Immunoblotting and dot blotting

Rapid Dot-Blot Immunoassay for Detecting Multiple Salmonella enterica Serotypes

Salmonella, a major contributor to foodborne infections, typically causes self-limiting gastroenteritis. However, it is frequently invasive and disseminates across the intestinal epithelium, leading to deadly bacteremia. Although the genus is subdivided into >2,600 serotypes based on their antigenic determinants, only few serotypes are responsible for most human infections. In this study, a rapid dot-blot immunoassay was developed to diagnose multiple Salmonella enterica serotypes with high incidence rates in humans. The feasibility of 10 commercial antibodies (four polyclonal and six monoclonal antibodies) was tested using the 18 serotypes associated with 67.5% Salmonella infection cases in the United States of America (U.S.A) in 2016. Ab 3 (polyclonal; eight of 18 serotypes), Ab 8 (monoclonal; 13 of 18 serotypes), and Ab 9 (monoclonal; 10 of 18 serotypes) antibodies exhibited high detection rates in western blotting and combinations of two antibodies (Ab 3+8, Ab 3+9, and Ab 8+9) were applied to dot-blot assays. The combination of Ab 3+8 identified 15 of the tested 18 serotypes in 3 h, i.e., S. Enteritidis, S. Typhimurium, S. Javiana, S. I 4,[5],12:i:-, S. Infantis, S. Montevideo, S. Braenderup, S. Thompson, S. Saintpaul, S. Heidelberg, S. Oranienburg, S. Bareilly, S. Berta, S. Agona, and S. Anatum, which were responsible for 53.7% Salmonella infections in the U.S. in 2016. This cost-effective and rapid method can be utilized as an on-site colorimetric method for Salmonella detection.

PSAC-6mA: 6mA site identifier using self-attention capsule network based on sequence-positioning

DNA N6-methyladenine (6mA) modifications play a pivotal role in the regulation of growth, development, and diseases in organisms. As a significant epigenetic marker, 6mA modifications extensively participate in the intricate regulatory networks of the genome. Hence, gaining a profound understanding of how 6mA is intricately involved in these biological processes is imperative for deciphering the gene regulatory networks within organisms. In this study, we propose PSAC-6mA (Position-self-attention Capsule-6mA), a sequence-location-based self-attention capsule network. The positional layer in the model enables positional relationship extraction and independent parameter setting for each base position, avoiding parameter sharing inherent in convolutional approaches. Simultaneously, the self-attention capsule network enhances dimensionality, capturing correlation information between capsules and achieving exceptional results in feature extraction across multiple spatial dimensions within the model. Experimental results demonstrate the superior performance of PSAC-6mA in recognizing 6mA motifs across various species.

A practical guide to in situ and ex situ characterisation of arabinogalactan proteins (AGPs) in fruits

BACKGROUND

Arabinogalactan proteins (AGPs) are plant cell components found in the extracellular matrix that play crucial roles in fruit growth and development. AGPs demonstrate structural diversity due to the presence of a protein domain and an expanded carbohydrate moiety. Considering their molecular structure, the modification of glycosylation is a primary factor contributing to the functional variety of AGPs.

MAIN BODY

Immunocytochemical methods are used for qualitative and quantitative analyses of AGPs in fruit tissues. These include in situ techniques such as immunofluorescence and immunogold labelling for visualising AGP distribution at different cellular levels and ex situ methods such as Western blotting and enzyme-linked immunoenzymatic assays (ELISA) for molecular characterisation and quantitative detection of isolated AGPs. The presented techniques were modified by considering the structure of AGPs and the changes that occur in fruit tissues during the development and ripening processes. These methods are based on antibodies that recognise carbohydrate chains, which are the only commercially available highly AGP-specific tools. These probes recognise AGP epitopes and identify structural modifications and changes in spatio-temporal distribution, shedding light on their functions in fruit.

CONCLUSION

This paper provides a concise overview of AGP research methods, emphasising their use in fruit tissue analysis and demonstrating the accessibility gaps in other tools used in such research (e.g. antibodies against protein moieties). It underscores fruit tissue as a valuable source of AGPs and emphasises the potential for future research to understand of AGP synthesis, degradation, and their roles in various physiological processes. Moreover, the application of advanced probes for AGP visualisation is a milestone in obtaining more detailed insights into the localisation and function of these proteins within fruit.

