Allergenic and antigenic activity of peptide fragments in a whey hydrolysate formula

BACKGROUND: Milk hydrolysates, although frequently used as substitutes in cases of cow's milk allergy, show a reduced but never a complete abolishment of antigenicity and allergenicity. OBJECTIVE: Our purpose was to determine the lower molecular weight limit of peptides to elicit skin reactions and to bind IgE antibodies in vitro. METHODS: Using FPLC, an ultrafiltrated whey hydrolysate, was fractionated in different molecular weight fractions. Skin-prick tests were performed with the hydrolysate and its fractions in five cow's milk allergic children, and RAST inhibition tests were done using the serum of these children. RESULTS: On the basis of the lowest extinction values between two peaks of the chromatogram, seven fractions with molecular weights between 15000 and 125 Da were obtained. Peptides of > 2600 Da elicited a clearly positive skin reaction and inhibited IgE-binding, while peptides of < 1400 Da did not give any positive skin reaction but were still able to inhibit to a small extent IgE-binding to the hydrolysate. CONCLUSION: Our findings suggest that for skin reactivity peptides of > 1400 Da are needed. The minimal molecular mass for IgE binding in vitro appears to be situated between 1400 and 970 Da. Such peptides might be used to develop a safe formula for patients reacting to milk hydrolysates or even for tolerance induction.     

The whey proteins of the milk of red deer (Cervus elaphus L.). A homologue of bovine beta-lactoglobulin

Increasing plasma free fatty acids decreased the degree of glycogen depletion, and increased the citrate concentration, in slow-red (soleus) and fast-red (deep portion of vastus lateralis) muscle during exercise (approx. 50% depletion of glycogen, as against 75% in control animals). There was no effect in fast-white muscle (superficial portion of vastus lateralis). Glycogen concentration in the liver decreased by 83% in controls, but only by 23% in animals with increased free fatty acids during exercise. The decreased glycogen depletion may be partly explained by the findings that (a) plasma-insulin concentration was two- to three-fold higher in animals with increased plasma free fatty acids and (b) the exercise-induced increase in plasma glucagon was lessened by increased free fatty acids. Blood glucose was higher in the animals with increased free fatty acids after the exercise. The rats with increased plasma free fatty acids utilized approx. 50% as much carbohydrate as did the controls during the exercise.     

Expression of bovine beta-lactoglobulin/human erythropoietin fusion protein in the milk of transgenic mice and rabbits

We have generated several transgenic mouse lines and rabbits expressing efficiently (up to 0.3 mg/ml in mice and up to 0.5 mg/ml in rabbits) human erythropoietin in their milk as bovine beta-lactoglobulin fusion protein. Human erythropoietin cDNA was inserted in frame into exon 5 of the bovine beta-lactoglobulin gene with a linker oligonucleotide encoding the cleavage site for bacterial IgA protease. RNA analysis performed on one lactating transgenic mouse and one transgenic rabbit revealed that the fusion gene was expressed almost exlusively in the mammary gland, although low amounts of transgene-derived RNA were detectable in salivary glands and uterus or in the kidney. The fusion protein was specifically cleaved with IgA protease. The erythropoietin part obtained upon digestion had a lower molecular mass than recombinant erythropoietin produced in Chinese hamster ovary cells. By deglycosylation analysis it was shown that the difference in size was due to a different type of glycosylation. Biological activity of the fusion protein, as determined by growth stimulation of TF-1 erythroleukemia cells, was less than 15% of that of human recombinant erythropoietin. Upon digestion of the fusion protein with IgA protease, biological activity comparable to that of the recombinant erythropoietin was recovered. Transgenic males and virgin females did not show signs of enhanced erythropoiesis, but lactating females expressing the transgene displayed transient increases in their hematocrit values.     

Allergy to the heat-labile proteins alpha-lactalbumin and beta-lactoglobulin in mare's milk

BACKGROUND: Allergy to mare's milk is rare. Recently, however, mare's milk has been recommended for treatment of various ailments by practitioners of "alternative medicine," and it is available in health food stores. OBJECTIVE: We report a case of allergic reaction to mare's milk in a 51-year-old woman who was able to tolerate cow's milk. METHODS: The protein composition of mare's milk was determined by methods based on measurement of nitrogen content. The patient underwent prick and intracutaneous tests with commercially available bovine milk proteins and several mare's milk preparations, including mare's milk granulate and boiled mare's milk. RAST and immunoblotting were also performed. RESULTS: Results of skin testing and RAST with cow's milk were negative but demonstrated an IgE-mediated allergy to mare's milk. Immunoblotting revealed two allergen bands with molecular weights of 16 and 18 kd, most likely representing the whey proteins alpha-lactalbumin and beta-lactoglobulin. The bands disappeared after the mare's milk was boiled, indicating that the proteins are heat-labile. CONCLUSION: The results of this study demonstrate the existence of an IgE-mediated mare's milk allergy caused by low molecular weight heat-labile proteins, most likely alpha-lactalbumin and beta-lactoglobulin, which do not cross-react with the corresponding whey proteins in cow's milk.     

