Respiratory muscle and pulmonary function in polymyositis and other proximal myopathies

We studied 53 patients with proximal myopathy to determine at what level of muscle weakness hypercapnic respiratory failure is likely, and which tests of pulmonary function or respiratory muscle strength would best suggest this development. Respiratory muscle strength was determined from maximal static efforts and in half the patients, both inspiratory and expiratory muscle strengths were less than 50% of normal. In the 37 patients without lung disease respiratory muscle weakness was accompanied by significant decreases in vital capacity, total lung capacity, and maximum voluntary ventilation; by significant increases in residual volume and arterial carbon dioxide tension (PaCO2); and greater likelihood of dependence on ventilators, atelectasis, and pneumonia. Hypercapnia was particularly likely when respiratory muscle strength was less than 30% of normal in uncomplicated myopathy, and when vital capacity was less than 55% of the predicted value in any patient.

Effect of body weight and muscularity on human diaphragm muscle mass, thickness, and area

To assess the consequences to the human diaphragm of alterations in body weight and muscularity, we measured the mass, thickness, area, and length of diaphragm muscle at necropsy. Of 33 subjects who were clinically well until sudden death, 27 had sedentary occupations and normal weight (group N), while 6 were nonobese laborers whose average weight was 40% greater than normal (group M). Among 37 patients dying of more prolonged illness, 23 were of normal weight (group W), while 14 weighed 71% of normal (group U). Subjects with obesity, chronic pulmonary disease, or edema were excluded. Disease per se did not significantly affect diaphragm dimensions. However, in group M diaphragm muscle mass, thickness, area, and length were 165, 129, 125, and 117% of normal (P less than 0.005), whereas in group U the corresponding values were 57, 73, 77, and 83% (P less than 0.001). Thus alterations in body weight and muscularity profoundly affect diaphragm muscle mass, causing a nearly threefold variation between muscular normal subjects and underweight patients.

Anthrax toxin lethal factor contains a zinc metalloprotease consensus sequence which is required for lethal toxin activity

Comparison of the anthrax toxin lethal factor (LF) amino acid sequence with sequences in the Swiss protein database revealed short regions of similarity with the consensus zinc-binding site, HEXXH, that is characteristic of metalloproteases. Several protease inhibitors, including bestatin and captopril, prevented intoxication of macrophages by lethal toxin. LF was fully inactivated by site-directed mutagenesis that substituted Ala for either of the residues (H-686 and H-690) implicated in zinc binding. Similarly, LF was inactivated by substitution of Cys for E-687, which is thought to be an essential part of the catalytic site. In contrast, replacement of E-720 and E-721 with Ala had no effect on LF activity. LF bound 65Zn both in solution and on protein blots. The 65Zn binding was reduced for several of the LF mutants. These data suggest that anthrax toxin LF is a zinc metallopeptidase, the catalytic function of which is responsible for the lethal activity observed in cultured cells and in animals.

Proteolytic activation of bacterial toxins by eukaryotic cells is performed by furin and by additional cellular proteases

Before intoxication can occur, anthrax toxin protective antigen (PA), Pseudomonas exotoxin A (PE), and diphtheria toxin (DT) must be activated by proteolytic cleavage at specific amino acid sequences. Previously, it was shown that PA and DT can be activated by furin. In Chinese hamster ovary (CHO) cells, wild-type (RKKR) and cleavage site mutants of PA, each administered with a modified form of anthrax toxin lethal factor (the N terminus of lethal factor fused to PE domain III), had the following potencies: RKKR (wild type) (concentration causing 50% cell death [EC50] = 12 ng/ml) > or = RAAR (EC50 = 18 ng/ml) > FTKR (EC50 = 24 ng/ml) > STRR (EC50 = 49 ng/ml). In vitro cleavage of PA and cleavage site mutants of PA by furin demonstrated that native PA (RKKR) and PA with the cleavage sequence RAAR are substrates for furin. To characterize eukaryotic proteases that play a role in activating bacterial toxins, furin-deficient CHO cells were selected after chemical mutagenesis. Furin-deficient cells were resistant to PE, whose cleavage site, RQPR, constitutes a furin recognition site and to all PA cleavage site mutants, but were sensitive to DT (EC50 = 2.9 ng/ml) and PA (EC50 = 23 ng/ml), whose respective cleavage sites, RKKR and RVRR, contain additional basic residues. Furin-deficient cells that were transfected with the furin gene regained sensitivity to PE and PA cleavage site mutants. These studies provide evidence that furin can activate the three toxins and that one or more additional proteases contribute to the activation of DT and PA.