Synthesis, molecular docking, and in-vitro studies of pyrimidine-2-thione derivatives as antineoplastic agents via potential RAS/PI3K/Akt/JNK inhibition in breast carcinoma cells

In the present investigation, derivatives from (2-6) containing pyrimidine-2-thione moiety incorporated with different heterocycles such as pyrazoline, phenyl pyrazoline, and pyrimidine were synthesized using different methods. These pyrimidine-2-thione derivatives were evaluated in-silico for their capability to inhibit the H-RAS-GTP active form protein with insight to their pharmacokinetics properties. According to our findings, compound 5a was selected for in vitro studies as it has the in-silico top-ranked binding energy. Furthermore, compound 5a induced apoptosis to panels of cancer cell lines with the best IC₅₀ on MCF-7 breast cancer cells (2.617 ± 1.6 µM). This effect was associated with the inhibition of phosphorylated RAS, JNK proteins, and PI3K/Akt genes expression. Thus, compound 5a has upregulated p21 gene and p53 protein levels. Moreover, 5a arrested the cell cycle progression at the sub-G0/G1 phase. In conclusion, the synthesized compound, 5a exhibited potent antineoplastic activity against breast cancer cell growth by targeting RAS/ PI3K/Akt/ JNK signaling cascades.

Dot-Blotting: A Quick Method for Expression Analysis of Recombinant Proteins

Expressing recombinant proteins in heterologous host cells is a prerequisite for purification and other downstream processes. Cell cultures require a protein expression test to optimize incubation time, temperature, and additives (like chemical inducers) to identify the best growth conditions with maximum recombinant protein yield. However, running SDS-PAGE followed by western blotting is cumbersome and results are not quick. Here, I describe a simple protocol to quickly check the presence of recombinant protein in cell cultures using a dot-blot experiment. The cells can be rapidly lysed and directly spotted on the nitrocellulose membrane. Then, the membrane is incubated with a horseradish peroxidase (HRP) conjugated antibody raised against the affinity tag present on the recombinant protein to confirm the protein expression by chemiluminescence. It takes less than an hour to get results. This method rapidly investigates recombinant protein expression in different cell lines and tests other variables. © 2022 Wiley Periodicals LLC. Basic Protocol 1: Protein expression analysis for eukaryotic systems Basic Protocol 2: Protein expression analysis for bacterial systems.

Under-5-Minute Immunoblot Assays by Vortex Fluidic Device Acceleration

Unlocking the potential of personalized medicine in point-of-care settings requires a new generation of biomarker and proteomic assays. Ideally, assays could inexpensively perform hundreds of quantitative protein measurements in parallel at the bedsides of patients. This goal greatly exceeds current capabilities. Furthermore, biomarker assays are often challenging to translate from benchtop to clinic due to difficulties achieving and assessing the necessary selectivity, sensitivity, and reproducibility. To address these challenges, we developed an efficient (<5 min), robust (comparatively lower CVs), and inexpensive (decreasing reagent use and cost by >70 %) immunoassay method. Specifically, the immunoblot membrane is dotted with the sample and then developed in a vortex fluidic device (VFD) reactor. All assay steps-blocking, binding, and washing-leverage the unique thin-film microfluidics of the VFD. The approach can accelerate direct, indirect, and sandwich immunoblot assays. The applications demonstrated include assays relevant to both the laboratory and the clinic.

Analysis of Proteins by Immunoblotting

In immunoblotting (western blotting), proteins are first separated by SDS-PAGE and then transferred electrophoretically from the gel onto a support membrane that binds proteins tightly. After the unreacted binding sites of the membrane are blocked to suppress nonspecific adsorption of antibodies, the immobilized proteins are reacted with a specific polyclonal or monoclonal antibody. Antigen-antibody complexes are visualized using chromogenic, fluorescent, or chemiluminescent reactions. Immunoblotting protocols are reagent specific and, owing to the wide assortment of equipment, reagents, and antibodies available, highly diverse. Presented here is an example of a workable protocol for developing a blot using horseradish peroxidase (HRP)-conjugated secondary antibody and enhanced chemiluminescence (ECL). ECL is based on the emission of light during the HRP-catalyzed oxidation of luminal or other substrates. Emitted light is captured on film or by a CCD camera, for qualitative or semiquantitative analysis. Because ECL is so sensitive, it has become a popular detection method. This protocol can be modified for different membranes, antibodies, and detection systems. Optimal dilutions of the primary and secondary antibodies need to be determined empirically, but recommendations provided by the manufacturer are usually a good starting point.

