Racial differences in prevalence of a supratypic HLA-genetic marker immaterial to pre-employment testing for susceptibility to chronic beryllium disease

Research to Practice Implications of High-Risk Genotypes for Beryllium Sensitization and Disease

OBJECTIVE

Beryllium workers may better understand their genetic susceptibility to chronic beryllium disease (CBD) expressed as population-based prevalence, rather than odds ratios from case-control studies.

METHODS

We calculated CBD prevalences from allele-specific DNA sequences of 853 workers for Human Leukocyte Antigen (HLA)-DPB1 genotypes and groups characterized by number of E69-containing alleles and by calculated surface electronegativity of HLA-DPB1.

RESULTS

Of 18 groups of at least 10 workers with specific genotypes, CBD prevalence was highest, 72.7%, for the HLA-DPB102:01:02/DPB117:01 genotype. Population-based grouped genotypes with two E69 alleles wherein one allele had -9 surface charge had a beryllium sensitization (BeS) of 52.6% and a CBD prevalence of 42.1%.

CONCLUSIONS

The high CBD and BeS prevalences associated with -9-charged E69 alleles and two E69s suggest that workers may benefit from knowing their genetic susceptibility in deciding whether to avoid future beryllium exposure.

Genetic susceptibility testing for beryllium: worker knowledge, beliefs, and attitudes

BACKGROUND

We sought to gain insight into workers' knowledge, beliefs, and attitudes on the subject of testing for genetic susceptibility to beryllium.

METHODS

Five focus groups were held with 30 current and former beryllium workers and nine family members. Audio recordings were transcribed and assessed by hierarchical coding using an inductive approach.

RESULTS

Some workers were unclear about the distinction between genotoxicity and heritability. A key finding is that they perceived the benefits of a positive test result to be related to enhanced autonomous decision-making. The major concern cited by participants was potential abuse of genetic information by employers. Complete financial separation of a prospective testing entity from the employer was seen as crucial.

CONCLUSIONS

A window of opportunity exists to create regional partnerships for translational research on genetic susceptibility testing. Such partnerships would involve labor, management, public health scientists, primary care professionals, and other stakeholders. They would be critical to identifying testing strategies that maximize worker autonomy along with the public health advantages of genetic testing.

Genetic variability in susceptibility to occupational respiratory sensitization

Respiratory sensitization can be caused by a variety of substances at workplaces, and the health and economic burden linked to allergic respiratory diseases continues to increase. Although the main factors that affect the onset of the symptoms are the types and intensity of allergen exposure, there is a wide range of interindividual variation in susceptibility to occupational/environmental sensitizers. A number of gene variants have been reported to be associated with various occupational allergic respiratory diseases. Examples of genes include, but are not limited to, genes involved in immune/inflammatory regulation, antioxidant defenses, and fibrotic processes. Most of these variants act in combination with other genes and environmental factors to modify disease progression, severity, or resolution after exposure to allergens. Therefore, understanding the role of genetic variability and the interaction between genetic and environmental/occupational factors provides new insights into disease etiology and may lead to the development of novel preventive and therapeutic strategies. This paper will focus on the current state of knowledge regarding genetic influences on allergic respiratory diseases, with specific emphasis on diisocyanate-induced asthma and chronic beryllium disease.

Risk of chronic beryllium disease by HLA-DPB1 E69 genotype and beryllium exposure in nuclear workers

RATIONALE

Beryllium sensitization (BeS) and chronic beryllium disease (CBD) are determined by at least one genetic factor, a glutamic acid at position 69 (E69) of the HLA-DPB1 gene, and by exposure to beryllium. The relationship between exposure and the E69 genotype has not been well characterized.

OBJECTIVES

The study goal was to define the relationship between beryllium exposure and E69 for CBD and BeS.

METHODS

Workers (n = 386) from a U.S. nuclear weapons facility were enrolled into a case-control study (70 BeS, 61 CBD, and 255 control subjects). HLA-DPB1 genotypes were determined by sequence-specific primer-polymerase chain reaction. Beryllium exposures were reconstructed on the basis of worker interviews and historical exposure measurements.

MEASUREMENTS AND MAIN RESULTS

Any E69 carriage increased odds for CBD (odds ratio [OR], 7.61; 95% confidence interval [CI], 3.66-15.84) and each unit increase in lifetime weighted average exposure increased the odds for CBD (OR, 2.27; 95% CI, 1.26-4.09). Compared with E69-negative genotypes, a single E69-positive *02 allele increased the odds for BeS (OR, 12.01; 95% CI, 4.28-33.71) and CBD (OR, 3.46; 95% CI, 1.42-8.43). A single non-*02 E69 allele further increased the odds for BeS (OR, 29.54; 95% CI, 10.33-84.53) and CBD (OR, 11.97; 95% CI, 5.12-28.00) and two E69 allele copies conferred the highest odds for BeS (OR, 55.68; 95% CI, 14.80-209.40) and CBD (OR, 22.54; 95% CI, 7.00-72.62).