Respiratory muscle failure

The diseases which are commonly complicated by hypercapnic respiratory failure also compromise the respiratory muscles in several ways. Increased work of breathing, mechanical disadvantage, neuromuscular disease, impaired nutritional status, shock, hypoxemia, acidosis, and deficiency of potassium, magnesium, and inorganic phosphorus are the major non-neurologic factors which contribute to respiratory muscle fatigue and failure. Respiratory muscle fatigue has two components. High frequency fatigue occurs rapidly with intense contractile efforts but is usually not severe. It also recovers rapidly with rest. Low frequency fatigue develops more slowly but is severe and requires hours for recovery. Since the spontaneous rate of neural stimulation is predominantly in the low frequency range, this component of fatigue is of particular clinical importance. Fatigue of the inspiratory muscles leads to acute respiratory acidosis, but before carbon dioxide retention occurs, it can be recognized from characteristic symptoms and signs. These include dyspnea which responds to mechanical ventilation, rapid shallow breathing, and asynchronous movements of the chest and abdomen. Inspiratory muscle fatigue must be treated by putting these muscles to rest, by mechanically supporting ventilation. In addition, underlying metabolic nutritional and circulatory abnormalities must be corrected and infection treated. Aminophylline and isoproterenol can restore inspiratory muscle contractility, but controlled clinical trials remain to be done regarding their application in acute and chronic respiratory failure. Inspiratory muscle training improves strength and endurance in patients with obstructive lung disease, cystic fibrosis, and spinal cord injury, but does not always improve physical exercise performance. Again, more work is needed to develop the indications for inspiratory muscle training and to determine the optimum type and duration of the training regimen.

Force-length relationship of the normal human diaphragm

To characterize the in vivo force-length relation of the human diaphragm, we related pressures during static inspiratory efforts (Pmus and Pdi, respiratory muscle and transdiaphragmatic pressures, respectively) to diaphragm lengths measured on chest X rays from 22 normal subjects. At total lung capacity, the intersection of diaphragm and chest wall contours corresponds to the anatomic junction of diaphragm and chest wall. This point is located by skeletal landmarks to reveal the entire diaphragm contour on films taken at lower lung volumes. To validate the X-ray measurements, corresponding diameters were measured on 32 normal diaphragms at necropsy. After correction for height and diaphragm position, in vivo and necropsy length estimates along the coronal section agreed within 9%. The diaphragm length-lung volume relation is curvilinear, with length increasing primarily in the portion of the diaphragm apposed to the chest wall. As length increases, Pmus and Pdi rise sharply then plateau, generally conforming to force-length behavior of isolated muscle. However, absence of a Pdi peak at presumed diaphragm resting length suggests that Pdi is submaximal during voluntary inspiratory effort.

Fusions of anthrax toxin lethal factor with shiga toxin and diphtheria toxin enzymatic domains are toxic to mammalian cells

