The use of caprylic acid for the extraction of the immunoglobulin fraction from egg yolk of chickens immunised with ovine alpha-lactalbumin

IgY technology: Methods for developing and evaluating avian immunoglobulins for the in vitro detection of biomolecules

The term “IgY technology” was introduced in the literature in the mid 1990s to describe a procedure involving immunization of avian species, mainly laying hens and consequent isolation of the polyclonal IgYs from the “immune” egg yolk (thus avoiding bleeding and animal stress). IgYs have been applied to various fields of medicine and biotechnology. The present article will deal with specific aspects of IgY technology, focusing on the currently reported methods for developing, isolating, evaluating and storing polyclonal IgYs. Other topics such as current information on isolation protocols or evaluation of IgYs from different avian species are also discussed. Specific advantages of IgY technology (e.g., novel antibody specificities that may emerge via the avian immune system) will also be discussed. Recent in vitro applications of polyclonal egg yolk-derived IgYs to the field of disease diagnosis in human and veterinary medicine through in vitro immunodetection of target biomolecules will be presented. Moreover, ethical aspects associated with animal well-being as well as new promising approaches that are relevant to the original IgY technology (e.g., development of monoclonal IgYs and IgY-like antibodies through the phage display technique or in transgenic chickens) and future prospects in the area will also be mentioned.

Simple and efficient protocol for immunoglobulin Y purification from chicken egg yolk

Besides being a common food component broadly consumed worldwide, egg yolk immunoglobulin Y (IgY) has essential therapeutic potentials. In fact, in a time of ever-increasing risk of antibiotic resistance, it is crucial to find new ways to battle infection, and oral administration of preformed specific antibodies represents one of the most attractive approaches against infection. Infectious diseases of bacterial and viral origin in humans and animals can be controlled and passively cured by orally applied IgYs isolated from chicken egg yolks. Despite multiple obvious advantages of oral administration of IgY, harvesting IgY from egg yolk in a pure form is a challenging task.

In this study, we developed a fast, simple, cost-effective, and efficient protocol for IgY isolation from chicken egg yolks. First, egg yolk was collected and diluted with 5 volumes of cold distilled water, homogenized, pH adjusted, and centrifuged. Next, the supernatant was collected, to which caprylic acid at concentration of 2% v/v was added, followed by pH adjustment to pH 5.0, centrifugation at 4°C, and collection of the resulting supernatant. This step was repeated twice, with adding 2% v/v of caprylic acid each time. The final supernatant was concentrated using ultrafiltration, and the IgY purity and activities were checked by SDS-PAGE, western blotting, and ELISA. The sequential (2, 2, 2%) addition of caprylic acid yielded IgY with a purity of 63.5, 90.6, and 95.8%, respectively, and reached 97.9% after ultrafiltration at pH 9.0. The IgY activity increased exponentially to reach 99% after the ultrafiltration step.

The proposed caprylic-acid-based protocol of IgY purification from the yolk of chicken eggs seems to be simple, fast, direct, and very cheap. This indicates that this protocol has great potential for scale-up processing.

Isolation and Characterization of IgM and IgY Antibodies from Plasma of Magellanic Penguins (Spheniscus magellanicus)

Infectious diseases such as aspergillosis, avian malaria, and viral infections are significant threats to the conservation of penguins, leading to morbidity and mortality of these birds both in captivity and in the wild. The immune response to such infectious diseases is dependent on different mechanisms mediated by cells and soluble components such as antibodies. Antibodies or immunoglobulins are glycoproteins that have many structural and functional features that mediate distinct effector immune functions. Three distinct classes of antibodies have been identified in birds: immunoglobulin A (IgA), immunoglobulin M (IgM), and immunoglobulin Y (IgY). In this study we aim to establish an efficient laboratory method to obtain IgM and IgY antibodies from plasma samples of healthy adult Magellanic penguins (Spheniscus magellanicus). The protocol was developed combining plasma delipidation, sequential precipitation with caprylic acid and ammonium sulfate, and size-exclusion chromatography. The efficiency of the protocol and the identity of the purified IgM and IgY antibodies were confirmed through enzyme-linked immunosorbent assay, Western blotting, one-dimensional and two-dimensional polyacrylamide gel electrophoresis, and lectin binding assay. Structural and physicochemical properties of IgM and IgY from Magellanic penguins were consistent with those of other avian species. This purification protocol will allow for more detailed studies on the humoral immunity of penguins and for the development of high specificity serologic assays to test Magellanic penguins for infectious pathogens.

