Human herpesvirus 6 (variant A) in Kaposi's sarcoma

Co-infections and Pathogenesis of KSHV-Associated Malignancies

Kaposi’s sarcoma-associated herpesvirus (KSHV), also known as human herpes virus 8 (HHV-8) is one of the several carcinogenic viruses that infect humans. KSHV infection has been implicated in the development of Kaposi’s sarcoma (KS), primary effusion lymphoma, and multicentric Castleman’s Disease. While KSHV infection is necessary for the development of KSHV associated malignancies, it is not sufficient to induce tumorigenesis. Evidently, other co-factors are essential for the progression of KSHV induced malignancies. One of the most important co-factors, necessary for the progression of KSHV induced tumors, is immune suppression that frequently arises during co-infection with HIV and also by other immune suppressants. In this mini-review, we discuss the roles of co-infection with HIV and other pathogens on KSHV infection and pathogenesis.

Sensitive, qualitative detection of human herpesvirus-6 and simultaneous differentiation of variants A and B

BACKGROUND

The current limitations of laboratory testing for the detection of human herpesvirus virus 6 (HHV-6) in clinical specimens with low HHV-6 viral loads make this area a priority for further research and development.

OBJECTIVES

To develop and validate a sensitive qualitative assay for simultaneous HHV-6 detection and variant differentiation.

METHODS

We developed a diagnostic procedure, which combines a magnetic bead-based nucleic acid extraction, PCR amplification, and colorimetric microtiter plate identification (MAG-PCR-EIA), for the sensitive detection of HHV-6 and the simultaneous differentiation of HHV-6A and HHV-6B.

RESULTS

Analytic sensitivities of the MAG-PCR-EIA assay were 10 copies per reaction for both HHV-6A and HHV-6B variants, which is equivalent to 20 copies/ml when 1ml of clinical specimen was processed. A proficiency panel containing 11 blinded specimens covering HHV-6A viral loads from 0 to 100,000 copies was tested, and the MAG-PCR-EIA was able to detect the lowest concentration at one copy in 200microl. A panel of 27 urine specimens, which were collected from patients with and without chronic fatigue syndrome, was tested by the MAG-PCR-EIA. HHV-6 was detected in two (HHV-6A) patients who have chromosomally integrated HHV-6A and in one (HHV-6B) patient who was a healthy control and diagnosed as cervical cancer later on. The HHV-6 results did not correlate with results previously determined by HHV-6 antigenemia in urine.

CONCLUSION

With large specimen volumes processed and an additional signal amplification incorporated, the MAG-PCR-EIA provides a sensitive and qualitative system for HHV-6 detection and simultaneous variant differentiation. Clinical relevance of the assay awaits further investigation.

Human herpesvirus 6 activates lytic cycle replication of Kaposi's sarcoma-associated herpesvirus

Kaposi's sarcoma-associated herpesvirus (KSHV) or human herpesvirus 8 (HHV-8) is a gamma-herpesvirus consistently identified in Kaposi's sarcoma (KS), primary effusion lymphoma, and multicentric Castleman's disease. KSHV infection appears to be necessary, but not be sufficient for development of KS without other co-factors. However, factors that facilitate KSHV to cause KS have not been well defined. Because patients with KS are often immunosuppressed and susceptible to many infectious agents including human herpesvirus 6 (HHV-6), we investigated the potential of HHV-6 to influence the replication of KSHV. By co-culturing HHV-6-infected T cells with KSHV-latent BCBL-1 cell line, infecting BCBL-1 cells with HHV-6 virions, and generating heterokaryons between HHV-6-infected T cells and BCBL-1 cells, we showed that HHV-6 played a critical role in induction of KSHV replication, as determined by production of lytic phase mRNA transcripts and viral proteins. We confirmed and extended the results by using a luciferase reporter assay in which KSHV ORF50 promoter, the first promoter activated during KSHV replication, drove the luciferase expression. Besides HHV-6, we also found that cytokines such as interferon-gamma partially contributed to induction of KSHV replication in the co-culture system. These findings suggest that HHV-6 may participate in KS pathogenesis by promoting KSHV replication and increasing KSHV viral load.

Evidence of active herpesvirus 6 (variant-A) infection in patients with lymphadenopathy in Belém, Pará, Brazil

