Lymphoid organs, in which antigen presenting cells (APCs) are in close proximity to T cells, are the ideal microenvironment for efficient priming and amplification of T-cell responses. However, the systemic delivery of vaccine antigens into dendritic cells (DCs) is hampered by various technical challenges. Here we show that DCs can be targeted precisely and effectively in vivo using intravenously administered RNA-lipoplexes (RNA-LPX) based on well-known lipid carriers by optimally adjusting net charge, without the need for functionalization of particles with molecular ligands. The LPX protects RNA from extracellular ribonucleases and mediates its efficient uptake and expression of the encoded antigen by DC populations and macrophages in various lymphoid compartments. RNA-LPX triggers interferon-α (IFNα) release by plasmacytoid DCs and macrophages. Consequently, DC maturation in situ and inflammatory immune mechanisms reminiscent of those in the early systemic phase of viral infection are activated. We show that RNA-LPX encoding viral or mutant neo-antigens or endogenous self-antigens induce strong effector and memory T-cell responses, and mediate potent IFNα-dependent rejection of progressive tumours. A phase I dose-escalation trial testing RNA-LPX that encode shared tumour antigens is ongoing. In the first three melanoma patients treated at a low-dose level, IFNα and strong antigen-specific T-cell responses were induced, supporting the identified mode of action and potency. As any polypeptide-based antigen can be encoded as RNA, RNA-LPX represent a universally applicable vaccine class for systemic DC targeting and synchronized induction of both highly potent adaptive as well as type-I-IFN-mediated innate immune mechanisms for cancer immunotherapy.

Multiple genetic events and subsequent clonal evolution drive carcinogenesis, making disease elimination with single-targeted drugs difficult. The multiplicity of gene mutations derived from clonal heterogeneity therefore represents an ideal setting for multiepitope tumor vaccination. Here, we used next generation sequencing exome resequencing to identify 962 nonsynonymous somatic point mutations in B16F10 murine melanoma cells, with 563 of those mutations in expressed genes. Potential driver mutations occurred in classical tumor suppressor genes and genes involved in proto-oncogenic signaling pathways that control cell proliferation, adhesion, migration, and apoptosis. Aim1 and Trrap mutations known to be altered in human melanoma were included among those found. The immunogenicity and specificity of 50 validated mutations was determined by immunizing mice with long peptides encoding the mutated epitopes. One-third of these peptides were found to be immunogenic, with 60% in this group eliciting immune responses directed preferentially against the mutated sequence as compared with the wild-type sequence. In tumor transplant models, peptide immunization conferred in vivo tumor control in protective and therapeutic settings, thereby qualifying mutated epitopes that include single amino acid substitutions as effective vaccines. Together, our findings provide a comprehensive picture of the mutanome of B16F10 melanoma which is used widely in immunotherapy studies. In addition, they offer insight into the extent of the immunogenicity of nonsynonymous base substitution mutations. Lastly, they argue that the use of deep sequencing to systematically analyze immunogenicity mutations may pave the way for individualized immunotherapy of cancer patients. Cancer Res; 72(5);

