Lipid kinase activity of antibodies from milk of clinically healthy human mothers

MicroRNAs of Milk in Cells, Plasma, and Lipid Fractions of Human Milk, and Abzymes Catalyzing Their Hydrolysis

Human milk provides neonates with various components that ensure newborns’ growth, including protection from bacterial and viral infections. In neonates, the biological functions of many breast milk components can be very different compared with their functions in the body fluids of healthy adults. Catalytic antibodies (abzymes) that hydrolyze peptides, proteins, DNAs, RNAs, and oligosaccharides were detected, not only in the blood sera of autoimmune patients, but also in human milk. Non-coding microRNAs (18−25 nucleotides) are intra- and extracellular molecules of different human fluids. MiRNAs possess many different biological functions, including the regulation of several hundred genes. Five of them, miR-148a-3p, miR-200c-3p, miR-378a-3p, miR-146b-5p, and let-7f-5p, were previously found in milk in high concentrations. Here, we determined relative numbers of miRNA copies in 1 mg of analyzed cells, lipid fractions, and plasmas of human milk samples. The relative amount of microRNA decreases in the following order: cells ≈ lipid fraction > plasma. IgGs and sIgAs were isolated from milk plasma, and their activities in the hydrolysis of five microRNAs was compared. In general, sIgAs demonstrated higher miRNA-hydrolyzing activities than IgGs antibodies. The hydrolysis of five microRNAs by sIgAs and IgGs was site-specific. The relative activity of each microRNA hydrolysis was very dependent on the milk preparation. The correlation coefficients between the contents of five RNAs in milk plasma, and the relative activities of sIgAs compared to IgGs in hydrolyses, strongly depended on individual microRNA, and changed from −0.01 to 0.80. Thus, it was shown that milk contains specific antibodies (abzymes) that hydrolyze microRNAs specific for human milk.

Secretory immunoglobulin A from human milk hydrolyzes 5 histones and myelin basic protein

Mother's milk provides newborns with various nutrients (e.g., enzymes, proteins, peptides, hormones, antibodies) that help babies grow and protect them from bacterial and viral infections. The functions of many components of breast milk can be very different from their corresponding functions in body fluids of healthy adults. Catalytic antibodies (abzymes) that hydrolyze peptides, proteins, DNA, RNA, and oligosaccharides were detected not only in human milk, but also in the blood sera of autoimmune patients. However, abzymes with unexpected synthetic activities (lipids, oligosaccharides, and protein kinase activities) were revealed in milk that were not found in the blood of autoimmune patients. The nutrition of infants with fresh milk has a very specific role; newborns are well protected by antibodies of mother's milk (passive immunity). Protease abzymes were found in the blood sera of autoimmune patients, whereas healthy humans usually do not contain such autoantibodies. Here, we present the first evidence that the milk of healthy mothers contains secretory (s)IgA that effectively hydrolyze 5 histones (e.g., H1, H2A, H2B, H3, and H4) and myelin basic protein (MBP). Several rigid criteria were applied to show that protease activity is an intrinsic property of sIgA. Milk abzymes against 5 histones cannot hydrolyze different control proteins except histones and MBP, whereas autoantibodies against MBP split this protein and 5 histones. Antibodies against histones and MBP exhibit complexation polyreactivity as well as specific and unusual catalytic cross-reactivity. With some exceptions, the specific sites of hydrolysis of H1, H2A, and H2B by sIgA against histones do not coincide with the sites of hydrolysis by abzymes against MBP. On the whole, fresh human milk is a very specific source of many of the most unusual antibodies and abzymes.