To investigate the ability of anthrax toxin lethal factor (LF) to translocate foreign proteins into the cytosol of eukaryotic cells and to characterize the structural requirements of this process, fusion proteins containing a portion of LF and the catalytic domains of either diphtheria toxin or Shiga toxin were constructed. Previous work showed that residues 1 to 254 of anthrax toxin lethal factor (LF1-254) are sufficient for binding to the protective antigen component of the toxin and that portions of Pseudomonas exotoxin A fused to LF1-254 are efficiently translocated to the cytosol of eukaryotic cells (N. Arora and S. H. Leppla, J. Biol. Chem. 268:3334-3341, 1993). In this study, it was found that fusion proteins containing the ADP-ribosylation domain of diphtheria toxin fused at either the amino end or the carboxyl end of LF1-254 are highly toxic to Chinese hamster ovary (CHO) cells, indicating that translocation does not strictly require that the amino terminus of LF be free. A fusion protein containing the ribosome-inactivating A1 subunit of Shiga toxin fused to the carboxyl terminus of LF1-254 was also highly toxic for CHO cells. All fusion proteins were toxic only when administered with the anthrax toxin protective antigen component. The data show that the combination of protective antigen and LF fusion proteins can efficiently import polypeptides from diverse bacterial sources to the cytosol of eukaryotic cells and that LF fusion proteins may have the passenger polypeptides fused at either the amino terminus or the carboxyl terminus of LF1-254. These LF fusion proteins could potentially be used as components of a therapeutic agent when the destruction of certain types of cells is desired (e.g., in treating cancer).

Identification of a serine protease as a major allergen (Per a 10) of Periplaneta americana

BACKGROUND

Cockroach allergens are associated with the development of asthma, but none of these has been characterized for proteolytic activity. This study was undertaken to isolate and characterize a protease from Periplaneta americana and determine its allergenicity.

METHODS

A serine protease was isolated from P. americana extract using benzamidine sepharose column and characterized by immunobiochemical methods. Allergenicity of the protease was assessed by enzyme-linked immunosorbent assay, immunoblot, intradermal testing, histamine release and peripheral blood mononuclear cells (PBMCs) proliferation.

RESULTS

Affinity purified protein of approximately 28 kDa (Per a 10) showed a single band of activity in gelatin zymogram and agarose plate assay. N-terminal sequence (IVGGRPAQI) revealed similarity with mite serine protease allergens and insect trypsins. It demonstrated proteolytic activity with azocollagen > gelatin > defatted-milk > casein including serine protease specific substrate, N-benzoyl-arginine-ethyl-ester-hydrochloride. It was inhibited by serine protease inhibitors, namely aprotinin > pefabloc > AEBSF > PMSF > benzamidine > antipain > leupeptin and trypsin-specific inhibitor (tosyl-lysyl-chloromethyl-ketone) suggesting it to be a trypsin-like serine protease. Per a 10 was recognized as a major allergen, showing IgE reactivity with >80% of cockroach sensitized patients by skin tests and immunoblot. It could induce significant histamine release (P < 0.05) in blood and secretion of interleukin-4 (IL-4) (P < 0.05) and IL-5 (P < 0.05) in culture supernatant of PBMCs from cockroach hypersensitive patients, suggesting a strong allergenic potency.

CONCLUSION

A serine protease isolated from P. americana was demonstrated to be a major allergen (Per a 10). It has a potential for component-based diagnosis of allergy and will be useful in elucidating the mechanism of allergy.

Targeting HIV proteins to the major histocompatibility complex class I processing pathway with a novel gp120-anthrax toxin fusion protein

A challenge for subunit vaccines whose goal is to elicit CD8(+) cytotoxic T lymphocytes (CTLs) is to deliver the antigen to the cytosol of the living cell, where it can be processed for presentation by major histocompatibility complex (MHC) class I molecules. Several bacterial toxins have evolved to efficiently deliver catalytic protein moieties to the cytosol of eukaryotic cells. Anthrax lethal toxin consists of two distinct proteins that combine to form the active toxin. Protective antigen (PA) binds to cells and is instrumental in delivering lethal factor (LF) to the cell cytosol. To test whether the lethal factor protein could be exploited for delivery of exogenous proteins to the MHC class I processing pathway, we constructed a genetic fusion between the amino-terminal 254 aa of LF and the gp120 portion of the HIV-1 envelope protein. Cells treated with this fusion protein (LF254-gp120) in the presence of PA effectively processed gp120 and presented an epitope recognized by HIV-1 gp120 V3-specific CTL. In contrast, when cells were treated with the LF254-gp120 fusion protein and a mutant PA protein defective for translocation, the cells were not able to present the epitope and were not lysed by the specific CTL. The entry into the cytosol and dependence on the classical cytosolic MHC class I pathway were confirmed by showing that antigen presentation by PA + LF254-gp120 was blocked by the proteasome inhibitor lactacystin. These data demonstrate the ability of the LF amino-terminal fragment to deliver antigens to the MHC class I pathway and provide the basis for the development of novel T cell vaccines.

