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In light of the recent novel H1N1 virus epidemic, virus resistance to currently approved antiviral medications has become a global health concern. Since almost all circulating strains of influenza A viruses are resistant to either adamantanes or neuraminidase inhibitors, new therapeutic approaches and means to discover new antiviral agents are critical to address the issue of recurring drug resistance. We postulate that computational molecular docking provides an efficient and innovative approach to examine small molecules against influenza viruses. We have identified a potent inhibitor of the H5N1 neuraminidase protein from a library of 23,000 compounds. This compound demonstrated anti-viral activity efficacy in vitro across a number of cell-lines assays in H5N1, H1N1, H9N2/G1, H3N2 and the oseltamivir-resistant H1N1 virus while the compound itself did not show any cytotoxicity. The underlying mechanisms including immunoregulation, upstream signalling pathways and neuraminidase inhibitory activity were also studied. It was found that the compound inhibit the viral titers via inhibiting the neuraminidase activity. Upon successful demonstration of the effectiveness of the compound in the cell culture model, we further validated the anti-influenza effect of the compound in a mouse model. BALB/c mice were administrated once daily with the compound or diluent control (DMSO). They were then intranasally infected with A/PR/8/34 influenza virus. The mice were treated with the compound or DMSO through oral gavage for five more days starting from 8 h post-infection. Our results showed that the compound prolonged the life span and increased the survival rate of the mice. These results demonstrated that the compound screened from molecular docking is a new potential drug candidate for inhibiting viral replications of different influenza viruses.

Tuberculosis (TB) is generally acquired through inhalation of airborne droplets containing Mycobacterium tuberculosis (Mtb). Macrophages are one of the pivotal cells in innate immunity against mycobacteria. Mycobacteria activate macrophages to produce proinflammatory cytokines such as TNF- α which controls Mtb infection. The cytokine is crucial for granuloma formation, induction of macrophage apoptosis and production of chemokines to recruit cells in tuberculosis. TNF- α biosynthesis is known to be controlled at the transcriptional and post-transcriptional levels. Emerging studies have shown that microRNAs (miRNAs), a family of single stranded, non-coding, short RNAs, act as post-transcriptional regulators of gene expressions. MiRNA-mediated regulations are essential in various developmental and cellular processes including tumor development and immune responses. MiRNAs regulate innate immunity and shape adaptive immunity. They target mRNAs of toll-like receptors (TLR), cellular signaling molecules, transcription factors or cytokines as to regulate the immunity. In this study, it was shown that various miRNAs were induced in primary human macrophages by Bacille Calmette-Guerin (BCG), a vaccine for TB. MiR-1303, which has not been shown to have function, was found to regulate BCG-induced TNF- α mRNA and protein production. It was shown that by knock-down of miR-1303, BCG-induced TNF- α protein expression was upregulated. In contrast, overexpression of miR-1303 can suppress the TNF- α protein expression. Additionally, it was demonstrated that miR-1303 could control levels of phosphorylated extracellular-signal-regulated kinase (ERK) and phosphorylated p38 mitogen-activated protein kinase (p38 MAPK). Further studies on the mechanisms of the regulation will be required and the studies will delineate how miRNAs manipulate immune responses to mycobacteria infection.

The 2010 Annual General Meeting and Scientific Meeting of the Hong Kong Society for Immunology (HKSI), Hong Kong, 17 April 2010.