Expression of the alpha-1-antitrypsin gene in mononuclear phagocytes of normal and alpha-1-antitrypsin-deficient individuals

Synthesis of stress proteins is increased in individuals with homozygous PiZZ alpha 1-antitrypsin deficiency and liver disease

Individuals who are homozygous for the protease inhibitor phenotype Z (PiZ) genetic variant of alpha 1-antitrypsin (alpha 1-AT) have reduced plasma concentrations of alpha 1-AT, and are susceptible to premature development of pulmonary emphysema. A subset of this population develops chronic liver disease. The reduction in plasma concentrations of alpha 1-AT results from a selective defect in secretion as the abnormal PiZ alpha 1-AT protein accumulates within the cell. It has recently been shown in several experimental systems that the heat shock/stress response, a response characterized by the synthesis of a family of highly evolutionarily conserved proteins during thermal or chemical stress, may also be activated by the presence of abnormal proteins within the cell. Therefore, we predicted that the heat shock/stress response would be induced in the absence of thermal or chemical stress in alpha 1-AT-synthesizing cells of PiZZ individuals. In the following study, however, we show that net synthesis of proteins in the heat shock/stress gene family (SP90, SP70, ubiquitin) is increased only in a subset of the population, PiZZ individuals with liver disease. It is not significantly increased in PiZZ individuals with emphysema or in those without apparent tissue injury. Net synthesis of stress proteins is not increased in individuals with another variant of the alpha 1-AT gene (PiS alpha 1-AT) and is not increased in individuals with severe liver disease but a normal alpha 1-AT haplotype (PiM alpha 1-AT). These results demonstrate that the synthesis of stress proteins is increased in a subset of individuals with homozygous PiZZ alpha 1-AT deficiency, those also having liver disease.

Ribonuclease A cleavage combined with the polymerase chain reaction for detection of the Z mutation of the alpha-1-antitrypsin gene

Homozygous inheritance of the Z mutation (exon V, Glu342GAG----Lys342AAG), the most common cause of alpha-1-antitrypsin (alpha 1AT) deficiency, is associated with a high risk for emphysema and liver disease. This study presents a rapid and accurate approach to definitive genotypic diagnosis of the Z homozygous state using a combination of polymerase chain reaction amplification of exon V of the alpha 1AT gene and ribonuclease cleavage of an exon V-specific antisense RNA probe. Taking advantage of the concept that ribonuclease A will cleave at points of mismatch of RNA-DNA hybrids, a 0.79 kb antisense RNA probe was designed with complementarity to the sense strand of exon V of the alpha 1AT gene (the site of the Z mutation) along with small regions of the 5' and 3' flanking sequences. After amplification of exon V of the alpha 1AT gene from genomic DNA by the polymerase chain reaction, the amplified DNA was analyzed by hybridization to a 32P-labeled exon V antisense RNA probe followed by digestion with RNase A. Any substitution mutations resulting in DNA-RNA mismatch were detected by evaluation with polyacrylamide gel electrophoresis under denaturing conditions followed by autoradiography (expected fragment lengths: 0.33 kb when the exon V probe hybridized to the normal amplified genomic DNA, 0.25 and 0.08 kb fragments when the exon V probe hybridized to the amplified genomic DNA with the Z mutation). Double-blinded evaluation of genomic DNA of 36 individuals (phenotypes MM n = 14, MZ n = 5, ZZ n = 16, ZNull n = 1; included among the "M" alleles were representatives of all the major normal M alleles) demonstrated definitive diagnosis of the Z mutation with absolute specificity for all 36 specimens, i.e., ZZ homozygotes, MZ heterozygotes, and normals were all detected accurately. This approach should be useful not only for screening for the Z mutation of the alpha 1AT gene, but by this type of analysis, mutational alterations of the alpha 1AT gene can be screened for without prior knowledge of the sequence changes and without complex cloning and sequencing methods.