Isolation of a highly thermal stable lama single domain antibody specific for Staphylococcus aureus enterotoxin B

Background

Camelids and sharks possess a unique subclass of antibodies comprised of only heavy chains. The antigen binding fragments of these unique antibodies can be cloned and expressed as single domain antibodies (sdAbs). The ability of these small antigen-binding molecules to refold after heating to achieve their original structure, as well as their diminutive size, makes them attractive candidates for diagnostic assays.

Results

Here we describe the isolation of an sdAb against Staphyloccocus aureus enterotoxin B (SEB). The clone, A3, was found to have high affinity (Kd = 75 pM) and good specificity for SEB, showing no cross reactivity to related molecules such as Staphylococcal enterotoxin A (SEA), Staphylococcal enterotoxin D (SED), and Shiga toxin. Most remarkably, this anti-SEB sdAb had an extremely high Tm of 85°C and an ability to refold after heating to 95°C. The sharp Tm determined by circular dichroism, was found to contrast with the gradual decrease observed in intrinsic fluorescence. We demonstrated the utility of this sdAb as a capture and detector molecule in Luminex based assays providing limits of detection (LODs) of at least 64 pg/mL.

Conclusion

The anti-SEB sdAb A3 was found to have a high affinity and an extraordinarily high Tm and could still refold to recover activity after heat denaturation. This combination of heat resilience and strong, specific binding make this sdAb a good candidate for use in antibody-based toxin detection technologies.

A new membrane based process to isolate immunoglobulin from chicken egg yolk

Although the importance of eggs as a source of specific antibodies has been well recognised, the generation of egg yolk immunoglobulins (IgY) is rarely chosen due to the peculiar composition of egg yolk and the lack of specific affinity ligands. In this work, we report a novel membrane based two-stage ultrafiltration process to isolate IgY from egg yolk. The effects of solution pH, ionic strength, stirring speed and permeate flux on the transmission of proteins were quantified using the pulsed sample injection technique and parameter scanning ultrafiltration. Under optimised conditions, the purity of immunoglobulin obtained was greater than 93% after the two-stage ultrafiltration process and the recovery of immunoglobulin from the feedstock was close to 87%. The resulting immunoglobulin product was then analysed by Isoelectric Focusing (IEF), SDS–PAGE and Circular Dichroism (CD), to confirm its isoelectric point, molecular weight and molecular secondary structure.

Innate profiles of cytokines implicated on oral tolerance correlate with low- or high-suppression of humoral response

SUMMARY

Oral tolerance (OT) is being studied with great interest because of its therapeutic potential in allergy and autoimmunity. In the present study, two mouse strains with extreme phenotypes of OT susceptibility (TS) or resistance (TR) to ovalbumin (OVA) were used to demonstrate whether the tr and ts genes, cumulated during 18 generations of bi-directional genetic selection, influence expression of immunobiological traits in naive or antigen-gavaged TR/TS mice. The difference in anti-OVA titres was 2048-fold between OVA-gavaged TS and TR mice. Tolerance susceptibility to OVA gavage in individuals from a (TS x TR)F(2) population was 24% high-susceptibility, 62% low-susceptibility and 14% non-tolerant. Different antigens, unrelated to OVA, were tested by gavage and TS mice were generally susceptible while TR mice were resistant. The stability of TS and TR phenotypes was not affected by the use of strict protocols of intraperitoneal immunization or feeding over 30 consecutive days. The levels of interleukin-2 (IL-2), IL-4, interferon-gamma and IL-10 cytokines evaluated in concanavalin A-stimulated spleen cells from naive mice and in OVA-stimulated spleen cells from OVA-gavaged mice were higher in TS mice. Interleukin-10 was up-regulated in OVA-gavaged TS mice and down-regulated in TR mice. In naive mice, the percentage of CD4(+) CD25(+) and CD4(+) Foxp3(+) spleen cells and IL-10 expression by CD4(+) cells was significantly higher in TS mice. These results indicate that regulation of IL-10 expression could be an important factor contributing to the mechanisms controlling OT susceptibility, and that the OT responses of TR and TS individuals strongly correlate with their innate potential to secrete this cytokine.

