Production and characterization of anti-human IgG F(ab')2 antibody fragment

Development and Characterization of Guinea Pig Anti-Insulin Polyclonal Antibody

Development and characterization of guinea pig anti-insulin polyclonal antibody against a target-specific insulin antigen. In India, an insulin immunogenicity kit for detecting insulin antibodies (neutralizing Nab) is an unmet medical need for diabetic patient's routine diagnosis. Type 1 diabetics rely on insulin injections daily basis for survival; if the body develops anti-insulin antibodies and neutralizes the exogenous recombinant insulin, glucose control is lost, and the patient eventually dies. Antibodies are excellent diagnostic reagents due to the specificity and sensitivity they provide in recognizing specific and unique target antigens. The paper describes the use of insulin as a target antigen and the development of target (insulin) specific antibodies in guinea pigs for use as a positive control for immunogenicity kit validation. Anti-insulin polyclonal antibody was raised against insulin in the Dunkin Hartley guinea pigs host. Anti-insulin antibody titer of all bleeds from four animals was tested using an indirect ELISA assay format. All four animals responded to the target-specific antigen but only one animal (#4) responded with a high-affinity antibody titer. The hyperimmune sera were purified using a protein A column. The purified anti-insulin antibody was characterized through SDS Page and western blot. The specificity, reactivity, and antibody binding efficiency were confirmed through immunoassays. Guinea pig anti-insulin polyclonal antibody developed in this study showed good specificity, reactivity, and efficiency in the immunoassays. This paper describes the development and characterization of anti-insulin antibodies for use as a control in developing a user-friendly insulin immunogenicity kit.

Quantifying LAGA mutated mouse IgG2a monoclonal antibody with a rapid pepsin digestion enabled immunoaffinity LC/MS/MS assay

A sensitive and specific bioanalytical method was required to measure the exposure of a LAGA-mutated surrogate mouse IgG2a monoclonal antibody in mouse plasma, but the lack of highly specific reagents for the LAGA mutant hindered the development of a ligand-binding assay. Equally problematic is that no sensitive unique tryptic peptides suitable for quantitative mass spectrometric analysis could be identified in the mIgG2a complementarity-determining regions. To overcome these challenges, a trypsin alternative pepsin, an aspartic protease, was systematically investigated for its use in digesting the mutated mIgG2a antibody to allow generation of signature peptides for the bioanalytical quantification purpose. After a series of evaluations, a rapid one-hour pepsin digestion protocol was established for the mutated Fc backbone. Consequently, a new pepsin digestion-based liquid chromatography-tandem mass spectrometry (LC/MS/MS) method was successfully developed to support the mouse pharmacokinetic (PK) sample analysis. In brief, robust and reproducible C-terminal cleavage of both leucine and phenylalanine near the double mutation site of the mutated mIgG2a was accomplished at pH ≤2 and 37°C. Combined with a commercially available rat anti-mIgG2a heavy-chain antibody, the established immunoaffinity LC/MS/MS assay achieved a limit of quantitation of 20 ng/mL in the dynamic range of interest with satisfactory assay precision and accuracy. The successful implementation of this novel approach in discovery PK studies eliminates the need for tedious and costly generation of specific immunocapturing reagents for the LAGA mutants. The approach should be widely applicable for developing popular LAGA mutant-based biological therapeutics.

Evaluation of Cellular Targeting by Fab' vs Full-Length Antibodies in Antibody-Nanoparticle Conjugates (ANCs) Using CD4 T-cells

Targeted delivery of chemotherapeutic drugs can improve their therapeutic efficiency by localizing their toxic effects at the diseased site. This is often achieved either by direct conjugation of drugs to antibodies targeting overexpressed receptors on cancer cells (antibody-drug conjugates/ADCs) or by conjugating antibodies to nanoparticles bearing drugs (antibody-nanoparticle conjugates/ANCs). Here, we report a platform for utilizing hinge cysteines on antigen-binding fragment (Fab') of an anti-CD4 antibody for site-specific conjugation to nanoparticles giving rise to anti-CD4 Fab'-nanoparticle conjugates (Fab'-NCs). We demonstrate a convenient route for obtaining functional anti-CD4 Fab' from full-length antibody and examine the targeted delivery efficiencies of anti-CD4 Fab'-NCs vs ANCs for selective delivery to CD4high mT-ALL cells. Our results indicate that higher avidity of full-length anti-CD4 antibody, i.e., protein alone translated to higher binding ability to CD4high mT-ALL cells in comparison with anti-CD4 Fab' alone. However, the targeted delivery efficiency of anti-CD4 Fab'-NCs was comparable to ANCs indicating that the avidity of Fab' is restored in a nanoparticle-conjugate format. Fab'-NCs are equally capable of achieving targeted drug delivery to CD4high T-cells as ANCs and are a versatile alternative to ANCs by offering site-selective modification strategy while retaining their advantages.

Clinical leishmaniosis in a captive Eurasian otter (Lutra lutra) in Spain: a case report

Background

Captive and free-ranging wild mammals have been recognized as potential reservoirs of Leishmania infantum infection. The aim of this study was to describe the first clinical case of leishmaniosis in the Eurasian otter.