Expression of HLA class II genes in alveolar macrophages of patients with sarcoidosis

Sarcoidosis is characterized by the accumulation of activated helper/inducer T-cells and macrophages at sites of disease. The accumulation of these T-cells may be related to the ability of sarcoid alveolar macrophages to present antigen and stimulate lymphocyte proliferation in an exaggerated fashion. In the context that HLA Class II gene (HLA-DR, DQ, and DP) expression is essential to the interaction of lymphocytes with antigen-presenting cells such as macrophages, we have evaluated the hypothesis that the expression of Class II genes may be up-regulated in sarcoid alveolar macrophages. Northern blot and dot blot analysis with 32P-labeled cDNA probes for HLA-DR, DQ, and DP genes revealed that both normal and sarcoid alveolar macrophages contain Class II mRNA transcripts, but that the levels in sarcoid and normal alveolar macrophages are similar (p greater than 0.3, all comparisons). Furthermore, evaluation of surface expression of Class II molecules with monoclonal antibodies and flow cytometry analysis demonstrated that alveolar macrophages of both patients with sarcoidosis and normal subjects express all three Class II molecules, DR, DQ, and DP, but there were no significant differences between sarcoid patients and normal subjects in the proportions of macrophages expressing these surface molecules. However, there was a significantly higher surface density of Class II molecules on sarcoid alveolar macrophages (p less than 0.05, all comparisons sarcoid to normal).(ABSTRACT TRUNCATED AT 250 WORDS)

Alpha 1-antitrypsin deficiency caused by the alpha 1-antitrypsin Nullmattawa gene. An insertion mutation rendering the alpha 1-antitrypsin gene incapable of producing alpha 1-antitrypsin

alpha 1-Antitrypsin (alpha 1AT) deficiency is a hereditary disorder associated with reduced serum alpha 1AT levels and the development of pulmonary emphysema. An alpha 1AT gene is defined as "Null" when no alpha 1AT in serum is attributed to that alpha 1AT gene. Although all alpha 1AT Null genes have identical phenotypic consequences (i.e. no detectable alpha 1AT in the serum), different genotypic mechanisms can cause the Null state. This study defines the molecular basis for the alpha 1AT gene Nullmattawa, identified and cloned from genomic DNA of an individual with the Null-Null phenotype and emphysema resulting from the heterozygous inheritance of the Nullmattawa and Nullbellingham genes. Sequencing of exons Ic-V and all exon-intron junctions of the Nullmattawa gene demonstrated it was identical to the common normal M1(Val213) alpha 1AT gene except for the insertion of a single nucleotide within the coding region of exon V, causing a 3' frameshift with generation of a premature stop signal. Family analysis using oligonucleotide probes specific for the Nullmattawa sequence demonstrated the gene was inherited in an autosomal fashion. Examination of blood monocytes demonstrated that a normal-sized, 1.8-kb alpha 1AT mRNA transcript is associated with the Nullmattawa gene and in vitro translation of mRNA with the Nullmattawa mutation showed it translated at a normal rate but produced a truncated alpha 1AT protein. Additionally, retroviral transfer of the alpha 1AT Nullmattawa cDNA to murine fibroblasts demonstrated no detectable intracellular or secreted alpha 1AT, despite the presence of alpha 1AT Nullmattawa mRNA transcripts. These findings are consistent with the concept that the molecular pathophysiology of Nullmattawa is likely manifested at a posttranslational level. The identification of the Nullmattawa gene supports the concept that Null alpha 1AT alleles represent a heterogenous group in which very different mechanisms cause the identical phenotypic state.

Alpha 1-antitrypsin: structure, function and molecular biology of the gene

Alpha 1-antitrypsin (AAT) deficiency is one of the commonest inherited disorders in white Caucasians. This association has provided major insights into the pathogenesis of chronic lung disease. The three dimensional structure of the protein and the structure of the gene have been determined. Some of the signals required for regulation of expression and tissue-specificity have been defined. Genetic manipulation of active site residues may provide a new generation of biological compounds with potential therapeutic applications.

