Alpha One Foundation Research
New Irish Study Shows carriers of the Z Alpha-1 Gene who smoke are at Increased Risk of COPD
Researchers from the Alpha One Foundation, the Royal College of Surgeons in Ireland and Harvard University have made a major breakthrough in identifying people who have an increased risk of developing COPD (chronic obstructive pulmonary disease) due to a combination of 1 copy of the Z Alpha-1 gene (MZ carriers) and exposure to cigarette smoke.
The research published in January in the American Journal of Respiratory and Critical Care Medicine, clarifies the risk of COPD linked to alpha-1 antitrypsin deficiency (Alpha-1), an inherited condition affecting almost 250,000 on the island of Ireland.
The research provides the strongest evidence yet that the estimated 1 in 25 people on the island of Ireland, who have inherited a combination of one normal (M) and one abnormal (Z) alpha-1 antitrypsin gene have an increased risk of the debilitating lung condition COPD. Cigarette smoke is the most influential factor in determining whether these individuals who carry this combination of genes (MZ) are at a greater risk of COPD compared to those who have two normal Alpha-1 genes (MM).
Given the very large number of people in Ireland who have the MZ combination of genes (one normal and one abnormal Alpha-1 gene), doctors leading the research stress that it is even more important than ever that people who have been diagnosed with COPD should be tested for Alpha-1. To date, approximately 1,500 people of an estimated 250,000 people on the island of Ireland have been identified with the (MZ) gene combination.
Professor Gerry McElvaney, Professor of Medicine at RCSI, principal investigator and chairman of the Alpha One Foundation Ireland, said "This research signals a major breakthrough in understanding the heightened risk of COPD for people who have the combination of one normal and one abnormal alpha-1 antitrypsin gene. If people know that they have a genetic predisposition to developing COPD, it allows intervention at an earlier age, encourages smoking cessation and prevents a further decline in lung function in a disease that is otherwise preventable. It also provides an opportunity for other family members to get tested for Alpha-1."
"Funded by the Department of Health and Children, the Alpha One Foundation provides a free national screening programme for Alpha-1, the only national screening programme in the world. We strongly urge people to avail of this service, particularly if they have COPD. Also as Alpha-1 is a hereditary disease, we recommend that all first degree family members of individuals with Alpha-1 should be tested. Alpha-1 can be easily diagnosed by a simple blood test. For more information on how to be tested, contact the National Centre for Alpha-1 based at Beaumont Hospital, Dublin." added Professor McElvaney.
Dr. Kevin Molloy, Royal College of Surgeons in Ireland, the lead author of the study said "Alpha-1 is a common inherited condition that is massively under-diagnosed both in Ireland and internationally. As this research has an impact on a large number of people who have the MZ gene combination, the research will greatly increase awareness and diagnosis of Alpha-1. Knowing that you have a genetic predisposition to developing COPD should encourage people to avoid exposure to cigarette smoke if they definitively know they have a higher risk of developing this debilitating lung condition."
"250 individuals from 51 Irish families took part in the research which set out to determine the risk of COPD for people who carry one normal and abnormal Alpha-1 gene. The participants were first degree family members of individuals with the confirmed MZ gene combination. The research used a unique study design which removed a lot of uncertainty from previous attempts to assess the risk of developing COPD for people who have the MZ gene combination." added Dr. Molloy
This piece has featured in a variety of local and national newspapers (for example Irish Times, Irish Independent, and Irish Examiner) and radio stations around the country and was featured on a segment on TV3 news.
Research Breakthrough in Understanding Alpha-1 by Irish Scientists
The Irish Times, the Irish Examiner, the RTE website, the Evening Herald and several other newspapers have this week (January 13th) reported a new discovery by scientists based at the Royal College of Surgeons of Ireland and Beaumont Hospital. These scientists have discovered how a protein, known as alpha-1 antitrypsin (AAT), which is produced by the liver, plays a significant role in reducing inflammation from white blood cells and its overall importance for good health. Their research findings were published in this month's edition of Science Translational Medicine, a prestigious journal that highlights medical advances resulting from scientific research.
