Proliferative responses towards native, heat-denatured and pepsin-treated ovalbumin by peripheral blood mononuclear cells from patients with hen's egg-sensitive atopic dermatitis

Implication of a positive virtual crossmatch with negative flow crossmatch: A mind-boggler

There are occasions when tests performed before considering a patient for transplant are ambiguous and require further workup. One such condition is the presence of a positive virtual crossmatch (VXm) (anti-human leukocyte antigen [HLA-A]*26: 01 antibody in this case) with a negative complement-dependent cytotoxicity, Luminex, and flow crossmatch. To ascertain the nature of the antibody, the beads used in single-antigen bead assay (SAB) were treated by acid to denature the antigens and retested with the control and test sample. The mean fluorescence intensities (MFIs) from the patient sera with acid-treated beads increased considerably as compared to the regularly untreated SAB indicating additional antigen epitopes become available by the denaturation process. The MFIs of the antibodies from that of the control sera were reduced to half on testing with the acid-treated SAB assay, indicating that HLA antigen HLA-A*26 was susceptible to acid treatment. Therefore, results of VXm should be interpreted with caution.

Tandem ion exchange fractionation of chicken egg white reveals the presence of proliferative bioactivity

Chicken eggs are recognized for their versatility as a food product and as a model for research in biology and medicine. This study investigated the egg white as a source of bioactive compounds. Egg white was fractionated using tandem ion exchange chromatography (SAX and SCX), and seven fractions were assessed for any associated bioactivity. Four fractions at various protein concentrations were shown to contain proliferative bioactivity that exceeded the FBS control. The most potent fraction (6) was used in an in vitro wound closure assay to demonstrate a positive influence on cell migration and restored scratch wounds more rapidly than the control. LC-MS/MS identified 33 proteins in fraction 6 of egg white, most of which play important roles in cell growth and development, signaling, motility, and proliferation. These candidate bioactives suggest that the egg white contains essential compounds that contribute to the growth of an embryo prior to fertilization.

Changes in the ovalbumin proteolysis profile by high pressure and its effect on IgG and IgE binding

Egg proteins are responsible for one of the most common forms of food allergy, especially in children, and one of the major allergens is ovalbumin (OVA). With the aim to examine the potential of high pressure to enhance the enzymatic hydrolysis of OVA and modify its immunoreactivity, the protein was proteolyzed with pepsin under high-pressure conditions (400 MPa). Characterization of the hydrolysates and peptide identification was performed by reversed-phase high-performance liquid chromatography-tandem mass spectrometry (RP-HPLC-MS/MS). The antigenicity (binding to IgG) and binding to IgE, using the sera of patients with specific IgE to OVA, were also assessed. The results showed that, upon treatment with pepsin at 400 MPa, all of the intact protein was removed in minutes, leading to the production of hydrolysates with lower antigenicity than those produced in hours at atmospheric pressure. However, the exposure of new target residues only partially facilitated the removal of allergenic epitopes, because the hydrolysates retained residual IgG- and IgE-binding properties as a result of the accumulation of large and hydrophobic peptides during the initial stages of hydrolysis. These peptides disappeared at later stages of proteolysis, although reactivity toward IgG and IgE was not completely abolished. Some fragments identified in the hydrolysates (such as Leu124-Phe134, Ile178-Ala187, Leu242-Leu252, Gly251-Ile259, Lys322-Gly343, Phe358-Phe366, and Phe378-Pro385) carried previously identified IgE-binding epitopes. Because some of the peptides found, such as Phe358-Phe366, probably contain only one binding site for IgE, the possibility to use high pressure to tailor hydrolysates that contain mostly peptides with only one IgE-binding site, which may help the immune system to tolerate egg proteins, is suggested.