A total of 323 patients with lymphadenopathy were selected in Belém, Brazil, between January 1996 and December 2001, and screened for the presence of human herpesvirus-6 (HHV-6) IgM- and--IgG antibodies by enzyme-linked immunosorbent assay (ELISA). When seroprevalence is analyzed by gender, similar rates are found for female (60.6%) and male (55.7%) individuals. Seventy-seven (23.8%) patients were HHV-6-IgM-and--IgG-positive (IgM+ subgroup), with positivity rates of 29.7% and 17.7% (p = 0.0007) for female- and male individuals, respectively. Sera from a subgroup (n = 120) of these subjects, with high HHV-6 antibody levels (either IgM+ or IgG+ reactivities), were subsequently processed for the presence of HHV-6 DNA by polymerase chain reaction (PCR)/nested PCR. Active infections (IgM+ and/or IgG+ high levels specific antibodies plus detection of viral DNA) were diagnosed in 20/77 (20.0%) and 8/43 (18.6%); subgroup of the 120 individuals suspected of having HHV-6 suggestive recent infection. All (n = 28) cases of active infection were found to be associated with HHV-6 variant-A (HHV-6A), as detectable by PCR/nested PCR, using variant-specific primer that amplify regions of 195 base pairs (bp) (HHV-6A) and 423 bp (HHV-6B). Rates of HHV-6 DNA detection between female and male patients were similar (p > 0.05) in the IgM+ and IgG+ groups: 20.4% versus 35.7% and 25.0% versus 13.0%, respectively. HHV-6 DNA was detected across < or = 5 through 41-50-year age-groups for patients whose serum samples were IgM+, with rates ranging from 7.7% (female subjects aged < or = 5 years) to 80.0% (male, 11-20 years). Among patients whose serological status was IgG+, HHV-6 DNA was detected in < or = 5, 6-10, 21-30 and > 50 age-groups at rates that ranged from 15.4% (male, < or = years of age) to 100.0% (female aged 11-20 years). Swelling cervical lymph nodes were the most common sign, accounting for 9 (32.0%) cases in each gender group. Among patients (n = 28) with active infection by HHV-6A variant, duration of symptoms lasted 1-5 days in 35.7% of subjects, whereas in 64.3% of them the disease lasted 6-20 days. Our data suggest that it is worth seeking for HHV-6 infection whenever a patient (infant or adult) presents with lymphadenopathy as a prominent symptom in the course of an acute febrile illness.

Detection of DNA of lymphotropic herpesviruses in plasma of human immunodeficiency virus-infected patients: frequency and clinical significance

The frequency and clinical significance of detection of DNA of cytomegalovirus (CMV), Epstein-Barr virus (EBV), human herpesvirus 6 (HHV-6), HHV-7, and HHV-8 in plasma were investigated by PCR. The plasma was obtained from 120 selected human immunodeficiency virus (HIV)-infected patients, of whom 75 had AIDS-related manifestations, 32 had primary HIV infection (PHI), and 13 had asymptomatic infections. Nested PCR analysis revealed that none of the lymphotropic herpesviruses tested were found in patients with PHI, in asymptomatic HIV-positive individuals, or in HIV-negative controls. By contrast, DNA of one or more of the viruses was found in 42 (56%) of 75 patients with AIDS-related manifestations, including CMV disease (CMV-D) or AIDS-related tumors. The presence of CMV DNA in plasma was significantly associated with CMV-D (P < 0.001). By contrast, EBV detection was not significantly associated with AIDS-related lymphomas (P = 0.31). Interestingly, the presence of HHV-8 DNA in plasma was significantly associated with Kaposi's sarcoma (KS) disease (P < 0.001) and with the clinical status of KS patients (P < 0.001). CMV (primarily), EBV, and HHV-8 were the viruses most commonly reactivated in the context of severe immunosuppression (P < 0.05). In contrast, HHV-6 and HHV-7 infections were infrequent at any stage of disease. In conclusion, plasma PCR was confirmed to be useful in the diagnosis of CMV-D but not in that of tumors or other conditions possibly associated with EBV, HHV-6, and HHV-7. Our findings support the hypothesis of a direct involvement of HHV-8 replication in KS pathogenesis, thus emphasizing the usefulness of sensitive and specific diagnostic tests to monitor HHV-8 infection.

Detection of human herpesvirus 8 in Korean Kaposi's sarcoma cases by polymerase chain reaction and in situ polymerase chain reaction

Several infectious agents, including herpesvirus-like particles, had been suggested as possible candidates for the development of Kaposi's sarcoma (KS), and a new herpesvirus, human herpesvirus 8 (HHV-8), was recently identified in the vast majority of KS lesions, irrespective of their association with human immunodeficiency virus (HIV) infection. However, the etiologic role of HHV-8 in KS remains controversial. We undertook this study to screen for and localize the presence of HHV-8 in KS in Korea. A total of 46 paraffin-embedded specimens were studied, including KS, hemangioproliferative disorders, and 10 non-KS lesions from HIV-positive patients. We performed nested polymerase chain reaction (PCR) and in situ PCR with HHV-8 specific primers. HHV-8 DNA sequences were detected in 8 of 11 KS specimens. All specimens of hemangioproliferative disorders, non-KS lesions from HIV-positive patients, and other skin samples were negative for HHV-8. When sequencing PCR products, the sequences were almost identical with the prototypic sequence for HHV-8. In PCR-positive tissues, in situ PCR staining of HHV-8 localized to nuclei of endothelial cells and perivascular spindle-shaped tumor cells. The results of this study suggest that HHV-8 is not widespread and has a certain causative role in the development of KS. Further studies, including serological and animal studies, will be helpful to appreciate an epidermiological link and pathogenetic mechanism between HHV-8 and KS.

