Human herpesvirus 6: a survey of presence and variant distribution in normal peripheral lymphocytes and lymphoproliferative disorders

Human herpes virus-6 seroprevalence and leukaemias: a case-control study. GIMEMA (Gruppo Italiano Malattie Ematologiche dell' Adulto)

The relationships between acute myeloid leukaemia (AML), acute lymphocytic leukaemia (ALL), chronic myeloid leukaemia (CML) and refractory anaemia with excess of blasts (RAEB) and human herpes virus (HHV)-6 antibody level were investigated in a multicentre case-control study. An association between increased HHV-6 seropositivity and geometric mean titre ratio with AML was shown: P for trend = 0.022, adjusted odds ratio 1.20, 95% confidence interval 1.07-1.33 respectively. No association was found between HHV-6 and ALL, CML or RAEB.

Human herpesviruses in chronic fatigue syndrome

We have conducted a double-blind study to assess the possible involvement of the human herpesviruses (HHVs) HHV6, HHV7, Epstein-Barr virus (EBV), and cytomegalovirus in chronic fatigue syndrome (CFS) patients compared to age-, race-, and gender-matched controls. The CFS patient population was composed of rigorously screened civilian and Persian Gulf War veterans meeting the Centers for Disease Control and Prevention's CFS case definition criteria. Healthy control civilian and veteran populations had no evidence of CFS or any other exclusionary medical or psychiatric condition. Patient peripheral blood mononuclear cells were analyzed by PCR for the presence of these HHVs. Using two-tailed Fisher's exact test analyses, we were unable to ascertain any statistically significant differences between the CFS patient and control populations in terms of the detection of one or more of these viruses. This observation was upheld when the CFS populations were further stratified with regard to the presence or absence of major axis I psychopathology and patient self-reported gradual versus acute onset of disease. In tandem, we performed serological analyses of serum anti-EBV and anti-HHV6 antibody titers and found no significant differences between the CFS and control patients.

U94 of human herpesvirus 6 is expressed in latently infected peripheral blood mononuclear cells and blocks viral gene expression in transformed lymphocytes in culture

Human herpesvirus 6 (HHV-6) like other herpesviruses, expresses sequentially immediate early (IE), early, and late genes during lytic infection. Evidence of ability to establish latent infection has not been available, but by analogy with other herpesviruses it could be expected that IE genes that regulate and transactivate late genes would not be expressed. We report that peripheral blood mononuclear cells of healthy individuals infected with HHV-6 express the U94 gene, transcribed under IE conditions. Transcription of other IE genes (U16/17, U39, U42, U81, U89/90, U91) was not detected. To verify that U94 may play a role in the maintenance of the latent state, we derived lymphoid cell lines that stably expressed U94. HHV-6 was able to infect these cells, but viral replication was restricted. No cytopathic effect developed. Furthermore, viral transcripts were present in the first days postinfection and declined thereafter. A similar decline in the level of intracellular viral DNA also was observed. These findings are consistent with the hypothesis that the U94 gene product of HHV-6 regulates viral gene expression and enables the establishment and/or maintenance of latent infection in lymphoid cells.

A practitioner's guide to human herpesvirus-6 (HHV-6) and human herpesvirus-7 (HHV-7)

Human herpesvirus-6 (HHV-6) and HHV-7 are newly recognized ubiquitous human viruses first discovered in patients with AIDS or lymphoproliferative disorders. Much more information is available about the clinical characteristics of infection with HHV-6 than HHV-7. Primary infection with HHV-6 occurs in early childhood and is most commonly manifested as an undifferentiated highly febrile illness, with seizures noted to be the most common complication. A subset of children develop the classic manifestations of roseola infantum or exanthem subitum. Other neurologic diseases in adults such as encephalitis and multiple sclerosis also have been linked to HHV-6; however, the role of HHV-6 in these clinical entities has not been fully elucidated. Although HHV-6 and HIV are both tropic for CD4+ lymphocytes and interact in vitro, there is no evidence at present that HHV-6 plays a role in HIV disease. HHV-7 is similar to HHV-6 in genetic organization and structure. Little is known of the clinical characteristics of infection with HHV-7 or its ability to cause disease in children or reactivation in adults.