Repair of the secretion defect in the Z form of alpha 1-antitrypsin by addition of a second mutation

Homozygous inheritance of the Z-type mutant form of the alpha 1-antitrypsin (alpha 1AT) gene results in the most common form of alpha 1AT deficiency, a human hereditary disease associated with a high risk for the development of emphysema and an increased incidence of neonatal hepatitis. The alpha 1AT-synthesizing cells of individuals with the Z gene have normal alpha 1AT messenger RNA levels, but alpha 1AT secretion is markedly reduced secondary to accumulation of newly synthesized alpha 1AT in the rough endoplasmic reticulum. Crystallographic analysis of alpha 1AT predicts that in normal alpha 1AT, a negatively charged Glu342 is adjacent to positively charged Lys290. Thus the Glu342----Lys342 Z mutation caused the loss of a normal salt bridge, resulting in the intracellular aggregation of the Z molecule. The prediction was made that a second mutation in the alpha 1AT genet that changed the positively charged Lys290 to a negatively charged Glu290 would correct the secretion defect. When the second mutation was added to the Z-type complementary DNA, the resulting gene directed the synthesis and secretion of amounts of alpha 1AT similar to that directed by the normal alpha 1AT complementary DNA in an in vitro eukaryotic expression system. This suggests the possibility that a human hereditary disease can be corrected by inserting an additional mutation in the same gene.

Multiple tissues express alpha 1-antitrypsin in transgenic mice and man

Hepatocytes are considered to be the predominant source of alpha 1-antitrypsin (AAT), the major antiprotease in human plasma. The development of emphysema in the hereditary PiZ AAT deficiency state suggests that inhibition of leukocyte elastase in the lung is a major function of this protein. In addition, patients with AAT deficiency are at increased risk for developing cholestasis in infancy and chronic liver disease as adults. The mechanism for hepatic cell injury, however, is not understood. Transgenic mice that express the normal human AAT gene demonstrate abundant AAT in hepatocytes and specific cell types of numerous nonhepatic tissues. Immunoperoxidase techniques have previously disclosed AAT in many of the cell types seen in transgenic mice; however, the issue of local synthesis vs. endocytosis in these cell types has remained unresolved. In this study, AAT mRNA was seen in a variety of tissues in the transgenic mouse. Immunoelectron microscopy of renal tubular and small intestinal epithelial cells in the transgenic mice demonstrated AAT within the cisternae of the rough endoplasmic reticulum, as in hepatocytes. These findings support the possibility of local synthesis in the various cell types. The results suggest that in addition to maintaining tissue integrity in the lung, the protease/antiprotease balance may have physiological functions in other organs as well.

Molecular basis of alpha-1-antitrypsin deficiency

Alpha-1-antitrypsin (A1AT) deficiency is an autosomal hereditary disorder associated with a major reduction in serum A1AT levels. Clinically, A1AT deficiency is associated with emphysema in adults and, less commonly, liver disease in neonates. A1AT is a 52-kDa, 394-amino acid, single-chain glycoprotein normally present in serum at 150 to 350 mg/dl. The A1AT gene, composed of seven exons dispersed over 12 kb of chromosomal segment 14q31-32.3, is expressed in hepatocytes and mononuclear phagocytes. The A1AT protein, a member of the class of protease inhibitor proteins known as serpins (serine protease inhibitors), is a globular molecule composed of nine alpha-helices and three beta-pleated sheets. The major function of A1AT is to inhibit neutrophil elastase; A1AT does so through an active site centered around Met358 contained within an external stressed loop on the surface of the molecule. A1AT is a highly pleomorphic protein with greater than 75 variants determined at the protein and/or gene level. These variants can be categorized into four groups according to their serum A1AT level and function: normal, deficient, dysfunctional, and absent. There are two important salt bridges within the A1AT molecule (Glu342-Lys290; Glu263-Lys387); a mutation in the A1AT gene causing disruption of either salt bridge causes distinct molecular pathology resulting in reduced serum A1AT levels. Clinically relevant variants can be distinguished by a combination of isoelectric focusing of serum, restriction fragment length analysis of genomic DNA, oligonucleotide probes, and direct sequencing of the variant A1AT genes.