Characterization by ionization mass spectrometry of lactosyl beta-lactoglobulin conjugates formed during heat treatment of milk and whey and identification of one lactose-binding site

The extent of the early stage of the Maillard-type reaction that impaired functional properties of whey proteins was evaluated by electrospray ionization mass spectrometry. Under conditions of mild heat treatment (63 degrees C for 20 s) applied to milk before whey separation at room temperature 23 degrees C), a modification of the relative molecular mass of beta-lactoglobulin (beta-LG) was observed that differed from that of the native form by 324. This specific modification of beta-LG occurred in acidified whey as well as in sweet whey and increased with the extent of the heat treatment. Incubation of purified beta-LG dissolved in milk ultrafiltration permeate or in lactose solution at 50 to 80 degrees C demonstrated the presence of a lactosyl residue that was covalently bound to beta-LG; beta-casein, used as a control, showed no mass modification. Studies of kinetics showed that a maximum of 35% of the beta-LG was lactosyl-beta-LG conjugate after heat treatment at 70 degrees C for 1 h. This study provides the first direct evidence of specific lactosylation of beta-LG during the initial stage of the Maillard reaction. One of the first lactose-binding sites was identified as a Lys47 by protease mapping and analysis by means of on-line liquid chromatography combined with mass spectrometry. In addition, collision-activated dissociation performed on the lactosylated peptide beta-LG (f 46-51) showed the rearrangement reactions occurring during the fragmentation process by electrospray. A mechanism is proposed.     

Transgenic mice secreting coronavirus neutralizing antibodies into the milk

Ten lines of transgenic mice secreting transmissible gastroenteritis coronavirus (TGEV) neutralizing recombinant monoclonal antibodies (rMAbs) into the milk were generated. The rMAb light- and heavy-chain genes were assembled by fusing the genes encoding the variable modules of the murine MAb 6A.C3, which binds an interspecies conserved coronavirus epitope essential for virus infectivity, and a constant module from a porcine myeloma with the immunoglobulin A (IgA) isotype. The chimeric antibody led to dimer formation in the presence of J chain. The neutralization specific activity of the recombinant antibody produced in transiently or stably transformed cells was 50-fold higher than that of a monomeric rMAb with the IgG1 isotype and an identical binding site. This rMAb had titers of up to 10(4) by radioimmunoassay (RIA) and neutralized virus infectivity up to 10(4)-fold. Of 23 transgenic mice, 17 integrated both light and heavy chains, and at least 10 of them transmitted both genes to the progeny, leading to 100% of animals secreting functional TGEV neutralizing antibody during lactation. Selected mice produced milk with TGEV-specific antibody titers higher than 10(6) as determined by RIA, neutralized virus infectivity by 10(6)-fold, and produced up to 6 mg of antibody per ml. Antibody expression levels were transgene copy number independent and integration site dependent. Comicroinjection of the genomic beta-lactoglobulin gene with rMAb light- and heavy-chain genes led to the generation of transgenic mice carrying the three transgenes. The highest antibody titers were produced by transgenic mice that had integrated the antibody and beta-lactoglobulin genes, although the number of transgenic animals generated does not allow a definitive conclusion on the enhancing effect of beta-lactoglobulin cointegration. This approach may lead to the generation of transgenic animals providing lactogenic immunity to their progeny against enteric pathogens.     