Case presentation

A case of clinical leishmaniosis is reported in a 4-year-old male Eurasian otter housed at a wildlife park (Murcia, South Eastern Spain). The Eurasian otter showed bilateral epistaxis, anorexia, apathy, and weight loss. A complete blood cell count and biochemical analyses revealed hyperproteinemia, hyperglobulinemia, decreases of paraoxonase-1, increases of haptoglobin and ferritin, and proteinuria. Bilateral nephropathy with hydronephrosis, mesenteric lymphadenomegaly, and ascites were also observed. L. infantum infection was confirmed by microscopy (amastigotes were detected in macrophages from spleen aspirate), molecular diagnosis (L. infantum DNA was detected by real-time polymerase chain reaction), and serology (anti-Leishmania IgG2 antibodies were detected by time-resolved immunofluorometry). The animal was treated with allopurinol for 3 months and gained weight, the epistaxis disappeared, and the ferritin concentration decreased.

Conclusions

This is the first report of clinical leishmaniosis in the Eurasian otter. Our results suggest that Eurasian otters are susceptible to infection with L. infantum and can develop clinical leishmaniosis in endemic areas.

Noninvasive Evaluation of CD20 Expression Using 64Cu-Labeled F(ab')2 Fragments of Obinutuzumab in Lymphoma

CD20-overexpressed non-Hodgkin lymphoma typically indicates progressive malignancy. Obinutuzumab is a next-generation Food and Drug Administration-approved humanized monoclonal antibody that targets CD20. Previous studies with ⁸⁹Zr-labeled obinutuzumab have successfully imaged CD20 in vivo. However, delayed tumor uptake and increased radioactive exposure caused by long blood circulation limit its clinical translation. This study aimed to develop ⁶⁴Cu-labeled F(ab')₂ fragments of obinutuzumab for imaging CD20 in lymphoma xenograft tumor models. Methods: F(ab')₂ fragments were produced from obinutuzumab using an IgG-degrading enzyme of Streptococcus pyogenes (IdeS) enzyme and purified with protein A beads. Sodium dodecyl sulfate polyacrylamide gel electrophoresis and high-performance liquid chromatography were performed to evaluate the products and their stability. F(ab')₂ products were conjugated with p-SCN-Bn-NOTA (NOTA) for ⁶⁴Cu radiolabeling. Western blotting was performed to screen the CD20 expression levels of lymphoma cells. Enzyme-linked immunosorbent assay, flow cytometry, and confocal imaging were used to test the binding affinity in vitro. Serial PET imaging and biodistribution studies in subcutaneous lymphoma-bearing mice were performed using ⁶⁴Cu-NOTA-F(ab')₂-obinutuzumab or ⁶⁴Cu-NOTA-F(ab')₂-IgG. Results: F(ab')₂-obinutuzumab and F(ab')₂-IgG produced by the IdeS digestion system were confirmed with sodium dodecyl sulfate polyacrylamide gel electrophoresis and high-performance liquid chromatography. The radiochemical purity of ⁶⁴Cu-labeled F(ab')₂ fragments was no less than 98%, and the specific activity was 56.3 ± 7.9 MBq/mg (n = 6). Among the 5 lymphoma cell lines, Ramos showed the strongest expression of CD20, and CLL-155 showed the lowest, as confirmed by enzyme-linked immunosorbent assay, flow cytometry, and confocal imaging. PET imaging revealed rapid and sustained tumor uptake of ⁶⁴Cu-NOTA-F(ab')₂-obinutuzumab in Ramos tumor-bearing mice. The peak tumor uptake (9.08 ± 1.67 percentage injected dose per gram of tissue [%ID/g]) in the Ramos model was significantly higher than that in the CCL-155 model (2.78 ± 0.62 %ID/g) or the ⁶⁴Cu-NOTA-F(ab')₂-IgG control (1.93 ± 0.26 %ID/g, n = 4, P < 0.001). The tumor-to-blood and tumor-to-muscle ratios were 7.3 ± 1.6 and 21.9 ± 9.0, respectively, at 48 h after injection in the ⁶⁴Cu-NOTA-F(ab')₂-obinutuzumab group. Of the measured off-target organs, the kidneys showed the highest uptake. Ex vivo immunofluorescent staining verified the differential CD20 expression in the Ramos and CCL-155 tumor models. Conclusion: This study demonstrated that ⁶⁴Cu-NOTA-F(ab')₂-obinutuzumab had a rapid and sustained tumor uptake in CD20-positive lymphoma with high contrast, which could enable noninvasive evaluation of CD20 levels in the clinic.

Development and characterization of polyclonal antibody against human kappa light chain in rabbit

Polyclonal antibodies against kappa light chain are used to diagnose diseases producing free light chain. The kappa and lambda light chains are products of immunoglobulin synthesis and released into the circulation in minor amounts such as serum, cerebrospinal fluid, urine and synovial fluid in normal condition. The purpose of this study was the production and purification of polyclonal immunoglobulin G (IgG) against human kappa light chains. In this study, early human IgG was purified by ion-exchange chromatography, reduced with Dithiothreitol and heavy and light chains were separated with size-exclusion chromatography. Afterward, affinity chromatography with protein L Sepharose at pH 2.00 was displayed to be a dominant condition for the separation and purification of the kappa light chain of immunoglobulins from human serum. Eventually, the rabbit was immunized by human kappa light chains. The rabbit IgG was purified and labeled with horseradish peroxidase (HRP). Direct enzyme-linked immunosorbent assay was planned to determine the titer of HRP conjugated rabbit IgG against the human kappa light chain. The optimum titer of anti-kappa IgG was 1:16000. At the result, purified polyclonal anti-kappa is useful tool in biomedical and biochemical researches and diagnostic kits.