Whooping cough, caused by Bordetella pertussis bacteria, causes 24.1 million cases and 160,700 deaths each year, according to the CDC. This is probably an underestimate, as many people don't report or aren't hospitalized for their illness, and thus are not counted in the total. Scientists are still trying to piece together the immune response we mount to the illness, particularly why whooping cough is most deadly in babies and toddlers.
Researchers from University of Maryland School of Medicine believe they have found part of the answer, and it lies in the differences in immune response between young children and adults. In this study, the researchers used lab mice infected with B. pertussis to mimic human infections, and studied the immune response following infection in infant and adult mice.
Type I and III interferons are cytokines, substances that are secreted by immune cells to signal that an infection is occurring. The elevated levels of Type I and III interferon seen in adult mice post-infection were not present in the infant mice in the study. The adult mice showed a delayed but significant increase in their interferon levels in the lungs, which stopped the bacterial infection from spreading throughout the body.
The infant mice had no interferon response, and as a result the B. pertussis bacteria were free invade the rest of the body. They eventually killed the young mice by stimulating an overwhelming, body-wide infection.
Could boosting interferon levels in babies and children improve their survival, and reduce mortality from this devastating disease? This, excitingly, opens a new door for pediatric whooping cough treatments.