Development of Label-Free Immunoassays as Novel Solutions for the Measurement of Monoclonal Antibody Drugs and Antidrug Antibodies

BACKGROUND

Immunoassays based on label-free technologies (label-free immunoassay [LFIA]) offer an innovative approach to clinical diagnostics and demonstrate great promise for therapeutic drug monitoring (TDM) of monoclonal antibody (mAb) drugs. An LFIA measures immunocomplex formation in real time and allows for quantification on initial binding rate, which facilitates fast measurement within a few minutes.

METHODS

Based on thin-film interferometry (TFI) technology, open-access LFIAs were developed for the quantification of the mAb drugs adalimumab (ADL) and infliximab (IFX) and for the detection of the antidrug antibodies (ADAs) to the mAb drugs (ADL-ADAs and IFX-ADAs).

RESULTS

The LFIAs for active mAb drugs (ADL and IFX) and for ADAs (ADL-ADAs and IFX-ADAs) were validated. The analytical measurement range (AMR) for both ADL and IFX was from 2 to 100 μg/mL. The AMR for ADL-ADAs was from 5 to 100 μg/mL and for IFX-ADAs was 10 to 100 μg/mL. In the comparison of LFIAs and reporter gene assays, the correlation coefficient was 0.972 for the quantification of ADL and 0.940 for the quantification of IFX. The concordance rate was 90% for the detection of ADL-ADAs and 76% for the detection of IFX-ADAs.

CONCLUSIONS

The LFIAs for active mAb drugs and ADAs were appropriate for the TDM of ADL and IFX. The TFI technology has unique advantages compared with other technologies used for the measurement of mAb drugs. Label-free technologies, especially those allowing for open-access LFIAs, have great potential for clinical diagnostics.

Human cancer immunotherapy with antibodies to the PD-1 and PD-L1 pathway

The programmed death 1 (PD-1) receptor and its ligands programmed death ligand 1 (PD-L1) and PD-L2, members of the CD28 and B7 families, play critical roles in T cell coinhibition and exhaustion. Overexpression of PD-L1 and PD-1 on tumor cells and tumor-infiltrating lymphocytes, respectively, correlates with poor disease outcome in some human cancers. Monoclonal antibodies (mAbs) blockading the PD-1/PD-L1 pathway have been developed for cancer immunotherapy via enhancing T cell functions. Clinical trials with mAbs to PD-1 and PD-L1 have shown impressive response rates in patients, particularly for melanoma, non-small-cell lung cancer (NSCLC), renal cell carcinoma (RCC), and bladder cancer. Further studies are needed to dissect the mechanisms of variable response rate, to identify biomarkers for clinical response, to develop small-molecule inhibitors, and to combine these treatments with other therapies.

A single subset of dendritic cells controls the cytokine bias of natural killer T cell responses to diverse glycolipid antigens

Many hematopoietic cell types express CD1d and are capable of presenting glycolipid antigens to invariant natural killer T cells (iNKT cells). However, the question of which cells are the principal presenters of glycolipid antigens in vivo remains controversial, and it has been suggested that this might vary depending on the structure of a particular glycolipid antigen. Here we have shown that a single type of cell, the CD8α⁺ DEC-205⁺ dendritic cell, was mainly responsible for capturing and presenting a variety of different glycolipid antigens, including multiple forms of α-galactosylceramide that stimulate widely divergent cytokine responses. After glycolipid presentation, these dendritic cells rapidly altered their expression of various costimulatory and coinhibitory molecules in a manner that was dependent on the structure of the antigen. These findings show flexibility in the outcome of two-way communication between CD8α⁺ dendritic cells and iNKT cells, providing a mechanism for biasing toward either proinflammatory or anti-inflammatory responses.