Morphological, histochemical, immunohistochemical, and ultrastructural characterization of tumors and dysplastic and non-neoplastic lesions arising in BK virus/tat transgenic mice

To study the role in AIDS pathogenesis of the human immunodeficiency virus type 1 (HIV-1) Tat protein, a transactivator of viral and cellular genes, we generated transgenic mice with a recombinant DNA containing BK virus (BKV) early region and the HIV-1 tat gene, directed by its own promoter-enhancer. DNA hybridization revealed that the transgene is stably maintained in all organs of transgenic mice as a tandem insertion in a number of copies ranging from 5 to 20 per cell. In addition, tat and BKV RNA were expressed in all tissues. Transgenic mice developed three types of lesions: 1) tumors, 2) hyperplastic and dysplastic lesions, and 3) non-neoplastic lesions. Tumors of different histotypes, such as lymphomas, adenocarcinomas of skin glands, leiomyosarcomas, skin squamous cell carcinomas, hepatomas, hepatocarcinomas, and cavernous liver hemangiomas, developed in 29% of transgenic animals. The majority of tumors were malignant, invasive, and producing metastases. Conversely, tumors of only two histotypes (lymphomas and adenocarcinomas of skin glands) appeared in control mice. Hyperplastic and dysplastic lesions were more frequent in transgenic than in control mice and involved the skin or its adnexes, the liver and the rectum, indicating multiple targets for the activity of the transgene. Pyelonephritis, frequently complicated with hydronephrosis, inflammatory eye lesions, and amyloid depositions represented the most frequent non-neoplastic lesions detected in transgenic mice. Many of the pathological findings observed in this animal model are comparable to similar lesions appearing in AIDS patients, suggesting a relevant role for Tat in the pathogenesis of such lesions during the course of AIDS.

Human herpesvirus 6: An emerging pathogen

Infections with human herpesvirus 6 (HHV-6), a beta-herpesvirus of which two variant groups (A and B) are recognized, is very common, approaching 100% in seroprevalence. Primary infection with HHV-6B causes roseola infantum or exanthem subitum, a common childhood disease that resolves spontaneously. After primary infection, the virus replicates in the salivary glands and is shed in saliva, the recognized route of transmission for variant B strains; it remains latent in lymphocytes and monocytes and persists at low levels in cells and tissues. Not usually associated with disease in the immunocompetent, HHV-6 infection is a major cause of opportunistic viral infections in the immunosuppressed, typically AIDS patients and transplant recipients, in whom HHV-6 infection/reactivation may culminate in rejection of transplanted organs and death. Other opportunistic viruses, human cytomegalovirus and HHV-7, also infect or reactivate in persons at risk. Another disease whose pathogenesis may be correlated with HHV-6 is multiple sclerosis. Data in favor of and against the correlation are discussed.

PCR assay fails to detect molluscum contagiosum virus-related sequences in AIDS-related Kaposi's sarcoma

Previous PCR-based studies have demonstrated the presence of various viral DNA or RNA sequences in Kaposi's sarcoma (KS) tissues. To date, only human herpesvirus 8 (HHV-8) DNA sequences are found consistently in KS. The putative role of this agent in KS pathogenesis remains, however, to be determined; HHV-8 could infect populations endemically and could be reactivated in patients with KS. A close association between AIDS-related KS and molluscum contagiosum occurrence was found and this study was conducted primarily to search for the presence of molluscum contagiosum virus DNA sequences in KS. Frozen KS samples were examined for the presence of both HHV-8 and molluscum contagiosum virus DNA sequences by PCR. Despite a high rate of co-infection, no molluscum contagiosum virus (MCV) DNA sequence could be found in the KS samples whereas HHV-8 was uniformly detected. These results suggest that the high prevalence of MCV in AIDS patients with KS relies on a mode of transmission common for HHV-8 and molluscum contagiosum virus rather than on a multiviral etiology of KS. They may also indicate a particular susceptibility of the host to viral reactivation. If this is so, the failure to detect MCV DNA sequences in KS tissues by PCR indicates that locally produced or released cyotokines are not involved in the latter process.

Studies on the antibodies to human herpesvirus type 6 among Hungarian patients with asymptomatic HIV infection

The occurrence and the possible role in promoting HIV infection by human herpesvirus type 6 (HHV-6) have not yet been revealed in Hungary. In different groups of patients, serum titre of IgM and IgG antibodies, as well as avidity of IgG were quantitated by indirect immunofluorescence and an enzyme-linked immunosorbent assay, using isolate U1102 of HHV-6 variant A as antigen. In 60% of HIV-seronegative adult controls, high avidity IgG antibodies were found in low titre suggesting childhood infection. In HIV-seronegative persons with high risk behaviour for HIV-infection, both IgM and low avidity IgG were frequently found in higher titre, representing either primary or frequent reinfections, or reactivation of latent HHV-6. In asymptomatic HIV-seropositive patients, high titre of high avidity IgG antibodies was predominant, proving virus infection in the near past. These results indicate the contribution of HHV-6 to immunosuppression prior to AIDS, predisposing the organism to HIV infection.

