Samantha S. Soldan

Tissue Distribution and Variant Characterization of Human Herpesvirus (HHV)—6: Increased Prevalence of HHV-6A in Patients with Multiple Sclerosis

Human herpesvirus (HHV)-6 has been associated with the pathogenesis of multiple sclerosis (MS) on the basis of serologic, molecular, and histopathologic studies. This study sought to determine the distribution of HHV-6 in different MS body fluids, including serum, saliva, urine, and peripheral blood lymphocytes. The study results extend the observation of an increased frequency of HHV-6 DNA in serum of patients with MS to the unique detection of viral sequences in urine of a subset of patients with MS. Moreover, the HHV-6 identified in these cell-free compartments was predominantly the HHV-6A variant, which has been reported to be neurotropic. These results support the hypothesis that HHV-6 may contribute to the MS disease process.

Increased lymphoproliferative response to human herpesvirus type 6A variant in multiple sclerosis patients

Several reports have suggested an association of human herpevirus 6 (HHV‐6) and multiple sclerosis (MS) based on immunohistochemical demonstration of HHV‐6 DNA from sera and cerebrospinal fluid of MS patients but not in controls. Characterization of the cellular immune response of MS patients to HHV‐6 may further clarify the role of HHV‐6 in MS and provide insight into the pathogenesis of this immune‐mediated disease. We have compared lymphoproliferative responses to HHV‐6A (U1102)‐, and HHV‐7 (H7SB) ‐infected cell lysates in healthy controls and patients with MS. Most healthy controls (71%) proliferated to HHV‐6B lysate, and fewer (33%) responded to the HHV‐6A lysate. In contrast, 67% of MS patients had a lymphoproliferative response to HHV‐6A, which is a significant increase in comparison with healthy controls. A similar frequency of lymphoproliferative response (78%) to HHV‐6B was demonstrated in MS patients. These results indicate that the lymphoproliferative response to the HHV‐6A variant, which was recently reported to have greater neurotropism, is increased in MS patients. Ann Neurol 2000;47:306–313

High Frequency of Human Herpesvirus 6 DNA in Multiple Sclerosis Plaques Isolated by Laser Microdissection

The frequency of human herpesvirus 6 (HHV-6) DNA was assessed in autopsy material from multiple sclerosis (MS) plaques and normal-appearing white matter (NAWM) from brains of persons with MS, healthy brains, and brains of persons with other neurologic diseases. Specific areas from formalin-fixed, paraffin-embedded brain tissue samples were isolated by laser microscope. DNA was extracted from laser microdissected brain material, and HHV-6 genomic sequences were amplified by nested polymerase chain reaction. We analyzed 44 NAWM samples and 64 MS plaques from 13 patients with MS, 46 samples from 13 patients with non-MS neurologic disorders, and 41 samples from 12 healthy control brains. Of the 44 NAWM samples, 7 (15.9%) were positive for HHV-6 DNA sequences, versus 37 (57.8%) of 64 MS plaques (P<.0005). HHV-6 DNA was detected in 10 (21.7%) of 46 samples from patients with non-MS neurologic disorders and in 11 (26.8%) of 41 samples from patients without known neurologic disease. Although the frequency of HHV-6 DNA did not differ significantly by sample type, HHV-6 DNA was significantly more common in MS plaques, suggesting that HHV-6 may play a role in MS pathogenesis.

Increased detection of serum HHV-6 DNA sequences during multiple sclerosis (MS) exacerbations and correlation with parameters of MS disease progression

In recent years, human herpesvirus 6 (HHV-6) has been investigated as a possible causative agent for MS. To determine if the detection of HHV-6 DNA in the serum of MS patients correlates with clinical parameters of MS disease progression, a total of 215 serum samples was obtained from 59 MS patients followed prospectively for a 5-month period. These samples were analyzed for the presence of HHV-6 DNA by nested PCR and compared in parallel to MS disease activity. HHV-6 DNA was amplified in 22% (4/18) of samples obtained during a period of clinical exacerbation. Significantly fewer (P = 0.008) sera, 5.6% (11/197), obtained from MS patients during clinical remission tested positive for the presence of HHV-6 DNA. This work demonstrates that the detection of serum HHV-6 DNA is significantly correlated with clinical exacerbations in MS. Moreover, the findings presented in this study have confirmed previous reports supporting an association between MS and HHV-6 and suggest a role for this human herpesvirus in the pathogenesis of MS.

Elevated Serum and Cerebrospinal Fluid Levels of Soluble Human Herpesvirus Type 6 Cellular Receptor, Membrane Cofactor Protein, in Patients with Multiple Sclerosis

Membrane cofactor protein (CD46) is a member of a family of glycoproteins that are regulators of complement and prevent activation of complement on autologous cells. Recently, CD46 has been identified as the cellular receptor for human herpesvirus Type 6 (HHV‐6). Elevated levels of soluble CD46 have been described in several autoimmune disorders and may be implicated in the pathogenesis of these diseases. As several reports have supported an association of HHV‐6 and multiple sclerosis, it was of interest to compare levels of soluble CD46 in the sera of MS patients to that of healthy controls, other neurological disease controls, and other inflammatory disease controls. Using an immunoaffinity column comprised of immobilized monoclonal antibodies to CD46, serum levels of soluble CD46 were found to be significantly elevated in multiple sclerosis patients compared with healthy and other neurological disease controls. Moreover, multiple sclerosis patients who tested positive for HHV‐6 DNA in serum had significantly elevated levels of soluble CD46 in their serum compared with those who were negative for HHV‐6 DNA. A significant increase in soluble CD46 was also found in the serum of other inflammatory disease controls tested compared with healthy controls. Additionally, a significant correlation was demonstrated between levels of soluble CD46 in the serum and cerebrospinal fluid of multiple sclerosis patients. Collectively, these data suggest that elevated levels of soluble CD46 may contribute to the pathogenesis of inflammatory diseases, including MS.

