Human herpesvirus-6 is a lymphotropic virus which infects susceptible individuals during the first year of life and usually causes life-long latency. In a variable percentage primary infections are followed by a short acute disease, exanthema subitum. Older individuals may suffer from infectious mononucleosis-like illnesses or from Kikuchi-Fujimoto's disease. In addition, there is a fairly wide spectrum of lymphoid and hematopoietic diseases or autoimmune disorders, which are associated with elevated titers of HHV-6 antibody, and from which replicating virus may be isolated. Such diseases include atypical polyclonal lymphoproliferation, Hodgkin's disease, chronic fatigue syndrome and systemic lupus erythematosus. The present article reviews the current knowledge of such associations.

Human herpesvirus 6 (HHV-6) is a potentially immunosuppressive agent that has been suggested to act as a cofactor in the progression of HIV disease. Exposure of human macrophages to HHV-6A or HHV-6B profoundly impaired their ability to produce interleukin 12 (IL-12) upon stimulation with interferon-gamma (IFN-gamma) and lipopolysaccharide (LPS).

By contrast, the production of tumor necrosis factor-alpha (TNF-alpha); regulated on activation, normal T-cell expressed and secreted (RANTES); and macrophage inflammatory protein 1beta (MIP-1beta) was not negatively affected. To exclude the involvement of IL-12-suppressive cytokines, such as IL-10 and TNF-alpha, the viral stocks were fractionated by ultra- centrifugation. The bulk of the suppressive activity was

recovered within the virion-rich pelleted fraction that was virtually devoid of such cytokines. IL-12 suppression was independent of viral replication, and the effect was not abrogated upon ultraviolet-light inactivation of the viral inoculum. The mechanism of HHV-6-mediated IL-12 suppression was investigated by RNase protection assays, which demonstrated unaltered levels of IL-12 p35 mRNA and only a modest reduction in p40 mRNA, which was insufficient to account for the near-complete loss of both extracellular and intracellular IL-12 protein. Moreover, both the IFN-gamma and the LPS signaling pathways were intact in HHV-6-treated cells. These data suggest that HHV-6 can dramatically affect the generation of effective cellular immune responses, providing a novel potential mechanism of HHV-6-mediated immunosuppression.

OBJECTIVE: Over the years, many viral agents have been suspected in the etiology of CFS. Recently, HHV-6, a beta herpesvirus, has been reported to be involved in the pathogenesis of CFS. We investigated the active infection of HHV-6 in CFS patients using (1) short-term culture of peripheral blood mononuclear cells (PBMCs), (2) IgM and IgG antibody evaluation in the plasma, and (3) nested PCR on plasma, cerebral spinal fluid (CSF), and PBMCs. We also characterized the HHV-6 isolates obtained as being Variant A or B. Seven CFS patients showing active HHV-6 infection were treated with three different antiherpesvirus compounds (Foscarnet, Ganciclovir, Valciclovir) to see if control of HHV-6 infection would alter the clinical manifestations.

MATERIALS AND METHODS: Specifically, we studied 24 CFS patients staged according to the severity of the disease. These patients came from Sierra Internal Medicine, Incline Village, NV, and the Medical Sciences Division, University of California at Irvine, Irvine, CA. The immunovirological assays used (i.e., IFA to detect HHV-6 antigen positive cells or to titer plasma for antibody) have previously been described (Ablashi et al., J Clin Virol 16:129, 2000). PBMCs from CFS patients were cultured (14 days) to detect HHV-6 infection using HHV-6 monoclonal antibodies. The modified nested PCR protocol used was based on the method described by Secchiero el al. (J Clin Microbiol 33:2124, 1997). HHV-6 specific primers against the major capsid protein were used. These primers generate a 258 bp fragment in the second stage PCR. DNA was isolated from PBMCs, plasma, and CSF samples using QIAgen columns.

