Mr. Ketterer et al., Infection of primary human bronchial epithelial cells by Haemophilus influenzae: Macropinocytosis as a mechanism of airway epithelial cell entry, INFEC IMMUN, 67(8), 1999, pp. 4161-4170
Nontypeable Haemophilus influenzae is an exclusive human pathogen which inf
ects the respiratory epithelium. We have initiated studies to explore the i
nteraction of the nontypeable H. influenzae strain 2019 with primary human
airway epithelial cells by electron and confocal microscopy, Primary human
airway cell cultures were established as monolayers on glass collagen-coate
d coverslips or on semipermeable membranes at an air-fluid interface, Scann
ing electron microscopy indicated that bacteria adhered to nonciliated cell
s in the population. The surface of infected cells showed evidence of cytos
keletal rearrangements manifested by microvilli and lamellipodia extending
toward and engaging bacteria. Confocal microscopic analysis demonstrated th
at infection induced actin polymerization with an increase in cortical acti
n as well as evidence of actin strands around the bacteria. Transmission el
ectron microscopic analysis showed lamellipodia and microvilli surrounding
organisms, as well as organisms adherent to the cell surface. These studies
also demonstrated the presence of bacteria within vacuoles inside of airwa
y cells. Confocal microscopic studies with Texas red-labeled dextran (molec
ular weight, 70,000) indicated that H. influenzae cells were entering cells
by the process of macropinocytosis. These studies indicate that nontypeabl
e H. influenzae can initiate cytoskeletal rearrangement within human airway
epithelium, resulting in internalization of the bacteria within nonciliate
d human airway epithelial cells by the process of macropinocytosis.