Characterization of endotoxin and mouse allergen exposures in mouse facilities and research laboratories

Predictors for Increased and Reduced Rat and Mouse Allergen Exposure in Laboratory Animal Facilities

Introduction

Exposure to rat and mouse allergens during work in laboratory animal facilities represents a risk for being sensitized and developing allergic diseases, and it is important to keep the exposure level as low as possible. The objective of this study was to characterize the personal Mus m 1 and Rat n 1 exposure during work in laboratory animal facilities, and to investigate the effect of identified predictors of increased and reduced exposure.

Methods

Mus m 1 and Rat n 1 were analysed in whole day or task-based personal air samples by enhanced sensitivity sandwich enzyme-linked immunosorbent assay. Information about cage-and-rack systems, tasks, and other conditions known to influence the allergen exposure was registered. Predictors for allergen exposure were identified by multiple linear regression analyses.

Results

The median allergen exposure was 3.0 ng m-3 Mus m 1 and 0.5 ng m-3 Rat n 1, with large task-dependent variations among the samples. The highest exposed job group were animal technicians. Cage emptying and cage washing in the cage washroom represented the highest exposure, whereas animal experiments in the lab/operation room represented the lowest exposure, with laminar airflow bench being an exposure-reducing determinant. Cage changing was the highest exposed task in the animal room, where individually ventilated cages (IVCs) were predictors of reduced exposure for both Mus m 1 and Rat n 1, whereas cage-rack systems with open shelves and sliding doors were predictors of increased Rat n 1 exposure. Cages of IVC type with positive air pressure (IVC+) as well as open shelves and sliding doors were strong predictors of increased exposure during cage emptying and cage washing.

Conclusions

Significant different exposure levels depending on type of work and task imply different risks of sensitization and allergy development. The fact that IVC+ cages have opposite impact on Mus m 1 and Rat n 1 exposure during different tasks may have positive clinical implications when taken into account.

Occupational Animal Allergy

PURPOSE OF REVIEW

This review explores animal allergen exposure in research laboratories and other work settings, focusing on causes and prevention.

RECENT FINDINGS

(1) Consistent with the hygiene hypothesis, there is new evidence that early childhood exposure to pets produces changes in the gut microbiome that likely lead to a lower risk of allergy. (2) Anaphylaxis from laboratory animal bites occurs more frequently than suggested by prior literature. (3) Animal allergens represent an occupational hazard in a wide variety of work settings ranging from fields that work with animals to public settings like schools and public transportation where allergens are brought into or are present in the workplace. Exposure to animal allergens can result in allergy, asthma, and anaphylaxis. Animal allergy has been most studied in the research laboratory setting, where exposure reduction can prevent the development of allergy. Similar prevention approaches need to be considered for other animal work environments and in all settings where animal allergens are present.

Impact of environmental microbiota on human microbiota of workers in academic mouse research facilities: An observational study

Objectives

To characterize the microbial environment of workers in academic mouse research facilities using endotoxin, 16S qPCR, and 16S amplicon sequencing. To determine whether the work microbiome contributes to the human microbiome of workers.

Methods

We performed area air sampling from the animal rooms, dirty, middle, and setup cage wash locations in four academic mouse research facilities. 10 workers in the dirty cage wash area underwent personal air sampling as well as repeated collection of nasal, oral, and skin samples before and after the work shift. Environmental samples underwent measurement of endotoxin, mouse allergen, bacteria copy number via 16S qPCR, and microbial identification via 16S rDNA sequencing. 16S rDNA sequencing was also performed on human samples before and after the work shift. SourceTracker was used to identify the contribution of the work microbiome to the human microbiome.

Results

Median endotoxin levels ranged from undetectable to 1.0 EU/m³. Significant differences in mouse allergen levels, bacterial copy number, microbial richness, and microbial community structure were identified between animal, dirty, middle, and setup cage wash locations. Endotoxin levels had only a moderate correlation with microbial composition. Location within a facility was a stronger predictor of microbial community composition (R² = 0.41, p = 0.002) than facility. The contribution of the work microbiome to the pre-shift human microbiome of workers was estimated to be 0.1 ± 0.1% for the oral microbiome; 3.1 ± 1.9% for the nasal microbiome; and 3.0 ± 1.5% for the skin microbiome.

