Abstract P3-06-05: Not presented

This abstract was not presented at the symposium.

Multi-institutional randomized control study of haemolysis in stored red cell units prepared manually or by an automated system

BACKGROUND

The haemolysis level at the end of storage is a performance parameter for RBC preparations. In the evaluation of new devices or new processes for processing blood, it is relevant to evaluate whether the haemolysis is linked to (1) specific characteristics of the blood donor, or (2) the nature of the blood-processing methodologies.

MATERIALS AND METHODS

As part of the validation of a new automated whole blood processing system compared to the current manual methods, randomized, paired crossover studies were conducted evaluating measures of blood component quality, including RBC haemolysis over 42 days of storage.

RESULTS

The association between haemolysis and the individual subject was evaluated by modelling haemolysis with independent predictors of treatment (control and test processing) and leucocyte reduction as fixed factors with donor and laboratory as random effects in a mixed-effects ANOVA model. It was found that the day 42 haemolysis values were strongly dependent on the donor subject, with an intraclass correlation coefficient of 0.81.

CONCLUSIONS

The data reported in this study suggest a link between the specific whole blood donor and the haemolysis levels observed in red-blood-cell units stored refrigerated for 42 days. Additional research to identify possible donor characteristics associated with haemolysis during storage is warranted.

In vivo and in vitro characteristics of double units of RBCs collected by apheresis with a single in-line WBC-reduction filter

BACKGROUND

A novel apheresis procedure for a blood separator (MCS+, Haemonetics) enables the collection of 2 WBC-reduced RBC units in a single donation by using one disposable set with one in-line WBC-reduction filter (RC2H, Pall Corp.). The objective of this study was to evaluate the filtration performance in connection with different prefiltration RBC storage conditions and with the in vitro and in vivo storage quality of the filtered units.

STUDY DESIGN AND METHODS

Sixty-six 2-unit RBC collection and gravity-filtration procedures were completed at three sites, resulting in 132 RBC units. Filtration of the double RBC units was performed at room temperature (RT) within 8 hours of collection (n = 36) and under refrigeration (1-6 degrees C) for up to 24 hours (n = 10) and 72 hours (n = 20) before filtration. RBC quality was compared to that of nonfiltered apheresis RBC units (n = 10).

RESULTS

Median filtration time was 6.5 and 14 minutes for units stored at RT and under refrigeration, respectively. All 132 RBC units had residual WBC counts <0.4 x 10(6). The refrigerated units showed a greater mean log reduction in WBCs: 5.06 +/- 0.16 (24 hour) and 4.74 +/- 0.48 (72 hour), respectively, than did RT units: 4.47 +/- 0.28 (p<0.05). RBC loss was less than 12 percent in all cases (mean, 7.8 +/- 1.8%). Minimal differences in volume were observed between the paired RBC units. In vitro RBC storage characteristics of the filtered units were as expected and similar to those of the nonfiltered units. For RBC units held at RT (n = 24), the mean in vivo 24-hour recovery was 81.8 +/- 8.4 percent (double-label).

CONCLUSION

Satisfactory filter performance in terms of WBC removal and RBC loss was observed with all 66 procedures, irrespective of storage conditions before filtration.

A hypoallergenic derivative of the major allergen of the dust mite Lepidoglyphus destructor, Lep d 2.6Cys, induces less IgE reactivity and cellular response in the skin than recombinant Lep d 2

BACKGROUND

The major allergen of the dust mite Lepidoglyphus destructor, Lep d 2, has been produced as a recombinant allergen (rLep d 2) with IgE reactivity both in vivo and in vitro. A modified form of rLep d 2 (rLep d 2.6Cys) obtained by site-directed mutagenesis has been shown to have a reduced IgE reactivity in vitro. In this study we have compared the ability of rLep d 2 and rLep d 2.6Cys to elicit positive skin prick tests and cellular responses among L. destructor-sensitized subjects.

METHODS

Seventeen subjects were skin prick-tested with rLep d 2, rLep d 2.6Cys, histamine and negative controls and 17-20 h later skin biopsy specimens were taken from the skin prick-tested sites. The biopsy specimens were stained immunohistochemically for EG2+, CD3+, CD1a+, mast cell tryptase+, and IgE+ cells. Dermal cell infiltrates were judged in hematoxylin and eosin staining. Total IgE and allergen-specific IgE were determined by CAP-RAST.

RESULTS

Compared to rLep d 2, rLep d 2.6Cys induced significantly smaller and fewer skin prick test reactions (p < 0.001) and dermal cell infiltrates (p < 0.05). Further, rLep d 2.6Cys induced fewer EG2+ cells (p < 0.001) but more tryptase+ cells (p < 0.05) than rLep d 2. A positive RAST to rLep d 2 was obtained for 88.2% of the subjects, while only 35.2% displayed a positive RAST to rLep d 2.6Cys.

CONCLUSION

This study demonstrates that rLep d 2.6Cys is less able to evoke IgE-mediated reactions and cellular responses, as measured both in skin and in serum, than rLep d 2. In the future this hypoallergenic derivative may be a promising candidate molecule for immunotherapy of L. destructor-allergic patients.

The effect of leukocyte-reduction method on the amount of human cytomegalovirus in blood products: a comparison of apheresis and filtration methods