Brazilian IgY-Bothrops antivenom: Studies on the development of a process in chicken egg yolk

The aims of this study were to devise a process for raising antibodies against Brazilian Bothrops venom in chicken egg yolks, to determine the best delipidation method for the preparation of the aqueous extract and to define the best purification conditions for IgY bothropic antivenom produced in eggs from hens immunized with Brazilian standard bothropic antigen. A group of nine Single Comb White Leghorn laying hens were immunized with venom from five different species of pit vipers of the genus Bothrops. The immunization process was carried out in three cycles, each performed six weeks apart. For extraction, the egg yolk was diluted 1:10 in distilled water, adjusted to a pH of 5.0, subjected to a freeze-thaw cycle, centrifuged and filtered before being precipitated with 20%(w/v) ammonium sulfate salt. This methodology retrieved 2.57 mg of IgY/ml of yolk from eggs. This preparation yielded antibodies capable of neutralizing lethal toxic activity of the pool of Bothrops sp venoms from five species, with an effective dose (ED50) of 365 microL/2 LD50 and, 1.0 mL of IgY antivenom neutralized 0.154 mg of venom.

Partitioning and inactivation of viruses by the caprylic acid precipitation followed by a terminal pasteurization in the manufacturing process of horse immunoglobulins

Caprylic acid (octanoic acid), has been used for over 50 years as a stabilizer of human albumin during pasteurization. In addition caprylic acid is of great interest, by providing the advantage of purifying mammalian immunoglobulins and clearing viruses infectivity in a single step. Exploiting these two properties, we sequentially used the caprylic acid precipitation and the pasteurization to purify horse hyperimmune globulins used in the manufacturing of Sérocytol. To evaluate the effectiveness of the process for the removal/inactivation of viruses, spiking studies were carried out for each dedicated step. Bovine viral diarrhoea virus (BVDV), pseudorabies virus (PRV), encephalomyocarditis virus (EMCV) and minute virus of mice (MVM) were used for the virological validation. Our data show that the treatment with caprylic acid 5% (v/v) can effectively be used as well to purify or to ensure viral safety of immunoglobulins. Caprylic acid precipitation was very efficient in removing and/or inactivating enveloped viruses (PRV, BVDV) and moderately efficient against non-enveloped viruses (MVM, ECMV). However the combination with the pasteurization ensured an efficient protection against both enveloped and non-enveloped viruses. So that viruses surviving to the caprylic acid precipitation will be neutralized by pasteurization. Significant log reduction were achieved > or =9 log(10) for enveloped viruses and 4 log(10) for non-enveloped viruses, providing the evidence of a margin of viral safety achieved by our manufacturing process. Its a simple and non-expensive manufacturing process of immunoglobulins easily validated that we have adapted to a large production scale with a programmable operating system.

Preparation of immunoglobulin Y from egg yolk using ammonium sulfate precipitation and ion exchange chromatography