Passive cutaneous anaphylaxis in mouse skin is associated with local accumulation of interleukin-6 mRNA and immunoreactive interleukin-6 protein

We used a BALB/c model of passive cutaneous anaphylaxis (PCA), an IgE-mediated, mast cell-dependent reaction, to demonstrate the early production of the proinflammatory cytokine interleukin-6 (IL-6) mRNA and protein product. Northern blot analysis detects IL-6 mRNA 1, and 2 hours after antigen challenge (dinitrophenyl30-40 human serum albumin [DNP30-40-HSA]) and in situ hybridization reveals that it is primarily cells with round-to-oval nuclei within the dermis (1 to 3 per high-power field) expressing IL-6 mRNA. Immunohistochemistry revealed perinuclear and cytoplasmic staining for immunoreactive IL-6 in mononuclear dermal cells and also cells within the basal keratinocyte layer. Injection of recombinant murine IL-6 (rmIL-6) either systemically or locally during antidinitrophenyl IgE skin sensitization resulted in increased vasopermeability at the PCA site after DNP30-40-HSA. However, this increased permeability was not associated with a change in the character of the cellular infiltrate at the PCA site 8 hours later. Although the specific role of IL-6 in the generation of the allergic response remains unknown, its detection during PCA unequivocally demonstrates that IL-6 be considered one of the mediators identified in inflammation that follows allergic reactions.

Toxicity analysis of N- and C-terminus-deleted vegetative insecticidal protein from Bacillus thuringiensis

A vegetative insecticidal protein (VIP)-encoding gene from a local isolate of Bacillus thuringiensis has been cloned, sequenced, and expressed in Escherichia coli. The expressed protein shows insecticidal activity against several lepidopteran pests but is ineffective against Agrotis ipsilon. Comparison of the amino acid sequence with those of reported VIPs revealed a few differences. Analysis of insecticidal activity with N- and C-terminus deletion mutants suggests a differential mode of action of VIP against different pests.

Respiratory muscle strength and maximal voluntary ventilation in undernourished patients

To assess the effect of chronic debilitation on respiratory muscle function, we studied 16 poorly nourished (PN) patients without pulmonary disease, and 16 well-nourished (WN) subjects matched for age and sex. Body weight, vital capacity (VC), maximal voluntary ventilation (MVV), and maximal static inspiratory and expiratory pressures (PImax and PEmax) were measured and expressed as percent predicted. Respiratory muscle strength (RMS) was calculated as (% PImax + % PEmax)2. Body weight was 71% predicted in the PN group and 104% in the WN group. The RMS, MVV, and VC were 37%, 41%, and 63%, respectively, of the values in the WN group (p less than 0.001). The 60% reduction in RMS was shared almost equally among inspiratory and expiratory muscles, and PEmax was linearly related to body weight. Because malnutrition reduces both respiratory muscle strength and MVV, it may well impair respiratory muscle capacity to handle increased ventilatory loads in thoracopulmonary disease.

Cough dynamics during progressive expiratory muscle weakness in healthy curarized subjects

The dynamics of voluntary cough were studied in healthy supine subjects during four successive infusions of d-tubocurarine (dTc) (0.05 mg/kg) to assess the effects of progressive expiratory muscle weakness on cough performance. Curarization produced a progressive decline in maximal static expiratory muscle strength (PEmax) measured at the mouth and in pleural pressures (Ppl) generated during coughing. Expiratory flow rates during coughing did not decrease except during the initial cough from total lung capacity with the last dTc dose (18% below control). This was associated with a decrease in end-inspiratory volume prior to coughing and with a marked decrease in Ppl to 30% of control. Although the decrease in flow rates was minimal compared with Ppl, flow patterns suggest that dynamic airway compression was reduced during these coughs. We conclude that the principal effect of the expiratory muscle weakness in curarized subjects is to reduce the cough-induced dynamic compression and linear velocity of airflow though the major intrathoracic airways.

