Multiple sclerosis and multiple sclerosis-associated retrovirus in Sardinia

The island of Sardinia has a high and increasing incidence of multiple scle rosis (MS). In a search for environmental factors that may account for this anomalously high incidence, we looked for evidence of multiple sclerosis-a ssociated retrovirus (MSRV) that has previously been found in the plasma an d cerebrospinal fluid of MS patients. We studied 25 MS patients and 25 matc hed healthy controls of ascertained Sardinian lineage. Blood samples were p rocessed for extracellular RNA extraction. RNAs underwent reverse transcrip tion/nested polymerase chain reaction (RT-PCR) with primers specific for MR SV-pol gene. We found a striking correlation between MSRV positivity and MS disease, but the virus was found also only in controls (100% and 12% respe ctively; Fisher's exact test, p <0.00001). It is unclear whether MSRV exert s any pathogenic role in MS. It is possible that this is simply an epipheno menon, but even then, it may constitute a diagnostic marker.