The objective of this study was to develop an economical, simple, and large-scale separation method for IgY from egg yolk. Egg yolk diluted with 9 volumes of cold water was centrifuged after adjusting the pH to 5.0. The supernatant was added with 0.01% charcoal or 0.01% carrageenan and centrifuged at 2,800 x g for 30 min. The supernatant was filtered through a Whatman no. 1 filter paper and then the filtrate was concentrated to 20% original volume using ultrafiltration. The concentrated solution was further purified using either cation exchange chromatography or ammonium sulfate precipitation. For the cation exchange chromatography method, the concentrated sample was loaded onto a column equilibrated with 20 mM citrate-phosphate buffer at pH 4.8 and eluted with 200 mM citrate-phosphate buffer at pH 6.4. For the ammonium sulfate precipitation method, the concentrated sample was twice precipitated with 40% ammonium sulfate solution at pH 9.0. The yield and purity of IgY were determined by ELISA and electrophoresis. The yield of IgY from the cation exchange chromatography method was 30 to 40%, whereas that of the ammonium sulfate precipitation was 70 to 80%. The purity of IgY from the ammonium sulfate method was higher than that of the cation exchange chromatography. The cation exchange chromatography could handle only a small amount of samples, whereas the ammonium sulfate precipitation could handle a large volume of samples. This suggests that ammonium sulfate precipitation was a more efficient and useful purification method than cation exchange chromatography for the large-scale preparation of IgY from egg yolk.

Quantification of Antibody (IgY) Titers in Hen Eggs Following Immunization and their Use in Detecting Cell Surface Molecules on Nitrocellulose Membranes

HLA-A*0201 alpha chain and beta2m were expressed from a prokaryotic system, and after refolding and purification, the alpha chain and beta2m were used to immunize eight laying hens. The titer of egg yolk antibody against alpha chain increased from 10(2) to 10(5.3) The titer of egg yolk antibody against beta2m increased from 10(1) to 10(4.7). The extent of titer increase is similar between the two antigens. An average of 135 mg purified polyclonal antibody (IgY) can be easily obtained from one egg yolk. The use of egg collection rather than serum collection is compatible with modern animal protection regulations. An average of 28 eggs were obtained from a laying hen every month, with a total amount of 3780 mg immunoglobulin extracted from one immunized hen every month, which would be equivalent to 630 mL of serum or 1260 mL of blood per month. Chickens are an optimal host for the production of polyclonal antibodies with high titer and high yield. Purified IgY was labeled with horseradish peroxidase and reacted with PBMC on nitrocellulose membranes indicating that the antibody can bind to the native conformation of class I HLA molecule on PBMC.

Simple purification methods for an alphagalactose-specific antibody from chicken eggs

For many applications avian antibody from egg yolk (IgY) offers advantages over the well-known mammalian antibodies. Different experimental techniques for the purification of IgY from chickens immunized with an alphagalactose-containing antigen (alphaGal-trisaccharide) were compared. These included ammonium sulfate precipitation, filtration with diatomaceous earth, treatment with deoxycholate, and thiophilic and affinity chromatography. Samples were tested for overall purity, protein and lipid content, and specific activity. Evaluated on the basis of these results and the simplicity of the process, the favored purification method is ammonium sulfate precipitation of diluted egg yolk directly followed by affinity chromatography. The high lipid content of IgY preparations is greatly reduced by either thiophilic or affinity chromatography. Affinity purification of ammonium sulfate precipitated material resulted in anti-alphaGal-trisaccharide IgY preparations with approximately 1% of the original protein content but approximately 100-fold higher specific activity for the alphaGal-trisaccharide epitope.

