Interferon-Inducible Myxovirus Resistance Proteins: Potential Biomarkers for Differentiating Viral from Bacterial Infections.

Background: In 2015, the 68th World Health Assembly declared that effective, rapid, low-cost diagnostic tools were needed for guiding optimal use of antibiotics in medicine. This review is devoted to interferon-inducible myxovirus resistance proteins as potential biomarkers for differentiating viral from bacterial infections.

Content: After viral infection, a branch of the interferon (IFN)-induced molecular reactions is triggered by the binding of IFNs with their receptors, a process leading to the activation of and , which produce antiviral Mx proteins (MxA and MxB).

Binding of cholera toxin B subunit to intestinal epithelial cells.

We have prepared I-labeled cholera toxin B subunit (I-labeled CT-B, a specific activity of 98Ci/mmol) and found that it binds to rat IEC-6 and human Caco-2 intestinal epithelial cells with high affinity (K 3.6 and 3.7nM, respectively).

Human myeloma IgG4 reveals relatively rigid asymmetric Y-like structure with different conformational stability of C2 domains.

Human IgG4 (hIgG4) has weak pro-inflammatory activity. The structural basis for this is still unclear. Here a 3D model of myeloma hIgG4 was created at ∼3nm resolution using electron microscopy (EM) with negative staining and single-particle 3D reconstruction.

Interaction of Cholera Toxin B-subunit with Human T-lymphocytes.

In this work, I-labeled cholera toxin B-subunit (CT-B) (specific activity 98 Ci/mmol) was prepared, and its high-affinity binding to human blood T-lymphocytes (K = 3.3 nM) was determined. The binding of the I-labeled CT-B was inhibited by unlabeled interferon-α (IFN-α), thymosin-α (TM-α), and by the synthetic peptide LKEKK, which corresponds to sequences 16-20 of human TM-α and 131-135 of IFN-α (K 0.

Interaction of cholera toxin B subunit with T and B lymphocytes.

We have prepared I-labeled cholera toxin B subunit (I-labeled CT-B, a specific activity of 98Ci/mmol) and found that its binding to T and B lymphocytes from the blood of healthy donors was high-affinity (K 2.8 and 3.0nM, respectively).

Three-dimensional structure of the human myeloma IgG2.

Human immunoglobulin G, subclass 2 (hIgG2), plays an important role in immunity to bacterial pathogens and in numerous pathological conditions. However, there is a lack of information regarding the three-dimensional (3D) structure of the hIgG2 molecule. We used electron microscopy (EM), differential scanning microcalorimetry (DSC) and fluorescence for structural analysis of the hIgG2.

Adhesive organelles of Gram-negative pathogens assembled with the classical chaperone/usher machinery: structure and function from a clinical standpoint.

This review summarizes current knowledge on the structure, function, assembly and biomedical applications of the superfamily of adhesive fimbrial organelles exposed on the surface of Gram-negative pathogens with the classical chaperone/usher machinery. High-resolution three-dimensional (3D) structure studies of the minifibers assembling with the FGL (having a long F1-G1 loop) and FGS (having a short F1-G1 loop) chaperones show that they exploit the same principle of donor-strand complementation for polymerization of subunits. The 3D structure of adhesive subunits bound to host-cell receptors and the final architecture of adhesive fimbrial organelles reveal two functional families of the organelles, respectively, possessing polyadhesive and monoadhesive binding.

FGL chaperone-assembled fimbrial polyadhesins: anti-immune armament of Gram-negative bacterial pathogens.

This review summarizes the current knowledge on the structure, function, assembly, and biomedical applications of the family of adhesive fimbrial organelles assembled on the surface of Gram-negative pathogens via the FGL chaperone/usher pathway. Recent studies revealed the unique structural and functional properties of these organelles, distinguishing them from a related family, FGS chaperone-assembled adhesive pili. The FGL chaperone-assembled organelles consist of linear polymers of one or two types of protein subunits, each possessing one or two independent adhesive sites specific to different host cell receptors.

Resolving the energy paradox of chaperone/usher-mediated fibre assembly.

Periplasmic chaperone/usher machineries are used for assembly of filamentous adhesion organelles of Gram-negative pathogens in a process that has been suggested to be driven by folding energy. Structures of mutant chaperone-subunit complexes revealed a final folding transition (condensation of the subunit hydrophobic core) on the release of organelle subunit from the chaperone-subunit pre-assembly complex and incorporation into the final fibre structure. However, in view of the large interface between chaperone and subunit in the pre-assembly complex and the reported stability of this complex, it is difficult to understand how final folding could release sufficient energy to drive assembly.

