Human herpes virus 6 and multiple sclerosis: a Finnish twin study

¹ Department of Neurology, University Hospital of Tampere, Tampere, Finland
² Department of Virology, University of Tampere, Medical School, Tampere, Finland
³ Department of Neurology, Hyvinkää Hospital, Hyvinkää, Finland

^* To whom correspondence should be addressed.

	Abstract

Objective To investigate the possible association of human herpes virus 6- (HHV6) infection and multiple sclerosis (MS).

Background Despite intensive investigations of genetic and environmental factors, the etiopathogenesis of MS remains unknown. HHV6 is a possible candidate in that it is neurotropic, able to induce demyelination and become latent and be reactivated. We had access to The Finnish National Twin Cohort, which provided a unique opportunity to study the association between HHV6 and MS in genetically homogenous patients.

Methods Thirty-four serum samples from 17 MS twin pairs and 12 cerebrospinal fluid (CSF) samples from six MS twin pairs were tested by PCR specific for HHV6. Immunogloubulin (Ig) G and M response against HHV6 in serum and CSF were analysed using ELISA method. The samples were collected during a remission of the disease.

Results No HHV6 DNA was found in any serum (n=34) or CSF (n=12) samples. Eighty-eight percent of the twins with MS and 86% of the healthy twin siblings were positive for IgG in serum. One twin with MS was also postitive for IgM in serum, whereas none of the healthy twins was IgM positive. All CSF samples were negative for IgG and IgM in both groups.

Conclusions During a clinical remission of MS the detection of antibodies against HHV6 in CSF and HHV6 DNA in serum, CSF supernatant or CSF leukocytes is unlikely. However, the results do not exclude a possibility of HHV6 reactivation during MS exacerbation or acute HHV6 infection being one of the triggering agents in development of MS long before its clinical manifestation.