Conclusions
Our data reveal that HERV-K proviruses are expressed in SLE and that the HERV-K-encoded Env protein elicits an immune response in patients, particularly during active disease.
Methods
ELISAs were conducted with recombinant Env protein and sera from SLE patients with active (n=60) or inactive (n=49) disease, healthy controls (n=47), other rheumatic disorders (n=59), as well as plasma from paediatric lupus patients with active (n=30) or inactive (n=30) disease, and 17 healthy children. Antibody reactivity was evaluated for correlations with clinical and laboratory parameters of the patients. Expression of HERV-K transcripts were profiled in SLE leukocytes by RNA-Seq.
Results
Both adult and paediatric SLE patients had autoantibodies against HERV-K Env with higher titres than healthy controls or patients with Sjögren's syndrome, small- or large-vessel vasculitis, or psoriatic arthritis. Transcripts from only two HERV-K loci capable of producing Env, HERV-K102 and -K108, were detected among the 10 expressed loci in SLE patients. Conclusions: Our data reveal that HERV-K proviruses are expressed in SLE and that the HERV-K-encoded Env protein elicits an immune response in patients, particularly during active disease.