Six catalytic activities and cytotoxicity of immunoglobulin G and secretory immunoglobulin A from human milk

In the milk of healthy women, antibodies were found with different catalytic activities (abzymes), which are absent in the sera of other healthy people. Moreover, it was previously shown that DNase antibodies-abzymes of patients with autoimmune diseases are cytotoxic to cancer cells. In this work, it was first shown that IgG and secretory IgA (sIgA) do not possess embryotoxicity; they practically do not affect the development of fertilized eggs of sea urchins but demonstrate sperm toxicity. After addition to the eggs of sperm preincubated with IgG and sIgA, the number of unfertilized eggs was increased, in the case of sIgA 1.6-fold higher than that for IgG. The suppression of the growth of MCF-7 breast cancer cells by sIgA was 2.2 times more effective than with IgG antibodies. The relative enzymatic activity of milk sIgA was higher than IgG (-fold): 1.9 (DNase), 4.6 (amylase), 1.7 (peroxidase), 1.3 (protease), 3.7 [hydrolysis of poly(C)], 3.3 [hydrolysis of poly(U)], and 1.7 (oxidation of 3,3'-diaminobenzidine). One of the possible reasons for the observed difference between sIgA and IgG could be that all 6 catalytic activities of sIgA were, on average, 2.6 times higher than that for IgG. Correlation coefficients between all the relative 6 enzymatic activities of IgG and sIgA and their toxicity to sea urchin sperm and to cancer cells were calculated. Maximum correlation coefficients were observed for DNase (+0.71), protease (+0.64) activities for sIgA, as well as protease (+0.59) and RNase (+0.77) of IgG with their toxicity toward sperm. The correlation coefficients were also high between peroxidase activity (+0.85) of sIgA and poly(U) hydrolysis by IgG (+0.58) with their suppression of tumor cell growth. It has been suggested that the catalytic activities of abzymes may be important in the manifestation of their sperm toxicity and inhibition of cancer cell growth.

Immunoglobulins with Non-Canonical Functions in Inflammatory and Autoimmune Disease States

Immunoglobulins are known to combine various effector mechanisms of the adaptive and the innate immune system. Classical immunoglobulin functions are associated with antigen recognition and the initiation of innate immune responses. However, in addition to classical functions, antibodies exhibit a variety of non-canonical functions related to the destruction of various pathogens due to catalytic activity and cofactor effects, the action of antibodies as agonists/antagonists of various receptors, the control of bacterial diversity of the intestine, etc. Canonical and non-canonical functions reflect the extreme human antibody repertoire and the variety of antibody types generated in the organism: antigen-specific, natural, polyreactive, broadly neutralizing, homophilic, bispecific and catalytic. The therapeutic effects of intravenous immunoglobulins (IVIg) are associated with both the canonical and non-canonical functions of antibodies. In this review, catalytic antibodies will be considered in more detail, since their formation is associated with inflammatory and autoimmune diseases. We will systematically summarize the diversity of catalytic antibodies in normal and pathological conditions. Translational perspectives of knowledge about natural antibodies for IVIg therapy will be also discussed.

Secretory immunoglobulin A from human milk hydrolyzes microRNA

For breast-fed infants, human milk is a source of various nutrients (e.g., proteins, peptides, antibodies) and bioactive components that promote neonatal growth and protect infants from viral and bacterial infection. Moreover, in terms of infant nutrition and protection the functions of many human milk components are very different from those of blood and other biological fluids of healthy adults. For example, catalytic antibodies ("abzymes") with synthetic activities (protein, oligosaccharide, and lipid kinase activities) have been found in human breast milk that are absent in the blood of healthy people. Abzymes with hydrolyzing functions have been detected not only in milk, but also in the blood of patients with autoimmune diseases. Obviously, feeding newborns human milk has a very specific role and it is a unique aspect of mammalian nutrition. Ribonuclease and DNase autoantibodies or abzymes are found in milk and blood of lactating women, but not in blood sera of healthy men and nonpregnant woman. Here, we present the first evidence that human milk secretory IgA molecules (sIgA) can effectively hydrolyze ribooligonucleotides containing 23 different bases [(pN)₂₃ ribooligonucleotides] and 4 microRNAs: miR-9-5p, miR-219-2-3p, miR-137, and miR-219a-5p. Ribonuclease activity is an inherent property of sIgAs. We showed that 7 individual sIgAs hydrolyzed the ribooligonucleotides (pA)₂₃, (pU)₂₃, and (pC)₂₃ nonspecifically and with comparable efficiency, whereas hydrolysis of the 4 microRNAs by sIgAs was site-specific. Sites of hydrolysis of 4 microRNAs by IgG from blood of patients with schizophrenia have been previously identified. The sites of hydrolysis of 4 microRNAs by sIgA-abzymes were very different from the previously identified sites of hydrolysis by IgG in patients with schizophrenia. In addition, in contrast to IgG, milk sIgAs efficiently hydrolyzed microRNAs in their loop and duplex regions.