This study examined the effectiveness of 3 leukocyte-reduction (LR) methods in depleting the residual level of cytomegalovirus (CMV) in blood products measured by quantitative polymerase chain reaction (QA-PCR). At 2 locations over 3 allergy seasons, apheresis platelets and whole blood were collected from 52 healthy CMV seropositive subjects having an elevated titer of CMV DNA (median = 2400 genome equivalents [GE]/mL) resulting in 32 evaluable LR apheresis platelets, 31 filtered platelets from whole blood, and 31 filtered red blood cells (RBCs) from whole blood. Leukoreduction by apheresis and filtration resulted in substantial reduction of detectable CMV DNA levels with 99.9% of the LR products expected to have less than 500 GE/mL of CMV DNA. No difference was found between methods (P = .52). CMV genomic leukocyte subset localization was determined by QA-PCR of fluorescence-activated cell sorter (FACS)-sorted peripheral blood from 20 seropositive subjects (n = 10 &gt; 100 GE/mL, n = 10 QA-PCR negative). CMV was detected in monocyte (13 of 20) and granulocyte (3 of 20) fractions. Presence of competent virus in QA-PCR positive (&gt; 100 GE/mL) peripheral blood samples was verified with 4 of 19 subjects positive in shell vial assay, and 8 of 18 positive for CMV gene products (messenger RNA). We observed a seasonal DNAemia variation in seropositive subjects. CMV seropositive subjects (n = 45) entered into longitudinal monitoring in March/April 1999 were QA-PCR negative at baseline. Subjects converted to a positive QA-PCR coincident with increased seasonal allergen levels (Norfolk 15 of 18 evaluable in 43.4 ± 9.48 days; Denver, 16 of 23 evaluable in 96 ± 26.3 days). These data demonstrate effective reduction of CMV load by LR during periods of DNAemia in CMV seropositive subjects.

Cloning of three new allergens from the dust mite Lepidoglyphus destructor using phage surface display technology

The dust mite Lepidoglyphus destructor is a common species in Europe and a major cause of dust mite allergy in rural surroundings, but it also contributes to dust mite allergy in urban areas. One major allergen, Lep d 2, has been expressed as a recombinant protein and evaluated both in vivo and in vitro and shown to detect 60% or more of L. destructor-sensitized subjects. Additional recombinant allergens are needed to obtain a reliable diagnostic tool for L. destructor allergy. The aim of this study was to clone and express new allergens from L. destructor and determine their recognition frequency among sensitized individuals. A phage display cDNA expression library was constructed and screened with sera from L. destructor-sensitized individuals. The cDNAs encoding the allergens were cloned into the pET17b vector and subsequently expressed in Escherichia coli as C-terminal His6-tagged proteins. Immunoblotting of the recombinant proteins was performed using sera from 45 subjects allergic to L. destructor. Three new allergens from L. destructor, Ld 5 (originating from a partial Lep d 5 clone), Lep d 7 and Lep d 13, were identified and recognized by 4/45 (9%), 28/45 (62%) and 6/45 (13%) sera from L. destructor-sensitized subjects, respectively.

Molecular population genetics of male accessory gland proteins in Drosophila

Drosophila seminal proteins have an unusually high rate of molecular sequence evolution, suggesting either a high rate of neutral substitution or rapid adaptive evolution. To further quantify patterns of polymorphism and divergence in genes encoding seminal proteins, also called accessory gland proteins (Acp's), we conducted a sequencing survey of 10 Acp genes in samples of Drosophila melanogaster and D. simulans (Acp29AB, Acp32CD, Acp33A, Acp36DE, Acp53Ea, Acp62F, Acp63F, Acp76A, Acp95EF, and Acp98AB). Mean heterozygosity at replacement sites in D. simulans was 0.0074 for Acp genes and 0.0013 for a set of 19 non-Acp genes, and mean melanogaster-simulans divergence at replacement sites was 0.0497 for Acp genes and 0.0107 at non-Acp genes. The elevated divergence of Acp genes is thus accompanied by elevated within-species polymorphism. In addition to the already-reported departures of Acp26A, Acp29AB, and Acp70A from neutrality, our data reject neutrality at Acp29AB and Acp36DE in the direction of excess replacements in interspecific comparisons.

Evaluation of an automated system for the collection of packed RBCs, platelets, and plasma

BACKGROUND

This study evaluated the quality of WBC-reduced platelets, RBCs, and plasma collected on a new system (Trima, Gambro BCT) designed to automate the collection of all blood components. The study also evaluated donor safety and suitability of these components for transfusion.

STUDY DESIGN AND METHODS

In Phase I, the quality of the components collected on the new system was evaluated by standard in vitro and in vivo testing methods. Results were compared to those from control components collected by currently approved standard methods. In Phase II, additional collections were performed to evaluate the acceptability of the new system and the safety of platelets collected.

RESULTS

In vivo 24-hour RBC recovery was 76.8 +/- 3.1 percent for the test RBC units and 77.1 +/- 4.4 percent recovery for whole-blood (control) RBCs. The differences between test and control platelet results in the in vivo and in vitro assays were not clinically significant. Plasma clotting factors and fibrinogen levels met international standards. The system was well accepted by donors, and no major adverse donor reactions were reported for the 68 procedures performed. No problems were reported with transfusing the blood components collected.

CONCLUSION

Blood components collected with the Trima are equivalent to currently available components, and they meet the applicable regulatory standards. This system provides consistent, standardized components with predictable yields. It provides the option of fully automating the collection of all blood components.

Evaluation of in vivo and in vitro quality of apheresis-collected RBC stored for 42 days

BACKGROUND AND OBJECTIVES

New technological developments make it possible to collect red blood cells (RBCs) by apheresis, which allows for better product consistency and has the potential for improved RBC quality. The purpose of these studies was to evaluate the quality and consistency of units of RBCs collected by apheresis using the MCS+(R) machine (Haemonetics Corp., Braintree, Mass., USA).

MATERIALS AND METHODS

Two studies were performed. In study 1 (n = 10), using containers and CP2D/AS-3 solutions from Medsep Corp. (Covina, Calif. USA), one-unit apheresis RBCs were compared to manually collected RBCs in a random crossover design. In study 2 (n = 12), 6 subjects had one unit collected, while the remaining 6 subjects had two units of RBCs collected with comparison to previously manually collected RBCs from the same donors. Haemonetics containers and solutions were used in study 2.

RESULTS

Low RBC volume variability was found for the apheresis collections with a standard deviation of only 6 ml difference between actual and target volumes. Combining the data from the two studies (n = 21 pairs), at 42 days of storage, the apheresis units showed slightly lower hemolysis (0.44+/-0.26 vs. 0.61+/-0.50%), lower supernatant potassium levels (50+/-3 vs. 53+/-3 mEq/l), and improved tolerance to osmotic shock (47+/-3 vs. 49+/-3%) as compared to manual units (p < 0.05). There was no statistically significant difference in RBC ATP (3.0+/-0.6 vs. 2.9+/-0.5 micromol/g Hb) or in 24-hour percent recoveries (81+/-6 for apheresis vs. 81+/-4% for apheresis red cells). Apheresis RBC quality was not affected by the manufacturer (Haemonetics vs. Medsep) of solutions and containers.