High-efficiency retrovirus-mediated gene transfer into the livers of mice

Recombinant retroviral vectors represent an attractive means of transferring genes into the liver because they integrate in the host cell genome and result in permanent gene expression. However, efficient gene transfer is limited by the requirement of active cell division for integration. Surgical partial hepatectomy has been the traditional method of inducing hepatocellular proliferation, but this invasive approach would be difficult to justify in clinical gene therapy. As an alternative, we used a recombinant adenovirus expressing a nonsecreted form of urokinase plaminogen activator (Ad.PGKmuPA), which results in liver regeneration over a period of 8 days. When a high-titer retroviral vector was continuously infused into the portal vein of mice during this period of hepatocyte proliferation, 33.5% of hepatocytes were stably transduced. In addition, high-level expression of a secreted transgene reporter was sustained for at least 48 weeks (length of experiment). We investigated the influence of vector titer on the in vivo transduction efficiency in our system, and found that the total number of infectious retroviral particles delivered per target cell is a critical factor. The results presented here demonstrate the ability to obtain a high gene transfer efficiency and long-term gene expression in hepatocytes in vivo without the need for surgical hepatectomy. The two-vector system described here may be of clinical relevance, as the level of hepatic gene transfer achieved has potential to be curative for a large number of genetic liver diseases.     

Prevention of peroxidative stress in rats fed on a low vitamin E-containing diet by supplementing with a fermented bovine milk whey preparation: effect of lactic acid and beta-lactoglobulin on the antiperoxidative action

We examined the antiperoxidative properties of a fermented bovine milk whey preparation in rats fed on a low vitamin E-containing diet and identified the active principle in the preparation. An exogenous supply of either lactic acid or an amino acid mixture simulated the unfermented whey proteins to prevent red blood cell (RBC) hemolysis and to lower liver thiobarbituric acid reactive substances (TBARS). The supply of either whey proteins or beta-lactoglobulin resulted in an increase in liver GSH and prevented iron-mediated lipoprotein peroxidation. These protein effects were reproduced in rats orally administered with either GSH or its precursor, gamma-glutamylcysteine. The amount of TBARS formed during in vitro lipoprotein peroxidation were positively correlated with liver TBARS. These results suggest that fermented milk products containing lactic acid and bovine milk whey proteins can ameliorate peroxidative stress in tissues subjected to vitamin E deficiency.     

A comparative evaluation of whey hydrolysate and whey-predominant formulas. How well do infants accept and tolerate them?

Whey hydrolysate formulas are a recent and important innovation in infant feeding. This study compared clinical tolerance and acceptability of a whey hydrolysate formula (WH) with those of a whey-predominant formula (WF) in 45 infants. Four infants (16%) who refused to drink WH formula were eliminated from the study. Mean volume intake was significantly lower for WH (120 mL/kg/day) than for WF (147 mL/kg/day; P < .001). Consequently, mean caloric intake was also significantly different: 80 kcal/kg/day (WF) vs 97 kcal/kg/day (WF; P < .001). Nevertheless, weight gain from birth to 13 weeks of age was nearly identical in both groups (171% for WH vs 178% for WF). No significant differences were noted in duration of feeding, number of pauses during feeding, number of stools per day, or number of regurgitations per day. The lower rate of caloric intake and the dropout rate of 16% for WH raise questions about the use of WH formula in normal infants, as has become the case in some Western European regions.     

Expression, purification and immunochemical characterization of recombinant bovine beta-lactoglobulin, a major cow milk allergen

The immunological characteristics of a recombinant beta-lactoglobulin were studied using monoclonal antibodies, polyclonal antiserum and sera from allergic patients. Recombinant beta-lactoglobulin (rBLG) was expressed in Escherichia coli strain DH5alpha and purified as described previously [Cho et al. (1994) J. Biol. Chem. 269, 11 102-11 107]. The method has been modified by adding an immunoaffinity purification step. A quantity of 5-10mg of purified rBLG per liter of medium culture can be produced. rBLG shared the same molecular weight as the natural BLG (nBLG) and also possessed at least one intrachain disulfide bridge. In HPLC, rBLG appeared as a single peak, and the purity was estimated to be greater than 95%. All the monoclonal antibodies (mAbs) used in this study recognized different epitopes of the BLG and presented compatible binding. No differences could be detected between rBLG and nBLG when tested in a Western blot with rabbit polyclonal antiserum or with three mAbs that bound preferentially the reduced and S-carboxymethylated form of BLG. In a competitive enzyme immunoassay (EIA) using either a rabbit polyclonal antiserum or four mAbs that recognized conformational epitopes, we could not distinguish between rBLG or nBLG. In direct ELISA using nBLG or rBLG as the immobilized allergen, we measured a similar concentration of specific anti-BLG IgE in five sera from allergic patients. The results of this study indicate that we have obtained a rBLG with biochemical and immunological properties very similar to nBLG.     