IgGs from Human Milk Hydrolyze microRNAs

Mother’s milk provides breast-fed infants with various nutrients, including peptides, proteins, DNA, RNA, antibodies, and other bioactive components promoting neonatal growth and protecting infants from viral and bacterial infection. The functions of many human milk components regarding the nutrition and protection of newborns may be very different compared to those of various biological fluids of healthy adults. For example, human milk contains catalytic antibodies (abzymes) with protein, lipid, and oligosaccharide kinase activities, which are absent in the biological fluids of healthy people and autoimmune patients. Obviously, the nutrition of infants with fresh breast milk is a special phenomenon having a very specific and important role. Here, we have shown that mother’s milk IgGs effectively split homo-(pN)23, and four miRNAs: miR-137, miR-219a-5p, miR-219-2-3p, and miR-9-5p. It was shown that ribonuclease activity is a unique property of milk IgGs. On average, individual IgGs hydrolyze (pA)23, (pU)23, and (pC)23 nonspecifically and with comparable efficiency, whereas the hydrolysis of four miRNAs is predominately site-specific. The specific sites of the hydrolysis of four miRNAs by IgGs from the blood of schizophrenic (SCZ) patients and secretory immunoglobulins A (sIgAs) from human milk were found earlier. The sites of the hydrolysis of four miRNAs by milk IgGs and sIgA-abzymes are almost the same, but are significantly different in comparison with those for SCZ IgGs. In addition, in contrast to the SCZ IgGs, milk IgGs and sIgAs efficiently hydrolyzed miRNAs in the duplex regions formed by their terminal sequences.

Human milk sIgA molecules contain various combinations of different antigen-binding sites resulting in a multiple binding specificity of antibodies and enzymatic activities of abzymes

In the classic paradigm, immunoglobulins are monospecific molecules that have stable structures and two or more identical antigen-binding sites. However, we show here for the first time that the sIgA pool of human milk contains, depending on the donor, only 35±5% λ-sIgAs, 48±7% κ-sIgAs, and 17±4% of chimeric λ-κ-sIgAs. sIgA preparations contained no traces of canonical enzymes. However, all sIgA fractions eluted from several specific affinity sorbents under the conditions destroying even strong immune complexes demonstrated high catalytic activities in hydrolysis of ATP, DNA, and oligosaccharides, and phosphorylation of proteins, lipids, and oligosaccharides. Sequential re-chromatographies of the sIgA fractions with high affinity to one affinity sorbents on the second, third and then fourth affinity sorbents bearing other immobilized antigens led to the distribution of Abs and all catalytic activities all over the profiles of these chromatographies; in all cases some fractions eluted from affinity sorbents only under the conditions destroying strong immune complexes. In vitro, only an addition of reduced glutathione and milk plasma containing no Abs to two sIgA fractions with different affinity for DNA-cellulose led to a transition of up to 11–20% of Ab from one fraction to the other. Our data are indicative of the possibility of half-molecule exchange between different IgA and sIgA molecules. In addition, it cannot be excluded that during the penetration of IgAs through the specific milk barrier, the secretory component (S) and the join chain (J) can combine molecules of dimeric H₂L₂ λ-IgAs and κ-IgAs against different antigens forming many different variants of H₄L₄SJ sIgA molecules. Therefore, some chimeric molecules of sIgA can contain from two to four HL-fragments to various antigens interacting with high affinity with different sorbents and catalyzing various chemical reactions. Our data essentially expand the ideas concerning explanation of the phenomenon of polyspecificity and cross-reactivity of Abs.