CONCLUSIONS

RBC units collected by apheresis demonstrated low variability in volume of RBC mass collected, and showed similar RBC properties as compared to manually collected RBCs after processing and after 42 days of storage.

Genetics of alpha-amanitin resistance in a natural population of Drosophila melanogaster

The genetic basis of variation in resistance to natural toxins is of interest for both ecological and evolutionary genetics. The wide variety of larval resources used by Drosophila, both within and between species, makes flies an excellent system for studying causes and consequences of selection resulting from exposure to natural toxins associated with different resources. In this study we carry out a genetic analysis of alpha-amanitin resistance in a population sample of Drosophila melanogaster. Data from mapping crosses of chromosome III support a role for a naturally occurring polymorphism in a multidrug resistance gene (Mdr65A) in alpha-amanitin resistance. However, there are no amino acid differences between resistant and sensitive chromosomes at Mdr65A. Therefore, if Mdr65A mutants contribute to the difference between alpha-amanitin-resistant and alpha-amanitin-sensitive third chromosome lines, the underlying cause is a gene regulatory mutation.

Cloning, characterization and expression of complete coding sequences of three IgE binding Malassezia furfur allergens, Mal f 7, Mal f 8 and Mal f 9

Malassezia furfur, formerly known as Pityrosporum orbiculare or P. ovale, is a yeast that colonizes human skin. Normally, this yeast is nonpathogenic but under the influence of predisposing factors it may induce IgE reactivity in patients with atopic dermatitis. Approximately 40-65% of atopic dermatitis patients have IgE antibodies and/or skin reactivity against M. furfur and a higher T-cell response against this yeast is found in atopic dermatitis patients than in healthy individuals. By making a cDNA library displayed on a phage surface, we previously cloned five different IgE-binding proteins, Mal f 5, Mal f 6, MF 7, MF 8 and MF 9, from this yeast. The cDNAs encoding these allergens were sequenced and expressed in Escherichia coli. The sequences of MF 7, MF 8 and MF 9 were not full length (missing their 5'-ends) giving only partial gene products. To obtain complete cDNA sequences, we performed RACE-PCR to amplify the 5'-ends of each cDNA. These PCR products were sequenced and analyzed. The coding sequences of Mal f 7, Mal f 8 and Mal f 9 encode proteins with ORFs of 141 (16.2 kDa), 179 (19.2 kDa) and 126 (14.0 kDa) amino-acid residues, respectively. None of the putative proteins showed significant sequence homology with other known proteins in the searched database. The proteins encoded by the complete cDNA sequences were expressed in E. coli as recombinant proteins. Immunoblotting and radioallergosorbant test data showed that all of the expressed recombinant proteins have the ability to bind serum IgE from atopic dermatitis patients and furthermore, the M. furfur extract could specifically inhibit this IgE binding.

Reduced X-linked nucleotide polymorphism in Drosophila simulans

Population genetic theory predicts that selectively driven changes of allele frequency for both beneficial and deleterious mutants reduce polymorphism at tightly linked sites. All else being equal, these reductions in polymorphism are expected to be greater when recombination rates are lower. Therefore, the empirical observation of a positive correlation between recombination rates and amounts of DNA polymorphism across the Drosophila melanogaster genome can be explained by two very different types of natural selection. Here, we evaluate alternative models of effects of selection on linked sites by comparison of X-linked and autosomal variation. We present polymorphism data from 40 genes distributed across chromosome arms X and 3R of Drosophila simulans, a sibling species of D. melanogaster. We find significantly less silent polymorphism in D. simulans on the X chromosome than on 3R, but no difference between arms for silent divergence between species. This pattern is incompatible with predictions from theoretical studies on the effect of negative selection on linked sites. We propose that some form of positive selection having greater effects on sex chromosomes than on autosomes is the better explanation for the D. simulans data.

Adaptive evolution of relish, a Drosophila NF-kappaB/IkappaB protein

NF-kappaB and IkappaB proteins have central roles in regulation of inflammation and innate immunity in mammals. Homologues of these proteins also play an important role in regulation of the Drosophila immune response. Here we present a molecular population genetic analysis of Relish, a Drosophila NF-kappaB/IkappaB protein, in Drosophila simulans and D. melanogaster. We find strong evidence for adaptive protein evolution in D. simulans, but not in D. melanogaster. The adaptive evolution appears to be restricted to the IkappaB domain. A possible explanation for these results is that Relish is a site of evolutionary conflict between flies and their microbial pathogens.

Quality and clinical response to transfusion of prestorage white cell-reduced apheresis platelets prepared by use of an in-line white cell-reduction system

BACKGROUND

This study evaluated the quality and clinical effectiveness of white cell (WBC)-reduced apheresis platelets collected by the use of a new technology, fluidized particle-bed separation.

STUDY DESIGN AND METHODS

In phase 1, six suitable donors underwent two separate plateletpheresis procedures on one occasion, each separated by less than 10 minutes. In random order, a control unit was collected with the COBE Spectra and a test unit with the Spectra Leukocyte-Reduction System (LRS). The quality of apheresis platelet components was assessed by an in vitro test panel, and residual WBCs were counted by Nageotte chamber and flow cytometric methods. For the in vivo studies, the test and control units were randomly labeled with either 51Cr or 111In at the end of storage and transfused simultaneously to the donor. Samples were taken for calculation of platelet survival and recovery. In phase II, 109 thrombocytopenic patients were given platelets collected by use of the Spectra LRS.

RESULTS

Test platelets had significantly fewer residual WBCs (median 7.6 x 10(4)) than control platelets (median 3.9 x 10(5)), with equivalent in vitro function values. Test and control platelets had similar recovery and survival. Transfused platelets collected by use of the LRS achieved a mean 1-hour corrected-count increment of 19.3.

CONCLUSION

The LRS collects platelet components with significantly lower WBC contamination without adverse effects on the function or in vivo survival of the platelets.