The study revealed for the first time how a lack of Alpha-1 protein leads to increased levels of white blood cell proteins, which in turn cause an autoimmune response that produces harmful oxidants and can lead to the development of the lung disease COPD.
The scientists, including RCSI Professor of Medicine Gerry McElvaney, Dr David Bergin and Dr Emer Reeves from the Respiratory Research Division of RCSI's Department of Medicine, also revealed how a treatment, known as augmentation therapy where Alpha-1 protein purified from blood is given intravenously, can ease the autoimmunity leading to the disease. As a result, Prof McElvaney said the research gives new hope for a better quality of life for sufferers of this chronic condition and may also be applied to other autoimmune associated diseases, such as rheumatoid arthritis.
The research was funded by the Medical Research Charities Group/ Health Research Board, the Alpha One Foundation (Ireland) and the Alpha-1 Foundation (USA).
International Collaborative Study To Establish The 1st International (WHO) Standard for Alpha-1 Antitrypsin
Irish scientists based at Beaumont Hospital have been involved in a multicentre study to determine the first ever international standard for alpha-1 antitrypsin. This study will make it easier for research groups and pharmaceutical companies to assess the activity and potency of different preparations of alpha-1 antitrypsin being used as a therapeutic agent.
International Collaborative Study To Establish The 1st International (WHO) Standard For Alpha-1 Antitrypsin
Craig Thelwell1, Peter Rigsby2 and Colin Longstaff1
1Biotherapeutics Group, Haemostasis Section and 2Biostatistics Division, National Institute for Biological Standards and Control, South Mimms, Herts EN6 3QG, England.
An international collaborative study was organised to establish the 1st International Standard (IS) for Alpha-1-Antitrypsin (AAT) as agreed at the Alpha-1 Foundation Workshop in April 2005, Cincinnati, USA. The study involved 15 laboratories from 10 different countries. Laboratories were provided with detailed methods and critical reagents and were asked to measure the potency of four candidate standards (A, 05/150; B, 05/152; C, 05/162 and D, 05/172). In addition laboratories with relevant experience were invited to carry out extended characterisation of the materials, including total protein and antigen content for which an additional reference preparation was provided. Analysis of the data indicated that any of the candidates would be suitable based on potency determination; however candidate C had a slight advantage based on filling data. It is therefore proposed that candidate C (05/162) be adopted as the 1st International Standard for Alpha-1-Antitrypsin with a potency of 243 nmoles (12.4 mg) active AAT per ampoule.
A copy of the full publication can be viewed here.
High Prevalence of Alpha-1 Antitrypsin Deficiency in Ireland
A new study which was presented at the Irish Thoracic Society annual scientific meeting for 2008 held in Belfast in November highlighted the high prevalence of Alpha-1 in Ireland.
The Prevalence of Alpha-1 Antitrypsin Deficiency in Ireland
Authors: T. CARROLL, O. FLOYD, C. O’CONNOR, J. McPARTLIN*, C. TAGGART, R. COSTELLO, S. J. O’NEILL and N. G. McELVANEY
Institution: Department of Respiratory Research, RCSI Education and Research Centre, Beaumont Hospital, Dublin 9, Ireland. *Trinity Biobank, Institute of Molecular Medicine, Trinity Centre, St James's Hospital, Dublin.
Rationale: AAT deficiency is a hereditary autosomal codominant disorder, resulting from mutations in the AAT gene, and classically presents with emphysema and liver disease. The most common phenotype presenting with clinical evidence of AAT deficiency is the Z phenotype, resulting in decreased levels of circulating AAT due to retention of the aberrantly folded protein in the liver. It is unclear whether the carrier status confers increased risk for disease. Demographic studies indicate that AAT deficiency is under-diagnosed and prolonged delays in diagnosis are common. World Health Organisation guidelines advocate targeted detection programmes of patients with COPD and asthma.