Human milk IgGs contain various combinations of different antigen-binding sites resulting in multiple variants of their bispecificity

In the classic paradigm, immunoglobulins represent products of clonal B cell populations, each producing antibodies (Abs) recognizing a single antigen. There is a common belief that IgGs in mammalian biological fluids are monovalent molecules having stable structures and two identical antigen-binding sites. However, human milk IgGs to different antigens undergo extensive half-molecule exchange. In the IgGs pool, only 33±5% and 13±5% of Abs contained light chains exclusively of kappa- or lambda-type, respectively, while 54±10% of the IgGs contained both kappa- and lambda- light chains. All Ab preparations contained different amounts of IgGs of all four subclasses. Interestingly, lambda-IgGs contained an increased amount of IgG2 (87%) and only 3–6% of each of IgG1, IgG3, and IgG4, while kappa-IgGs consisted of comparable (17–32%) amounts of all IgG subtypes. Chimeric kappa-lambda-IgGs consisted of ∼74% IgG1, ∼16% IgG2, ∼5% IgG3 and ∼5% IgG4. As the result of the exchange, all IgG fractions eluted from several specific affinity sorbents under the conditions destroying strong immunocomplexes demonstrated high catalytic activities in hydrolysis of ATP, DNA, oligosaccharides, phosphorylation of proteins, lipids, and oligosaccharides. In vitro, an addition of reduced glutathione and milk plasma to two IgG fractions with different affinity for DNA-cellulose led to a transition of 25–60% of Ab of one fraction to the other fraction. Our data are indicative of the possibility of half-molecule exchange between milk IgGs of various subclasses, raised against different antigens (including abzymes), which explains the polyspecificity and cross-reactivity of these IgGs.

Metal dependent hydrolysis of β-casein by sIgA antibodies from human milk

We present the first evidence that electrophoretically and immunologically homogeneous sIgAs purified from milk of healthy human mothers by chromatography on Protein A-Sepharose and FPLC gel filtration contain intrinsically bound metal ions (Ca  >  Mg ≥ Al > Fe approximately  Zn ≥ Ni ≥ Cu ≥ Mn), the removal of which by a dialysis against ethylenediamine tetraacetic acid (EDTA) leads to a significant decrease in the β-casein-hydrolyzing activity of these antibodies (Abs). An affinity chromatography of total sIgAs on benzamidine-Sepharose interacting with canonical serine proteases separates a small metalloprotease sIgA fraction (6.8 ± 2.4%) from the main part of these Abs with a serine protease-like β-casein-hydrolyzing activity. The relative activity of this metalloprotease sIgA fraction containing intrinsically bound metal ions increases ∼1.2-1.9-fold after addition of external metal ions (Mg(2+) > Fe(2+) > Cu(2+) ≥ Ca(2+) ≥ Mn(2+)) but decreases by 85 ± 7% after the removal of the intrinsically bound metals. The metalloprotease sIgA fraction free of intrinsic metal ions demonstrates a high β-casein-hydrolyzing activity in the presence of individual external metal ions (Fe(2+) > Ca(2+) > Co(2+) ≥ Ni(2+)) and especially several combinations of metals: Co(2+) + Ca(2+) < Mg(2+) + Ca(2+) < Ca(2+) + Zn(2+) < Fe(2+) + Zn(2+) < Fe(2+) + Co(2+) < Fe(2+) + Ca(2+). The patterns of hydrolysis of a 22-mer oligopeptide corresponding to one of sIgA-dependent specific cleavage sites in β-casein depend significantly on the metal used. Metal-dependent sIgAs demonstrate an extreme diversity in their affinity for casein-Sepharose and chelating Sepharose, and interact with Sepharoses bearing immobilized monoclonal mouse IgGs against λ- and κ-type light chains of human Abs. Possible ways of the production of metalloprotease abzymes (Abz) by human immune system are discussed.

