Intranasal administration of the protein flagellin may activate innate immunity and protect against acute pneumonia say researchers from France. They report their findings in the October 2010 issue of the journal Infection and Immunity.
Streptococcus pneumoniae is a major cause of respiratory infections in infants and the elderly worldwide. Many humans carry the bacterium in their throat, but remain asymptomatic due to activated innate immunity, however, inadequate immune responses in susceptible individuals can result in invasive pneumococcal pneumonia.
Researchers determined the capacity of flagellin to protect against pneumonia by intranasally inoculating two groups of mice with S. pneumoniae and simultaneously treating only one with flagellin. Mice treated with flagellin had a survival rate between 75 and 100% while untreated mice died within 3 to 4 days. Also, infected mice receiving flagellin treatment demonstrated significant bacterial reduction in the lungs after 24 hours and complete clearance after 2 days.
Additionally, researchers evaluated the therapeutic value of flagellin treatment by infecting two groups of mice with S. pneumoniae and then intranasally administering flagellin to only one after 24 hours. Protection levels among treated mice were 60 to 100 %, while all untreated mice died.
“Our results showed that local stimulation with a single and well-characterized molecule, specifically flagellin, is sufficient for augmenting lung innate immune defenses and controlling pneumococcal pneumonia, highlighting the benefits of using microbe-associated molecular patterns as the basis for developing antimicrobial therapies,” say the researchers.
(N. Munoz, L. Maele, J.M. Marques, A. Rial, J.C. Sirard, J.A. Chabalgoity. 2010. Mucosal administration of flagellin protects mice from Streptococcus pneumoniae lung infection. Infection and Immunity, 78. 10: 4226-4233.)