| As a core member of adaptive immune system,cellular immunity is dominated by T lymphocytes and is extensively involved in many physiological and pathological processes.On the one hand,cellular immunity constitutes a reliable line of defense that facilitates the elimination of malignancy and intracellular pathogen.Up-regulation of cellular immunity is thereby the primary objective of many antitumor,antiviral and antibacterial vaccines.On the other hand,hyper-activation or overreaction of cellular immunity is the main etiological factor of allograft rejection,type IV hypersensitivity,autoimmune diseases and inflammatory diseases.In these cases,down-regulation of cellular immunity is regarded as the ultimate purpose of treatment.However,at present,the regulation of cellular immunity is largely limited by insufficient means and efficiency,which is further challenged by a lack of in-depth understanding of the immunological network.As a result,new target of manipulation and better interpretation of cellular immunity are urgently needed for the prophylaxis and treatment of associated diseases.The inherent characteristics of antigen and the type of delivery vector are important determinants of cellular immune response,which are therefore first investigated for their potential applications in manipulating cellular immunity in this work.To begin with,cationic nanoemulsion(CNE)capable of complexing multi-epitope tumor antigen in the form of protein or m RNA was constructed,and antitumor cellular immunity with the same delivery vector but different forms of antigen was studied.Comparative analysis revealed that the phenotypic maturation and antigen presentation of dendritic cells(DCs)pulsed with these two forms of antigen were different.Specifically,protein-based antigen elicited major histocompatibility complex(MHC)class II-biased presentation and favored the establishment of humoral immunity;whereas m RNA-based antigen induced MHC class I-biased presentation and CD8~+T cell-preferred immunity.Then,m RNA encoding the receptor binding domain of severe acute respiratory syndrome coronavirus 2(SARS-Co V-2)spike protein was formulated with different nanoparticles including CNE,cationic liposome(Lipo)and Lipid nanoparticle(LNP),and antiviral cellular immunity with the same antigen form but different types of delivery vector was explored.By comparison,LNP-based m RNA vaccine elicited humoral-preferred immune responses,while CNE-and Lipo-based ones gave rise to cellular-skewed immunity.The above results indicated that the immunological outcomes were largely determined by the type of modulatory molecule,and were tunable by the use of delivery vehicle.Thus,an appropriate selection and optimization of the drug delivery system(DDS)might facilitate the regulation of cellular immunity.Of note,composed of multiple members and involved in various biological activities,cellular immunity is subjected to a sophisticated regulatory network that requires precise drug delivery.Off-target drug distribution not only limits the therapeutic effectiveness,but poses a potential risk of inducing toxicity.In these regards,targeted drug delivery to its site of pharmacological action is urgently needed in the context of cellular immunity regulation.Compared with tissue targeting and cell targeting,subcellular structure targeting is more refined.In recent years,the advances in molecular cell biology have enhanced our understanding of the structure and function of subcellular compartments,while the development of pharmaceutics and nanotechnology have enabled targeted delivery and controlled release of drugs.Eukaryotic endoplasmic reticulum(ER)participates in and supports multiple biological activities of various immune cells,profoundly affects the type,magnitude,persistence and consequence of cellular immune response.Therefore,ER is recognized as a key target of cellular immune regulation,and drugs routed to the ER of different immune cells and/or interfere with different signalling pathways via targeted DDS may lead to efficient manipulation of the cellular immunity to satisfy different therapeutic demands.In these considerations,in the second and third parts of this work,two ER targeted DDSs respectively capable of up-regulating and down-regulating cellular immunity were constructed,with their therapeutic applications and modes of action explored:(1)ER-targeted antigen delivery up-regulated cellular immunity for improved antitumor vaccine effect.The cross presentation of exogenous antigen protein by DCs contributes to the activation of naive CD8~+T cells and promotes the initiation of cellular immune response,serving as an important means to optimize the anti-infection/antitumor effect of protein-based vaccines.ER-associated degradation(ERAD)machinery and multiple ER chaperones participate in the cross presentation of DCs.Therefore,improving the accessibility of exogenous antigen to the ER of DCs might facilitate the development of cross presentation and promote antigen-specific cellular immunity.On these basis,cationic liposome loaded with tumor model antigen chicken ovalbumin(OVA)and surface-modified with ER targetable polypeptide Pardaxin was constructed,i.e.,OVA@lipo T.The cationic nature of the liposome facilitated the encapsulation and cellular internalization of antigen,whereas the introduction of Pardaxin modification enabled an ER-targeted intracellular trafficking and accumulation of antigen.Subsequently,ER-located antigen underwent endogenous processing with the help of ERAD,leading to elevated cross presentation.Both in vitro and in vivo results demonstrated that such an ER-targeted antigen delivery strategy exhibited overwhelming superiority in mobilizing antigen epitope-specific CD8~+T cell response,which significantly improved the antitumor vaccine effect.(2)ER-targeted small molecule drug delivery down-regulated cellular immunity for alleviated skin allograft rejection.Transplantation is the only survival option for patients with end-stage organ failure.Due to unmet clinical need for syngeneic organ grafts,allogeneic transplantation has been most frequently adopted.However,allogeneic grafts are vulnerable to the attack launched by the host immune system,especially the cellular immunity,which is primarily responsible for allograft rejection and even failure in the clinic.Increasing evidence suggests that cellular immunity-mediated allogenic graft rejection is usually accompanied by a hyperactivation of host lymphocyte ER stress response,i.e.,unfolded protein response(UPR),that is initiated by ER-resident transmembrane proteins.Therefore,ER-targeted intervention of lymphocytic UPR may effectively inhibit cellular immunity and mitigate allograft rejection.Accordingly,Pardaxin-modified ER-targetable liposome encapsulating small molecule inhibitor of UPR pathway(UPRi)was prepared,i.e.,UPRi@lipo T.Results demonstrated that UPRi@lipo T was internalized by lymphocytes and accumulated in the ER,contributing to an efficient inhibition of UPR;UPR participated in the activation-induced phase transition processes of CD8~+T cells and thereby influenced their clonal expansion,effector function and memory commitment;ER-targeted abrogation of lymphocytic ER-stress transducer IRE1αby UPRi@lipo T induced systemic cellular immune suppression,attenuated transplant rejection and prolonged graft survival in a murine full-thickness trunk skin allograft model,which can be further used in combination with immunosuppressant FK506 for synergistic inhibition effect on the cellular immunity.In conclusion,this work revealed the great potential of ER-targeted delivery system in reshaping the cellular immunity,which may satisfy multiple therapeutic demands by acting on different target cells and introducing different modes of intervention that lead to up-regulation or down-regulation of cellular immunity. |
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