Evaluation of specific IgE to the recombinant group 2 mite allergens Lep d 2 and Tyr p 2 in the Pharmacia CAP system

BACKGROUND

Several recombinant allergens have been shown to be potentially useful for diagnosis of IgE-mediated allergy, but only a few recombinant allergens are at present commercially available in serological assays for detection of specific IgE. The aim of this study was to evaluate the IgE binding to the recombinant major dust mite allergens rLep d 2 and rTyr p 2 and compare it with the IgE binding to the commercial mite extracts Lepidoglyphus destructor and Tyrophagus putrescentiae in the Pharmacia RAST CAP System.

METHODS

The recombinant allergens rLep d 2 and rTyr p 2 were immobilised on ImmunoCAPs, and sera from 461 Swedish farmers who are frequently exposed to mites were analysed for specific IgE antibodies. Immunoblotting was performed to evaluate discrepancies between the results obtained with the recombinant and the commercial CAP assays.

RESULTS

The IgE values of each recombinant assay significantly correlated with the IgE values of the corresponding commercial CAP assay. The sensitivity of the rLep d 2 assay was 73.3% and that of the rTyr p 2 assay, 60.5% of that provided by the commercial L. destructor and T. putrescentiae assays. Two subjects out of 416, who tested negative in the commercial L. destructor assay, were positive to rLep d 2. The corresponding figures for rTyr p 2 and the T. putrescentiae extract were 5/418. The possibility that these subjects were sensitised to L. destructor and T. putrescentiae could not be excluded.

CONCLUSIONS

The data suggest that it may be possible to use rLep d 2 and rTyr p 2 on ImmunoCAPs to detect and quantify IgE antibodies to these, the major allergens of L. destructor and T. putrescentiae. It appears likely that the addition of just a few more recombinant L. destructor and T. putrescentiae allergens in the CAP assay will be sufficient for in vitro diagnosis of IgE mediated allergy to L. destructor and T. putrescentiae.

Identification and characterisation of two allergens from the dust mite Acarus siro, homologous with fatty acid-binding proteins

BACKGROUND

Dust mites are a major cause of allergic disease worldwide. The dust mite Acarus siro is an inducer of occupational allergy among farmers, but sensitisation has also been found in non-farming populations.

METHODS

A degenerate primer was designed to the N-terminal amino acid sequence of a 15-kD IgE-binding protein in A. siro extract. The cDNA sequence was obtained by using reverse transcriptase polymerase chain reaction, standard cloning and sequencing techniques. The protein was expressed in Escherichia coli with a 6-histidine tag at its C-terminus. Immunoblotting of the recombinant protein and whole extract was performed using patient sera.

RESULTS AND CONCLUSION

15 and 17-kD allergens were identified in a fraction of A. siro extract. The cDNA of the 15-kD allergen was isolated, cloned and sequenced and the allergen was expressed as a recombinant protein. The calculated molecular weight of the cDNA-encoded protein is 14.2 kD. The predicted amino acid sequence has one potential N-glycosylation site at position 4-6 and a cytosolic fatty acid-binding protein signature at position 5-22. The protein has 64% sequence identity with Blo t 13, an allergen from the dust mite Blomia tropicalis, as well as homology with several other fatty acid-binding proteins (FABPs) from different organisms. The allergen was named Aca s 13 and was recognised strongly by 3 of 13 (23%) of the subjects investigated. The amino acid sequence of the 17-kD protein was partly determined and it also showed high sequence homology with Blo t 13 and FABPs.

Selective cloning of allergens from the skin colonizing yeast Malassezia furfur by phage surface display technology

The yeast Malassezia furfur, also known as Pityrosporum orbiculare (ovale), is part of the normal microflora of the human skin but has also been associated with different skin diseases including atopic dermatitis. More than 50% of atopic dermatitis patients have positive skin test and specific IgE to M. furfur extracts; however, the pathophysiologic role of these IgE-mediated reactions in the development of the disease remains unknown. The yeast is able to produce a wide panel of IgE-binding proteins, variably recognized by sera of individual patients. In order to assess the contribution of individual components to the disease, highly pure allergen preparations are required. We have cloned M. furfur allergens from a cDNA library displayed on the phage surface, sequenced the inserts and produced recombinant proteins in Escherichia coli. Phage displaying IgE-binding proteins were selectively enriched from the library using IgE from a M. furfur-sensitized atopic dermatitis patient as a ligand. We were able to identify five different inserts coding for IgE-binding polypeptides. Three of the sequenced cDNA encode incomplete gene products with molecular masses of 21.3 kDa (MF 7), 14.4 kDa (MF 8), and 9.7 kDa (MF 9), respectively, having no sequence similarity to known proteins. The other two cDNA encode allergens of 18.2 kDa (Mal f 5) and 17.2 kDa (Mal f 6). Mal f 5 shows significant homology to M. furfur allergens Mal f 2, Mal f 3 and an Aspergillus fumigatus allergen Asp f 3. Mal f 6 has significant homology with cyclophilin. All of the recombinant polypeptides were capable of binding serum IgE from atopic dermatitis patients in immunoblotting experiments. The availability of pure recombinant M. furfur allergens will allow the careful investigation of the role of IgE-binding proteins in atopic dermatitis.

Immunologic characterization of natural and recombinant Mal f 1 yeast allergen

BACKGROUND

Individuals with atopic dermatitis (AD) often have IgE antibodies against protein components of Malassezia furfur. The cDNA encoding one of these proteins (Mal f 1) has recently been cloned and sequenced.

OBJECTIVE

We sought to express recombinant Mal f 1 (rMal f 1) allergen in large quantities by using different expression systems. The primary aim was to characterize the IgE-binding properties of rMal f 1 in comparison with its natural counterpart in M furfur extract.

METHODS

We have expressed and purified Mal f 1 from prokaryotic (Escherichia coli) and eukaryotic cells (baculovirus-infected insect cells). The rMal f 1 produced in both systems has been tested for the ability to be recognized by IgE from patients with specific serum IgE to M furfur by using immunoblotting and the Pharmacia CAP System RAST FEIA.