CONCLUSIONS

E69 and beryllium exposure both contribute to the odds of CBD. The increased odds for CBD and BeS due to E69 appear to be differentially distributed by genotype, with non-*02 E69 carriers and E69 homozygotes at higher odds than those with *02 genotypes.

Application of oligonucleotide microarray technology to toxic occupational exposures

Microarray technology has advanced toward analysis of toxic occupational exposures in biological systems. Microarray analysis is an ideal way to search for biomarkers of exposure, even if no specific gene or pathway has been identified. Analysis may now be performed on thousands of genes simultaneously, as opposed to small numbers of genes as in the past. This ability has been put to use to analyze gene expression profiles of a variety of occupational toxins in animal models to classify toxins into specific categories based on response. Analysis of normal human cell strains allows an extension of this analysis to investigate the role of interindividual variation in response to various toxins. This methodology was used to analyze four occupationally related toxins in our lab: oxythioquinox (OTQ), a quinoxaline pesticide; malathion, an organophosphate pesticide; di-n-butyl phthalate (DBP), a chemical commonly found in personal care and cosmetic items; and benzo[a]pyrene (BaP), an environmental and occupational carcinogen. The results for each exposure highlighted signaling pathways involved in response to these occupational exposures. Both pesticides showed increase in metabolic enzymes, while DBP showed alterations in genes related to fertility. BaP exposure showed alterations in two cytochrome P450s related to carcinogenicity. When used with occupational exposure information, these data may be used to augment risk assessment to make the workplace safer for a greater proportion of the workforce, including individuals susceptible to disease related to exposures.

Beryllium: A Modern Industrial Hazard

Beryllium exposure can cause a granulomatous lung disease in workers who develop a lymphocyte-mediated sensitization to the metal. Workers in diverse industries are at risk because beryllium's properties are critical to nuclear, aerospace, telecommunications, electronic, metal alloy, biomedical, and semiconductor industries. The occupational air concentration standard's failure to protect beryllium workers is driving many scientific and occupational health advances. These developments include study of bioavailability of different physicochemical forms of beryllium, medical surveillance to show effectiveness of skin protection in preventing sensitization in high-risk processes, gene-environment interaction, transgenic mice for use in experimental research, and risk-based management of industrial exposures in the absence of effective exposure-response information. Beryllium sensitization and disease prevention are paradigms for much broader public health action in both occupational and general population settings.

Comparative analysis between CFSE flow cytometric and tritiated thymidine incorporation tests for beryllium sensitivity

BACKGROUND

In this study, we evaluated alternative possibility for CFSE beryllium flow cytometric test against beryllium blood lymphocyte proliferation test (BeLPT) as a standard radioactive clinical screening method to identify sensitization to beryllium.

METHODS

Delta PD (the ratio of divided cell population to the total number of cells with subtracted counts of unstimulated cells) of specific beryllium-induced pathogenic CD3+ CD4+ T-lymphocytes and stimulation index (SI) in CFSE proliferation test was compared with delta counts per minute (mean test CPM minus mean control CPM) and SI in radioactive blood BeLPT.

RESULTS

Comparison analysis of CFSE and BeLPT demonstrated excellent agreement between delta PD and delta CPM (kappa = 0.845, P << 0.0001). We determined 6.8% positive subjects in the beryllium-exposed, Be-LPT-negative group. The decreased mean difference of these indexes to percentage of average and the long tail in the plot reflects increased sensitivity. CFSE/CD4+ T-cell proliferation assay has 100% specificity, significantly higher sensitivity and efficiency than BeLPT.

CONCLUSIONS

Both delta PD, measured by the precursor frequencies method in CFSE assay and delta CPM, defined by tritiated thymidine in BeLPT, can be used for the enumeration of beryllium specific CD4+ T-cell proliferation and may substantially improve the quality of the early diagnosis of beryllium hypersensitivity.

Ethical considerations in testing workers for the -Glu69 marker of genetic susceptibility to chronic beryllium disease

OBJECTIVE

The most compelling real-world example of genetic testing for susceptibility to a workplace exposure involves those industries that process or fabricate beryllium. We examined ethical issues associated with testing for susceptibility to chronic beryllium disease.

METHODS

Using ethical and clinical criteria, we examined voluntary employer-sponsored testing programs in which individual results are reported directly to workers in a confidential manner.

RESULTS

Under reasonable assumptions, the longitudinal positive predictive value of the HLA-DPB1-Glu69 marker of susceptibility to beryllium disease is 12%. Interpretive challenges further limit the utility of the test and may inadvertently suggest a false sense of safety among workers. Concerns about confidential participation and pressures to be tested also must be addressed.

