Quantitation of rheumatoid factors by enzyme immunoassay using biotinylated human IgG

Surface Modification of Biodegradable Microparticles with the Novel Host-Derived Immunostimulant CPDI-02 Significantly Increases Short-Term and Long-Term Mucosal and Systemic Antibodies against Encapsulated Protein Antigen in Young Naïve Mice after Respiratory Immunization

Generating long-lived mucosal and systemic antibodies through respiratory immunization with protective antigens encapsulated in nanoscale biodegradable particles could potentially decrease or eliminate the incidence of many infectious diseases, but requires the incorporation of a suitable mucosal immunostimulant. We previously found that respiratory immunization with a model protein antigen (LPS-free OVA) encapsulated in PLGA 50:50 nanoparticles (~380 nm diameter) surface-modified with complement peptide-derived immunostimulant 02 (CPDI-02; formerly EP67) through 2 kDa PEG linkers increases mucosal and systemic OVA-specific memory T-cells with long-lived surface phenotypes in young, naïve female C57BL/6 mice. Here, we determined if respiratory immunization with LPS-free OVA encapsulated in similar PLGA 50:50 microparticles (~1 μm diameter) surface-modified with CPDI-02 (CPDI-02-MP) increases long-term OVA-specific mucosal and systemic antibodies. We found that, compared to MP surface-modified with inactive, scrambled scCPDI-02 (scCPDI-02-MP), intranasal administration of CPDI-02-MP in 50 μL sterile PBS greatly increased titers of short-term (14 days post-immunization) and long-term (90 days post-immunization) antibodies against encapsulated LPS-free OVA in nasal lavage fluids, bronchoalveolar lavage fluids, and sera of young, naïve female C57BL/6 mice with minimal lung inflammation. Thus, surface modification of ~1 μm biodegradable microparticles with CPDI-02 is likely to increase long-term mucosal and systemic antibodies against encapsulated protein antigen after respiratory and possibly other routes of mucosal immunization.

Development of a Scrub Typhus Diagnostic Platform Incorporating Cell-Surface Display Technology

Scrub typhus (ST), also known as tsutsugamushi disease and caused by rickettsia Orientia tsutsugamushi, is an underestimated fatal epidemic in the Asia-Pacific region, resulting in a million human infections each year. ST is easily misdiagnosed as clinical diagnosis is based on non-specific skin eschar and flu-like symptoms. Thus, the lack of accurate, convenient, and low-cost detection methods for ST poses a global health threat. To address this problem, we adopted baculovirus surface-display technology to express three variants of TSA56, the major membrane antigen of O. tsutsugamushi, as well as the passenger domain of ScaC (ScaC-PD), on insect Sf21 cell surfaces rather than biosafety level 3 bacteria in an enzyme-linked immunosorbent assay (ELISA). Recombinant TSA56 and ScaC-PD were all properly expressed and displayed on Sf21 cells. Our cell-based ELISA comprising the four antigen-displaying cell types interacted with monoclonal antibodies as well as serum samples from ST-positive field-caught rats. This cell-based ELISA presented high accuracy (96.3%), sensitivity (98.6%), and specificity (84.6%) when tested against the ST-positive rat sera. Results of a pilot study using human sera were also highly consistent with the results of immunofluorescence analyses. By adopting this approach, we circumvented complex purification and refolding processes required to generate recombinant O. tsutsugamushi antigens and reduced the need for expensive equipment and extensively trained operators. Thus, our system has the potential to become a widely used serological platform for diagnosing ST.