Detection and serological relationships of cymbidium mosaic potexvirus isolates

Twenty-two isolates of Cymbidium mosaic virus (CyMV) were isolated from 35 orchid plants suspected of being infected with CyMV. Among the three methods used for detecting CyMV, immunoelectron microscopy (IEM-1) was shown to be the most sensitive method, being able to detect the virus in 71.43% of suspected CyMV-infected plants while the electron microscopic method and the indexing plant method could detect 51.43 and 42.86%, respectively. Out of 12 symptomless plants investigated, 25% were found by IEM-1 method to be infected with the virus. Purified CyMV were flexuous rods having lengths between 470-490 nm. A few end-to-end aggregates were also observed and the 280 260 absorbance ratios were from 0.884 to 0.929. The yield of CyMV was 31.07 to 44.09 mg per kg of Datura leaves. Antibodies against purified CyMV D2 were produced in rabbits and hens. The antibody titers in the yolk and sera of hens indicated that 0.5 mg of virus per immunization efficiently generated an abundant supply of IgY in the yolk, however 1 mg of virus per immunization gave a stronger immune response in both sera and yolk. The average yields of IgY were 6.5 +/- 0.6 and 9.4 +/- 0.9 mg/ml of yolk in the group that received 0.5 mg and the group that received 1.0 mg of the virus, respectively. Positive ELISA reactions were observed in 18 and 20 of 22 CyMV isolates when detected with rabbit IgG and IgY, respectively, demonstrating that those isolates were serologically related and the ELISA reactions were shown to be stronger with IgY than those with rabbit IgG in most isolates. The degree of reaction between the CyMV isolates, O(2) and O(4), and IgY was less than that of the other isolates. The two isolates, D(6) and Cat(6), gave negative reactions to rabbit IgG. The results of ELISA assays showed that the homologous serological reaction was not consistently stronger than the heterologous one. Twelve isolates out of twenty-two gave stronger reactions than the homologous antigen (CyMV D(2)) when IgY was used as the detecting antibody while nine isolates gave stronger reactions when using rabbit IgG. No reactions were observed with other plant viruses and plant proteins from healthy Datura.

Chicken egg yolk antibodies (IgY-technology): a review of progress in production and use in research and human and veterinary medicine

The production of antibodies (Abs) in chickens and the extraction of specific Abs from egg yolk (IgY Abs) are increasingly attracting the interest of the scientific community, as demonstrated by the significant growth of the IgY literature. This review offers detailed and comprehensive information about IgY-technology, including: a) possibilities for hen keeping in accordance with the Three Rs principles; b) new insights into the IgY transfer mechanism from blood to yolk as a biological basis for the technology; c) the comparative characteristics of IgY Abs and IgG Abs; d) the high efficacy of the technique, in view of the extraordinary amount of IgY Ab produced by one hen in one year (between 20 g and 40 g IgY in total); e) comparisons between the efficacies of IgY Abs and IgG Abs (rabbit, sheep, mouse) in several immunological assays; f) immunisation protocols, as well as the most commonly used IgY-extraction procedures; g) new possibilities for application in human and veterinary medicine, including strategies for the treatment of Helicobacter pylori infection or fatal intestinal diseases in children, particularly in poor countries, for reducing the use of antibiotics, and, in Asia and South America, for producing Abs against snake, spider and scorpion venoms; and h) the use of IgY Abs in various fields of research, also taking into consideration recent developments in South America (particularly Argentina and Cuba) and in Asia.

Efficient production, purification, and application of egg yolk antibodies against human HLA-A*0201 heavy chain and light chain (beta2m)

The importance of eggs as a source of specific antibodies is well recognized. Egg yolk contains 8--20mg immunoglobulins (IgY) per milliliter. However, the major problem in separating IgY is to remove the high concentrations of lipids in egg yolk. We first used water dilution method to get the supernatant containing IgY, then purified the antibody by caprylic acid-ammonium sulfate method, and obtained specific antibody with satisfactory purity and activity. By comparison of these several methods, each has its advantages, one can be chosen to purify IgY according to practical need. The purified IgY produced by the immunized chickens can stain the human peripheral blood mononuclear cell effectively when labeled with fluorescent FITC.

A comparison of three methods for extracting IgY from the egg yolk of hens immunized with Sendai virus

Hens were immunized with partially purified Sendai virus that had been grown on chicken embryos. The titres of specific antibodies to Sendai virus varied from log2 13.0 to 15.5 during the 4 months after immunization and the immunoglobulin Y (IgY) concentration varied from 2 to 10 mg per ml of egg yolk. A method has been developed employing dextran blue to isolate IgY from the egg yolk. The dextran blue method was compared with two other methods (poly(ethylene glycol) and chloroform) in terms of yield, total protein content, IgY concentration, specific activity of IgY and SDS-PAGE analysis. The specific activity and the IgY content obtained by these three methods proved to be identical, in the range log2 12.9-14.1, and 4.6-12.8 mg/egg, respectively. However, the total protein content when purified by chloroform was 2-fold to 4-fold higher than that of the others. The analysis of IgY by SDS-PAGE demonstrated that IgY purified with dextran blue contained three major protein components with molecular weights of 34.7 kDa, 41 kDa and 66 kDa and one minor protein of 45 kDa. IgY that was extracted with chloroform contained two major proteins of 45.7 kDa and 75.2 kDa and that extracted with PEG-6000 contained only one major protein of 66 kDa. The IgY obtained by these latter methods also contained several minor proteins in the range 41-80 kDa.