Methods: A combination of serum AAT measurement by radial immunodiffusion (RID) or nephelometry, phenotyping by isoelectric focussing (IEF), and genotyping of DNA isolated from dried blood spot samples was used to identify AAT variants.
Results: 2,000 individuals with COPD or asthma attending respiratory outpatient clinics were screened in a national targeted detection programme. A further 1,000 healthy individuals in the general population were also screened for S and Z alleles in a pilot study. The targeted programme identified 43 ZZ, 28 SZ, 7 SS, 195 MZ, 158 MS, and 6 MI individuals, as well as several other rarer phenotypes. The pilot screen of 1,000 healthy individuals identified 98 MS, 46 MZ, 2 SZ, and a single SS case.
Conclusions: The percentage of deficiency alleles detected in the targeted population was higher than anticipated from studies in other populations. The S variant, thought common to the Iberian Peninsula, was detected with unusually high frequency in both targeted and the general population. Several other rarer phenotypes were also detected. Further analysis will reveal whether these phenotypes predispose individuals to lung disease.
Acknowledgements: Alpha One Foundation Ireland, Alpha-1 Foundation U.S., Irish Department of Health and Children, Royal College or Surgeons in Ireland and Talecris Biotherapeutics.
American Thoracic Society Annual Conference 2008
Researchers from the Department of Medicine at RCSI Beaumont Hospital attended the American Thoracic Society Annual Conference 2008 recently to present some of their findings in the area of Alpha-1.
Title: Evidence for the Activation of the Unfolded Protein Response (UPR) in Monocytes from Alpha-1 Antitrypsin Deficient Individuals
Author: T. CARROLL, C. GREENE, C. TAGGART, S. J. O’NEILL and N. G. McELVANEY
Institution: Department of Respiratory Research, RCSI Education and Research Centre, Beaumont Hospital, Dublin 9, Ireland.
Rationale: Alpha-1 antitrypsin (AAT) is a serine protease inhibitor synthesised mainly in the liver and functions as the most important antiprotease in the lung. AAT deficiency (AATD) is a hereditary disorder resulting from mutations in the AAT gene and presents with emphysema in young adults and liver disease in childhood. The most common phenotype presenting with clinical evidence of AATD is the Z phenotype, with decreased levels of circulating AAT due to retention of the aberrantly folded protein in the endoplasmic reticulum (ER) of hepatocytes. AAT is also synthesised in monocytes, and locally produced within the lung by alveolar macrophages and epithelial cells. Having shown previously that ER stress pathways are activated in the liver we sought to elucidate whether misfolded Z AAT can induce ER stress pathways, specifically the UPR, in monocytes from AATD patients.
Methods: Monocytes were isolated from healthy individuals and from AATD ZZ patients. Immunoblotting and quantitative RT-PCR were used to investigate UPR activation.
Results: We show that elements of the UPR, such as the chaperones glucose-regulated protein 78 and 94 (grp78 and grp94), the activated transcription factors 3 and 4 (ATF3 and ATF4) and C/EBP-homologous protein (CHOP), can be activated in monocytes by treatment with Thapsigargin, a known ER stress inducer. To further evaluate UPR activation in vivo we show the transcription factor X-box binding protein-1 (XBP-1) is spliced and activated in ZZ monocytes, and not in monocytes from normal (MM) individuals. In addition, we demonstrate the phosphorylation of eukaryotic initiation factor 2α (eIF2α) in ZZ monocytes, responsible for shutting down global protein synthesis, the first step in the UPR. Finally, we show that the chaperones grp78 and grp94, and components of the ER-associated degradation pathway (ERAD) are induced in ZZ monocytes, and not in MM monocytes.