从长水口吹入氩气对中包钢液传输行为的影响

为考察从长水口吹人氩气对中包内钢液流动行为的影响,采用数学和物理模拟的方法对中包内高湍流区流场、气体体积分布和停留时间曲线进行了测定,结果表明：从长水口吹人气体改变了高湍流区的流体流动特征,减弱了钢流对中包底部的冲击,但对示踪剂的停留时间没有明显的影响。     

LacZ gene transfer into tumor cells abrogates tumorigenicity and protects mice against the development of further tumors

Numerous studies have shown that the expression of immuno-stimulatory genes in tumor cells can result in the development of antitumoral immunity resulting in the rejection of the tumor cells. We show here that the simple integration and expression of the lacZ gene in the highly tumorigenic murine mastocytoma cell line P815 strongly reduces the cell's tumorigenicity. All the animals having rejected P815-lacZ challenges develop a long-lasting immunity against unmodified P815 cells with all of the animals rejecting further challenges with tumorigenic doses of P815 cells. However, this protective immunity conferred by P815-lacZ, directed against both the nuclearly expressed lacZ and surface tumor antigens, is not sufficient to act as curative immunity. In this immunogenic tumor model the expression of the lacZ antigen is more efficient than the irradiation of the cells to induce a strong immune response and an antitumoral state of vaccination in syngeneic animals.     

Effect of psychrotrophic microorganisms on the plasmin system in milk

The psychrotrophic bacteria that are present in raw milk produce heat-stable proteases that affect the plasmin system and, in turn, the quality of the processed milk and other dairy products. Three bacterial strains, Pseudomonas spp. SRM21A and SRM28A and Pseudomonas fluorescens M3/6, were inoculated at a level of approximately 10(3) cfu/ml into reconstituted nonfat dry milk and incubated at 4 degrees C for up to 9 d. From each sample, casein and whey fractions were obtained and electrophoresed to visualize protein hydrolysis and plasmin activity. Colorimetric assays were used to quantify plasmin-related activities. The casein SDS-PAGE gels showed that, by 5 d of incubation, caseinolytic activity was visible in whey fractions of all three strains at the same molecular mass range as commercial bovine plasmin, which was used as a control. Colorimetric assays indicated that plasmin activity in the casein samples decreased as incubation time increased; plasmin activity in the whey samples increased, peaking at 5 to 7 d. Plasminogen activity decreased over time in the casein fraction and increased in the whey fraction. Protein immunodetection indicated crossreactivity between anti-bovine plasminogen and the plasmin and plasminogen from whey samples collected at 5 and 7 d from the incubated milk. The growth of the Pseudomonas strains tested and their concomitant production of proteases caused the release of plasmin and plasminogen from the casein micelle into the whey fraction.     

Effect of saponin on the transmucosal passage of beta-lactoglobulin across the proximal small intestine of normal and beta-lactoglobulin-sensitised rats

The ability of saponins and glycoalkaloids to permeabilise the mammalian intestinal barrier has been previously demonstrated in vitro, leading to the hypothesis that membranolytic saponins may facilitate transfer to the tissues of otherwise excluded macromolecules. An enhanced uptake of, for instance, potentially allergenic species from the lumen is one of the factors that may affect the induction of food allergy, and its presentation in already sensitised individuals. In the experiments described here, an increase in the transmucosal uptake of the milk allergen beta-lactoglobulin (beta LG) was assessed in non-sensitised and sensitised Brown Norway rats in the presence of Gypsophila saponin. Isolated jejunal loops were exposed in vivo to either beta LG followed by saponin, saponin followed by beta LG or the two compounds simultaneously. Portal vein blood samples were collected and assayed for beta LG and rat mucosal mast cell protease (RCMP II) activity. Mucosal tissue was also examined histologically and assayed for histamine content. Sham-operated animals, exposed to physiological buffer alone, were included as controls and beta LG measurements corrected for this component which was negligible. No transfer of beta LG occurred in the absence of saponin in non-sensitised rats, whereas a significant enhancement was observed in the presence of saponin. beta LG was detected in the portal circulation of sensitised rats exposed to beta LG alone; however addition of saponin to the intestinal lumen further enhanced this uptake, possibly by an independent mechanism. Histological examination of the mucosal epithelium exposed to saponin revealed damage, especially at the villus tips. Mucosal histamine and serum RCMP II concentrations were consistent with the differences observed between sensitised and non-sensitised animals. It is concluded that exposure to food constituents capable of permeabilising the mucosal epithelium may increase the risk of sensitisation to dietary antigens.     