RESULTS: 1. HHV-6 infection was detected in 14/24 (58.3%) of the CFS patients by the methods described. HHV-6 infection was detected in the PBMCs in short-term culture as early as three days, using IFA and HHV-6 early (p41) and late (gpl 16) monoclonal antibodies. The number of infected PBMCs varied from patient to patient. 2. IgM antibody to HHV-6 detected by IFA ranged from 1:20 to >1:160, and the IgG titer ranged from 1:80 to 1:1280. The presence of HHV-6 IgM antibody correlated well with the presence of HHV-6 in the PBMCs in 85% of the samples studied. 3. Nested PCR detected HHV-6 DNA in 15% of the plasmas and 25% of the CSF from the CFS patients. 4. Approximately 70% of the HHV-6 isolates from CFS patients were Variant A. 5. Out of the seven patients treated with antiviral compounds, the patient treated with Foscarnet clinically improved, and no HHV-6 infection was detectable. Of the four patients treated with Ganciclovir, only one showed slight clinical improvement. However, HHV-6 infection could be detected in the PBMCs of this patient. Of the two patients treated with Valciclovir, one improved clinically with no HHV-6 infection detectable. The second patient remained HHV-6 negative without any clinical improvement. CONCLUSION: 1. The data presented, although preliminary, show that the majority of CFS patients studied have HHV-6 infection. 2. It was surprising to find CFS patients exhibiting HHV-6 DNA in the CSF or plasma as well as in HCBMCs infected with CSF from these patients. These data suggest the presence of cell-free infectious virus in the CSF. In CFS, it is possible that HHV-6 is invading the central nervous system and may participate in the neurological manifestations associated with this disease. 3. Seventy percent of the HHV-6 isolates from CFS patients were classified as Variant A, which is more neuro-tropic. 4. Potent antiviral agents, such as Foscarnet and Valciclovir, are useful in suppressing HHV-6, thereby resulting in improved patient condition. However, longitudinal studies of more patients with CFS using newer antiviral agents which are less toxic are required to determine what specific role HHV-6 infection plays in the pathogenesis of this disease.

Multiple co-infections (Mycoplasma, Chlamydia, human herpes virus-6) in blood of chronic fatigue syndrome patients: association with signs and symptoms G. L. NICOLSON,1 R. GAN2 and J. HAIER3 1The Institute for Molecular Medicine, Huntington Beach, California, USA; 2International Molecular Diagnostics, Inc., Huntington Beach, California, USA, and 3Department of General Surgery, University Hospital, Muenster, Germany Nicolson GL, Gan R, Haier J.

Previously we and others found that a majority of chronic fatigue syndrome (CFS) patients showed evidence of systemic mycoplasmal infections, and their blood tested positive using a polymerase chain reaction assay for at least one of the four following Mycoplasma species: M. fermentans, M. hominis, M. pneumoniae or M. penetrans. Consistent with previous results, patients in the current study (n?) showed a high prevalence (overall 52%) of mycoplasmal infections. Using forensic polymerase chain reaction we also examined whether these same patients showed evidence of infections with Chlamydia pneumoniae (overall 7.5% positive) and/or active human herpes virus-6 (HHV-6, overall 30.5% positive).

Since the presence of one or more infections may predispose patients to other infections,we examined the prevalence of C. pneumoniae andHHV-6 active infections inmycoplasma-positive and -negative patients. Unexpectedly, we found that the incidence of C. pneumoniae or HHV-6 was similar in Mycoplasma-positive and -negative patients, and the converse was also found in active HHV-6-positive and -negative patients.

Control subjects (n?) had low rates of mycoplasmal (6%), active HHV-6 (9%) or chlamydial (1%) infections, and there were no co-infections in control subjects. Differences in bacterial and/or viral infections in CFS patients compared to control subjects were significant. Severity and incidence of patients’ signs and symptoms were compared within the above groups. Although there was a tendency for patients with multiple infections to have more severe signs and symptoms (p_0.01), the only significant differences found were in the incidence and severity of certain signs and symptoms in patients with multiple co-infections of any type compared to the other groups (p_0.01). There was no correlation between the type of co-infection and severity of signs and symptoms. The results indicate that a large subset of CFS patients show evidence of bacterial and/or viral infection(s), and these infections may contribute to the severity of signs and symptoms found in these patients.