The exploration of N6-deoxyadenosine methylation in mammalian genomes

N⁶-methyladenine (N⁶-mA, m⁶dA, or 6mA), a prevalent DNA modification in prokaryotes, has recently been identified in higher eukaryotes, including mammals. Although 6mA has been well-studied in prokaryotes, the function and regulatory mechanism of 6mA in eukaryotes are still poorly understood. Recent studies indicate that 6mA can serve as an epigenetic mark and play critical roles in various biological processes, from transposable-element suppression to environmental stress response. Here, we review the significant advances in methodology for 6mA detection and major progress in understanding the regulation and function of this non-canonical DNA methylation in eukaryotes, predominantly mammals.

Nanotechnology-based Colorimetric Approaches for Pathogenic Virus Sensing: A review

Fast and inexpensive virus identification protocols are paramount to hinder the further extent of pandemic diseases, minimize economic and social damages, and expedite proper clinical rehabilitation. Until now, various biosensors have been fabricated for the identification of pathogenic particles. But, they offer many difficulties. Nanotechnology resolves these difficulties and offers direct identification of pathogenic species in real-time. Among them, nanomaterial based-colorimetric sensing approach of pathogenic viruses by the naked eye has attracted much awareness because of their simplicity, speed, and low cost. In this review, the latest tendencies and advancements are overviewed in detecting pathogenic viruses using colorimetric concepts. We focus on and reconsider the use of distinctive nanomaterials such as metal nanoparticles, carbon nanotubes, graphene oxide, and conducting polymer to form colorimetric pathogenic virus sensors.

A simple and rapid pipeline for identification of receptor-binding sites on the surface proteins of pathogens

Ligand-receptor interactions play a crucial role in the plethora of biological processes. Several methods have been established to reveal ligand-receptor interface, however, the majority of methods are time-consuming, laborious and expensive. Here we present a straightforward and simple pipeline to identify putative receptor-binding sites on the pathogen ligands. Two model ligands (bait proteins), domain III of protein E of West Nile virus and NadA of Neisseria meningitidis, were incubated with the proteins of human brain microvascular endothelial cells immobilized on nitrocellulose or PVDF membrane, the complex was trypsinized on-membrane, bound peptides of the bait proteins were recovered and detected on MALDI-TOF. Two peptides of DIII (~916 Da and ~2003 Da) and four peptides of NadA (~1453 Da, ~1810 Da, ~2051 Da and ~2433 Da) were identified as plausible receptor-binders. Further, binding of the identified peptides to the proteins of endothelial cells was corroborated using biotinylated synthetic analogues in ELISA and immunocytochemistry. Experimental pipeline presented here can be upscaled easily to map receptor-binding sites on several ligands simultaneously. The approach is rapid, cost-effective and less laborious. The proposed experimental pipeline could be a simpler alternative or complementary method to the existing techniques used to reveal amino-acids involved in the ligand-receptor interface.

Determination of Autoantibodies by Line Immunoblotting

Autoantibody detection is a useful and obligatory tool for clinicians and researchers in diagnosing autoimmune diseases. Line blotting is a simple, sensitive, and flexible technique for fast semiquantitative detection of multiple antibodies. Line blotting enables the detection of antibodies on membrane strips coated with thin parallel lines of several purified, biochemically characterized antigens, which are fixed onto a synthetic support. Each strip can contain more than ten antigens, thus allowing simultaneous screening for multiple antibodies. Here, we describe the principle of line blotting and how the buffer composition can interfere with the results of autoantibody detection.

Transient expression of anti-VEFGR2 nanobody in Nicotiana tabacum and N. benthamiana

In human, the interaction between vascular endothelial growth factor (VEGF) and its receptor (VEGFR2) is critical for tumor angiogenesis. This is a vital process for cancer tumor growth and metastasis. Blocking VEGF/VEGFR2 conjugation by antibodies inhibits the neovascularization and tumor metastasis. This investigation designed to use a transient expression platform for production of recombinant anti-VEGFR2 nanobody in tobacco plants. At first, anti-VEGFR2-specific nanobody gene was cloned in a Turnip mosaic virus (TuMV)-based vector, and then, it was expressed in Nicotiana benthamiana and Nicotiana tabacum cv. Xanthi transiently. The expression of nanobody in tobacco plants were confirmed by reverse transcription-polymerase chain reaction (RT-PCR), dot blot, enzyme-linked immunosorbent assays (ELISA), and Western blot analysis. It was shown that tobacco plants could accumulate nanobody up to level 0.45% of total soluble protein (8.3 µg/100 mg of fresh leaf). This is the first report of the successful expression of the camelied anti-VEFGR2 nanobody gene in tobacco plants using a plant viral vector. This system provides a fast solution for production of pharmaceutical and commercial proteins such as anti-cancer nanobodies in tobacco plants.