PCR analysis of human telomeric repeats present on HHV-6A viral strains

Human herpesvirus 6 (HHV-6) presents a perfect tandem array of human telomeric repeats (TRS) at both identical direct repeats (DR). Several researchers have reported a different TRS copy number by sequence analysis of HHV-6 DR's cloned fragments so it has been hypothesized that number of TRS is unstable. By PCR we show that the TRS copy number of U1102 HHV-6 variant A strains is stable during viral cultivation in cell lines and each HHV-6 variant A strain, detected in pathologic specimens, is characterized by a specific TRS copy number.

CD68+ cells of monocyte/macrophage lineage in the environment of AIDS-associated and classic-sporadic Kaposi sarcoma are singly or doubly infected with human herpesviruses 7 and 6B

Earlier studies have shown that Kaposi sarcomas contain cells infected with human herpesvirus (HHV) 6B, and in current studies we report that both AIDS-associated and classic-sporadic Kaposi sarcoma contain HHV-7 genome sequences detectable by PCR. To determine the distribution of HHV-7-infected cells relative to those infected with HHV-6, sections from paraffin-embedded tissues were allowed to react with antibodies to HHV-7 virion tegument phosphoprotein pp85 and to HHV-6B protein p101. The antibodies are specific for HHV-7 and HHV-6B, respectively, and they retained reactivity for antigens contained in formalin-fixed, paraffin-embedded tissue samples. We report that (i) HHV-7 pp85 was present in 9 of 32 AIDS-associated Kaposi sarcomas, and in 1 of 7 classical-sporadic HIV-negative Kaposi sarcomas; (ii) HHV-7 pp85 was detected primarily in cells bearing the CD68 marker characteristic of the monocyte/macrophage lineage present in or surrounding the Kaposi sarcoma lesions; and (iii) in a number of Kaposi sarcoma specimens, tumor-associated CD68+ monocytes/macrophages expressed simultaneously antigens from both HHV-7 and HHV-6B, and therefore appeared to be doubly infected with the two viruses. CD68+ monocytes/macrophages infected with HHV-7 were readily detectable in Kaposi sarcoma, but virtually absent from other normal or pathological tissues that harbor macrophages. Because all of the available data indicate that HHV-7 infects CD4+ T lymphocytes, these results suggest that the environment of the Kaposi sarcoma (i) attracts circulating peripheral lymphocytes and monocytes, triggers the replication of latent viruses, and thereby increases the local concentration of viruses, (ii) renders CD68+ monocytes/macrophages susceptible to infection with HHV-7, and (iii) the combination of both events enables double infections of cells with both HHV-6B and HHV-7.

Human herpesvirus 6

Human herpesvirus 6 variant A (HHV-6A) and human herpesvirus 6 variant B (HHV-6B) are two closely related yet distinct viruses. These visuses belong to the Roseolovirus genus of the betaherpesvirus subfamily; they are most closely related to human herpesvirus 7 and then to human cytomegalovirus. Over 95% of people older than 2 years of age are seropositive for either or both HHV-6 variants, and current serologic methods are incapable of discriminating infection with one variant from infection with the other. HHV-6A has not been etiologically linked to any human disease, but such an association will probably be found soon. HHV-6B is the etiologic agent of the common childhood illness exanthem subitum (roseola infantum or sixth disease) and related febrile illnesses. These viruses are frequently active and associated with illness in immunocompromised patients and may play a role in the etiology of Hodgkin's disease and other malignancies. HHV-6 is a commensal inhabitant of brains; various neurologic manifestations, including convulsions and encephalitis, can occur during primary HHV-6 infection or in immunocompromised patients. HHV-6 and distribution in the central nervous system are altered in patients with multiple sclerosis; the significance of this is under investigation.

HHV8 and Kaposi's sarcoma: a time cohort study

AIMS

The recent finding that human herpes virus 8 (HHV8) is found in the majority of Kaposi's sarcoma (KS) cases supports the epidemiological observation that the tumour may be caused by an infectious agent. This study aimed to address when and how HHV8 evolved.

METHODS

A cohort of African endemic KS (49 samples from 45 patients) and European KS (18 samples from 13 patients), spanning 27 years, was assessed for the presence of HHV8 by both standard solution phase polymerase chain reaction (PCR) and the newly described technique of TaqMan PCR.

RESULTS

HHV8 was present in approximately 49% (24 of 49 tissue samples) of the African cases and in more than 90% (16 of 18 tissue samples) of the European cohort, in keeping with recent seroepidemiological data.

CONCLUSIONS

HHV8 is strongly linked to the development of KS; however, in some patients, other factors may operate. The utility and flexibility of TaqMan PCR in detecting low copy viral target in human tissues was demonstrated.

