Filoviruses, Ebola and Marburg, are causative agents of sever hemorrhagic fever in humans with case-fatality rates exceeding 88%. Filoviruses, designated as category A select agents by the Centers for Disease Control and Prevention, are considered potential biowarfare agents and therefore a serious threat to public health and national security. Furthermore, outbreaks in Africa have been on the rise in the past 15 years. There are currently no vaccines or therapeutics available for treatment or prophylaxis of filovirus hemorrhagic fever. Most current vaccine platforms under development utilize viral vectors such as adenovirus or vesicular stomatitis virus. While some of these approaches may prove to be good post-exposure treatment options, they are problematic as vaccines due to pre-existing vector immunity in a sizable portion of the population (in the case of adenovirus) and/or safety concerns in particular in immune-compromised populations (in the case of live viral vectors). An additional challenge is development of a vaccine that can convey broad protection to different pathogenic species and strains of filoviruses without the need for blending multiple individual vaccines. To date no cross protective vaccination strategy has been described that can protect against Sudan and Zaire Ebolaviruses or between an Ebola and a Marburg virus. The objective of this proposal is to develop a vaccine platform based on purified proteins that (i) is easy to produce, and (ii) provides broad protection against multiple species of filoviruses. In this proposal, relying on a rational and structure-based antigen design and strong preliminary data, we propose to develop a protein-based vaccine based on an engineered antigen in which the highly conserved receptor binding region of the viral glycoprotein is exposed as a result of deletion of highly glycosylated mucin-like domain. Our preliminary studies using this approach showed, for the first time, cross protection between Ebola and Marburg viruses.
In Specific Aim 1 we will produce engineered antigens for Zaire and Sudan Ebolaviruses as well as Lake Victoria Marburgvirus using a baculovirus/insect cell expression system. The vaccine preparations will be thoroughly characterized.
In Aim 2 we will evaluate the immunogenicity of the new vaccine platforms in comparison to a first generation virus like particle (VLP) vaccine currently under development in our group. The immunogenicity study will include cross reactive total and neutralizing antibody titers between all strains as well as evaluation of the T cell responses. Homologous and heterologous efficacy against lethal challenge will be tested initially in mice and then in the more stringent guinea pig model with the goal of demonstrating pan Filovirus protective efficacy. A strong team of scientists with decades of cumulative experience in filovirology, vaccine development, and animal studies under biocontainment, has been assembled to perform this important project. Upon completion of this Phase I SBIR we anticipate to have identified a single vaccine candidate that is easy to produce and capable of protecting against different Filovirus strains as divergent as Zaire and Marburg. Demonstration of the vaccine candidate efficacy in nonhuman primates and further preclinical development can be pursued in a subsequent Phase II project.
Filoviruses, Ebola and Marburg, are among the deadliest viruses and can cause severe hemorrhagic fever in humans. There is serious concern that these viruses can be used as a bioterror agent. There is currently no vaccine or drugs available for prevention or treatment of Filovirus infections. In this proposal, using a novel approach, we seek to develop a vaccine that is easy to produce and would protect against several strains of filoviruses.