Objectives: To determine the ability of Arg and Lys- gingipains to cleave CD14, TLR2, and TLR4 expressed on macrophages.
Methods: Peritoneal macrophages from mice were exposed to Arg- (RgpA & RgpB) and Lys- (Kgp) gingipains. Detection of TLR2, TLR4 and CD14 was determined by flow cytometry.
Results: RgpA & Kgp decreased the detection of CD14 in a concentration (P=0.0000002) and time dependent manner (P=0.03), whereas RgpB didn't have a significant effect .The type of gingipain influenced the strength of CD14 cleavage with Kgp>>RgpA>>RgpB. CD14 Proteolysis with Kgp needed a shorter incubation time and a lower protease concentration than RgpA mediated proteolysis. Surprisingly, short-term exposure to RgpA and Kgp led to an increase in the detection of TLR4. Exposure to RgpB did not affect TLR4 detection, and none of the gingipains influenced detection of TLR2 on macrophages.
Conclusions: The gingipain hemaglutinin/adhesin site is important for CD14 cleavage since RgpB lacks this site and was unable to cleave CD14. Increased detection of TLR4 expression following exposure to RgpA and Kgp is transient and may be due to proteolysis of other cell surface components that hinder TLR4 detection. Longer exposure to the gingipains may lead to proteolysis of TLR4 itself. The fact that P. gingivalis selectively cleaves innate immune receptors suggests that the bacteria may influence the particular type of host response that develops. Further studies are needed to examine how gingipains may shape the host immune response to bacterial infection.