Highlights d Mutations in TCRb and CD3z TMRs that reduce their interaction augment signaling d pMHC and anti-CD3 binding to TCR-CD3 induce similar quaternary structure relaxation d Soluble monovalent pMHC alone signals and reduces TCRab cohesion with CD3z d Allosteric changes in TCR-CD3 dynamics instigate T cell activation

We have exploited the properties of filamentous bacteriophage fd to deliver immunologically active lipids together with antigenic peptides. Filamentous bacteriophages resemble for size, capability to be permeable to blood vessels, and high density antigen expression, a nature-made nanoparticle. In addition, their major coat protein pVIII, which is arranged to form a tubular shield surrounding the phage genome, has a high content of hydrophobic residues promoting lipid association. We conjugated bacteriophages to alpha-GalactosylCeramide (α-GalCer), a lipid antigen-stimulating invariant natural killer T (iNKT) cells and capable of inducing their anti-tumoral activities. We found that bacteriophage fd/α-GalCer conjugates could repeatedly stimulate iNKT cells in vitro and in vivo, without inducing iNKT anergy. Moreover, co-delivery of α-GalCer and a MHC class I restricted tumor-associated antigenic determinant to antigen-presenting cells via bacteriophages strongly boosted adaptive CD8+ T cell response and efficiently delayed tumor progression. Co-delivery of a tumor antigen and iNKT-stimulatory lipid on the surface of filamentous bacteriophages is a novel approach to potentiate adaptive anti-cancer immune responses, overcoming the current limitations in the use of free α-GalCer and may represent an attractive alternative to existing delivery methods, opening the path to a potential translational usage of this safe, inexpensive, and versatile tool.

In the originally published version of this article, p-MHC was incorrectly defined due to copyeditor oversight. The correct definition for p-MHC is ''peptide-major histocompatibility complex,'' and this has been corrected in the paper online.The production team apologizes for the error.

No abstract

The mechanism of T cell antigen receptor (TCR-CD3) signalling remains elusive. Here, we identified mutations in the transmembrane region of TCRβ or CD3ζ that augmented pMHC-induced signalling, not explicable by enhanced ligand binding, lateral diffusion, clustering or co-receptor function. Using a novel biochemical assay and molecular dynamics simulation, we demonstrated that the gain-of-function mutations loosened interaction between TCRαβ and CD3ζ. We found that, similar to the activating mutations, pMHC binding reduced TCRαβ cohesion with CD3ζ. This event occurred prior to CD3ζ phosphorylation and at 0°C. Moreover, we demonstrated that soluble monovalent pMHC alone induced signalling and reduced TCRαβ cohesion with CD3ζ in membrane-bound or solubilised TCR-CD3. Our data provide compelling evidence that pMHC binding suffices to activate allosteric changes propagating from TCRαβ to the CD3 subunits, reconfiguring interchain transmembrane region interactions. These dynamic modifications could change the arrangement of TCR-CD3 boundary lipids to licence CD3ζ phosphorylation and initiate signal propagation.