Animal Allergens, Endotoxin, and β-(1,3)-Glucan in Small Animal Practices: Exposure Levels at Work and in Homes of Veterinary Staff

OBJECTIVES

In veterinary settings, high exposures to animal allergens and microbial agents can be expected. However, occupational exposure levels are largely unknown. The objective of this study was to estimate the allergen, endotoxin, and β-(1,3)-glucan concentrations in small animal practices and in the homes of practice employees.

METHODS

Dust samples were collected using electrostatic dust fall collectors in diverse rooms of 36 small animal practices, as well as in employees' homes. Major animal allergens (Fel d 1, Can f 1, Ory c 3, Cav p 1, Equ c 1, Bos d 2), domestic mite (DM) allergens, and β-(1,3)-glucan levels were measured using enzyme immunoassays. Endotoxin was determined using the Limulus amoebocyte lysate assay. Influences on exposure levels were analyzed using multilevel models.

RESULTS

The levels of Can f 1, Fel d 1, Ory c 3, and Cav p 1 were up to 30 times higher in practices compared with homes without animals, but significantly lower compared with the homes with the respective pet. Although horses were not treated in the practices, Equ c 1 was found in 87.5% of samples, with the highest concentrations measured in changing rooms. DM levels were significantly lower in practices than in all private homes, and endotoxin levels were similar to those in homes with pets. In the practice itself, exposure levels were significantly influenced by animal presence, type of the room, and area per employee; whereas, room volume and diverse cleaning measures had mostly no effect.

CONCLUSIONS

Exposure to animal allergens is high in veterinary practices, but it does not reach levels of households with pets. Domestic mite allergen and endotoxin exposure seem to be low for workers in veterinary practices. The high Equ c 1 detection rate strongly indicates dispersal of allergens, most likely through clothing and hair.

Curdlan stimulates tissue mast cells to synthesize pro-inflammatory mediators, generate ROS, and migrate via Dectin-1 receptor

Mast cells (MCs) are engaged in host defense against various pathogens as they are equipped with pattern recognition receptors (PRRs). Among PRRs expressed on MCs, there are also molecules recognizing components of the fungal cell wall, which are able to induce cellular activation and response. However, little information is available concerning the MC activation by various fungal-derived components. The aim of the study was to determine whether curdlan, a model fungal particle of β-(1,3)-glucan, can directly stimulate tissue MCs. We demonstrated that curdlan triggers MCs to initiate pro-inflammatory response as it activates these cells to synthesize essential pro-inflammatory and/or immunoregulatory factors. We also showed that curdlan serves as a potent chemoattractant for MCs and stimulates those cells to generate reactive oxygen species (ROS). Finally, we documented that curdlan induces MC response via Dectin-1. Our observations support the idea that MCs serve as important sentinels modulating immune response during fungal infection.

β-(1,3)-Glucan Unmasking in Some Candida albicans Mutants Correlates with Increases in Cell Wall Surface Roughness and Decreases in Cell Wall Elasticity

Candida albicans is among the most common human fungal pathogens, causing a broad range of infections, including life-threatening systemic infections. The cell wall of C. albicans is the interface between the fungus and the innate immune system. The cell wall is composed of an outer layer enriched in mannosylated glycoproteins (mannan) and an inner layer enriched in β-(1,3)-glucan and chitin. Detection of C. albicans by Dectin-1, a C-type signaling lectin specific for β-(1,3)-glucan, is important for the innate immune system to recognize systemic fungal infections. Increased exposure of β-(1,3)-glucan to the immune system occurs when the mannan layer is altered or removed in a process called unmasking. Nanoscale changes to the cell wall during unmasking were explored in live cells with atomic force microscopy (AFM). Two mutants, the cho1Δ/Δ and kre5Δ/Δ mutants, were selected as representatives that exhibit modest and strong unmasking, respectively. Comparisons of the cho1Δ/Δ and kre5Δ/Δ mutants to the wild type reveal morphological changes in their cell walls that correlate with decreases in cell wall elasticity. In addition, AFM tips functionalized with Dectin-1 revealed that the forces of binding of Dectin-1 to all of the strains were similar, but the frequency of binding was highest for the kre5Δ/Δ mutant, decreased for the cho1Δ/Δ mutant, and rare for the wild type. These data show that nanoscale changes in surface topology are correlated with increased Dectin-1 adhesion and decreased cell wall elasticity. AFM, using tips functionalized with immunologically relevant molecules, can map epitopes of the cell wall and increase our understanding of pathogen recognition by the immune system.

A combined chemical and enzymatic method to determine quantitatively the polysaccharide components in the cell wall of yeasts

A reliable method to determine cell wall polysaccharides composition in yeast is presented, which combines acid and enzymatic hydrolysis. Sulphuric acid treatment is used to determine mannans, whereas specific hydrolytic enzymes are employed in a two sequential steps to quantify chitin and the proportion of β-(1,3) and β-(1,6)-glucan in the total β-glucan of the cell wall. In the first step, chitin and β-(1,3)-glucan were hydrolysed into their corresponding monomers N-acetylglucosamine and glucose, respectively, by the combined action of a chitinase from Streptomyces griseus and a pure preparation of endo/exo-β-(1,3)-glucanase from Trichoderma species. This step was followed by addition of recombinant endo-β-(1,6)-glucanase from Trichoderma harzianum with β-glucosidase from Aspergillus niger to hydrolyse the remaining β-glucan. This latter component corresponded to a highly branched β-(1,6)-glucan that contained about 75-80% of linear β-(1,6)-glucose linked units as deduced from periodate oxidation. We validated this novel method by showing that the content of β-(1,3), β-(1,6)-glucan or chitin was dramatically decreased in yeast mutants defective in the biosynthesis of these cell wall components. Moreover, we found that heat shock at 42 °C in Saccharomyces cerevisiae and treatment of this yeast species and Candida albicans with the antifungal drug caspofungin resulted in 2- to 3-fold increase of chitin and in a reduction of β-(1,3)-glucan accompanied by an increase of β-(1,6)-glucan, whereas ethanol stress had apparently no effect on yeast cell wall composition.