Anti-IgG-anchored liquid crystal microdroplets for label free detection of IgG

AIgG anchored LC microdroplets showing configurational transition from radial (a) to bipolar (b) upon interaction with IgG.

Arabidopsis PTB1 and PTB2 proteins negatively regulate splicing of a mini-exon splicing reporter and affect alternative splicing of endogenous genes differentially

This paper examines the function of Arabidopsis thaliana AtPTB1 and AtPTB2 as plant splicing factors. The effect on splicing of overexpression of AtPTB1 and AtPTB2 was analysed in an in vivo protoplast transient expression system with a novel mini-exon splicing reporter. A range of mutations in pyrimidine-rich sequences were compared with and without AtPTB and NpU2AF65 overexpression. Splicing analyses of constructs in protoplasts and RNA from overexpression lines used high-resolution reverse transcription polymerase chain reaction (RT-PCR). AtPTB1 and AtPTB2 reduced inclusion/splicing of the potato invertase mini-exon splicing reporter, indicating that these proteins can repress plant intron splicing. Mutation of the polypyrimidine tract and closely associated Cytosine and Uracil-rich (CU-rich) sequences, upstream of the mini-exon, altered repression by AtPTB1 and AtPTB2. Coexpression of a plant orthologue of U2AF65 alleviated the splicing repression of AtPTB1. Mutation of a second CU-rich upstream of the mini-exon 3' splice site led to a decline in mini-exon splicing, indicating the presence of a splicing enhancer sequence. Finally, RT-PCR of AtPTB overexpression lines with c. 90 known alternative splicing (AS) events showed that AtPTBs significantly altered AS of over half the events. AtPTB1 and AtPTB2 are splicing factors that influence alternative splicing. This occurs in the potato invertase mini-exon via the polypyrimidine tract and associated pyrimidine-rich sequence.

A mass screening survey of cystic echinococcosis by ultrasonography, Western blotting, and ELISA among university students in Manisa, Turkey

Cystic echinococcosis (CE) is one of the most important zoonotic diseases in a wide geographic area, including Turkey. In the present project, a total of 4275 students from Celal Bayar University, Manisa, Turkey, were screened by ultrasonography (US) and specific antibodies for CE were examined by Western blotting (WB) and ELISA in finger prick blood samples of 2034 of 4275 volunteered students. We aimed to report the apparent prevalence of CE based on different diagnostic procedures and to compare WB and ELISA with US in diagnosis of CE in a mass screening setting. Six new cases were diagnosed as CE by US during the survey. In addition to these cases, three students were also detected to have been previously operated and pathologically confirmed for hepatic CE. US revealed parenchymal changes in these cases in concordance with their operation history; so, the prevalence of CE by US was calculated as 0.21% (9/4275) (95%CI, 0.11-0.39%) among university students in Manisa. Bands were detected at 8, 28, 32, 38, 42, 47, 70 and 90kDa by WB and the cases were considered to be positive for CE when at least three of the bands were seen together. Apparent prevalence of CE by ELISA and WB were found to be 2.11% (43/2034) (95%CI, 1.57-2.83%) and 0.25% (5/2034) (95%CI, 0.10-0.57%), respectively. Of the six US positive cases, WB was positive in only one case with two cysts in the liver. All of four cases with liver involvement were positive by ELISA. The high prevalence of CE among university students in Manisa indicated that CE is a major health problem in this area of Turkey. Our results supported that WB is rather difficult and not feasible as a mass screening test and may not be effective for confirmation especially in asymptomatic cases. As a result, we recommend US to be used initially in mass screening surveys for CE followed by confirmation by ELISA for suspected cases. Further examination primarily by chest X-ray followed by computed tomography and/or magnetic resonance imaging, if needed, should be recommended for US negative, ELISA and WB positive individuals who may have non-abdominal cysts.

