Absence of detectable human herpesvirus 8 in the semen of human immunodeficiency virus-infected men without Kaposi's sarcoma

The prevalence of human herpesvirus 8 (HHV-8)/Kaposi's sarcoma (KS)-associated herpesvirus was investigated in the semen of 99 human immunodeficiency virus (HIV)-infected men (median CD4 cell count, 357/mm3) by use of a polymerase chain reaction (PCR) assay capable of detecting <10 copies of HHV-8 DNA. Of the subjects, 95 (96%) self-identified as men who have sex with men (MSM), and 3 had a history of clinical KS. Seminal cell specimens were negative for HHV-8 in 98 subjects. None of the 26 without KS (27.1% of 96 tested) who were seropositive for HHV-8 by IFA for latency-associated nuclear antigens had HHV-8 detected in their semen. The only subject with any evidence for seminal HHV-8 DNA was seropositive for HHV-8 and had active KS. HHV-8 was detected in 10 (10.4%) of 96 peripheral blood mononuclear cell specimens. The prevalence of HHV-8 DNA by PCR in semen of HIV-infected MSM without KS is low.     

Human herpesvirus 8 infection occurs following adolescence in the United States

Most recent evidence suggests that human herpesvirus 8 (HHV-8) infection is restricted to persons with Kaposi's sarcoma (KS) or to persons who may subsequently develop KS. To accurately determine the prevalence of infection in the United States, children and adults with AIDS were examined for evidence of HHV-8 infection to see whether HHV-8 (like other herpesviruses) would be readily detected in immunosuppressed persons. By use of nested polymerase chain reaction, DNA specific for HHV-8, Epstein-Barr virus, and cytomegalovirus was detected in blood leukocytes from 0, 26 (51%), and 9 (18%), respectively, of 51 children. Similarly, HHV-8-specific antibodies were not detected in analyses of sera from the children. By contrast, HHV-8 DNA was detected in 9 (27%) of 33 adult AIDS patients without KS. These findings suggest that the pattern of transmission of HHV-8 in the United States differs from that of other herpesviruses in that primary infection occurs predominantly in adults.     

Human herpesvirus-8: detection of novel herpesvirus-like DNA sequences in Kaposi's sarcoma and other lesions

Kaposi's sarcoma (KS) is a malignancy suspected of having an infectious etiology. Unique viral DNA sequences were recognized in KS lesions, using a novel technique that identifies small differences between two complex genomes. The virus had homology with the herpesvirus family, especially Epstein Barr virus (EBV), yet it was distinct from the known herpesviridae, and was appropriately named human herpesvirus 8 (HHV-8) or Kaposi's sarcoma-associated herpesvirus (KSHV). HHV-8 DNA sequences were present in AIDS-associated KS, classic KS, African endemic KS, Mediterranean KS, iatrogenic KS, and KS in homosexual men without HIV infection. HHV-8 DNA sequences were also present in peripheral blood mononuclear cells (PBMC) of KS+ patients; body-cavity-based lymphomas in HIV positive patients without KS; and in tissue from a number of malignant and non-malignant lesions in patients without HIV infection. The role of HHV-8 in KS and other malignancies is not known. Viruses are notoriously trophic for lesional tissue. Therefore, in order to determine the role of HHV-8 in KS pathogenesis, HHV-8 needs to be isolated and shown to induce immortalization in a suitable system. Regardless of its role in KS, another human herpesvirus has been discovered, and the extent of its pathogenicity needs to be uncovered.     

Detection of human herpesvirus 8 DNA sequences in tissues and bodily fluids

Human herpesvirus 8 (HHV-8) has been proposed as a sexually transmitted etiologic agent of Kaposi's sarcoma (KS). In this study, by use of a sensitive polymerase chain reaction assay, HHV-8 DNA was detected in the skin lesions (92%), normal skin (23%), peripheral blood mononuclear cells (PBMC) (46%), plasma (7%), saliva (37%), and semen (12%) but not stool samples from KS patients. The average number of HHV-8 copies per microgram of positive target DNA was 64, 000, 9000, 40, 33,000, and 300 for skin, PBMC, plasma, saliva, and semen samples, respectively. Only 1 non-KS donor sample, of saliva, was positive for HHV-8. Sequencing showed 5% divergence among HHV-8 strains. The data suggest that saliva may be more important than semen or stool in the sexual transmission of HHV-8. The relatively high prevalence of HHV-8 in PBMC raises the question as to why there is no evidence for bloodborne virus transmission.     