CHRONIC FATIGUE SYNDROME LINKED TO HHV-6 VIRUS

Kutapressin inhibits in vitro infection of Human Herpesvirus Type 6. Ablashi DV, Berneman Z, Lawyer C, Komaroff A. Clinical Infectious Diseases 1994; 18(Supp 1): S113.

Abstract: The recently discovered human herpesvirus-6 (HHV-6) is being associated with an increasing number of conditions in which there is evidence of immunologic dysfunction. A number of widely available antiviral agents have shown little or no activity against the virus. We found that Ampligen, Poly(I)åPoly(C12U), a synthetic, mismatched, double-stranded RNA, has potent, previously unexpected antiviral effects. Cells known to allow replication of HHV-6 were infected with the virus and treated with Ampligen under various conditions. When cells were pretreated with Ampligen (concentrations of 100 or 200 micrograms/ml) prior to infection or treated shortly after infection, viral replication was inhibited by 46-98%. At 100 and 200 micrograms/ml, Ampligen also inhibited the DNA polymerase activity of HHV-6 by 42-98%. When lower concentrations of Ampligen (10 and 50 micrograms/ml) were used, only pretreatment of cells, with Ampligen, followed by virus infection and carrying the infected cells with Ampligen, significantly inhibited HHV-6 infection (83.7 and 89.1% respectively). Indirect evidence suggests that Ampligen may inhibit viral attachment to cellular receptors and/or inhibit intracellular maturation of the virus. The above concentrations of Ampligen were not toxic to the cells used in the study. Given these in vitro findings, and the low frequency of toxicity reported with the use of Ampligen, clinical trials of this drug in patients with evidence of reactivated HHV-6 infection would seem to be warranted.

Abstract: 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.

Abstract: OBJECTIVE: To conduct neurologic, immunologic, and virologic studies in patients with a chronic debilitating illness of acute onset. DESIGN: Cohort study with comparison to matched, healthy control subjects. PATIENTS: We studied 259 patients who sought care in one medical practice; 29% of the patients were regularly bedridden or shut-in. MAIN OUTCOME MEASURES: Detailed medical history, physical examination, conventional hematologic and chemistry testing, magnetic resonance imaging (MRI) studies, lymphocyte phenotyping studies, and assays for active infection of patients' lymphocytes with human herpesvirus type 6 (HHV-6). MAIN RESULTS: Patients had a higher mean (± SD) CD4/CD8 T-cell ratio than matched healthy controls (3.16 ± 1.5 compared with 2.3 ± 1.0, respectively; P less than 0.003). Magnetic resonance scans of the brain showed punctate, subcortical areas of high signal intensity consistent with edema or demyelination in 78% of patients (95% CI, 72% to 86%) and in 21% of controls (CI, 11% to 36%) (P less than 10(-9)). Primary cell culture of lymphocytes showed active replication of HHV-6 in 79 of 113 patients (70%; CI, 61% to 78%) and in 8 of 40 controls (20%; CI, 9% to 36%) (P less than 10(-8], a finding confirmed by assays using monoclonal antibodies specific for HHV-6 proteins and by polymerase chain reaction assays specific for HHV-6 DNA. CONCLUSIONS: Neurologic symptoms, MRI findings, and lymphocyte phenotyping studies suggest that the patients may have been experiencing a chronic, immunologically mediated inflammatory process of the central nervous system. The active replication of HHV-6 most likely represents reactivation of latent infection, perhaps due to immunologic dysfunction. Our study did not directly address whether HHV-6, a lymphotropic and gliotropic virus, plays a role in producing the symptoms or the immunologic and neurologic dysfunction seen in this illness. Whether the findings in our patients, who came from a relatively small geographic area, will be generalizable to other patients with a similar syndrome remains to be seen.