Studies on the measurement of phospholipase A2 (PLA2) and PLA2 inhibitor activities in ram semen

Extraction with Tris-citrate or Tris-NaCl-EGTA improved the yield of phospholipase A2 (PLA2) from ram semen by 40-50 fold over the previously recommended method of extraction by dilute (0.18 N) sulphuric acid. The enzyme activity in the citrate extract deteriorated more rapidly than in Tris-NaCl-EGTA. The semen PLA2 activity was optimum at pH 8.0, heat sensitive at 70 degrees C for 30 min, activated by Ca2+ (although approximately 60% activity was also found in the absence of calcium) and did not exist as a pro-enzyme. The semen PLA2 activity was equally distributed among the sperm and seminal plasma (SP) components of ram semen. However, the low levels of PLA2 activity in the SP of vasectomised rams tend to suggest that PLA2 in the SP fraction may have originated from testicular or epididymal secretions or leakage, from sperm. PLA, in sperm exists as a large molecular weight aggregate, whereas in SP it is present as a smaller aggregate. In addition to PLA2, semen also contained PLA2 inhibitor activities. Inhibition was observed against PLA2s from bee venom, pig pancreas and oviductal extracts. The inhibitory activity is presumed to be due to a large molecular weight protein as the inhibitor activity was not extracted in a chloroform:methanol (2:1; v/v) mixture, it was non-dialysable, precipitated by 10% trichloroacetic acid and destroyed by proteases. The inhibitor activity was distributed in various molecular weight fractions of sperm, SP and SP from vasectomised rams.

Development of snake antivenom antibodies in chickens and their purification from yolk

Adult white leghorn hens hyperimmunised with Brazilian snake venoms of the genus Bothrops and/or Crotalus produced antibodies capable of recognising, combining with and neutralising the toxic and lethal components of the venoms. The antibodies were first detected by an enzyme-linked immunosorbent assay two weeks after starting the immunisation schedule, reached the highest titres by the third week and remained high for at least 24 weeks. These antibodies are transferred to the egg yolk from which they were isolated as enriched IgY preparations by a combination of methods using positive and negative precipitation with sodium sulphate and/or caprylic acid. The yolk-derived IgY preparations contained antibodies which blocked the phospholipase A2-dependent haemolytic activity of both venoms and the haemorrhagic activity of Bothrops venom, and neutralised the toxic lethal activities of the venoms with good efficacy. The median effective dose (ED50) of the IgY anti-Bothrops venom was 592.5 microliters/2LD50 and, 1.0 ml neutralised 0.0675 mg of venom. The ED50 of the IgY anti-Crotalus venom was 457.5 microliters/3LD50 and 1.0 ml neutralised 0.075 mg of venom.

Proteasome inhibitors prevent tracheary element differentiation in zinnia mesophyll cell cultures

To determine whether proteasome activity is required for tracheary element (TE) differentiation, the proteasome inhibitors clasto-lactacystin beta-lactone and carbobenzoxy-leucinyl-leucinyl-leucinal (LLL) were used in a zinnia (Zinnia elegans) mesophyll cell culture system. The addition of proteasome inhibitors at the time of culture initiation prevented differentiation otherwise detectable at 96 h. Inhibition of the proteasome at 48 h, after cellular commitment to differentiation, did not alter the final percentage of TEs compared with controls. However, proteasome inhibition at 48 h delayed the differentiation process by approximately 24 h, as indicated by examination of both morphological markers and the expression of putative autolytic proteases. These results indicate that proteasome function is required both for induction of TE differentiation and for progression of the TE program in committed cells. Treatment at 48 h with LLL but not clasto-lactacystin beta-lactone resulted in partial uncoupling of autolysis from differentiation. Results from gel analysis of protease activity suggested that the observed incomplete autolysis was due to the ability of LLL to inhibit TE cysteine proteases.

