Sumario: |
Actinobacillus pleuropneumoniae (A.pp, Gram negative) and Streptococcus (S.) suis (Gram
positive) can cause severe diseases in pigs. During infection, neutrophils infiltrate to counteract
these pathogens with phagocytosis and/or neutrophil extracellular traps (NETs). NETs consist of a
DNA-backbone spiked with antimicrobial components. The NET formation mechanisms in porcine
neutrophils as a response to both of the pathogens are not entirely clear. The aim of this study was
to investigate whether A.pp (serotype 2, C3656/0271/11) and S. suis (serotype 2, strain 10) induce
NETs by NADPH oxidase- or CD18-dependent mechanisms and to characterize phenotypes of NETs
in porcine neutrophils. Therefore, we investigated NET induction in porcine neutrophils in the
presence and absence of NET inhibitors and quantified NETs after 3 h. Furthermore, NETosis and
phagocytosis were investigated by transmission electron microscopy after 30 min to characterize
different phenotypes. A.pp and S. suis induce NETs that are mainly ROS-dependent. A.pp induces
NETs that are partially CD18-dependent. Thirty minutes after infection, both of the pathogens
induced a vesicular NET formation with only slight differences. Interestingly, some neutrophils
showed only NET-marker positive phagolysosomes, but no NET-marker positive vesicles. Other
neutrophils showed vesicular NETs and only NET-marker negative phagolysosomes. In conclusion,
both of the pathogens induce ROS-dependent NETs. Vesicular NETosis and phagocytosis occur in
parallel in porcine neutrophils in response to S. suis serotype 2 and A.pp serotype 2.
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