Hepatitis C Virus Infection Involves CD34+Hematopoietic Progenitor Cells in Hepatitis C Virus Chronic Carriers

Although hepatitis C virus (HCV) mainly affects hepatocytes, infection is widespread and involves immunologically privileged sites. Whether lymphoid cells represent further targets of early HCV infection, or whether other cells in the hematopoietic microenvironment may serve as a potential virus reservoir, is still unclear. We studied whether pluripotent hematopoietic CD34+ cells support productive HCV infection and can be used to establish an in vitro infection system for HCV. Six patients were selected as part of a cohort of HCV chronic carriers who developed a neoplastic disease. Reverse transcriptase-polymerase chain reaction (RT-PCR) and branched DNA signal amplification assays were used to detect and quantitate HCV RNA in extracted nucleic acids from purified bone marrow and peripheral blood CD34+ cells. Direct in situ RT-PCR, flow cytometry analysis, and immunocytochemistry were applied to demonstrate specific viral genomic sequences and structural and nonstructural virus-related proteins in intact cells. Results indicated that both positive and negative HCV RNA strands and viral proteins were present in CD34+ cells from all HCV-positive patients and in none of the controls. Additional experiments showed that a complete viral cycle took place in CD34+ cells in vitro. Spontaneous increases in viral titers indicated that virions were produced by infected hematopoietic progenitor cells. To further define the cellular tropism, we attempted to infect CD34+ cells in vitro. We were unable to demonstrate viral uptake by cells. These findings suggest that HCV replication can occur in the early differentiation stages of hematopoietic progenitor cells, and that they may be an important source of virus production.

© 1998 by The American Society of Hematology.

Hepatitis C Virus Infection Involves CD34+Hematopoietic Progenitor Cells in Hepatitis C Virus Chronic Carriers

Although hepatitis C virus (HCV) mainly affects hepatocytes, infection is widespread and involves immunologically privileged sites. Whether lymphoid cells represent further targets of early HCV infection, or whether other cells in the hematopoietic microenvironment may serve as a potential virus reservoir, is still unclear. We studied whether pluripotent hematopoietic CD34+ cells support productive HCV infection and can be used to establish an in vitro infection system for HCV. Six patients were selected as part of a cohort of HCV chronic carriers who developed a neoplastic disease. Reverse transcriptase-polymerase chain reaction (RT-PCR) and branched DNA signal amplification assays were used to detect and quantitate HCV RNA in extracted nucleic acids from purified bone marrow and peripheral blood CD34+ cells. Direct in situ RT-PCR, flow cytometry analysis, and immunocytochemistry were applied to demonstrate specific viral genomic sequences and structural and nonstructural virus-related proteins in intact cells. Results indicated that both positive and negative HCV RNA strands and viral proteins were present in CD34+ cells from all HCV-positive patients and in none of the controls. Additional experiments showed that a complete viral cycle took place in CD34+ cells in vitro. Spontaneous increases in viral titers indicated that virions were produced by infected hematopoietic progenitor cells. To further define the cellular tropism, we attempted to infect CD34+ cells in vitro. We were unable to demonstrate viral uptake by cells. These findings suggest that HCV replication can occur in the early differentiation stages of hematopoietic progenitor cells, and that they may be an important source of virus production.

© 1998 by The American Society of Hematology.

Integration of human herpesvirus 6 in a Burkitt's lymphoma cell line

Human herpesvirus 6 (HHV-6) genome has been found in several human lymphoid malignancies, but configuration of the HHV-6 genome has not been well delineated. We established the HHV-6-positive, Epstein-Barr virus-negative Burkitt's lymphoma cell line Katata. In this study we investigated the status of the HHV-6 genome in Katata cells. Neither linear nor circular HHV-6 DNA was detected by Gardella gel analysis. The fluorescence in situ hybridization technique enabled us to directly visualize the integrated HHV-6 DNA at the single-cell level. Only one integrated site of viral DNA was detected in metaphase chromosomes and it was preferentially located at the long arm of chromosome 22 (22q13). Treatment of the cells with 12-O-tetradecanoyl-phorbol-13-acetate (TPA) or with calcium ionophore A23187 led to induction of the HHV-6 immediate-early gene as well as the late gene. Sodium n-butyrate also gave rise to expression of the HHV-6 genes. The TPA inducibility was synergistically enhanced when combined with A23187 or n-butyrate. Our study provides, for the first time, an in vitro model system of latent HHV-6 infection whose genome is integrated into host DNA of lymphoma cells.

