Designing distribution of adjuvants: Synthesis of lipidated nucleic acid adjuvant compounds

<p>Peptide vaccines can generate antigen-specific immune responses against tumours. However, peptides on their own are not usually immunogenic and require an adjuvant to ensure antigen-presenting cells are appropriately activated. Adjuvant localisation is essential for its activity; targeting an immunomodulatory compound to the lymph nodes appropriately positions it among a high density of immune cells, where immune responses are coordinated. Furthermore, systemic distribution of a potent immune modulator can lead to severe systemic toxicities. Lymph node targeting reduces systemic exposure with simultaneous reduction of side effects. Where a compound distributes in viva is determined by its pharmacokinetic properties and its route of administration. Once the route has been defined, a drug's pharmacokinetic properties can be modified by structural changes. To this end, we modified existing adjuvants to distribute into the lymphatics preferentially. One method was to increase the hydrophilicity and size of agalactosylceramide to favour lymphatic uptake. The second was to exploit albumin hitchhiking to access the lymph nodes. Here, a-galactosylceramide was chemically linked via an enzyme-labile linker to CpG ODN 1826, a TLR-9 agonist. The properties of each adjuvant mutually alter those of the other: to the CpG, a-galactosylceramide acts as an albumin binding domain; to the a-galactosylceramide, the CpG serves as a large hydrophilic group creating an amphiphile. In vivo, this should activate a strong, multilineage T cell response through the synergy of the two adjuvants. Furthermore, this should reduce the toxicity and side effects of the adjuvant by limiting its systemic distribution. This adjuvant may find further use in vaccines for diseases requiring a Thl response for effective clearance.</p>

Designing distribution of adjuvants: Synthesis of lipidated nucleic acid adjuvant compounds

<p>Peptide vaccines can generate antigen-specific immune responses against tumours. However, peptides on their own are not usually immunogenic and require an adjuvant to ensure antigen-presenting cells are appropriately activated. Adjuvant localisation is essential for its activity; targeting an immunomodulatory compound to the lymph nodes appropriately positions it among a high density of immune cells, where immune responses are coordinated. Furthermore, systemic distribution of a potent immune modulator can lead to severe systemic toxicities. Lymph node targeting reduces systemic exposure with simultaneous reduction of side effects. Where a compound distributes in viva is determined by its pharmacokinetic properties and its route of administration. Once the route has been defined, a drug's pharmacokinetic properties can be modified by structural changes. To this end, we modified existing adjuvants to distribute into the lymphatics preferentially. One method was to increase the hydrophilicity and size of agalactosylceramide to favour lymphatic uptake. The second was to exploit albumin hitchhiking to access the lymph nodes. Here, a-galactosylceramide was chemically linked via an enzyme-labile linker to CpG ODN 1826, a TLR-9 agonist. The properties of each adjuvant mutually alter those of the other: to the CpG, a-galactosylceramide acts as an albumin binding domain; to the a-galactosylceramide, the CpG serves as a large hydrophilic group creating an amphiphile. In vivo, this should activate a strong, multilineage T cell response through the synergy of the two adjuvants. Furthermore, this should reduce the toxicity and side effects of the adjuvant by limiting its systemic distribution. This adjuvant may find further use in vaccines for diseases requiring a Thl response for effective clearance.</p>

Immunopotentiation by Lymph-Node Targeting of a Malaria Transmission-Blocking Nanovaccine

A successful malaria transmission blocking vaccine (TBV) requires the induction of a high antibody titer that leads to abrogation of parasite traversal of the mosquito midgut following ingestion of an infectious bloodmeal, thereby blocking the cascade of secondary human infections. Previously, we developed an optimized construct UF6b that elicits an antigen-specific antibody response to a neutralizing epitope of Anopheline alanyl aminopeptidase N (AnAPN1), an evolutionarily conserved pan-malaria mosquito midgut-based TBV target, as well as established a size-controlled lymph node targeting biodegradable nanoparticle delivery system that leads to efficient and durable antigen-specific antibody responses using the model antigen ovalbumin. Herein, we demonstrate that co-delivery of UF6b with the adjuvant CpG oligodeoxynucleotide immunostimulatory sequence (ODN ISS) 1018 using this biodegradable nanoparticle vaccine delivery system generates an AnAPN1-specific immune response that blocks parasite transmission in a standard membrane feeding assay. Importantly, this platform allows for antigen dose-sparing, wherein lower antigen payloads elicit higher-quality antibodies, therefore less antigen-specific IgG is needed for potent transmission-reducing activity. By targeting lymph nodes directly, the resulting immunopotentiation of AnAPN1 suggests that the de facto assumption that high antibody titers are needed for a TBV to be successful needs to be re-examined. This nanovaccine formulation is stable at -20°C storage for at least 3 months, an important consideration for vaccine transport and distribution in regions with poor healthcare infrastructure. Together, these data support further development of this nanovaccine platform for malaria TBVs.

Overcoming physiological barriers by nanoparticles for intravenous drug delivery to the lymph nodes

The lymph nodes are major sites of cancer metastasis and immune activity, and thus represent important clinical targets. Although not as well-studied compared to subcutaneous administration, intravenous drug delivery is advantageous for lymph node delivery as it is commonly practiced in the clinic and has the potential to deliver therapeutics systemically to all lymph nodes. However, rapid clearance by the mononuclear phagocyte system, tight junctions of the blood vascular endothelium, and the collagenous matrix of the interstitium can limit the efficiency of lymph node drug delivery, which has prompted research into the design of nanoparticle-based drug delivery systems. In this mini review, we describe the physiological and biological barriers to lymph node targeting, how they inform nanoparticle design, and discuss the future outlook of lymph node targeting.