Micro-NMR and Nanoparticle Amplification                              for Botulinum Toxin                                              Diagnostics

Recombinant Envelope Protein Domain III as a                              Candidate Subunit Dengue                               Vaccine

A Highly Sensitive, Low-labor Pathogen Detector                              Based on Retroreflector-                              linked Immunosorbent                              Assay

Genetic Screens to Identify the Ebola Virus Receptor

High-throughput Assay Development Against                              Cryptosporidium Glycotlytic                              Enzymes

Model for Oral Ingestion of Ricin Toxin

Recombinant Envelope Protein Domain III as a Candidate Subunit Dengue Vaccine

Collaborating Institution: University of Texas Medical Branch, Galveston, TX

Principal Investigator: Alan Barrett, Ph.D.

Expected Product: Subunit vaccine for dengue virus.

Description: Effective vaccines exist for only a few members of the genus Flavivirus, including yellow fever, tick-borne encephalitis, and Japanese encephalitis. There are no effective prophylactic treatments for the diseases caused by any of these viruses, including dengue (DEN). The disease DEN is caused by four mosquito-borne, serologically related flaviviruses known as DEN1 to DEN4, and is the most important arboviral disease of humans. An estimated 50-100 million cases of dengue fever and hundreds of thousands of cases of dengue hemorrhagic fever occur in the tropics each year. Thus there is a need for a tetravalent vaccine. Since DEN is an emerging disease that is a major public health problem throughout tropical regions of the world, developing a DEN vaccine fits into the strategic plan of the WRCE to develop vaccines against biothreat agents and emerging infectious diseases.
To date no candidate DEN vaccines have gotten beyond Phase II clinical trials, demonstrating a need to take a novel approach to developing a DEN vaccine. Each DEN virus consists of multiple genetic groups, termed genotypes. In the last few years, there is evidence that Asian and American genotype viruses differ antigenically, and that Asian genotype viruses are not neutralized by sera prepared against American genotype viruses, at least for DEN2 virus. This latter point may become an important issue for vaccine development as all candidate vaccines to date are based on DEN strains from Thailand in Asia. Therefore, the long-term objective of these studies is the development of a candidate subunit vaccine that induces neutralizing antibodies, but not antibody-dependent enhancement antibodies, against all genotypes of all four DEN viruses. To achieve this goal, we are proposing preclinical studies on a subunit vaccine based on domain III of the envelope protein (ED3). We hypothesize that a monovalent ED3 immunogen will induce antibodies that will neutralize members of all genotypes of the particular DEN virus and that residue E-390 in ED3 is part of a critical neutralizing epitope on DEN2 virus. Furthermore, we hypothesize that a tetravalent ED3 DEN vaccine will induce a protective immune response against all four DEN viruses without the induction of cross-reactive antibodies that may enhance DEN infection and lead to DHF. For this developmental project we will focus on DEN2 virus to justify our hypothesis.
The following specific aims are proposed: 1) express DEN2 virus domain III of the virus envelope protein (ED3) each from an Asian and American genotype virus and compare their immunogenicity in a mouse model; and 2) evaluate a tetravalent rED3 vaccine in the mouse model.