Gastroviruses

Lennart Svensson, Professor, virology.
Lennart Svensson, Professor. Ulrik Svedin - Linköpings unive

My group investigates disease mechanisms of virus associated with acute gastroenteritis such as norovirus and rotavirus (the winter vomiting disease, "vinterkräksjuka"), and the role of human genetics in susceptibility and resistance to human viral infections.

Enteroids Lennart Svensson.Fig. 1. Human  enteroids. 3D culture of a human  ileum enteroid (A), enterochromaffin 
cell in yellow (B)  and human rotavirus infected 2D human enteroids (C).
Photo credit Lennart Svensson - LiU
Rotavirus and norovirus (the winter vomiting disease, “vinterkräksjuka”) are major causes of acute diarrhea worldwide, with a burden of  >500,000 deaths per year, predominantly in developing countries. The underlying disease mechanisms are still unresolved. The clinical importance of these infections is significant and a vaccine against rotavirus has been introduced globally.
Our research on rotavirus and norovirus is hypothesis driven and translational. Currently, we investigate the cross-talk between enterochromaffin cells, enteric glia cells, enteric nerves and CNS during rotavirus and norovirus infections and how infection activates brain structures associated with the feeling of sickness. We also investigate human genetic factors associated with rotavirus and norovirus susceptibility, to explain why certain individuals get sick and not others when exposed.

Current projects at a glance

Does the vagal nerve and/or enteric glial cells contribute to maintaining a tight intestinal epithelium during rotavirus infection? Prover med stamceller, Lennart Svensson, professor i molekylär virologi vid Linköpings universitet. Foto - Ulrik Svedin - LiU Cell samples from small intestine. Photo credit Ulrik Svedin
We have previously shown that intestinal permeability remains unaffected during rotavirus infection in children and mice, which is in contrast with increased intestinal permeability during bacterial infections. Since intestinal permeability is partially regulated by the vagus nerve and neurotrophic factors released from enteric glial cells, we propose that vagus and/or enteric glial cells contribute to maintaining a tight intestinal epithelium during rotavirus infection. These studies may uncover how the gut epithelium remains intact during rotavirus infection in human and mice.

Human enteroids: A novel cultivation model for human norovirus

The major barrier to research and development of effective interventions for human norovirus infections has been the lack of a robust and reproducible in vitro cultivation system and a small animal model.Immunohistochemistry of rotavirus infected duodenum of mice.  Red shows  rotavirus infected cells and green activated enteric glia cells.Fig.2. Immunohistochemistry of rotavirus infected duodenum of mice. Red shows rotavirus infected cells and green activated enteric glia cells Photo credit Lennart Svensson     A major advance in this field was recently described by Ettayebi et al (Science 2016), who reported successful cultivation of multiple human norovirus strains in enterocytes of stem cell–derived enteroid cultures. The enteroids are produced from small intestinal biopsies donated by consenting individuals and contain stem-cells that developed/derived into multiple intestinal epithelial cell types including enterocytes, goblet cells, enterochromaffin- and Paneth cells. This non-transformed culture system recapitulates the human intestinal epithelium, permits human host-pathogen studies of previously non-cultivatable pathogens, and allows the assessment of methods to prevent and treat human norovirus infections. The method is established in my group and explored for several kind of experiments such as determination of norovirus infectivity in clinical specimens, co-culturing of enteroids with enteric nerves and/or enteric glia cells. 

Human enteroids to identify restriction factors 
to rotavirus and norovirus infection

Human gut-virus studies have been hampered by use of sub-optimal in vitro intestinal cell models, mainly transformed cells. In this project we take advantage of the non-transformed human enteroid model to identify the cellular receptor for rotavirus and norovirus and to identify restriction factors limiting infections of certain types of rotavirus in certain geographic regions. Our hypothesis is that polymorphisms in secretor- and Lewis antigens restrict certain rotavirus infections. To address this question, we take advantage of the library of human enteroids that we have built from patients with different genetic set up.

Are there individual-specific responses in the gut 
to rotavirus and norovirus?

Historically virus-host interactions have been investigated using different pathogens on transformed cell cultures. This (may) answer the question how different pathogens interact on the same cells, but do not answer if the host responses to a single pathogen is unique to each individual. To address this question, we investigate the innate response of a single virus specimen to differentiated enteroid cultures obtained from 10-12 individuals with different polymorphisms with respect to FUT2 and FUT3, genes encoding secretor- and Lewis antigens respectively.

Does rotavirus activate brain structures associated with sickness feeling?

Rotavirus infection includes sickness feeling such as nausea, fever, loss of appetite and social withdrawn. The mechanism and signaling pathways underlying these symptoms is unresolved.Marie Hagbom, forskningsingenjör och expert pÃ¥ stamceller, Lennart Svensson, professor i molekylär virologi vid Linköpings universitet. Foto - Ulrik Svedin - LiU Marie Hagbom studies cells in microscope. 
Photo credit
Ulrik Svedin
A novel objective is to identify the activated regions in the CNS following rotavirus infection, giving raise to sickness feeling. We have previously shown that rotavirus activate the enteric nervous system (Lundgren et al, Science, 2000) and the vomiting center (Hagbom et al, PLoS Path, 2011) and those studies are the basis for our further investigations. Our working hypothesis is that rotavirus infection of the small intestine activates regions within hypothalamus and/or dorsal motor nucleus via the vagus nerve. 

Will gastrointestinal viral infection affect telomere 
length and the biological clock?

Virus infection can induce various cellular remodeling events and stress responses, including telomere-specific alterations. While previous studies have shown thatLennart Svensson, professor i molekylär virologi vid Linköpings universitet. Foto - Ulrik Svedin - LiU Lennart Svensson, Professor. Photo credit Ulrik Svedin - LiU viral infection in the gastrointestinal tract accelerate differentiation of crypt cells
towards mature enterocytes, no information is available if teleomere length and thus life span and the biological clock is affected. 

In a collaboration with Asghar Huhammad and Anna Färnert, we investigate if acute infection with rotavirus and norovirus accelerate aging by shorting the telomere length.

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