Is this the black swan I have been looking for?
We need to be able to explain smouldering MS and why pwMS get worse despite having no evident disease activity (NEDA) on DMTs. One of the hypotheses is that something is occurring within the brains and spinal cords of pwMS. I have referred to this in the past as the field hypothesis and have suggested that it could be due to an active virus within the brains of pwMS. I have always made the point that the two viruses with most of the evidence behind them are EBV and HERVs, particularly HERV-W.
This study below strongly suggests that the HERV-W envelope protein may be driving smouldering MS. It would be interesting if the ENV protein is found in SELs (slowly expanding lesions). This study supports our Charcot Project and the urgent need to formally test HAART (highly active antiretroviral therapies) in MS. Our INSPIRE trial, which was negative, was not HAART as it only tested one anti-retroviral and integrase inhibitor.
Do you have the appetite for another push at getting funding for an add-on HAART trial in MS? The case for doing it is compelling both from an epidemiological and basic science perspective.
LET’S DO IT!
Kremer et al. pHERV-W envelope protein fuels microglial cell-dependent damage of myelinated axons in multiple sclerosis. Proc Natl Acad Sci U S A. 2019 Jun 18
Axonal degeneration is central to clinical disability and disease progression in multiple sclerosis (MS). Myeloid cells such as brain-resident microglia and blood-borne monocytes are thought to be critically involved in this degenerative process. However, the exact underlying mechanisms have still not been clarified. We have previously demonstrated that human endogenous retrovirus type W (HERV-W) negatively affects oligodendroglial precursor cell (OPC) differentiation and remyelination via its envelope protein pathogenic HERV-W (pHERV-W) ENV (formerly MS-associated retrovirus [MSRV]-ENV). In this current study, we investigated whether pHERV-W ENV also plays a role in axonal injury in MS. We found that in MS lesions, pHERV-W ENV is present in myeloid cells associated with axons. Focusing on progressive disease stages, we could then demonstrate that pHERV-W ENV induces a degenerative phenotype in microglial cells, driving them toward a close spatial association with myelinated axons. Moreover, in pHERV-W ENV-stimulated myelinated cocultures, microglia were found to structurally damage myelinated axons. Taken together, our data suggest that pHERV-W ENV-mediated microglial polarization contributes to neurodegeneration in MS. Thus, this analysis provides a neurobiological rationale for a recently completed clinical study in MS patients showing that antibody-mediated neutralization of pHERV-W ENV exerts neuroprotective effects.