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Journal of Immunology Research
Volume 2015, Article ID 706376, 14 pages
http://dx.doi.org/10.1155/2015/706376
Review Article

The Lung Immune Response to Nontypeable Haemophilus influenzae (Lung Immunity to NTHi)

1Monash Lung and Sleep, Monash Medical Centre, Melbourne, VIC 3168, Australia
2Monash University Department of Medicine, Monash Medical Centre, Melbourne, VIC 3168, Australia

Received 19 March 2015; Revised 12 May 2015; Accepted 13 May 2015

Academic Editor: Mahboobeh Mahdavinia

Copyright © 2015 Paul T. King and Roleen Sharma. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Haemophilus influenzae is divided into typeable or nontypeable strains based on the presence or absence of a polysaccharide capsule. The typeable strains (such as type b) are an important cause of systemic infection, whilst the nontypeable strains (designated as NTHi) are predominantly respiratory mucosal pathogens. NTHi is present as part of the normal microbiome in the nasopharynx, from where it may spread down to the lower respiratory tract. In this context it is no longer a commensal and becomes an important respiratory pathogen associated with a range of common conditions including bronchitis, bronchiectasis, pneumonia, and particularly chronic obstructive pulmonary disease. NTHi induces a strong inflammatory response in the respiratory tract with activation of immune responses, which often fail to clear the bacteria from the lung. This results in recurrent/persistent infection and chronic inflammation with consequent lung pathology. This review will summarise the current literature about the lung immune response to nontypeable Haemophilus influenzae, a topic that has important implications for patient management.