Human cytomegalovirus pp65 peptide-induced autoantibodies cross-reacts with TAF9 protein and induces lupus-like autoimmunity in BALB/c mice

Human cytomegalovirus (HCMV) has been linked to the triggering of systemic lupus erythematosus (SLE). We proposed that B cell epitope region of HCMV phosphoprotein 65 (HCMVpp65)(422–439) mimics an endogenous antigen and initiates lupus-like autoimmunity. Amino acid homology between HCMVpp65(422-439) and TAF9(134-144) (TATA-box binding protein associated factor 9, TAF9) was investigated using a similarity search in NCBI protein BLAST program (BLASTP). A murine model was used to confirm their antigenicity and ability to induce lupus-like symptoms. HCMVpp65(422-439) induced immune responses with the presence of specific antibodies against HCMVpp65(422-439) and TAF9(134-144), as well as anti-nuclear and anti-double-stranded (ds)DNA antibodies that are characteristic of SLE. In addition, the majority of HCMVpp65(422-439) and TAF9(134-144) immunized mice developed proteinuria, and their renal pathology revealed glomerulonephritis with typical abnormalities, such as mesangial hypercellularity and immune complex deposition. Immunoglobulin eluted from the glomeruli of HCMVpp65(422-439) immunized mice showed cross-reactivity with TAF9(134-144) and dsDNA. Increased anti-TAF9 antibody activity was also observed in the sera from SLE patients compared with healthy people and disease controls. Molecular mimicry between HCMVpp65 peptide and host protein has the potential to drive lupus-like autoimmunity. This proof-of-concept study highlights the mechanisms underlying the link between HCMV infection and the induction of SLE.