Detection of human herpesvirus 8 in patients with Kaposi's sarcoma or Castleman's disease associated with AIDS

A new herpesvirus provisionally termed as KSHV or HHV-8 has been detected in lesions from AIDS-based Kaposi's sarcoma (KS) and from other KS clinical forms, and also in other tumors such as body cavity-based lymphomas or Castleman's disease (CD). We have assessed the presence of this novel herpesvirus in specimens from patients diagnosed with either AIDS and KS or AIDS and CD. DNA samples from skin lesions and peripheral blood obtained from 8 patients diagnosed with AIDS, seven with KS and one with multicentric CD were analyzed; skin specimens and peripheral blood samples from volunteer blood donors or from KS and CD free HIV seronegative patients were used as controls. Detection of the virus was done by PCR amplification of KS330 region, one of the HHV-8 sequences first reported. All skin lesions analysed tested positive for KS330; peripheral blood samples from 5 of the patients, including the one diagnosed with CD, showed also the virus sequence. All skin specimens and peripheral blood samples from controls were negative. From our results it can be concluded that the novel herpesvirus HHV-8 can also be detected in patients with AIDS-associated KS and AIDS-associated CD in Spain.     

Simultaneous onset of primary cutaneous B-cell lymphoma and human herpesvirus 8-associated Kaposi's sarcoma

We report the simultaneous occurrence of Kaposi's sarcoma (KS) and primary cutaneous B-cell lymphoma (CBCL) of the leg in a 79-year-old woman, seronegative for HIV-1, HTLV-1 and HTLV-2. The CBCL underwent complete clinical remission after local radiotherapy, whilst the KS became disseminated within a year following diagnosis. However, 2 years after the diagnosis of KS, the patient died with neurological symptoms. These were presumed to be due to involvement of the central nervous system by lymphoma, although in the absence of an autopsy, this could not be proven. Skin biopsies from the original KS and CBCL lesions, as well as short-term culture of spindle cells from the KS lesion and peripheral blood mononuclear cells (PBMC), were studied by semiquantitative polymerase chain reaction (PCR) using primers specific for DNA sequences of a novel gamma-herpesvirus-8 (HHV-8). PCR studies were strongly positive for the virus on KS cells and PBMC; conversely, a low viral load was found on CBCL cells. A high titre of serum IgG antibodies reacting with the nuclei of the HHV-8 positive cell line BCP-1 was found. These data suggest that reactivation of latent infection with HHV-8 had occurred in this patient, and that HHV-8 is directly involved in KS, but not in CBCL of the leg, an aggressive variant of CBCL.     

Seroprevalence of human herpesvirus 8 among Zambian women of childbearing age without Kaposi's sarcoma (KS) and mother-child pairs with KS

The seroprevalence of human herpesvirus 8 (HHV-8) among a group of Zambian women of reproductive age and among mother-child pairs in which either one of them has Kaposi's sarcoma (KS) was determined. A cross-sectional group of 378 pregnant women was randomly recruited into the study, and 183 (48.4%) had HHV-8 antibodies. Among the human immunodeficiency virus (HIV)-1-infected women, 51.1% were HHV-8-seropositive, whereas of HIV-1-negative women, 47.3% were HHV-8-seropositive. In addition, 21 women index patients with KS and 5 young children index patients with KS were studied. All children with KS had mothers who were HHV-8-seropositive, while not all children whose mothers had KS were infected with HHV-8. Our study suggests that there is a high HHV-8 seroprevalence among Zambian women, and the rate is almost the same in HIV-1-positive and -negative women. This high seroprevalence may be a contributing factor toward the increased frequency of KS in this population.     

Epilepsy and mental retardation in a subset of early onset 4q35-facioscapulohumeral muscular dystrophy

This study was designed to determine whether there is serologic or molecular evidence of human herpesvirus 8 (HHV-8) activation in renal transplant patients, an immunocompromised population at risk for development of Kaposi's sarcoma. Indirect immunofluorescence for detection of HHV-8 serum antibody and Southern blot polymerase chain reaction (PCR) for detection of viral DNA in whole blood were used. Seroprevalence and geometric mean titer (GMT) were significantly increased in the transplant group compared with healthy adults and were comparable to those in human immunodeficiency virus (HIV)-positive adults (transplant patients, 50% [GMT 1:210]; healthy adults, 7% [GMT 1:44]; HIV-positive patients, 73% [GMT 1:172]). Viral DNA was present in the blood of some renal transplant patients (3/33 PCR-positive) but in none of 20 healthy adults. Thus, there is both serologic and molecular evidence of HHV-8 activation in the renal transplant population compared with healthy adults (P<.01). The serologic results approximate those obtained for HIV-positive adults.     

