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Sporozoite Vaccine Administration Method


OBJECTIVE: To develop an innovative method for administering a malaria sporozoite vaccine that provides efficient access by the sporozoites to the intravascular space, thereby mimicking direct intravenous (IV) delivery. This innovative method should contrast with traditional intramuscular (IM), subcutaneous (SC) or intradermal (ID) methods delivering sporozoites primarily to the interstitial space. Proof-of-concept should be established in animal models using cryopreserved malaria sporozoites as the Phase I objective, with pre-clinical development, clinical testing and FDA licensure of a P. falciparum sporozoite vaccine (administered by this novel method) projected for later development phases. The sporozoite is the infectious stage of the malaria parasite transmitted to humans by the female Anopheles mosquito. The sporozoites used for proof-of-principle in this SBIR should be purified and cryopreserved. The cryopreserved sporozoites can be either fully infectious or radiation-attenuated. Ideally, proof-of-principle for IV equivalency should be established using both types. The most important demonstration will be to demonstrate equivalent protection to IV administration, using radiation-attenuated sporozoites. See the Phase I project description for more details. The method may incorporate novel administration devices, locations, volumes, formulations or other innovative approaches, and should be equivalent to the current gold standard, direct intravenous inoculation, as measured by sporozoite infectivity, vaccine immunogenicity or vaccine efficacy on subsequent malaria challenge. The method should be amenable to routine use in vaccination clinics at military medical treatment facilities, primarily for adult recipients but ideally suitable also for pediatric applications. While the primary target is US Army / DoD military medical operations, a secondary target is medical operations for other government agencies and the general public. DESCRIPTION: Malaria has been identified as most significant infectious disease threat during deployments to tropical and subtropical regions. The first formal determination of malaria"s importance was made by the Infectious Diseases Investment Decision Evaluation Algorithm (ID-IDEAL) in 2003, which ranked malaria #1 out of 40 infectious diseases considered (Burnette, Hoke et al. 2008). The same conclusion was reached in 2012 by the Infectious Disease Threat Prioritization Panel, which ranked malaria #1 out of 38 infectious diseases (Infectious Disease Threats to the US Military Prioritization Panel Results; Memorandum for Record, Fort Sam Houston, TX, 2010). This prioritization reflects malaria"s historical role as the leading cause of person-days lost from active duty in conflicts taking place in tropical regions, including approximately 12 million person-days lost for Navy and Marine Corps personnel during WWII and 1 million person-days lost during the Vietnam Conflict (Beadle & Hoffman, 1993). In October 2003, malaria inflicted a 44% casualty rate on a 157 person Marine Expeditionary Unit deployed to Roberts International Airport in Monrovia, Liberia, aborting the peace-keeping mission after 12 days on the ground (Whitman, Coyne et al. 2010). These casualties occurred despite the availability of effective malaria drug prophylaxis and personal protective measures, indicating a major shortfall in the ability to sustain the performance of US military forces in the tropics. The evacuations from Liberia and subsequent hospitalizations cost the military approximately $1.2M (Roberts, in preparation). This shortfall would be entirely eliminated by an effective vaccine. For this reason, the DoD formalized the requirement for a malaria vaccine in the document"Operational Requirements Document for Plasmodium Falciparum Malaria Vaccine"issued by the Army Training and Doctrine Command and approved on 13 March 1997 by the Deputy Chief of Staff for Combat Developments. The requirement has been updated by the document"Capability Development Document For Plasmodium Falciparum Malaria Vaccine"issued by the Army Medical Research and Materiel Command and approved 01 April 2010 by the US Army Deputy Chief of Staff. Since 2000, the DoD had invested more than $100M in malaria vaccine development, focusing on three different promising vaccine platforms: (1) recombinant malaria proteins formulated in adjuvant (e.g., RTS,S/AS01B Vaccine); (2) malaria genes delivered as DNA plasmids or by non-replicating viral vectors (e.g., NMRC-M3V-D/Ad-PfCA Vaccine); and (3) metabolically active, non-replicating (attenuated), whole malaria sporozoites. This past fall (2012), whole malaria sporozoite vaccines emerged as the most protective approach to date. In a dose escalation trial of purified, cryopreserved, radiation-attenuated sporozoites (PfSPZ Vaccine, Sanaria Inc., Rockville, MD), 6/6 research subjects (100%) were fully protected against Plasmodium falciparum sporozoite challenge. The human challenge model exposes research subjects to malaria via infectious mosquito bite; it is also called controlled human malaria infection or CHMI. In the second highest dose group, 6/9 research subjects (67%) were fully protected. This was only the second time that the PfSPZ Vaccine has been tested in a clinical trial. These protection results are the best achieved by a candidate malaria vaccine administered by any route other than by mosquito bite. The route of delivery used in the recent trial described above was direct intravenous inoculation, since the first clinical study of the same vaccine delivered SC or ID showed protection of less than 10% (Epstein, Tewari et al. 2011). The IV route bypasses the initial tissue stage of infection, in that, during normal malaria transmission, most sporozoites are deposited by the probing mosquito within the epidermis or dermis or potentially subcutaneously depending on the depth of proboscis penetration. The mosquito searching for a blood meal probes the skin multiple times, depositing sporozoites in a single stream with each probing. Jin and colleagues at New York University demonstrated in the murine model that during mosquito probing, sporozoites are released at a relatively slow rate (approximately 1 to 2.5 per second) from the mosquito proboscis (Jin 2007). In the earlier trial with SC or ID administration, the purified cryopreserved parasites were deposited"en masse"in a bolus of fluid, as occurs with