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High Prevalence of Active Human Herpesvirus Six Variant A Infection in CNS and Lymphoid Tissue of Patients with MS

Konstance K. Knox, Ph.D. and Donald R. Carrigan, Ph.D.
Institute for Viral Pathogenesis, 10437 Innovation Drive, Milwaukee, Wisconsin 53226
Presented at the 125th Annual Meeting of the American Neurological Association
October 16, 2000
Boston, Massachusetts


Studies by our laboratory have documented that the majority of patients with MS have active HHV-6 infections in their CNS and lymphoid tissues. There are two distinct variants of HHV-6, HHV-6A and HHV-6B, that differ in their biologic and pathogenic properties. In these studies, we utilized variant specific monoclonal antibodies to detect the active HHV-6 infections. Of the 8 patients whose CNS tissues contained cells actively infected with HHV-6, 4 had infections with both HHV-6A and HHV-6B, 2 had only HHV-6A infected cells present, and 2 had only HHV-6B infected cells in their tissues. Three (50%) of the 6 patients with active infection of their lymphoid tissues were positive for both HHV-6A and HHV-6B. One patientís lymphoid tissue contained only HHV-6A, and two patientsí tissues contained only HHV-6B. These relatively high rates of HHV-6A infection in patients with MS, i.e. 75% and 67% in CNS and lymphoid tissues, respectively, stand in contrast to the low rates ( < 20%) of HHV-6A detection in normal individuals and immunocompromised patients. Thus, HHV-6A may play a special role in the pathogenesis of MS.


Patients and methods 

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Estimation of the Prevalence of HHV-6A infection in Adults


Prevalence of HHV-6A DNA in Specimens from Normal Controls and Various Patient Populations

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 Figure 1: The prevalence of HHV-6A DNA is significantly higher in normal adults compared to normal children.


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Figure 2: The prevalence of HHV-6A DNA is less than 30% in all patient groups and less than 20% in normal controls

Prevalence of Active HHV-6A infections in the CNS and Lymphoid Tissues of Patients with MS 

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Figure 3: 75% (6/8) of the MS patients studied had active HHV-6A infections within their CNS tissues  

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Figure 4: Of actively infected CNS tissue sections from these patients, 60% (12/20) of the active infections involved HHV-6A.

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†Figure 5: HHV-6 A infections were involved in 67% (4/6) of the lymphoid tissue infections present


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