Vegetative forms of Clostridium chauvoei trigger apoptotic and inflammatory responses on macrophages

Elsevier

Available online 3 August 2022, 102616

AnaerobeHighlights•

The effect of 24 hpi with the vegetative form of C. chauvoei on Mϕs was studied.

After 24 hpi with an MOI of 20:1, Mϕs underwent apoptosis.

Concurrently with apoptosis, the infected Mϕs expressed iNOS and TNF-α.

Apoptosis of Mϕs can be an immune evasion mechanism used by C. chauvoei.

Our results suggest that the absence of phagocytic cells in tissues infected by C. chauvoei could be partly due to the induction of apoptosis, which could be considered as a mechanism of evasion of the immune response.

AbstractBackground

Clostridium chauvoei is a gram-positive, spore-forming, strictly anaerobic bacterium that causes blackleg, a disease that affects cattle by inducing fulminant myonecrosis, thereby leading to high and constant losses of cattle. Macrophages (Mɸs) are depleted in tissues infected with the vegetative form of C. chauvoei, but the mechanism remains partially known. Consequently, Mɸs may be a critical target in the pathogenicity of C. chauvoei.

Aim

The objective of this work was to study the mechanism of death of mouse-primary Mɸs infected in vitro for 24 h with the vegetative form of C. chauvoei.

Methods

Mouse peritoneal Mɸs were infected in vitro with different multiplicities of infection (MOIs) of C. chauvoei (i.e., 5:1, 20:1, and 100:1). After 24 h post-infection, cell viability (MTT reduction assay), apoptosis (apoptotic bodies, DNA ladder, and Annexin V assays), and inflammatory cell response (iNOS and TNF-α expression) were assessed.

Results

All the MOIs investigated decreased cell viability. An MOI of 20:1 caused the highest production of apoptotic bodies and an electrophoretic DNA-ladder pattern typical of an apoptosis cell death process. These results were corroborated using the Annexin V-flow cytometry assay. Concurrently with apoptotic cell death, Mϕs expressed iNOS and TNF-α.

Conclusion

Inflammation-mediated apoptosis of Mϕs can be a potential mechanism of evasion of the immune response used by C. chauvoei in tissues for depleting phagocytic cells at the site of infection.

Keywords

macrophage

Clostridium chauvoei

In vitro

Inflammation

Apoptosis

AbbreviationsiNOS

oxide nitric synthase

MOI

multiplicity of infection

MTT

(3- [4,5- dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide

TNFR

tumor necrosis factor receptor

TNF-α

tumor necrosis factor-alpha

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© 2022 Published by Elsevier Ltd.

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