Expression of human herpesvirus-6 antigens in benign and malignant lymphoproliferative diseases

Immunohistochemistry was used to look for the expression of human herpesvirus-6 (HHV-6) antigens in a well characterized series of benign, atypical, and malignant lymphoid lesions, which tested positive for the presence of HHV-6 DNA. A panel of specific antibodies against HHV-6 antigens, characteristic either of the early (p41) or late (p101K, gp106, and gp116) phases of the viral cycle, was applied to the lymphoid tissues from 15 non-Hodgkin's lymphomas, 14 Hodgkin's disease cases, 5 angioimmunoblastic lymphadenopathies with dysproteinemia, 14 reactive lymphadenopathies, and 2 cases of sinus histiocytosis with massive lymphadenopathy (Rosai-Dorfman disease). In lymphomatous tissues, the expression of late antigens was documented only in reactive cells, and mainly in plasma cells. Of interest, the expression of the early p41 antigen was detected in the so-called "mummified" Reed-Sternberg cells, in two Hodgkin's disease cases. In reactive lymphadenopathies, the HHV-6 late antigen-expressing cells were plasma cells, histiocytes, and rare granulocytes distributed in interfollicular areas. In both cases of Rosai-Dorfman disease, the p101K showed an intense staining in follicular dendritic cells of germinal centers, whereas the gp106 exhibited an intense cytoplasmic reaction in the abnormal histiocytes, which represent the histological hallmark of the disease. The expression of HHV-6 antigens is tightly controlled in lymphoid tissues. The lack of HHV-6 antigen expression in neoplastic cells and the limited expression in degenerating Reed-Sternberg cells argue against a major pathogenetic role of the virus in human lymphomagenesis. The detection of a rather unique pattern of viral late antigen expression in Rosai-Dorfman disease suggests a possible pathogenetic involvement of HHV-6 in some cases of this rare lymphoproliferative disorder.

Human herpesvirus type 6 variants identified by single-strand conformation polymorphism analysis

Six human herpesvirus 6 (HHV-6) variants were analyzed for heterogeneity using the polymerase chain reaction (PCR) and single-strand conformation polymorphism (SSCP). Two independent DNA regions were selected: a fragment of the gene U11 (position 18966-21578) coding for a basic phosphoprotein, the major antigenic structural protein pp100; and a fragment from an open reading frame (ORF) area of the gene U67, previously referred to as 13R (position 102458-103519), coding for a product of unknown function. The two PCR systems based on the above DNA sequences yielded products of 187 bp and 223 bp, respectively. DNA obtained from three laboratory reference strains (U1102, R104 and St.W.) and from HHV-6 infected peripheral white blood cells of bone marrow transplant patients and blood donors was used to test the applicability of two different SSCP analysis systems for the identification of HHV-6 variants using amplicons derived by PCR from the two genomic regions described above (U11 [pp100], U67 [13R-ORF]). The generation of characteristic SSCP patterns enables the rapid differentiation of HHV-6 A and B strains for the classification of variants derived from clinical samples, reducing the need for expensive and time-consuming direct sequencing analyses.

Human herpesvirus type 7 in Hodgkin's disease

Several lines of evidence have pointed to the involvement of a viral agent in the pathogenesis of Hodgkin's disease (HD). Therefore we investigated the presence of human herpesvirus type 7 (HHV-7) in 53 cases of HD by polymerase chain reaction (PCR), DNA in situ hybridization (ISH) and immunohistochemistry. HHV-7 DNA was frequently detected (68% of the cases) in HD biopsies by PCR independently of the histological type, whereas only 32% (P<0.05) of positive cases were found in 19 reactive lymph nodes. However, by applying the quantitative PCR technique, the majority of the samples showed a low level of viral load. Moreover, ISH for HHV-7 DNA was positive in a low number of small T lymphocytes and consistently negative in Hodgkin and Reed-Sternberg (HRS) cells, which appeared negative for HHV-7 also at immunohistochemistry. These results indicate that the high frequency of HHV-7 infection in HD: (i) is probably non-productive, (ii) mainly involves small lymphocytes belonging to the T-lineage, and (iii) is probably due to the recruitment of non-malignant reactive cells in HD tissue.

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.