Conclusions

The microbial environment of academic animal care facilities varies significantly by location rather than facility. Endotoxin is not a proxy for assessment of environmental microbial exposures using 16S qPCR or 16S rDNA sequencing. The work microbiome contributes to the composition of the nasal and skin microbiome of workers; the clinical implications of this observation should be further studied.

Exposure to high endotoxin concentration increases wheezing prevalence among laboratory animal workers: a cross-sectional study

Background

Endotoxin from Gram-negative bacteria are found in different concentrations in dust and on the ground of laboratories dealing with small animals and animal houses.

Methods

Cross-sectional study performed in workplaces of two universities. Dust samples were collected from laboratories and animal facilities housing rats, mice, guinea pigs, rabbits or hamsters and analyzed by the “Limulus amebocyte lysate” (LAL) method. We also sampled workplaces without animals. The concentrations of endotoxin detected in the workplaces were tested for association with wheezing in the last 12 months, asthma defined by self-reported diagnosis and asthma confirmed by bronchial hyperresponsiveness (BHR) to mannitol.

Results

Dust samples were obtained at 145 workplaces, 92 with exposure to animals and 53 with no exposure. Exposed group comprised 412 subjects and non-exposed group comprised 339 subjects. Animal-exposed workplaces had higher concentrations of endotoxin, median of 34.2 endotoxin units (EU) per mg of dust (interquartile range, 12.6–65.4), as compared to the non-exposed group, median of 10.2 EU/mg of dust (interquartile range, 2.6–22.2) (p < 0.001). The high concentration of endotoxin (above whole sample median, 20.4 EU/mg) was associated with increased wheezing prevalence (p < 0.001), i.e., 61 % of workers exposed to high endotoxin concentration reported wheezing in the last 12 months compared to 29 % of workers exposed to low endotoxin concentration. The concentration of endotoxin was not associated with asthma report or with BHR confirmed asthma.

Conclusion

Exposure to endotoxin is associated with a higher prevalence of wheezing, but not with asthma as defined by the mannitol bronchial challenge test or by self-reported asthma. Preventive measures are necessary for these workers.

Laboratory Animal Allergy in the Modern Era

Laboratory animal workers face a high risk of developing laboratory animal allergy as a consequence of inhaling animal proteins at work; this has serious consequences for their health and future employment. Exposure to animal allergen remains to be the greatest risk factor although the relationship is complex, with attenuation at high allergen exposure. Recent evidence suggests that this may be due to a form of natural immunotolerance. Furthermore, the pattern of exposure to allergen may also be important in determining whether an allergic or a tolerant immune response is initiated. Risk associated with specific tasks in the laboratory need to be determined to provide evidence to devise a code of best practice for working within modern laboratory animal facilities. Recent evidence suggests that members of lipocalin allergens, such as Mus m 1, may act as immunomodulatory proteins, triggering innate immune receptors through toll-like receptors and promoting airway laboratory animal allergy. This highlights the need to understand the relationship between endotoxin, animal allergen and development of laboratory animal allergy to provide a safe working environment for all laboratory animal workers.

Comparison of endotoxin levels and gram-negative bacteria under different conditions in microbial laboratories and a biowaste site

In this study, we assessed airborne endotoxin levels in university laboratories, hospital diagnostic laboratories, and a biowaste site. We also investigated indoor and outdoor sampling, sampling site, type of ventilation system, presence of open biowaste boxes, weather, and detection of Gram-negative bacteria (GNB). A total of 69 air samples were collected from 11 facilities in three institutions. Average total airborne endotoxin levels ranged from <0.01 to 10.02 EU m(-3), with an overall mean of 1.03 EU m(-3). Endotoxin levels were high in window-ventilated facilities, in facilities in which GNB were detected; levels were also high when it was rainy (all ps<0.05). Endotoxin levels were significantly correlated with humidity (r=0.70, p<0.01). The presence of HVAC; humidity; and the presence of open biowaste boxes affect endotoxin levels in laboratories.

Gene-environment interactions influence airways function in laboratory animal workers

BACKGROUND

Most diseases, including asthma, result from the interaction between environmental exposures and genetic variants. Functional variants of CD14 negatively affect lung function in farm workers and children exposed to animal allergens and endotoxin.

OBJECTIVE

We hypothesized that CD14 polymorphisms interact with inhaled endotoxin, mouse allergen, or both to decrease airways function in laboratory animal workers.

