Norovirus causes winter vomiting disease, spreads quickly in cold months, and immunity is short-lived, allowing reinfection.
Winter vomiting disease, primarily triggered by the Norovirus, is most active and contagious during the colder months of the year. Infected individuals usually recover within a few days, but the immunity developed after infection is short-lived, meaning people can become reinfected several times over a brief period.
The Genetic Shield: Unlocking Natural Resistance to Winter Vomiting Disease
Remarkably, susceptibility to the virus is not uniform across all individuals. Some people possess a unique gene variant that confers natural resistance, protecting them from infection even after exposure to the virus. This finding sheds light on the intricate relationship between genetics and vulnerability to infectious diseases, offering potential avenues for understanding immunity and developing targeted preventive strategies.
“We wanted to trace the historical spread of the gene variant,” says Hugo Zeberg, senior lecturer in genetics at the Department of Physiology and Pharmacology, Karolinska Institutet, and researcher at the Max Planck Institute for Evolutionary Anthropology in Leipzig.
The FUT2 gene is the target of an enzyme found in the intestinal mucosa. One of its role is to place sugar molecules on the surface of the intestinal cells, and it is through these molecules that the Norovirus infects the gut. The protective gene variant is defective so that the enzyme fails to work – and without the sugar molecules, the virus is unable to enter the cells.
To trace the spread of the variant, the researchers analyzed the DNA of 4,343 prehistorical individuals from the past 10,000 years. The defective gene was brought to Europe in around 6,000 BCE by early farmers from what is now Turkey and then propagated throughout the population some 8,500 to 5,000 years ago. In the early societies of the first farmers, the vomiting sickness virus spread much more quickly than when humans lived in small groups.
“Our results suggest that this type of disease environment drove up the frequency of the gene variant as it protects against winter vomiting disease and confers on the bearer the advantage of not falling sick,” says Dr Zeberg.
By studying questionnaires and genetic material from biobanks with 700,000 modern humans, the researchers observed that people with the gene variant rarely had vomiting sickness, especially if they had double copies – one from each parent.
Mini-Guts Confirm: Full Norovirus Protection Conferred by Gene Variant
To confirm their findings, the researchers cultivated human gut organoids (or miniature guts) from gut biopsies. In so doing, they found that individuals with two copies of the gene variant were fully protected against Norovirus infection.
The study is published in Molecular Biology and Evolution and was conducted with researchers at Linköping University.
“Ascertaining why certain mutations arise and get selected allows us to better understand how they affect our health today,” says the study’s lead author Johan Nordgren, docent of medical microbiology at the Department of Biomedical and Clinical Sciences, Linköping University.
But there is a price to this protection: modern biobanks show an elevated risk of stomach ulcers and gallstones in the gene variant bearers.
“These are usually linked to stress and a high intake of fat, which was probably less common during the neolithic period,” says Hugo Zeberg.
As regards the clinical relevance of the study, Dr Zeberg says that knowledge that the gene variant provides full protection can be of use in risk assessment. An estimated twenty per cent of the Swedish population have double copies.
“But my chief interest is in evolutionary science,” he says. “Prehistoric DNA is a time machine that allows us to replay evolution and see how genetic mutations can be tied to events in the human environment.”
Source-Eurekalert