ARS | Publication request: High pressure inactivation of human norovirus virus-like particles: evidence that the capsid of human norovirus is highly pressure resistant

Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 16, 2012
Publication Date: May 15, 2012
Citation: Fangfei, L., Huang, P., Neetoo, H., Gurtler, J., Niemira, B.A., Chen, H., Jaing, X., Li, J. 2012. High pressure inactivation of human norovirus virus-like particles: evidence that the capsid of human norovirus is highly pressure resistant. Applied and Environmental Microbiology. DOI: 10.1128/AEM.00532-12.

Interpretive Summary: Human norovirus is a pathogenic virus, and a leading cause of intestinal illness worldwide. High pressure processing has been considered a promising non-thermal processing technology to inactivate food- and water-borne viral pathogens. Due to the lack of an effective cell culture for human norovirus, the effectiveness of high pressure processing on inactivating human norovirus remains unknown. Therefore, developing a new model system to evaluate the survival of human norovirus is urgently needed. We evaluated the effectiveness of high pressure processing on disrupting the structure and function integrity of virus-like particles, non-pathogenic particles that resemble human norovirus. We evaluated them by direct examination via electron microscopy and by measurement of the binding ability of the treated particles. Pressurization at 500-600 megapascals (MPa) was not sufficient to disrupt the structure and function of these particles, even with a very long holding time of 60 min. The disrupting efficacy of high pressure processing increased with the pressure level. The time required for a complete disruption of the particles at 700, 800, and 900 MPa was 45, 15, and 2 min, respectively. Pressure-treated particles are better able to bind to type A blood antigens than to the types B and O blood antigens. Additionally, smaller particles appeared to be much more stable than the larger particles. A treatment of 800-900 MPa is capable of effectively disrupting the structure of the human norovirus within a short holding time. The virus-like particles therefore represents a better model than two commonly used model organisms, the murine norovirus and the feline calicivirus. With a better model to work with, high pressure processing can be more effectively developed as a method to inactivate human pathogenic viruses on food.

Technical Abstract: Human norovirus (NoV) is the leading cause of non-bacterial acute gastroenteritis epidemics worldwide. High pressure processing (HPP) has been considered a promising non-thermal processing technology to inactivate food- and water-borne viral pathogens. Due to the lack of an effective cell culture for human NoV, the effectiveness of HPP on inactivating human NoV remains unknown. Therefore, developing a new model system to evaluate the survival of human NoV is urgently needed. Using human NoV virus-like particles (VLPs) as a model, we evaluated the effectiveness of HPP on disrupting human NoV based on the structure and function integrity of VLPs by electron microscopy and histo-blood group antigen (HBGA) receptor binding assays. We found that pressurization at 500-600 MPa for 2 min, a pressure level that completely inactivates the murine norovirus (MNV) and feline calicivirus (FCV), was not sufficient to disrupt the structure and function of human NoV VLPs, even with a holding time of 60 min. The disrupting efficacy of HPP increased with the pressure level. The time required for a complete disruption of human NoV VLPs at 700, 800, and 900 MPa was 45, 15, and 2 min, respectively. The human NoV VLPs are more resistant to HPP in their ability to bind the type A than the types B and O HBGAs. Additionally, the 23-nm VLPs appeared to be much more stable than the 38-nm VLPs. While human NoV VLP is highly resistant to HPP, a level of 800-900MPa is capable of effectively disrupting human NoV capsid within a short holding time. The apparent high resistance of human NoV capsid to HPP also indicates that the human NoV VLPs represents a better model than MNV and FCV to study the survival of human NoV under various conditions.