Aug
13
Tue
2013
Plenary Address: Making sense of pathogen sensors of Innate Immunity: Utility of their ligands as antiviral agens and adjuvants for vaccines. @ Acharya Hall
Aug 13 @ 9:17 am – 9:55 am

SuryaprakashSuryaprakash Sambhara, DVM, Ph.D
Chief, Immunology Section, Influenza Division, CDC, Atlanta, USA


Making sense of pathogen sensors of Innate Immunity: Utility of their ligands as antiviral agents and adjuvants for vaccines.

Currently used antiviral agents act by inhibiting viral entry, replication, or release of viral progeny.  However, recent emergence of drug-resistant viruses has become a major public health concern as it is limiting our ability to prevent and treat viral diseases.  Furthermore, very few antiviral agents with novel modes of action are currently in development.  It is well established that the innate immune system is the first line of defense against invading pathogens.  The recognition of diverse pathogen-associated molecular patterns (PAMPs) is accomplished by several classes of pattern recognition receptors (PRRs) and the ligand/receptor interactions trigger an effective innate antiviral response.  In the past several years, remarkable progress has been made towards understanding both the structural and functional nature of PAMPs and PRRs.  As a result of their indispensable role in virus infection, these ligands have become potential pharmacological agents against viral infections.  Since their pathways of action are evolutionarily conserved, the likelihood of viruses developing resistance to PRR activation is diminished.  I will discuss the recent developments investigating the potential utility of the ligands of innate immune receptors as antiviral agents and molecular adjuvants for vaccines.

Suryaprakash (1) Suryaprakash (4) Suryaprakash-Nagaraja

Invited Talk: Pertubation of DNA topology in mycobacteria @ Acharya Hall
Aug 13 @ 11:50 am – 12:12 pm

NagarajaV. Nagaraja Ph.D.
Professor, Indian Institute of Science, Bengaluru, India


Perturbation of DNA topology in mycobacteria

To maintain the topological homeostasis of the genome in the cell, DNA topoisomerases catalyse DNA cleavage, strand passage and rejoining of the ends. Thus, although they are essential house- keeping enzymes, they are the most vulnerable targets; arrest of the reaction after the first trans-esterification step leads to breaks in DNA and cell death.  Some of the successful antibacterial or anticancer drugs target the step ie arrest the reaction or stabilize the topo -DNA covalent complex. I will describe our efforts in this direction – to target DNA gyrase and also topoisomerase1 from mycobacteria. The latter, although essential, has no inhibitors described so far. The new inhibitors being characterized are also used to probe topoisomerase control of gene expression.

In the biological warfare between the organisms, a diverse set of molecules encoded by invading genomes target the above mentioned most vulnerable step of topoisomerase  reaction, leading to the accumulation of double strand breaks. Bacteria, on their part appear to have developed defense strategies to protect the cells from genomic double strand breaks. I will describe a mechanism involving three distinct gyrase interacting proteins which inhibit the enzyme in vitro. However, in vivo all these topology modulators protect DNA gyrase from poisoning effect by sequestering the enzyme away from DNA.

Next, we have targeted a topology modulator protein, a nucleoid associated protein(NAP) from Mycobacterium tuberculosis to develop small molecule inhibitors by structure based design. Over expression of HU leads to alteration in the nucleoid architecture. The crystal structure of the N-terminal half of HU reveals a cleft that accommodates duplex DNA. Based on the structural feature, we have designed inhibitors which bind to the protein and affect its interaction with DNA, de-compact the nucleoid and inhibit cell growth. Chemical probing with the inhibitors reveal the importance of HU regulon in M.tuberculosis.