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Antibodies hydrolyzing myelin basic protein (MBP) can play an important role in the pathogenesis of multiple sclerosis (MS) and systemic lupus erythematosus (SLE). An immunoglobulin light chain phagemid library derived from peripheral blood lymphocytes of patients with SLE was used. Small pools of phage particles displaying light chains with different affinities for MBP were isolated by affinity chromatography on MBP-Sepharose, and the fraction eluted with 0.5 M NaCl was used for preparation of individual monoclonal light chains (MLChs, 26–27 kDa). Seventy-two of 440 individual colonies were randomly chosen, expressed in Escherichia coli in a soluble form, and MLChs were purified by metal chelating chromatography. Twenty-two of 72 MLChs have high affinity and efficiently hydrolyze only MBP (not other control proteins) demonstrating various pH optima in a 5.7–9.0 range and different substrate specificity in the hydrolysis of four different MBP oligopeptides. Four MLChs demonstrated serine protease-like and three thiol protease-like activities, while 11 MLChs were metalloproteases. The activity of three MLChs was inhibited by both phenylmethylsulfonyl fluoride (PMSF) and Ethylenediaminetetraacetic acid (EDTA), two other by EDTA and iodoacetamide, and one by PMSF, EDTA, and iodoacetamide. The ratio of relative activity in the presence of Ca2+, Mg2+, Mn2+, Ni2+, Zn2+, Cu2+, and Co2+ was individual for each of 22 MLCh preparations. It is the first examples of human MLChs, which probably can possess two or even three different proteolytic activities. These observations suggest an extreme diversity of anti-MBP abzymes in SLE patients. The immune systems of individual SLE patients can generate a variety of anti-MBP abzymes, which can attack MBP of myelin-proteolipid sheath of axons and play an important role in MS and SLE pathogenesis. Copyright © 2015 John Wiley & Sons, Ltd.

Human immunodeficiency virus-infected patients possess anti-integrase (IN) catalytic IgGs and IgMs (abzymes), which, unlike canonical proteases, specifically hydrolyze only intact globular IN. Anti-myelin MBP abzymes from patients with multiple sclerosis and systemic lupus erythematosus efficiently hydrolyze only intact MBP. Anti-MBP and anti-IN abzymes do not hydrolyze several other tested control globular proteins. Here, we show that anti-IN abzymes efficiently hydrolyze a 21-mer oligopeptide (OP21) corresponding to one antigenic determinant (AGD) of MBP, whereas anti-MBP abzymes extremely poorly cleave oligopeptides corresponding to AGDs of IN. All sites of IgG-mediated and IgM-mediated proteolysis of OP21 by anti-IN abzymes were found for the first time by a combination of reverse phase and thin layer chromatography and mass spectrometry. Several clustered sites of OP21 cleavage were revealed and compared with the cleavage sites within the complete IN. Several fragments of OP21 had good homology with many fragments of the IN sequence. The active sites of anti-IN abzymes are known to be located on their light chains, whereas heavy chains are responsible for the affinity for protein substrates. Interactions of intact IN with both light and heavy chains of the abzymes provide high affinity for IN and the specificity of its hydrolysis. Our data suggest that OP21 interacts mainly with the light chains of polyclonal anti-IN abzymes, which possess lower affinity and specificity for substrate. The hydrolysis of the non-cognate OP21 oligopeptide may be also less specific than the hydrolysis of the globular IN because in contrast to previously described serine protease-like abzymes against different proteins, anti-IN abzymes possess serine, thiol, acidic, and metal-dependent protease activities.