Human B-lymphotropic virus (human herpesvirus-6)

Multistage carcinogenesis utilizing human genital cells and human papillomaviruses

The preponderance of evidence indicates that a subset of human papillomaviruses are important etiological agents for cervical cancer. However, the necessity of other agents as well as cellular events is recognized because not all women with papillomaviruses develop cancer. Therefore, the exact role of papillomaviruses in the multistage carcinogenesis process is unclear. Regulation of specific viral genes is important to the malignant process. The current study demonstrates that human herpesvirus-6, another ubiquitous virus, can infect genital epithelial cells and upregulate the expression of relevant papillomavirus genes. Thus, it can be considered a cofactor for cancer.

Detection of human herpesvirus-6 in paraffin-embedded tissue of cervical cancer by polymerase chain reaction

The polymerase chain reaction (PCR) was used to detect human herpesvirus-6 (HHV-6) DNA sequences from paraffin-embedded tissue from cervical cancer patients. Two of eight cases were positive for HHV-6 using two sets of HHV-6 primers. Hybridization of PCR products with specific radioisotope-labeled oligonucleotide probes confirmed the results. Furthermore, HHV-6 typing was possible by adapting restriction endonuclease digestion of PCR product. This method is useful for retrospective studies in investigating the etiologic role of HHV-6 in the development of human diseases.

Prevalence of human herpesvirus 6 antibody among isolated Amazonian Amerindian communities in Brazil

Human herpesvirus 6 (HHV6) antibody was detected by the anticomplement immunofluorescence test in 65 of 592 serum samples (10.9%) obtained from Amerindians belonging to 4 remote communities inhabiting the Amazon Region of Brazil. Seropositivity rates ranged from 5.4% in the Oyampí to 14.9% in the Tucano. Among the Mekranoiti and Tiriyo, the seroprevalence rates were 12.5% and 11.8%, respectively. In children aged 0-10 years, the prevalences of HHV6 antibody ranged from 5.2% to 24.2%, among the Oyampí and Mekranoiti tribes, respectively. In the 11-20 and > 20 years old age groups, percentages of positivity ranged, in the former group, from 9.5% to 17.5% in the Oyampí and Tucano, respectively and, in the latter group, from 1.3% in the Oyampí to 14.8% in the Tucano. The prevalences of HHV6 antibody decreased regularly through the first 3 age-groups in the Mekranoiti and Tiriyo. In addition, frequencies of seropositivity were consistently higher in males than in females in the Mekranoiti (P < 0.05), Oyampí and Tiriyo tribes.

Human herpesvirus 6 infects cervical epithelial cells and transactivates human papillomavirus gene expression

To examine whether human herpesvirus 6 (HHV-6) is capable of infecting human cervical epithelial cells and altering expression of human papillomavirus (HPV) genes, HPV-immortalized or -transformed carcinoma cell lines were infected with HHV-6 variant A. No cytopathic effect was observed in infected cervical cells. However, immunofluorescence indicated that infected cells expressed early-late proteins of HHV-6 by day 3 postinfection. HHV-6 DNA was also detected by Southern blot hybridization after infection and persisted through continued subculture in an episomal state as proven by Gardella gel electrophoresis and fluorescence in situ hybridization. HHV-6 infection enhanced expression of HPV RNAs encoding the viral oncoproteins E6 and E7. Transient transfection assays showed that two HHV-6 molecular clones, pZVB-70 and pZVH-14, upregulated transcription 9- to 15-fold from a receptor plasmid containing the HPV type 18 regulatory sequences which control transcription in vivo. Cervical carcinoma cells infected with HHV-6 induced more rapid development of tumors in mice than did noninfected cells. These results are the first evidence that human cervical epithelial cells can be infected with HHV-6 and that HHV-6 contains transactivators which stimulate the HPV-transforming genes.

In vitro susceptibility of Macaca nemestrina to human herpesvirus 6: a potential animal model of coinfection with primate immunodeficiency viruses

Human herpesvirus 6 (HHV-6), a lymphotropic herpesvirus, has been suggested as a potential cofactor in the acquired immunodeficiency syndrome (AIDS). Previous studies indicate that HHV-6 has a restricted range of susceptible species. In this study, we tested the in vitro susceptibility to HHV-6 of Macaca nemestrina (pig-tailed macaque), a species that has been found to be infectable by human immunodeficiency virus type I in vivo and that develops an AIDS-like syndrome following simian immunodeficiency virus (SIV) infection. Two different HHV-6 isolates (HHV-6GS and HHV-6BA), belonging to the two major HHV-6 variants (A and B, respectively), were employed. Both viruses induced a productive and cytopathic infection in phytohemagglutinin-stimulated peripheral blood T lymphocytes from M. nemestrina. In contrast, only HHV-6BA (variant B) was able to replicate in lymphocytes from Macaca mulatta (rhesus macaque). Moreover, HHV-6GS and SIVsmE660 productively coinfected individual M. nemestrina lymphocytes, resulting in increased levels of SIV replication. Genetic sequences of HHV-6 were not amplified by polymerase chain reaction from peripheral blood mononuclear cells of several adult M. nemestrina, suggesting that these animals, unlike humans, are not commonly infected by HHV-6, or a related virus. Thus, M. nemestrina may represent an optimal animal model system to investigate the in vivo interactions between HHV-6 and the primate immunodeficiency viruses.

