Isolation and characterization of monoclonal antibodies monospecific for bovine alpha-casein and beta-casein

A simple competitive enzyme-linked immunosorbent assay for the specific detection of the multiphosphorylated 1–25 β-casein fragment

A specific and simple competitive enzyme-linked immunosorbent assay (ELISA) was developed to determine bovine β-casein phosphopeptides (β-CPP) in casein phosphopeptides (CPP) or CPP complexes such as casein phosphopeptide amorphous calcium phosphate complexes added into dairy products. The method combines sample pretreatment designed for CPP enrichment and anti-β-CPP(f(1–25)) monoclonal antibody 1A5 (mAb 1A5). The mAb 1A5 bound specifically to the tryptic phosphopeptides from β-casein but not from αs1- or αs2-casein. Reactivity was also influenced by the extent of the phosphorylated form of serine residues. Based on the sequence-specific recognition and contribution of phosphorylated serine residues, the epitope of mAb 1A5 was found to reside within the cluster motif Ser(P)-Ser(P)-Ser(P)-Glu-Glu and the surrounding residues in β-CPP. The competitive ELISA developed here can be used as an alternative to specialised and expensive techniques such as mass spectrometry. In particular, it is suitable for the measurement of CPP or CPP complexes in dairy products, which contain closely related endogenous molecular species.

Authenticity Assessment of Dairy Products

The authenticity of dairy products has become a focal point, attracting the attention of scientists, producers, consumers, and policymakers. Among many others, some of the practices not allowed in milk and milk products are the substitution of part of the fat or proteins, admixtures of milk of different species, additions of low-cost dairy products (mainly whey derivatives), or mislabeling of products protected by denomination of origin. A range of analytical methods to detect frauds have been developed, modified, and continually reassessed to be one step ahead of manufacturers who pursue these illegal activities. Traditional procedures to assess the authenticity of dairy products include chromatographic, electrophoretic, and immunoenzymatic methods. New approaches such as capillary electrophoresis, polymerase chain reaction, and isotope ratio mass spectrometry have also emerged alongside the latest developments in the former procedures. This work intends to provide an updated and extensive overview since 1991 on the principal applications of all these techniques together with their advantages and disadvantages for detecting the authenticity of dairy products. The scope and limits of different tools are also discussed.

Subcloning the MAC-T bovine mammary epithelial cell line: morphology, growth properties, and cytogenetic analysis of clonal cells

The objectives of the present study were 1) to determine the heterogeneity of the MAC-T cell line; 2) to examine whether homogeneous clones could be derived from MAC-T cells; and 3) to examine cell morphology, cytoskeletal characteristics, size, colony-forming ability, growth characteristics, beta-casein production, response to oxytocin, and cytogenetic properties of the clones. Three clonal cells, designated CU-1, CU-2, and CU-3, were derived from MAC-T cells. CU-1 and CU-2 cells were morphologically homogeneous. CU-3 cells were heterogeneous and contained two distinct subtypes. All clones contained cytokeratin 14 and 18. CU-2 and CU-3 cells were 30 and 18% larger, respectively, than CU-1 cells. CU-1 cells did not grow in serum-free medium. Doubling times for MAC-T, CU-2, and CU-3 were 46, 48, and 78 h, respectively, in serum-free medium. MAC-T cells and clones constitutively expressed beta-casein in culture ranging from .1 to .3 micrograms/ml per 24 h. Cytogenetic analyses revealed Robertsonian translocations and isochromosomes in the clonal lines. We conclude that parental MAC-T cells are heterogeneous in morphology, growth, and cytogenetic characteristics.

Bovine mammary myoepithelial cells. 1. Isolation, culture, and characterization

The objective of this study was to isolate, purify, culture, and characterize myoepithelial cells from bovine mammary glands. Myoepithelial cells were separated from other mammary and blood cells after collagenase digestion and centrifugation using metrizoate-ficoll gradients. Myoepithelial cells were identified by their characteristic morphology and cloned using selective detachment. They contained many densely packed myofilaments, very few cytoplasmic organelles, elongated surface projections, and a dense, irregularly shaped nuclei. Some cells were as large as 1.2 mm in culture. Myoepithelial cells contained an extensive network of cytoskeletal proteins, including alpha-smooth muscle actin, alpha-actinin, and vimentin. When cultured, they tended to repel one another and never grew as closely associated cells. The myoepithelial nature of these cells was verified by showing that they contracted in response to oxytocin, bound oxytocin, and did not produce casein. Myoepithelial cells from fetal and lactating glands grew very well in culture. Active division of myoepithelial cells could be maintained for at least 3 mo, and cells could be serially subcultured at least seven times. The successful isolation and culture of bovine mammary myoepithelial cells make utilization of these cells possible in order to study their role in mammary growth and differentiation and milk ejection.

Isolation and characterization of monoclonal antibody directed against bovine alpha s2-casein

A monoclonal antibody 62-1A of isotype IgM, directed against bovine alpha s2-casein, was isolated and characterized. Monoclonal antibody 62-1A recognized bovine alpha s2-11P- and alpha s2-9P-caseins by indirect solid phase radioimmunoassay and Western blot analysis. Crossreactivity toward native genetic variants (A, B, and C) of alpha s1-casein was similar but lower (approximately 60 to 70%) than that for alpha s2-11P-casein). Little or no crossreactivity was observed for other bovine milk or serum proteins. Antibody affinity for alpha s2-11P-casein was 1.3 x 10(9)/M. As little as 25 ng/ml (.5 ng/well) of alpha s2-11P-casein was detected by solid phase radioimmunoassay.