Antigens reversibly conjugated to a polymeric glyco-adjuvant induce protective humoral and cellular immunity

Fully effective vaccines for complex infections must elicit a diverse repertoire of antibodies (humoral immunity) and CD8+ T-cell responses (cellular immunity). Here, we present a synthetic glyco-adjuvant named p(Man-TLR7), which, when conjugated to antigens, elicits robust humoral and cellular immunity. p(Man-TLR7) is a random copolymer composed of monomers that either target dendritic cells (DCs) via mannose-binding receptors or activate DCs via Toll-like receptor 7 (TLR7). Protein antigens are conjugated to p(Man-TLR7) via a self-immolative linkage that releases chemically unmodified antigen after endocytosis, thus amplifying antigen presentation to T cells. Studies with ovalbumin (OVA)-p(Man-TLR7) conjugates demonstrate that OVA-p(Man-TLR7) generates greater humoral and cellular immunity than OVA conjugated to polymers lacking either mannose targeting or TLR7 ligand. We show significant enhancement of Plasmodium falciparum-derived circumsporozoite protein (CSP)-specific T-cell responses, expansion in the breadth of the alpha CSP IgG response and increased inhibition of sporozoite invasion into hepatocytes with CSP-p(Man-TLR7) when compared with CSP formulated with MPLA/QS-21-loaded liposomes-the adjuvant used in the most clinically advanced malaria vaccine. We conclude that our antigen-p(Man-TLR7) platform offers a strategy to enhance the immunogenicity of protein subunit vaccines.

Myeloid Cells Orchestrate Systemic Immunosuppression, Impairing the Efficacy of Immunotherapy against HPV+ Cancers

Gabriele Galliverti, Douglas Hanahan, Melody Swartz, Mélanie Louise Tichet, Stephan Wullschleger, Nadine Zangger

Cancers induced by human papillomaviruses (HPV) should be responsive to immunotherapy by virtue of expressing the immunogenic oncoproteins E6/E7. However, advanced forms of cervical cancer, driven by HPV, are poorly responsive to immune response-enhancing treatments involving therapeutic vaccination against these viral neoantigens. Leveraging a transgenic mouse model of HPV-derived cancers, K14HPV16/H2b, we demonstrated that a potent nanoparticle-based E7 vaccine, but not a conventional "liquid" vaccine, induced E7 tumor antigen-specific CD8(+) T cells in cervical tumor-bearing mice. Vaccination alone or in combination with anti-PD-1/anti-CTLA4 did not elicit tumor regression nor increase CD8(+) T cells in the tumor microenvironment (TME), suggesting the presence of immune-suppressive barriers. Patients with cervical cancer have poor dendritic cell functions, have weak cytotoxic lymphocyte responses, and demonstrate an accumulation of myeloid cells in the periphery. Here, we illustrated that myeloid cells in K14HPV16/H2b mice possess potent immunosuppressive activity toward antigen-presenting cells and CD8(+) T cells, dampening antitumor immunity. These immune-inhibitory effects inhibited synergistic effects of combining our oncoprotein vaccine with immune checkpoint-blocking antibodies. Our data highlighted a link between HPV-induced cancers, systemic amplification of myeloid cells, and the detrimental effects of myeloid cells on CD8(+) T-cell activation and recruitment into the TME. These results established immunosuppressive myeloid cells in lymphoid organs as an HPV+ cancer-induced means of circumventing tumor immunity that will require targeted abrogation to enable the induction of efficacious antitumor immune responses.

AMER ASSOC CANCER RESEARCH2020

Development of a nano-adjuvant cancer vaccine and its evaluation for melanoma in combination with radiotherapy

Sylvie Hauert

Cancer is the second leading cause of death in the world and melanoma is the deadliest type of skin cancer. Although surgery, radiotherapy and chemotherapy are still standard treatments, the discovery of the role played by the immune system in cancer has allowed the development of new treatments, called immunotherapies. The goal of these treatments is to help the immune system eradicate cancerous cells, for example by increasing the anti-tumor response of the patient. In this particular case, the treatment has to activate cytotoxic CD8+ and CD4+ helper T cells against the cancer cells. This can be done by using subunit vaccines composed of tumor antigens, adjuvants and a delivery system, which will be internalized by dendritic cells (DCs) and induce its activation followed by the migration to the lymph nodes where it will educate T cells against specific antigens. Our laboratory has developed two different delivery systems, nanoparticles (NPs) and polymersomes (PSs) that can enhance the vaccineâs immune response by efficiently entering the lymphatic system, due to their size, and drain to the lymph node. Once they reach that location, they will be internalized by DCs and induce an anti-tumor response. In this thesis, we used these two nanocarriers to create a vaccine composed of different nano-adjuvants capable of activating several toll-like receptors simultaneously and test their efficacy at inducing an anti-tumor response in melanoma. We have developed and characterized the different nano-adjuvants, PS-MPLA, PS-CL075 and NP-CpG-B, and demonstrated, in vitro, synergistic effects on DC activation when PS-MPLA + PS-CL075 and PS-MPLA + NP-CpG-B were combined. In vivo, we showed the enhanced immune response with the different nano-adjuvant combinations, but only PS-MPLA + NP-CpG-B was able to delay tumor growth in melanoma. We then tested this vaccine in combination with radiotherapy, mimicking a clinical situation. We first demonstrated an enhanced immune response when combining a high irradiation dose, 15 Gy, with the nano-adjuvant vaccine draining the tumor-draining lymph node. Moreover, the vaccination of NP-CpG-B + PS-MPLA and radiotherapy increased mice survival by 17 days compared to mice only receiving radiotherapy. â Overall, we have demonstrated that combining different nano-adjuvants, targeting the tumor-draining lymph node, with radiotherapy enhanced significantly the survival in a melanoma model. This approach is particularly promising since ionizing radiation is a standard treatment in cancer and our vaccine can be applied to a multitude of cancer since it does not contain any antigen and its composition can easily be modified.

EPFL2018

Exploiting lymphatic transport and complement activation in nanoparticle vaccines

Jeffrey Alan Hubbell, Sai Reddy, Melody Swartz

Antigen targeting and adjuvancy schemes that respectively facilitate delivery of antigen to dendritic cells and elicit their activation have been explored in vaccine development. Here we investigate whether nanoparticles can be used as a vaccine platform by targeting lymph node-residing dendritic cells via interstitial flow and activating these cells by in situ complement activation. After intradermal injection, interstitial flow transported ultra-small nanoparticles (25 nm) highly efficiently into lymphatic capillaries and their draining lymph nodes, targeting half of the lymph node-residing dendritic cells, whereas 100-nm nanoparticles were only 10% as efficient. The surface chemistry of these nanoparticles activated the complement cascade, generating a danger signal in situ and potently activating dendritic cells. Using nanoparticles conjugated to the model antigen ovalbumin, we demonstrate generation of humoral and cellular immunity in mice in a size- and complement-dependent manner.