RESULTS

Sixty-one percent of sera from 95 patients showed positive RAST responses to the rMal f 1 produced in the baculovirus expression system and 43% to the E coli -produced rMal f 1. Both the E coli - and baculovirus-produced proteins can specifically inhibit IgE binding to a 36-kd protein band (Mal f 1) in immunoblotting, indicating that the recombinant proteins contain the majority, if not all, the IgE-binding epitopes of Mal f 1. Recombinant Mal f 1 is able to release histamine from basophils of an atopic individual.

CONCLUSION

We have expressed and purified rMal f 1, which can bind IgE in a way resembling natural Mal f 1. The ability to produce recombinant allergens with similar properties to their native counterparts has many potential uses, such as accurately diagnosing causes of IgE-mediated allergy.

Proline-induced disruption of a transmembrane alpha-helix in its natural environment

alpha-Helix formation in globular proteins has been studied both theoretically and experimentally for decades, while a lack of both high-resolution structures and suitable experimental techniques has hampered the study of helices in membrane proteins. We have developed a new experimental approach, glycosylation mapping, where the active site of the lumenally exposed endoplasmic reticulum enzyme oligosaccharyl transferase is used as a point of reference against which the position of a transmembrane segment in the membrane can be measured. Here, we report an initial analysis of the helix-breaking properties of proline residues inserted in a transmembrane helix. We find that proline residues can break a transmembrane helix, but only when inserted near the end, and only when the helix is sufficiently long. The glycosylation mapping technique may be generally useful for determining the position of transmembrane helices in the membrane.

IgE binding capacity of synthetic and recombinant peptides of the major storage mite (Lepidoglyphus destructor) allergen, Lep d 2

BACKGROUND

Lepidoglyphus destructor is an important non-pyroglyphid mite species in Europe and a dominant allergen in farming environments. The major allergen of L. destructor, Lep d 2, is a protein of 13.2 kD that is recognised by about 90% of sera RAST positive to this mite species.

METHODS

The cDNA of two isoallergens of the Lep d 2 has previously been sequenced and the protein expressed in different protein expression systems. In order to map the B-cell epitopes, the full length protein and the truncated forms of the protein have been expressed in Escherichia coli as glutathione-S-transferase (GST) fusion proteins. Recombinant Lep d 2 fragments and synthetic overlapping 15 mer peptides spanning Lep d 2 were probed with sera from patients allergic to storage mite.

RESULTS

The full-length (125 amino acids) GST fusion protein reacted strongly with patient IgE in Western blots and dot blots. Synthetic peptides failed to react with IgE antibodies from mite-allergic patients and the truncated fusion proteins displayed weak IgE-binding capacity.

CONCLUSION

We conclude that there are no dominant linear IgE-binding epitopes in Lep d 2. Recombinant or synthetic Lep d 2 fragments may, however, be further evaluated as hypoallergenic candidate molecules for specific immunotherapy.

Contribution of disulphide bonds to antigenicity of Lep d 2, the major allergen of the dust mite Lepidoglyphus destructor

To study the contribution of the 3 disulphide bonds in the major allergen Lep d 2 to the antigenic structure, site-directed mutagenesis was performed. Mutants with one or more cysteine residues altered were constructed with a histidine residue tag for purification purposes and expressed as recombinant proteins in E. coli. Seven mutants were analysed: 3 single mutants (Cys 8, Cys 21 and Cys 72), 3 double mutants (Cys 8-117, Cys 21-16 and Cys 72 77) and one mutant with all 6 cysteines altered (6 Cys). The evaluation of IgE reactivity in 10 allergic patients showed that the disulphide bond formed by cysteine 72 and 77 was the single most contributing bond to IgE binding. Mutants with disruption of the Cys 8-117 bond had a lesser reduction in IgE binding, even though this alteration seemed to influence the compact nature of Lep d 2. However, to abolish the IgE reactivity almost completely, all 6 cysteines had to be altered. A monoclonal antibody previously raised against Lepidoglyphus destructor showed a similar binding as human IgE with no reactivity to the Cys 72 77 or the 6 Cys mutant. Using skin prick test we found no reaction to the 6 Cys mutant at the concentrations tested (1-100 microg/ml) in an Lepidoglyphus destructor allergic patient, while the T-cell reactivity was preserved. The 6 Cys mutant of Lep d 2 may, after further evaluation, be a candidate molecule for improved immunotherapy of Lepidoglyphus destructor allergy.

Expression of two isoforms of Lep d 2, the major allergen of Lepidoglyphus destructor, in both prokaryotic and eukaryotic systems

BACKGROUND

The dust mite Lepidoglyphus destructor is a major cause of allergic diseases among farmers. We have previously cloned and sequenced two isoforms of the major allergen Lep d 2 (formerly designated Lep d 1) and found significant homology to group 2 allergens of the house dust mite species Dermatophagoides. We now report on the production and characterization of recombinant Lep d 2.

OBJECTIVE

We have expressed both isoforms in two different expression systems; a eukaryotic system, baculovirus in insect cells and a prokaryotic system, E. coli. We have compared the two systems in regard to production yields and immunoreactivity of the recombinant allergens.

METHODS

The complete cDNA including the natural leader sequence was cloned into the pBlueBacIII transfer vector, and the rLep d 2 was produced as a secreted protein in baculovirus. For the expression in E. coli, the cDNA was cloned into the pET vector, and the rLep d 2 was produced with six C-terminal histidine residues. The purified recombinant allergens were tested for immunoreactivity with 10 sera from subjects allergic to Lepidoglyphus destructor and were compared with native Lep d 2 using inhibition immunoblotting. The ability of the recombinant allergens to release histamine from basophils was evaluated using a histamine release assay.

RESULTS

Both expression systems produced immunoreactive recombinant allergens. They inhibited the binding of human sera to native Lep d 2 confirming their retained IgE binding properties. The yield of pure recombinant protein from the prokaryotic system was approximately 1 mg/L compared to the eukaryotic system which produced up to 4 mg/L in an adherent cell culture system.

CONCLUSIONS

We have produced recombinant Lep d 2 in prokaryotic and eukaryotic expression systems which are comparable to the native allergen. Recombinant Lep d 2 might now be included in more extensive clinical studies to confirm its usefulness in the in vitro and the in vivo diagnosis of Lepidoglyphus destructor.