Detection of human herpesvirus 6 DNA in serum by a microplate PCR-hybridization assay

PCR was performed on DNA extracts derived from clinical serum samples submitted for human herpesvirus 6 (HHV-6) serological examination. To detect amplified HHV-6 products, a hybridization-based microtiter plate assay (PCR ELISA; Boehringer Mannheim) was used. The assay system was found to be rapid, specific, and sensitive. Approximately three copies of a plasmid-based HHV-6 sequence could be detected, and no cross amplification was observed with HHV-7 genomic DNA. There was no correlation found between HHV-6 DNA detection and serological status in clinical serum samples from individuals more than 2 years old. On the other hand, in serum samples from infants less than 2 years old, a high rate of detection of HHV-6 DNA was observed in those who lacked immunoglobulin G and M antibodies to HHV-6 (55%). In this regard, PCR of serum DNA extracts may be used as a sensitive indicator of active HHV-6 infection in infants prior to their seroconversion.

Human Herpesvirus 6 (HHV-6)–Positive Burkitt's Lymphoma: Establishment of a Novel Cell Line Infected With HHV-6

Human herpesvirus 6 (HHV-6) DNA has been detected in several human lymphoproliferative disorders. We report a case of HHV-6–infected Burkitt's lymphoma, from which a cell line, designated Katata, has been established. Katata cells had an immature B-cell phenotype with an L3 morphology and carried a t(8; 14)(q24; q32) chromosomal abnormality. The HHV-6 DNA sequences were detected in both the patient's tumor cells and Katata cell line by polymerase chain reaction using three sets of primers that target different regions of HHV-6 DNA. The presence of HHV-6 DNA in Katata cells was also shown by Southern blot hybridization with the BamHI fragment of HHV-6. It is likely that the virus is in a latent state, since (1) virion-associated protein was not expressed in Katata cells, (2) transcriptional level of the immediate-early gene was very low, and (3) no viral particles were observed by electron microscopy. Katata cells were highly tumorigenic in nude mice and the tumor cells also contained HHV-6 DNA. We have successfully obtained several clonal lines by allowing the cells to form colonies in soft agarose and by the limiting dilution method. HHV-6 DNA was detectable in all 13 clones analyzed, suggesting that virtually all Katata cells are infected with HHV-6. This is the first report of a case of HHV-6+ Burkitt's lymphoma in the absence of Epstein-Barr virus. Furthermore, there has been no report of lymphoma cell lines that are persistently and nonproductively infected with HHV-6. The Katata Burkitt's lymphoma cell line, therefore, would provide a useful tool for studies of the mechanisms of HHV-6 latency and reactivation.

Human Herpesvirus 6 (HHV-6)–Positive Burkitt's Lymphoma: Establishment of a Novel Cell Line Infected With HHV-6

Human herpesvirus 6 (HHV-6) DNA has been detected in several human lymphoproliferative disorders. We report a case of HHV-6–infected Burkitt's lymphoma, from which a cell line, designated Katata, has been established. Katata cells had an immature B-cell phenotype with an L3 morphology and carried a t(8; 14)(q24; q32) chromosomal abnormality. The HHV-6 DNA sequences were detected in both the patient's tumor cells and Katata cell line by polymerase chain reaction using three sets of primers that target different regions of HHV-6 DNA. The presence of HHV-6 DNA in Katata cells was also shown by Southern blot hybridization with the BamHI fragment of HHV-6. It is likely that the virus is in a latent state, since (1) virion-associated protein was not expressed in Katata cells, (2) transcriptional level of the immediate-early gene was very low, and (3) no viral particles were observed by electron microscopy. Katata cells were highly tumorigenic in nude mice and the tumor cells also contained HHV-6 DNA. We have successfully obtained several clonal lines by allowing the cells to form colonies in soft agarose and by the limiting dilution method. HHV-6 DNA was detectable in all 13 clones analyzed, suggesting that virtually all Katata cells are infected with HHV-6. This is the first report of a case of HHV-6+ Burkitt's lymphoma in the absence of Epstein-Barr virus. Furthermore, there has been no report of lymphoma cell lines that are persistently and nonproductively infected with HHV-6. The Katata Burkitt's lymphoma cell line, therefore, would provide a useful tool for studies of the mechanisms of HHV-6 latency and reactivation.

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.