Reflections on Lupus 2013: butterflies, wolves and prophecies

The recently concluded Tenth International Congress on Systemic Lupus Erythematosus (SLE) held in Buenos Aires was a resounding success. This overview summarizes some of the origins of the First International Congress held in Calgary, Canada in 1986, predictions offered by past Congress Presidents, and a perspective on the trends in autoantibody testing, which remains one of the key approaches to the early and accurate diagnosis of SLE. The last few decades have witnessed a remarkable proliferation of new diagnostic technologies including addressable laser bead immunoassays and, more recently, chemiluminescence and lateral flow technologies that could find a clinical niche in point-of-care diagnostics. Against the backdrop of these constantly emerging technologies, indirect immunofluorescence has remained the platform of choice for many laboratories and diagnosticians. The notion that autoantibodies are pathogenic has been challenged by evidence that some autoantibodies are protective, some may have catalytic capacity while others may be neutral or have no function at all. The latter notion of functionless or "junk" autoantibodies needs to be taken under some advisement, because there was a time when a great proportion of the human genome was considered to include "junk DNA". The butterfly as a symbol of hope and progress in SLE research over the past 27 years since the First International Congress on SLE is almost certainly to be even more appropriate when future Congresses are held in Geneva (2015), Melbourne (2017) and eventually one in 2050.

Monoclonal antibody-based dipstick assay: a reliable field applicable technique for diagnosis of Schistosoma mansoni infection using human serum and urine samples

A field applicable diagnostic technique, the dipstick assay, was evaluated for its sensitivity and specificity in diagnosing human Schistosoma mansoni infection. A monoclonal antibody (mAb) against S. mansoni adult worm tegumental antigen (AWTA) was employed in dipstick and sandwich ELISA for detection of circulating schistosome antigen (CSA) in both serum and urine samples. Based on clinical and parasitological examinations, 60 S. mansoni-infected patients, 30 patients infected with parasites other than schistosomiasis, and 30 uninfected healthy individuals were selected. The sensitivity and specificity of dipstick assay in urine samples were 86.7% and 90.0%, respectively, compared to 90.0% sensitivity and 91.7% specificity of sandwich ELISA. In serum samples, the sensitivity and specificity were 88.3% and 91.7% for dipstick assay vs. 91.7% and 95.0% for sandwich ELISA, respectively. The diagnostic efficacy of dipstick assay in urine and serum samples was 88.3% and 90.0%, while it was 90.8% and 93.3% for sandwich ELISA, respectively. The diagnostic indices of dipstick assay and ELISA either in serum or in urine were statistically comparable (P>0.05). In conclusion, the dipstick assay offers an alternative simple, rapid, non-invasive technique in detecting CSA or complement to stool examinations especially in field studies.

Analysis of the native structure, stability and aggregation of biotinylated human lysozyme

Fibril formation by mutational variants of human lysozyme is associated with a fatal form of hereditary non-neuropathic systemic amyloidosis. Defining the mechanistic details of lysozyme aggregation is of crucial importance for understanding the origin and progression of this disease and related misfolding conditions. In this study, we show that a biotin moiety can be introduced site-specifically at Lys33 of human lysozyme. We demonstrate, using biophysical techniques, that the structure and stability of the native-state of the protein are not detectably altered by this modification, and that the ability to form amyloid fibrils is unchanged. By taking advantage of biotin-avidin interactions, we show that super-resolution fluorescence microscopy can generate detailed images of the mature fibrils. This methodology can readily enable the introduction of additional probes into the protein, thereby providing the means through which to understand, in detail, the nature of the aggregation process of lysozyme and its variants under a variety of conditions.

Toward a new autoantibody diagnostic orthodoxy: understanding the bad, good and indifferent

Rapid advances in diagnostic technologies used to detect autoantibodies have made it difficult for even the most modern laboratory to keep abreast of the changing approaches and platforms, not to mention the clinicians who are hard pressed to keep abreast of evolving diagnostic paradigms attended by these newer techniques. While autoantibody testing is traditionally considered to be primarily serving the realm of diagnostic medicine, there is little doubt that autoantibodies are also being recognized as an approach to providing prognostic and therapeutic information. Accordingly, along with related proteomics, genomics and metabolomics, it is taking on increasing importance in the realm of personalized medicine. In today's world of autoantibody diagnostics, overarching concerns about false-negative and false-positive autoantibodies tests cannot be summarily dismissed by citing pros or cons of any one technology or diagnostic platform, but often point to persisting gaps in our knowledge about, and understanding of, the origin and roles of autoantibodies. Before we can hope to completely understand the enigmas that attend the results of autoantibody diagnostic tests, perhaps it is time to step back and re-examine long-accepted paradigms and beliefs. This review will address some of the issues that impact on autoantibody detection technologies and some of the considerations and issues that will attend a new orthodoxy of autoantibody diagnostics. These issues will be addressed in the context of "bad" (pathogenic), "good" (protective) or "indifferent" (no apparent role in disease) autoantibodies.