Conclusions: Monocytes produce AAT, representing another source of misfolded protein. We have shown for the first time that the unfolded protein response is activated in monocytes from AATD patients, probably by misfolded Z AAT. This UPR activation may impair monocyte function and contribute to the pro-inflammatory milieu of the AATD lung.
Acknowledgements: Alpha One Foundation Ireland, Royal College of Surgeons of Ireland, and the Department of Health and Children.
Award to Study Immune Cell Function in Alpha-1 Antitrypsin Deficiency
Researchers in the Department of Medicine at RCSI Beaumont Hospital have been awarded a prestigious European award to study cells of the immune system from people with alpha-1 antitrypsin deficiency (Alpha-1).
European Alpha-1-Antitrypsin Laurell’s Training Award (eALTA) is given to young investigators around Europe who are trying to understand more about Alpha-1 and its causes.
Alpha-1 antitrypsin deficiency (AATD) is a hereditary disorder characterised by lung and liver manifestations. The most common form of AAT deficiency occurs due to the Z mutation, which encodes a glutamine to lysine substitution at position 342 of the AAT protein. This mutation causes the protein to fold aberrantly and accumulate in the endoplasmic reticulum (ER) of hepatocytes. The liver disease is believed to be associated with intracellular accumulation of AAT in the ER leading to ER stress responses whilst the lung disease is due to decreased levels of the AAT antiprotease in the airways, thereby facilitating proteolytic damage. In addition to hepatocytes, AAT is also expressed by other cell types including monocytes and neutrophils. We aim to demonstrate that ER accumulation of Z AAT in monocytes and neutrophils impacts on specific phenotypes and functions of these immune cells, contributing to the overall inflammatory disease process.
The project will run for 12 months from September 2007.
Elucidation of Unfolded Protein Response pathways activated in Lung and Liver Disease associated with Z Alpha-1 Antitrypsin Deficiency
Monday, 24 November 2008 12:41
Health Research Board (HRB)/Medical Research Charities Group (MRCG)
Current treatments for AAT deficiency are based on augmentation therapy with recombinant or plasma-purified AAT and focus almost completely on treating the pulmonary emphysema associated with the disorder. However, the long term efficacy of augmentation therapy has yet to be established, and represents a very expensive therapeutic option. Lung or liver transplantation provides the only effective means of intervention for AAT deficient patients with end-stage lung and liver disease. Unfortunately, while transplantation has been shown to successfully achieve AAT serum conversion, its usefulness as a treatment is confounded by a lack of suitable donors, concomitant immunosuppressive therapy, and high mortality rates. For these reasons it is critically important to develop less invasive therapeutic strategies for the treatment of the lung and liver disease associated with AATD. Conformational diseases are associated with rogue protein accumulation in tissues and cellular compartments. AAT deficiency is one such genetic disease characterised by the accumulation of incorrectly folded AAT in liver cells. The accumulation of mutant Z AAT protein within the cell switches on several protective mechanisms, including the unfolded protein response (UPR). With prolonged activation the UPR becomes harmful to the cell, causes inflammation and ultimately cell death. This is responsible for the cirrhosis observed in the AATD-associated liver disease, but may also be partly responsible for the emphysema seen in AATD-associated lung disease. This may explain why augmentation therapy has yet to be proven clinically effective, and why AAT deficient patients who have received liver transplants still exhibit local inflammation in the lung. We have previously identified intracellular events involved in the molecular pathogenesis of AATD-induced liver disease using an in vitro model system of Z AAT accumulation in liver cells. We will demonstrate that abnormalities in Z AAT-induced liver disease can also be present in Z AAT-induced lung disease. We aim to highlight the crucial involvement of the UPR in Z AAT-associated lung and liver disease. We will show that Z AAT activates the UPR, knocking off protein synthesis, turning on a plethora of UPR-related genes, and activating machinery which degrades the misfolded Z AAT. We will evaluate the role of UPR mediators in vivo in lung and liver biopsies from individuals with AATD compared to healthy normal individuals. This discovery-driven project proposal will lead to a greater understanding of AATD, generate several hypotheses, and allow us to identify novel therapeutic avenues for the treatment of AATD-related lung and liver disease.
