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

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

Baseline characteristics of the BAL patients.

<p>Baseline characteristics of the BAL patients.</p

Production of extracellular traps is associated with ROS production and is inhibited by DNase.

<p>Panels A shows that neutrophils expressing NETs have a four-fold increase in ROS fluorescence compared to NET negative (-ve) cells (NET-ve 16 706 (5879–42 332), NET+ve 64 146 (44 738–122921)), (n = 7, p = 0·008). Panel B shows that macrophages expressing MET-like structures have a two-fold increase in ROS fluorescence compared to MET negative (-ve) cells (MET-ve 45 644 (6257–118907), MET+ve 93 636 (28 113–392 973)), (n = 8, p = 0·023). Panels C and D demonstrate inhibition of NET (NTHi 44 (24–53), NTHi &amp; DNase 3 (0–10)), (n = 6, p = 0·004) and MET-like structure (NTHi 19±5, NTHi &amp; DNase 0.1±0.1)), (n = 8, p = 0·008) formation by the addition of DNase.</p

Response by human bronchoalveolar macrophages to nontypeable <i>Haemophilus influenzae</i>.

<p>Panel A shows adherent BAL macrophages with staining for NTHi and production of ROS fluorescence in macrophages infected with NTHi by confocal microscopy. Panel B shows the ROS production in control (uninfected) macrophages and NTHi-infected macrophages over a 17 hour time-period (n = 15 subjects for each time-point) measured by confocal microscopy. At each one-hour time-point ROS production is significantly higher in the NTHi group (p&lt;0·01). Panel C shows the increase over 17 hours in ROS production (1 hour 13012±2214, 17 hours 15175±2247)), (n = 15, p = 0·009). Panel D shows upregulation of ROS as measured by the effect of three different strains of NTHi using chemiluminescence (control 5937 (1839–10855), NTHi-1 8193 (3569–15538), NTHi-2 8953 (5105–17111), NTHi-3 10093 (4136–20848)), (RLUs = reactive light units/second). The chemiluminescence predominantly measures extracellular ROS production. Panels E and F demonstrates an examples of the presence of high and low-producing ROS fluorescence populations in control (unstimulated) and NTHi-stimulated macrophages from a patient (using flow cytometry). The high-producing ROS populations have significantly increased surface expression of the M1 marker HLA-DR (p&lt;0·001): Panel G shows the unstimulated (baseline) macrophage population (low peak 6 (1–45), high peak 98 (94–99)), (n = 17), whilst Panel H shows the NTHi-stimulated macrophage population (low peak 11 (7–40), high peak 95 (80–100)), (n = 15).</p

Production of phagocyte extracellular traps and proteases in response to nontypeable <i>Haemophilus influenzae</i>.

<p>Panel A shows the % of neutrophils expressing neutrophil extracellular traps (NETs), (control 7 ±2, NTHi 40±6)), (n = 7, p = 0·002)) and Panel B shows the % of BAL macrophages expressing macrophage extracellular traps-like structures (METs), (control 0, NTHi 19±5), (n = 8, p = 0·008); after stimulation with NTHi compared to control. Panel C shows neutrophils producing NETs with co-expression of neutrophil elastase (arrow). Panel D shows macrophages producing a MET with co-expression of macrophage metalloproteinase-12 (arrow). Panel E shows that neutrophils (40±6, n = 7) have a higher expression of extracellular traps compared to macrophages (19±5, n = 8) (p = 0·013). Panel F; NTHi increases surface expression of MMP12 by BAL macrophages as measured by flow cytometry (control 804±78, NTHi 1075±142)), (n = 8, p = 0·005).</p