Infection of Lung Epithelial Cells with Pandemic 2009 A(H1N1) Influenza Viruses Reveals Isolate-Specific Differences in Infectivity and Host Cellular Responses

Abstract

To better understand the early virus-host interactions of the pandemic 2009 A(H1N1) viruses in humans, we examined early host responses following infection of human epithelial cell cultures with three 2009 A(H1N1) viruses (A/California/08/2009, A/Mexico/4108/2009, and A/Texas/15/2009), or a seasonal H1N1 vaccine strain (A/Solomon Islands/3/2006). We report here that infection with pandemic A/California/08/2009 and A/Mexico/4108/2009 viruses resulted in differences in virus infectivity compared to either pandemic A/Texas/15/2009 or the seasonal H1N1 vaccine strain. In addition, IFN-β levels were decreased in cell cultures infected with either the A/California/08/2009 or the A/Mexico/4108/2009 virus. Furthermore, infection with A/California/08/2009 and A/Mexico/4108/2009 viruses resulted in lower expression of four key proinflammatory markers (IL-6, RANTES, IP-10, and MIP-1β) compared with infection with either A/Texas/15/2009 or A/Solomon Islands/3/2006. Taken together, our results demonstrate that 2009 A(H1N1) viruses isolated during the Spring wave induced varying degrees of early host antiviral and inflammatory responses in human respiratory epithelial cells, highlighting the strain-specific nature of these responses, which play a role in clinical disease.

Early host response and immune signaling to 2009 pandemic influenza A (H1N1) viruses in primary cell culture models.

“…Using in vitro models that closely mimic physiological conditions within the lungs in evaluating respiratory infections is an important approach in elucidation of potential differences between strains with different virulence [321,322] H1N1pdm being more efficient [90]. Furthermore, a study comparing different H1N1pdm isolates in udNHBE cells show critical differences in levels of cytokines and chemokines elicited from cells infected with closely-related influenza isolates [91]. They show distinct differences in viral infectivity as well as differences in IFN levels between 2009 H1N1pdm (CA/08, Mexico/4108, TX/15) and the seasonal H1N1 (Solomon/03) [91].…”

“…Furthermore, a study comparing different H1N1pdm isolates in udNHBE cells show critical differences in levels of cytokines and chemokines elicited from cells infected with closely-related influenza isolates [91]. They show distinct differences in viral infectivity as well as differences in IFN levels between 2009 H1N1pdm (CA/08, Mexico/4108, TX/15) and the seasonal H1N1 (Solomon/03) [91]. The differences seen in these models, prompted us to compare the phenotype induced by our genetically, closely-related H1N1pdm and seasonal influenza isolates in wdNHBE cells.…”

“…Subsequent research showed the H1N1pdm has tropism for the upper and lower respiratory tract [74,349]. Histopathologic analysis of fatal cases of seasonal and pandemic influenza virus infection show a similar spectrum of pathologies [295,350], however, strains vary in their ability to infect and replicate in specific cell types (i.e., respiratory, alveolar, and lung endothelial cells) [66,86,91,[351][352][353]. Furthermore, different strains of IAV vary in their ability to infect and replicate productively in macrophages which also show differences in the magnitude of their pro-inflammatory responses [222,307,351,[354][355][356][357].…”

“…Hence, the spatial distribution and concentration of potential receptors associated within different areas of the respiratory tract and/or different cell types are integral in the study of IAV infection and disease [75,[88][89][90][91].…”

“…Seasonal IAV and H1N1pdm viruses enter and replicate efficiently into non-ciliated cells which are present in the epithelial cell layer in both the large and small airways of the lower respiratory tract, while H5N1 enters and replicates more efficiently in ciliated cells within the small airways [74,75,[83][84][85][86]. Hence, the spatial distribution and concentration of potential receptors associated within different areas of the respiratory tract and/or different cell types are integral in the study of IAV infection and disease [75,[88][89][90][91]. Further, while the lung epithelium is a primary target for infection [46], it is a highly complex environment composed of a heterogeneous cell population, including secretory (Clara), goblet (secretory/mucus), ciliated, and basal cells that differ in frequency and distribution depending on location in the lung [317].…”