Advances in Kaposi's sarcoma

KS remains a challenge to clinicians and investigators more than a century after its initial description. Debate continues as to the cell of origin, as well as whether or not it is a true cancer. KS appears to be an opportunistic neoplasm, which in its earliest phase retains some features of a benign hyperproliferative process, but in its late stages behaves like an aggressive malignancy. Pathogenesis seems to involve a predisposed individual (genetically susceptible or immunologically compromised) who comes into contact with an infectious agent, most likely a virus. Cytokines appear to play a major role in the growth of the tumor. The exact role of the KSHV in this process will likely be the subject of much investigation in the future.

The role of nucleic acid amplification and detection in the clinical microbiology laboratory

Clinical microbiology is in the midst of a new era. Methodology that is based on nucleic acid detection has slowly appeared in the diagnostic laboratory, and is revolutionizing our ability to assist physicians in the diagnosis and management of patients suffering from infectious diseases. Much like the introduction of immunoassays built around hybridoma technology in the 1980s, considerable doubt and promise exist hand in hand in the 1990s. Conventional testing that is technically straight forward, informative, and timely will always be a part of clinical microbiology; however, considerable room for improvement exists with organisms/diseases for which laboratory methods are limited. Nucleic acid methodology will have its greatest and long-awaited impact in this arena.

Frequency and distribution of herpesvirus-like DNA sequences (KSHV) in different stages of classic Kaposi's sarcoma and in normal tissues from an Italian population

The frequency and distribution of herpesvirus-like DNA sequences (KSHV) were investigated by PCR in the pathologic skin lesions of a series of 22 HIV-negative elderly patients with classic Kaposi's sarcoma (KS) from Italy, one of the few regions of the world where classic KS is prevalent. Viral sequences were clearly identifiable in 15 cases, in particular in 2 of 5 patch, in 3 of 6 plaque and in 10 of 11 nodular lesions. Our findings confirm the association of these herpesvirus-like DNA sequences with KS in unrelated populations, providing evidence of the putative KS-associated agent in all different histologic lesions of the disease, mainly in the nodular stage. The search for other herpesviruses by PCR showed that Epstein-Barr virus (EBV) sequences were present in 7 of 22 pathologic skin lesions. In 4 cases, both EBV and KSHV were present. On the contrary, all 22 classic KS specimens were negative for human herpesvirus-6 sequences. Two of 3 patch and the 1 nodular lesions from AIDS-related KS patients examined were positive for KSHV but negative for both EBV and HHV-6 sequences. Furthermore, we evaluated the prevalence of KSHV sequences in the normal population of the same geographical area. Thirteen peripheral blood mononuclear cell samples, 9 salivary gland tissues and 6 saliva samples from healthy subjects were invariably found negative for KSHV, using the same PCR technique. Of interest, 2 of 11 hyperplastic tonsils harboured these herpesvirus-like sequences, suggesting that, like other herpesviruses, the KS- associated agent may be harboured in a proportion of normal individuals and tonsils may represent at least one of the possible reservoirs of this putative lymphotropic gamma-herpesvirus in vivo.

Coinfection with human herpesvirus 6 variants A and B in lung tissue

Human herpesvirus 6 (HHV-6) variant B is frequently identified in peripheral blood, but identification of HHV-6 variant A is relatively rare. We devised a PCR-based method for sensitive, simultaneous detection of both HHV-6 variants. The method was applied to 34 lung tissue specimens that were previously shown to contain HHV-6 DNA. A total of 22 lung tissue samples showed coinfections with HHV-6 variants A and B, 2 had only HHV-6 variant A DNA, and 10 had only HHV-6 variant B DNA. The prevalences of coinfections in lung tissues from healthy controls (54% coinfected) and in those from bone marrow transplant patients with pneumonia (67% coinfected) were similar. These data indicate that coinfections of HHV-6 variants A and B commonly occur in lung tissues of healthy and diseased individuals.

Human herpesvirus 6 in human immunodeficiency virus-infected individuals: association with early histologic phases of lymphadenopathy syndrome but not with malignant lymphoproliferative disorders

