CAREER DEVELOPMENT & TRAINING
Factors influencing the epidemic potential of Dengue
Shannon Bennett, University of Hawaii
Project period: May 2007 - April 2009
Abstract:
Mosquito-borne viruses such as dengue (DENV) are prominent on Category A, B and C bioterrorism agent lists, and are among the most important emergent/resurgent infectious diseases at the dawn of the 21st century, causing major public health problems. DENV in particular has demonstrated an amazing capacity to invade and become established in new geographic regions. The 20th century pandemic of dengue/dengue hemorrhagic fever (DEN/DHF), which currently plagues 50 to 100 million people annually, has intensified in the past 25 years, with a dramatic increase in disease incidence and geographic expansion, including to parts of the US. Effective laboratory-based surveillance and analysis is paramount for the detection of emergent viruses and assessment of their epidemic potential based on their genetic properties. Genetic factors appear to be involved in DENV expansion and increasing pathogenesis based on phylogenetic analyses paired with epidemiological patterns. Partial sequence analysis of the phylodynamics of emerging DENV in Puerto Rico indicates sporadic nonrandom genetic changes associated with significant outbreaks, but it is unclear whether all emergent DENV would share similar patterns of genetic change. Furthermore, the phenotypic effects of these changes, with respect to disease causing potential, remains untested. We are in the process of investigating these important questions in multiple populations with a history of dengue outbreaks to determine a), whether DENV strains circulating before and during an epidemic differ consistently in their genetic composition and/or pattern of evolution (e.g., whether evolutionary change was effected by random genetic drift or non-random adaptive processes); and b), the potentially-disease-causing characteristics exhibited by these epidemic variants in experimentally infected mosquitoes.
Highly sensitive and portable aptamer-based sensing system for botulinum toxins
Jeffrey Tok, Lawrence Livermore National Laboratories
Project period: May 2007 - April 2009
Abstract:
Systematic Evolution of Ligands by Exponential Enrichment (SELEX) is an in vitro technique that utilizes a large population of randomized DNA or RNA sequences as the starting material to identify chemically functional molecules. Targets in which aptamers have successfully been generated include proteins, small molecules, whole cells (bacterial spores and viruses) and even nucleic acids. One of the main functions we seek in the nucleic acid sequences is their ability to recognize and bind to the target molecules. The nucleic acid library is composed of completely random sequences flanked by constant regions that help to amplify the oligonucleotide. In this proposal, we will apply the SELEX technique to generate high affinity aptamers against the heavy chain domain of Clostridium Botulinum Neurotoxin (Hc-BoNT). BoNThas been widely regarded as the “poison of all poisons”. In regard to its operating mechanism, BoNT functions primarily within the synaptic terminal to prevent the release of neurotransmitter. The neurotoxins operate by first binding to the neuronal membrane receptors, being taken up into an endosome-like compartment, and penetrating the endosome membrane via a pH-dependent translocation process. Once within the synaptic cytoplasm, BoNTs are able to cleave neuronal protein such that synaptic vesicle fusion is prevented, and thus inhibiting the release of neurotransmitter. With the threat of these bacterial toxins being used in biowarfare, it is thus imperative that a rapid yet sensitive aptamer-based detection assays for the BoNTs be developed.
