The autophagic response toStaphylococcus aureusprovides an intracellular niche in neutrophils

Abstract

Staphylococcus aureus is a major human pathogen causing multiple pathologies, from cutaneous lesions to life-threatening sepsis. Although neutrophils contribute to immunity against S. aureus, multiple lines of evidence suggest that these phagocytes can provide an intracellular niche for staphylococcal dissemination. However, the mechanism of neutrophil subversion by intracellular S. aureus remains unknown. Targeting of intracellular pathogens by autophagy is recognised as an important component of host innate immunity, but whether autophagy is beneficial or detrimental to S. aureus-infected hosts remains controversial. Here, using larval zebrafish we show that S. aureus is rapidly decorated by the autophagy marker Lc3 following engulfment by macrophages and neutrophils. Upon phagocytosis by neutrophils, Lc3-positive, non-acidified spacious phagosomes are formed. This response is dependent on phagocyte NADPH oxidase as both cyba knockdown and diphenyleneiodonium (DPI) treatment inhibited Lc3 decoration of phagosomes. Importantly, NADPH oxidase inhibition diverted neutrophil S. aureus processing into tight acidified vesicles, which resulted in increased host resistance to the infection. Some intracellular bacteria within neutrophils were also tagged by p62-GFP fusion protein and loss of p62 impaired host defence. Taken together, we have shown that intracellular handling of S. aureus by neutrophils is best explained by Lc3-associated phagocytosis (LAP), which appears to provide an intracellular niche for bacterial pathogenesis, while the selective autophagy receptor p62 is host-protective. The antagonistic roles of LAP and p62-mediated pathways in S. aureus-infected neutrophils may explain the conflicting reports relating to antistaphylococcal autophagy and provide new insights for therapeutic strategies against antimicrobial resistant staphylococci.

Phagosomal Acidification Is Required to Kill Streptococcus pneumoniae in a Zebrafish Model

“…For these experiments, the transgenic larvae Tg(fms: GFP)sh377 [34] were infected with D39ΔcpsGFP which were prestained with the pH-sensitive dye pHrodo Red [35], which creates a higher fluorescence intensity at lower pH. We found that bacteria internalised by macrophages were acidified in control larvae and this acidification was inhibited by bafilomycin A1 in the medium (Figures 4(a)-4(c)).…”

The Case for Modeling Human Infection in Zebrafish

“…Furthermore, association with LC3 is independent of ATG13, but is dependent on Rubicon and NADPH, which suggests that S. Typhimurium replication in macrophages is restricted by LC3-associated phagocytosis (LAP) [49]. For S. aureus infection, p62-mediated autophagy and LAP have opposing roles in neutrophils [50,51] because p62-selective autophagy promotes bacterial clearance, whereas LAP helps bacteria to establish an intracellular niche.…”

Eliminating the invading extracellular and intracellular FnBp+ bacteria from respiratory epithelial cells by autophagy mediated through FnBp-Fn-Integrin α5β1 axis

“…However, some pathogens have evolved survival strategies in their favor, using autophagy for intracellular reproduction. This process has been achieved through LAP (Prajsnar et al, 2021). Therefore, we explored the exact mechanism of mutual recognition and induction of autophagy between pathogen and host cells, in which host cells can survive but bacteria cannot.…”

“…Some studies have reported on the relationship between the two and autophagy. Tomasz K. et al found that autophagy can provide an intracellular replication niche for S. aureus within neutrophils (Prajsnar et al, 2021). Meanwhile, Josie F. et al, in the same lab, found that the selective autophagy receptor Sqstm1/p62 in neutrophils could target and degrade S. aureus intracellularly (Gibson et al, 2021).…”

“…During this process, bacteria, in particular intracellular pathogens, can be engulfed directly into the cytoplasm by a bilayer membrane vesicle called autophagosome which then fuses with the lysosome for degradation. Alternately, bacteria can be surrounded by a monolayer membrane structure called LC3associated phagosome (LAP) (Gibson et al, 2021;Prajsnar et al, 2021). Related literature points out xenophagy is an important intracellular innate immune protective mechanism (Neumann et al, 2016;Kemper and Hensel, 2023).…”