An overview of the P. aeruginosa “killed but metabolically
active” T3SS-based vaccination. (a) The P. aeruginosa strain
is cultivated under T3SS-inducing conditions. The protein used for vaccination is
overexpressed by bacteria before bacterial inactivation with PCT in the presence of
amotosalen. Then, P. aeruginosa is injected subcutaneously (s.c.), and its
active T3SS allows protein injection into the host cells. (b) Colony-forming
units (CFU) of OST and OSTAB after treatment with increasing amotosalen concentration.
The mean of five experiments (performed in duplicate) is represented. (c)
Analysis of the membrane integrity of the P. aeruginosa OSTAB strain with the
Live/Dead BacLight bacterial viability kit (Invitrogen). OSTAB (live), heat-killed (HK),
or photochemically treated P. aeruginosa in presence of 0–15 µmol/l
amotosalen concentrations. (d) Western blot analysis of the protein S54-OVA in
the supernatant of cultivated OSTAB S54-OVA strain with or without EGTA (i.e.,
closed or opened syringe), after PCT and in the presence of various amotosalen
concentrations. IPTG was added for 3 hours after PCT. Representative blot of three
experiments. EGTA, ethylene glycol tetraacetic acid; IPTG, isopropyl
β-D-1-thiogalactopyranoside; PCT, photochemical treatment.