Herpesvirus 6 variant A infection after heart transplantation with giant cell transformation in bile ductular and gastroduodenal epithelium

Herpesvirus 6 (HHV-6) is a ubiquitous virus known to cause febrile syndromes and exanthema subitum in children. Less commonly, and particularly in organ transplant recipients, it may result in hepatitis, bone marrow suppression, interstitial pneunonitis, and meningoencephalitis. This report expands the spectrum of clinical disease associated with HHV-6 by documenting viral infection in a 44-year-old heart transplant recipient presenting with gastroduodenitis, pancreatitis, and hepatitis. On histopathologic examination, the gastric, duodenal, and bile ductular epithelium showed a multinucleate giant cell transformation similar to the cytopathic effect caused by the virus in human T-lymphocytes infected in vitro. Electron microscopy showed herpes particles with a thick tegument layer in the duodenum. Polymerase chain reaction amplified HHV-6 variant A sequences from multiple sites. Serology confirmed the presence of an acute HHV-6 infection. Thus, HHV-6 variant A can cause gastroduodenitis and pancreatitis in immunosuppressed individuals. Multinucleate giant cells and enveloped virions with a prominent tegument can be used as morphologic criteria to raise the possibility of HHV-6 infection in human biopsy tissue.

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.

Presence of human herpesvirus 6 variants A and B in saliva and peripheral blood mononuclear cells of healthy adults

Saliva and peripheral blood mononuclear cells (PBMCs) from 44 healthy young adults were tested for human herpesvirus 6 variants A and B (HHV-6A and -6B) DNA by a sensitive nested PCR. HHV-6B infection was ascertained in 98% of the subjects, and 95% were found to excrete variant B in their saliva. HHV-6A was found in the PBMCs of 16%, but was not detected in saliva samples.

Detection of human herpesvirus 6 sequences in lymphoma tissues by immunohistochemistry and polymerase chain reactions

We have analyzed one Hodgkin's and six non-Hodgkin's lymphomas for the presence of human herpesvirus 6 (HHV-6) and Epstein-Barr virus (EBV) DNA by polymerase chain reaction (PCR) and antigens by immunohistochemistry. A large cell B-cell lymphoma and a T-cell lymphoma were positive for HHV-6 antigens by immunohistochemistry. Using PCR primers from the HHV-6 ZVH14 transforming DNA segment, all seven tumors were positive. EBV DNA was not detected by PCR using sequences from EBV internal repeat-3 region as primers. The data suggest an etiologic involvement of HHV-6 in some human lymphomas. Although all seven of the lymphoma tissues examined contained HHV-6 DNA, expression of HHV-6 antigens was observed in only two cases, suggesting that expression of proteins was not required for transformation.

Presence of human herpesvirus type 6 in sporadic lymphoproliferative disorders. A comparative study

A supportive or causal role for human herpesvirus 6 (HHV-6) in lymphoproliferative disorders is still controversial. Different results were obtained in both tissue-based and serological investigations. We investigated 243 lymph node and salivary gland tissue biopsies for the presence of viral DNA by using a newly developed, highly sensitive nested polymerase chain reaction method. HHV-6 was detected in 39% of the non-Hodgkin's lymphomas, in 52% of Hodgkin's diseases, 64% of non-neoplastic lymph nodes, 23% of tumor metastases, and 50% of salivary gland biopsies. When correlating the patients' ages with the occurrence of HHV-6, we found a significantly higher percentage of positive samples in patients younger than 60 years of age (54%) than in older patients (35%). This age-related difference was found in all the lymphoproliferative disorders studied as well as in salivary gland biopsies. Taking patient's ages into account, we found no significant difference between the various groups of disorders concerning the percentage of HHV-6-positive samples.

B cell clonality in gastric lymphoid tissues of patients with Sjögren's syndrome

OBJECTIVE

To determine the prevalence of mucosa associated lymphoid tissue (MALT) in the stomach and of a possible antigen driven proliferation, in patients with Sjögren's syndrome (SS).

METHODS

Twenty one patients with primary SS and 80 dyspeptic controls underwent upper endoscopy. Lymphoid tissue and Helicobacter pylori were assessed by histopathological analysis. Epstein-Barr virus (EBV) or human herpes virus-6 (HHV-6) genome were studied by polymerase chain reaction (PCR) DNA amplification. Two PCR VDJ procedures were used to detect immunoglobulin heavy chain (IgH) gene rearrangement.

RESULTS

Organised MALT was found in 33.3% of the patients, compared with 21.5% of the controls (NS). H pylori infection was seen in 71% of patients and 63% of controls. Genomic EBV or HHV-6 was found in a minor portion of SS gastric tissues. B cell expansion was detected in nine of the 21 patients. Infectious agents in the stomach might have contributed to B cell clonality only in 55.5% of the cases. No strict relationship was found between lymphoid follicles and clonality.

