FIG 3 .

Inhibition of IFN-β by H. pylori is independent of viability and the virulence factor CagPAI but dependent on the toxin VacA. (A) BMDMs were stimulated with L. acidophilus NCFM, H. pylori 251, or the H. pylori 251 CagPAI mutant alone or prestimulated with L. acidophilus NCFM (L. acid.) for 1 h prior to addition of H. pylori strains. RNA was extracted after 4 h, cDNA was synthesized, and the expression of Ifn-β was measured by RT-PCR (L. acidophilus NCFM plus H. pylori 251 or plus the H. pylori 251 CagPAI mutant versus L. acidophilus NCFM alone; *, P < 0.01). (B) BMDMs were prestimulated with L. acidophilus NCFM for 1 h prior to addition of heat-killed (HK) H. pylori 251 and heat-killed H. pylori 251 CagPAI mutant. IFN-β was measured in the supernatants 10 h after stimulation by ELISA (L. acidophilus NCFM [L. acidoph.] plus HK H. pylori 251 or plus the H. pylori 251 CagPAI mutant versus L. acidophilus NCFM alone; *, P < 0.01). (C) BMDMs were prestimulated with L. acidophilus NCFM for 1 h prior to addition of H. pylori 251 or the H. pylori 251 vacA mutant. RNA was extracted after 4 h, cDNA was synthesized, and the expression of Ifn-β was measured by RT-PCR (L. acidophilus NCFM plus the H. pylori 251 vacA mutant versus L. acidophilus NCFM alone; *, P < 0.01). (D) BMDMs were preincubated for 30 min with the endosomal acidification blockers chloroquine (CQ) (final concentration, 20 µM) and bafilomycin A1 (Baf A1) (final concentration, 25 µM) prior to stimulation with L. acidophilus NCFM. IFN-β was measured in the supernatants 10 h after stimulation by ELISA (L. acidophilus NCFM plus inhibitors versus L. acidophilus NCFM alone; *, P < 0.01). Represented are the means ± SEM for triplicate macrophage cultures, which are representative of three independent experiments.