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Complexes of antigenic glycolipids bound to CD1d have been visualized in situ

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A single DC subset predominates in presentation of a variety of glycolipids

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Antigen presentation to iNKT cells rapidly alters accessory molecules on APCs

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Reciprocal induction of CD70 and PD-L2 controls cytokine bias of iNKT cell responses

Inhibition through PD-1 is crucial for protection against M. tuberculosis infection (58.1)

With over one-third of the world's population currently infected with M. tuberculosis, there is an increasing need to develop novel vaccines and immunotherapies. Better understanding of the early immune responses in the lung is crucial for this purpose. We have shown that Programmed Death-1 (PD-1), a co-inhibitory receptor that is known to negatively regulate adaptive immune responses, is crucial for the development of a protective host response against M. tuberculosis. PD-1 deficient mice are extremely sensitive to tuberculosis, show uncontrolled bacterial proliferation in the lung and develop severe necrotic pneumonia, with dramatically reduced survival. Cytokine responses in the lungs of PD-1-/- and wild-type mice were profoundly different, indicating a significantly altered inflammatory response in the absence of PD-1. PD-1 blockade in wild-type mice after M. tuberculosis infection resulted in decreased survival, suggesting that immunotherapeutic approaches targeting PD-1 blockade should be considered cautiously. By studying genetically modified mouse models that have altered PD-1 or PD-L expression, our data show differential contributions of PD-L1 and PD-L2 to the immune regulatory role of PD-1 observed in tuberculosis. By providing the mechanism on the immune regulatory role of PD-1 in tuberculosis, our data will allow for the identification of novel therapeutic targets, which can be of great value for future immunotherapy.

Structural and functional studies on PD-1: from crystals to mice (63.17)

Programmed death-1 (PD-1) inhibits T and B cell responses upon binding to its ligands, PD-L1 and PD-L2, and has crucial role in maintaining peripheral tolerance. We have recently reported the crystal structure of the complex between PD-1 and PD-L2. Performing structure-based mutagenesis studies, high-affinity, and PD-L2-specific PD-1 mutants were identified. High-resolution crystal structures of the high-affinity PD-1 mutant with PD-L1 and PD-L2, respectively, provide the atomic details of the tighter receptor-ligand binding. The crystal structure of the complex between the PD-L2-specific PD-1 mutant and PD-L2 provides the atomic details of the selective interaction of this mutant with PD-L2. Soluble Ig fusion proteins of the two PD-1 mutants were designed to modulate the PD-1 pathway for immunotherapy. Finally, these mutations were introduced into mice by generating “knock-in” mouse strains, which provide novel animal models to study the role of PD-1 in immunity. Current work is focused on analyzing the functional effects of these mutations in PD-1 mediated immune responses. In summary, our data demonstrate the value of structural studies in developing novel immunotherapy and animal models for in vivo studies.

The role of Programmed Death-1 (PD-1) in pulmonary M. tuberculosis infection: friend or foe? (40.10)

The programmed death-1 (PD-1) co-inhibitory receptor attenuates T and B cell responses and plays a crucial role in peripheral tolerance. Recently, PD-1 has been shown to inhibit T cell responses during chronic viral infections such as LCMV and HIV, and blockade of PD-1 restored anti-viral effector T cell responses. In this study, we examined the role of PD-1 in infection with Mycobacterium tuberculosis, a common co-infection with HIV. Surprisingly and paradoxically, PD-1 deficient mice showed dramatically reduced survival compared to wild-type mice. Moreover, lungs of the PD-1-/- mice showed uncontrolled bacterial proliferation, and focal necrotic areas with predominantly neutrophilic infiltrates, but a lower number of infiltrating T and B cells. Pro-inflammatory cytokines, such as TNF-α, IL-1, and especially IL-6 were significantly increased in the lung and sera of infected PD-1-/- mice, consistent with an excessive inflammation. Microarray analysis of the lungs infected with M. tuberculosis showed dramatic differences between PD-1-/- and control mice: 297 genes were differentially expressed, resulting in profoundly altered inflammatory responses, with implications in both innate and adaptive immunity. Our studies demonstrate that M. tuberculosis infection in the absence of PD-1 results in fatal inflammation with increased bacterial load; therefore we suggest that the PD-1 pathway is involved in controlling inflammatory responses after M. tuberculosis infection in the lungs.