Duration: 3 years from January 2007
Identification and characterisation of novel pro-inflammatory proteases that excerbate lung disease associated with Z alpha-1 antitrypsin deficiency
Monday, 24 November 2008 12:25
DA Bergin, Greene CM, Taggart CC, O’Neill SJ and McElvaney NG. Activation of the EGFR by Human Neutrophil Elastase. Royal College of Surgeons in Ireland Research Day, RCSI St. Stephen’s Green, Dublin, April 2006. DA Bergin, CM Greene, CC Taggart, EE Sterchi, SJ O’Neill, NG McElvaney.
Clarification of the Risk of COPD in Alpha-1 antitrypsin (MZ) Individuals
Monday, 24 November 2008 12:20
Funding Body: Alpha-1 Foundation (USA)
Project Description: This clinical research study, to clarify the risk of COPD in MZ individuals, commenced in July 2007 and is supervised by Professor Gerry McElvaney, Department of Medicine RCSI, Smurfit Building, Beaumont Hospital, Dublin 9, Ireland.
The purpose of this study is to obtain information about individuals (and their family members) that are carriers of alpha-1 antitrypsin (AAT) deficiency. Acquisition of an abnormal alpha-1 gene from each parent leads to severe deficiency in alpha-1 protein levels which may result in serious lung disease in adults and/or liver disease in infants, children and adults. If an individual inherits an abnormal alpha-1 gene from only one parent, they are a carrier and may be predisposed to developing lung disease. The main objective of this study is to determine whether carriers of alpha-1 antitrypsin deficiency are at an increased risk of developing lung disease. We aim to identify subtle changes in lung function especially in close family members that may allow earlier intervention and treatment. We also aim to investigate whether there are any environmental factors that interact with the abnormal alpha-1 gene that predisposes some but not others to serious lung disease. If identified correctly, such environmental factors may then be avoided thus preventing the development of serious lung disease in carriers of alpha-1 antitrypsin deficiency. Our aim is to enroll 400 parents and siblings of 100 alpha-1 antitrypsin carriers (PiMZ) with diagnosed GOLD Stage 3 or 4 COPD into this study. The inclusion criteria for PiMZ carriers are as follows:
- Age >30
- GOLD Stage 3 or 4 COPD (post-bronchodilator FEV1 <50% predicted; FEV1/FVC ratio 0.7)
- Confirmed PiMZ genotype
- No other lung diseases that would affect pulmonary function testing (PFT)
The exclusion criteria for relatives of the above PiMZ carriers are as follows:
- Any interstitial lung diseases
- Genotypes other than PiMM or PiMZ
- Non-biological siblings of the PiMZ COPD proband
Each individual will perform a lung function test (using a portable spirometer), complete a detailed questionnaire (respiratory and liver questions, family history, smoking history etc) and provide blood samples to confirm their carrier status and allow DNA extraction. In the last year, we have recruited 125 individuals into the study from 25 families. Our preliminary results have shown approximately equal numbers of MZ carriers and MM individuals within each family. Our goal is to include as many siblings and parents from each family as possible to participate in this ground-breaking clinical research study. We will determine whether the PiMZ carrier status is associated with an increased risk of COPD and whether cigarette smoking confers an increased risk of COPD in carriers of alpha-1 antitrypsin deficiency.
If you are an MZ carrier, fulfill the above criteria and are interested in partaking in this clinical research study, please contact:
Alpha-1 Augmentation Therapy Clinical Trial
Monday, 24 November 2008 12:08
This clinical trial is being conducted in Beaumont Hospital by Professor McElvaney and his team. This is a placebo-controlled, double-blinded, multicentre phase III / IV study to compare the efficacy and safety of the drug Zemaira ® in patients with emphysema due to alpha-1 antitrypsin deficiency. The duration for each patient is 2 years.
