Human Metapneumovirus Infection Predisposes Mice to Severe Pneumococcal Pneumonia

A new study suggests that prior infection with human metapneumovirus or influenza A virus predisposes mice to a severe secondary bacterial infection with pneumococcal pneumonia. The researchers from the Universitaire de Quebec and Laval University in  Quebec, Canada and Virion Systems, Inc. of Rockville, Md., report their findings in the February 2009 issue of the Journal of Virology.

A newly discovered member of the Paramyxoviridae family, human metapneumovirus (hMPV) has been associated with upper and lower respiratory tract symptoms such as common colds, bronchitis, and pneumonia. Previous studies suggest that hMPV infects virtually all individuals worldwide by the age of 5 resulting in a significant number of hospitalizations of young children. Research on co-infecting pathogens in hMPV-infected individuals has focused more exclusively on other viruses, however some instances of bacterial coinfections in hMPV infected individuals have been reported.

In the study researchers compared the response of mice initially infected with hMPV or influenza A virus followed by superinfection with Streptococcus pneumoniae five days later to mice infected with hMPV, influenza virus, or pneumococcus alone. Results showed that superinfected mice suffered significant weight loss and greater levels of airway obstruction than those mice only infected with hMPV, influenza, or pneumococcus. Bacterial counts increased in superinfected mice and higher rates of interstitial and alveolar inflammation were also observed.

"Prior infection with either hMPV or influenza A virus predisposes mice to severe pneumococcus infection," say the researchers. "Our results stress the importance of the conjugate pneumococcal vaccine in reducing the severity of hMPV and influenza virus infections by preventing pneumococcal superinfections."

Reference: I. Kukavica-Ibrulj, M.E. Hamelin, G.A. Prince, C. Gagnon, Y. Bergeron, M.G. Bergeron, G. Boivin. 2009. Infection with human metapneumovirus predisposes mice to severe pneumococcal pneumonia. Journal of Virology, 83. 3: 1341-1349.