Comparison of the prevalence of antibodies to human herpesvirus 8 (Kaposi's sarcoma-associated herpesvirus) in Brazil and Colorado

The prevalence of human herpesvirus 8 (HHV-8; Kaposi's sarcoma [KS] herpesvirus) infection was determined by IFA in 297 persons living in Brazil and Colorado. The prevalence of antibody to HHV-8 in human immunodeficiency virus (HIV) type 1-seropositive gay men with and without KS was similar in Brazil and Colorado. In Brazil, the prevalence of HHV-8 antibody was significantly greater in HIV-1-seronegative gay men than in HIV-1-seronegative male intravenous drug users. HHV-8-seropositive Brazilian gay men who had a clinical diagnosis of KS or who were infected with HIV-1 had significantly higher titers of HHV-8 antibody than did HHV-8-seropositive, HIV-1-seronegative Brazilian gay men. These findings provide further support for the association between HHV-8 infection and KS and suggest that, as in the United States, HHV-8 infection is transmitted sexually in Brazil.     

Kaposi's sarcoma and human herpesvirus-8

KS is a major cause of morbidity and mortality among AIDS patients and a treatment problem in the sporadic cases that are not associated with HIV. All four forms of the disease are linked to a newly described herpesvirus, HHV-8 or KSHV, via strong epidemiologic associations and biologic plausibility as a causal agent. HHV-8 is also epidemiologically associated with body cavity-based lymphomas, which are almost unique to AIDS, and Castleman's disease. Existing radiation and chemotherapeutic treatments of KS are only partially effective and cause significant adverse effects. New preventive approaches and therapies aimed at inhibiting HHV-8 may be effective. New treatments that interfere with the molecular mechanisms that drive KS may, in the future, provide the best opportunities to control the disease.     

Immunological profile of endemic and epidemic Kaposi's sarcoma patients in Dar-es-Salaam, Tanzania

Kaposi's sarcoma (KS) presents in four clinicopathological types namely classical/sporadic (CKS), endemic African (EKS), iatrogenic (IKS) and that associated with AIDS (AKS). Recently a putative herpes virus (HHV-8) was described and shown to be present in all four types of KS. The immunological status of patients with EKS has been conflicting. In this study total leucocyte counts, total lymphocyte counts and lymphocyte subsets of patients with EKS and AKS were determined by flow cytometry and compared to those of healthy HIV-1 seronegative controls. Results show that 50% of EKS lesions were of nodular type. Patients with EKS had significantly lower levels of CD4+ T- lymphocytes and CD4:CD8 ratio but significantly higher CD8+ T-lymphocytes compared to controls. Patients with AKS had significantly lower levels of CD4+ T-lymphocytes and also CD4:CD8 ratios but significantly higher percentage of CD8+ T-lymphocytes when compared with EKS patients. These findings indicate that in both forms of KS there is a certain degree of immunological disturbance which is more conspicuous in AKS because of HIV infection and suggests that HIV-1 acts synergistically with the aetiological agent (HHV-8) to cause a more aggressive type of KS.     

Survey of drug and alcohol use by lesbian women in New Zealand

A newly identified herpesvirus has been associated with Kaposi's sarcoma. We determined risk factors for Kaposi's-sarcoma-associated herpesvirus/human herpesvirus 8 (KSHV/HHV-8) seropositivity and incidence of infection over time in a cohort of Danish homosexual men followed from 1981 to 1996. Antibodies to a latent nuclear (LANA) and a structural (orf65) antigen of KSHV/HHV-8 were measured by immunofluorescence and ELISA/WB respectively. Through linkage with the national AIDS registry, all cohort members diagnosed with AIDS as of September 1996 were identified and their hospital records were scrutinized to record all diagnoses of KS. Overall, 21.1% (52/246) of the men were KSHV/HHV-8-seropositive in 1981. Among the initially seronegative, the rate of KSHV/HHV-8 seroconversion was highest between 1981 and 1982 and declined steadily thereafter. In a multivariate analysis of the status at enrollment in 1981, KSHV/HHV-8 seropositivity was not associated with age but was independently associated both with number of receptive anal intercourses (OR = 2.83; p = 0.03) and with sex with US men (OR = 2.27; p < 0.05). In a multivariate analysis of follow-up data, risk of KSHV/HHV-8 seroconversion was independently associated with having visited homosexual communities in the United States, and current HIV-positive status. More than 5 years' homosexual experience was associated with an insignificantly increased risk (RR = 2.68). KS occurred only in HIV-positive men who were KSHV/HHV-8-positive at or prior to their KS diagnosis. In conclusion, KSHV/HHV-8 appears to be sexually transmitted, probably by receptive anal intercourse, and may have been introduced to Danish homosexual men via sex with US men. The epidemic of KSHV/HHV-8 is now declining. These findings are concordant with the view that KSHV/HHV-8 may have been actively spread simultaneously with and by the same activities that lead to the spread of HIV.     

