Therapeutic antitumor antibodies treat cancer by mobilizing both innate and adaptive immunity. CD47 is an antiphagocytic ligand exploited by tumor cells to blunt antibody effector functions by ...transmitting an inhibitory signal through its receptor signal regulatory protein alpha (SIRPα). Interference with the CD47–SIRPα interaction synergizes with tumor-specific monoclonal antibodies to eliminate human tumor xenografts by enhancing macrophage-mediated antibody-dependent cellular phagocytosis (ADCP), but synergy between CD47 blockade and ADCP has yet to be demonstrated in immunocompetent hosts. Here, we show that CD47 blockade alone or in combination with a tumor-specific antibody fails to generate antitumor immunity against syngeneic B16F10 tumors in mice. Durable tumor immunity required programmed death-ligand 1 (PD-L1) blockade in combination with an antitumor antibody, with incorporation of CD47 antagonism substantially improving response rates. Our results highlight an underappreciated contribution of the adaptive immune system to anti-CD47 adjuvant therapy and suggest that targeting both innate and adaptive immune checkpoints can potentiate the vaccinal effect of antitumor antibody therapy.
Toll-like receptor (TLR) signaling plays a critical role in innate and adaptive immune responses and must be tightly controlled. TLR4 uses LPS binding protein, MD-2, and CD14 as accessories to ...respond to LPS. We therefore investigated the presence of an analagous soluble cofactor that might assist in the recruitment of CpG oligonucleotides (CpG-ODNs) to TLR9. We report the identification of granulin as an essential secreted cofactor that potentiates TLR9-driven responses to CpG-ODNs. Granulin, an unusual cysteine-rich protein, bound to CpG-ODNs and interacted with TLR9. Macrophages from granulin-deficient mice showed not only impaired delivery of CpG-ODNs to endolysosomal compartments, but also decreased interaction of TLR9 with CpG-ODNs. As a consequence, granulin-deficient macrophages showed reduced responses to stimulation with CpG-ODNs, a trait corrected by provision of exogenous granulin. Thus, we propose that granulin contributes to innate immunity as a critical soluble cofactor for TLR9 signaling.
► Granulin binds TLR9 and CpG oligonucleotides ► Granulin is sufficient for intracellular localization of CpG-ODNs ► Granulin is a critical cofactor in enabling TLR9 signal transduction
Sortases are a class of bacterial enzymes that possess transpeptidase activity. It is their ability to site‐specifically break a peptide bond and then reform a new bond with an incoming nucleophile ...that makes sortase an attractive tool for protein engineering. This technique has been adopted for a range of applications, from chemistry‐based to cell biology and technology. In this Minireview we provide a brief overview of the biology of sortase enzymes and current applications in protein engineering. We identify areas that lend themselves to further innovation and that suggest new applications.
It takes all sortases: Enzymatic formation of a peptide bond using the sortase A transpeptidase (SrtA) provides a convenient and mild means for engineering proteins to contain nongenetically templated modifications. Myriad applications are possible, from producing homogeneous post‐translational modification mimics, assembling protein domains, to anchoring proteins to solid surfaces.
Ubiquitin is important for nearly every aspect of cellular physiology. All viruses rely extensively on host machinery for replication; therefore, it is not surprising that viruses connect to the ...ubiquitin pathway at many levels. Viral involvement with ubiquitin occurs either adventitiously because of the unavoidable usurpation of cellular processes, or for some specific purpose selected for by the virus to enhance viral replication. Here, we review current knowledge of how the ubiquitin pathway alters viral replication and how viruses influence the ubiquitin pathway to enhance their own replication.
The principal components of both MHC class I and class II antigen processing and presentation pathways are well known. In dendritic cells, these pathways are tightly regulated by Toll-like-receptor ...signalling and include features, such as cross-presentation, that are not seen in other cell types. However, the exact mechanisms involved in the subcellular trafficking of antigens remain poorly understood and in some cases are controversial. Recent data suggest that diverse cellular machineries, including autophagy, participate in antigen processing and presentation, although their relative contributions remain to be fully elucidated. Here, we highlight some emerging themes of antigen processing and presentation that we think merit further attention.