We have recruited 16 patients so far and they are all at various stages in the trial. The trial involves having weekly intravenous infusions of Zemaira®, an alpha-1 antitrypsin product or a placebo (which is a mock treatment that looks like the real thing but has none of the activity).
As the study is double-blinded, neither the participating patients nor our study staff knows which therapy has been assigned to them. There is an equal chance of receiving either treatment. As of March 2008 we have had 6 patients graduate onto the extension phase of the study. This is where each patient receives Zemaira for up to another two years. The infusions are given either in Beaumont Hospital or in the patient’s own home and take on average 20 minutes. Every three months patients are required to attend Beaumont Hospital so that routine tests can be carried out. These include: Monitoring of vital signs, i.e. blood pressure, weight etc.
- Blood tests.
- Pulmonary Function tests.
- Physical Examination by physician.
- Cotinine test (urine test that detects nicotine) is required.
At certain visits a Quality of Life questionnaire and CT scan are performed. These help to investigate the effect of Zemaira® on the development and progression of emphysema within the patients. The main inclusion criteria for all patients that enter onto the study are: · Diagnosis of alpha-1 antitrypsin deficiency (ZZ phenotype).
- Non smokers or Ex-Smokers who have stopped at least 6 months prior to screening.
- Age range of 18 – 65 years of age, male and female.
- Emphysema with an FEV1 of 35-70% predicted range.
As with other alpha-1 therapies, Zemaira® may not be appropriate for the following adults:
- Individuals with a known hypersensitivity and/or history of anaphylaxis or severe systemic reaction to alpha-1 antitrypsin products or their components.
- Individuals with selective IgA deficiencies who have known antibodies against IgA. This is due to Zemaira® being derived from human plasma.
All patients however will be assessed on an individual basis. In previous clinical studies, Zemaira® has been shown to be generally well tolerated and provides patients with half or less the infusion time of other available alpha-1 augmentation therapies. If you would like any further information on Zemaira® or you are interested in taking part in the trial please feel free to contact:
Tel: 01 8093864/01 8093876
Research Nurse, Study Co-Ordinator
Pilot Alpha-1 Antitrypsin Deficiency Screening Programme to determine the Prevalence of Alpha-1 Antitrypsin Deficiency in Ireland
We recently undertook a research project to identify the incidence of AATD in a representative sample of the general population of Ireland. This involved screening 1000 anonymised DNA samples for the presence of the S and Z mutations and was undertaken in collaboration with Dr. Joe McPartlin of the Trinity College Biobank. The gene frequencies revealed for both the S and Z mutation were higher than anticipated based on studies in other European populations.
For the purpose of this study the randomised nationally-based buccal swab collection from the Trinity Biobank was investigated. Ethical approval for the collection was granted by the joint Hospital Ethics Committee of Tallaght and St. James’s Hospitals. The confidentiality of the participant’s data and samples was respected and ensured by irreversible anonymisation. DNA was extracted from buccal swabs according to the Biobank standard protocols. AAT deficient individuals were identified through separate genotyping assays for the S and Z mutations using Real-Time PCR technology and melt curve analysis on a Roche Lightcycler. A Z genotyping assay was performed on 1095 DNA samples provided by the Biobank. This revealed 46 MZ or carrier individuals in the population. The frequency of the Z gene in this population was, therefore, 0.022. An S assay, carried out on 960 biobank samples, revealed 98 MS carriers and 1 SS (homozygote) individual. The frequency of the S gene in this population was, therefore, 0.053. In total, between the two assays, 3 AAT deficient individuals were identified, constituting 2 SZ and 1 SS genotype. A total of 140 AATD carriers were detected, constituting 46 MZ and 98 MS individuals.
