Staphylococcus aureus Lipase 1 Enhances Influenza A Virus Replication.

Mariya I Goncheva,Bernadette M Dutia,Amy C Pickering,J Ross Fitzgerald,Andrew C Gill,Carina Conceicao,Hui-Min Lee,Saira Hussain,Ian Bennet,Fiona Sargison,Paul Digard,Stephen W Tuffs,Marlynne Quigg-Nicol

doi:10.1128/mbio.00975-20

Abstract

Influenza A virus (IAV) causes annual epidemics of respiratory disease in humans, often complicated by secondary coinfection with bacterial pathogens such as Staphylococcus aureus Here, we report that the S. aureus secreted protein lipase 1 enhances IAV replication in vitro in primary cells, including human lung fibroblasts. The proviral activity of lipase 1 is dependent on its enzymatic function, acts late in the viral life cycle, and results in increased infectivity through positive modulation of virus budding. Furthermore, the proviral effect of lipase 1 on IAV is exhibited during in vivo infection of embryonated hen's eggs and, importantly, increases the yield of a vaccine strain of IAV by approximately 5-fold. Thus, we have identified the first S. aureus protein to enhance IAV replication, suggesting a potential role in coinfection. Importantly, this activity may be harnessed to address global shortages of influenza vaccines.IMPORTANCE Influenza A virus (IAV) causes annual epidemics and sporadic pandemics of respiratory disease. Secondary bacterial coinfection by organisms such as Staphylococcus aureus is the most common complication of primary IAV infection and is associated with high levels of morbidity and mortality. Here, we report the first identified S. aureus factor (lipase 1) that enhances IAV replication during infection via positive modulation of virus budding. The effect is observed in vivo in embryonated hen's eggs and greatly enhances the yield of a vaccine strain, a finding that could be applied to address global shortages of influenza vaccines.

Highlights

Influenza A virus (IAV) causes annual epidemics of respiratory disease in humans, often complicated by secondary coinfection with bacterial pathogens such as Staphylococcus aureus
To investigate further the role of S. aureus proteases during influenza coinfection, we repeated the protocol employed by Tashiro et al and fractionated culture supernatants of S. aureus strains Wood 46 (Fig. 1A), USA300 LAC and a deletion mutant of USA300 LAC deficient in the production of all known secreted proteases [20] by size exclusion chromatography (SEC)
Aliquots of the resulting SEC fractions were added to primary chicken embryo fibroblast (CEF) cells infected with the H1N1 IAV strain A/Puerto Rico/8/34 (PR8) to test for their ability to support virus replication in the absence of exogenous trypsin

Summary

Introduction

Influenza A virus (IAV) causes annual epidemics of respiratory disease in humans, often complicated by secondary coinfection with bacterial pathogens such as Staphylococcus aureus. We have identified the first S. aureus protein to enhance IAV replication, suggesting a potential role in coinfection This activity may be harnessed to address global shortages of influenza vaccines. A common feature of all HA subtypes is that the molecule is synthesized as a precursor (HA0) that, after assembly into a trimer, must be proteolytically cleaved into HA1 and HA2 subunits to produce infectious virus particles [3] This cleavage step is achieved in cell culture by the addition of trypsin to the media, while secreted trypsin-like proteases of respiratory or mucosal epithelia perform this role in human seasonal IAV infections or low-pathogenicity avian influenza virus infections [4]. In the most recent pandemic of 2009, 25% to 40% of mortalities were attributed to bacterial coinfection, despite the widespread use of antibiotics [9, 10]

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