Synergy Between in Situ Cryoablation and TLR9 Stimulation Results in a Highly Effective in Vivo Dendritic Cell Vaccine

[D.ap]

Abstract

Dendritic cells (DC) are professional antigen-presenting cells that play a pivotal role in the induction of immunity. Ex vivo-generated, tumor antigen-loaded mature DC are currently exploited as cancer vaccines in clinical studies. However, antigen loading and maturation of DC directly in vivo would greatly facilitate the application of DC-based vaccines. We have previously shown that in situ tumor destruction by ablative treatments efficiently delivers antigens for the in vivo induction of antitumor immunity. In this article, we show that although 20% of the draining lymph node DCs acquire intratumorally injected model antigens after in situ cryoablation, only partial protection against a subsequent tumor rechallenge is observed. However, we also show that a combination treatment of cryoablation plus TLR9 stimulation via CpG-oligodeoxynucleotides is far more effective in the eradication of local and systemic tumors than either treatment modality alone. Analysis of the underlying mechanism revealed that in situ tumor ablation synergizes with TLR9 stimulation to induce DC maturation and efficient cross-presentation in tumor-bearing mice, leading to superior DC function in vivo. Therefore, in situ tumor destruction in combination with CpG-oligodeoxynucleotide administration creates a unique "in situ DC vaccine" that is readily applicable in the clinic.

https://pubmed.ncbi.nlm.nih.gov/16849578/

[D.ap]

Development of TLR9 agonists for cancer therapy


Abstract

In vertebrates, the TLRs are a family of specialized immune receptors that induce protective immune responses when they detect highly conserved pathogen-expressed molecules. Synthetic agonists for several TLRs, including TLR3, TLR4, TLR7, TLR8, and TLR9, have been or are being developed for the treatment of cancer. TLR9 detects the unmethylated CpG dinucleotides prevalent in bacterial and viral DNA but not in vertebrate genomes. As discussed in this Review, short synthetic oligodeoxynucleotides containing these immune stimulatory CpG motifs activate TLR9 in vitro and in vivo, inducing innate and adaptive immunity, and are currently being tested in multiple phase II and phase III human clinical trials as adjuvants to cancer vaccines and in combination with conventional chemotherapy and other therapies.“

https://www.jci.org/articles/view/31414

[D.ap]

However, we also show that a combination treatment of cryoablation plus TLR9 stimulation via CpG-oligodeoxynucleotides is far more effective in the eradication of local and systemic tumors than either treatment modality alone.

CpG Oligodeoxynucleotide
CpG-oligodeoxynucleotides (ODN) is a short synthetic DNA containing unmethylated CpG motifs, highly prevalent in bacterial DNA, and recognized by Toll-like receptor 9 (TLR9), which is expressed by a variety of cells in the immune system.
From: Clinical Immunology (Fifth Edition), 2019-



“Abstract
CpG oligodeoxynucleotides (ODNs) bind to and activate Toll-like receptor 9 (TLR9), initiating an innate immune response that supports the subsequent development of adaptive immunity. Preclinical studies demonstrate that TLR9 agonists improve antigen presentation and the induction of vaccine-specific cellular and humoral responses. More than 100 clinical trials utilizing CpG ODNs have been conducted that evaluated their utility in preventing or treating allergy, infectious diseases, and cancer. This chapter reviews the results of those clinical trials. In broad terms, the data indicate that CpG ODNs are safe when used as vaccine adjuvants. They improve humoral and cellular immune responses, accelerate the induction of protective antibodies, and support the generation of higher and more persistent antibody titers when added to protein-based vaccines. CpG ODNs show great promise for inclusion in prophylactic vaccines designed to prevent infection. However, the magnitude of the immunity they induce appears insufficient to control the spread of established cancers.“

https://www.sciencedirect.com/topics/me ... nucleotide

[D.ap]

Abstract

Unmethylated cytosine-phosphate-guanosine (CpG) oligodeoxynucleotides (ODNs) are recognized by Toll-like receptor 9 (TLR9) found in antigen-presenting cells and B cells and can activate the immune system. Using CpG ODNs as an adjuvant has been found to be effective for treating infectious diseases, cancers, and allergies. Because natural ODNs with only a phosphodiester backbone are easily degraded by nuclease (deoxyribonuclease [DNase]) in serum, CpG ODNs with a phosphorothioate backbone have been studied for clinical application. CpG ODNs with a phosphorothioate backbone have raised concern regarding undesirable side effects; however, several CpG ODNs with only a phosphodiester backbone have been reported to be stable in serum and to show an immunostimulatory effect. In recent years, research has been conducted on delivery systems for CpG ODNs using nanoparticles (NPs). The advantages of NP-based delivery of CpG ODN include (1) it can protect CpG ODN from DNase, (2) it can retain CpG ODN inside the body for a long period of time, (3) it can improve the cellular uptake efficiency of CpG ODN, and (4) it can deliver CpG ODN to the target tissues. Because the target cells of CpG ODN are cells of the immune system and TLR9, the receptor of CpG ODN is localized in endolysosomes, CpG ODN delivery systems are required to have qualities different from other nucleic acid drugs such as antisense DNA and small interfering RNA. Studies until now have reported various NPs as carriers for CpG ODN delivery. This review presents DNase-resistant CpG ODNs with various structures and their immunostimulatory effects and also focuses on delivery systems of CpG ODNs that utilize NPs. Because CpG ODNs interact with TLR9 and activate both the innate and the adaptive immune system, the application of CpG ODNs for the treatment of cancers, infectious diseases, and allergies holds great promise.

Keywords: Toll-like receptor 9 (TLR9), immunostimulation, higher-order nanostructure of DNA, delivery system, nanoparticles

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3356174/