The design of arm pressure covers to alleviate pain in high G maneuvers

HYPOTHESIS

Arm pain has been noted especially when increased coverage anti-G suits are worn in combination with PBG (pressure breathing during G) in high G centrifuge test runs. Arm pain has forced the termination of test runs and has the potential to cause a serious decrement in a pilot's ability to function effectively during high-G flight. Based on the theory that arm pain is caused by fluid pooling in the arm, four new pressure cover systems for the arm were designed and tested.

METHODS

Seven test subjects wore each design in a series of runs in a dynamic flight simulator (DFS). Subjects experienced both gradual and rapid onset rate runs with G levels ranging from +3.0 G to +9.0 G. Data were collected on the maximum G's achieved, pain location, and pain intensity. Subjective responses on the comfort and function of each design and overall arm cover design preferences were also obtained via a questionnaire.

RESULTS

Analysis of the DFS data, using a two-factor ANOVA (subjects, designs), revealed that each of the new designs provided significantly better protection from arm pain than the control condition (no protection) and that each of the designs significantly improved the maximum G level attained during rapid onset acceleration in the range of +1 G.

CONCLUSION

No positive correlation was found between subject ranking of the four new design concepts at the conclusion of the study in terms of the pain reduction they provided and the pain levels reported during DFS testing.

Cloning and characterisation of a group II allergen from the dust mite Tyrophagus putrescentiae

The complete cDNA encoding a major allergen from the dust mite Tyrophagus putrescentiae, Tyr p 2, has been sequenced and expressed. A degenerate primer was designed to the N-terminal amino acid sequence of the 16-kDa protein. The complete cDNA sequence was achieved by using reverse transcriptase PCR, PCR+1, standard cloning and sequencing techniques. The cDNA of Tyr p 2 is 552 nucleotides in length from the start codon including 126 nucleotides after the stop codon up to the beginning of the poly(A) tail. The leader sequence consists of 15 amino acids. Regarding the predicted amino acid sequence, there are no potential N-glycosylation sites (N-X-S/T). The sequence showed similarity to group II allergens from other mite species, and some regions are completely conserved. To show that the cloned cDNA sequence was coding for an allergen, Tyr p 2 was expressed in Escherichia coli and shown to react with a T. putrescentiae-positive serum pool.

Calmodulin point mutations affect Drosophila development and behavior

Calmodulin (CAM) is recognized as a major intermediary in intracellular calcium signaling, but as yet little is known of its role in developmental and behavioral processes. We have generated and studied mutations to the endogenous Cam gene of Drosophila melanogaster that change single amino acids within the protein coding region. One of these mutations produces a striking pupal lethal phenotype involving failure of head eversion. Various mutant combinations produce specific patterns of ectopic wing vein formation or melanotic scabs on the cuticle. Anaphase chromosome bridging is also seen as a maternal effect during the early embryonic nuclear divisions. In addition, specific behavioral defects such as poor climbing and flightlessness are detected among these mutants. Comparisons with other Drosophila mutant phenotypes suggests potential CAM targets that may mediate these developmental and behavioral effects, and analysis of the CAM crystal structure suggests the structural consequences of the individual mutations.

Membrane-protein engineering

Membrane proteins perform many of the essential functions required for life. They are often the targets of medicinal drugs and have many potential uses in biotechnological processes. Therefore our ability to understand them and manipulate their functions is both important and necessary to enable protein engineers to create 'designer' membrane proteins (that is, proteins designed to have desired properties).

The complete cDNA sequence and expression of the first major allergenic protein of Malassezia furfur, Mal f 1

For the first time the complete cDNA encoding a major allergen and novel protein of the yeast Malassezia furfur, Mal f 1, has been sequenced and expressed. The amino acid sequences of nine tryptic peptides of the protein were determined. Oligonucleotides were designed from these amino acid sequences. The cDNA sequence was obtained by hybridizing these primers to mRNA and enhancement by reverse-transcriptase PCR techniques. The cDNA is 1176 bp in length. It shows an open reading frame of 1050 bp coding for a protein of 38178 Da and a deduced amino acid sequence containing 350 residues. The hydropathy plot and the tryptic digest indicate that the first 22 amino acids represent a leader sequence determining a mature protein of 35 988 Da. The complete encoding cDNA was expressed as a maltose-binding protein fusion protein in Escherichia coli. The recombinant fusion protein reacted with our specific monoclonal antibody and with IgE from patients with atopic dermatitis.

Evaluation of a new prestorage leukoreduction filter for red blood cell units

BACKGROUND AND OBJECTIVES

Prestorage leukoreduction offers a variety of potential benefits and is becoming more commonly practiced. The LeukoNet prestorage leukoreduction filtration system is intended for leukoreduction of red blood cells and uses a vent to allow automatic drainage of red cells from the filter.

MATERIALS AND METHODS

We studied the functional characteristics and the in-vivo and in-vitro properties of leukoreduced AS-1 Red Blood Cells prepared with this new system. Units of AS-1 Red Blood Cells were filtered at 4 degrees C through the LeukoNet filter 24-48 h after collection and stored under usual conditions for 42 days. Residual leukocytes were enumerated using a Nageotte chamber or with a polymerase chain reaction (PCR) technique. In the clinical trial (phase one), 21 donors had units stored with and without leukoreduction for 42 days; biochemical assays were done before and after storage, and 51Cr/99mTc red cell recovery studies at the end of the storage period.

RESULTS

Leukocyte content after filtration was 3.2 +/- 2.6 x 10(4)/unit (n = 21), and all units had < 1 x 10(5) leukocytes (median: 3.8 x 10(4)). In-vivo paired studies showed no difference in 24-hour recovery (control: 82.1 +/- 5.8%; test: 82.9 +/- 6.0%). Hemolysis was halved with leuko-reduction (0.59 +/- 0.30 vs. 0.29 +/- 0.11%; p < 0.05), and glucose consumption was reduced by 5% compared to control units (p = < 0.05). Other biochemical parameters showed no differences. In the practical trial (phase two), filtration time was 41 +/- 23 min. With a residual leukocyte content of 6.6 +/- 4.9 x 10(4)/unit and 14 +/- 3% red cell loss (n = 84). Six additional units underwent leukocyte enumeration by PCR and had 2.6 +/- 1.1 x 10(4) residual leukocytes.