A model to study viral and cytokine involvement in Sjögren's syndrome

To investigate mechanisms that may be important in the pathogenesis of Sjögren's syndrome (SS) we developed a protocol for the growth of salivary gland epithelial cells in culture. We examined the effect that viral infection has on the cellular location of the autoantigen La. Autoantibodies to La are common in SS and it has been proposed that viral infection may result in cell membrane expression of La. Co-expression of MHC class II molecules in infected cells could lead to the presentation of La peptides to the immune system. Advenovirus infection of salivary gland epithelial cells resulted in an altered nuclear staining of La. Treatment with interferon-gamma resulted in the expression of La in the cell cytoplasm and HLA-DR molecules at the cell surface. These findings suggest that a cytokine-driven mechanism may generate an autoimmune response to La in SS. Using the polymerase chain reaction (PCR) we tested salivary gland epithelial cell cultures for the presence of human herpesvirus-6 (HHV-6) and Epstein-Barr virus (EBV). Only HHV-6 was detected in 2 of 10 salivary gland epithelial cell cultures although the presence of HHV-6 was not associated with SS. Primary salivary gland cultures may prove useful as an in vitro model to study mechanisms of autoimmunity in SS.

Activation of the Epstein-Barr virus replicative cycle by human herpesvirus 6

One common attribute of herpesviruses is the ability to establish latent, life-long infections. The role of virus-virus interaction in viral reactivation between or among herpesviruses has not been studied. Preliminary experiments in our laboratory had indicated that infection of Epstein-Barr virus (EBV) genome-positive human lymphoid cell lines with human herpesvirus 6 (HHV-6) results in EBV reactivation in these cells. To further our knowledge of this complex phenomenon, we investigated the effect of HHV-6 infection on expression of the viral lytic cycle proteins of EBV. Our results indicate that HHV-6 upregulates, by up to 10-fold, expression of the immediate-early Zebra antigen and the diffuse and restricted (85 kDa) early antigens (EA-D and EA-R, respectively) in both EBV producer and nonproducer cell lines (i.e., P3HR1, Akata, and Raji). Maximal EA-D induction was observed at 72 h post-HHV-6 infection. Furthermore, expression of late EBV gene products, namely, the viral capsid antigen (125 kDa) and viral membrane glycoprotein gp350, was also increased in EBV producer cells (P3HR1 and Akata) following infection by HHV-6. By using dual-color membrane immunofluorescence, it was found that most of the cells expressing viral membrane glycoprotein gp350 were also positive for HHV-6 antigens, suggesting a direct effect of HHV-6 replication on induction of the EBV replicative cycle. No expression of late EBV antigens was observed in Raji cells following infection by HHV-6, implying a lack of functional complementation between the deleted form of EBV found in Raji cells and the superinfecting HHV-6. The susceptibility of the cell lines to infection by HHV-6 correlated with increased expression of various EBV proteins in that B95-8 cells, which are not susceptible to HHV-6 infection, did not show an increase in expression of EBV antigens following treatment with HHV-6. Moreover, UV light-irradiated or heat-inactivated HHV-6 had no upregulating effect on the Zebra antigen or EA-D in Raji cells, indicating that infectious virus is required for the observed effects of HHV-6 on these EBV products. These results show that HHV-6, another lymphotropic human herpesvirus, can activate EBV replication and may thus contribute to the pathogenesis of EBV-associated diseases.

Identification and mapping of the gene encoding the glycoprotein complex gp82-gp105 of human herpesvirus 6 and mapping of the neutralizing epitope recognized by monoclonal antibodies

Monoclonal antibodies (MAbs) 2D4, 2D6, and 13D6 against human herpesvirus 6 (HHV-6) variant A strain GS recognized virion envelope glycoprotein complex gp82-gp105 and neutralized the infectivity of HHV-6 variant A group isolates. A 624-bp genomic fragment (82G) was identified from an HHV-6 strain GS genomic library constructed in the lambda gt11 expression system by immunoscreening with MAb 2D6. Rabbit antibodies against the fusion protein expressed from the genomic insert recognized glycoprotein complex gp82-gp105 from HHV-6-infected cells, thus confirming that the genomic fragment is a portion of the gene(s) that encodes gp82-gp105. This genomic insert hybridized specifically with viral DNAs from HHV-6 variant A strains GS and U1101 under high-stringency conditions but hybridized with HHV-6 variant B strain Z-29 DNA only under low-stringency conditions. DNA sequence analysis of the insert revealed a 167-amino-acid single open reading frame with an open 5' end and a stop codon at the 3' end. Hybridization studies with HHV-6A strain U1102 DNA localized the gp82-gp105-encoding gene to the unique long region near the direct repeat at the right end of the genome. To locate the neutralizing epitope(s) recognized by the MAbs, a series of deletions from the 3' end of the gene were constructed with exonuclease III, and fusion proteins from deletion constructs were tested for reactivity with MAbs in a Western immunoblot assay. Sequencing of deletion constructs at the reactive-nonreactive transition point localized the epitope recognized by the three neutralizing MAbs within or near a repeat amino acid sequence (NIYFNIY) of the putative protein. This repeat sequence region is surrounded on either side by two potential N-glycosylation sites and three cysteine residues.