Adoptive transfer of dendritic cells (DCs) transfected with in vitro-transcribed, RNA-encoding, tumor-associated antigens has recently entered clinical testing as a promising approach for cancer immunotherapy. However, pharmacokinetic exploration of RNA as a potential drug compound and a key aspect of clinical development is still pending. While investigating the impact of different structural modifications of RNA molecules on the kinetics of the encoded protein in DCs, we identified components located 3 of the coding region that contributed to a higher transcript stability and translational efficiency. With the use of quantitative reverse transcription-polymerase chain reaction (RT-PCR) and eGFP variants to measure transcript amounts and protein yield, we showed that a poly(A) tail measuring 120 nucleotides compared with a shorter one, an unmasked poly(A) tail with a free 3 end rather than one extended with unrelated nucleotides, and 2 sequential ␤-globin 3 untranslated regions cloned head to tail between the coding region and the poly(A) tail each independently enhanced RNA stability and translational efficiency. Consecutively, the density of antigen-specific peptide/MHC complexes on the transfected cells and their potency to stimulate and expand antigen-specific CD4 ؉ and CD8 ؉ T cells were also increased. In summary, our data provide a strategy for optimizing RNA-transfected DC vaccines and a basis for defining release criteria for such vaccine preparations. IntroductionAntigen-encoding RNA 1,2 has the advantages of a genetic vaccine (delivery of all epitopes of the whole antigen, easy manufacturing, standardized purification) and the added value of a safe pharmaceutical characterized by transient expression and lack of integration into the genome of the treated host. The combination of this versatile antigen delivery molecule with dendritic cells (DCs) as the most potent antigen-presenting cells is regarded as an attractive approach to induce cellular and potentially therapeutic immune responses in patients with cancer. Reports demonstrated convincingly that the use of RNA results in efficient induction of antigen-specific immune responses in vitro and in animal models 1,[3][4][5][6][7] and paved the way for trials in humans. Early clinical trials showed feasibility, lack of toxicity, and promising efficacy based on immunologic and clinical read-outs. [8][9][10][11][12] At this early phase of clinical development, antigen-specific RNA has the status of a drug compound requiring detailed exploration.Basic pharmacologic issues that must be addressed in drug development include the pharmacokinetics of the compound of interest within the system of its physiological activity after administration. In the quoted clinical trials, this system would be represented by immature or mature DCs. A key objective of such investigations is better understanding of the impact of the structural features of the drug formulation on its pharmacologic properties. Neither of these questions has thus far been addressed for antigen-e...

Although naked antigen-encoding RNA has entered clinical testing, basic knowledge on how to apply this promising novel vaccine format is still pending. By comparing different administration routes, we observed surprisingly potent antigen-specific T-cell immunity upon intranodal injection of naked antigen-encoding RNA. RNA was selectively uptaken by resident dendritic cells, propagated a T-cell attracting and stimulatory intralymphatic milieu, and led to efficient expansion of antigen-specific CD8 + as well as CD4 + T cells. By intranodal treatment of mice with repeated cycles of RNA, we achieved de novo priming of naïve T cells, which became potent cytolytic effectors capable of homing to primary and secondary lymphatic tissues as well as memory T cells. In tumor-bearing mice intralymphatic RNA vaccination elicited protective and therapeutic antitumor immune responses, resulting in a remarkable survival benefit as compared with other treatment regimens. This is the first report of strong systemic antigen-specific Th1-type immunity and cancer cure achieved with naked antigen-encoding RNA in preclinical animal models. Cancer Res; 70(22); 9031-40. ©2010 AACR.

Vaccination with in vitro transcribed RNA coding for tumor antigens is considered a promising approach for cancer immunotherapy and has already entered human clinical testing. One of the basic objectives for development of RNA as a drug is the optimization of immunobioavailability of the encoded antigen in vivo. By analyzing the effect of different synthetic 5 0 mRNA cap analogs on the kinetics of the encoded protein, we found that m 2 7,2 0 ÀO Gpp S pG (b-S-ARCA) phosphorothioate caps, in particular the D1 diastereoisomer, profoundly enhance RNA stability and translational efficiency in immature but not mature dendritic cells. Moreover, in vivo delivery of the antigen as b-S-ARCA(D1)-capped RNA species is superior for protein expression and for efficient priming and expansion of naïve antigen-specific T cells in mice. Our findings establish 5 0 mRNA cap analogs as yet another module for tuning immunopharmacological properties of recombinant antigen-encoding RNA for vaccination purposes.

Genetic modification of vaccines by linking the Ag to lysosomal or endosomal targeting signals has been used to route Ags into MHC class II processing compartments for improvement of CD4+ T cell responses. We report in this study that combining an N-terminal leader peptide with an MHC class I trafficking signal (MITD) attached to the C terminus of the Ag strongly improves the presentation of MHC class I and class II epitopes in human and murine dendritic cells (DCs). Such chimeric fusion proteins display a maturation state-dependent subcellular distribution pattern in immature and mature DCs, mimicking the dynamic trafficking properties of MHC molecules. T cell response analysis in vitro and in mice immunized with DCs transfected with Ag-encoding RNA showed that MITD fusion proteins have a profoundly higher stimulatory capacity than wild-type controls. This results in efficient expansion of Ag-specific CD8+ and CD4+ T cells and improved effector functions. We used CMVpp65 and NY-ESO-1 Ags to study preformed immune responses in CMV-seropositive individuals and cancer patients. We show that linking these Ags to the MITD trafficking signal allows simultaneous, polyepitopic expansion of CD8+ and CD4+ T cells, resulting in distinct CD8+ T cell specificities and a surprisingly broad and variable Ag-specific CD4+ repertoire in different individuals.