Metformin increases phagocytosis and acidifies lysosomal/endosomal compartments in AMPK-dependent manner in rat primary microglia

Recent evidence suggests that metformin shows beneficial effects in experimental models of neuroinflammatory diseases. The aim of the present study was to determine the effect of metformin on phagocytosis and acidification of lysosomal/endosomal compartments in rat primary microglia in the presence of lipopolysaccharide (LPS) and/or beta-peptides (25-35), (1-40), and (1-42). Metformin increased the phagocytosis of fluorescent microspheres in the presence or absence of all the beta-peptides. However, the drug had no effect on the phagocytosis in LPS-stimulated microglia regardless of the presence of all the beta-peptides. Metformin acidified the lysosomal/endosomal compartments in the presence or absence of the beta-peptide 1-40 in both resting and activated microglia. To elucidate the mechanism of metformin action, we used 5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside as an activator of adenosine monophosphate-activated protein kinase (AMPK) and compound C as a confirmed pharmacological inhibitor of AMPK. We have shown that metformin increased AMPK activity in microglial cells and that all observed effects are AMPK-dependent because the pretreatment of microglia with compound C reversed the effects of the drug. Since degradation of proteins in lysosomal/endosomal compartments depends largely on their phagocytosis and acidification, metformin may be beneficial in proteinopathies affecting the brain.

Ambivalent effects of compound C (dorsomorphin) on inflammatory response in LPS-stimulated rat primary microglial cultures

It was proven that compound C displays beneficial effects in models of inflammatory-induced anemia, ischemic stroke, and fibrodysplasia ossificans progressiva. Compound C influence on microglia, playing a major role in neuroinflammation, has not been evaluated yet. The aim of the present study was to determine the effect of compound C on cytokine release, NO, and reactive oxygen species (ROS) production. The rat microglial cultures were obtained by shaking the primary mixed glial cultures. Cytokine and nitrite concentrations were assayed using ELISA kits. ROS were assayed with nitroblue tetrazolium chloride. AMPK activity was assayed using the SAMS peptide. The expression of arginase I, NF-kappaB p65, and hypoxia-inducible factor-1 alpha (HIF-1 alpha) was evaluated using Western blot. Compound C displayed ambivalent effect depending on microglia basal activity. It up-regulated the release of TNF alpha and NO production and increased the expression of arginase I in non-stimulated microglia. However, compound C down-regulated IL-1 beta, IL-6 and TNF alpha release, NO, ROS production, and AMPK activity, diminished NF-kappaB and HIF-1 alpha expression, as well as increased arginase I expression in lipopolysaccharide (LPS)-stimulated microglia. Compound C did not affect iNOS expression and IL-10 and TGF-beta release in non-stimulated and LPS-stimulated microglia. The observed alterations in the release or production of inflammatory mediators may be explained by the changes in NF-kappaB, HIF-1 alpha, and arginase I expression and 3-(4,5-dimethylthazol-2-yl)-2,5-diphenyltetrazolinum bromide values in response to LPS, whereas the basis for the compound C effect on non-stimulated microglia remains to be investigated.

Protective role of unconjugated bilirubin on complement-mediated hepatocytolysis

Hyperbilirubinemia and complement-mediated immune attack on hepatocyte membrane are common features of certain hepatic diseases. To assess whether unconjugated bilirubin (UB) counteracts complement-mediated hepatocytolysis, we first generated a rabbit polyclonal antibody (Ab) against rat hepatocyte plasma membrane (RHPM). An assay performed with isolated rat hepatocytes in the presence of the polyclonal Ab and rat serum as complement donor demonstrated that UB inhibits cell lysis, as lactate dehydrogenase release into the medium was inhibited by the pigment in a dose-dependent manner. Immunofluorescence microscopy studies showed that UB significantly attenuates the binding of C3 to the hepatocyte-Ab complex. Further enzyme immunoassay studies showed that UB interferes the binding of C1q to purified anti-RHPM IgG, also in a dose-dependent manner. A dot-blot assay showed that [14C]-UB binds to C1q and human serum albumin (HSA) to a similar extent. A differential spectrum analysis of UB in the presence of C1q further confirmed that the pigment interacts with this protein. In conclusion, we demonstrated an inhibitory action of UB on complement-mediated Ab-induced hepatocytolysis, this action being evidenced at pathophysiological pigment concentrations (171 microM and higher). A direct binding of the pigment to C1q is likely involved.