CONCLUSIONS

Difficulties surrounding the interpretation of the HLA-DPB1-Glu69 marker, lack of assurance regarding the protection of worker confidentiality, and the potential lowering of social barriers to the implementation of mandatory worker screening combine to make testing beryllium workers inappropriate at this time.

Immunogenetic factors in beryllium sensitization and chronic beryllium disease

Exposure to beryllium in the workplace can cause beryllium sensitization and chronic beryllium disease. Sensitization to beryllium can be detected in the laboratory using the beryllium lymphocyte proliferation test. It was shown that anti-HLA antibodies could block the beryllium-specific response in the beryllium lymphocyte proliferation test, thereby implicating HLA genes in chronic beryllium disease. A supratypic genetic marker, HLA-DPB1*E69, was found to be strongly associated with immunologic sensitization to beryllium and chronic beryllium disease in beryllium workers. However, there are 40 HLA-DPB1 gene variants that have E69 but that also have other DNA sequence variations. The purpose of the study was to evaluate the evidence for potential differential susceptibility that may be associated with the physical characteristics of HLA protein molecules for which different HLA-DPB1*E69 variants code; that is, do some HLA-DPB1*E69 variants convey higher risk of beryllium sensitization and chronic beryllium disease than others. To do this, two approaches were pursued: first, detailed analysis of the findings from the published literature was performed, and second, computational chemistry was used to seek clues concerning the physical properties of the HLA protein molecules for which these alleles code. Among the 40 HLA-DPB1 gene variants that code for E69, molecular epidemiological studies have suggested a risk hierarchy, where some variants appear to convey low to moderate risk of chronic beryllium disease (e.g., HLA-DPB1*0201, approximately 3-fold increased risk), some convey an intermediate risk (e.g., HLA-DPB1*1901, approximately 5-fold) and others convey high risk (e.g., HLA-DPB1*1701, >10-fold). Molecular modeling has been used to further investigate a potential mechanistic basis for these observations. We found a strong correlation between the hierarchical order of risk of chronic beryllium disease associated with specific alleles and the predicted surface electrostatic potential and charge of the corresponding isotypes. Therefore, when alleles were grouped by the relative negative charge on the molecules for which they code, the data suggest that those alleles associated with the most negatively charged proteins carry the greatest risk of beryllium sensitization and disease.

Bérylliose pulmonaire chronique (2e partie)

INTRODUCTION

Chronic beryllium disease (CBD) is an occupational lung disease caused by the inhalation of beryllium dust, fumes or metallic salts.

CURRENT DATA

Beryllium affects the lungs via particles deposited in the pulmonary alveoli. These are ingested by alveolar macrophages which act as antigen presenting cells to CD4+ T lymphocytes. T lymphocytes proliferate in response to beryllium antigens and combined with macrophages produce numerous epithelioid granulomas with the release of inflammatory cytokines (IFNgamma, IL-2, TNFalpha and IL6) and growth factors. Beryllium induces macrophage apoptosis which reduces its clearance from the lung which in turn contributes to the host's continual re-exposure and thus a chronic granulomatous disorder. Pulmonary granulomatous inflammation is the primary manifestation of CBD, but the disease occasionally involves other organs such as the liver, spleen, lymph nodes and bone marrow. The clinical, radiological, and histopathological features of CBD can be difficult to distinguish from sarcoidosis. The Beryllium lymphocyte proliferation test (BeLPT) demonstrates a beryllium specific immune response, confirms the diagnosis of CBD, and excludes sarcoidosis.

CONCLUSIONS AND PERSPECTIVES

CBD provides a human model of pulmonary granulomatous disease produced by an occupational exposure, occurring more frequently in those with a genetic pre-disposition. It can be differentiated from sarcoidosis by specific immunological testing.

The association between HLA-DPB1Glu69 and chronic beryllium disease and beryllium sensitization

BACKGROUND

Several case-control studies have found an association between chronic beryllium disease (CBD) and HLA-DPB1 gene variants. However, the relationship between HLA-DPB1 and beryllium sensitization, and whether the presence of one or two HLA-DPB1(Glu69) alleles is differentially associated with CBD and beryllium sensitization have not been completely resolved.

METHODS

Restriction fragment length polymorphism (RFLP) analysis was used to address these questions in a large population-based cohort consisting of 884 beryllium workers (90 with CBD, 64 beryllium sensitized).

RESULTS

HLA-DPB1(Glu69) was associated with both CBD (OR = 9.4; 95% CI = 5.4, 16.6) and sensitization (OR = 3.3, 95% CI = 1.9, 5.9). Further, workers with CBD and sensitization were more likely to be homozygous HLA-DPB1(Glu69) compared to workers without disease or sensitization (P < 0.001).

CONCLUSIONS

Follow-up of this cohort, scrutiny of HLA-DPB1 haplotypes, and evaluation of gene-environment and gene-gene interactions will be important for fully understanding the immunogenetic nature of this occupational disease.