Human herpesvirus 6 and multiple sclerosis: survey of anti-HHV-6 antibodies by immunofluorescence analysis and of viral sequences by polymerase chain reaction

A possible involvement of human herpesvirus 6 (HHV-6) infection in the pathogenesis of multiple sclerosis (MS) was investigated. The immunofluorescence analysis of sera from 126 MS patients showed significantly higher anti-HHV-6 antibody titres in MS sera than in 500 normal controls. A polymerase chain reaction (PCR) assay of the peripheral blood mononuclear cell (PBMC) DNAs of 31 MS patients and 24 normal subjects was positive in one normal control and in one MS patient. The Southern blot analysis indicated an unexpectedly high level of viral sequences in the MS patient, but not in the control. Since viral sequences are rarely present in MS subjects, the high anti-HHV-6 antibody titres found in MS are likely to be related to immune impairment rather than reactivation of a latent infection.

Human herpesvirus-6 infections in infants admitted to hospital

Virological studies were carried out on 3 to 36-month-old patients admitted to the Children's Hospital of the University of Modena with febrile syndrome from September 1990 to February 1991. Virological tests were carried out for human herpesvirus-6 (HHV-6), Epstein-Barr virus (EBV), cytomegalovirus (CMV), herpes simplex virus 1 (HSV-1), adenoviruses, parainfluenza viruses 1, 2 and 3, respiratory syncytial virus (RSV) and influenza viruses A and B. Viral infections were confirmed in 60.7% patients: 39.6% were correlated with HHV-6, 5.4% with EBV, 5.4% with both HHV-6 and EBV, 5.4% with adenoviruses, 1.8% with HSV-1, 1.8% with CMV and 1.8% with an unidentified herpes-like lymphotropic virus. HHV-6 isolates were obtained from either peripheral blood lymphocytes (PBLs) or pharyngeal secretion of the infected children. HHV-6 infections included both primary infections (72%) and reactivations (28%). Among HHV-6 infected children, 40%, with exanthem subitum, had infections presenting serological evidence of primary infection and virus isolation from PBLs. The remaining cases of primary infection and the cases of reactivation were found in patients with febrile syndrome without rash (60%). HHV-6 isolates were obtained either from PBLs or pharyngeal secretions from these patients. Southern blot hybridization of the DNAs of 4 HHV-6 isolates showed that the circulating HHV-6 strains all appeared similar, but differed from the HHV-6 strain U1102 used as a positive control.

Lymphadenitis and lymphoproliferative lesions associated with the human herpes virus-6 (HHV-6)

A newly described herpes virus, human herpes virus 6, (HHV-6), has been linked to exanthema subitum but beyond this its pathogenetic impact remains to be determined. A large body of evidence links it to various lymphoproliferative disorders and this study was conducted to identify forms of lymphoproliferation linked to HHV-6. We studied biopsy samples from 32 patients with disorders of the lymphatic system for the presence of HHV-6, both by polymerase chain reaction (PCR) and in-situ hybridization (ISH) methods, as well as Epstein-Barr virus (EBV) viral DNA, clonal rearrangements of the antigen receptor genes and bcl-2 genes. All the specimens were studied morphologically and a clinical follow-up of up to 4 years was obtained. Seven of the 32 patients were positive for HHV-6 DNA and the remainder were negative. Two of these HHV-6 positive specimens, both from elderly persons, showed a similar distinct histological pattern diagnosed as malignant B-cell lymphoma of high grade malignancy. Two other HHV-6-positive specimens were reactive lymphadenopathies occurring in younger adults. In addition, one further specimen with evidence of EBV-involvement was from a patient who died 3 months after biopsy with fatal infectious mononucleosis (IM). These five samples had HHV-6 DNA by PCR and ISH. Two specimens without specific histologic abnormalities showed evidence of HHV-6 only by PCR but not by ISH. Both high grade malignant lymphomas showed clonal proliferations, one of monoclonal B-cells and the other of clonal T-cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Viral involvement in Hodgkin's disease

The etiology of Hodgkin's disease (HD) is unknown, but a growing body of evidence suggests that the Epstein-Barr virus (EBV) plays a role in a proportion of cases. Clonal EBV genomes have been detected in affected tissues, and EBV has been localized to Reed-Sternberg (RS) cells, the putative malignant cells in HD. EBV latent genes, including the EBER RNAs and the latent membrane protein, LMP-1, are expressed by RS cells. These data suggest that EBV is playing a role in the pathogenesis of HD; however, it is clearly not involved in all cases. Using in situ hybridization, we can detect EBV within the RS cells in approximately 40% of cases. Epidemiological data suggest that HD is a heterogeneous condition and the distribution of EBV-associated cases is not random. Studies from several groups indicate that mixed cellularity cases are more likely to be EBV-associated than nodular sclerosis cases. Our data further suggest that the majority of pediatric and older cases of HD are EBV-associated, whereas the RS cells in young adult cases only rarely harbor EBV. We therefore speculate that another virus is responsible for the young adult peak in incidence which is seen in developed countries.