Abstract: A 17-year-old, previously healthy woman developed an acute "mononucleosis-like" illness with an associated "atypical" pneumonitis, followed by years of debilitating chronic fatigue, fevers, a 10-kg weight loss, night sweats, and neurocognitive symptoms. Thereafter, her sister developed a similar but less severe illness. The patient developed marked, chronic lymphadenopathy and splenomegaly, with associated persistent relative lymphocytosis and atypical lymphocytosis and with thrombocytopenia. After 3 years of illness, a splenectomy was performed, which resulted in some symptomatic improvement, prompt weight gain, and resolution of all hematologic abnormalities. Serial immunologic studies revealed a strikingly elevated number of activated B lymphocytes and a T lymphopenia, which improved but did not return to normal postsplenectomy. No causal association was found with any of several infectious agents that could produce such a lymphoproliferative illness. However, both the patient and her sister had evidence of active infection with the recently discovered human herpesvirus-6. Seven years after the onset of the illness, the patient and her sister remain chronically ill.

Abstract: 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).

Abstract: Human herpesvirus-6 is a lymphotropic virus which infects susceptible individuals during the first year of life and usually causes life-long latency. In a variable percentage primary infections are followed by a short acute disease, exanthema subitum. Older individuals may suffer from infectious mononucleosis-like illnesses or from Kikuchi-Fujimoto's disease. In addition, there is a fairly wide spectrum of lymphoid and hematopoietic diseases or autoimmune disorders, which are associated with elevated titers of HHV-6 antibody, and from which replicating virus may be isolated. Such diseases include atypical polyclonal lymphoproliferation, Hodgkin's disease, chronic fatigue syndrome and systemic lupus erythematosus. The present article reviews the current knowledge of such associations.

Abstract: An HHV-6 antigen capture assay measuring gp116/64/54 antigen was developed. This ELISA is specific for HHV-6 Variants A and B, does not cross react with other human herpesviruses, is sensitive, stable, quantitative, and can detect antigen in body fluids and cell cultures. Relative to virus isolation or techniques for measuring HHV-6 nucleic acids, the assay is much simpler and less expensive to perform. Plasmas/sera (413) obtained from healthy donors, children with Exanthem subitum, febrile illnesses, patients with Chronic Fatigue Syndrome, and AIDS patients tested by antigen capture assay demonstrated that the assay is useful in clinical laboratory settings. The capture assay can also be used to monitor cell cultures for virus isolation, production, quantitation, and antiviral agent screening.

Abstract: To evaluate the association between human herpesvirus 6 (HHV-6) and chronic fatigue syndrome (CFS), 2 geographically separate groups of CFS patients (125 and 29 patients, respectively) and healthy controls (150 and 15 controls, respectively) were compared, using an EIA, for antibodies to HHV-6 early antigen p41/38 (EA). Sixty percent (93/154) of CFS patients were were positive for HHV-6 EA IgM, 40% (61/154) were positive for IgG, and 23% (35/154) were positive for both. A total of 119 (77%) of the CFS patients were positive for HHV-6 EA IgG or IgM (or both); only 12% (20/165) of the controls had IgG or IgM to HHV-6 EA. These data demonstrate that more CFS patients than controls had elevated levels of HHV-6 EA-specific IgM, perhaps indicating active replication of HHV-6 in CFS.

Abstract: To test for an association between chronic fatigue syndrome (CFS) and infections with Epstein-Barr virus (EBV), human herpesvirus 6 (HHV-6) and human herpesvirus 7 (HHV-7), antibodies to these viruses were tested in the serum from three groups of individuals: (1) 10 CFS patients with chronic fatigue beginning with a clinical pattern of acute infectious mononucleosis [IM; true chronic IM (CIM)]; (2) 10 CFS patients whose illness did not start with acute IM (non-CIM), and (3) healthy controls. High EBV antibody titers were demonstrated in most patients. Antibodies to ZEBRA, a product of the immediate early EBV gene BZLF1, were detected in the serum of CFS patients at a higher frequency than in healthy controls. Antibody titers to HHV-6 and HHV-7 were also higher in the patients with CFS than in the controls. These results are consistent with the view that CFS patients may have reactivations of EBV, HHV-6 and HHV-7.