CONCLUSION

Lymphoid accumulation in the gastric mucosa is common in Sjögren's syndrome, but full evidence for an antigen driven B cell expansion could not be demonstrated. Only a portion of those with clonal B cell expansion had evidence of an infectious agent. Other unknown infectious agents or factors related to the underlying disease (autoantigen) and its tissue environment may have a further role as possible causes of B clonal expansion in the gastric mucosa.

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

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

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.

Search for human herpesvirus 6 and human cytomegalovirus in bronchoalveolar lavage from patients with human immunodeficiency virus-1 and respiratory disorders

Virus isolation and viral DNA detection by the polymerase chain reaction were used to investigate the presence of human herpesvirus 6 (HHV-6) and human cytomegalovirus (HCMV) in bronchoalveolar lavage from 34 human immunodeficiency virus-1 (HIV-1)-infected patients with respiratory disorders. The aim was to assess the presence of reactivated HHV-6 in lung tissues for a subsequent evaluation of the frequency of virus involvement in respiratory clinical manifestations in the course of HIV-1 infection. Bronchoalveolar lavage samples were tested for the presence of HCMV, as a routine investigation within a protocol monitoring opportunistic infections in symptomatic HIV-1 patients. Whereas HCMV DNA was detected by the polymerase chain reaction in 12 bronchoalveolar lavage specimens, 10 of which were also positive for virus isolation, all samples were negative for HHV-6 by both virological procedures. The HHV-6 DNA finding in bronchoalveolar lavage from an HIV-1-seronegative patient with renal carcinoma, investigated accidentally together with the bronchoalveolar lavage specimens from HIV-1 seropositive patients, stressed the HHV-6 polymerase chain reaction-negative results in the bronchoalveolar lavage samples under study. It is concluded that the lung may be a target organ for HCMV infection in HIV-1-seropositive patients affected by respiratory symptoms but that this does not seem to be the case for HHV-6.

Immunophenotypic and molecular analyses of acquired immune deficiency syndrome-related and Epstein-Barr virus-associated lymphomas: a comparative study

Limited information is current available on the molecular and immunophenogenotypic characteristics of CD30-positive anaplastic large cell (ALC) lymphomas occurring in human immunodeficiency virus (HIV)-infected individuals. To address this issue, the authors have undertaken a combined analysis of these lymphomas in a comparison with other Epstein-Barr virus (EBV)-associated tumors in the setting of HIV infection. Twenty-one AIDS-related lymphomas, including five CD30-positive ALC and 11 small noncleaved cell (SNCC) lymphomas, and five Hodgkin's disease (HD) specimens were characterized regarding the immunophenogenotypic features, the frequency and subtype distribution of EBV (as defined by in situ hybridization [ISH], Southern blot, and a polymerase chain reaction [PCR] amplification of the EBV nuclear antigen-2 [EBNA-2] region) antigen expression (latent membrane protein-1 [LMP-1], EBNA-2, and for alterations of the tumor suppressor gene p53. Combined immunophenotypic and immunogenotypic analyses showed a derivation from anomalously matured B cells in four of five CD30-positive ALC lymphomas, whereas SNCC showed features of mature B cells; no evidence of immunoglobulin or TCR gene rearrangement could be obtained in HD cases. Combined ISH and Southern blot analyses revealed that EBV was more strictly associated with HD (five of five) and CD30-positive ALC lymphomas (four of five) than with SNCC lymphomas (four of 11). EBV-positive samples from CD30-positive ALC lymphomas carried type 1 EBV (two of two specimens tested), whereas both EBV subtypes were observed in SNCC lymphomas and HD samples. All three forms of viral latent gene expression were found in the EBV positive CD30-positive ALC lymphomas. SNCC specimens did not express LMP-1 or EBNA-2, whereas HD specimens expressed LMP-1 (four of five tested) but no EBNA-2. Immunostaining for ZEBRA was consistently negative. HHV-6 DNA sequences were detected by PCR in one SNCC of the 19 specimens analyzed. Three out of five CD30-positive ALC lymphoma specimens and six of 10 SNCC showed nuclear staining for p53. No mutation was detected in any of the three CD30-positive Alc lymphoma analyzed, whereas an aberrant SSCP pattern was found in all the four SNCC samples tested. At variance with SNCC lymphomas, AIDS-related B-cell CD30- positive ALC lymphomas are strictly associated with EBV infection and may also express the broad lymphoblastoid cell line-like (LMP-1-positive, EBNA-2-positive) pattern, and lack p53 genetic lesions. Unlike EBV, HHV-6 probably does not represent a relevant factor involved in the pathogenesis of CD30-positive ALC and other HIV related lymphomas.