Chromosome breakpoint distribution in nonmelanoma skin cancers

Human herpesvirus 8 (HHV-8) DNA sequences were examined in peripheral blood mononuclear cell (PBMC) DNA samples of 56 children, 15 healthy adults, and 10 renal transplant patients by the polymerase chain reaction (PCR). The PCR amplification was carried out using the published KS330(233) primer pairs to amplify HHV-8 DNA sequences. The PCR-amplified products were confirmed by Southern blot hybridization with radiolabeled 233 bp HHV-8 DNA fragment, which was cloned and sequenced from the PCR-amplified product of Kaposi's sarcoma tissue. Six PCR-amplified product of four children and two renal transplant patients were cloned and sequenced. HHV-8 DNA sequences were detected in 36 of 56 (64%) normal children, in 12 of 15 (80%) healthy adults, and in all 10 renal transplant patients by Southern blot hybridization of PCR-amplified products. Six PCR-amplified products were confirmed by sequencing. These results suggest that HHV-8 infection is prevalent in the Japanese population with infection occurring in early childhood.     

Human herpesvirus 8--the first human Rhadinovirus

Kaposi's sarcoma (KS)-associated herpesvirus, also known as human herpesvirus 8 (HHV-8), is the first known human member of the genus Rhadinovirus. It is regularly found by polymerase chain reaction in all forms of KS, in certain types of Castleman's disease, and in body cavity-based B-cell lymphoma. Other members of this virus group occur in nonhuman primates, ungulates, rabbits, and mice and cause in part fulminant lymphomas and other neoplastic disorders of the hematopoietic system. Rhadinoviruses share a typical genome structure; most characteristically, they contain numerous sequences that appear to be sequestered from cellular DNA. We cloned and sequenced almost the complete genome of HHV-8 from a single KS biopsy specimen. Although this procedure revealed collinear organization and extensive homologies with the open reading frames of herpesvirus saimiri, genes with homology to the known oncoproteins (Stp, Tip) were not identified in the HHV-8 genome. However, HHV-8 reading frame K1, the positional analogue of Stp/Tip, was found to be significantly variable between different strains. We found, in addition, the reading frames for homologues of cellular interleukin 6, macrophage inflammatory proteins alpha and beta (MIP1 alpha and MIP1 beta, respectively), an interferon-responsive factor, and two inhibitors of apoptosis. Several of these cell-homologous genes of HHV-8 have already been shown to code for functional proteins.     

Big but weak: how many pathogenic genes does human herpesvirus-8 need to cause Kaposi's sarcoma? (Review)

Human herpesvirus-8 (HHV-8) is implicated in the pathogenesis of Kaposi's sarcoma (KS). In the last two years several HHV-8 gene products were heralded to 'cause KS' without any evidence that the respective gene is expressed in the tumor cells of KS lesions. In this framework it is of interest that almost 10% of the genes encoded by HHV-8 have been suggested to promote KS development due to either mitogenic, anti-apoptotic, chemoattractive, angiogenic or transforming activities. The rapidly growing number of HHV-8-encoded genes with 'KS causing' activities raises the question of why HHV-8 may need so many genes to trigger growth of KS that appears to be more closely related to a hyperplasia than to a real sarcoma. In this review an overview of the current knowledge of HHV-8 gene expressions in KS lesions in vivo is presented.     