Human herpesvirus 7 is a T-lymphotropic virus and is related to, but significantly different from, human herpesvirus 6 and human cytomegalovirus

An independent strain (JI) of human herpesvirus 7 (HHV-7) was isolated from a patient with chronic fatigue syndrome (CFS). No significant association could be established by seroepidemiology between HHV-7 and CFS. HHV-7 is a T-lymphotropic virus, infecting CD4+ and CD8+ primary lymphocytes. HHV-7 can also infect SUP-T1, an immature T-cell line, with variable success. Southern blot analysis with DNA probes scanning 58.8% of the human herpesvirus 6 (HHV-6) genome and hybridizing to all HHV-6 strains tested so far revealed homology to HHV-7 with only 37.4% of the total probe length. HHV-7 contains the GGGTTA repetitive sequence, as do HHV-6 and Marek's disease chicken herpesvirus. DNA sequencing of a 186-base-pair fragment of HHV-7(JI) revealed an identity with HHV-6 and human cytomegalovirus of 57.5% and 36%, respectively. Oligonucleotide primers derived from this sequence (HV7/HV8, HV10/HV11) amplified HHV-7 DNA only and did not amplify DNA from other human herpesviruses, including 12 different HHV-6 strains. Southern blot analysis with the p43L3 probe containing the 186-base-pair HHV-7 DNA fragment hybridized to HHV-7 DNA only. The molecular divergence between human cytomegalovirus, on the one hand, and HHV-6 and HHV-7, on the other, is greater than between HHV-6 and HHV-7, which, in turn, is greater than the difference between HHV-6 strains. This study supports the classification of HHV-7 as an additional member of the human beta-herpesviruses.

Human herpesvirus-6 infection and bone marrow transplantation

Human herpesvirus-6 (HHV-6) is ubiquitous in the human population and causes exanthem subitum, a benign disease seen in infancy. However it also produces a wide spectrum of clinical manifestations including cases with a fatal outcome. The virus remains latent in several organs, including the kidneys, liver, lymph/nodes and salivary glands, after the primary infection and reactivates when immune function is impaired. Reactivation of the virus occurred in a half of the bone marrow recipients 2 to 4 weeks after bone marrow transplantation (BMT). It remains to be established whether HHV-6 in fact causes the fever and rash observed in recipients who have reactivation of the virus. The data reviewed here will be required to compare with those of human herpesvirus 7 and a different group of HHV-6.

Antigenic relationships among human herpesvirus-6 isolates

Human herpesvirus 6 (HHV-6) prototype isolate GS is a newly identified lymphotropic herpesvirus and several subsequent herpes isolates were recognized as HHV-6 by their hybridization to a HHV-6(GS) DNA probe pZVH14. DNA restriction analysis and in vitro tropism studies show that HHV-6 isolates can be divided into two groups, designated group A and group B. Antigenic relationships among 15 HHV-6 isolates belonging to these two groups were examined using rabbit antibodies against HHV-6(GS) infected cells, 11 monoclonal antibodies against three glycoproteins and four non-glycoproteins of HHV-6(GS), and sera from 136 healthy adults. More than 20 polypeptides from all these isolates were immunoprecipitated by rabbit polyclonal antibodies against HHV-6(GS) infected cells. Reactivities of monoclonal antibodies segregated these isolates into the same two groups. Group A contains HHV-6(GS), HHV-6(U1102) from a Ugandan acquired immunodeficiency syndrome (AIDS) patient, and nine other HHV-6 isolates from various disorders. HHV-6(Z-29) from a Zairian AIDS patient, HHV-6(SF) isolated from the saliva of a human immunodeficiency virus (HIV)-infected individual, HHV-6(OK) from a child with exanthem subitum, and HHV-6(DC) from a leukopenia patient are in group B. Eighty-one percent of the sera showed similar antibody titer in immunofluorescence assay with group A HHV-6(GS) and group B HHV-6(Z-29) infected cells and 19% of the sera showed two- to four-fold antibody titer differences. The mobilities of many of the polypeptides immunoprecipitated from group A HHV-6(GS) and group B HHV-6(Z-29) infected cells were different and sera showed differences in the quantities and nature of polypeptides immunoprecipitated.(ABSTRACT TRUNCATED AT 250 WORDS)

HHV-6 inhibition by two polar compounds

Dimethyl sulphoxide and dimethyl formamide, two polar compounds and powerful cell differentiation inducers, inhibit HHV-6 infection when added to HHV-6-infected HSB2 cultures. This was established by a delay in the time-course of infection and in the development of virus-induced cytopathic effects. Furthermore, viral titration of supernatants showed a significant reduction (3 log10) of the number of infectious particles. Electron microscopy confirmed that viable cells and extracellular virions were present in the cultures containing the polar compounds, while in the non-treated cultures all cells were lysed and no extracellular virus was evident. The mode of action of these compounds is still unclear and warrants further investigation.

Evaluation of variables in immunofluorescence procedures for the detection of antibodies against human herpesvirus 6 (HHV-6)

Ten human sera were used to study different parameters, namely, methods of smear preparation and fixation, and age of infected HSB-2 cells in order to optimize indirect immunofluorescence assay (IFA) and anticomplement immunofluorescence (ACIF) procedures to measure antibody levels against HHV-6. Results showed a greater sensitivity of rapid smear drying and methanol fixation over conventional acetone smear preparation. Cells harvested 6 days after infection and fixed with methanol exhibited a sharper and more intense fluorescence. IFA titers were higher than those obtained with ACIF, although the latter procedure enabled the distinction between three fluorescent sites. Reactivity pattern of individual sera against infected cells was variable and indicated that the human immune response to HHV-6 is directed against different antigens. An easier interpretation and a better definition of the fluorescence of HSB-2 cell line infected with HHV-6 strain Dv is obtained with the following conditions: cells should be harvested at 5-8 days after infection (at the giant cell stage of infection), cell smears have to be dried quickly before fixation with methanol at -20 degrees C, and finally, they should be stained by IFA.