Pilot Production of SARS-CoV-2 Related Proteins in Plants: A Proof of Concept for Rapid Repurposing of Indoor Farms Into Biomanufacturing Facilities

The current CoVid-19 crisis is revealing the strengths and the weaknesses of the world's capacity to respond to a global health crisis. A critical weakness has resulted from the excessive centralization of the current biomanufacturing capacities, a matter of great concern, if not a source of nationalistic tensions. On the positive side, scientific data and information have been shared at an unprecedented speed fuelled by the preprint phenomena, and this has considerably strengthened our ability to develop new technology-based solutions. In this work, we explore how, in a context of rapid exchange of scientific information, plant biofactories can serve as a rapid and easily adaptable solution for local manufacturing of bioreagents, more specifically recombinant antibodies. For this purpose, we tested our ability to produce, in the framework of an academic lab and in a matter of weeks, milligram amounts of six different recombinant monoclonal antibodies against SARS-CoV-2 in Nicotiana benthamiana. For the design of the antibodies, we took advantage, among other data sources, of the DNA sequence information made rapidly available by other groups in preprint publications. mAbs were engineered as single-chain fragments fused to a human gamma Fc and transiently expressed using a viral vector. In parallel, we also produced the recombinant SARS-CoV-2 N protein and the receptor binding domain (RBD) of the Spike protein in planta and used them to test the binding specificity of the recombinant mAbs. Finally, for two of the antibodies, we assayed a simple scale-up production protocol based on the extraction of apoplastic fluid. Our results indicate that gram amounts of anti-SARS-CoV-2 antibodies could be easily produced in little more than 6 weeks in repurposed greenhouses with little infrastructure requirements using N. benthamiana as production platform. Similar procedures could be easily deployed to produce diagnostic reagents and, eventually, could be adapted for rapid therapeutic responses.

Computational models in immunological methods: an historical review

The utilization of computational models in immunology dates from the birth of the science. From the description of antibody-antigen binding to the structural models of receptors, models are utilized to bring fundamental understandings of the processes together with laboratory measurements to uncover implications of these data. In this review, an historical view of the role of computational models in the immunology laboratory is presented, and short mathematical descriptions are given of fundamental assays. In addition, the range of current uses of models is explored -- especially as seen through papers which have appeared in the Journal of Immunological Methods from volume 1 (1971/1972) to volume 208 (1997). Each paper which introduced a new mathematical, statistical, or computer simulation model, or introduced an enhancement to an instrument through a model in those volumes is cited and the type of computational model noted.

An ELISA for blood group specific exoglycosidases

An enzyme-linked immunosorbent assay (ELISA) for studying erythrocyte A, B and H epitope specific exoglycosidases is described. Human blood type B erythrocyte membranes and Coffea canephora alpha-D-galactosidase were used as a model. Membrane coated microtiter wells were incubated with exoglycosidase, probed with IgM monoclonal antibody, and then with anti-murine mu chain specific alkaline phosphatase conjugate. The assay is useful for studying exoglycosidase modification of the A, B and H epitopes on human erythrocyte membranes as well as in screening prokaryotic and eukaryotic extracts for blood group active enzymes. Furthermore, this technique has the advantage of simplicity, sensitivity, and objectivity of data interpretation.

Automated turbidimetry of rheumatoid factor without heat inactivation of serum

We describe an improved turbidimetric procedure for rheumatoid factor measurement in human serum. Heat-aggregated human IgG is used as antigen. Interference produced by the complement component C1q, which required a previous heat pretreatment of sera, is avoided by the addition of the chemical inhibitor, poly(vinyl sulphonic acid). This inhibitor eliminates C1q interference without affecting the attachment of rheumatoid factor to the Fc part of IgG, thus permitting full automation of the assay. After studying the reactivity of different heat-aggregated IgG preparations, we optimized the procedure for preparing the antigen in order to attain maximal reactivity: IgG was heated at 63 degrees C until the absorbance at 340 nm of a 1/10 dilution of the antigen lay between 0.65 and 0.95 absorbance units. The study of antigen stability showed a maximum aggregation two weeks after preparation. The antigen was then stable and could be used in the assay. The standard curve extends from 30 to 500 x 10(3) IU/l. Intra- and inter-assay CV were less than 5.5%. Relative analytical sensitivity and specificity were 98.3% and 95.2%, respectively. The results agreed well with those obtained by the non-improved turbidimetric procedure (r = 0.996) and with nephelometry values on the Behring nephelometer analyser (r = 0.964). The correlation with an enzyme immunoassay was also good (r = 0.923).