Preliminary evidence suggested that human herpesvirus-6 (HHV-6) may act as a cofactor in acquired immunodeficiency syndrome (AIDS) and may contribute to the pathogenesis of lymphoproliferative disorders occurring in individuals infected with the human immunodeficiency virus (HIV). To understand better the biological and clinical significance of HHV-6 infection in the context of HIV-related immunosuppression, the polymerase chain reaction was used to study the frequency and variant distribution of HHV-6 in peripheral blood mononucleated cells (PBMCs) from HIV-seropositive individuals, either asymptomatic or with lymphadenopathy syndrome (LAS) or with overt AIDS. Non-neoplastic and malignant lymphoproliferative disorders from both HIV-infected and HIV-seronegative patients were also investigated using the same series of samples for the presence of Epstein-Barr virus (EBV). When compared with healthy blood donors (12/42, 29%), HHV-6 prevalence in PBMCs showed a progressive decline in HIV-seropositive individuals with asymptomatic HIV infection (3/26, 11%) and in patients with LAS (1/13, 8%) and a significant reduction in patients with overt AIDS (1/20, 20%; P = 0.02). The decrease correlated with the number of CD4+ cells at the time of examination. In addition, HHV-6 DNA sequences were significantly more prevalent in LAS biopsies (13/20, 65%) than in HIV-unrelated reactive lymphadenopathies (2/10, 20%; P = 0.02) and the presence of HHV-6 sequences correlated closely with a histologic pattern of follicular hyperplasia (13/16, 81%; P = 0.003). Strikingly, HHV-6 prevalence decreased in PBMCs of LAS patients, suggesting that the likelihood of interactions between HHV-6 and HIV varies in different body districts. In particular, the demonstration that all HHV-6-carrying LAS samples were also positive for HIV infection suggests that LAS lymph nodes constitute one of the sites where biologically relevant interactions between the two viruses might occur. Also, the prevalence of EBV was higher in LAS (14/20, 70%) than in non-neoplastic lymph nodes from HIV-seronegative individuals (4/10, 40%), although the difference was not statistically significant. EBV was associated strongly with HIV-related malignant lymphoproliferative disorders, being detected in 100% of patients with Hodgkin's disease (HD) and 53% of B-cell non-Hodgkin's lymphomas (NHL). In contrast, the prevalence of HHV-6 DNA in HD and B-cell NHL arisen in HIV-infected patients (30% and 6% respectively) was remarkably lower and similar to that observed in lymphoproliferative disorders from HIV-seronegative patients. Finally, as observed in healthy individuals, HHV-6 variant B was more prevalent than variant A in benign and malignant lymphoproliferative disorders from bot HIV-infected and HIV-seronegative patients. These results suggest that the interactions between HHV-6 and HIV could be different in the various phases of HIV disease and in different districts; HHV-6 has probably no direct role in the pathogenesis of HIV-associated B-cell NHL and HD cases, and behave differently from EBV; and HIV-related immunosuppression does not alter the distribution of HHV-6 variants in these tissues, as observed in the case of EBV.

Presence of human herpesvirus-like DNA sequence in oral Kaposi's sarcoma. A preliminary PCR study

DNA sequences closely related to herpesvirus-like sequences have been found in AIDS-associated Kaposi's sarcoma. Subsequent studies indicate that these DNA sequences may be consistently found in AIDS Kaposi's sarcoma and non-AIDS Kaposi's sarcoma from different geographic regions. Oral Kaposi's sarcoma is rare and the specificity of this viral DNA in oral Kaposi's sarcoma and in other oral neoplasms has not been examined. A total of 77 oral neoplasms, including 3 Kaposi's sarcoma specimens from 2 patients with AIDS, were analyzed by polymerase chain reaction for the presence of this herpesvirus-like DNA sequence with the 330-233 primers. All three specimens of oral AIDS-Kaposi's sarcoma from two patients were positive for this DNA sequence. All of the other intraoral lesions including hemangioma, pyogenic granuloma, and various types of epithelial neoplasms, however, had negative reactions. Our results further confirm that oral Kaposi's sarcoma appears to be associated with this herpesvirus-like DNA sequence.

Restriction endonuclease mapping and molecular cloning of the human herpesvirus 6 variant B strain Z29 genome

Human herpesvirus 6(HHV-6) variants A and B differ in cell tropism, reactivity with monoclonal antibodies, restriction endonuclease profiles, and epidemiology. Nonetheless, comparative nucleotide and amino acid sequences from several genes indicate that the viruses are very highly conserved genetically, The B variant is the major etiologic agent of exanthem subitum and is frequently isolated from children with febrile illness; no disease has been etiologically associated with HHV-6A. One HHV-6A strain has been cloned and sequenced, but similar information and reagents are not available for HHV-6B. We report here the determination of maps of the restriction endonuclease cleavage sites for BamHI, C1aI, HindIII, KpnI, and Sa1I, and the cloning in plasmids and bacteriophages of fragments representing over 95% of the HHV-6B strain Z29 [HHV-6B(Z29)] genome. Hybridization experiments and orientation of several blocks of nucleotide sequence information onto the genomic map indicate that HHV-6A and HHV-6B genomes are colinear.

Herpesvirus-like DNA sequences in classic Kaposi's sarcomas

Kaposi's sarcoma (KS) accounts for more than 15% of AIDS-related malignancies. The etiology of KS is unresolved but is postulated to be multifactorial, involving viruses and overexpression of cellular growth factors and/or oncogenes. Recently, herpesvirus-like sequences (KSHV) were identified with high prevalence in AIDS-KS (AKS), endemic KS, and in classic KS biopsies (CKS). To confirm the presence and the prevalence of the KSHV sequences, 18 CKS and 13 AKS samples were tested using polymerase chain reaction (PCR) analysis. To our knowledge this is the highest number of CKS samples that has ever been included in a single study, and it is also important that the biopsies were obtained from different institutions and geographical locations. KSHV sequences were detected in 100% of the AKS samples and 72% of the CKS biopsies using PCR analysis. The presence of the unique KSHV sequences was confirmed by direct sequencing of representative PCR products obtained from AKS and CKS samples. Reverse transcriptase (RT)-PCR experiments showed that the KSHV sequences were transcribed to mRNA in both AKS and CKS samples. Our results confirm that the putative new herpesvirus-like agent is associated with both AKS and CKS and may have an etiological role in the pathogenesis of this malignancy.

