CHS Research Group Noroviruses
Dr. Grant Hansman
Noroviruses are the dominant cause of outbreaks of gastroenteritis around the world. Currently, there are no vaccines or antivirals for human noroviruses. Cross-protection from future norovirus infections is uncertain and it is not uncommon for re-infection with a genetically similar strain. The objective of our research group is to better understand the molecular basis of norovirus capsid antigenicity, flexibility, and interaction with receptors and binding factors. Ultimately, we expect to develop novel antivirals against human noroviruses.
Aim 1. Norovirus interactions with receptors
The human histo-blood group antigens (HBGAs) have been identified as potential co-factors for norovirus. The HBGAs are complex carbohydrates linked to proteins or lipids present on epithelial cells and other cells in the body or found as free antigens. At least nine different HBGAs have been described that can bind to norovirus. Noroviruses bind to HBGAs at the outer surface of the capsid. The interaction is coordinated by both hydrophobic and hydrophilic interactions, but the binding is different among the genetically diverse norovirus strains. Our group is currently deciphering the different norovirus interactions with a panel of HBGAs using X-ray crystallography.
Aim 2. Norovirus drug discovery
Recently, we analyzed the interaction of citrate with noroviruses using X-ray crystallography and saturation transfer difference (STD) NMR. We found that the citrate interaction was coordinated with an almost identical set of capsid interactions as involved in recognizing the terminal HBGA fucose, the saccharide that forms the primary conserved interaction between HBGAs and genogroup II noroviruses. STD NMR showed the protruding domain to have weak affinity for citrate, but could compete against the soluble HBGAs for the HBGA binding site. Our group is screening candidate drug molecules that bind and inhibit norovirus attachment to cells using a combination of X-ray crystallography, Biacore, and cell culture.
Aim 3. Norovirus capsid flexibility and antibody binding
Recently, we determined the cryo-EM structure of a human norovirus virus-like particle (VLP) and showed that the protruding (P) domain was raised off the shell (S) domain by ~15 Å. The exposed regions on the lower side of the P domain ultimately allowed monoclonal antibodies to bind at occluded sites on the VLPs. It was interesting to note that we found the human genogroup VLP was more similar to an infectious murine norovirus virion than to the prototype human norovirus VLP, which had a P domain resting on the S domain. Our group is currently studying other norovirus VLPs using a combination of X-ray crystallography and cryo-EM in order to identify sites of vulnerability, to untangle the importance of the flexible P domain, and to answer questions of antigenicity.
Aim 4. Development of a novel reverse genetics system for human noroviruses
Human noroviruses are uncultivable in cell culture, but reverse genetic systems have shown that VLPs can be generated and these were likely to be infectious. Our group plans to improve on previously developed reverse genetic systems and describe particle formation and viral entry using a variety of tools.
Hansman GS, Taylor DW, McLellan JS, Smith TJ, Georgiev I, Tame JRH, Park SY, Yamazaki M, Gondaira F, Miki M, Katayama K, Murata K, and Kwong PD. (2012) Structural basis for broad detection of genogroup II noroviruses by a monoclonal antibody that binds to a site occluded in the viral particle. J Virol 86: 3635-3646.
Hansman GS, Shahzad-ul-Hussan S, McLellan JS, Chuang G, Georgiev I, Shimoike, T, Katayama K, Bewley, CA, and Kwong PD. (2012) Structural basis for norovirus inhibition and fucose mimicry by citrate. J Virol 86: 284-292.
Hansman GS, Biertümpfel C, Georgiev I, McLellan JS, Chen L, Zhou T, Katayama K, Kwong PD. (2011) Crystal Structures of GII.10 and GII.12 Norovirus Protruding Domains in Complex with Histo-Blood Group Antigens Reveal Details for a Potential Site of Vulnerability. J Virol 85: 6687-6701.
Ozawa K, Oka T, Takeda N Hansman GS (2007) Norovirus infections in symptomatic and asymptomatic food handlers in Japan. J Clin Microbiol 45: 3996-4005