Surface biotinylation of cytotoxic T lymphocytes for in vivo tracking of tumor immunotherapy in murine models.

Currently, there is no stable and flexible method to label and track cytotoxic T lymphocytes (CTLs) in vivo in CTL immunotherapy. We aimed to evaluate whether the sulfo-hydroxysuccinimide (NHS)-biotin-streptavidin (SA) platform could chemically modify the cell surface of CTLs for in vivo tracking. CD8+ T lymphocytes were labeled with sulfo-NHS-biotin under different conditions and then incubated with SA-Alexa647. Labeling efficiency was proportional to sulfo-NHS-biotin concentration. CD8+ T lymphocytes could be labeled with higher efficiency with sulfo-NHS-biotin in DPBS than in RPMI (P < 0.05). Incubation temperature was not a key factor. CTLs maintained sufficient labeling for at least 72 h (P < 0.05), without altering cell viability. After co-culturing labeled CTLs with mouse glioma stem cells (GSCs) engineered to present biotin on their surface, targeting CTLs could specifically target biotin-presenting GSCs and inhibited cell proliferation (P < 0.01) and tumor spheres formation. In a biotin-presenting GSC brain tumor model, targeting CTLs could be detected in biotin-presenting gliomas in mouse brains but not in the non-tumor-bearing contralateral hemispheres (P < 0.05). In vivo fluorescent molecular tomography imaging in a subcutaneous U87 mouse model confirmed that targeting CTLs homed in on the biotin-presenting U87 tumors but not the control U87 tumors. PET imaging with 89Zr-deferoxamine-biotin and SA showed a rapid clearance of the PET signal over 24 h in the control tumor, while only minimally decreased in the targeted tumor. Thus, sulfo-NHS-biotin-SA labeling is an efficient method to noninvasively track the migration of adoptive transferred CTLs and does not alter CTL viability or interfere with CTL-mediated cytotoxic activity.

Imaging Tumor Vascularity and Response to Anti-Angiogenic Therapy Using Gaussia Luciferase.

We developed a novel approach to assess tumor vascularity using recombinant Gaussia luciferase (rGluc) protein and bioluminescence imaging. Upon intravenous injection of rGluc followed by its substrate coelenterazine, non-invasive visualization of tumor vascularity by bioluminescence imaging was possible. We applied this method for longitudinal monitoring of tumor vascularity in response to the anti-angiogenic drug tivozanib. This simple and sensitive method could be extended to image blood vessels/vasculature in many different fields.

Simultaneous in vivo monitoring of regulatory and effector T lymphocytes using secreted Gaussia luciferase, Firefly luciferase, and secreted alkaline phosphatase.

Regulatory T cells (Tregs) are amongst the most widely studied cells in a variety of immune-mediated conditions, including transplantation and Graft Versus Host Disease (GVHD), cancer and autoimmunity; indeed, there is great interest in the tolerogenic potential of Treg-based therapy. Consequently, the need to establish the mechanisms that determine Treg survival and longevity, in addition to developing new tools to monitor these parameters, is paramount. Using both a mouse model of GVHD and a mouse model of Type 1 Diabetes (T1D), we describe herein a dual reporter system based on Gluc and multiplexed with SEAP and non-secreted Firefly luciferase (Fluc), which permits simultaneous imaging and noninvasive tracking of two different T-cell populations (CD4(+)CD25(+) Tregs and CD4(+)CD25(-) Tcon cells) in vivo by transducing the cells with different lentiviruses bearing distinct color signatures. This new technology promises to overcome the limitations of the conventional methods currently available to study lymphocyte survival in vivo. Furthermore, this novel technique has applications not only in autoimmunity and alloimmunity, but also in the wider field of immunology.

Directed molecular evolution reveals Gaussia luciferase variants with enhanced light output stability.

Gaussia Luciferase (Gluc) has proven to be a powerful mammalian cell reporter for monitoring numerous biological processes in immunology, virology, oncology, and neuroscience. Current limitations of Gluc as a reporter include its emission of blue light, which is absorbed by mammalian tissues, limiting its use in vivo, and a flash-type bioluminescence reaction, making it unsuited for high-throughput applications. To overcome these limitations, a library of Gluc variants was generated using directed molecular evolution and screened for relative light output, a shift in emission spectrum, and glow-type light emission kinetics. Several variants with a 10-15 nm shift in their light emission peak were found. Further, a Gluc variant that catalyzes a glow-type bioluminescence reaction, suited for high-throughput applications, was also identified. These results indicate that molecular evolution could be used to modulate Gluc bioluminescence reaction characteristics.