No evidence for basolateral secretion of milk protein in the mammary gland of lactating goats

Recent research suggests that a small percentage of milk proteins may be secreted basolaterally, which would have implications for our work on the permeability of tight junctions in the mammary epithelium. In our work, the presence of alpha-lactalbumin (LA) or lactose in plasma is used as an indicator of permeability. The aim of this study was to examine basolateral secretion by determining the presence of milk proteins in efferent mammary lymph. Five Saanen goats were fitted with mammary lymph catheters and were administered intramammary isosmotic bolus infusions of sucrose control solutions or ethylene glycolbis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid to induce leaky tight junctions. Lymph samples were collected before and approximately 5 h after infusion. Lymph was analyzed by Western blotting for the presence of alpha-casein (CN), beta-CN, and alpha-LA No alpha-CN or beta-CN was detected in lymph, but alpha-LA was detected in all lymph samples. Moreover, the signal was much stronger in samples from goats that were treated with ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid, and concentrations of alpha-LA in lymph were significantly increased with this treatment. These changes and the absence of casein in lymph suggest increased permeability of tight junctions rather than basolateral secretion. In summary, these data do not support basolateral secretion.

Posttranscriptional regulation of collagen alpha1(I) mRNA in hepatic stellate cells

The hepatic stellate cell (HSC) is the primary cell responsible for the dramatic increase in the synthesis of type I collagen in the cirrhotic liver. Quiescent HSCs contain a low level of collagen alpha1(I) mRNA, while activated HSCs contain about 60- to 70-fold more of this mRNA. The transcription rate of the collagen alpha1(I) gene is only two fold higher in activated HSCs than in quiescent HSCs. In assays using actinomycin D or 5,6-dichlorobenzimidazole riboside collagen alpha1(I) mRNA has estimated half-lives of 1.5 h in quiescent HSCs and 24 h in activated HSCs. Thus, this 16-fold change in mRNA stability is primarily responsible for the increase in collagen alpha1(I) mRNA steady-state level in activated HSCs. We have identified a novel RNA-protein interaction targeted to the C-rich sequence in the collagen alpha1(I) mRNA 3' untranslated region (UTR). This sequence is localized 24 nucleotides 3' to the stop codon. In transient transfection experiments, mutation of this sequence diminished accumulation of an mRNA transcribed from a collagen alpha1(I) minigene and in stable transfections decreased the half-life of collagen alpha1(I) minigene mRNA. Binding to the collagen alpha1(I) 3' UTR is present in cytoplasmic extracts of activated but not quiescent HSCs. It contains as a subunit alphaCP, which is also found in the complex involved in stabilization of alpha-globin mRNA. The auxiliary factors necessary to promote binding of alphaCP to the collagen 3' UTR are distinct from the factors necessary for binding to the alpha-globin sequence. Since alphaCP is expressed in both quiescent and activated HSCs, these auxiliary factors are responsible for the differentially expressed RNA-protein interaction at the collagen alpha1(I) mRNA 3' UTR.

Differences in the abundance of nuclear proteins in the bovine mammary gland throughout the lactation and gestation cycles

The mechanisms that control the synthesis of milk protein are not fully understood and could well involve undiscovered proteins within the mammary gland. A search for such proteins in high salt extracts of nuclei that had been isolated from bovine mammary tissues was undertaken using two-dimensional electrophoresis on large format gels. The sensitivity of the procedure was sufficient to detect the transcription factors Sp1 and NF-1 by Coomassie blue stain; over 300 proteins were routinely detected. Analysis of mammary tissue taken from 5 nonlactating cows in midpregnancy, 5 cows in late lactation, and 4 cows in early involution revealed five proteins where relative abundance was altered with stage of lactation or reproductive cycle. Four of these proteins were identified by Western blotting or amino acid sequencing as lactoferrin, annexin II, vimentin, and heavy-chain immunoglobulin. Analysis of proteins after further enrichment of the extracts by heparin-Sepharose affinity chromatography revealed an additional protein that was substantially more abundant in samples from lactating cows. This 90-kDa protein did not react with anti-Stat5 antibodies. Conceivably, one or more of these six proteins could play a role in the lactational function of the bovine mammary gland.