The endoplasmic reticulum (ER) is the site of maturation for secretory and membrane proteins that together make up about one third of the cellular proteome. Cells carefully control the synthetic ...output of this organelle to regulate both quality and quantity of proteins that emerge. Here, we synthesize current concepts underlying the pathways that mediate protein degradation from the ER and their deployment under physiologic and pathologic conditions.
Noninvasive imaging of immune responses Rashidian, Mohammad; Keliher, Edmund J.; Bilate, Angelina M. ...
Proceedings of the National Academy of Sciences - PNAS,
05/2015, Letnik:
112, Številka:
19
Journal Article
Recenzirano
Odprti dostop
Significance Tumors are often surrounded and invaded by bone marrow-derived cells. Imaging the infiltration of such immune cells into tumors may therefore be an attractive means of detecting tumors ...or of tracking the response to anticancer therapy. We show that it is possible to detect these cells noninvasively by 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 therefore change how therapies are applied and assessed, to the benefit of many patients.
At their margins, tumors often contain neutrophils, dendritic cells, and activated macrophages, which express class II MHC and CD11b products. The interplay between stromal cells, tumor cells, and migratory cells such as lymphocytes creates opportunities for noninvasive imaging of immune responses. We developed alpaca-derived antibody fragments specific for mouse class II MHC and CD11b products, expressed on the surface of a variety of myeloid cells. We validated these reagents by flow cytometry and two-photon microscopy to obtain images at cellular resolution. To enable noninvasive imaging of the targeted cell populations, we developed a method to site-specifically label VHHs the variable domain (V H) of a camelid heavy-chain only antibody with ¹⁸F or ⁶⁴Cu. Radiolabeled VHHs rapidly cleared the circulation ( t ₁/₂ ≈ 20 min) and clearly visualized lymphoid organs. We used VHHs to explore the possibility of imaging inflammation in both xenogeneic and syngeneic tumor models, which resulted in detection of tumors with remarkable specificity. We also imaged the infiltration of myeloid cells upon injection of complete Freund’s adjuvant. Both anti-class II MHC and anti-CD11b VHHs detected inflammation with excellent specificity. Given the ease of manufacture and labeling of VHHs, we believe that this method could transform the manner in which antitumor responses and/or infectious events may be tracked.
The Zika virus (ZIKV) outbreak in the Americas and South Pacific poses a significant burden on human health because of ZIKV's neurotropic effects in the course of fetal development. Vaccine ...candidates against ZIKV are coming online, but immunological tools to study anti-ZIKV responses in preclinical models, particularly T cell responses, remain sparse. We deployed RNA nanoparticle technology to create a vaccine candidate that elicited ZIKV E protein-specific IgG responses in C57BL/6 mice as assayed by ELISA. Using this tool, we identified a unique H-2D
-restricted epitope to which there was a CD8
T cell response in mice immunized with our modified dendrimer-based RNA nanoparticle vaccine. These results demonstrate that this approach can be used to evaluate new candidate antigens and identify immune correlates without the use of live virus.
Chemokines are small proteins that function as immune modulators through activation of chemokine G protein–coupled receptors (GPCRs). Several viruses also encode chemokines and chemokine receptors to ...subvert the host immune response. How protein ligands activate GPCRs remains unknown. We report the crystal structure at 2.9 angstrom resolution of the human cytomegalovirus GPCR US28 in complex with the chemokine domain of human CX3CL1 (fractalkine). The globular body of CX3CL1 is perched on top of the US28 extracellular vestibule, whereas its amino terminus projects into the central core of US28. The transmembrane helices of US28 adopt an active-state–like conformation. Atomic-level simulations suggest that the agonist-independent activity of US28 may be due to an amino acid network evolved in the viral GPCR to destabilize the receptor's inactive state.
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