Albumin in Immunohistochemistry: Foe and Friend

Immunohistochemical procedures constitute a high methodological value in both pathologic diagnostics and research. Staining quality depends on a large variety of interference factors. Primarily, background staining reduces the quality of evaluation by reducing the chromatic discrimination. For the identification of important interference factors, various incubation steps and composition of solutions recommended in routine protocols were altered or omitted in our study. Surprisingly, the most important effect concerning background staining reduction could be significantly attributed to the omission of albumin which usually is recommended as a reducer of background stainings. However, in contrast to this negative effect, albumin could also increase specific staining intensity. These findings lead to the recommendation of a careful use of albumin in immunohistochemistry because of the dichotomous effects mentioned above. Furthermore, these results imply that in case of a good specific staining pattern, the use of albumin in immunohistochemical solutions merely exerts significant negative background staining effects.

Development and application of an indirect ELISA test for the detection of antibodies to Mycoplasma crocodyli infection in crocodiles (Crocodylus niloticus)

Non-availability of a standardized rapid serodiagnostic test for quick and accurate diagnosis of Mycoplasma crocodyli (M. crocodyli) infection in crocodiles was the underlining reason for conducting the present study. An indirect enzyme-linked immunosorbent assay (iELISA) for the detection of antibodies (Ab) to M. crocodyli infection in crocodile sera was developed using sonicated antigen (Ag) and anti-crocodile conjugate. The iELISA test was optimised with different reagents and at different steps. A cut-off value of percent positive greater than or equal to 53.47% resulted in an estimated sensitivity and specificity of 85.67 and 100%, respectively. The developed iELISA could be used for detection of Abs to M. crocodyli infection in crocodiles and may enable to understand the transmission of the disease.

Application of a circulating antigen detection immunoassay for laboratory diagnosis of extra-pulmonary and pulmonary tuberculosis

BACKGROUND

Diagnosis of extra-pulmonary tuberculosis is often difficult to establish using standard methods. Recently, a 55-kDa mycobacterial antigen was identified in sera of individuals with pulmonary TB using a simple and rapid dot-ELISA based on monoclonal antibody (TB-55 mAb). Here, we have evaluated the application of the dot-ELISA for the detection of target antigen in sera of individuals with extra-pulmonary TB.

METHODS

The Western blot and indirect immunoperoxidase staining was used to identify the target TB antigen using the TB-55 mAb. The dot-ELISA was used to detect the target antigen in serum samples.

RESULTS

The target antigen was identified at 55-kDa molecular weight in serum, ascitic fluid and CSF samples from individuals with extra-pulmonary TB. The purified antigen from these samples showed similar biochemical properties to the previously described antigen. The target antigen was localized in areas without caseous necrosis in lymph tissues. The dot-ELISA detected the target antigen in 90% sera of individuals with extra-pulmonary TB and in 87% sera of individuals with pulmonary TB with a specificity of 97% among control individuals.

CONCLUSION

The detection of the 55-kDa antigen using dot-ELISA can be routinely employed to support clinical diagnosis of extra-pulmonary TB and pulmonary TB.

Production and characterization of monoclonal antibodies against formalin-inactivated Nipah virus isolated from the lungs of a pig

Eight clones of monoclonal antibodies (Mabs) to Nipah virus (NV) were produced against formalin-inactivated NV antigens. They reacted positive by indirect immunofluorescent antibody test, and one of them also demonstrated virus neutralizing activity. They were classified into six different types based on their biological properties. These Mabs will be useful for immunodiagnosis of NV infections in animals and further research studies involving the genomes and proteins of NV.

Immunosensors for pesticide analysis: antibody production and sensor development

Immunosensors, a type of affinity biosensor, are based on the binding interactions between an immobilized biomolecule (antibody/antigen) on the electronic transducer surface with the analyte of interest (antigen/antibody), resulting in a detectable signal. The sensor system takes advantage of the high selectivity provided by the molecular recognition characteristic of an antibody, which binds reversibly with a specific antigen. This review article presents the current status of immunosensors, highlighting their potential benefits and limitations for pesticide analysis. The basic criteria for generating specific antibodies against low-molecular-mass pesticides, which are usually nonimmunogenic in nature, are briefly discussed. The article also describes the fundamentals of important transducer technologies and their use in immunosensor development.