Abstract: A rapid (60-min) commercially available enzyme-linked immunosorbent assay (ELISA) for the detection of immunoglobulin G (IgG) class antibodies to human herpesvirus 6 (HHV-6) was evaluated. The specificity of the ELISA for HHV-6 was confirmed by absorption studies, with the reactivities of HHV-6-positive sera being unaffected by other herpesviruses (cytomegalovirus, herpes simplex virus, and varicella-zoster virus) or the HSB2 cell line used to culture HHV-6. HHV-6 IgG antibody levels in a panel of 502 serum samples were determined by ELISA and an indirect immunofluorescence assay (IFA). Results obtained by the two methods were in close agreement, suggesting that the ELISA provides a suitable test method for the determination of HHV-6 IgG antibodies in a routine clinical laboratory. Both tests were positive in 398 cases (79%), and both were negative in 71 cases (14%), with a different result obtained by IFA and ELISA in only 33 cases (7%). Furthermore, absorption of sera with HHV-6 prior to assay revealed that the majority of these results were false positive (n = 8) or false negative (n = 23) in the IFA (true positives or negatives in the ELISA). Subsequently, the ELISA showed a sensitivity of 99.76% and a specificity of 98.75%. HHV-6-specific IgG levels were also determined in paired serum samples collected from 49 donors-14 with exanthem subitum (ES), 15 with ES which was complicated with central nervous system involvement, and 20 undergoing bone marrow transplantation-in whom HHV-6 infection had been demonstrated by virus isolation and/or PCR. All patients with ES or central nervous system complications showed an increase in HHV-6-specific IgG, indicating that this ELISA may be a useful aid in the diagnosis of these conditions. Furthermore, 14 of 20 patients undergoing bone marrow transplantation showed an increase in HHV-6-specific IgG levels, possibly reflecting a reactivation of HHV-6 in these patients.

Abstract: Fifteen patients who fit the CDC definition of chronic fatgiue syndrome (CFS) and had evidence of severe reduction in performance levels by low Karnofsky performance scores (KPS) of 20 - 60 were treated with Ampligen. At baseline most patients showed evidence of cerebral dysfunction by neuropsychological testing, were antigen positive by cell culture assay for human herpesvirus-6 (HHV-6), and displayed reduced performance during exercise tolerance testing, as measured by oxygen consumption. These patients represented a subset of CFS patients with especially severe and sustained symptomatology. Following 12 - 48 weeks of Ampligen therapy, sustained improvements were noted in KPS (p< .01) Cognitive function improved including IQ and memory. Oxygen uptake and treadmill duration during exercise tolerance testing was also improved after 24 weeks of treatment (p < 0.01). Reduction in HHV-6 expression as measured by the giant cell assay was significant (p < 0.001). Patients continued to show significant improvement late in therapy, taking 8 to 12 weeks as baseline. It was concluded that while receiving Ampligen, the severely afflicted patients studied here derived long-lasting clinical benefit from the Ampligen therapy.

Abstract: Chronic fatigue syndrome (CFS) is a physically debilitating illness associated with immunologic abnormalities, viral reactivation, and impairment of cognition. In a randomized, multicenter, placebo-controlled, double-blind study of 92 patients meeting the CFS case definition of the Centers for Disease Control and Prevention, the response of several laboratory and clinical variables to an antiviral and immunomodulatory drug, poly(I)åpoly(C12U), was determined. Measures of clinical response included Karnofsky performance score, a cognition scale derived from a self-administered instrument assessing symptomatology (SCL-90-R), an activities of daily living scale, and exercise treadmill performance. After 24 weeks, patients receiving poly(I)åpoly(C12U) had higher scores for both global performance and perceived cognition than did patients receiving placebo. In particular, patients given Poly(I)åPoly(C12U) had increased Karnofsky performance scores (P < .03), exhibited a greater ability to do work during exercise treadmill testing (P=".01)," displayed an enhanced capacity to perform the activities of daily living (P < .04), had a reduced cognitive deficit (P=".05)," and required less use of other medications (P < .05).

Abstract: 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.

Abstract: Primary Human Herpesvirus-6 (HHV-6) infection has been related to different clinical pictures and notably, to Chronic Fatigue Syndrome (CFS). We studied 52 patients fulfilling the criteria of Centers for Disease Control (CDC) for CFS and a control group of 51 matched healthy blood donors. HHV-6 was recovered by culture and confirmed by immunofluorescence assay (IFA) and by PCR in 30/52 patients (57.7%) and in 6/51 (11.7%) of blood donors.