Human herpesvirus 6A ts suppresses both transformation by H-ras and transcription by the H-ras and human immunodeficiency virus type 1 promoters

Human herpesvirus 6 strain U1102 (HHV-6A) was shown to contain a 1,473-bp functional transformation suppressor gene (ts). ts exhibited 24% identity and 51% similarity to adeno-associated virus type 2 Rep68/78. Like adeno-associated virus type 2 Rep68/78, HHV-6A ts suppressed H-ras transformation of NIH 3T3 cells. Suppression of H-ras transformation was eliminated by translation termination linker mutation at amino acid 25, 125, or 245. These data indicated the importance of the C-terminal portion of the ts protein. H-ras transformation was suppressed by ts only when H-ras was expressed by its endogenous H-ras promoter and not when it was expressed by the heterologous murine osteosarcoma virus long terminal repeat (LTR). Furthermore, ts suppressed chloramphenicol acetyltransferase (CAT) activity when the CAT gene was expressed from the H-ras promoter but not the murine osteosarcoma virus LTR promoter. Taken together, the data showed that ts suppressed H-ras transformation at the level of the H-ras promoter. To further identify the interaction of ts with transcriptional regulatory elements, the human immunodeficiency virus type 1 (HIV-1) LTR was used. This promoter was selected because it has well-defined transcriptional regulatory elements for both basal and activated transcription, because its activity is inhibited by the Rep68/78 gene, and because both HHV-6 and HIV-1 naturally infect CD4+ T cells in vivo and have been shown to infect the same cell in vitro. ts suppressed expression from both wild-type and upstream mutant HIV-1 LTR-CAT constructs. However, downstream HIV-1 TAR mutations reversed ts suppression, indicating that TAR is one of the critical elements involved. The data presented demonstrated that HHV-6A ts functionally suppressed H-ras transformation and HIV-1 LTR expression and thus that it may be useful in future gene therapy.

Human herpesvirus type 6 and cytomegalovirus in AIDS-associated Kaposi's sarcoma: no evidence for an etiological association

Epidemiological studies indicate that acquired immune deficiency syndrome (AIDS)-associated Kaposi's sarcoma (KS) may be caused by an infectious, preferentially sexually transmitted agent. Herpesviruses infections are common sexually transmitted diseases in homosexual men, who are also the main risk group for developing Kaposi's sarcoma. To evaluate a possible role of human herpesvirus-6 (HHV-6) and cytomegalovirus (CMV) in the development of AIDS-associated KS, we investigated cutaneous AIDS-associated KS in 26 AIDS patients using the polymerase chain reaction (PCR) and immunohistochemistry (IHC) to detect the presence of HHV-6 and CMV. Human herpesvirus-6 was detected in nine of 26 Kaposi's sarcoma specimens (all cases were HHV-6 subtype B) and in eight of 27 normal skin specimens from human immunodeficiency virus (HIV) seropositive and HIV seronegative patients (one case was HHV-6 subtype A and seven cases were HHV-6 subtype B). In two of four patients showing HHV-6 in KS of the skin, the virus also was detected in other investigated tissues, such as heart, lung, liver, kidney, and adrenals. Cytomegalovirus was detected only in AIDS-associated KS (seven of 26 KS specimens) and not in normal skin tissues of HIV-seropositive and HIV-seronegative patients. Cytomegalovirus was detected in other organs of those patients showing CMV in Kaposi's sarcoma. Our data indicate that the presence of HHV-6 and CMV in AIDS-associated KS most likely reflects disseminated viral infection. Human herpesvirus-6 and CMV may be cofactors but not the only causative agents for the development of AIDS-associated KS.

Human herpesvirus 6 and human herpesvirus 7 in chronic fatigue syndrome

We analyzed lymphocytes of patients with chronic fatigue syndrome (CFS) for the presence of human herpesvirus 6 (HHV-6) and HHV-7 DNA. HHV-7 was present in over 80% of CFS patients and healthy controls, while the prevalence of HHV-6 variant A increased significantly in CFS cases (22 versus 4%; P = 0.05).

Human herpesvirus 6

HHV-6, the first T-lymphotropic human herpesvirus, is an important novel human pathogen. It is the cause of exanthem subitum in infants and may act as an opportunistic agent in immunocompromised patients. Moreover, several lines of clinical and experimental evidence suggest that HHV-6 may accelerate the progression of HIV infection. Progress in the study of HHV-6 has been rapid, in part as a consequence of the strong current interest in human lymphotropic viruses and their relationship with the immune system. Nonetheless, the full spectrum of diseases linked to this agent is still unknown (Table 2) and animal models of infection have not yet been exploited. The next few years will be crucial for a complete understanding of the potential role of HHV-6 in human disease.