Newest human herpesvirus (HHV-6) in the Guillain-Barré syndrome and other neurological diseases

To investigate the presence of human herpesvirus-6 (HHV-6) in patients affected by Guillain-Barré syndrome (GBS) and by other neurological diseases (OND), we examined by indirect immunofluorescence analysis (IFA) the sera and cerebrospinal fluid (CSF) from 28 GBS and 63 OND. Moreover, we tested 150 blood donors (BD) to appreciate the diffusion of HHV-6 infection in the Italian adult healthy population. We found a significantly higher titre of antibody to HHV-6 in the GBS patients compared with OND and BD, although the pathogenicity of the virus is not known.

Antibodies to human herpes virus-6 and clinical course in patients with Hodgkin's disease

Serial serum samples from 37 patients with Hodgkin's disease (HD) and 39 healthy controls were studied for antibodies to human herpes virus-6 (HHV-6) using ELISA and indirect immunofluorescent antibody (IFA) tests and to the Epstein-Barr virus (EBV) using a radio-complement fixation assay. Antibodies to HHV-6 in the pre-treatment sera from the HD patients were not significantly different from those of controls, but significant changes in titers related to clinical course were noted among the HD patients. HHV-6 IFA titers increased significantly in the course of follow-up in patients who relapsed and decreased significantly over time in patients who did not. These serologic studies support tissue-based investigations indicating that EBV plays a greater etiologic role in HD than HHV-6, although HHV-6 serology may be of prognostic value or may assist in identifying individuals with immunologic abnormalities. The identification of diverse HHV-6 antibody patterns using different assays may reflect the presence of a number of antibodies with varying implications, similar to those identified for EBV.

Hodgkin's disease

The epidemiological features of Hodgkin's disease (HD) suggest that it is a heterogeneous condition which may have different aetiologies in different age groups. The risk factors for the development of HD in young adults suggest that delayed exposure to a common infectious agent may be involved in this age group. Seroepidemiological studies have shown that HD patients have elevated antibody titres to Epstein-Barr virus (EBV) and the elevated titres have been shown to precede the diagnosis of HD. Recent molecular studies provide support for the idea that EBV is involved in the pathogenesis of HD. EBV genomes are consistently found in a proportion of tumour biopsies, the EBV-infected cells are clonal and the EBV genomes have been localized to Reed-Sternberg cells. Furthermore, EBV latent gene products are expressed by the Reed-Sternberg cells. The majority of HD samples from patients aged greater than 50 years and less than 15 years are EBV positive, whereas the minority (less than 15%) of samples from young adults contain detectable EBV DNA. The results suggest that EBV plays a role in HD in children and older adults but that other agents, possibly other viruses, are involved in young adults.

Lymphadenopathy in connection with human herpes virus type 6 (HHV-6) infection

Two siblings and their mother developed afebrile generalized lymphadenopathy. The lymph nodes were movable and painless. During the course of the illness, the mother and one child developed an uncharacteristic rash. Increased titers of human herpes virus type 6 (HHV-6) antibodies were found in all three family members and in an unrelated patient with lymphadenitis colli. The enlarged lymph nodes decreased in size within several weeks. We speculate these symptoms to be caused by an infection with this lymphotropic virus.

Seroepidemiological correlations of antibodies to human herpesviruses and human immunodeficiency virus type 1 in African patients

A seroepidemiological evaluation of the humoral immune response against human herpes viruses was carried out in patients with and without HIV infection in Tanzania to study the role of these viruses as a cofactor in AIDS. Serum specimens were obtained from 321 outpatients and 100 healthy schoolchildren of a rural population in the Kagera Region, Tanzania, and from 149 inpatients of an urban population in Dar-es-Salaam, Tanzania. The data were analysed by logistic models taking into account demographic variables. The data obtained revealed no differences in the prevalence of antibodies to human herpes viruses between the different groups. Therefore, our study under the present conditions and the observed stages of AIDS does not suggest an influence of HIV infection on human herpesvirus infection or serologic response.

Genomic polymorphism, growth properties, and immunologic variations in human herpesvirus-6 isolates

Fifteen human herpesvirus-6 (HHV-6) isolates from normal donors and patients with AIDS, systemic lupus erythematosis, chronic fatigue syndrome, collagen-vascular disease, leukopenia, bone marrow transplants, Exanthem subitum (roseola), and atypical polyclonal lymphoproliferation were studied for their tropism to fresh human cord blood mononuclear cells, growth in continuous T cell lines, reactivity to monoclonal antibodies, and by restriction enzyme banding patterns. All isolates replicated efficiently in human cord blood mononuclear cells, but mitogen stimulation of the cells prior to infection was required. The ability to infect continuous T-cell lines varied with the isolates. Isolates similar to GS prototype infected HSB2 and Sup T1 cells and did not infect Molt-3 cells, whereas isolates similar to Z-29 infected Molt-3 cells but not HSB2 and Sup T1 cells. Some of the monoclonal antibodies directed against the HHV-6 (GS) isolate showed reactivity with all isolates tested, but others only reacted with HHV-6 isolates similar to the GS isolate and not with those similar to Z-29 isolate. Restriction enzyme analysis using EcoRI, BamHI, and HindIII revealed that HHV-6 isolates from roseola, bone marrow transplant, leukopenia, and an HIV-1-positive AIDS patient from Zaire (Z-29) were closely related but distinct from GS type HHV-6 isolates. Based on the above findings, we propose that, like herpes simplex virus types 1 and 2, the 15 HHV-6 isolates analyzed can be divided into group A (GS type) and group B (Z-29 type).

