Systematic Identification and Characterization of Cellular Factors Required for Virus Infection

Viruses are simple intracellular parasites that depend on their hosts for replication. Once they infect, viruses hijack or take control of many different proteins in our cells. They do this to shut down the body’s defenses and to make new viruses that can then spread to the next host. Our main goal is to identify and unravel the interactions between viruses and their hosts. Uncovering all of these interactions is challenging because there are many and they are often very complex. Also, we do not know which ones are the most important for the infection process.

Recent advances in human genome research allow us to take an unbiased approach to this problem. We can now eliminate each protein in a cell, one-by-one, and ask how its loss affects the virus. This approach is extremely powerful because we can test many cell proteins at the same time to rapidly identify the important ones.

Once we identify these cell proteins, we dig deeper to find out why they are so important to the virus and if we can use this information to better understand how to fight viral infections in the future.

Viral diseases represent one of the world’s highest social-economic burdens. With increased global trade and travel, climate change resulting in shifting viral vectors, and the emergence of new and often deadly viruses, it is necessary to develop new research, diagnostics, and therapeutic tools to fully understand existing as well as future pandemic and epidemic infections. For this, a thorough understanding of the basic lifecycle of viruses and the cellular factors and functions required for viral replication is needed. In turn, as obligatory, intracellular parasites, viruses exploit cellular processes such as signalling, membrane trafficking, molecular sorting, etc. Thus viruses provide valuable tools to study multiple aspects of normal cell function.

Our group is interested in deciphering the complex interactions that occur between poxviruses and their host cells. The Poxviridae comprise a family of viruses characterized by their unusual size, cytoplasmic replication, and large repertoire of genes. For humans the most dangerous poxvirus is variola, the causative agent of smallpox. Although eradicated, the threat of smallpox bioterrorism, the emergence of zoonotic poxviruses, and the continued use of these viruses for cancer therapy, have initiated in-depth analysis of the poxvirus family. In the laboratory we use vaccinia virus (VACV), the prototypic member of the Poxviridae. Like all poxviruses, VACV is a large, complex, enveloped, DNA virus that replicates exclusively in the cytoplasm of infected cells. In addition to its use at the smallpox vaccine, VACV was the first virus to be visualized microscopically, grown in tissue culture, purified, and chemically analyzed.

Our particular interests lie in uncovering novel mechanisms by which poxviruses subjugate host cell functions to facilitate their productive replication. For these studies we combine cellular, molecular, and virological techniques with state-of-the-art technologies such as automated image-based small compound and siRNA screening, advanced proteomics, live-cell, electron-, and super-resolution microscopy technologies. Particular focus is placed on investigating how VACV initiates endocytic internalization and uses cellular endocytic transport to its advantage. Currently, we are analyzing the cellular factors and functions required for cytoplasmic delivery of viral genomes and accessory proteins, initiation of viral genome replication, and assembly of new viral particles.
Not only will these studies provide a more detailed understanding of the cell biology of poxvirus infection, we have to opportunity to uncover novel functions of cellular factors. Additionally, this work has the potential to uncover general strategies used by viruses to subjugate their host cells and, by extension, the possibility to develop cell-targeting, broad-spectrum antiviral agents.