Lactation duration: influences of human milk replacements and formula samples on women planning postpartum employment

The authors evaluated the adsorption loss of tricyclic antidepressants in analytical procedures with solvent extraction and evaporation. In standard procedures with the use of triple solvent extraction between alkalinized and acidified samples before chromatographic analysis, the adsorption loss was more significant with the demethylated metabolites. As much as 50% adsorption loss can occur; this irreversible loss can be accounted for entirely during the solvent evaporation step. Because of differential adsorption loss among parent drugs, metabolites, and internal standards, the analytical methods usually had wide within-day and day-to-day variations. The authors found that the addition of as little as 0.05% diethylamine to the extract before evaporation completely eliminated the adsorption loss of amitriptyline-nortriptyline, imipramine-desipramine, and doxepin-desmethyldoxepin. with subsequent improvement in procedure performance. This simple modification can be adopted readily by all laboratories that use solvent extraction and subsequent chromatographic analysis of tricyclic antidepressants.     

A randomised multicentre study of human milk versus formula and later development in preterm infants

Whether breast milk influences later neurodevelopment has been explored in non-randomised studies, potentially confounded by social and demographic differences between feed groups. Here in a strictly randomised prospective multicentre trial, Bayley psychomotor and mental development indices (PDI and MDI) were assessed at 18 months postterm in survivors of 502 preterm infants assigned to receive, during their early weeks, mature donor breast milk or a preterm formula. These diets were compared as sole enteral feeds or as supplements to the mother's expressed breast milk. No differences in outcome at 18 months were seen between the two diet groups despite the low nutrient content of donor milk in relation to the preterm formula and to the estimated needs of preterm infants. These results contrast with those reported from our parallel two centre study that compared infants randomly assigned a standard term formula or the preterm formula during their early weeks; those fed standard formula, now regarded as nutritionally insufficient for preterm infants, were substantially disadvantaged in PDI and MDI at 18 months post-term. It is shown here that infants from that study fed solely on standard formula had significantly lower developmental scores at 18 months than those fed on donor breast milk in the present study; yet the standard formula had a higher nutrient content than the donor milk. Thus, donor milk feeding was associated with advantages for later development that may have offset any potentially deleterious effects of its low nutrient content for preterm infants. As these outcome advantages were not confounded by the social and educational biases usually associated with mothers' choice to breast feed, our data add significant support to the view that breast milk promotes neurodevelopment.     

Effective gene transfer of lacZ and P0 into Schwann cells of P0-deficient mice

PC12 cells are used as a model system to study neuronal differentiation. Nerve growth factor (NGF) triggers a differentiation pathway in PC12 cells. Neurite outgrowth (a morphological marker of differentiation) in PC12 cells is significantly reduced in the presence of the NOS inhibitor l-NAME, but not d-NAME, implicating NOS in the differentiation process. Previously we have shown that the neuronal NO synthase (nNOS) isoform is induced in PC12 cells in the presence of NGF. Thus, we wished to further evaluate the role of nNOS and NO in PC12 cell differentiation. When a dominant negative mutant nNOS expression vector was transiently transfected into NGF-treated PC12 cells, it significantly reduced PC12 cell neurite outgrowth. Thus, we concluded that the NO required for PC12 cell differentiation, in response to NGF, is produced by nNOS. NO alone was insufficient to induce differentiation as cells treated with the NO donor, sodium nitroprusside did not produce neurites. Treatment of PC12 cells with oxyhemoglobin (an NO scavenger) was also found to significantly reduce the number of neurites produced by PC12 cells treated with NGF. Thus, NO appears to be necessary, but not sufficient, to induce differentiation, and its mode of action appears to be extracellular. A well documented action of NO is to activate soluble guanylate cyclase. Thus, we determined the role of soluble guanylate cyclase activation as a means by which NO induces PC12 cell differentiation. However, in the presence of NGF (to prime PC12 cells for differentiation) and l-NAME (to specifically remove the NO component), 8Br-cGMP (a cGMP analog) failed to induce PC12 cell differentiation. In addition, blockade of sGC activity with specific inhibitors failed to block NGF-induced PC12 cell differentiation. We conclude that the NO required for PC12 cell differentiation is produced by nNOS and that the NO exerts its effects on surrounding PC12 cells in a sGC/cGMP independent manner.