The potential efficacy of malaria vaccines have been demonstrated experimentally in humans immunized with irradiated sporozoites and in naturally infected individuals living in malaria endemic areas. A number of subunit vaccines targeting the pre-erythrocytic and erythrocytic stages of the Plasmodium parasite have recently undergone Phase I - III clinical trials. However, the transient and / or suboptimal protective efficacy of these subunit vaccine candidates has emphasized the critical need for more potent adjuvants to stimulate high levels of humoral and/or cellular immunity. TLR agonists based on unique pathogen associated molecular patterns (PAMPs) can function as strong stimulators of innate immune responses that promote protective adaptive immunity against viral, bacterial and protozoan pathogens. The proposed studies will utilize a well characterized TLR 5 agonist, flagellin, which has been used to developTLR-5 linked candidate vaccines to influenza (currently in clinical trial) and flaviviruses such as West Nile virus, Japanese encephalitis virus, and Dengue virus by VaxInnate. The techniques used for the design, purification and production of potent TLR agonist modified viral vaccines will be utilized to develop a P. falciparum malaria vaccine by fusing flagellin to full-length circumsporozoite (CS) protein or to well-defined, functional T and B cell epitopes of CS. The TLR5 agonist modified CS will serve both as a vaccine candidate as well as a model antigen that will help elucidate the critical parameters required for optimization of malaria-specific humoral and cellular immunity. Protective efficacy against sporozoite challenge will be determined in the transgenic parasite model and in rodent malaria models. Alternative routes of immunization will be explored to develop an intranasal needle-free vaccine which, if successful, could provide a safe, cost effective and easily administered malaria vaccines for use in endemic countries. The studies on CS will provide the framework for future rationale design of multi-antigen malaria vaccines that can target both erythrocytic, as well as pre-erythrocytic, stages of the parasite to provide highly efficacious vaccines for the 40% of the world's population currently at risk of malaria infection.
There is currently no malaria vaccine available to prevent the 250-500 million infections, and 1-2 million deaths, caused by Plasmodium. Effective bridging of innate and adaptive immunity is required to ensure that malaria vaccines can elicit strong T and B cell responses required for protective immunity. A potent TLR 5 agonist, flagellin, will be linked to P. falciparum CS protein to provide a cost-effective and safe vaccine for public health efforts to reduce the world-wide morbidity and mortality caused by the Plasmodium parasite.
| Nacer, A; Carapau, D; Mitchell, R et al. (2014) Imaging murine NALT following intranasal immunization with flagellin-modified circumsporozoite protein malaria vaccines. Mucosal Immunol 7:304-14 |
| Carapau, Daniel; Mitchell, Robert; Nacer, Adéla et al. (2013) Protective humoral immunity elicited by a needle-free malaria vaccine comprised of a chimeric Plasmodium falciparum circumsporozoite protein and a Toll-like receptor 5 agonist, flagellin. Infect Immun 81:4350-62 |
| Przysiecki, Craig; Lucas, Bob; Mitchell, Robert et al. (2012) Sporozoite neutralizing antibodies elicited in mice and rhesus macaques immunized with a Plasmodium falciparum repeat peptide conjugated to meningococcal outer membrane protein complex. Front Cell Infect Microbiol 2:146 |
| Rudra, Jai S; Mishra, Satish; Chong, Anita S et al. (2012) Self-assembled peptide nanofibers raising durable antibody responses against a malaria epitope. Biomaterials 33:6476-84 |