Role of viruses in etiology and pathogenesis of multiple sclerosis.

Publisher Summary Multiple sclerosis (MS) is the most prevalent demyelinating disease of young adults, affecting an estimated 300,000 individuals in the United States alone. The majority of affected individuals have a relapsing–remitting course while a smaller subset has a more chronic–progressive presentation. Women are affected more often than men, a phenomenon associated with a number of auto-immune diseases. Although the etiology of MS is unknown, it is generally believed that genetic, immunologic, and environmental factors are involved. This chapter discusses these issues as they suggest that exogenous factors are associated with the pathogenesis of this disorder. Recently, the human herpes virus 6 (HHV-6) has received considerable attention as an infectious agent candidate that might be associated with the pathogenesis of MS. The chapter focuses on this agent and the data that support the role of this virus in MS disease pathogenesis. A model is proposed, whereby in genetically susceptible individuals, multiple viruses may trigger either a virus-specific or a cross-reactive auto-immune response that results in clinical MS. Epidemiologic evidence suggests that it is a multifactorial disease that develops as a result of host genetics, immune response, and environment.

Characterization and Sequencing of Prototypic Human T-Lymphotropic Virus Type 1 (HTLV-1) from an HTLV-1/2 Seroindeterminate Patient

ABSTRACT Serological screening for human T-lymphotropic virus type 1 (HTLV-1) parallels the standard screening process for human immunodeficiency virus (HIV), in which samples found positive by enzyme-linked immunosorbent assay (ELISA) are confirmed with a modified Western blot procedure. There are a significant number of cases in which HTLV-1/2 ELISA-positive specimens demonstrate an incomplete banding pattern on this Western blot. Individuals providing these atypical antibody responses are categorized as seroindeterminate for HTLV-1/2. Although HTLV-1 genomic sequences are readily detectable in the peripheral blood lymphocytes (PBL) of seropositive individuals, previous studies have repeatedly demonstrated that PBL from the vast majority of HTLV-1/2 seroindeterminate individuals are PCR negative for HTLV-1. As a result, identification of the agent responsible for this indeterminate reactivity has been of interest. We have generated an HTLV-1-positive B-cell line (SI-1 B) from one of these seroindeterminate individuals. Previous screening for HTLV-1 in PBL from this patient had been routinely negative by primary PCR; however, HTLV-1 tax had been periodically detected by nested PCR. DNA sequence data generated with genomic DNA from the SI-1 B cell line and HTLV-1-specific primers demonstrated the presence of a full-length viral genome with >97% homology to the Cosmopolitan form of HTLV-1. A 12-bp deletion was identified in the 3′-gag/5′-prot region, which would predict translation of altered or nonfunctional proteins from these genes. We propose that this HTLV-1/2-seroindeterminate patient is infected with a prototypic form of HTLV-1 at an extremely low viral load and that this finding may explain HTLV-1/2 seroindeterminate reactivity in at least a subset of these individuals.

Prediagnostic Human T Lymphotropic Virus Type I Provirus Loads Were Highest in Jamaican Children Who Developed Seborrheic Dermatitis and Severe Anemia

In a recent clinical analysis of 308 Jamaican children, human T lymphotropic virus type I (HTLV-I) infection was found to be associated with significantly higher incidence rates of seborrheic dermatitis, eczema, and persistent hyperreflexia of the lower limbs and with nonsignificantly increased rates of severe anemia and abnormal lymphocytes. Results of examination of HTLV-I viral markers in the 28 HTLV-I-infected children provided virologic support for the epidemiologic associations of HTLV-I with seborrheic dermatitis and severe anemia in childhood.

HTLV-I/II Seroindeterminate Western Blot Reactivity in a Cohort of Patients with Neurological Disease

The human T-cell lymphotropic virus type I (HTLV-I) is associated with a chronic, progressive neurological disease known as HTLV-I-associated myelopathy/tropical spastic paraparesis. Screening for HTLV-I involves the detection of virus-specific serum antibodies by EIA and confirmation by Western blot. HTLV-I/II seroindeterminate Western blot patterns have been described worldwide. However, the significance of this blot pattern is unclear. We identified 8 patients with neurological disease and an HTLV-I/II seroindeterminate Western blot pattern, none of whom demonstrated increased spontaneous proliferation and HTLV-I-specific cytotoxic T lymphocyte activity. However, HTLV-I tax sequence was amplified from the peripheral blood lymphocytes of 4 of them. These data suggest that patients with chronic progressive neurological disease and HTLV-I/II Western blot seroindeterminate reactivity may harbor either defective HTLV-I, novel retrovirus with partial homology to HTLV-I, or HTLV-I in low copy number.

Immune Response to HTLV-I and HTLV-II

Originally identified from a T-lymphoblastoid cell line (HUT 102) of a patient diagnosed with a cutaneous T-cell lymphoma, the human T-lymphotropic virus type I (HTLV-I) was the first described human retrovirus (1). In 1981, HTLV-I was established as the etiologic agent for adult T-cell leukemia (ATL) (2), a hematological malignancy first characterized in Japan (3). Since the initial description of ATL and the discovery of HTLV-I, the virus has been associated with an inflammatory, chronic, progressive neurologic disease known as HTLV-I associated myelopathy/tropical spastic paraparesis (HAM/TSP) in addition to several other inflammatory diseases (4–14). Although an increasing number of human diseases have been linked to HTLV-I the vast majority of HTLV-I—infected individuals remain clinically asymptomatic.