Peculiarities of abzymes from sera and milk of healthy donors and patients with autoimmune and viral diseases

The detection of catalytic activity of antibodies is the earliest indicator of development of autoimmune diseases (AID). In early stages of AID, the repertoire of abzymes with various properties is relatively small, but it is greatly increased during their development. Catalytic diversity of the abzymes includes DNase, RNase, ATPase, and oxidoreductase activities; there are antibodies phosphorylating proteins, lipids, and polysaccharides. This review summarizes new data on abzyme heterogeneity and possible reasons for this phenomenon. A possible role of abzymes and their exceptional multiplicity in the pathogenesis of different AID is discussed.

Nucleotide-hydrolyzing antibodies from the sera of autoimmune-prone MRL-lpr/lpr mice

Abzymes (Abzs) with different enzymic activities have been detected in the sera of patients with various autoimmune (AI) diseases and in AI mice. In this work, electrophoretically homogeneous IgGs were isolated from the sera of MRL-lpr/lpr mice spontaneously developing lupus-like AI pathology. It was shown for the first time that polyclonal IgGs (pIgGs) and their isolated heavy and light chains hydrolyze different nucleoside-5'-triphosphate (NTPs), nucleoside-5'-diphosphate (NDPs), adenosine monophosphate and deoxiadenosine-5'-monophosphate (dAMP), whereas antibodies from the sera of control healthy mice were catalytically inactive. Monoclonal mouse IgGs also effectively hydrolyze nucleotides. The data demonstrate that nucleotide-hydrolyzing activity is an intrinsic property of isolated mouse pIgG and monoclonal IgG. It was shown that various markers of AI pathologies (proteinuria and antibody titers to native and denatured DNA) demonstrating spontaneous development of AI reactions increased in animals with aging and correlated with an increase in Abz relative activity in hydrolysis of nucleotides. The highest increase in AI reaction markers and in Abz enzymic activity was found in mice immunized with a DNA-protein complex.

Cryptic natural autoantibodies and co-potentiators

Natural autoantibodies are normal components of the humoral arm of the immune system found in clinically healthy individuals. There are two subpopulations of natural antibodies, including an overt group of antibodies that are readily detected in unfractionated normal human sera. The other natural antibody subgroup is revealed by physico or biochemical treatment of normal human sera in vitro. Unmasking of this latter cryptic natural autoantibodies (cNA) may occur in vivo by local factors in the tissue environment of disease states. The masking cryptic factors may be immunoglobulin (Ig) or non-Ig in nature. These factors may either be co-inhibitors or co-enhancers of cNA. In the heat-potentiated binding of natural anti-phospholipid antibodies, apolipoprotein H (beta 2-glycoprotein I) appears to act as a co-enhancer. The immuno-relationship between the in vitro and in vivo cNA phenomenon remains to be elucidated.

Formation of different abzymes in autoimmune-prone MRL-lpr/lpr mice is associated with changes in colony formation of haematopoietic progenitors