Quantitation of canine distemper virus and antibodies by enzyme-linked immunosorbent assays using protein A and monoclonal antibody capture

Monoclonal antibodies produced from 19 cloned hybridomas were selected for this study. Specific canine distemper virus (CDV) antibodies in medium from cloned hybridomas were detected by direct enzyme-linked immunosorbent assays (ELISA) and by indirect immunofluorescence. Three different sandwich ELISA systems were developed either to detect CDV in cell cultures and clinical specimens or to detect specific antibody in canine sera. Protein A and monoclonal antibodies attached in sequence to a solid phase constituted the capture system in the assays. Viral antigens were detected by sandwiching extracts of clinical specimens (or infected cell cultures), monoclonal antibody, and peroxidase-labeled protein A in sequence onto the capture layer. In 1 procedure, biotin-labeled antibody and peroxidase-labeled avidin were used as the last 2 layers in the assay. The CDV antibodies in dog sera were quantitated in a similar manner, but the sequential sandwiching levels consisted of partially purified CDV, serum specimen, and peroxidase-labeled protein A, respectively. The procedures were specific and highly sensitive.

Purification of mouse haptoglobin by antibody affinity chromatography and development of an ELISA to measure serum haptoglobin levels

Mouse haptoglobin was isolated from acute-phase serum initially by affinity chromatography on haemoglobin-Sepharose. This proved inefficient, but sufficient material was obtained for use as an immunogen. Rabbit anti-haptoglobin antibodies were used as immunoabsorbents to isolate larger quantities of haptoglobin. Subsequently, specific anti-haptoglobin antibodies were prepared by affinity chromatography on haptoglobin-Sepharose. A direct sandwich ELISA for mouse serum haptoglobin was developed, using affinity purified reagents. The working range of the haptoglobin standard curve was 0.02-0.5 microgram/ml. The reagents did not cross-react with albumin or haemoglobin and the antibody also recognised rat haptoglobin.

A useful method for determining class-specific rheumatoid factors with computerized analyses of data

A simple and sensitive enzyme-linked immunosorbent assay (ELISA) was developed to determine rheumatoid factors (RFs) of IgG, IgA and IgM class. Standardisation was performed with a standard reference serum for IgM-RF, calibrated according to the WHO preparation, and with the serum of a patient containing high levels of IgA- and IgG-RF. The sigmoidal shaped calibration curve was fitted with a computerized four parameter logistic model with simplified mathematical computations. This method provided to be more accurate for measuring RF levels, as judged by the smaller residuals, than logit or log-linear transformations. The considerable reduction in processing time, which is obtained by the computerized analysis of data, makes this method of class-specific RF determination suitable for routine analysis.

Quantitation of indirect sandwich enzyme-linked immunosorbent assay parameters

The optimization of data from the indirect sandwich enzyme-linked immunosorbent assay has been commonly accomplished by linear regression analysis, even though the data are often essentially sigmoid. A new microcomputer software program (LISACRV) that uses a nonlinear regression statistical model to analyze the data from enzyme-linked immunosorbent assay titration experiments was developed.

Comparative studies on RF-IgA and RF-IgM ELISA--human or rabbit IgG as antigen?

In the literature it is seen that the antigens used in Elisa test for rheumatoid factors (RF) are either human IgG, rabbit IgG, or mouse IgG. We investigated RF-IgA activity in 55 serum samples using either human IgG or rabbit IgG as antigen. In other 76 serum samples we investigated RF-IgM activity using either human IgG or rabbit IgG as antigen. In RF-IgA the median AU/ml is found a factor 2-3 times higher using rabbit IgG as antigen. The discriminatory power of the RF-IgA Elisa test is better using rabbit IgG as antigen. In RF-IgM Elisa the results are different using human or rabbit IgG as antigen. Our investigation illustrates some of the problems in Elisa testing for RF's. We conclude that the variations are influenced by the antigen source, being rabbit or human IgG. This might affect the daily and scientific communication between different laboratories and/or clinical departments. Results obtained by one antigen cannot easily be compared with results obtained with the other antigen. This means that the user of the results has to be aware of the antigen used, and it seems most important to develop some kind of standardization in the Elisa tests used.