Alpha-1-antitrypsin augmentation therapy for alpha-1-antitrypsin deficiency

Alpha-1-antitrypsin (A1AT) deficiency is a genetic disorder characterized by low serum levels of A1AT and a high risk for the development of emphysema. A1AT is the principal inhibitor of neutrophil elastase, such that a deficiency of A1AT results in insufficient anti-elastase protection in the lower respiratory tract, thus allowing neutrophil elastase to destroy alveolar structures. The goal of A1AT augmentation therapy in A1AT deficiency is to raise lung A1AT levels and anti-neutrophil elastase capacity to levels that will provide adequate protection against neutrophil elastase, thereby preventing the lung from further elastase-mediated degradation. Studies with intravenous administration of human A1AT (60 mg/kg at weekly intervals) demonstrate that serum A1AT levels increased from an average 33 +/- 8 mg/dl pre-infusion to a steady-state trough level of 117 +/- 4 mg/dl, well above the projected threshold protective serum level of A1AT. The infused A1AT diffused into the lung and significantly augmented the epithelial lining fluid A1AT levels, rising from an average 0.44 +/- 0.16 microM (pre-infusion) to 2.62 +/- 1.29 microM at the nadir level just prior to the next infusion. Of critical importance is the fact that the A1AT that diffused into the lung was active as an inhibitor or neutrophil elastase, resulting in significant augmentation of epithelial lining fluid anti-neutrophil elastase capacity and normalization of the lung anti-elastase protection. In the over 800 weekly infusions administered, no significant adverse reactions have occurred. These findings demonstrate that long-term augmentation therapy with weekly infusions of A1AT is a rational, safe, and biochemically effective therapy for A1AT deficiency.

Elastase regulates the synthesis of its inhibitor, alpha 1-proteinase inhibitor, and exaggerates the defect in homozygous PiZZ alpha 1 PI deficiency

The net balance of neutrophil elastase, an enzyme that degrades many components of the extracellular matrix, and its inhibitor, alpha-1-proteinase inhibitor (alpha 1 PI), is thought to be a critical determinant in the development of destructive lung disease, especially in individuals with homozygous alpha 1 PI deficiency. Synthesis and secretion of alpha 1 PI has been recently demonstrated in cells of mononuclear phagocyte lineage, including peripheral blood monocytes and tissue macrophages. In this study we show that alpha 1 PI gene expression in human monocytes and bronchoalveolar macrophages is affected by a novel mechanism, whereby elastase directly regulates the synthesis of its inhibitor. In nanomolar concentrations, neutrophil or pancreatic elastase mediates a dose- and time-dependent increase in steady state levels of alpha 1 PI mRNA and in the rate of synthesis of alpha 1 PI in human monocytes and bronchoalveolar macrophages. Antisera to neutrophil elastase or pretreatment of elastase with the serine proteinase inhibitor diisopropylfluorophosphate abrogates the effect of elastase on alpha 1 PI expression. Elastase also stimulates the synthesis of alpha 1 PI in monocytes from homozygous PiZZ alpha 1 PI-deficient individuals, but has no effect on the rate of secretion; hence, the enzyme mediates an effect on alpha 1 PI that increases the intracellular accumulation of inhibitor and exaggerates the intrinsic defect in secretion of alpha 1 PI that characterizes the homozygous PiZZ alpha 1 PI deficiency.

