Human C-reactive protein (CRP) is one of the so called acute phase proteins. Its concentration in blood increases rapidly as a response to inflammation. CRP is a 224 residue protein with a monomer molecular mass of approximately 25 kDa and pI 6.4 (1-4). It belongs to pentraxins, an evolutionally conserved family of proteins characterized by calcium dependent ligand binding and radial symmetry of five monomers forming a ring around central pore (5). The precise function of CRP in vivo is still not yet completely clear. CRP has been shown to participate in inflammatory as well as innate immunity processes. Important bioactivities of CRP are determined by its ability to bind to a variety of ligands, such as damaged cell membranes, apoptotic cells and fibronectin, with the highest affinity to phosphocholine residues. When CRP is ligand-bound, it can be recognized by the complement component C1q, which leads to activation of the classical complement pathway. On the other hand, via interaction with the complement factor H, CRP regulates the alternative complement pathway (6).
CRP in diagnostics
C-reactive protein is accepted in clinical use as a major, although rather non-specific, marker of inflammation. In generally healthy people, CRP levels are usually less than 5 mg/L. In pathology, CRP concentration has an enormous, 10,000-fold dynamic range (approximately 0.05–500 mg/L) (7). The highest levels of CRP (above 30 mg/L) are observed in bacterial infection, such as septic arthritis, meningitis and pneumonia.
In 2003, the Centers for Disease Control and Prevention (CDC) and the American Heart Association (AHA) issued a statement that identified CRP as the inflammatory marker best suited for use in current clinical practice to assess cardiovascular risk (8). Many epidemiologic studies have indicated that CRP is a strong independent predictor of future cardiovascular events, including myocardial infarction, ischemic stroke, peripheral vascular disease, and sudden cardiac death without known cardiovascular disease (as reviewed by Clearfield (9)). The CDC/ AHA guidelines support the use of CRP in primary prevention and set cutoff points according to relative risk categories: low risk (<1.0 mg/L), average risk (1.0-3.0 mg/L), and high risk (>3.0 mg/L). This is why present day high sensitivity CRP (hsCRP) assays are aimed at nanogram per milliliter (ng/ml) CRP level distinction.
Reagents for hsCRP assay development
HyTest’s monoclonal antibodies have been used in novel immunometric assays that achieve excellent sensitivity with linear detection range from 0.025 mg/L to 2.5 mg/L in a magnetic biosensor assay (10) and from 0.01 mg/L to 50 mg/L in an immunochemiluminometric assay (11). In both assays, the detection limit was 0.004 mg/L. A detection limit of 0.0011 mg/L was reached in a solid-phase sandwich fluorescence immunoassay using nanocrystals (12). Our best pairs C2-C6 and C5-CRP135 and several others provide 10,000-fold linearity in experimental immunofluorometric assays. Our antibodies could be used for the development of hsCRP assays for different diagnostic platforms. In addition to monoclonal antibodies, we also provide purified native CRP and CRP-free serum.
ApplicationsIn native CRP molecule each protomer has twocoordinated Ca2+ ions (13). HyTest offers anti-CRPMAbs which are either sensitive or insensitive tothe absence of Ca2+ in the solution. Some of ourantibodies recognize antigen only in the presenceof Ca2+ (MAbs C3, C4). The majority of HyTestMAbs do not depend on Ca2+ presence in sandwichimmunoassay and are able to efficiently recognizeantigen even in the presence of EDTA in the testedsample (MAbs C1, C2, C5, C6, C7, CRP11, CRP30,CRP36, CRP103, CRP135, CRP169).All HyTest anti-CRP MAbs were tested in differentimmunological applications.