The differentiated airway epithelium infected by influenza viruses maintains the barrier function despite a dramatic loss of ciliated cells

Abstract

Virus-host interactions in the respiratory epithelium during long term influenza virus infection are not well characterized. Therefore, we developed an air-liquid interface culture system for differentiated porcine respiratory epithelial cells to study the effect of virus-induced cellular damage. In our well-differentiated cells, α2,6-linked sialic acid is predominantly expressed on the apical surface and the basal cells mainly express α2,3-linked sialic acid. During the whole infection period, release of infectious virus was maintained at a high titre for more than seven days. The infected epithelial cells were subject to apoptosis resulting in the loss of ciliated cells together with a thinner thickness. Nevertheless, the airway epithelium maintained trans-epithelial electrical resistance and retained its barrier function. The loss of ciliated cells was compensated by the cells which contained the KRT5 basal cell marker but were not yet differentiated into ciliated cells. These specialized cells showed an increase of α2,3-linked sialic acid on the apical surface. In sum, our results help to explain the localized infection of the airway epithelium by influenza viruses. The impairment of mucociliary clearance in the epithelial cells provides an explanation why prior viral infection renders the host more susceptible to secondary co-infection by another pathogen.

Viral Coinfection Replaces Effects of Suilysin on Streptococcus suis Adherence to and Invasion of Respiratory Epithelial Cells Grown under Air-Liquid Interface Conditions

“…This effect of an influenza virus infection on differentiated airway epithelial cells has been reported recently (33) and is more pronounced at later times after SIV infection (7 days postinfection [dpi]). This may be explained by the loss of infected ciliated cells due to apoptosis (33). To compensate for the loss of cells, basal cells start to differentiate into specialized cells.…”

“…As there is no culture medium in the apical compartment of the ALI culture system used in our study, the proliferation of streptococci relies on the metabolism of nutrients provided by the epithelial cells (26). As influenza viruses are able to induce apoptosis (33), it is conceivable that potential nutrients are released from dying cells (41) and might be utilized by S. suis. However, the virus-dependent cytotoxicity was observed only late in infection; therefore, this possibility appears to be less likely, as far as coinfection by influenza viruses and suilysin-negative S. suis bacteria is concerned.…”

“…If any of these cell types are injured, this will impair the mucociliary clearance function, which may facilitate infection by pathogens. The apoptotic effect of influenza A virus infections results in the loss of ciliated cells (33,38). As a consequence, in the areas of infection, the mucociliary clearance function is impaired until the loss is compensated for by basal cells that differentiate into specialized cells (39).…”

Propagation of respiratory viruses in human airway epithelia reveals persistent virus-specific signatures

“…5 Different strains of influenza (H3N2, H1N1, or influenza B) are also known to affect tissue integrity, cilia beating, and MCC in mice, rats, pigs, and human subjects. [47][48][49][50] In addition, we observed similar induction of LDH release and blockage of MCC with an H1N1 clinical isolate (data not shown). The mechanisms used by EV-D68 and influenza to destroy ciliated cells might differ.…”

Comparison of mono- and co-infection by swine influenza A viruses and porcine respiratory coronavirus in porcine precision-cut lung slices

“…Lung slices have been used in scientific studies from a variety of animals like rodents, caprine or bovine lung or even human lung (Abdull Razis et al, 2011;Banerjee et al, 2012;Braun and Tschernig, 2006;Goris et al, 2009;Kirchhoff et al, 2014a;Kirchhoff et al, 2014b). However, although porcine PCLS have been analyzed in the context of influenza A virus infection and co-infection with bacteria, the co-infection with coronaviruses remains to be investigated (Meng et al, 2013;Punyadarsaniya et al, 2011;Wu et al, 2016). Porcine lung slices are easy to produce and reproduce under stable conditions, while mimicking respiratory infection.…”