specimens (31 AIDS-related, 10 classic) were examined using streptavidin-biotin-peroxidase immunohistochemistry with monoclonal antibody to cyclin D1. A scoring system based on the intensity and extent of staining was used. The correlations among cyclin D1 expression and clinicopathologic parameters were statistically analyzed. Cyclin D1 overexpression was found in 29% (12/41) of all KS cases. There was a strong correlation between cyclin D1 overexpression and pathologic stage (0% in patch stage, 13% in plaque stage, 50% in nodular stage; P = 0.0017). Classic KS lesions had a higher incidence of cyclin D1 overexpression than AIDS-related lesions (70% vs 16%, P = 0.001). Cyclin D1 overexpression was detected in 78% of the classic nodular lesions and 31% of the AIDS-related nodular lesions (P = 0.03). On multivariate analysis, negative human immunodeficiency virus status (P = 0.001) and nodular lesions (P = 0.007) were strong predictors of cyclin D1 overexpression. Age, gender, recurrence of the tumor, multiplicity, and site of the lesions hold no statistically significant association with cyclin D1 expression on multivariate analysis. In summary, cyclin D1 overexpression was more prevalent in classic lesions and more advanced nodular stage. These findings raise the possibility of a different pathogenetic mechanism in the progression of AIDS-related KS and classic KS.     

Loop-mediated isothermal amplification assay for the diagnosis of retinitis caused by herpes simplex virus-1

A loop-mediated isothermal amplification (LAMP) assay was developed for the detection of herpes simplex virus 1 (HSV-1). The specificity of the assay was tested using DNA extracted from HSV-1-infected rabbit corneal epithelium cultures, HSV-2 grown on Vero cell line, cytomegalovirus (CMV) (AD-169), varicella zoster virus (VZV) (Oka-vaccine), adenovirus, Aspergillus flavus and Staphylococcus aureus. The specificity of LAMP was confirmed by bidirectional sequencing of the amplicons. The sensitivity of the LAMP assay was tested using different concentrations of HSV-1 DNA. To evaluate the application of the LAMP assay in clinical diagnosis, we tested vitreous samples from 20 patients with suspected viral retinitis using LAMP and real-time PCR for HSV-1. The LAMP primers amplified only HSV-1 DNA; no LAMP products were detected with the DNAs of HSV-2, CMV, VZV, adenovirus A. flavus and S. aureus. The sequences of the positive HSV-1 LAMP products perfectly (99–100%) matched the HSV-1 sequences deposited in the GenBank database. LAMP is as sensitive as real-time PCR, with the lowest detection limit being 10 copies/μL of HSV-1 DNA. Of the 20 patients with suspected viral retinitis, four tested positive for HSV-1 using real- time PCR and LAMP. A 100% concordance was observed across the two methods. The LAMP assay is a rapid, highly specific and sensitive method for the diagnosis of retinitis caused by HSV-1.     

Immunohistochemical detection of proliferating cell nuclear antigen in solid human malignancies

Proliferating cell nuclear antigen (PCNA), also known as cyclin, is a cell cycle-related nuclear protein that is maximally elevated in late G1 and S phases of proliferating cells. In this study, PCNA was identified by paraffin-section immunohistochemistry in 42 of 64 solid human malignancies, and in several benign tissues known to contain proliferating cells. The PCNA-positive nuclei were randomly distributed and ranged from less than 1% (in most cases) to more than 20% of the neoplastic cells. In general, PCNA positivity correlated with mitotic activity and tumor grade. Further study is necessary to evaluate PCNA as a marker of cellular proliferation and a potential prognostic marker in human malignancy.     

High expression of the Epstein-Barr virus latent protein EB nuclear antigen-2 on pyothorax-associated lymphomas.

Pyothorax-associated lymphoma (PAL) is a rare tumor associated with long-standing tuberculous pyothorax. Most of these lymphomas are B-cell lymphomas of high-grade malignancy. Over 50 cases have been reported in Japan, but no cases have been described in Western countries. Its pathogenesis remains unknown. We studied immunohistologically the expression of Epstein-Barr virus- (EBV) encoded latent gene products, EB nuclear antigen-2 and LMP-1, in four cases of PAL. Fifty B-cell lymphomas unrelated to pyothorax, and five EBV-bearing lymphoblastic tumors produced in severe combined immune deficient mice (severe combined immune deficient-EBV+ tumors) were also studied as controls. Marked expression of EB nuclear antigen-2 was demonstrated on all four PALs. LMP-1 was also present in all cases, but both the staining intensity and the number of stained cells remained less than on severe combined immune deficient-EBV+ tumors. Neither EB nuclear antigen-2 nor LMP-1 was observed in the 50 control B-cell lymphomas. Additional molecular genetic analysis revealed that EBVs are incorporated into each PAL clonally. These results confirm the definite association of EBV with PALs, although the significance of weak expression of LMP-1 awaits further study.     

Analysis of human herpes virus-6 genomes in lymphoid malignancy in Japan.

Ninety cases of malignant lymphoma and 56 cases of reactive lymphadenopathy were studied using Southern blot analysis and the polymerase chain reaction to identify human herpes virus-6 (HHV-6) DNA. This was detected in cases of lymphoid malignancy at a rate which ranged from 50.0% to 68.8%. There were no differences in rates for different types of lymphoid malignancies. Herpes virus-6 DNA was detected by PCR in lymphoid malignancies less frequently than in reactive lymphadenopathies. It was not detected in lymphoid malignancies using Southern blotting. These results suggest that HHV-6 DNA was not related to lymphoid malignancy and was only a latent infection of non-neoplastic cells in tumour tissue.