HHV6 is unlikely to link to susceptibility to MS

van Nierop GP, Hintzen RQ, Verjans GM. Prevalence of human Herpesviridae in cerebrospinal fluid of patients with multiple sclerosis and noninfectious neurological disease in the Netherlands. J Neurovirol. 2014. [Epub ahead of print]

Prevalence of eight human herpesviruses (HHV1-8) was determined by real-time PCR in cell-rich cerebrospinal fluid (CSF) samples, obtained early after disease symptoms, of Dutch patients with multiple sclerosis (MS) and other noninfectious central nervous system diseases (NIND). Whereas HHV1-8 DNA was undetectable in CSF samples of MS patients, HHV6 DNA was detected in a plexus neuritis case and HHV7 DNA in an ependymoma and a Behçets' disease patient. However, intrathecal HHV infection was not detected. Data indicate that HHV1-8 are rarely detected in CSF of Dutch NIND patients and do not support the role of intrathecal HHV infection early after onset of disease symptoms in MS.
Some people think that HHV6 is a virus that causes MS (See below), however the data does not stack up. ProfG G says Bradford Hill... but maybe we should say enough's enough as this yet another study that cast serious doubt on any causal link between HHV-6 and MS. However not evey thing is black and white

Engdahl E, Gustafsson R, Ramanujam R, Sundqvist E, Olsson T, Hillert J, Alfredsson L, Kockum I, Fogdell-Hahn A. HLA-A∗02, gender and tobacco smoking, but not multiple sclerosis, affects the IgG antibody response against human herpesvirus 6. Hum Immunol. 2014 Mar. pii: S0198-8859(14)00109-8. doi: 0.1016/j.humimm.2014.03.001. [Epub ahead of print]

Multiple sclerosis (MS) is an inflammatory, demyelinating disease of the central nervous system. Both genetic and environmental factors contribute to disease susceptibility and two viruses associated with MS are human herpesvirus (HHV)-6A and HHV-6B, together referred to as HHV-6. This study characterized the plasma IgG antibody response against HHV-6 in MS patients (n=446) and healthy controls (n=487), and the relationship between MS susceptibility factors and the anti-HHV-6 response was investigated. In addition, 134 samples were further investigated for IgG against the early HHV-6 antigen p41. Antibody levels were measured with ELISA. The overall sero-prevalence against HHV-6 was 90%, with no significant difference in positivity or levels between MS patients and controls. Interestingly, carriership of HLA-A∗02 and tobacco smoking was associated with lower anti-HHV-6 IgG levels (p=0.0017 and p=0.026 respectively), whereas females sex was associated with higher levels (p=0.0090). No difference in IgG titers against p41 was observed between MS patients and controls. In conclusion, the IgG response against HHV-6 was associated with several factors that have previously been associated with MS susceptibility, possibly reflecting a relation between autoimmunity and how the immune system handles viral infections.

So in this study it suggests that the majority of MSers and controls have been exposed to HHV-6 and links reactivity f HHV-6 to the presence of HHV-6 risk factors

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