Characterization of Francisella tularensis-specific bacteriophages

点击翻译按钮获取中文摘要

Bacteriophages are viruses that infect and kill bacteria either by disrupting their metabolism or by causing bacterial lysis. These unique properties of bacteriophages have been exploited as antimicrobial agents for over 100 years. The emergence of antibiotic resistance and the lack of introduction of new antibiotics in recent years, has renewed interest in the development of bacteriophage-based therapies in clinical situations where antibiotics are no longer effective. The overall goal of this proposal is to characterize a panel of bacteriophages that could further be developed as a therapy to treat fatal human disease tularemia caused by a Gram-negative bacterium, Francisella tularensis (Ft). Ft is a highly ubiquitous, infectious, intracellular bacterium prevalent throughout North America. Ft is classified as a Tier 1 Category A select agent by the CDC due to its history of weaponization by several countries, and its potential to be used as a bioterror agent. Anthrax powder attacks after 9/11 incidence have renewed the medical and scientific interest in Ft research. Tularemia is a notifiable disease in the USA. Naturally occurring tularemia is reported from all the states of the USA, except Hawaii. Currently, no vaccine is available for tularemia prophylaxis. Unfortunately, antibiotic treatment is not particularly effective against severe respiratory tularemia and may not be effective at all, if a weaponized antibiotic-resistant strain used in a bioterror attack causes an outbreak. Together, these indicate that the development of effective therapeutic measures against this dreaded biothreat agent is necessary. Bacteriophages may provide an excellent alternative to the conventional antibiotic therapy for the treatment of tularemia with the added advantage being that they are innocuous, self-replicating, amplify at the site of infection, and do not perturb microbiota. However, bacteriophages against Francisella have not been reported in the literature to-date. As a proof-of-concept, we have isolated a panel of Francisella-specific lytic phage populations from environmental samples. In specific aim 1 of this proposal, we will isolate a collection of individual Ft-specific phages from these samples and characterize their genetic, biochemical, and physical properties. In specific aim 2, we will characterize their biological properties. Specifically, we will determine their growth characteristics, host-range, and potential cell surface receptors. We will formulate an Ft-specific phage cocktail and develop assays to test the ability of phage cocktail(s) to kill intracellular Francisella. This is a first comprehensive study directed at the characterization of Ft-specific bacteriophages. Isolation and characterization of Ft-specific phages against Category A Tier-1 select agent Ft SchuS4 and formulation of novel Ft-specific bacteriophage cocktail capable of killing intracellular bacteria constitute the most innovative aspects of this proposal. We expect that the outcome of the proposed studies will pave the way for the development of a novel therapeutic approach for the treatment of tularemia in humans.