|Deficiency Phenotype||No. Detected/No. Screened|
Table 1. Number of Deficiency Phenotypes Detected in Population Screened
The percentage of deficiency alleles detected was higher than anticipated from studies in other populations. The allele frequencies for S and Z in Ireland were previously estimated at between 0.02-0.04 and 0.005-0.015 (Luisetti et al, Thorax 2004). The S variant, thought common to the Iberian Peninsula, was detected with unusually high frequency in the Irish population. Our pilot study shows S and Z alleles occur at frequencies of 0.053 and 0.022 respectively in the Irish population. As the random sample was from the 32 counties, and extrapolating from a population of 6 million on the island of Ireland this would suggest there are approximately 2,900 ZZ and 14,000 SZ AAT deficient individuals and over 200,000 MZ carriers on the island of Ireland. Compared to the gene frequencies in our targeted detection programme the Z mutation would appear to be much more clinically significant with a higher penetrance than S in the two populations we have evaluated. The prospect that alpha-1 antitrypsin deficiency is much more common in Ireland than previously thought will help highlight the fact that all COPD, non-responsive asthma and cryptogenic liver disease patients should be tested for AATD. Increased awareness and understanding of AATD is vital to prevent the continuing under-diagnosis of this condition. Early diagnosis of AATD, with appropriate medical follow-up and lifestyle changes, can prevent, or at least postpone, AATD complications.
Adoption of New Sebia Phenotyping Method:
In the last year we have acquired a new piece of equipment for the Targeted Detection Programme. This has allowed us to implement a more accurate method of phenotyping. We can now identify the different alpha-1 antitrypsin phenotypes with an increased sensitivity of detection. The Sebia Hydragel 18 AAT Isofocusing kit is designed for the qualitative detection and identification of the different phenotypes of alpha-1 antitrypsin (AAT) in the electrophoretic patterns of human sera. The procedure includes isoelectricfocusing on agarose gel, performed on the semi-automatic HYDRASYS system, followed by immunofixation with anti-alpha-1 antitrypsin antiserum. The assay is carried out in two stages. Firstly, isoelectrofocusing on agarose gel is used to fractionate the proteins in the serum samples. This is followed by immunofixation with enzyme (peroxidase)-labelled anti-alpha-1 antitrypsin antiserum to identify the various phenotypes of alpha-1 antitrypsin.
To summarise, we have found this new phenotyping method to be highly specific, rapid and simple to perform. It represents a more accurate method of screening for alpha-1 antitrypsin deficiency and improves the identification of not only the most common but also various rare AAT phenotypes.
National Alpha-1 Antitrypsin Deficiency Targeted Detection Programme
Alpha-1 antitrypsin (AAT) is an antiprotease produced chiefly by the liver. Alpha-1 antitrypsin deficiency (AATD) is a genetic disorder characterised by low serum levels of AAT and is associated with lung and liver disease.
In May 2004 a national targeted detection programme for alpha-1 antitrypsin deficiency was established in Beaumont Hospital. Funded directly by the Irish Government's Department of Health, the screening programme provides free testing to patients with chronic obstructive pulmonary disease (COPD), non-responsive asthma, cryptogenic liver disease and to relatives of AATD patients.
