Wu-Bo Li

The use of Random Homozygous Gene Perturbation to identify novel host-oriented targets for influenza.

Conventional approaches for therapeutic targeting of viral pathogens have consistently faced obstacles arising from the development of resistant strains and a lack of broad-spectrum application. Influenza represents a particularly problematic therapeutic challenge since high viral mutation rates have often confounded many conventional antivirals. Newly emerging or engineered strains of influenza represent an even greater threat as typified by recent interest in avian subtypes of influenza. Based on the limitations associated with targeting virally-encoded molecules, we have taken an orthogonal approach of targeting host pathways in a manner that prevents viral propagation or spares the host from virus-mediated pathogenicity. To this end, we report herein the application of an improved technology for target discovery, Random Homozygous Gene Perturbation (RHGP), to identify host-oriented targets that are well-tolerated in normal cells but that prevent influenza-mediated killing of host cells. Improvements in RHGP facilitated a thorough screening of the entire genome, both for overexpression or loss of expression, to identify targets that render host cells resistant to influenza infection. We identify a set of host-oriented targets that prevent influenza killing of host cells and validate these targets using multiple approaches. These studies provide further support for a new paradigm to combat viral disease and demonstrate the power of RHGP to identify novel targets and mechanisms.

Identification of novel host-oriented targets for Human Immunodeficiency Virus type 1 using Random Homozygous Gene Perturbation

BackgroundHuman Immunodeficiency Virus (HIV) is a global threat to public health. Current therapies that directly target the virus often are rendered ineffective due to the emergence of drug-resistant viral variants. An emerging concept to combat drug resistance is the idea of targeting host mechanisms that are essential for the propagation of the virus, but have a minimal cellular effect.ResultsHerein, using Random Homozygous Gene Perturbation (RHGP), we have identified cellular targets that allow human MT4 cells to survive otherwise lethal infection by a wild type HIV-1NL4-3. These gene targets were validated by the reversibility of the RHGP technology, which confirmed that the RHGP itself was responsible for the resistance to HIV-1 infection. We further confirmed by siRNA knockdowns that the RHGP-identified cellular pathways are responsible for resistance to infection by either CXCR4 or CCR5 tropic HIV-1 variants. We also demonstrated that cell clones with these gene targets disrupted by RHGP were not permissible to the replication of a drug resistant HIV-1 mutant.ConclusionThese studies demonstrate the power of RHGP to identify novel host targets that are essential for the viral life cycle but which can be safely perturbed without overt cytotoxicity. These findings suggest opportunities for the future development of host-oriented therapeutics with the broad spectrum potential for safe and effective inhibition of HIV infection.

Function-first approaches to improve target identification in cancer

Target discovery for cancer is undergoing a sort of revival with an increasing need for improved therapeutics. Likewise, the strategies to discover new and better therapeutic targets have come full circle, with greater emphasis placed upon targets that are functionally relevant to the disease process. In this article, we review the evolution of cancer target discovery and discuss random homozygous gene perturbation, an emerging technology that combines the practicality of screening for new targets by emphasizing function as the primary criterion, with cutting-edge advances in gene-based screening of all potential targets in a cell.

Identification of hepatic microvascular adhesion-related genes of human colon cancer cells using random homozygous gene perturbation.

Random homozygous gene perturbation (RHGP), in combination with liver sinusoidal endothelial cell (LSEC) adhesion screening of clonal colon cancer cells with perturbed genes, was used to identify genes contributing to the hepatic microvascular adhesion of colon cancer cells. Plasmid vector encoding transactivator and gene search vector were transfected into HT‐29 human colorectal cancer cells to create a HT‐29 RHGP cell library; the adhesion of these library cells to primary cultured mouse LSEC significantly decreased in the presence of RSL1 ligand (inducer), indicating that most of the genes contributing to HT‐29 adhesion to LSEC were altered. Next, HT‐29 RHGP cell library fractions with upregulated or silenced LSEC adhesion‐related genes were isolated. Around 160 clones having altered expression in LSEC adhesion‐related genes were obtained, and nine relevant protein‐coding genes were identified. Some were proadhesive genes detected because of their overexpression in adherent HT‐29 cells (DGCR8 and EFEMP1 genes) and their silenced status in nonadherent HT‐29 cells (DGKE, DPY19L1, KIAA0753, PVR and USP11 genes). Others were antiadhesive genes detected because of their overexpression in nonadherent HT‐29 cells (ITPKC gene) and their silenced status in adherent HT‐29 cells (PPP6R2 gene). Silencing of PVR, DGCR8 and EFEMP1 genes decreased adhesion to LSEC and hepatic microvascular retention of HT‐29 cells. The results conclude that RHGP was a valuable strategy for the discovery of mechanisms regulating microvascular adhesion of circulating colon cancer cells before hepatic metastasis formation. Identified genes may contribute to understand the metastatic process of colon cancer and to discovering molecular targets for hepatic metastasis therapeutics.

Antibody targeting of TSG101 on influenza-infected cells

Influenza remains a significant cause of morbidity and mortality worldwide. Although vaccination programs and conventional antiviral therapies can reduce disease burden, increasing resistance to conventional therapies renders much of the population susceptible to infection. The present study focuses on an important host protein target, tumor susceptibility gene 101 (TSG101), which is functionally exploited (hijacked) by certain enveloped viruses to facilitate viral budding and release. We find that influenza viruses depend on TSG101 for progeny virion morphogenesis in infected host cells. Antibody-binding studies revealed that TSG101 is exposed at the surface of influenza-infected cells but remains intracellular in uninfected cells. Using recombinant TSG101 and influenza M1 protein, we demonstrated a direct interaction between these proteins involving the ubiquitin E2 variant domain of TSG101. These findings identify an interaction between TSG101 and M1 protein in infected cells. Furthermore, a monoclonal antibody directed against TSG101 reduced virus yields in cell-based assessment of influenza virus infection, underscoring the potential of the TSG101-M1 interaction as a possible antivi- ral therapeutic target. The display of TSG101 at the surface of infected cells, combined with evidence that TSG101 antibodies reduce virus yields, suggest that TSG101 plays an essential role in the budding process of influenza virus. Our findings may also suggest potential oppor- tunities for influenza treatment and prevention by using monoclonal antibody therapeutics to interfere with virus replication.