Choline supplementation reduces oxidative stress in mouse model of allergic airway disease

BACKGROUND

Asthma is a multi-factorial inflammatory disease associated with increased oxidative stress and altered antioxidant defences. We have evaluated the effect of choline on oxidative stress in a mouse model of airway disease.

MATERIALS AND METHODS

Balb/c mice were sensitised with 100 microg of ovalbumin on days 0 and 14, and challenged with aerosolized ovalbumin on days 25-27. Mice were administered 1 mg kg(-1) of choline via oral gavage or intranasal route on days 14-27. Mice were also administered 100 mg kg(-1) of alpha-lipoic acid as standard antioxidant. Total cell counts, eosinophils and eosinophil peroxidase (EPO) activity were determined in bronchoalveolar lavage (BAL) fluid. Reactive oxygen species (ROS), lipid peroxidation and isoprostanes levels were measured in BAL fluid. IL-13 and tumour necrosis factor-alpha (TNF-alpha) levels were also measured in BAL fluid and spleen cell culture supernatant. Nuclear factor kappaB (NFkappaB) p65 protein expression was measured after last ovalbumin challenge in nuclear and cytosolic extracts of lungs.

RESULTS

Compared with ovalbumin-challenged mice, choline and alpha-lipoic acid treated mice had significantly reduced eosinophilic infiltration and EPO activity in BAL fluid. Choline and alpha-lipoic acid treatment reduced ROS production and isoprostanes level significantly in BAL fluid and thus suppressed oxidative stress. Choline and alpha-lipoic acid administration by either route decreased lipid peroxidation levels and down regulated NFkappaB activity. Further, choline and/or alpha-lipoic acid treatment suppressed TNF-alpha level significantly as compared with that of ovalbumin-challenged mice.

CONCLUSIONS

Choline administration reduces oxidative stress possibly by modulating the redox status of the cell and inhibits inflammatory response in a mouse model.

Sensitization to blackgram in patients with bronchial asthma and rhinitis: clinical evaluation and characterization of allergens

BACKGROUND

Legumes are important causative agents of type I hypersensitivity in south Asia and Europe but such studies are lacking in Indian population. The present study investigates blackgram sensitization in asthma and rhinitis patients and identifies immunoglobulin E (IgE)-binding proteins.

METHODS

Respiratory allergy patients were evaluated using standard questionnaire and skin prick tests (SPT) with common foods and aeroallergens. Blackgram-specific IgE level was estimated by enzyme-linked immunosorbent assay (ELISA) and sensitization was established by a double-blind, placebo-controlled food challenge (DBPCFC). The cross-reactivity of blackgram with other legumes was studied by immunobiochemical methods.

RESULT

Of 816 patients, 35 gave history of blackgram hypersensitivity. From these, 16 patients were SPT positive and 14 showed elevated specific IgE (three times of negative control) to blackgram. DBPCFC established blackgram sensitivity in four of 14 patients. Immunoblotting with individual patient's sera recognized eight most prevalent allergens of 78, 56, 47, 43, 40, 30, 28 and 16 kDa. Roasted blackgram showed six major allergens whereas 47, 43 and 28 kDa proteins retained IgE reactivity upon boiling. Blackgram extract required 14 ng of self protein for 50% ELISA inhibition whereas roasted and boiled blackgram required 16 and 120 ng protein. ELISA and immunoblot inhibition show partial inhibition to blackgram proteins by lentil, limabean and pea.

CONCLUSION

Blackgram induces IgE-mediated reactions in 1.7% of asthma and rhinitis patients and contains eight major IgE-binding components, of which six retained IgE reactivity after roasting. Blackgram shares allergenicity with lentil and limabean.

Serine protease activity of Per a 10 augments allergen-induced airway inflammation in a mouse model

BACKGROUND

We recently reported an immunodominant serine protease allergen (Per a 10) from Periplaneta americana. This study investigates the role of its proteolytic activity in driving the immune responses towards self and other allergens.