A range of methods are used to diagnose AATD including phenotyping by isoelectric focussing and genotyping by RT-PCR. Upon diagnosis the Alpha One Foundation also provides a range of ancillary services to patients including counselling, expert advice, information packs and leaflets, and opportunities to enrol in clinical trials and to join the Alpha-1 patient support group. Alpha-1 antitrypsin (AAT) is a 52kDa glycosylated protein. Produced in the liver and secreted into the blood, AAT diffuses into the lungs where it functions as an antiprotease. Antiproteases regulate and inactivate protein-splitting enzymes such as neutrophil elastase, an enzyme capable of destroying alveolar wall connective tissue. AAT is the most abundant antiprotease in the lung and therefore plays a major role in maintaining a healthy, functioning lung. Alpha-1 antitrypsin deficiency (AATD) is a hereditary autosomal codominant disorder caused by mutations in the AAT gene located on chromosome 14. Genetic variants of the AAT gene are characterised by their electrophoretic mobilities as medium (M), slow (S) or very slow (Z). The most common variants associated with disease are the S (Glu264Val) and Z (Glu342Lys) mutations, caused by a single amino acid replacement of glutamic acid at positions 264 and 342 of the polypeptide respectively. Both mutations result in decreased levels of circulating AAT due to retention of the aberrantly folded protein in the liver, and classically result in liver disease in children, and early onset emphysema or occasionally liver disease in adults. Moreover, the small amount of AAT that reaches the lung in AATD patients is inactivated by cigarette smoke. Smoking is the single biggest risk factor for the development of emphysema in AATD patients, and individuals with AATD who smoke develop severe, early-onset emphysema. The most commonly observed genotypes are MM (normal), MS, MZ (heterozygotes), SZ (compound heterozygote) and SS or ZZ (homozygotes). It is unclear, as yet, whether the carrier status (MS or MZ) confers an increased risk of disease.
AATD is under-diagnosed with prolonged delays in diagnosis common. In addition, the majority of AATD individuals with emphysema are misdiagnosed as COPD patients. A recent US study showed it takes an average 5.6 years from the time symptoms first appear to accurate diagnosis. Increased awareness and understanding of AATD is therefore vital to prevent the continuing under-diagnosis of this condition. To this end, we have launched a national registry of AATD patients and a website (www.alpha1.ie) providing a resource for doctors, patients, and the general public. All patients diagnosed through our targeted detection programme are offered a variety of services including counselling, expert advice, information packs/leaflets, and opportunities to enrol in clinical trials and to join the Alpha-1 patient support group. Based on studies in other European countries it is estimated that 1,200 Irish citizens have AATD and up to 200,000 Irish citizens are carriers, yet only 110 individuals with AATD have been identified in Ireland to date. A research project recently undertaken in our laboratory screened 1,000 anonymised DNA samples provided by the Trinity College Biobank for the presence of the S and Z mutations. This investigation of a sample Irish population revealed a gene frequency of 0.05 for the S mutation and 0.022 for the Z mutation, which is higher than anticipated based on studies in other European populations.
|Phenotype|| AAT (%) || What does it mean? |
|Normal ||MM||100||No altered AAT gene so no risk of disease|
|Carrier ||MS||80||Carries altered AAT gene but evidence suggests no increased risk of disease|
|MZ||60||Carries altered AAT gene & may develop disease (particularly if smoking)|
|Mild Deficiency ||SS||60||Carries two altered AAT genes but evidence suggests no increased risk of disease|
|Severe Deficiency ||SZ/ZZ||10 - 30||Carries two altered AAT genes and will probably develop disease (particularly if smoking)|
Table 1: Explanation of the various AAT phenotypes and their clinical consequences.
In summary, AATD is more prevalent in Ireland than previously thought, even allowing for the targeted, symptomatic population investigated in this programme. The advantages of early and accurate diagnosis of AATD are manifold and include (1) closer observation and management of affected individuals, especially regarding pulmonary and liver health, (2) family member testing, at least some of whom may have lung or liver complications, (3) aggressive smoking cessation efforts, which have been associated with lower rates of smoking among AAT-deficient individuals, and (4) consideration of occupational hazards and environment as exposures to some occupational dusts and vapours can accelerate pulmonary decline. Once identified, AATD patients have the opportunity to enrol in clinical trials currently taking place in Beaumont Hospital, such as the AAT augmentation therapy clinical trial for ZZ individuals, and the MZ family study which is attempting to fully clarify the risk of COPD in MZ individuals. To conclude, the importance of an early diagnosis of AATD cannot be over-emphasised as the resulting appropriate medical follow-up and lifestyle changes can help prevent or at least postpone the development of AATD-related lung and liver disease.