Seroepidemiology of human herpesvirus-6 in pregnant women from different parts of the world

The prevalence of HHV-6 IgG was studied in 11 different countries across several continents: Morocco, Burkina-Faso, Congo, Ivory Coast, Mali, Niger, Senegal, Togo, Ecuador, Martinique, and France. The study group consisted of 550 pregnant women, representative of the general adult population in each country. Antibodies were detected by immunofluorescence assay on HSB-2 cells infected with HHV-6. Each serum was tested at nine dilutions (1:20 to 1:5,120), sera greater than or equal to 20 being considered positive. For the negative antigen control, we used mock-infected HSB-2 cells. Great differences were seen between separate areas: Morocco showed both low prevalence (20%) and a low geometric mean titer (12), whereas sub-Saharan Africa displayed high prevalences (60% to 90%) and variable geometric mean titers (34 to 229). This study revealed a prevalence of 92% for Ecuador, significantly higher than the prevalence for Martinique (50%), yet both countries had very low antibody titers compared with those found in Africa. The prevalence in France (76%) was similar to previous results from other European countries.

Identification, characterization, and sequence analysis of a cDNA encoding a phosphoprotein of human herpesvirus 6

Human herpesvirus 6 (HHV-6)-specific monoclonal antibody (Mab) 9A5D12 reacted with the nucleus of HHV-6 strain GS-infected cells and immunoprecipitated a phosphorylated polypeptide with an approximate size of 41 kDa, designated HHV-6 P41. A 110-kDa polypeptide was also immunoprecipitated by the MAb. These polypeptides were synthesized early in infection, and the synthesis was greatly reduced by phosphonoacetic acid. Polypeptides with identical sizes were recognized by the MAb from cells infected with an additional eight HHV-6 strains. A 2.1-kb cDNA insert was identified from an HHV-6(GS) cDNA library constructed in the lambda gt11 expression system by using MAb 9A5D12. This cDNA insert hybridized specifically with viral DNA from HHV-6 strains GS and Z-29 and with two predominant transcripts with approximate sizes of 2.5 and 1.2 kb from infected cells. The reactivity of the MAb with a fusion protein expressed in the prokaryotic vector suggested that the cDNA encodes a 62- to 66-kDa protein. Analysis of the nucleotide sequence of the cDNA insert revealed a 623-amino-acid-residue single open reading frame of 1,871 nucleotides, with an open 5' end. The predicted polypeptide is highly basic and contains a long stretch of highly hydrophobic residues localized to the carboxy terminus. The amino-terminal half of the predicted HHV-6 protein from the cDNA shows significant homology with the UL44 gene product of human cytomegalovirus, coding for the ICP36 family of early-late-class phosphoproteins. Two TATA boxes are located at nucleotide positions 668 and 722 of the cDNA. In vitro translation of RNA transcribed in vitro from the cDNA resulted in the synthesis of a 41-kDa polypeptide only. This polypeptide was readily immunoprecipitated by MAb 9A5D12, and its partial peptide map was identical to that of the 41-kDa polypeptide detected in infected cells. Together, these results indicate that the HHV-6 P41 is encoded within a gene coding for a larger protein.

Retroviral sequences related to human T-lymphotropic virus type II in patients with chronic fatigue immune dysfunction syndrome

Chronic fatigue immune dysfunction syndrome (CFIDS) is a recently recognized illness characterized by debilitating fatigue as well as immunological and neurological abnormalities [Straus, S.E. (1988) J. Inf. Dis. 157, 405-412]. Once thought to be caused by Epstein-Barr virus, it is now thought to have a different but unknown etiology. We evaluated 30 adult and pediatric CFIDS patients from six eastern states for the presence of human T-lymphotropic virus (HTLV) types I and II by Western immunoblotting, polymearse chain reaction, and in situ hybridization of blood samples. The majority of patients were positive for HTLV antibodies by Western blotting and for HTLV-II gag sequences by polymerase chain reaction and in situ hybridization. Twenty nonexposure healthy controls were negative in all assays. These data support an association between an HTLV-II-like virus and CFIDS.

Antibody reactivity with two strains of human herpesvirus-6 in Malaysians

A total of 234 sera from healthy Malaysians of diverse ethnic origins were tested for antibody to the Z29 and prototype GS strains of HHV-6. The prevalence in the races ranged from 58 to 80% for the GS strain and 49 to 76% for the Z29 strain. The highest prevalence was in Malays with semi-urban cultural lifestyles and lowest was in the indigenous rural tribes (Ibans, Kadazans, Bidayuhs, and Orang Asli). The antibody titres to GS and Z29 virus capsid antigens differed in 11 (4.7%) samples by more than 2 dilutions. In 9 of the 11 sera the titres to GS strain were higher than to the Z29 strain. The differences in the antibody titres between strains of HHV-6 may reflect subtle changes in antigen structure of the virus recognised by some individuals.

