A comparative study of human endogenous retrovirus HERV-E λ 4-1 activation in autoimmune pathology

Considering the presence of immunomodulatory properties of human endogenous retroviruses, namely (i) the ability to activate the innate immune response by HERVs nucleic acids; (ii) the antigenicity of transcriptionally competent endogenous retroviruses envelope protein molecule, which causes polyclonal activation of lymphocytes; (iii) the absence of HERVs expression and protein production in the thymus during the immune tolerance formation, which allows us to consider these proteins as autoantigens or neoantigens, it seemed relevant to investigate the association of replication-competent human endogenous retrovirus HERV-E λ 4-1 with course of some of autoimmune diseases, such as multiple sclerosis, rheumatoid arthritis and systemic lupus erythematosus. The aim of this work was a comparative study of the human endogenous retrovirus HERV-E λ 4-1 activation frequency in blood mononuclear cells in multiple sclerosis, rheumatoid arthritis, systemic lupus erythematosus, as well as in chronic nervous system non-progressive diseases and the degenerative-dystrophic disease of the musculoskeletal system. The peripheral blood mononuclear cells were isolated by the venous blood centrifugation on Ficoll density gradient of 1.078 g/cm3. Expression of the HERV-E λ 4-1 envelope gene was detected by reverse transcriptase polymerase chain reaction. It was found that the HERV-E λ 4-1 envelope gene expression frequency in the chronic non-progressive diseases of nervous system, as well as in degenerative-dystrophic joint disease, is comparable to the expression frequency in conditionally healthy individuals. However, the HERV-E λ 4-1 envelope gene expression frequency in autoimmune diseases significantly exceeded that in conditionally healthy individuals and in non-inflammatory diseases. The maximum values of expression frequency were observed in active multiple sclerosis, significantly higher than in systemic lupus erythematosus and rheumatoid arthritis in the acute stage. Moreover, the expression frequency in the remission stage of multiple sclerosis was significantly lower than in the acute stage of the relapsing-remitted course, as well as in the progredient course. Estimation of HERV-E λ 4-1 envelope gene expression frequency at different severity levels of multiple sclerosis revealed its maximum rates at III and IV-V severity levels, both in relapsing-remitting and progressive course of multiple sclerosis. Thus, activation of the human endogenous retrovirus HERV-E λ 4-1 is associated with the course of autoimmune diseases, namely multiple sclerosis, rheumatoid arthritis, and systemic lupus erythematosus; it positively correlates with the activity and severity of multiple sclerosis.