I work on three areas: 1) molecular interactions between viruses and the host cells; 2) transport between the cell cytoplasm and the nucleus and 3) transmissible cancers. I have made seminal contributions in each of these fields.

I pioneered the study of retroviral capsid uncoating (J. Virol. 1999, 2001,2003), which to this day is a major topic of research in the field. We providedthe first demonstration that the HIV-1 capsid protein enters the nucleus ofinfected cells and affects integration; we proposed a new step in the HIV-1life cycle called “nuclear uncoating” (J. Biol. Cem. 2010; PLoS Pathog 2011;Retrovirology 2016). More recently, we found that the capsid protein promotesHIV-1 integration into clusters of functionally related genes that regulateT-cell activation and metabolism (PLoS Pathog. 2017; Sci Rep. 2017). Currently, we are investigating how the 3D organization of chromatin in which HIV-1 has integrated may regulate latency and its reversal. We are also carrying out research to understand why Th17 cells are preferentially infected by HIV-1 and depleted, a key event leading to AIDS pathogenesis.

In collaboration with Bart Hoogenboom (UCL Centre for Nanotechnology), we described the biophysical properties of the native nuclear pore complex using atomic force microscopy, which provided a model to understand passage of large macromolecules such as viruses, across the nuclear envelope (Nature Nanotech 2015). By studying tRNAs that are selectively incorporated into HIV-1 particles, we found that, contrary to dogma, tRNAs are re-imported into the nucleus in human cells by an active pathway (PLoS Biol. 2006). This pathway, conserved from yeast to human, is now called "tRNA retrograde transport". HIV-1 exploits this pathway to gain access to the nucleus (PLoS Biol;. 2006, PLoS Pathog. 2011). We showed that tRNA retrograde transport is part of the response to oxidative stress (Cell Reports 2019).  We are now seeking to map the components of the tRNA retrograde transport pathway and to understand if this pathway affects codon usage by changing the pool of tRNAs in the cytoplasm in response to oxidative stress. Because several viruses induce oxidative stress, we hypothesize that they may induce tRNA retrograde transport to change codon usage to their advantage.

With Robin Weiss, we demonstrated the clonal origin of the canine transmissible venereal tumour (CTVT), proving that a mammalian cell can evolve into a transmissible cancer cell "parasite" (Cell 2006). CTVT often regresses after treatment with the drug vincristine. We found that CTVT regression depends on acute inflammation of the host cells surrounding the tumour and upregulation of chemokine CCL5, which attracts and retains immune cells into the tumour site (Cancer Cell 2018). We are currently investigating how vincristine activates the innate immune system and how it induces CCL5 expression. We are also working to understand how CTVT can bypass allorecognition. We use CTVT as a model to study cancer regression and immunoevasion.