A comprehensive immunological analysis in chronic fatigue syndrome

A detailed analysis of cell-mediated and antibody-mediated immunity was performed in 20 CDC-defined patients with chronic fatigue syndrome (CFS) and 20 age- and sex-matched healthy controls. CD3+, CD4+, CD8+, and CD20+ lymphocytes were comparable in two groups. Natural killer cells as defined by CD16, CD56 and CD57 antigens were significantly reduced in CFS. A significant increase in the proportions of CD4+ ICAM 1+ T cells was observed in CFS. Monocytes from CFS displayed increased density (as determined by mean fluorescence channel numbers) of intercellular adhesion molecule 1 (ICAM-1) and lymphocyte function associated antigen 1 (LFA-1), but showed decreased enhancing response to recombinant interferon-gamma in vitro. The lymphocyte DNA synthesis in response to phytohaemoglobulin (PHA), Concanavalin A (Con A) and pokeweed mitogen (PWM) was normal but the response to soluble antigens was significantly reduced. Serum IgM, IgG, IgA, and IgG subclasses were normal. In vivo specific antibody response to pneumococcus vaccine was depressed in CFS. Forty percent of patients showed titres of anti-human herpes virus 6 (anti-HHV-6) antibody higher than that in the controls (greater than or equal to 1/80). These data suggest immunological dysfunction in patients with chronic fatigue syndrome. The significance of these observations is discussed.

Detection of HHV-6 by the polymerase chain reaction

The polymerase chain reaction (PCR) was used to detect human herpes virus 6 (HHV-6) sequences in tissue culture. A pair of primers was synthesized and used to amplify a conserved region of the genome. Amplified products were detected either by visualization of UV illuminated ethidium bromide stained gel or, by hybridization with a specific radiolabeled oligonucleotide. As little as 5 fg of HHV-6 could be detected in infected cells, making this assay suitable for diagnostic purposes.

Antigen(s)-specific tumour-infiltrating lymphocytes from tumour induced by human herpes virus-6 (HHV-6) DNA transfected NIH 3T3 transformants

Tumour infiltrating lymphocytes (TIL) have recently been shown to mediate potent therapeutic effects in certain malignancies in mice and in humans. To understand the mechanism of TIL immunotherapy it would be advantageous to generate tumour-specific TIL and to study a defined system of TIL and target cells in which the tumour epitope(s) recognized by TIL might be identified. We have established tumourigenic cell lines by transfection of NIH 3T3 cells with the entire genome of human herpesvirus-6 (HHV-6) and its small fragment (about 5% of the viral DNA sequence). Injection of these cells into nude mice produced tumours termed G-2T and 14-2T, respectively. Cell lines derived from these tumours when injected in NIH Swiss mice produced tumours, G-2TS and 14-2TS, respectively. We have generated TIL from G-2TS tumour that can kill G-2TS tumour cells in vitro but not other related tumours (14-2TS or MCA-106). These TIL can be expanded between 2-6.5 every 3-5 days. The TIL proliferated in tissue culture in response to recombinant interleukin-2 and interleukin-4 and maintained their tumor specificity for up to 6 months in vitro. Their phenotype was Thy 1.2+, Lyt-2+ and L3T4-. The availability of such tumour-specific stable TIL lines and specific viral-transformed targets will provide an opportunity to characterize the tumour-associated antigen critical for the specific cytotoxicity in this system and thereby to clarify the mechanism of this promising immunological approach to cancer therapy.

Hepatitis C virus seroprevalence in Italian haemophiliacs injected with virus-inactivated concentrates: five year follow-up and correlation with antibodies to other viruses

The overall prevalence of anti-HCV antibody in a group of 125 haemophiliacs was 62%. Four patients who had never received replacement therapy were anti-HCV negative. Of the 121 patients injected regularly with commercial concentrates, 76 were already anti-HCV seropositive in 1985 and remained so throughout the follow-up. Two patients seroconverted in 1987 without obvious signs or symptoms of hepatitis. Our patients were treated with dry heat-treated concentrates since 1985 and with wet heat- or solvent/detergent-treated concentrates since 1988. The absence of further seroconversions and of symptoms of acute post-transfusion non-A, non-B hepatitis since 1988 suggest that present virucidal treatments of concentrates are effective in preventing HCV transmission. Anti-HCV positivity appeared to be unrelated to the type and degree of haemophilia as well as to the presence of antibodies to hepatitis B virus, human immunodeficiency virus type 1, and human herpesvirus type 6.

Latent human herpesvirus-6 DNA is sparsely distributed in peripheral blood lymphocytes of healthy adults and patients with lymphocytic disorders

Human herpesvirus-6 (HHV-6) can be regularly isolated from peripheral blood mononuclear cells (PBMC) of children suffering from exanthema subitum, but only rarely from PBMC of adults. Although the high prevalence of HHV-6 infection in early childhood seems to result from cell-free infectious virus shedded in saliva of healthy adults, latent HHV-6 infection is supposed to occur in lymphocytes. Therefore, we performed polymerase chain reaction (PCR) with DNA from PBMC of 44 healthy adults, 31 HIV-seropositive individuals and 33 patients with leukaemia or lymphoproliferative disorders. As positive control served PBMC from 11 children with exanthema subitum and as negative control PBMC from 20 newborns. Whereas HHV-6-specific sequences were detected in PBMC from all children with exanthema subitum and never in PBMC from newborns, they were found in PBMC of 9% of healthy adults and HIV-seropositive individuals and in 16% of the patients with lymphoproliferative disorders. Apparently detection of HHV-6 DNA in PBMC was neither limited by low sensitivity of the HHV-6 PCR assay, which detected less than ten copies of cloned HHV-6 DNA, nor by a low rate of latently infected individuals, but was limited by the number of lymphocytes subjected to PCR. It is supposed that the presence of latent HHV-6 DNA in lymphocytes is common, but that infected lymphocytes are rare (less than or equal to 1 infected cell in 10(5) lymphocytes).(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibition of human herpesvirus 6 replication by 9-[4-hydroxy-2-(hydroxymethyl)butyl]guanine (2HM-HBG) and other antiviral compounds

