Multiple sclerosis-associated retrovirus and related human endogenous retrovirus-W in patients with multiple sclerosis: A literature review

•HERV-W and related MSRV were reviewed in multiple sclerosis.•The debate on MSRV, endogenous or exogenous in nature?•HERV-W Env protein was also expressed in brain tissue from healthy subjects.•Absence of antibodies against MSRV Gag and Env proteins in multiple sclerosis•Reports do not support a causative role for MSRV or HERV-W in multiple sclerosis.

Human endogenous retrovirus-W and the closely related multiple sclerosis-associated retrovirus have been associated with neuro-inflammatory diseases including multiple sclerosis. However, retroviral expression has been reported in brain tissue from healthy subjects as well. In addition, no consensus has been reached on the endogenous/exogenous status of multiple sclerosis-associated retrovirus, which also needs clarification. Therefore, the purpose of this study was to systematically review the published data available on the viruses investigated in patients with multiple sclerosis and to evaluate their hypothesized role as contributing factors to the disease etiology. Evidence suggests that both retroviruses may be endogenous to humans and that failure to suppress viral activity may not be restricted to patients with multiple sclerosis and therefore an unlikely cause of the disease.