Sequence, structure, function, immunity: structural genomics of costimulation

SUMMARY

Costimulatory receptors and ligands trigger the signaling pathways that are responsible for modulating the strength, course, and duration of an immune response. High-resolution structures have provided invaluable mechanistic insights by defining the chemical and physical features underlying costimulatory receptor:ligand specificity, affinity, oligomeric state, and valency. Furthermore, these structures revealed general architectural features that are important for the integration of these interactions and their associated signaling pathways into overall cellular physiology. Recent technological advances in structural biology promise unprecedented opportunities for furthering our understanding of the structural features and mechanisms that govern costimulation. In this review, we highlight unique insights that have been revealed by structures of costimulatory molecules from the immunoglobulin and tumor necrosis factor superfamilies and describe a vision for future structural and mechanistic analysis of costimulation. This vision includes simple strategies for the selection of candidate molecules for structure determination and highlights the critical role of structure in the design of mutant costimulatory molecules for the generation of in vivo structure-function correlations in a mammalian model system. This integrated 'atoms-to-animals' paradigm provides a comprehensive approach for defining atomic and molecular mechanisms.

The interchain disulfide linkage is not a prerequisite but enhances CD28 costimulatory function

Oligomeric state makes important contributions to the signaling mechanisms of costimulatory molecules. In this study we address the biological relevance of the disulfide-linked dimeric structure of CD28. Fluorescence Resonance Energy Transfer (FRET) demonstrates that removal of the interdomain disulfide bond (C123) does not interfere with the formation of CD28 oligomers on the cell surface. Although the C123S mutant shows 40% lower binding affinity to the ligand B7-1, it is able to costimulate anti-CD3-induced IL-2 production but at a lower level (150%) compared to the wild-type (270%). Interestingly, binding to B7-2 was not affected. Thus, the covalently linked dimeric structure of CD28 represents an important mechanistic determinant for the optimal costimulatory activity in the immunological synapse.

The PD-1/PD-L costimulatory pathway plays a key role in Histoplasma capsulatum pathogenesis (B122)

The PD-1 costimulatory receptor negatively regulates T cell receptor signaling upon interacting with its ligands PDL1 and PDL2 expressed on antigen presenting cells (APCs) and has a key role in maintaining self-tolerance. In the present study we examined the role of PD-1 in Histoplasma capsulatum (Hc) infection. Hc is a human pathogenic dimorphic fungus that replicates within macrophages in vivo. To characterize immune responses in murine histoplasmosis, macrophages, as well as splenocytes were analyzed after intranasal infection with Hc. qRT-PCR and FACS analysis showed significant, IFN-γ-mediated up-regulation of PDL1 on both macrophages and splenocytes. The role of the PD-1 pathway in Hc pathogenesis is further demonstrated by the significant (100%) survival of PD-1 deficient mice infected with a lethal dose of Hc. Although initially inflammatory reactions developed in the lungs, the mice were disease free by day 10, as shown by histological analysis and cfu values. Also, when Hc infected C57BL/6 mice were treated with blocking anti-PD-1 monoclonal antibody, there was a significant increase in the survival of the animals (70%), whereas all untreated mice died. Our results show for the first time the importance of the PD-1/PDL pathway in anti-fungal immunity, and offer novel strategies for immunotherapy in clinical histoplasmosis.

Histamine deficiency induces tissue-specific down-regulation of histamine H2 receptor expression in histidine decarboxylase knockout mice

Histidine decarboxylase (HDC) is the single enzyme responsible for histamine synthesis. HDC-deficient mice (HDC(-/-)) have no histamine in their tissues when kept on a histamine-free diet. Therefore, the HDC(-/-) mice provide a suitable model to investigate the involvement of histamine in the regulation of histamine receptor expression. Gene expression of H1 and H2 histamine receptors was studied in several organs of HDC(-/-) mice and compared to standard (HDC(+/+)) mice. In many tissues, prolonged absence of histamine induced down-regulation of the H2 receptor subtype. The expression of the H1 receptor was less sensitive to histamine deficiency. Exogenous histamine present in the diet abolished the differences observed in H2 receptor expression. These results suggest that the expression of mouse H2 receptor is under the control of histamine in a tissue-specific manner.