Specific cross-reaction of anti-dsDNA antibody with platelet integrin GPIIIa49-66

Abstract

Anti-platelet autoantibodies are frequently found in systemic lupus erythematosus (SLE) patients and contribute to the development of SLE-associated immunologic thrombocytopenia (SLE-ITP). Although the correlation of anti-dsDNA autoantibody with platelet-associated antibody has been reported, the potential mechanism underlying such a correlation is incompletely understood. We have reported that anti-platelet integrin GPIIIa49-66 (CAPESIEFPVSEARVLED) autoantibodies play a major role in the development of HIV-1-related thrombocytopenia (HIV-1-ITP). The strong negative charge of GPIIIa49-66 prompts us to investigate whether GPIIIa49-66 can be an epitope mimicking dsDNA. We report here that anti-GPIIIa49-66 antibodies are found in three out of nine SLE-ITP patients. Double-stranded (ds) DNA competitively inhibited the binding of purified patient anti-dsDNA antibodies to GPIIIa49-66 peptide. Both polyclonal and monoclonal anti-GPIIIa49-66 antibodies are able to cross-react with dsDNA. Consistent with previous reports, the DNA binding activities of anti-GPIIIa49-66 antibodies are mainly dependent on the positively charged amino acid in the heavy-chain complementarity-determining region 3 (HCDR3). The HCDR3 of human SLE anti-dsDNA monoclonal antibody (mAb) 412.67 demonstrates a similar positively charged amino acid chain orientation compared with that of anti-GPIIIa49-66 mAb A11, and it cross-reacts with GPIIIa49-66 peptide. Purified anti-GPIIIa49-66 antibodies from SLE-ITP patients are able to induce platelet fragmentation in vitro and to induce thrombocytopenia in vivo. Thus, our data suggest that specific epitope cross-reaction between GPIIIa49-66 and dsDNA could be a mechanism involved in the development of SLE-associated thrombocytopenia.

HOT or not: examining the basis of high-occupancy target regions

“…Such displacement causes R-loop prone regions to contain multiple polynucleotide structures: double stranded DNA, single stranded DNA, RNA:DNA hybrids, single stranded RNA (reviewed in [16]), G quadruplex complexes [30,31], etc., all of which can be bound by antibodies with a range of affinities [30,[32][33][34][35]. Anti-DNA antibodies are abundant in the serum of normal animals immunized with protein fragments [36][37][38][39][40][41][42][43][44][45], and are frequently polyspecific [40,[46][47][48][49][50][51][52][53][54] -they can bind both polynucleotide and non-polynucleotide (e.g. peptide, phospholipid) epitopes [35].…”

A humanized single-chain antibody against beta 3 integrin inhibits pulmonary metastasis by preferentially fragmenting activated platelets in the tumor microenvironment

“…We have previously described a unique antiplatelet autoantibody in patients with HIV-or hepatitis C-related thrombocytopenia that recognizes the sequence GPIIIa49-66 and induces complement-independent platelet lysis by generation of reactive oxygen species and peroxide after platelet-reduced nicotinamide adenine dinucleotide phosphate oxidase activation. [18][19][20][21][22] By screening a human single-chain fragment variable region (scFv) library with the GPIIIa49-66 peptide as bait, we identified a human monoclonal scFv Ab that recognized GPIIIa49-66 (named A11), with similar functional properties to the patient autoantibody in that it preferentially binds to activated platelets and can also lyse platelet thrombus in vitro. [23][24][25] We therefore sought to determine whether A11 would be associated with any significant antimetastatic effect by clearance of functional, activated platelets in the tumor environment.…”

Systemic Lupus Erythematosus: Definitions, Contexts, Conflicts, Enigmas

“…Molecular mimicry is an alternative approach to study origin and impact of anti-dsDNA antibodies. For example, several distinct anti-dsDNA antibodies cross-react with non-nucleic acid structures like, e.g., phospholipids ( 164 , 165 ), α-actinin ( 166 – 168 ), peptides like DWEYSVWLSN ( 169 ), entactin ( 113 ), the platelet integrin GPIIIa49-66 ( 170 ), and others. Which of the cross-reacting structures are initiating this dual immune response in vivo is not known.…”