traditional SC or ID administration. This is very different from what occurs with mosquito probing. Since sporozoites do not"swim,"instead requiring the interstitial substrate to achieve the gliding motility that normally enables locating and entering the vascular system and subsequent travel to the liver, it could be that deposition within a lacunae of fluid inhibits entry into the vasculature. In addition, it is possible that, due to the shock of cryopreservation and subsequent thawing, radiation-attenuated parasites such as those comprising the PfSPZ Vaccine are less effective at moving through the interstitial space, penetrating the vascular wall and gaining access to the vascular system than non-cryopreserved radiation-attenuated sporozoites freshly injected by a mosquito. Intravenous administration effectively bypasses this initial skin phase of infection, thereby effectively circumventing both of these disadvantages. Intravenous administration thus revealed the potency of the PfSPZ Vaccine for providing sterile protection against malaria, achieving 100% protection in the high dose group. Although direct intravenous inoculation appeared to be safe and well tolerated in the recent study and could be administered in the controlled environment of DoD personnel prior to deployment to endemic areas, it would nevertheless be useful to identify an alternative method of delivery that mimics the ability of IV administration to elicit high grade protection. In developing this concept, improved methods of vaccine delivery could be demonstrated in animal models by (1) administering intact cryopreserved sporozoites and using infection as the outcome variable, or by (2) administering radiation-attenuated cryopreserved sporozoites and using protection as the outcome variable. With either the intact sporozoites/infection model or the attenuated sporozoites/protection model, there is a roughly 5 to 25 fold difference in dose comparing IV to ID or SC administration to achieve equivalent infection or protection (Hoffman, personal communication; Ploemen, Chakravarty et al. 2012). This SBIR solicitation is based on the assumption that a non-IV method can be developed that eliminates this multifold difference, permitting infectivity and/or protection that is equivalent to that achieved by direct IV administration. Applicants are encouraged to think"outside the box"by proposing highly innovative approaches and then assessing these approaches in animal models. Of note, novel vaccine delivery methods applicable to malaria sporozoites may prove equally applicable to other infectious agents for which we currently lack effective vaccines. Product requirements: a vaccination method for delivering cryopreserved malaria sporozoites that: - is safe and well tolerated (military personnel may not be placed in down status). - achieves equivalent potency relative to direct single needle IV administration, meeting DoD criteria of>80% protection (preferred:>90% protection) in humans. - can be administered in routine fashion at military medical treatment facilities. - is suitable for adult application (preferred: additionally suitable for pediatric including infant application). - is able to receive FDA approval for administration of a sporozoite vaccine. - can be adequately scaled to meet military needs. - is cost-effective. PHASE I: Perform experiments in animal models to demonstrate that the proposed method of sporozoite delivery is equivalent or superior to gold standard IV administration. Purified, cryopreserved or purified, cryopreserved, radiation-attenuated sporozoites should be used. The endpoint should be infectivity and/or protective efficacy, as measured by parasite liver load, proportion of animals positive, or other suitable outcome measure. The proof-of-principle, if conducted in a rodent malaria model, should be readily translatable to P. falciparum whole sporozoite vaccines, such as the PfSPZ Vaccine, and should have a clear pathway for pre-clinical and clinical development, licensure and deployment by the DoD. Please identify technical risks of the approach, as well as the costs, benefits and schedule associated with development for clinical use. Map out a well-constructed clinical development plan. Identify minimum system requirements for deployment. PHASE II: Perform pre-clinical development of the novel method for delivering the P. falciparum whole sporozoite vaccine through IND allowance. Manufacture sufficient material for pre-clinical and clinical development. Include a plan for scale-up manufacturing, licensure, marketing and effective implementation in the DoD. Include estimates of resources required to fully implement the method"s use in 100,000 military personnel. Include a business plan that addresses required partnerships and issues of intellectual property such that unrestricted government use at reasonable cost is assured. PHASE III: Assess the safety, tolerability, immunogenicity and efficacy of the novel method for delivering the P. falciparum whole sporozoite vaccine and demonstrate equivalence or superiority to direct, single needle IV administration. Fully develop the data set required for FDA licensure. Detail product and associated consumables costs. Provide full specifications for manufacturing materials and processes and product storage and shipment. Provide a detailed plan for licensure and transition to DoD acquisition programs. REFERENCES: 1. Beadle C & Hoffman SL. (1993)."History of malaria in the United States Naval Forces at war: World War I through the Vietnam conflict."Clin Infect Dis 16(2):320-9. 2. Burnette, WN, Hoke CH, et al. (2008)."Infectious diseases investment decision evaluation algorithm: a quantitative algorithm for prioritization of naturally occurring infectious disease threats to the U.S. military."Mil Med 173(2): 174-81. 3. Epstein JE, Tewari K, et al. (2011)."Live attenuated malaria vaccine designed to protect through hepatic CD8(+) T cell immunity."Science 334(6055):475-80. 4. Jin Y, Kebaier C & Vanderberg J. (2007)."Direct microscopic quantification of dynamics of Plasmodium berghei sporozoite transmission from mosquitoes to mice."Infect Immun 75(11):5532-9. 5. Ploemen IH, Chakravarty S, et al. (2012)."Plasmodium liver load following parenteral sporozoite administration in rodents."Vaccine. 6. Whitman TJ, Coyne PE, et al. (2010)."An outbreak of Plasmodium falciparum malaria in U.S. Marines deployed to Liberia."Am J Trop Med Hyg 83(2): 258-65.
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