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Anti-HER2 nanobody

Expression and purification of anti-Her2 nanobody for the anchoring to the liposome.

Sequence and Features

Introduction

Toulouse-INSA-UPS 2023 designed this part to decorate the liposome for anchoring to cancer cells. To express and purify these Anti-HER2 Nanobodies (Anti-HER2 nb), we used the E. coli strain BL21(DE3), which contained the plasmid pET26b_pelB-HER2-tev-stops, provided to us by Adilya Dagkesamanskaya, a researcher at the Toulouse Biotechnology Institute (TBI). This plasmid contained the gene for the Anti-HER2 Nanobody fused to a signal peptide gene called pelB leader, along with a Histag for purification. The signal peptide was fused to the Anti-HER2 nb with the aim of achieving periplasmic expression.

Construction expression and purification

The expression of this Anti-HER2 nb part was induced using IPTG, and purification was carried out using Cobalt resin (TALON® Metal Affinity Resin).

Two separate batches of protein expression and purification were performed in duplicate, and both were successful.

The expected size of Anti-HER2 nb is approximately 17 kDa. In figure 2, we can observe a clear band around this size in the extract and flowthrough, demonstrating expression of the nanobody Anti-HER2. The presence of a similar band in the negative control (No IPTG, lane 2, gel 2 in Figure 1) probably reflects an uncontrolled expression of the nanobody due to promoter leakage. Approximately 2 mL of the nanobody at 17.65 µM was produced for each sample.

Characterisation

Anchoring of liposomes decorated with Anti-HER2 nb on Caco-2 cells

To test how liposomes anchor to cancer cells using Anti-HER2 Nanobodies, we prepared standardized fluorescent liposomes with a diameter of 400 nm. These liposomes contain DGS lipids, which allow us to coat the liposomes with the Anti-HER2 Nanobodies. see Protocol page.We used HER2-positive colorectal adenocarcinoma cells called Caco-2 cells to test how well the liposomes could attach with the help of the Anti-HER2 Nanobodies see Protocol page.Figure 3 shows a microscopy image of adherent and non-adherent Caco-2 cells observed in brightfield. For education purposes we appended on the image some features of living eukaryotic cells that can be distinguished with a standard optical microscope.

Fluorescent liposomes were incubated on top of Caco-2 cells as described in our Protocol page. Figure 4 shows an animated gif picture with the trajectory of liposomes over time. It is possible to differentiate between diffusing liposomes and anchored liposomes on cancerous cells.

Figure 4: Optical imaging of Caco-2 cells (brightfield) and 400-nm fluorescent liposomes (red fluorescence) functionalized with Anti-HER2 nb after 1 hour incubation. This gif animation taken from a movie allows for categorizing liposomes as diffusing or immobile (anchored) during the lifespan of the movie.

Qualitatively, this experiment seems to show that liposomes are able to anchor on cancerous cells. However, it does not allow us to ascertain the specificity of the interaction between the liposome and the cancerous cell. Control liposome samples without anti-HER2 nanobodies or competitive assays with soluble extracellular domain of HER2 added in solution will have to be performed.

Conclusion and Perspectives

These experiments provide evidence that the Anti-HER2 nb production was successful and that it seems possible to use it to promote liposome anchoring on cancerous cells. However, we would recommend performing more experiments to better characterize the anti-HER2 nanobodies and its interaction with HER2 on cancer cells.

The construction , the expression and the purification of this Nanobody Anti-HER2 part can be performed in the Biosafety level-1 laboratory and the characterization with cancer cells in the Biosafety level-2 laboratory.

References

1. ^[1]Chabrol E, Stojko J, Nicolas A, et al. VHH characterization.Recombinant VHHs: Production, characterization and affinity. Anal Biochem. 2020;589:113491. https://doi:10.1016/j.ab.2019.113491.
2. ^[2]Hartmann L, Botzanowski T, Galibert M, et al. VHH characterization. Comparison of recombinant with chemically synthesized anti-HER2 VHH. Protein Sci. 2019;28(10):1865-1879. https://doi:10.1002/pro.3712.
3. ^[3]Chabrol E, Fagnen C, Landron S, et al. Biochemistry, structure, and cellular internalization of a four nanobody-bearing Fc dimer. Protein Sci. 2021;30(9):1946-1957. https://doi:10.1002/pro.4147.