Even though it is known for more than one decade that antigen-encoding RNA can deliver antigenic information to induce antigen-specific immunity against cancer, the nature and mechanism of RNA uptake have remained enigmatic. In this study, we investigated the pharmacokinetics of naked RNA administered into the lymph node. We observed that RNA is rapidly and selectively uptaken by lymph node dendritic cells (DCs). Furthermore, in vitro and in vivo studies revealed that the efficient internalization of RNA by human and murine DCs is primarily driven by macropinocytosis. Selective inhibition of macropinocytosis by compounds or as a consequence of DC maturation abrogated RNA internalization and delivery of encoded antigens. Our findings imply that bioavailability of recombinant RNA vaccines in vivo highly depends on the density and the maturation stage of DCs at the administration site and are of importance for the design of RNA-based clinical immunotherapy protocols. Gene Therapy (2011) Keywords: vaccination; dendritic cells; RNA; macropinocytosis INTRODUCTION Antigen-encoding RNA has emerged as an attractive new vaccine format. Major advantages of RNA are efficient delivery of the complete antigenic information, transient expression and lack of genome integration, as well as cost-efficient and easy production in large amounts and high purity. 1 Moreover, through activation of the immune system via TLR3, TLR7 and TLR8, 2,3 RNA supports the induction of immune responses against the encoded protein.Of several in vitro and in vivo strategies utilizing antigen-encoding RNA as a vaccine format, 4 two are in clinical stage. One is based on adoptive transfer of autologous dendritic cells (DCs) transfected ex vivo with antigen-encoding RNA. [5][6][7] The other employs direct injection of naked RNA. 8,9 Feasibility and safety of vaccination protocols based on intradermal administration of naked RNA have been shown in preclinical and clinical settings and partial protection from tumor challenge has been achieved in mice. 10,11 However, at present, neither in animals nor in men, systemic immune responses let alone therapeutic effects were unequivocally demonstrated. It is assumed that rapid degradation by ubiquitous RNAses constraining pharmacologically efficient dosing of unprotected RNA contributes to the still suboptimal clinical effects. Knowledge about the nature and pharmacokinetics of RNA uptake in vitro and in vivo as well as the cell-type specificity is still scarce. Recently, we discovered that the administration route of naked RNA has a crucial impact on its efficacy as a vaccine. By injecting RNA directly into lymph nodes of mice, we achieved for the first time strong systemic antigen-specific Th1 type immunity and cancer cure in preclinical animal models. 12

HPV16 infections are associated with a variety of cancers and there is compelling evidence that the transforming activity of HPV16 critically depends on the expression of the viral oncoproteins E6 and E7. Therapeutic cancer vaccines capable of generating durable and specific immunity against these HPV16 antigens hold great promise to achieve long-term disease control. Here we show in mice that HPV16 E7 RNA-LPX, an intravenously administered cancer vaccine based on immuno-pharmacologically optimized antigen-encoding mRNA, efficiently primes and expands antigen-specific effector and memory CD8 + T cells. HPV-positive TC-1 and C3 tumors of immunized mice are heavily infiltrated with activated immune cells and HPV16-specific T cells and are polarized towards a proinflammatory, cytotoxic and less immune-suppressive contexture. E7 RNA-LPX immunization mediates complete and durable remission of progressing tumors. Circulating memory T cells are highly cytotoxic and protect from tumor rechallenge. Moreover, E7 RNA-LPX immunization sensitizes anti-PD-L1 refractory tumors to checkpoint blockade. In conclusion, our data highlight the potential of HPV16 RNA-LPX for the treatment of HPV-driven cancers.