The SspA subtilisin-like protease of Streptococcus suis triggers a pro-inflammatory response in macrophages through a non-proteolytic mechanism

Table 1 Effect of heat treatment or the presence of polymyxin B on cytokine secretion by PMA-differentiated U937 macrophages stimulated with the recombinant SspA (33 μg/ml) of S. suis.

Conditions	Amount secreted (pg/ml)
	CCL5	IL-6	CXCL8
Control (no stimulation)	2081 ± 14	100 ± 1	3170 ± 9
Recombinant SspA of S. suis	2370 ± 61*	1922 ± 31*	108557 ± 620*
Heat-inactivated recombinant SspA of S. suis	72409 ± 848*	2111 ± 71*	102287 ± 1062*
Recombinant SspA of S. suis + polymyxin B	2081 ± 32	2099 ± 254*	107446 ± 590*

The data are the means ± SD of triplicate assays for three separate experiments. Asterisks indicate a significant difference in comparison with the unstimulated control at P < 0.01.

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