MATERIALS AND METHODS

Groups of Balb/c mice were sensitized intraperitoneally and subcutaneously with proteolytically active Per a 10 or inactivated Per a 10 (using aminoethyl benzenesulfonyl fluoride hydrochloride) or whole body P. americana extract and subsequently challenged intranasally with the respective antigens. Mice were also sensitized and challenged with ovalbumin (OVA) alone or co-administered with active or inactive Per a 10. The immune-inflammatory responses were measured by airway hyperresponsiveness (AHR) and cellular infiltration of lungs i.e. eosinophil counts, eosinophil peroxidase (EPO) activity, myeloperoxidase activity (MPO), lung histopathology, serum levels of specific-antibodies and levels of Th1/Th2 interleukins in bronchoalveolar lavage fluid (BALF) and in spleen cells culture supernatant.

RESULTS

Mice challenged with active Per a 10/P. americana extract showed a significant airway inflammation demonstrated by enhanced AHR and increased cellular infiltration of lungs as evidenced by high eosinophil counts, EPO activity, IL-4 and IL-5 in BALF. Active Per a 10 also induced a significant proliferation of spleen cells, increased secretion of IL-4 and IL-5 in the spleen cells culture supernatant and systemic production of specific-IgE and IgG1. However, exposure with inactive Per a 10 elicited a low cellular infiltration and systemic antibody production. Exposure to OVA with active Per a 10 demonstrated a significantly high cellular infiltration and production of OVA-specific IgE and IgG1, than exposure to OVA alone or with inactive Per a 10.

CONCLUSIONS

Proteolytic activity of Per a 10 plays an important role in driving the allergic immune response by providing an adjuvant effect, towards self and other potential allergens present in the same microenvironment.

Anthrax toxin fusion proteins for intracellular delivery of macromolecules

The dominant role played by the anthrax toxin in Bacillus anthracis pathogenesis shows that the toxin has evolved to be an efficient system for delivering its two catalytic protein components, oedema factor and lethal factor (LF), into the cytosol of host cells. This system involves binding of the protective antigen (PA) toxin component to a ubiquitous (and still unidentified) receptor, proteolytic activation at the cell surface, internalization by endocytosis and translocation through an early endosome membrane to the cytosol (Leppla 1995). We and colleagues showed that the system can be exploited to deliver heterologous polypeptides to the cytosol (Arora et al. 1992; Milne et al. 1995). This work used the catalytic domains of other toxins which are normally translocated across membranes (Arora & Leppla 1994). Immunity to intracellular pathogens depends on the cytosolic processing of antigens to produce peptides that are presented on the cell surface bound to MHC Class I molecules. The anthrax toxin delivery system provides a way to mimic this process. We made a fusion protein containing the (non-catalytic) amino terminal domain of LF and the gp120 envelope glycoprotein of HIV-1. Administration of this recombinant protein along with PA to antigen-presenting cells sensitized them to cytolysis by cytotoxic T-cells specific to gp120 peptides (Goletz et al. 1997). Further exploitation of the anthrax toxin system as a cell-targeting reagent would be facilitated by achieving cell type specificity. The recent determination of the PA structure (Petosa et al. 1997) allows rational engineering to modify or replace the receptor-binding domain with specific ligand structures. A model system was produced by fusing a c-Myc peptide to the carboxyl terminus of PA so as to target hybridoma cells expressing cell surface antibodies to this peptide. Killing of the hybridoma cells was shown to be specific by competition with the peptide and with non-toxic mutants of PA (Varughese et al. 1998).

Allergenicity assessment of transgenic mustard (Brassica juncea) expressing bacterial codA gene

BACKGROUND

Assessing the allergenicity and toxicity of genetically modified (GM) crops is essential before they become a regular part of our food supply. The present study aimed to assess the allergenicity of Brassica juncea (mustard) expressing choline oxidase (codA) gene from Arthrobacter globiformis that provides resistance against abiotic stresses.

