Difficulties in Developing a Vaccine Against Norovirus

Norovirus is considered the leading cause of foodborne illness in the US.  The main reasons for this is how easily it spreads (acute onset vomiting), low infectious dose, and ability to remain active in the environment.  Another key is that the body does not easily become immune to the virus, and with that, there are no available vaccines.

The reason for this is the changing complexity of the outer capsid structure.  This shell changes structure significantly from strain to strain.  And of course this structure is what antibodies find and lock onto in order to eliminate from the body.

Technology Networks
https://www.technologynetworks.com/biopharma/news/steps-towards-a-food-poisoning-vaccine-320589
Norovirus Structure Far More Complex Than First Thought 
News   Jun 13, 2019 |

 Original story by the Cold Spring Harbor Laboratory

Noroviruses are a leading cause of food-borne illness outbreaks, accounting for 58% of all outbreaks and cause 685 million cases worldwide each year. There is no effective therapeutic against them. Having knowledge of the intricate structure of the outer layer of noroviruses, the capsid, which allows the virus to attach to its human host, could help in vaccine development.

In vaccines, specific antibodies recognize the capsids and bind to them so they can no longer interact with human cells. “We need to understand what the norovirus capsid shapes actually look like, and the shape differences between different strains,” said James Jung, a postdoctoral fellow in Dr. Leemor Joshua-Tor’s lab at Cold Spring Harbor Laboratory (CSHL).

Jung and Joshua-Tor led a team to solve the high-resolution structures of four different strains of noroviruses using a cryo-electron microscope. This allowed them to see the intricate architecture of virus shells in high-definition. Their findings are published in the journal PNAS.

Jung gleaned new insights that could help in guiding the development of therapeutics to fight norovirus infection. “Previously, it was thought that the norovirus shells exist in single-sized assemblies consisting of 180 building blocks and 90 surface spikes. What we found was an unexpected mixture of different shell sizes and shapes. We found a smaller form, which consists of just 60 building blocks with 30 surface spikes placed further apart. We also found larger shells made out of 240 building blocks with 120 surface spikes that are lifted significantly above the base of the shell and form a two-layered architecture that could interact differently with the human cells,” he said.

Rest of story - https://www.technologynetworks.com/biopharma/news/steps-towards-a-food-poisoning-vaccine-320589