Infectious Disease Control

(1) Development of drugs against Category A bacterial pathogens. Infectious diseases continue to represent a major threat to the health of the human population. One of the most significant threats is the intentional use of infectious agents for bioterrorism. New strategies are urgently needed to counteract this threat. The Institute will bring together microbiologists and chemists with the aim of developing novel drugs that can be used to prevent or treat infections caused by Category A bacterial pathogens in the human population. Stony Brook has significant expertise in this area. Dr. Bliska and Dr. R. Johnson will direct this project. Collaborators for this project will be drawn from the Departments of Molecular Genetics and Microbiology, Physiology and Biophysics, Biochemistry and Cell Biology, and Chemistry. The Center for Infectious Diseases, which is located in the new Centers for Molecular Medicine at Stony Brook, has three biological containment laboratories (Biosafety Level 3 and Biosafety Level 2) that are equipped to perform cutting edge research on highly contagious agents. The three bacterial agents that will be the focus of our research efforts are Bacillus anthracis, which causes anthrax, Francisella tularensis, which causes tularemia, and Yersinia pestis, which causes plague. These agents are in the CDC Category A list of pathogens that have the highest potential for use as bioterrorism agents.

ICB&DD plans to develop i) highly specific and novel inhibitors against key secreted protein toxins that are unique to each of these bacteria and ii) novel inhibitors that target essential cytoplasmic proteins that are common to all three agents. The novel antibiotics against these lethal bacteria will be developed with DOD and NIAID as a part of bioterrorism/homeland security programs. Pharmaceutical and biotechnology firms in the New York State will be targeted for technology transfer related to newly discovered inhibitors.

(2) New drugs for multi-drug resistant tuberculosis. The CDC has estimated that one third of the world's population are infected with Mycobacterium tuberculosis (Mtb), the organism that causes tuberculosis, and that 10% of these individuals will develop active infections. Currently, more than two million people die annually and there are 8.8 million new cases every year. Critical issues in the treatment and control of tuberculosis include the role of this disease as a major opportunistic pathogen in patients with HIV/AIDS and the emergence of multi-drug resistant strains of the organism (MDR-TB). MDR-TB is much more difficult to treat than sensitive TB, requiring administration of more expensive, second-line antibiotics for up to two years. Consequently, NIAID has classified MDR-TB as a category C priority pathogen. Accordingly, the Institute plans to focus on the discovery and development of new drugs that are effective against Mtb. The Institute currently has the following three approaches for the drug discovery and development.

(a) Enoyl reductase (ENR) inhibitors.
InhA, the enoyl reductase from M. tuberculosis, catalyzes the NADH-dependent reduction of enoyl-ACPs and is the target for the antitubercular drug isoniazid (INH). The enzyme is involved in biosynthesis of fatty acids and enzyme inhibition interferes with the synthesis of mycolic acid, a critical component of the mycobacterial cell wall. A substantial fraction of all clinical isolates that are resistant to INH result from mutations in KatG the enzyme that activates INH, rather than from mutations in InhA. Consequently, compounds that inhibit the ultimate molecular target(s) of INH, but that don't require activation by KatG, have tremendous promise as novel drugs for combating MDR-TB. Consequently, InhA is a bona fida target for the development of novel antitubercular agents. INH inhibits InhA by forming a covalent adduct with the nicotinamide cofactor. Dr. Tonge has succeeded in synthesizing the INH-NAD adduct and has discovered that it is a slow, tight-binding inhibitor of InhA with a Ki of 1 nM. Currently, Dr. Tonge is evaluating the impact of InhA mutations, identified in INH-resistant clinical strains, on adduct formation and affinity. In addition, Dr. Tonge is performing SAR studies with the enoyl reductase inhibitor triclosan. Triclosan, an antibacterial compound added to consumer products such as toothpaste, is a submicromolar inhibitor of InhA, and a range of triclosan analogs have been synthesized to dissect inhibitor-enzyme interactions. Data from the SAR studies, in combination with the X-ray structure of the InhA-triclosan complex solved by Dr. Kisker and Dr. Tonge, are being used to design novel InhA inhibitors. The Institute will organize a project team to boost this highly promising drug discovery and development project.

(b) FtsZ inhibitors.
FtsZ is the first nonregulatory element to appear at the septum site of bacteria, and the function of the septum has been shown to depend on correct FtsZ function. FtsZ is a cytosolic protein that polymerizes in a GTP-dependent manner and has been shown to be the bacterial tubulin homologue. The sequence similarity between FtsZ and tubulin, however, is generally low (<20% identity). Thus, FtsZ is a highly promising target for new antimicrobial drugs because of its central role in bacterial cell division. Dr. Ojima in collaboration with Dr. Kirikae (Director, Department of Infectious Diseases and Tropical Medicine, International Medical Center of Japan) has very recently discovered that several new generation taxanes possess significant antibacterial activity against resistant M. tuberculosis, which likely block FtsZ function. Interestingly, paclitaxel (TAXOLŽ) is totally inactive. These taxanes are extremely important hits for the development of novel class of antibiotics against M. tuberculosis. Accordingly, the Institute is organizing a project team including Dr. Ojima, Dr. Kirikae, Dr. Tonge, Dr. Kisker, and Dr. Simmerling for this highly promising project.

(c) Cholesterol oxidation.
There are many reports that mycobacteria oxidize cholesterol, and that the oxidation activity is inducible. Importantly, cholesterol oxidation has been linked to pathogenicity. The enzymes responsible for this activity comprise a pathway that is not typically targeted by anti-TB pharmaceuticals, and their inhibition could lead to improved host response in combating infection. However, the protein(s) responsible for the activity has(have) never been isolated, and the mechanism of pathogenicity is poorly understood. Dr. Nicole Sampson will head experiments which aim to identify the gene and characterize the protein or proteins responsible for cholesterol oxidation in Mycobacterium tuberculosis. The hypothesis is that cholesterol oxidation activity represents a new target for anti-MDR-TB pharmaceutical development because 1) cholesterol oxidation is essential for virulence and 2) these enzymes are absent in humans. With this work, they will elucidate the role of cholesterol oxidation in host cell infection by characterizing the protein products of putative M. tuberculosis cholesterol oxidizing genes, and evaluating the differential transcription profile of M. tuberculosis grown in the presence and absence of cholesterol.