Effect of atropine on milk protein yield by dairy cows with different beta-lactoglobulin phenotypes

The objective of this study was to determine the response of individual milk proteins to a reduction in amino acid (AA) availability induced by atropine and to determine whether the response was different in cows with different beta-lactoglobulin (LG) phenotypes. Six cows that were homozygous for the A variant of beta-LG and six cows that were homozygous for the B variant of beta-LG were each given a single subcutaneous injection of saline or 20 mg of atropine. In both groups of cows, atropine decreased milk yield by 30% and reduced the concentration of alpha-lactalbumin (LA) by 25 to 30% at 8 h following injection. Eight hours after atropine injection, yield of beta-LG was 41% lower than it was following saline injection, and yield of beta-casein (CN) after atropine injection declined 16% relative to saline. Concentrations of BSA and the ratio of gamma-CN to beta-CN, which reflects plasmin activity in milk, were significantly increased after administration of atropine. Although the response to atropine tended to be more pronounced in cows that were homozygous for beta-LG B, they were not significantly different from the response of cows that were homozygous for beta-LG B, they were not significantly different from the response of cows that were homozygous for beta-LG A. The differential response of individual proteins to a reduction in AA concentrations in whole blood suggested that susceptibility to restriction in substrate availability differed for individual proteins. The concentration of lactose in plasma did not change, which implied that the integrity of the mammary epithelial barrier was not compromised when AA derived from blood were diminished. The consistent concentration of lactose combined with the minimal increase in total yield of BSA in milk following atropine treatment indicated that the increased concentration in milk of proteins derived from serum was due to the concentrating effect of lower milk volume.

Influence of standards and antibodies in immunochemical assays for quantitation of immunoglobulin G in bovine milk

This study reports the influence of using various reference antigens or standards as well as the source of antibody in the immunochemical quantitation of bovine immunoglobulin (Ig) G. Standard curves from analyses by ELISA and radial immunodiffusion were compared for bovine IgG from serum, colostrum, and cheese whey and for the two subclasses IgG1 and IgG2. Also compared were different sources of polyclonal antibodies (antisera from rabbit and sheep or hen yolk) and monoclonal antibodies that had various antibody specificities. The results indicate that IgG1 was a reliable alternative to purified IgG from milk or cheese whey for quantitation of IgG in milk based on ELISA absorbance. Serum IgG, colostral IgG, and IgG2 greatly underestimated milk IgG, regardless of the source of antibody used. Determination of milk IgG by radial immunodiffusion using antisera that were specific for rabbit anti-bovine IgG (H + L) was less dependent on the source of IgG that was used as the standard antigen. However, radial immunodiffusion using subclass-specific antibodies led to inaccurate estimation of IgG in milk unless the quantitation was based on a standard curve for IgG from milk. The Ig from hen yolk were a feasible alternative source of specific antibodies for immunoassay of IgG in bovine milk.

Four highly stable eukaryotic mRNAs assemble 3' untranslated region RNA-protein complexes sharing cis and trans components

Assembly of a sequence-specific RNA-protein complex on the 3' untranslated region (3'UTR) of human alpha-globin mRNA (alpha-complex) correlates with mRNA stabilization. Here we map a limited segment of the alpha-globin 3'UTR that is both necessary and sufficient for alpha-complex formation. The sequence of this binding region identifies three additional, highly stable mRNAs that share closely related, pyrimidine-rich cis-motifs in their respective 3'UTRs. Each mRNA assembles a sequence-specific ribonucleoprotein complex at this conserved region. These complexes are structurally related, and each contains a 39-kDa cytoplasmic poly(C) binding protein previously demonstrated to be essential to formation of the alpha-complex. These observations indicate the existence of a general determinant for stabilization of eukaryotic mRNAs.