Emphysema associated with complete absence of alpha 1- antitrypsin in serum and the homozygous inheritance [corrected] of a stop codon in an alpha 1-antitrypsin-coding exon

Homozygous inheritance of the null bellingham alpha 1-antitrypsin (alpha 1AT) gene is associated with early-onset emphysema, resulting from the lack of alpha 1AT to protect the lung from neutrophil elastase. Cloning and sequencing of the null bellingham gene demonstrated that the promoter region, coding exons, and all exon-intron junctions were normal except for a single base substitution in exon III, causing the normal lys217 (AAG) to become a stop codon (TAG). Evaluation of genomic DNA of family members by using oligonucleotides directed toward this region demonstrated that the index case had inherited this mutation in a homozygous fashion. Although the consequences to the individual (i.e., emphysema) are identical to those associated with the common homozygous Z mutation, the homozygous null bellingham form of alpha 1AT deficiency has a very different genetic basis.

Modulation of fibronectin gene expression in human mononuclear phagocytes

Under some conditions, mononuclear phagocytes spontaneously synthesize and release fibronectin, an extracellular matrix glycoprotein with versatile effects on cell-matrix interactions. To gain insight into the processes that modulate the level of fibronectin secretion by these cells, we used monocytes, in vitro matured monocytes and alveolar macrophages as models to compare fibronectin mRNA levels and fibronectin secretion in a variety of circumstances. Using Northern analysis and dot-blot analysis with a 32P-labeled human fibronectin cDNA probe, we evaluated steady-state mRNA levels and a human fibronectin-specific ELISA was used to evaluate fibronectin secretion. In all cases the amounts of fibronectin secreted paralleled fibronectin mRNA levels. Specifically (a) when fibronectin mRNA was undetectable, as in the case of normal blood monocytes, no fibronectin was secreted, but whenever fibronectin mRNA was present, as in normal alveolar macrophages, fibronectin was secreted by the cells; (b) as monocytes matured into macrophages in vitro, the cells began to express fibronectin mRNA and the cells secreted fibronectin; (c) when alveolar macrophages were activated with surface stimuli such as lipopolysaccharide (LPS) or immune complexes, fibronectin mRNA levels decreased and in parallel, the cells secreted less fibronectin; (d) in idiopathic pulmonary fibrosis (IPF), alveolar macrophages contained severalfold more fibronectin mRNA transcripts that normal and the cells spontaneously secreted severalfold more fibronectin than normal; and (e) when IPF alveolar macrophages were placed in culture the fibronectin mRNA levels in the cells decreased with time, and concurrently the amounts of fibronectin produced per unit time continually decreased. The observation of a strict concordance of fibronectin mRNA levels and fibronectin release by mononuclear phagocytes suggests that, at least in many circumstances, fibronectin secretion by mononuclear phagocytes is controlled by steady-state levels of fibronectin mRNA.

Z-type alpha 1-antitrypsin is less competent than M1-type alpha 1-antitrypsin as an inhibitor of neutrophil elastase