The in vitro susceptibilities of human herpesvirus 6 to foscarnet; the guanosine analogs acyclovir, ganciclovir, and two isomers of 9-[4-hydroxy-2-(hydroxymethyl)butyl]guanine; and the thymidine analogs 3'-azido-3'-deoxythymidine and 1-beta-D-arabinofuranosyl-E-5-(2-bromovinyl)uracil were investigated. All compounds except 3'-azido-3'-deoxythymidine and 1-beta-D-arabinofuranosyl-E-5-(2-bromovinyl)uracil inhibited human herpesvirus 6 replication. The highest in vitro selectivity was obtained for 9-[4-hydroxy-2-(hydroxymethyl)butyl]guanine.

The Use of Antisera to the Human Herpesvirus 6 Major Capsid Protein to Determine the Effect of Antiviral Inhibitors on Virus Gene Expression

We have recently described the production of antisera which react with the human herpesvirus 6 (HHV-6) major capsid protein (MCP). We describe here the use of these specific antisera to characterize the kinetics of expression of the HHV-6 MCP and demonstrate that it is a late virus protein, expressed after DNA replication. We have used the expression of this protein as a measure of the efficacy of the antiviral nucleoside analogues 9-(2-hydroxyethoxymethyl)guanine (ACV) and 9-(1,3-dihydroxy-2-propoxymethyl)guanine (DHPG) upon HHV-6 replication and have determined 50% inhibitory concentrations to be 150 μm and 2 μm, respectively.

Characterization of a new strain of HHV-6 (HHV-6SF) recovered from the saliva of an HIV-infected individual

An isolate of the human herpesvirus-6 (HHV-6SF) recovered from the saliva of an HIV-infected individual differs in its cellular host range and certain genomic properties from other HHV-6 strains described. HHV-6SF replicates in adult peripheral blood mononuclear cells (PMC) substantially better than in fetal cord blood PMC and can be grown only in the MT-4 established T cell line. It preferentially infects CD4+ lymphocytes but can replicate in CD8+ cells and peripheral blood macrophages. It also infects neuroblastoma cells and cell lines derived from the gastrointestinal tract. These latter results suggest that this herpesvirus could play a role in disorders affecting these tissues. Finally, the restriction enzyme pattern of HHV-6SF differs from that of other HHV-6 strains. The identification of this distinct HHV-6 strain could indicate an unusual biologic variation among viral isolates thus far not observed with other herpesviruses.

An enzyme-linked immunosorbent assay for IgG antibodies to human herpes virus 6

An indirect enzyme-linked immunosorbent assay (ELISA) with human herpes virus 6 (HHV6) membrane antigen was compared with indirect immunofluorescence assay (IFA) for measurement of HHV6 IgG antibodies. Five hundred serum samples from 403 Swedish patients with suspected symptomatic Epstein-Barr virus (EBV) infections were examined. The specificity of the ELISA compared with IFA was 98.7% and the sensitivity was 98.4%. In 90% of the patients, IgG antibodies to HHV6 were detected with both assays. The highest HHV6 IgG titers were found mainly in patients with EBV or CMV infections, but HHV6 mononucleosis was not diagnosed. The same HHV6 antigen was assessed for IgM ELISA but was found to be of limited value due to high IgM reactivity with the control antigen. The HHV6 IgM ELISA requires further investigation. The IgG ELISA described is a reliable alternative to IFA for measurement of HHV6 IgG antibodies and for large scale epidemiological studies.

Identification of a nucleocapsid protein as a specific serological marker of human herpesvirus 6 infection

Enveloped whole virions and nucleocapsids of human herpesvirus 6 (HHV-6) strain Z29 were purified from supernatant fluids of infected human cord blood lymphocytes by filtration through polyvinylpyrrolidone-treated filters, banding on a Nycondenz step gradient, and centrifugation through two successive continuous sucrose gradients. More than 20 proteins ranging in molecular weight from less than 30,000 to more than 200,000 were identified in preparations of purified whole virions labeled with [35S]methionine and [35S]cysteine. Immunogenic virion proteins of HHV-6 were identified in immunoblot assays with human immune sera, immune sera generated from mice immunized with purified whole virions or purified nucleocapsids, and a monoclonal antibody generated from a mouse immunized with purified nucleocapsids. The sera and the monoclonal antibody reacted strongly with a 101-kilodalton protein in the immunoblots, suggesting that the protein is a component of the nucleocapsid. Human sera lacking HHV-6-specific antibodies and seropositive for one or more of the other human herpesviruses failed to react with this protein, indicating that it is a specific serologic marker for HHV-6 infection.