METHODS

Three hundred sixty-nine Caucasian workers completed a symptom and work exposure questionnaire, skin prick testing, and spirometry. Individual exposure estimates for endotoxin and murine allergen were calculated by weighting task-based breathing zone concentrations by time reported for each task and length of time in the current job. Real-time PCR was used to assess CD14/-1619, -550, and -159 alleles. Multiple linear regression predicting airways function included an interaction term between genotype and exposure.

RESULTS

Workers at the highest quartile of the natural log-transformed cumulative endotoxin exposure and with the endotoxin-responsive CD14/-1619 G allele had significantly lower FEV(1) and forced expiratory flow, midexpiratory phase (FEF(25-75)) percent predicted compared with workers with an AA genotype, with no significant differences noted at lower endotoxin levels for either genotype. The gene-environment effect was marked for atopic workers. Laboratory animal allergy, murine allergen exposure, CD14/-159 or -550 genotype, and a gene-exposure interaction term for these genotypes and exposures did not predict changes in lung function.

CONCLUSIONS

A significant gene-environment interaction affects airways function in laboratory animal workers. More highly endotoxin-exposed workers with CD14/-1619G alleles have significantly lower FEV(1) and FEF(25-75) percent predicted than those with CD14/-1619AA alleles. Atopic workers are particularly affected by cumulative endotoxin exposures.

Association of Toll-like receptor 4 alleles with symptoms and sensitization to laboratory animals

BACKGROUND

Researchers and technicians working with laboratory animals (LAs) are exposed to animal allergen and endotoxin, which can interact to potentiate or inhibit symptoms or allergic responses. We hypothesized that functional genetic variants of Toll-like receptor 4 (TLR4), a key surface receptor for endotoxin, interface between worker and workplace and affect animal sensitization, symptoms, or both.

OBJECTIVE

We sought to determine whether TLR4/8551 variants alter the risk for LA sensitization, symptoms, or both.

METHODS

Three hundred thirty-five researchers, 195 of whom worked with animals, completed questions on workplace practices and symptoms and underwent skin prick tests or RASTs to common and animal allergens. Real-time PCR assessed TLR4/8551 and TLR4/8851 variants. Nominal logistic regression was used to analyze the contribution of demographic, exposure, and genetic variables to outcomes of interest.

RESULTS

Twenty-one percent of workers were LA sensitized, and 29% reported 1 or more symptoms to LAs. The TLR4/8551 G variant, which is less responsive to endotoxin, was detected in 9% and in linkage disequilibrium with the TLR4/8851 T allele. The G variant significantly associated with atopy and LA sensitization. Workers with the G variant spent significantly longer hours in high endotoxin/animal allergen tasks compared with those with the AA variant, which is perhaps less affected by endotoxin exposures. In multivariate analyses the G variant and longer animal research hours increased the risk of LA sensitization. Job tasks and LA sensitization, but not TLR4 variants, were predictors of LA-induced symptoms.

CONCLUSION

Workers with TLR4 variants that reduce responsiveness to endotoxin have higher risks for LA and other allergen sensitization but spend longer hours in tasks with high endotoxin and animal allergen exposures.

Rodent allergen in Los Angeles inner city homes of children with asthma

Recent studies have examined the presence of mouse allergen in inner city children with asthma. Researchers have found high levels of rodent allergen in homes sampled in the northeast and midwest United States, but there has been considerable variation between cities, and there have been few studies conducted in western states. We evaluated the frequency of rodent sightings and detectable mouse allergen and the housing conditions associated with these outcomes in inner city homes in Los Angeles. Two hundred and two families of school children, ages 6-16 living in inner city neighborhoods, participated in the study. Families were predominantly Latino (94%), and Spanish speaking (92%). At study entry, parents completed a home assessment questionnaire, and staff conducted a home evaluation and collected kitchen dust, which was analyzed for the presence of mouse allergen. Fifty-one percent of homes had detectable allergen in kitchen dust. All 33 families who reported the presence of rodents had detectable allergen in the home and were also more likely to have increased levels of allergen compared to those who did not report rodents. Unwashed dishes or food crumbs, lack of a working vacuum, and a caretaker report of a smoker in the home were all significantly associated with a greater risk of rodent sightings or detectable allergen (P<0.05). Detached homes were significantly more likely to have detectable allergen. The prevalence of allergen is common enough that it may have public health implications for asthmatic children, and detectable allergen was not routinely identified based on rodent sightings. Many of the predictors of rodent allergen are amenable to low-cost interventions that can be integrated with other measures to reduce exposure to indoor allergens.