TNF-alpha polymorphisms in chronic beryllium disease and beryllium sensitization

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.

Chronic beryllium disease: an updated model interaction between innate and acquired immunity

During the last decade, there have been concerted efforts to reduce beryllium (Be) exposure in the workplace and thereby reduce potential cases of this occupational lung disorder. Despite these efforts, it is estimated that there are at least one million Be-exposed individuals in the U.S. who are potentially at risk for developing chronic beryllium disease (CBD). Previously, we reviewed the current CBD literature and proposed that CBD represents a model interaction between innate and acquired immunity (Sawyer et al., Int Immunopharmacol 2:249-261, 2002). We closed this review with a section on "future directions" that identified key gaps in our understanding of the pathogenesis of CBD. In the intervening period, progress has been made to fill in some of these gaps, and the current review will provide an update on that progress. Based on recent findings, we provide a new hypothesis to explain how Be drives sustained chronic inflammation and granuloma formation in CBD leading to progressive compromised lung function in CBD patients. This paradigm has direct implications for our understanding of the development of an immune response to Be, but is also likely applicable to other immune-mediated lung diseases of known and unknown etiology.

Influence of ethnicity on pharmacogenetic variation in the Ghanaian population

It has been well established that the frequencies of genomic variants can vary greatly between the populations of different countries. We sought to quantify the intra-population variability in Ghana to determine the value of genotyping studies done at a nationwide level. Further, we investigated the differences between the Ghanaian and other African populations to determine the quality of genomic representation provided by a small subgroup within the continent with regard to the general population. We genotyped 934 unrelated Ghanaian individuals for 15 single nucleotide polymorphisms (SNPs) from genes defined as clinically relevant based on their reported roles in the transport of, metabolism of, or as targets of the medicines listed in the World Health Organization Essential Medicines list. Populations within Ghana and between nations in Western Africa were genetically cohesive. In contrast, populations in other areas of Africa were genetically divergent. Gene allele frequency also differed significantly between the populations in African nations and the United States for several of the SNPs. These results demonstrate that national populations in similar geographic regions, like Africa, may have widely varying genetic allele frequencies for clinically relevant SNPs. Further genotyping studies of specific populations are necessary to provide the best medical care to all individuals.

Beryllium hypersensitivity and chronic beryllium lung disease

PURPOSE OF REVIEW

This review aims to present the clinician with a synthesis of recent studies that have enhanced our understanding of the epidemiology and pathogenesis of beryllium hypersensitivity (BeH) and chronic beryllium disease (CBD).

RECENT FINDINGS

Lower occupational limit levels to beryllium exposure and more stringent preventive measures can decrease the risk for development of BeH and CBD. Beryllium sensitization is determined by a positive beryllium lymphocyte proliferation test (BeLPT). Longitudinal data suggest that BeH progresses to CBD. Together with a comprehensive history the BeLPT may help identify berylliosis in patients erroneously diagnosed to have sarcoidosis. HLA-DPB1-Glu69 marker is associated with increased susceptibility to development of BeH and CBD but poor positive predictive value limits its use; other genetic markers are being investigated. Recent investigations augment our understanding on the role of T-lymphocytes and chemokines in the pathogenesis of beryllium-associated disease. However, the basis for treatment strategies remains scarce.

SUMMARY

Our enhanced understanding of beryllium-associated lung disease potentially provides a window to unraveling other granulomatous diseases. However, even more questions beg to be elucidated and additional efforts are needed to translate this body of knowledge into better prevention and treatment.

Bibliography. Current world literature

This bibliography is compiled by clinicians from the journals listed at the end of this publication. It is based on literature entered into our database between 1 November 2007 and 31 October 2008 (articles are generally added to the database about two and a half months after publication). In addition, the bibliography contains every paper annotated by reviewers; these references were obtained from a variety of bibliographic databases and published between the beginning of the review period and the time of going to press. The bibliography has been grouped into topics that relate to the reviews in this issue.

The uses and adverse effects of beryllium on health

CONTEXT

This review describes the health effects of beryllium exposure in the workplace and the environment.

AIM

To collate information on the consequences of occupational and environmental exposure to beryllium on physiological function and well being.

MATERIALS AND METHODS

The criteria used in the current review for selecting articles were adopted from proposed criteria in The International Classification of Functioning, Disability, and Health. Articles were classified based on acute and chronic exposure and toxicity of beryllium.

RESULTS

The proportions of utilized and nonutilized articles were tabulated. Years 2001-10 gave the greatest match (45.9%) for methodological parameters, followed by 27.71% for 1991-2000. Years 1971-80 and 1981-90 were not significantly different in the information published and available whereas years 1951-1960 showed a lack of suitable articles. Some articles were published in sources unobtainable through requests at the British Library, and some had no impact factor and were excluded.

CONCLUSION

Beryllium has some useful but undoubtedly harmful effects on health and well-being. Measures need to be taken to prevent hazardous exposure to this element, making its biological monitoring in the workplace essential.

Immunology of chronic beryllium disease

PURPOSE OF REVIEW

This review discusses the immunology of chronic beryllium disease. It addresses the importance of the interaction between class II molecules and the T cells that recognize beryllium, along with the subsequent immune response that results in sensitization and disease, and genetic factors leading to variation in this response.

RECENT FINDINGS

HLA-DPB1 with a glutamic acid at amino acid position 69 (Glu69) confers increased risk of beryllium sensitization and is not specific for chronic beryllium disease. The degree of negative surface charge of the molecule may increase risk of chronic beryllium disease but not sensitization. In the absence of Glu69, HLA-DRB1 alleles may function in beryllium presentation, increasing the risk of chronic beryllium disease. The T-cell response as assessed by the beryllium lymphocyte proliferation test is dependent on central memory T-cells, while Th1 cytokine secretion leading to granulomatous inflammation and chronic beryllium disease is dependent on the activity of effector memory T cells. Polymorphisms in cytokine genes, such as the TGF-beta1 gene, also affect the risk of chronic beryllium disease and more severe disease.

SUMMARY

The current diagnostic criteria for sensitization and chronic beryllium disease rely on the beryllium lymphocyte proliferation test. By understanding the novel immunologic mechanisms and genetic factors associated with sensitization and chronic beryllium disease, we may improve our ability to detect beryllium health effects with new diagnostics, and hopefully refine therapies for disease.