Alpha 1-antitrypsin (alpha 1AT) deficiency resulting from homozygous inheritance of the Z-type alpha 1AT gene is associated with serum alpha 1AT levels of less than 50 mg/dl and the development of emphysema in the third to fourth decades. Despite the overwhelming evidence that the emphysema of PiZZ individuals develops because of a "deficiency" of alpha 1AT and hence an insufficient antineutrophil elastase defense of the lung, epidemiologic evidence has shown that levels of alpha 1AT of only 80 mg/dl protect the lung from an increased risk of emphysema. With this background, we hypothesized that homozygous inheritance of the Z-type may confer an added risk beyond a simple deficiency of alpha 1AT by virtue of an inability of the Z-type alpha 1AT molecule to inhibit neutrophil elastase as effectively as the common M1-type molecule. To evaluate this hypothesis, the functional status of alpha 1AT from PiZZ individuals (n = 10) was compared with that of alpha 1AT from PiM1M1 individuals (n = 7) for its ability to inhibit neutrophil elastase (percent inhibition) as well as its association rate constant for neutrophil elastase (K association). Plasma alpha 1AT concentration, measured by radial immunodiffusion, was 34 +/- 1 mg/dl in PiZZ patients vs. 237 +/- 14 mg/dl for PiM1M1 plasma, a sevenfold difference. When titrated against neutrophil elastase, the present inhibition of PiZZ plasma was significantly less than Pi M1M1 plasma (ZZ 78 +/- 1% vs. M1M1 95 +/- 1%, P less than 0.001) as was purified Z type alpha 1AT (ZZ, 63 +/- 2% vs. M1M1 86 +/- 2%, P less than 0.001). Sodium dodecyl sulfate (SDS) gel comparisons of the complexes formed with M1-type alpha 1AT and Z-type alpha 1AT with elastase demonstrated the Z alpha 1AT-elastase complexes were less stable than the M1 alpha 1AT-elastase complexes, thus releasing some of the enzyme to continue to function as a protease. Consistent with these observations, the K association of purified Z-type alpha 1AT for neutrophil elastase was lower than that of M1-type alpha 1AT (ZZ 4.5 +/- 0.3 X 10(6) M-1s-1 vs. M1M1 9.7 +/- 0.4 X 10(6) M-1s-1, P less than 0.001), suggesting that for the population of alpha 1AT molecules, the active Z-type molecules take more than twice as long as the active M1-type alpha 1AT to inhibit neutrophil elastase. Consequently, not only is there less alpha1AT in PiZZ individuals, but the population of Z-type alpha1AT molecules is less competent as an inhibitor of neutrophil elastase than M1-type alpha1AT molecules. This combination of defects suggests that PiZZ individuals have far less functional antielastase protection than suggested by the reduced concentrations of alpha1AT alone, further explaining their profound risk for development of emphysema.

Lipopolysaccharide modulates the expression of alpha 1 proteinase inhibitor and other serine proteinase inhibitors in human monocytes and macrophages

alpha 1 Proteinase inhibitor (PI) is the principle inhibitor of neutrophil elastase, an enzyme that degrades many components of the extracellular matrix. Expression and regulation of alpha 1 PI, therefore, affects the delicate balance of elastase and antielastase, which is critical to turnover of connective tissue during homeostasis, tissue injury, and repair. In this study we show that expression of alpha 1 PI in human monocytes and macrophages is regulated during activation by LPS. LPS mediates a concentration- and time-dependent increase in the rate of synthesis of alpha 1 PI in mononuclear phagocytes. There is a 4.5-8.7-fold increase in functionally active inhibitor delivered to the cell culture fluid of monocytes. The effect of LPS is specific in that it is neutralized by an mAb to the lipid A moiety. The increase in expression of alpha 1 PI mediated by LPS occurs in the context of other specific changes in the expression of serine proteinase inhibitor genes in mononuclear phagocytes. There is an increase in the rate of synthesis of C1 inhibitor and a decrease in synthesis of alpha 2 macroglobulin. Regulation of alpha 1 PI by LPS is distinctive in that it is largely determined by a change in the efficiency of translation of alpha 1 PI mRNA. LPS has no effect on the rate of posttranslational processing and/or secretion of alpha 1 PI and, therein, causes greater intracellular accumulation of alpha 1 PI in mononuclear phagocytes from individuals with homozygous PiZZ alpha 1 PI deficiency.