On the role of human herpesvirus 6 in viral latency in nervous tissue and in cerebral lymphoma

Latent infections by human herpesvirus 6 (HHV6) in nervous tissue and its role in human disease are poorly understood. For the present study, an improved PCR method has been applied to brain tissue samples from 5 different brain regions from 20 forensic post-mortem cases without neurologic involvement. Spleen tissue from these cases as well as 5 cerebral lymphoma tissue samples were also examined. HHV6 DNA was detected in 3 of 20 brains. The viral sequences could be amplified from cortical brain tissue from these 3 cases. In one of these cases, HHV6 DNA was detectable in two separate tissue samples. PCR was negative in brain lymphoma and spleen tissue. These findings point toward HHV6 latency in brain tissue and might thus support the reported glial tropism of this virus. No role could be found for HHV6 in the pathogenesis of cerebral lymphoma.

Targeted integration of human herpesvirus 6 in the p arm of chromosome 17 of human peripheral blood mononuclear cells in vivo

Out of 64 cases of non-Hodgkin's lymphomas (NHL), 55 cases of Hodgkin's disease (HD) and 31 cases of multiple sclerosis (MS), 2 NHL, 7 HD and 1 MS cases were found positive by polymerase chain reaction (PCR) for the presence of HHV-6 sequences in pathologic lymph nodes of the lymphomas and in peripheral blood mononuclear cells (PBMCs) of MS. A further analysis of the PBMCs of the PCR positive cases by standard Southern blot technique revealed only 2 NHL, 3 HD and 1 MS cases as positive, indicating that these six patients have an unusually high viral copy number in the PBMCs. Restriction analysis, carried out using probes representative of different regions of the virus, showed that three cases retain only a deleted portion of the viral genome. In the remaining three cases a complete viral genome was present, containing the right end sequences in which the rep-like gene, possibly crucial to the viral and cellular life cycle, is located. The analysis by pulsed field gel electrophoresis (PFGE) of the total DNA of the PBMCs obtained directly, without culture from PBMCs of these last three cases (1 NHL, 1 HD, and 1 MS), using the same probes, showed the absence of free viral molecules and the association of viral sequences with high molecular weight DNA. These results are consistent with in vivo integration of the entire virus in the cellular genome. A further study of the same patients with chromosome fluorescence in situ hybridization (FISH) showed in all the three cases the presence of a specific hybridization site, located at the telomeric extremity of the short arm of chromosome 17 (17p13), suggesting that this location is at least a preferred site of an infrequent, but possibly biologically important, integration phenomenon.

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 herpesviruses 6 and 7 in salivary glands and shedding in saliva of healthy and human immunodeficiency virus positive individuals

The presence of human herpesvirus 6 (HHV-6) and human herpesvirus 7 (HHV-7) was investigated by the polymerase chain reaction in saliva specimens from healthy persons, donors affected by common cold or recurrent aphthous ulceration (RAU), and human immunodeficiency virus (HIV) positive patients, and in salivary gland biopsies. The sensitivity of the technique made it possible to detect as few as 5-10 target molecules in 15 microliters of saliva. HHV-6 was present in 63% of salivary gland biopsies and in 3% of salivas from healthy persons. No significant difference in the presence of HHV-6 was detected in specimens from donors with common cold, RAU, or HIV-infected patients. HHV-7 was present in 75% of salivary glands and in 55% of salivas from healthy persons. HHV-7 was detected with similar frequency in salivas from donors with common cold or RAU. Salivas from HIV-infected patients harbored HHV-7 with higher frequency (81%) and increased viral load. These results show that salivary glands are a site of persistent infection for both HHV-6 and HHV-7. However, the two viruses seem to differ in their biological properties: 1) HHV-6 is rarely present in saliva in detectable amounts, while HHV-7 is frequently detected; and 2) immunosuppression by acquired immunodeficiency syndrome (AIDS) increases the frequency of detection and the viral load of HHV-7, but does not have a significant effect on HHV-6 shedding in saliva.