Activation of cellulose membranes with 1,1'-carbonyldiimidazole or 1-cyano-4-dimethylaminopyridinium tetrafluoroborate as a basis for the development of immunosensors

Methods for the activation of a cellulose dialysis membrane for immunosensor applications have been developed. For activation two reagents, 1,1'-carbonyldiimidazole (CDI) and 1-cyano-4-dimethylaminopyridinium tetrafluoroborate (CDAP), were compared with respect to the coupling efficiency for glucose oxidase (GOx) and 1,8-diamino-2,6-dioxaoctane. The maximum level of activation was 2.4 micromol cm(-2) for CDI and 0.2 micromol cm(-2) for CDAP activation. We observed 1.5 microg cm(-2) and 0.4 x 10(-4) U cm(-2) GOx with CDI-activated membranes whereas 1.7 microg cm(-2) and 7.2 x 10(-4) U cm(-2) GOx were observed with CDAP-activated membranes. With 1,8-diamino-2,6-dioxaoctane amino group densities of 0.165 and 0.09 micromol cm(-2) were observed via CDI and CDAP activation, respectively. An amino-modified membrane was used for coupling a ligand (pentapeptide) and an immunoenzymometric assay for hemoglobin A1c was carried out.

Preliminary studies by ELISA on the antigen and antibody dynamics in the early stages of experimental infections with Trypanosoma evansi in cattle

Six 6-month-old bulls were experimentally infected with five different isolates of Trypanosoma evansi; two received the same isolate and the other four received different isolates. The parasitaemias and serum antigen levels were monitored regularly by the haematocrit centrifuge technique (HCT) and antigen-detection ELISA (Ag-ELISA), respectively. Trypanosomal antigen was demonstrated by the Ag-ELISA by 10-14 days post inoculation in four cattle, while parasitaemias were first found to be positive in individual cattle over a longer period of time post inoculation (6-28 days). In two cattle, the Ag-ELISA values were also positive when the animals were found to harbour trypanosomes by the HCT and only turned negative 3 days after treatment, while the ELISA values fluctuated during the experiment in another two bulls. The remaining two cattle never produced positive ELISA results despite positive parasitological results. The antibody titres in all six cattle started to rise around 10 days post inoculation and then stayed high throughout the experiment. It was concluded that the Ag-ELISA would produce some false negative results in the early stages of T. evansi infection owing to variations in the balance of parasitaemia and antibody levels in the circulation, and in the pathogenicity of parasite strains.

Formulation and characterisation of Bordetella pertussis fimbriae as novel carrier proteins for Hib conjugate vaccines

Haemophilus influenzae type b (Hib) capsular polysaccharide (polyribosylribitol phosphate, PRP) is the active component of conjugate vaccines that have proven successful in preventing invasive Hib disease. Conjugation of PRP to a protein carrier greatly improves its immunogenicity providing protection in infants and subsequent antibody maturation upon boosting. In this study, fimbriae isolated from Bordetella pertussis have been assessed as novel carrier proteins. These proteins are components of some acellular pertussis vaccines and clinical trials have indicated that fimbriae could be important protective antigens against whooping cough. Fimbriae (Fim2 and Fim3) purified from B. pertussis were dissociated in 6 M guanidine hydrochloride, pH 10.5, to produce proteins of defined size and to facilitate the production and characterisation of the conjugates. Both carbodiimide-mediated coupling and reductive amination were used to conjugate PRP to dissociated fimbriae. Efficiency of conjugation was determined by size exclusion chromatography followed by protein and polysaccharide analysis of fractionated components. Immunisation of rabbits with dissociated fimbriae-PRP conjugates (D.fim-PRP) produced high anti-fimbrial and anti-PRP IgG titres. Use of a D.fim-PRP conjugate could protect against Hib disease and may also augment protection against B. pertussis.

Analysis of human self-reactive antibody repertoires by quantitative immunoblotting

We review the use of a quantitative immunoblotting technique to characterize human self-reactive antibody repertoires in health and disease. The interactions of plasma IgM and IgG with tissue extracts as sources of self-antigens were analyzed by quantitative immunoblotting. Data were compared by means of multiparametric statistical analysis. The data summarized here demonstrate that natural self-reactive antibody repertoires of healthy individuals are restricted to a limited subset of immunodominant autoantigens that is selected early in development, and remains conserved between individuals through ageing. The selection of human natural self-reactive IgG antibody repertoires requires normal T-/B-cell interactions. The immunoblotting assay has the potential to distinguish between autoimmune diseases with organ-related oligoclonal expansion of self-reactive clones and those characterized by broad alterations of immunoregulation. However, organ-specific autoimmune diseases may be characterized by altered patterns of antibody repertoires unrelated to the target organ. The assay also revealed an unexpected defect in the regulatory function of self-reactive IgM on the expression of self-reactive IgG repertoires in several systemic and organ-specific autoimmune diseases. The results are discussed in the light of our current understanding of the processes of selection of self-reactive B-cells and the pathophysiology of autoimmunity.