Thermodynamic, conformational and functional properties of the human C1q globular heads in the intact C1q molecule in solution.

Thermodynamic. conformational and functional properties of the human C1q globular heads (hgC1q) were studied with the experimental approaches, which allow investigating these properties in the intact hC1q molecule in solution. Surprisingly, the scanning calorimetry data reveal a low level of cooperativity of interactions between the hgC1q A, B and C domains even at a neutral pH area.

Folding of the human immunoglobulin G3 Kus core hinge into the thirteenth globular domain.

Earlier, the electron microscopy and hydrodynamic studies revealed the transformation of the globule-like form of the human (h) IgG3 Kus hinge into a rod-like shape under non-denaturing perturbations [Eur. J. Biochem.

Core hinge of human immunoglobulin G3 as a system of four independent co-operative blocks.

On the heat absorption curves of human immunoglobulin G3 (hIgG3) Kuc melting the scanning calorimetry method reveals a high-temperature (high-T(m)) peak of high intensity that is absent at the curves of other hIgG subclasses and IgG of other species. An analogous peak is observed also at the curves of melting of hIgG3 fragments containing the hinge segments. The high-T(m) peak is accompanied by characteristic changes in circular dichroism (CD) spectra at 220-230 nm.

Synthetic peptide VKGFY and its cyclic analog stimulate macrophage bactericidal activity through non-opioid beta-endorphin receptors.

We synthesized linear and cyclic pentapeptides corresponding to the sequence 369-373 of human immunoglobulin G heavy chain--VKGFY (referred to as pentarphin and cyclopentarphin, respectively). The effect of pentarphin and cyclopentarphin on phagocytosis of Salmonella typhimurium virulent 415 strainbacteria by mouse peritoneal macrophages in vitro was studied. Control experiments showed that macrophages actively captured these bacteria, but did not digest them: the captured microbes were viable and continued to proliferate inside the phagocytes; within 12 h all macrophage monolayer was destroyed (incomplete phagocytosis).

Long-term metastable conformation of human Fcgamma subunit.

It was found that the human (hu) myeloma IgG1 Ser, its Fcgamma fragment and the chimeric mouse-human monoclonal antibody (chim-mAb), containing the constant part of hu-gamma1-chain, can exist in a long-term metastable conformational state. This state arises as a result of short incubation of IgG molecules and their Fcgamma fragments at pH<2.8 and the consequent rapid neutralisation to pH 7.

Donor strand complementation mechanism in the biogenesis of non-pilus systems.

The F1 antigen of Yersinia pestis belongs to a class of non-pilus adhesins assembled via a classical chaperone-usher pathway. Such pathways consist of PapD-like chaperones that bind subunits and pilot them to the outer membrane usher, where they are assembled into surface structures. In a recombinant Escherichia coli model system, chaperone-subunit (Caf1M:Caf1n) complexes accumulate in the periplasm.

Synthetic peptide SLTCLVKGFY competes with beta-endorphin for naloxone-insensitive binding sites on rat brain membranes.

The synthetic decapeptide Ser-Leu-Thr-Cys-Leu-Val-Lys-Gly-Phe-Tyr (termed immunorphin) corresponding to the sequence 364-373 of the CH3 domain of human immunoglobulin G heavy chain and its synthetic fragment VKGFY were found to compete with 125I-labeled beta-endorphin for high-affinity naloxone-insensitive binding sites on membranes isolated from the rat brain cortex (K(i)=1.18+/-0.09 and 1.

beta-Endorphin-like peptide SLTCLVKGFY is a selective agonist of nonopioid beta-endorphin receptor.

It has been found that beta-endorphin (beta-END) and a synthetic beta-END-like decapeptide Ser-Leu-Thr-Cys-Leu-Val-Lys-Gly-Phe-Tyr (termed immunorphin, IMN) corresponding to the sequence 364-373 of human IgG heavy chain stimulate Con A-induced proliferation of T lymphocytes from the blood of healthy donors. [Met(5)]enkephalin ([Met(5)]ENK) and an antagonist of opioid receptors naloxone (NAL) tested in parallel were not active. The stimulating effect of beta-END and IMN on T lymphocyte proliferation was not inhibited by NAL.

