Rhinovirus is a leading cause of asthma attacks, the common cold, and other respiratory illnesses. When cold viruses enter the nose epithelial cells lining the airways respond and often clear the virus before it can replicate and trigger symptoms; but others exposed to the virus will get mildly to seriously ill.
Epithelial cells were used in experiments from healthy human donors derived from either nasal passages or the lungs to investigate why. Both types of cells were exposed to rhinovirus and were maintained under the same conditions in cell culture, with more robust antiviral responses being observed in nasal cells.
In both lung and nasal cells RIG-1 surveillance pathway was triggered, it was found both cell types generated antiviral responses and defense responses against oxidative stress: nasal cell antiviral responses were stronger, but bronchial cell defense against oxidative stress was observed to be more pronounced.
Additional experiments found evidence of a tradeoff: antiviral defenses were shut down by defense responses against oxidative stress. Nasal cells were exposed to oxidative stress in the form of cigarette smoke, then to a cold virus, to investigate further and it was found nasal cells were more susceptible to the cold virus, surviving the cigarette smoke but not being able to fight off the virus very well allowing the virus to grow.
Delicate balances between the body’s different mechanisms are suggested by the findings: Airway linings protect against viruses and harmful substances that enter, which do well when encountering one stressor at a time, however when trying to deal with another stresser type it can adapt but the cost is susceptibility to rhinovirus infection.
The study shows mechanistic links between environmental exposures and susceptibility to the common cold, and may explain why smokers tend to be more susceptible to rhinovirus infection, according to the researchers, who hope findings will help lead to discovery of strategies to combat respiratory viruses that can cause an estimated 500 million colds and 2 million hospitalizations per year within the USA alone.