CONCLUSIONS

Under the conditions studied, the LeukoNet leukoreduction filtration system produces about 4-5 log10 leukocyte content reduction.

A neurotransmitter transporter encoded by the Drosophila inebriated gene

Behavioral and electrophysiological studies on mutants defective in the Drosophila inebriated (ine) gene demonstrated increased excitability of the motor neuron. In this paper, we describe the cloning and sequence analysis of ine. Mutations in ine were localized on cloned DNA by restriction mapping and restriction fragment length polymorphism (RFLP) mapping of ine mutants. DNA from the ine region was then used to isolate an ine cDNA. In situ hybridization of ine transcripts to developing embryos revealed expression of this gene in several cell types, including the posterior hindgut, Malpighian tubules, anal plate, garland cells, and a subset of cells in the central nervous system. The ine cDNA contains an open reading frame of 658 amino acids with a high degree of sequence similarity to members of the Na+/Cl(-)-dependent neurotransmitter transporter family. Members of this family catalyze the rapid reuptake of neurotransmitters released into the synapse and thereby play key roles in controlling neuronal function. We conclude that ine mutations cause increased excitability of the Drosophila motor neuron by causing the defective reuptake of the substrate neurotransmitter of the ine transporter and thus overstimulation of the motor neuron by this neurotransmitter. From this observation comes a unique opportunity to perform a genetic dissection of the regulation of excitability of the Drosophila motor neuron.

Ala-insertion scanning mutagenesis of the glycophorin A transmembrane helix: a rapid way to map helix-helix interactions in integral membrane proteins

Alanine insertions into the glycophorin A transmembrane helix are found to disrupt helix-helix dimerization in a way that is fully consistent with earlier saturation mutagenesis data, suggesting that Ala-insertion scanning can be used to rapidly map the approximate location of structurally and/or functionally important segments in transmembrane helices.

A 12-residue-long polyleucine tail is sufficient to anchor synaptobrevin to the endoplasmic reticulum membrane

Synaptobrevin is a tail-anchored protein with a hydrophobic C-terminal transmembrane segment that inserts into the endoplasmic reticulum membrane independently of the SRP/Sec61p pathway. Here, we show that idealized hydrophobic segments composed of 11-17 leucines and 1 valine function as insertion signals in vitro, whereas shorter segments do not. These results suggest that there are no specific requirements beyond overall hydrophobicity for C-terminal endoplasmic reticulum insertion signals.

A nascent secretory protein may traverse the ribosome/endoplasmic reticulum translocase complex as an extended chain

We have measured the minimum number of residues in a translocating polypeptide required to bridge the distance between the P-site in endoplasmic reticulum-bound ribosomes and the lumenally disposed active site of the oligosaccharyl transferase. The results suggest that a nascent chain may traverse the ribosome/translocase complex in a largely extended conformation, and that hydrophobic stop-transfer segments have a more compact, possibly alpha-helical conformation in the translocase.

SecA-independent translocation of the periplasmic N-terminal tail of an Escherichia coli inner membrane protein. Position-specific effects on translocation of positively charged residues and construction of a protein with a C-terminal translocation signal

We have shown previously that the 100-residue-long periplasmic N-terminal tail of the Escherichia coli inner membrane protein ProW can be translocated across the inner membrane in a sec-independent manner and that its translocation is blocked by the introduction of three positively charged residues near its C-terminal end (Whitley, P., Zander, T., Ehrmann, M., Haardt, M., Bremer, E., and von Heijne, G. (1994) EMBO J. 13, 4653-4661). We have now further analyzed the requirements for translocation of the N-terminal tail and found that the introduction of even a single arginine can block translocation. Position-specific differences in the effects on translocation of arginine insertions suggest that the C-terminal end of the N-terminal tail is more critical for translocation than the central and N-terminal regions. We also show that the N-terminal tail is translocated in a truncation mutant where a stop codon is placed immediately after the first transmembrane segment, provided that the transmembrane segment is flanked on its C-terminal end by positively charged residues. Thus, sec-independent translocation of a relatively large domain can be induced by a translocation signal located at the extreme C terminus of a protein.

A quantitative assay to determine the amount of signal peptidase I in E. coli and the orientation of membrane vesicles

The number of Signal Peptidase I (SPasel) molecules per E. coli cell was determined using western blot techniques. Different strains were found to contain approximately 1000 SPasel molecules per cell during exponential growth. Based on the activity of SPasel in vitro it could be estimated that this amount is sufficient to process all translocated precursors. SPasel did not appear to be under growth phase dependent control, but was constitutively expressed. The quantitative western blot technique was also used to establish the orientation and intactness of isolated inner membrane vesicles.

De novo design of integral membrane proteins

We have designed integral membrane proteins with one, two and four hydrophobic transmembrane segments of highly simplified amino acid composition and with appropriately placed positively charged lysine residues intended to control the overall membrane orientation. When expressed in Escherichia coli, these model proteins insert efficiently into the inner membrane and adopt the predicted topologies. This demonstrates the feasibility of de novo design of multi-spanning integral membrane proteins, and opens up new possibilities for membrane protein engineering.

Synergistic insertion of two hydrophobic regions drives Sec-independent membrane protein assembly

We have studied the membrane insertion of two proteins from the inner membrane of Escherichia coli, both with two transmembrane segments connected by a short periplasmic loop: the M13 procoat protein and a mutant "inverted" leader peptidase. Neither molecule depends on the Sec machinery for insertion. We show that the introduction of a charged residue in the second transmembrane segment completely blocks insertion of both proteins. In contrast, a Sec-dependent procoat mutant, where the periplasmic region has been lengthened, inserts into the membrane even in the presence of a charged residue in the second hydrophobic domain. In addition, a large deletion within the second transmembrane domain of the leader peptidase mutant allows membrane translocation, but only under conditions where the SecA protein is functional. Furthermore, we show that the first hydrophobic domain is required for insertion of the short periplasmic loop of the "inverted" leader peptidase. These results suggest that Sec-independent insertion occurs by a synergistic entry of the two neighboring hydrophobic domains into the lipid bilayer.