Synthetic beta-endorphin-like peptide immunorphin binds to non-opioid receptors for beta-endorphin on T lymphocytes.

The synthetic decapeptide H-SLTCLVKGFY-OH (termed immunorphin) corresponding to the sequence 364-373 of the CH3 domain of human immunoglobulin G heavy chain was found to compete with [125I]beta-endorphin for high-affinity receptors on T lymphocytes from the blood of healthy donors (K(i) = 0.6 nM). Besides immunorphin, its synthetic fragments H-Val-Lys-Gly-Phe-Tyr-OH (K(i) = 15 nM), H-Leu-Val-Lys-Gly-Phe-Tyr-OH (K(i) = 8.

Secretion of recombinant proteins via the chaperone/usher pathway in Escherichia coli.

F1 antigen (Caf1) of Yersinia pestis is assembled via the Caf1M chaperone/Caf1A usher pathway. We investigated the ability of this assembly system to facilitate secretion of full-length heterologous proteins fused to the Caf1 subunit in Escherichia coli. Despite correct processing of a chimeric protein composed of a modified Caf1 signal peptide, mature human interleukin-1beta (hIL-1beta), and mature Caf1, the processed product (hIL-1beta:Caf1) remained insoluble.

An extended hydrophobic interactive surface of Yersinia pestis Caf1M chaperone is essential for subunit binding and F1 capsule assembly.

A single polypeptide subunit, Caf1, polymerizes to form a dense, poorly defined structure (F1 capsule) on the surface of Yersinia pestis. The caf-encoded assembly components belong to the chaperone-usher protein family involved in the assembly of composite adhesive pili, but the Caf1M chaperone itself belongs to a distinct subfamily. One unique feature of this subfamily is the possession of a long, variable sequence between the F1 beta-strand and the G1 subunit binding beta-strand (FGL; F1 beta-strand to G1 beta-strand long).

Influence of synthetic peptide corresponding to the ACTH-like sequence of human immunoglobulin G1 on activity of murine thymocytes and peritoneal macrophages.

The purpose of the present study was to investigate properties and mechanism of action of the synthetic adrenocorticotropin (ACTH)-like peptide VKKPGSSVKV, corresponding to the sequence 11-20 of the variable part of human immunoglobulin G1 (IgG1) heavy chain. The ACTH-like peptide was shown to act as an immunosuppressive agent in vitro: it inhibits the blast transformation of mouse thymocytes and reduces the spontaneous motility of mouse peritoneal macrophages as well as their bactericidal activity against Salmonella typhimurium 415 virulent strain bacteria. High affinity receptors for the ACTH-like peptide were found on thymocytes and macrophages and shown to be at the same time the receptors for ACTH.

Influence of synthetic peptide corresponding to the ACTH-like sequence of human immunoglobulin G1 on proliferation of lymphoblastoid cells.

Influence of the ACTH-like peptide H-Val-Lys-Lys-Pro-Gly-Ser-Ser-Val-Lys-Val-OH corresponding to the sequence 11-20 of the variable part of human immunoglobulin G1 (IgG1) heavy chain on growth of MT-4 human T-lymphoblastoid cell line was investigated. It was found that the ACTH-like peptide at concentration range 10(-11) -10(-7) M inhibits the proliferation of MT-4 cells. Labeled ACTH 'address segment' [(125)I]ACTH (13-24) was used to establish that MT-4 cells express specific receptors for ACTH (K(d) = 97 pM).

Study of immunosuppressive activity of a synthetic decapeptide corresponding to an ACTH-like sequence of human immunoglobulin G1.

The synthetic ACTH-like decapeptide H-Val-Lys-Lys-Pro-Gly- Ser-Ser-Val-Lys-Val-OH, corresponding to amino acid residues 11-20 of the variable part of the human IgG1 heavy chain (referred to as immunocortin) was found to have an immunosuppressive effect on cells in vitro: it inhibits blast transformation of mouse thymocytes and reduces spontaneous motility of mouse peritoneal macrophages as well as their bactericidal activity against the virulent bacterial strain Salmonella typhimurium 415. Tritium-labeled immunocortin binds with high affinity to ACTH receptors on thymocytes and macrophages (Kd 2. 1 and 2.