METHODS

SDAP, Farrp, and Swiss-Prot databases were used to study allergenicity of choline oxidase. Digestibility of choline oxidase was assessed in simulated gastric fluid (SGF). Specific immunoglobulin E (IgE) reactivity of native and GM mustard was compared by using enzyme-linked immunosorbent assay (ELISA) and skin tests in respiratory-allergic patients. Allergenicity of GM and native mustard proteins was compared in Balb/c mice.

RESULTS

Choline oxidase showed no significant homology with allergenic proteins in SDAP and Farrp databases. Cross-reactive epitope search showed a stretch similar to Hev b 6 having some antigenic properties. Purified choline oxidase showed complete degradation with SGF. Skin prick test of native and GM mustard extract on respiratory allergic patients showed significant correlation (P < 0.05). ELISA with 96 patients' sera showed comparable IgE reactivity. Balb/c mice immunized with native and GM mustard proteins showed low IgE response. Presensitized mice on intravenous challenge with Brassica extract showed no anaphylactic symptoms unlike ovalbumin (OVA) sensitization that showed anaphylactic reaction in mice. Lung histology of OVA-sensitized mice showed narrowing of airway and large eosinophilic infiltration, whereas native and GM Brassica extract showed normal airway.

CONCLUSION

Genetically modified mustard with the codA gene possessed allergenicity similar to that of native mustard and no enhancement of IgE binding was observed due to genetic manipulation.

Portal hypertension in north Indian children

Etiological factors associated with portal hypertension in children influence the decision about therapy and the prognosis. This cross-sectional observational study was performed at a tertiary care centre in northern India from January, 1990 to December, 1994. Children below the age of 14 years with suspected portal hypertension were prospectively assembled into a cohort to determine the etiology and clinical profile of portal hypertension. Of the 115 patients with portal hypertension, 76.5% had extrahepatic portal hypertension (EHPH). Remaining 23.5% of the cases had intrahepatic and post-hepatic causes of portal hypertension. Children with EHPH had a significantly earlier onset of symptoms as compared to those with intrahepatic portal hypertension (p = 0.002) and bled significantly more frequently (p = 0.00). Forty per cent of patients with chronic liver disease (CLD) never had jaundice. History suggestive of potential etiological factors could be elicited in only 7% of EHPH patients. The commonest site of block in splenoportal axis was at the formation of the portal vein. An inverse relation of bleeding rates with duration of illness was seen in EHPH. Of the 10 CLD patients in whom liver biopsy could be done, cirrhosis was present in 6 patients. Understanding the natural history of EHPH and portal hypertension due to other etiologies may have significant implications in choosing the appropriate intervention and predicting the outcome.

Identification of serine protease as a major allergen of Curvularia lunata

BACKGROUND

Several proteins from Curvularia lunata have been identified as important fungal allergens. It will be worthwhile to study the functional aspects of these allergens. The present study aimed at purifying a major allergen and determining its biological function.

METHODS

Concanavalin A and Superdex 75 were used to purify Cur l 1 major allergen from C. lunata. Cur l 1 activity was determined qualitatively and quantitatively. Serine protease inhibitors and specific substrate was used to determine the biological function of the protein.

RESULTS

Concanavalin A-bound fraction showed five allergenic proteins, which on Superdex G-75 purification gave a homogenous Cur l 1 protein. Cur l 1 showed IgE reactivity with 80% of the C. lunata hypersensitive patient's sera indicating it to be a major allergen. It showed protease activity on different substrates. Cur l 1's amino terminal sequence, GLTQKSAPWGLGADTIVAVELDSY, showed homology with the alkaline serine protease precursor. Phenylmethylsulfonylfluoride, pefabloc, aprotinin and leupeptin inhibited 70-80% enzymatic activity of Cur l 1 and no inhibition was observed with ethylenediaminetetraacetic acid (EDTA). A dose-dependent hydrolysis of Nalpha-benzoyl-l-arginine ethyl ester-hydrochloride, a specific serine protease substrate was obtained with Cur l 1.

CONCLUSION

A major glycoprotein allergen Cur l 1 was purified to homogeneity from C. lunata. Amino terminal sequence and biochemical assays identified it as a serine protease.