Selective ovine serum albumin allergy in an adult

Crystal structures of serum albumins from domesticated ruminants and their complexes with 3,5-diiodosalicylic acid

Serum albumin (SA) is the most abundant protein in plasma and is the main transporter of molecules in the circulatory system of all vertebrates, with applications in medicine, the pharmaceutical industry and molecular biology. It is known that albumins from different organisms vary in sequence; thus, it is important to know the impact of the amino-acid sequence on the three-dimensional structure and ligand-binding properties. Here, crystal structures of ovine (OSA) and caprine (CSA) serum albumins, isolated from sheep and goat blood, are described, as well those of their complexes with 3,5-diiodosalicylic acid (DIS): OSA-DIS (2.20 Å resolution) and CSA-DIS (1.78 Å resolution). The ligand-free OSA structure was determined in the trigonal space group P3221 at 2.30 Å resolution, while that of CSA in the orthorhombic space group P212121 was determined at 1.94 Å resolution. Both albumins are also capable of crystallizing in the triclinic space group P1, giving isostructural crystals that diffract to around 2.5 Å resolution. A comparison of OSA and CSA with the closely related bovine serum albumin (BSA) shows both similarities and differences in the distribution of DIS binding sites. The investigated serum albumins from domesticated ruminants in their complexes with DIS are also compared with the analogous structures of equine and human serum albumins (ESA-DIS and HSA-DIS). Surprisingly, despite 98% sequence similarity, OSA binds only two molecules of DIS, whereas CSA binds six molecules of this ligand. Moreover, the binding of DIS to OSA and CSA introduced changes in the overall architecture of the proteins, causing not only different conformations of the amino-acid side chains in the binding pockets, but also a significant shift of the whole helices, changing the volume of the binding cavities.

Is abnormal liver function correlated with food sensitisation in adults? US NHANES, 2005-2006

BACKGROUND

Associations between liver function and serum IgE levels have recently been observed in children. However, the relationship in adults is unclear. Therefore, it was aimed to study associations of liver function and serum total and food-specific IgE concentrations in a national and population-based study.

METHOD

Data were retrieved from the United States National Health and Nutrition Examination Surveys, 2005-2006 including demographics, liver status tests, biomarkers, lifestyle factors, and serum total and food-specific IgE concentrations. Participants aged 20 and above were included. Analyses included t-test, chi-square test, and survey-weighted regression modelling.

RESULTS

After adjusting for age, sex, ethnicity, vitamin D, waist circumference, family poverty income ratio, total cholesterol, ever asthma, total protein, and survey weighting, abnormal gamma glutamyl transpeptidase was significantly associated with food sensitisation (peanut: OR 2.17, 95%CI 1.60-2.94, P<0.001; egg: OR 2.55, 95%CI 1.32-4.90, P=0.008; milk: OR 2.59, 95%CI 1.56-4.31, P=0.001; shrimp: OR 1.81, 95%CI 1.29-2.55, P=0.002). Moreover, both abnormal albumin and alanine transaminase were associated with egg sensitisation (OR 1.96, 95%CI 1.12-3.43, P=0.022 and OR 2.06, 95%CI 1.04-4.09, P=0.040, respectively).

CONCLUSION

Abnormal liver status tests were correlated with serum food-specific IgE concentrations in adults. Future research with longitudinal design or in clinical settings may be warranted confirming or refuting the observations made in the present epidemiological study.

Serum albumins-unusual allergens

BACKGROUND

Albumins are multifunctional proteins present in the blood serum of animals. They can bind and transport a wide variety of ligands which they accommodate due to their conformational flexibility. Serum albumins are highly conserved both in amino acid sequence and three-dimensional structure. Several mammalian and avian serum albumins (SAs) are also allergens. Sensitization to one of the SAs coupled with the high degree of conservation between SAs may result in cross-reactive antibodies in allergic individuals. Sensitivity to SA generally begins with exposure to an aeroallergen, which can then lead to cross-sensitization to serum albumins present in food.

SCOPE OF REVIEW

This review focuses on the allergenicity of SAs presented in a structural context.

MAJOR CONCLUSIONS

SA allergenicity is unusual taking into account the high sequence identity and similarity between SA from different species and human serum albumin. Cross-reactivity of human antibodies towards different SAs is one of the most important characteristics of these allergens.

GENERAL SIGNIFICANCE

Establishing a relationship between sequence and structure of different SAs and their interactions with antibodies is crucial for understanding the mechanisms of cross-sensitization of atopic individuals. Structural information can also lead to better design and production of recombinant SAs to replace natural proteins in allergy testing and desensitization. Therefore, structural analyses are important for diagnostic and treatment purposes. This article is part of a Special Issue entitled Serum Albumin.

Role of sensitization to mammalian serum albumin in allergic disease

Serum albumin (SA) constitutes an intriguing puzzle that is involved in allergic sensitizations from different sources and induces different clinical manifestations. In this article, we describe the role of sensitization to SAs in inducing allergic diseases and the complex interactions and cross-reactivity between SA resulting from its presence in various mammalian tissues and fluids. SAs alone are an uncommon cause of allergic sensitization in airways, but these allergenic proteins likely play a significant role as cross-reacting allergens in individuals sensitized to several types of animal dander. SAs are a minor allergen in milk but a major allergen in meats. Recently, bovine SA has been added to the culture medium of spermatozoids used for artificial insemination. As a consequence, some case reports have shown that bovine SA may be a causative agent in severe anaphylaxis after standard intrauterine insemination or in vitro fertilization.