Selection of a monoclonal antibody specific for variant B human herpesvirus 6-infected mononuclear cells

A monoclonal antibody, designated as MAb 6E2, specific for human herpesvirus 6 variant B (HHV-6B) was derived from the spleen of a mouse immunized with lysates of HHV-6B(Z29) cord blood mononuclear cells. MAb 6E2 reacts by immunofluorescence with all the HIV-6B strains tested (Z29, CV, Hashimoto and SF) and fails to react with variant A prototypes, GS and U1102. The immunofluorescence staining was punctate and localized to the cytoplasm. The protein reacting with MAb 6E2 was identified as protein 48,000 in apparent M(r) value by immunoaffinity chromatography of lysates of HHV-6B-infected mononuclear cells.

Controlled study of human herpesvirus 6 detection in acquired immunodeficiency syndrome-associated non-Hodgkin's lymphoma. The French Study Group for HIV-Associated Tumors

Human herpesvirus 6 (HHV-6) is a recently identified lymphotropic herpesvirus, which has been isolated from patients with acquired immunodeficiency syndrome (AIDS) or lymphoproliferative diseases. Two variants A and B of HHV-6 have been described, variant B being more common in children with exanthema subitum. HHV-6 infection was studied in cases of AIDS-associated non-Hodgkin's lymphoma (NHL), and in three control populations in order to evaluate the possible etiological role of HHV-6 in this lymphoproliferative disease. Tumor specimens from various organs were obtained from 27 patients with AIDS-associated NHL and 20 human immunodeficiency virus (HIV)-seronegative patients with NHL. Lymph node specimens were obtained from four HIV-seropositive and nine HIV-seronegative patients with lymph node follicular hyperplasia. A specific polymerase chain reaction (PCR) was used to detect HHV-6 DNA. Subsequently HHV-6 variant was identified by using variant-specific PCR. Human cytomegalovirus (CMV) infection was detected in parallel by means of specific PCR. HHV-6 DNA was detected in 12 of 27 tumor tissues (44%), including 8 of 15 lymph node specimens (53%) from patients with AIDS-associated NHL. The corresponding values in HIV-seronegative patients with NHL were 35% (7/20) and 36% (5/14), respectively. Lymph node specimens were positive for HHV-6 in two of four (50%) HIV-seropositive and five of nine (55%) HIV-seronegative patients with follicular hyperplasia. Variant A was detected in two cases of AIDS-associated NHL, variant B in one case, and both variants in six cases. The distribution of HHV-6 variants exhibited a similar pattern in the three control groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Identification of human herpesvirus 6 variants A and B by amplimer hybridization with variant-specific oligonucleotides and amplification with variant-specific primers

Two distinct PCR-based procedures were evaluated for the detection and identification of human herpesvirus 6 (HHV-6) variants A and B in uncultured human samples. Variant-specific oligonucleotide hybridization (VSOH) is based on the amplification of two distinct regions of the HHV-6 genome, followed by hybridization of amplimers with variant-specific oligonucleotide probes. Variant-specific primer PCR (VSPP) is based on the amplification of each variant by using variant-specific primers. The study of 10 well-characterized HHV-6 strains allowed us to demonstrate the high sensitivity and specificity of both methods. With variant mixtures, however, some limitations of VSOH were evidenced and VSPP was required to obtain unambiguous results. The combination of VSOH and VSPP was applied to the direct study of 300 peripheral blood mononuclear cell samples from French subjects. HHV-6 was detected in 15 samples: 11 corresponded to variant B, 3 corresponded to variant A, and 1 corresponded to a mixture of both variants.

Prevalence of human herpesvirus 6 variants A and B in patients with chronic fatigue syndrome

Peripheral blood mononuclear cells collected from 13 patients with chronic fatigue syndrome and 13 healthy controls were analyzed for the presence of human herpesvirus 6 (HHV-6) DNA by variant-specific polymerase chain reaction and dot blot hybridization. HHV-6 DNA was detected in 7 of 13 (53%) patients, and of those 7 patients, 4 were positive for HHV-6 variant A DNA and 3 were for variant B. No HHV-6 DNA was detected in the controls. Serum antibody titers to the late antigen and antibody prevalence to the early antigen of HHV-6 were significantly higher in the patient group. These results suggest active replication of HHV-6 in patients with chronic fatigue syndrome.

Human herpesvirus 6 and human herpesvirus 7 infections in renal transplant recipients and healthy adults in Turkey

We explored the prevalence of human herpesvirus 6 (HHV-6) and human herpesvirus 7 (HHV-7) infections in 16 renal transplant recipients and 16 healthy controls by virus isolation, serology, polymerase chain reaction (PCR) followed by dot blot hybridization. HHV-6 variant A was isolated from one renal transplant recipient. Seven patients (44%) and six controls (38%) had HHV-6 variant B DNA in their peripheral blood mononuclear cells. The prevalence of HHV-7 DNA was found to be the same in patients and controls (19%).