Sec-independent translocation of a 100-residue periplasmic N-terminal tail in the E. coli inner membrane protein proW

The ProW protein, located in the inner membrane of Escherichia coli, has a very unusual topology with a 100-residue-long N-terminal tail protruding into the periplasmic space. We have studied the mechanism of membrane translocation of the periplasmic tail by analysing ProW-PhoA and ProW-Lep fusion proteins, both in wild-type cells and in cells with an impaired sec machinery. Our results show that the translocation efficiency is not affected by treatments that compromise the SecA and SecY functions, but that translocation is completely blocked by dissipation of the proton motive force or by the introduction of extra positively charged residues into the N-terminal tail. This suggests that the sec machinery can act properly only on domains located on the C-terminal side of a translocation signal, and that the N-terminal tail is driven through the membrane by a mechanism that involves the proton motive force.

The COOH-terminal ends of internal signal and signal-anchor sequences are positioned differently in the ER translocase

Signal peptides (SPs) target proteins to the secretory pathway and are cleaved from the nascent chain once the translocase in the ER has been engaged. Signal-anchor (SA) sequences also interact transiently with the ER translocase, but are not cleaved and move laterally out of the translocase to become permanent membrane anchors. One obvious difference between SP and SA sequences is the considerably longer hydrophobic regions (h regions) of the latter. To study the interaction between SP/SA sequences and the ER translocase, we have constructed signal sequences with poly-Leu h regions ranging in length from 8 to 29 residues and have characterized their locations within the translocase using both a new assay that measures the minimum number of amino acids needed to span the distance between the COOH-terminal end of the h region and the active site of the oligosaccharyl transferase enzyme and an assay where the efficiency of signal peptidase catalyzed cleavage is measured. Our results suggest that SP and SA sequences are positioned differently in the ER translocase.

The DsbA-DsbB system affects the formation of disulfide bonds in periplasmic but not in intramembraneous protein domains

The DsbA and DsbB proteins of Escherichia coli are involved in facilitating the formation of disulfide bonds in periplasmic proteins. Here, we show that the rate of formation of a disulfide bond in the periplasmic domain of the inner membrane protein leader peptidase is reduced in dsbA and dsbB strains, whereas the rate of formation of a disulfide bond engineered into the membrane embedded domain of the same protein is completely unaffected by these mutations. We conclude that the Dsb proteins do not facilitate the formation of intramembraneous disulfides.

Three-dimensional model for the membrane domain of Escherichia coli leader peptidase based on disulfide mapping

We have mapped the interface between the two transmembrane alpha-helices in the membrane domain of the Escherichia coli enzyme leader peptidase by analyzing disulfides formed between pairs of cysteine residues introduced near their respective periplasmic ends. The interface is formed primarily from aliphatic amino acids, and the two helices appear to pack against each other in a left-handed supercoil. We suggest that disulfide mapping may be a generally applicable approach for the construction of models of helix-helix interfaces in membrane proteins.

Platelet storage lesions in second-generation containers: correlation with in vivo behavior with storage up to 14 days

The relationship between in vivo behavior and in vitro characteristics of 59 platelet concentrates (PC) stored for up to 14 days in a synthetic medium or in CPDA-1 plasma was systematically investigated. 25 paired studies (1 study was incomplete) were performed comparing platelets suspended either in the synthetic medium or CPDA-1 plasma with 5 days (n = 5); 7 days (n = 10); 10 days (n = 5); and 14 days (n = 5) of storage. In addition, 10 control studies were performed with freshly prepared PC (6-24 h) in CPDA-1 plasma. Both percent recovery and survival estimations showed decreases with increasing storage duration, irrespective of storage medium used. In both media, with prolonged storage, the platelet survival curves not only became shorter, but also increasingly exponential, suggesting that in vitro storage caused progressive damage to the platelets present in circulation. Survival curves of platelets suspended in synthetic medium remained more linear, indicative of less random damage during storage. Mean population lifespan (MPL) of the stored PC was determined by the area below the survival curve divided by the mean percent recovery for the fresh PC, which was 55%. MPL decreased from 4.5 days (fresh PC) to 0.4 days after 14 days of storage in plasma, with a 50% reduction (t1/2) estimated at 7.2 days of storage. MPL t1/2 for PC stored in the synthetic medium was estimated to be 8.8 days.(ABSTRACT TRUNCATED AT 250 WORDS)

Properties of platelet concentrates prepared after extended whole blood holding time

Extension of the maximum holding time for whole blood collected into a CPD-ADSOL system from 6 to 8 hours at ambient temperature under conditions that cause the temperature of the blood to decrease to 20 to 24 degrees C would facilitate the preparation of platelet concentrates (PCs). In this study, the properties of CPD-PCs prepared and stored for 5 days in PL-732 containers after various initial holding periods were assessed in two laboratories, designated Laboratory A and Laboratory B. Laboratory A found higher platelet-rich plasma (PRP) volumes (276 +/- 25 vs. 249 +/- 19 mL) and platelet yields (76 +/- 18 vs. 66 +/- 18 x 10(9) platelets) with 8-hour holds (n = 10) than with 1- to 2-hour holds (n = 10), although only the difference in PRP volumes was significant (p less than 0.05). No significant difference was observed in autologous in vivo recovery (54 +/- 11 vs. 47 +/- 9%) or survival (167 +/- 37 vs. 170 +/- 25 hrs), as calculated by gamma function using 111In as radiolabel. Laboratory B also found higher PRP volumes (304 +/- 31 vs. 279 +/- 37 mL) and platelet yields with 8-hour holds (n = 12) than with a 6-hour holds (n = 10) (88 +/- 26 vs. 77 +/- 27 x 10(9) platelets). No significant differences were found in morphology score, the extent of release of beta-thromboglobulin, the discharge of lactate dehydrogenase, or hypotonic shock response.(ABSTRACT TRUNCATED AT 250 WORDS)