Japanese researchers have linked higher body temperatures to increased resistance to diseases caused by viruses.
- In the study, mice exposed to cold a week before the flu died due to severe hypothermia.
- Rodents exposed to heat were very resistant to infection, even at increasing doses of virus.
- A high body temperature would promote increased production of bile acids, which modulate immune responses, in a manner dependent on the intestinal microbiota.
Fever is a common symptom of the flu and Covid-19. However, “its physiological role in host resistance to viral infection is unclear”, according to scientists from the University of Tokyo (Japan). This is why they carried out a study which suggests that high body temperatures could strengthen the body’s ability to fight pathologies caused by viruses. Additionally, researchers found that high temperatures suppressed virus replication and excessive inflammatory responses.
Mice more resistant to flu after exposure to heat
To reach this conclusion, they conducted experiments on mice. As part of their work, published in the journal Nature Communications, the rodents were exposed to heat or cold, more precisely to 4°C, 22°C or 36°C, one week before the flu. After viral infection was induced, most animals exposed to cold died due to severe hypothermia, whereas those exposed to heat were highly resistant to infection even at increasing doses of virus. “Mice exposed to high heat raise their basal temperature above 38°C, which allows them to produce more bile acids in a manner dependent on the gut microbiota,” explained Dr. Takeshi Ichinohe, author of the research in a statement.
Flu: deoxycholic acid suppresses viral replication
The team hypothesized that deoxycholic acid (DCA) signaling from the gut microbiota and its plasma membrane-bound receptor, “Takeda G protein-coupled receptor 5” (TGR5), increased the host resistance to influenza by suppressing viral replication and tissue damage dependent on neutrophils (which constitute the most abundant class of white blood cells). Analyzing the experiments, the researchers noticed that mice infected with the influenza virus showed a decrease in body temperature almost four days after the onset of illness and that they huddled together to stay cool. hot.
High body temperature increases host resistance to Covid-19
In addition to the results obtained on flu, scientists also tested the effect of high body temperature on Covid-19. They found that increasing the hamsters’ body temperature helped protect them against the virus. “In addition, certain bile acids are reduced in the plasma of Covid-19 patients who develop moderate disease. (…) Our discovery may provide insight into the variability of clinical manifestations of the disease in humans and allow to find approaches to mitigate the results of the coronavirus”, said Dr. Takeshi Ichinohe.