It was shown that IgGs from the sera of 2–7-month-old control non-autoimmune (CBA x C57BL)F1 and BALB/c mice and 2–3-month-old autoimmune prone MRL-lpr/lpr mice (conditionally healthy mice) are catalytically inactive. During spontaneous development of deep systemic lupus erythematosus (SLE)-like pathology a specific reorganization of immune system of these mice leads to conditions associated with a production of IgGs hydrolyzing DNA, ATP and polysaccharides with low catalytic activities (conditionally pre-diseased mice).A significant increase in DNase, ATPase and amylase IgG relative activities associated with a transition from pre-diseased to deep diseased mice is correlated with additional changes in differentiation and proliferation of mice bone marrow haematopoietic stem cells (HSCs) and lymphocyte proliferation in different organs.The highest increase in all abzyme activities was found in mice immunized with DNA, which in comparison with pre-diseased and diseased mice are characterized by a different profile of HSC differentiation and by a suppression of cell apoptosis. Abzyme activities in the serum of pregnant females were comparable with those for pre-diseased mice, but the profile of HSC differentiation and cell apoptosis levels in pregnant and pre-diseased mice were quite different. Right after the beginning of lactation (4 days after delivery) and in a late time of lactation (14 days after delivery) there was an observed increase in cell apoptosis and two different stages of significant change in the HSC differentiation profiles; the first stage was accompanied with a significant increase and the second with a remarkable decrease in abzyme activities. Overall, all mouse groups investigated are characterized by a specific relationship between abzyme activities, HSC differentiation profiles, levels of lymphocyte proliferation, and cell apoptosis in different organs. From our point of view, the appearance of ATPase, DNase activities may be considered the earliest statistically significant marker of mouse spontaneous SLE and a further significant increase in their activities correlates with the appearance of SLE visible markers and with an increase in concentrations of anti-DNA Abs and urine protein. However, development of autoimmune (AI)-reactions and the increase in the sera anti-DNA antibodies (Abs) and in the abzyme activities in pregnant and lactating mice do not associate with SLE visible markers and proteinuria. The possible differences in immune system reorganizations during pre-disease, disease, pregnancy and lactation leading to production of different auto-antibodies and abzymes are discussed.

Polysaccharide kinase activity of human milk IgG antibodies

A small fraction of human milk IgG antibodies is shown to possess polysaccharide kinase activity for the first time. Unlike all known kinases, IgG antibodies can use as phosphate donor not only [gamma-(32)P]ATP, but also directly [(32)P]ortho-phosphate. Human milk IgGs therefore possess high affinity to ortho-phosphate (K(m) = 9-71 microM), which is a more effective substrate than ATP. IgG antibodies possessing polysaccharide kinase activity are yet another example of natural abzymes possessing not hydrolytic, but synthetic enzymatic activity.

Enzymes phosphorylating lipids and polysaccharides

Phosphorylation plays an important role in regulation of living functions of organisms; phosphorylation may significantly alter chemical properties of proteins, lipids, and carbohydrates. Canonical kinases catalyze transfer of terminal phosphate group from ATP (or other NTPs) to specific nucleophilic groups of proteins, lipids, and polysaccharides. Recently, unique kinases, catalytically active antibodies (abzymes) phosphorylating proteins, lipids, and polysaccharides have also been discovered. This review highlights biological functions and enzymatic characteristics of canonical kinases and abzymes phosphorylating lipids and polysaccharides.

Antibodies with amylase activity from the sera of autoimmune-prone MRL/MpJ-lpr mice

Animals spontaneously developing lupus-like autoimmune pathology (SLE) are very promising models to study the mechanisms of natural abzymes (Abzs) generation and their role in etiology and pathogenesis of autoimmune diseases, but Abzs from the sera of animals remain virtually unstudied. In this work, electrophoretically homogeneous IgGs were isolated from the sera of MRL/MpJ-lpr mice. It was shown for the first time that amylase activity is an intrinsic property of antibodies (Abs) and their isolated heavy and light chains. Various markers of SLE pathology (proteinuria, enhanced concentration of anti-DNA Abs) increased with spontaneous development of SLE and especially after animal immunization, correlating with the increase in Abz relative amylase activity. The highest amylase activity was found in the sera Abs of healthy mice after delivery and at the beginning of lactation; this was not correlated with markers of mouse SLE but supports the idea that pregnancy could "activate" or "trigger" autoimmune-like manifestations and Abzs production in healthy mammals. The possible differences in mechanisms of Abzs production in lactating mice and animals developing SLE are discussed.