Imaging Immune Response with sdAbs

The interplay between stromal cells, tumor cells, and migratory cells such as lymphocytes creates opportunities for noninvasive imaging of immune responses. Experienced in single domain antibody (sdAb) development and antibody site-specific conjugation, Creative Biolabs offers various labeling approaches to develop sdAb-based imaging tracers. In vivo imaging services will be tailored according to your specific project demands. By using a combination of sdAb, we will choose the best one to track immune responses with excellent specificity.

Significance of Imaging Immune Response

Tumors are often surrounded and invaded by bone marrow-derived cells. Imaging the infiltration of such immune cells into tumors provides an attractive means of detecting tumors or of tracking the response to anticancer therapy. Reports show that it is possible to detect these cells non-invasively by various techniques such as positron emission tomography (PET) via the surface markers displayed by them. The ability to monitor the immune response in the course of therapy will enable early determination of the efficacy of treatment and will inform decisions as to whether treatment should be stopped or continued. Noninvasive monitoring could thus change how therapies are applied and assessed.

Imaging Examples

Radiolabeled anti-murine class II major histocompatibility complex (MHC II) and CD11b sdAbs were developed to assess immune infiltrates in different tumor models. The radiolabeled anti-class II MHC and anti-CD11b sdAbs were then used to detect tumors in both xenogeneic and syngeneic tumor models. Similarly, to image human immune responses, an anti-human MHC IIb sdAb was developed and the radiolabeled sdAb was used in a relevant humanized mouse model to detected graft-versus-host disease. In diseased animals, a significant increase in PET signal in the liver was detected, which was attributed to the infiltration of activated class II MHC⁺ T cells. The method may thus be more generally useful to diagnose inflammation.

Cytotoxic CD8⁺ T cells mediate much of the response to checkpoint blockade. Monitoring the distribution of CD8⁺ T cells could be used to assess the response to therapy. A ⁸⁹Zr-labeled anti-CD8 sdAb was used to perform PET on mice. PET images showed label accumulation in lymphoid organs, as well as in the kidneys and bladder. The addition of a PEG molecule was found to improve the efficiency of staining and decrease non-specific uptake in the kidneys.

Common Tools

Customized Services

• Generation and in vitro characterization of sdAb
• Tailored PEG modification for lead sdAb
• Nanotracers construction services
• In vitro assessment services
• In vivo imaging services
• Statistical analysis

With the availability of anti-human sdAb, the ability to monitor the presence or absence of neutrophils and activated macrophages as an indicator of inflammation should be transposable to a pre-clinical or clinical setting as a diagnostic tool. Creative Biolabs customized imaging sdAb-based tracer development services for global clients. If you are interested in our services, please feel free to contact us for more information.

Published Data

1. Nanobody-Based Immuno-PET for Noninvasive Imaging of CD8⁺ T Cell Responses

Fig.1 Quantification of CD8⁺ T Cell Immuno-PET Signal in the Lungs and MLN/Thymus.^1,3

In this study, researchers used a sdAb targeting mouse CD8α, labeled with ⁸⁹Zr, to image CD8⁺ T cells during influenza A virus (IAV) infection. CD8⁺ signals increased significantly in the mediastinal lymph node (MLN) and thymus at 4 days post-infection (dpi), with the lungs showing a similar increase at 6 dpi. Initially, CD8⁺ T cells were diffusely distributed in the lungs, later accumulating in specific regions, correlating with peak morbidity and weight loss. CD8⁺ T cells isolated from control or IAV-infected mice displayed differences in their distribution and migration patterns when labeled ex vivo with ⁸⁹Zr-labeled anti-CD8α sdAb and subsequently transferred into infected or control animals. Infected mice’s CD8⁺ T cells persisted in the lungs, even in uninfected mice. Immuno-PET imaging enabled noninvasive, real-time tracking of the immune response to infection in live animals.

2. In Vivo Imaging of Human CD4⁺ Cells Using Single-Domain Antibodies

Fig.2 CD4-Nbs for in vivo imaging.^2,3

This study developed novel sdAbs that specifically target human CD4. Following an assessment of their binding characteristics, recognized epitopes, and impact on T-cell functions, the researchers identified CD4-specific Nbs that did not affect T-cell proliferation, activation, or cytokine secretion in vitro. These Nbs were then transformed into immune tracers for noninvasive molecular imaging. Using optical imaging, they demonstrated that a high-affinity CD4-Nb could visualize CD4⁺ cells in vivo in a xenograft model. In a human CD4 knock-in mouse model, ⁶⁴Cu-labeled CD4-Nb1 was demonstrated to rapidly accumulate in CD4⁺ T cell-rich tissues through immunoPET/MR imaging. These CD4-Nbs may serve as probes for patient stratification and monitoring immune responses in cancer and inflammatory diseases.

References

1. Rothlauf, Paul W., et al. "Noninvasive immuno-PET imaging of CD8⁺ T cell behavior in influenza A virus-infected mice." Frontiers in Immunology 12 (2021): 777739.
2. Traenkle, Bjoern, et al. "Single-domain antibodies for targeting, detection, and in vivo imaging of human CD4⁺ cells." Frontiers in immunology 12 (2021): 799910.
3. Distributed under Open Access license CC BY 4.0, without modification.

For Research Use Only.