Modulation of protein A formation in Staphylococcus aureus by genetic determinants for methicillin resistance

Reversible Immuno-Infrared Sensor for the Detection of Alzheimer's Disease Related Biomarkers

The development of biosensors for medical purposes is a growing field. An immuno-infrared biosensor for the preclinical detection of Alzheimer's disease (AD) in body fluids was developed. The key element of this sensor is an ATR crystal with chemically modified surface to catch the biomarker out of the body fluid. So far, the immuno-infrared sensor can be used only once and requires time-consuming steps of sensor exchange, sensor cleaning, and novel surface functionalization. Here, we developed an immuno-infrared sensor providing a reusable surface and showcase its performance by the detection of the AD biomarker proteins Aβ and Tau in human cerebrospinal fluid (CSF). The sensor surface is covalently coated with the immunoglobulin binding proteins Protein A or Protein G. These were employed for noncovalent immobilization of antibodies and the subsequent immobilization and analysis of their antigens. The reversible antibody immobilization can be repeated several times with the same or different antibodies. Further, the more specific binding of the antibody via its Fc region instead of the conventional NHS coupling leads to a 3-4-fold higher antigen binding capacity of the antibody. Thus, the throughput, sensitivity, and automation capacity of the immuno-infrared biosensor are significantly increased as compared to former immuno-infrared assays. This immuno-sensor can be used with any antibody that binds to Protein A or Protein G.

xMAP-based analysis of three most prevalent staphylococcal toxins in Staphylococcus aureus cultures

Detection of staphylococcal toxins presents a great interest for medical diagnostics. Screening of clinical samples for the presence of several types of staphylococcal toxins using traditional methods-biological tests on animals or cell cultures as well as ELISA-is laborious. Multiplex detection methods would simplify testing. We have designed an xMAP-based assay to detect three staphylococcal toxins-enterotoxins A and B (SEA and SEB) and toxic shock syndrome toxin (TSST)-in cultural supernatants obtained from different strains of Staphylococcus aureus. The limits of detection of SEA, SEB, and TSST multiplex detection in S. aureus growth medium were 10, 1,000, and 5 pg/mL, respectively. Fifty-nine samples of S. aureus cultural supernatants were tested with the xMAP assay. The developed assay has proved highly effective detection of the natural toxins in the samples obtained due to bacterial cells cultivation. In prospect, the developed test system can be used in clinical diagnostics and in monitoring of foodstuffs and environmental objects.

A comparative structural and bioanalytical study of IVIG clinical lots

Intravenous immunoglobulin are important bio-therapeutics used in the replacement therapy for primary and secondary immunodeficiencies, chronic inflammatory disorders and several autoimmune haematologic disorders. Currently, a number of immunoglobulin intravenous (IVIG) products have been approved by the Food and Drug Administration (FDA) and are available commercially. It is known that small differences in the manufacturing processes as well as in the formulations may affect their clinical efficacy and tolerability. Therefore, given the complexity of the multi-step process required for the isolation of IVIG from human plasma, it is necessary to ensure a rigorous quality control of final products. We show here that a set of different bioanalytical techniques can be conveniently used to comparatively characterize, at a quantitative and qualitative level, different lots of IVIG preparations and to unveil randomly occurring impurities which can also affect the overall product stability. We have used circular dichroism, surface plasmon resonance and two-dimensional electrophoresis (2DE), and have demonstrated that this combination of bioanalytical approaches is very useful to improve the quality control of antibodies and to monitor the reliability of the IVIG manufacturing process.

IgG-binding proteins of bacteria

Proteins capable of non-immune binding of immunoglobulins G (IgG) of various mammalian species, i.e. without the involvement of the antigen-binding sites of the immunoglobulins, are widespread in bacteria. These proteins are located on the surface of bacterial cells and help them to evade the host's immune response due to protection against the action of complement and to decrease in phagocytosis. This review summarizes data on the structure of immunoglobulin-binding proteins (IBP) and their complexes with IgG. Common and distinctive structural features of IBPs of gram-positive bacteria (staphylococci, streptococci, peptostreptococci) are discussed. Conditions for IBP expression by bacteria and their functional heterogeneity are considered. Data on IBPs of gram-negative bacteria are presented.

Antimicrobial resistance of Staphylococcus aureus: genetic basis

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