Clonal gene therapy: transplanted mouse fibroblast clones express human alpha 1-antitrypsin gene in vivo

A retroviral vector was used to insert human alpha 1-antitrypsin (alpha 1AT) complementary DNA into the genome of mouse fibroblasts to create a clonal population of mouse fibroblasts secreting human alpha 1AT. After demonstrating that this clone of fibroblasts produced alpha 1AT after more than 100 population doublings in the absence of selection pressure, the clone was transplanted into the peritoneal cavities of nude mice. When the animals were evaluated 4 weeks later, human alpha 1AT was detected in both sera and the epithelial surface of the lungs. The transplanted clone of fibroblasts could be recovered from the peritoneal cavities of those mice and demonstrated to still be producing human alpha 1AT. Thus, even after removal of selective pressure, a single clone of retroviral vector-infected cells that expressed an exogenous gene in vitro, continued to do so in vivo, and when recovered, continued to produce the product of the exogenous gene.

Evaluation of alveolar macrophages in normals and individuals with active pulmonary sarcoidosis for the spontaneous expression of the interleukin-1 beta gene

We have evaluated the hypothesis that the presence of large numbers of activated helper/inducer T lymphocytes in the lungs of individuals with active pulmonary sarcoidosis is associated with the exaggerated release of interleukin-1 (IL-1) by alveolar macrophages. Evaluation of media from unstimulated cultured sarcoid alveolar macrophages failed to detect IL-1 activity. When parallel cultures of sarcoid and normal alveolar macrophages were stimulated with lipopolysaccharide (LPS), they released similar amounts of IL-1 activity. Using a highly specific polyclonal anti-IL-1 beta antibody and flow cytometry to evaluate cell-associated IL-1 beta, analysis of fresh alveolar macrophages from patients with active sarcoidosis and normal individuals revealed no detectable cell-associated IL-1 beta, but IL-1 beta was present when macrophages from sarcoid patients and normals were stimulated with LPS. Similar observations were made using immunoblot analysis of cell lysates of the same unstimulated and stimulated macrophages. Finally, Northern analysis of alveolar macrophages for IL-1 beta mRNA transcripts demonstrated minimal, but equivalent, amounts of IL-1 beta in both normal and sarcoid macrophages, as compared to the much larger quantities present in LPS-stimulated alveolar macrophages. Thus, while alveolar macrophages of individuals with sarcoidosis are clearly capable of expressing the IL-1 beta gene, these findings suggest that altered expression of the IL-1 beta gene by alveolar macrophages does not play a central role in the exaggerated lung T-cell activation characteristic of sarcoidosis.

Production of glycosylated physiologically "normal" human alpha 1-antitrypsin by mouse fibroblasts modified by insertion of a human alpha 1-antitrypsin cDNA using a retroviral vector

Alpha 1-Antitrypsin (alpha 1AT) deficiency is a hereditary disorder characterized by reduced serum levels of alpha 1AT, resulting in destruction of the lower respiratory tract by neutrophil elastase. As an approach to augment alpha 1AT levels in this disorder with physiologically normal human alpha 1AT, we have integrated a full-length normal human alpha 1AT cDNA into the genome of mouse fibroblasts. To accomplish this, the retroviral vector N2 was modified by inserting the simian virus 40 early promoter followed by the alpha 1AT cDNA. Southern analysis demonstrated that the intact cDNA was present in the genome of selected clones of the transfected murine fibroblasts psi 2 and infected NIH 3T3. The clones produced three mRNA transcripts (5.8, 4.8, and 2.4 kilobases) containing human alpha 1AT sequences, secreted an alpha 1AT molecule recognized by an anti-human alpha 1AT antibody, with the same molecular mass (52 kDa) as normal human alpha 1AT and that complexed with and inhibited human neutrophil elastase. The psi 2 produced alpha 1AT was glycosylated, and when infused intravenously into mice, it had a serum half-life similar to normal alpha 1AT purified from human plasma and markedly longer than that of nonglycosylated human alpha 1AT cDNA-directed yeast-produced alpha 1AT. These studies demonstrate the feasibility of using a retroviral vector to insert the normal human alpha 1AT cDNA into non-alpha 1AT-producing cells, resulting in the synthesis and secretion of physiologically "normal" human alpha 1AT.