Some aspects of the pathogenesis of HIV-1-associated Kaposi's sarcoma

Kaposi's sarcoma (KS) is a very rare tumor except after human immunodeficiency virus type 1 (HIV-1) infection when it becomes common. Most investigators assume that the role of HIV-1 is passive, i.e., via inducing immune deficiency, thereby enhancing cancer development, and specifically, in the case of human herpesvirus 8 (KSHV) by enhancing HHV-8 replication. We suggest that the role of HIV-1 is more active in the disease process by at least two events: 1) promoting an increase in inflammatory cytokines, which through sustained release influences early stage KS by inciting local microinflammatory responses, and 2) by the Tat protein that effects growth of the inflammatory cells. Cultures of all activated endothelial spindle cells, whether hyperplastic or neoplastic, are negative for HHV-8; transmission of HHV-8 does not induce cell growth or transformation; monkeys immune suppressed by simian immunodeficiency virus infection and infected also with HHV-8 do not develop KS; polymerase chain reaction analysis of blood cells shows HHV-8 sequences in monocytes and B cells (about 20% of normal donors in Maryland); M. Starzl showed that early KS has few cells (mostly macrophage) positive for HHV-8, increasing and present in endothelial cells only late in the disease; no increase in HHV-8 has been found in association with progressive immune deficiency; and recent studies in Gambia by others showed that HHV-8 is a very common infection, and though HHV-2 is known to be relatively common, HIV-1 is unusual and so is KS. Collectively, these findings lead me to conclude that there is little evidence that HHV-8 is a transforming virus as has been repeatedly suggested and that its role in KS is more likely to be indirect (like HIV-1), perhaps necessary but hardly likely to be sufficient for KS development.     

Reactivities of human sera with human herpesvirus-8-infected BCBL-1 cells and identification of HHV-8-specific proteins and glycoproteins and the encoding cDNAs

The reactivates of human sera with uninduced and phorbol ester (TPA)-induced human herpesvirus-8 (HHV-8)-infected BCBL-1 cells were examined by immunofluorescence assay (IFA) and by radioimmunoprecipitation reactions (RIP). The seroprevalence of HHV-8 infections is low in the United States general population and only low levels of HHV-8 antibodies were detected in the seropositive sera. In contrast, high levels of antibodies against HHV-8 lytic and latent antigens were detected by IFA in the sera from HIV+ Kaposi's sarcoma (KS)-positive individuals. These sera recognized several proteins and glycoproteins from BCBL-1 cells in RIP reactions. Two types of antibody responses were detected in the sera from HIV+ KS- homosexual men. In majority of the sera with and without detectable HHV-8 DNA in the peripheral blood mononuclear cells (PBMC), significantly low levels of HHV-8 antibodies were detected by IFA. These sera recognized only a subset of HHV-8 proteins and glycoproteins in RIP reactions. In contrast, in a subgroup of sera from HIV+ KS- homosexual men, higher levels of IFA antibodies against HHV-8 lytic and latent antigens were detected. These sera also recognized several viral proteins and glycoproteins in RIP reactions. These results suggest that antibody response profiles to HHV-8 infection vary significantly and serologic assays to detect antibody responses to a panel of both lytic and latent antibodies may be required for maximum sensitivity. Screening of a cDNA library from TPA-induced BCBL-1 cells with an HIV+ KS+ serum identified cDNAs encoding 12 HHV-8 proteins. Further characterization of these HHV-8 proteins would define the HHV-8 antigens useful for seroepidemiological studies and in discriminating lytic, latent, past, and/or reactivation infections.     

Distribution of IgE and IgG antibody levels against house dust mites in schoolchildren, and their relation with asthma

Progressive multifocal leukoencephalopathy (PML), a viral-induced demyelinating disease, is becoming relatively common, while many diagnostic and pathogenetic aspects remain to be clarified. A study was therefore undertaken in 64 AIDS patients suffering from various neurological disorders, including PML (12 subjects), with the specific objective of searching for JC virus (JCV) DNA by nested PCR (n-PCR) in cerebrospinal fluid (CSF), peripheral blood mononuclear cells (PBMCs), and urine collected from all patients. CSF examination, CD4 and CD8 counts, neurological examinations, and neuroradiological investigations were undertaken. JCV DNA was detected in 92% of CSF specimens in 75% of the PBMCs and urine samples from the PML patients, whereas among the non-PML patients JCV DNA was not detected in any CSF samples, but was found in 10% of PBMCs and in 39% of the urine specimens. BKV and JCV DNA viruria was observed simultaneously in 6% of the AIDS patients without PML. The routine CSF tests including IgG oligoclonal bands, the Link, and Tourtellotte IgG indexes, did not show a typical pattern in PML cases. The data obtained clearly indicate that the detection of JCV DNA in CSF constitutes an efficient marker for PML diagnosis. The simultaneous presence of JCV DNA in the CSF, PBMCs, and urine samples from the PML patients, who did not differ from controls with regard to their immunosuppressive status, suggests that JCV could be carried into the central nervous system (CNS) by infected PBMCs.     

