Retroviral RNA related to ERV9/MSRV in a human serum: a new sequence variant

Association of human endogenous retroviruses with multiple sclerosis and possible interactions with herpes viruses

The hypothesis that human endogenous retroviruses (HERVs) play a role in autoimmune diseases is subject to increasing attention. HERVs represent both putative susceptibility genes and putative pathogenic viruses in the immune-mediated neurological disease multiple sclerosis (MS). Gammaretroviral HERV sequences are found in reverse transcriptase-positive virions produced by cultured mononuclear cells from MS patients, and they have been isolated from MS samples of plasma, serum and CSF, and characterised to some extent at the nucleotide, protein/enzyme, virion and immunogenic level. Two types of sequences, HERV-H and HERV-W, have been reported. No known HERV-H or HERV-W copy contains complete ORFs in all prerequisite genes, although several copies have coding potential, and several such sequences are specifically activated in MS, apparently resulting in the production of complete, competent virions. Increased antibody reactivity to specific Gammaretroviral HERV epitopes is found in MS serum and CSF, and cell-mediated immune responses have also been reported. Further, HERV-encoded proteins can have neuropathogenic effects. The activating factor(s) in the process resulting in protein or virion production may be members of the Herpesviridae. Several herpes viruses, such as HSV-1, VZV, EBV and HHV-6, have been associated with MS pathogenesis, and retroviruses and herpes viruses have complex interactions. The current understanding of HERVs, and specifically the investigations of HERV activation and expression in MS are the major subjects of this review, which also proposes to synergise the herpes and HERV findings, and presents several possible pathogenic mechanisms for HERVs in MS.

Multiple sclerosis retrovirus particles and recombinant envelope trigger an abnormal immune response in vitro, by inducing polyclonal Vbeta16 T-lymphocyte activation

A retroviral element (MSRV) defining a family of genetically inherited endogenous retroviruses (HERV-W) has recently been characterized in cell cultures from patients with multiple sclerosis (MS). To address the possible relationship with MS, direct detection of circulating virion RNA was proposed but revealed technically difficult to perform in standardized conditions, in the face of multiple endogenous HERV-W copies. A parallel approach has evaluated MSRV potential pathogenicity in relation to characteristic features of multiple sclerosis, in particular, T-lymphocyte-mediated immunopathology. We report here that MSRV particles induce T-lymphocyte response with a bias in the Vbeta16 chain usage in surface receptor, whatever the HLA DR of the donor. A recombinant MSRV envelope-but not core-protein reproduced similar nonconventional activation. Molecular analysis of Vbeta CDR3 showed that Vbeta16 expansions are polyclonal. Our results thus provide evidence that MSRV envelope protein can trigger an abnormal immune response with similar characteristics to that of superantigens.

Infrequency of detection of particle-associated MSRV/HERV-W RNA in the synovial fluid of patients with rheumatoid arthritis

OBJECTIVES

To determine whether the recently identified multiple sclerosis-associated retrovirus, MSRV, is detectable in the serum and synovial fluid of patients with rheumatoid arthritis (RA).

METHODS

A reverse transcription-polymerase chain reaction (RT-PCR) assay was used to seek evidence of particle-associated MSRV/HERV-W RNA in the plasma and synovial fluid of patients with RA and controls. Stringent precautions were taken to avoid detection of contaminating human genomic DNA and cellular RNA sequences.

RESULTS

Thirty-seven plasma samples were tested (20 from RA patients and 17 from controls) but none had detectable MSRV/HERV-W RNA. Synovial fluid samples were available from nine patients with RA and 10 controls. Particle-associated MSRV/HERV-W RNA was reproducibly detected in two of nine synovial fluid samples from RA patients and in one control sample. The identity of RT-PCR products was confirmed by sequencing.

CONCLUSION

MSRV/HERV-W RNA sequences are detectable in the synovial fluid of a small proportion of RA patients, but this phenomenon may not be specific to RA.