The common cold and other respiratory illnesses frequently occur together when the weather is cold.
This is due to a number of factors, including the fact that during the winter months, people tend to spend more time indoors, and viruses work out better in air with a lower humidity level. However, there has been less clarity as to whether or not lower temperatures do, in fact, decrease human immunity and, if they do, how this happens.
Now, a new research that was published on Tuesday in The Journal of Allergy and Clinical Immunology describes a previously unknown method that the immune system targets viral invaders within the nose. The study also found that it functions better when it is warm.
Mansoor Amiji, a professor of pharmaceutical sciences at Northeastern University and one of the research’s co-leaders, told AFP that these discoveries might help pave the road for a future therapy against the common cold and other viruses.
In 2018, Amiji and colleagues conducted research in which they discovered that nasal cells generated “extracellular vesicles” (EVs), which were a spray of small sacs that swarmed and killed germs upon inhalation. This served as the basis for the current study.
Amiji stated that a hornet’s nest is the most appropriate example that they could make. EVs will swarm and kill intruders, much to how hornets protect a nest from an attack.
In the course of the new investigation, the group sought answers to the following two questions: When a person has a viral infection, do EVs also get secreted from the nose? And if they do, is the intensity of their response proportional to the temperature they are exposed to?
Researchers employed a test substance that imitate a viral infection to stimulate nasal mucosa, which is a thin tissue that borders the inside of the nose. This tissue was collected from participants who had surgery to remove polyps so that they could answer the first question.
They discovered that it did, in fact, create EVs that targeted viruses in their research.
In order to answer the second issue, they cultivated the nasal cell samples in the laboratory, exposing one set of samples to 37 degrees Celsius, and the other set of samples to 32 degrees Celsius. This allowed them to compare the results of the two temperatures.
These values were selected based on the findings of a different experiment which indicated that the temperature within the nose lowers by approximately 5C when the temperature of the air outside drops from 23C to 4C.
Under normal conditions of body heat, the EVs were able to successfully fight off viruses by providing them with “decoy” targets that they could latch on to instead of the receptors that they would normally target on cells. This was accomplished by presenting the viruses with the receptors that they would normally target on cells as a form of distraction.
However, because of the lower temperatures, there were fewer EVs formed, and those that were made had less of an impact against the invaders that were examined. These invaders included two rhinoviruses and a non-COVID coronavirus, all of which are often prevalent during the winter cold season.
In a statement, co-author Benjamin Bleier, who is a surgeon at Harvard Medical School and Massachusetts Eye & Ear said that there’s never been a persuasive rationale why you get this very evident rise in viral infection rates in the cold months.
This is the first answer that has been produced that is both measurable and credible from a biological standpoint.
According to Amiji, one of the most interesting and promising parts of the research is the possibility of stimulating the body’s natural production of virus-targeting EVs in order to combat or perhaps fight off the common cold, as well as the flu and COVID.
Cold exposure impairs extracellular vesicle swarm–mediated nasal antiviral immunity, Journal of Allergy and Clinical Immunology (2022). DOI: 10.1016/j.jaci.2022.09.037