Kaposi's sarcoma pathogenesis: a link between immunology and tumor biology

Kaposi's sarcoma (KS) was a rare disease in Europe and North America until a decade ago, when it became the most common neoplasm complicating the acquired immunodeficiency syndrome (AIDS), where it acquires an aggressive course. Clinical and experimental data suggest that, at least in early stage, KS may not be a true sarcoma, but an hyperplastic-proliferative lesion that may regress. At least three components characterize KS lesions: (1) neoangiogenesis and proliferation of spindle-shaped cells of endothelial and macrophage cell origin, some of which may originate from a circulating precursor; (2) a cellular infiltrate represented by macrophages, lymphoid cells, mast cells, and neutrophils; and (3) the infection of spindle cells and mononuclear cells with a new virus of the Herpesvirinae family defined KS-associated herpesvirus or human herpesvirus-8 (HHV-8). KS lesions are highly responsive, in terms of growth, to inflammatory cytokines (IC) and many lesional cell components are able to secrete cytokines and chemokines, which induce paracrine-autocrine mechanisms of growth, angiogenesis, and promote further cellular recruitment. The association between HHV-8 and KS is close; however, the role of the virus in KS development is yet unknown. Nevertheless, the virus has the potential to encode for homologs of cellular cytokines and some chemokines and its reactivation is sensitive to stimuli provided by IC. This review focuses on these aspects of KS pathogenesis, trying to reconcile many of the clinical and experimental observations. Finally, the role of the HIV-1 Tat protein as a factor of progression in AIDS-KS as well as the role of cellular and HHV-8 encoded proto-oncogenes as factors and markers of progression of KS to a true malignancy is reviewed.     

Human herpesvirus 8 variants in sarcoid tissues

BACKGROUND: The cause of sarcoidosis is unknown, although mycobacteria have been implicated. We examined sarcoid tissues for human herpesvirus 8 (HHV-8) in addition to mycobacterial genomic sequences. METHODS: Biopsy samples from 17 patients with sarcoidosis were studied (eight transbronchial, 27 lymph node, two skin, and two oral mucosa). We used tissues (n = 137) from 96 patients without sarcoidosis as negative controls. A nested PCR was applied to amplify a segment of open reading frame (ORF) 26 of the HHV-8 genome, and a heminested PCR was to amplify a segment of ORF 25 of HHV-8 and of the 16 S rRNA gene of mycobacteria. Differences in base sequences of the amplified fragments were resolved with single-strand conformation polymorphism and dideoxy sequencing. FINDINGS: HHV-8 ORF 26 DNA was detected in significantly higher proportions of sarcoid than of non-sarcoid tissue samples from lung (8/8 vs 0/54; p < 0.0001), lymph nodes (26/27 vs 6/29; p < 0.0001), skin (2/2 vs 0/17; p = 0.006), and oral tissues (2/2 vs 1/13; p = 0.029). 31 (82%) of the 38 ORF 26 DNA-positive sarcoid specimens were also positive for ORF 25 DNA. For mycobacteria-like 16 S rRNA DNA, the proportion positive was significantly higher in sarcoid than non-sarcoid tissues for lymph node samples (11/27 vs 2/29; p = 0.003) but not for other tissues (lung 3/8 vs 22/54; skin 2/2 vs 15/17; and oral tissues 1/2 vs 0/13). Overall, the prevalence of HHV-8 ORF 26 sequences was higher in sarcoid tissues than in non-sarcoid tissues (p < 0.0001). When patients whose tissues were included in a masked phase of the study were treated as units of analysis, eight of eight sarcoidosis patients were positive for HHV-8 ORF 26 DNA, compared with three of 56 control patients (p < 0.0001); for mycobacteria-like sequences, three of eight sarcoidosis patients were positive, compared with four of 56 controls (p = 0.0464). The HHV-8 ORF 26 sequences, ten of which were unique, could be segregated into four groups according to peptide motifs. In seven of nine patients from whom biopsy samples were taken from various sites, different sequences were recovered. The mycobacterial sequences amplified from sarcoid tissues were also varied, but none was homologous to those of known species. INTERPRETATION: Variant HHV-8 DNA sequences are found in a wide range of sarcoid but not non-sarcoid tissues. Mycobacteria-like 16 S rRNA sequences are more frequently present in sarcoid lymph nodes and not in other tissue types, but do not indicate infection by a particular mycobacterial species.