Oral immunization with Porphyromonas gingivalis outer membrane protein and CpG oligodeoxynucleotides attenuates P. gingivalis-accelerated atherosclerosis and inflammation

Anti-atherosclerotic vaccination against Porphyromonas gingivalis as a potential comparator of statin in mice

Background

Porphyromonas gingivalis (Pg) is an oral anaerobe which damages teeth and periodontal tissues. Its body infection is known to cause chronic inflammation, thereby inducing an early stage of atherosclerosis through humoral immune actions. Hence, vaccination by immunizing the proteins of P. gingivalis (Pg) post sonication with heating may prevent atherosclerosis. This study aimed to compare the effect of its vaccination with statin, which effectively prevents atherosclerosis by lowering lipids.

Methods

The vaccine was produced by sonicating P. gingivalis through heating, and a total of 32 male APOE-/-mice (8-week old) were subjected Western diet for 8 weeks, in order to induce atherosclerosis in a physiological manner. Then, the mice were grouped to undergo four treatment conditions (i.e., no treatment, pitavastatin, vaccine, or pitavastatin with vaccine). Vaccination was conducted through nasal immunization and confirmed by a Pg-specific humoral immune reaction. Then, half of the mice in each group were orally injected with P. gingivalis for the next 5 weeks while the other half remained uninfected, generating a total of eight groups (n = 4/group). The mice were sacrificed at 3 weeks after the last injection. After harvesting the aorta, Oil Red O staining of en face was conducted with imaging and image analysis, and plaque formation was quantitatively determined.

Results

Compared to no treatment, the vaccination through nasal immunization significantly reduced the atherosclerotic plaque sizes in APOE -/- mice under Western diet to the comparable level of statin group. When both vaccine and statin were used, no clear synergistic effect was observed as opposed to expectation.

Conclusions

This study revealed that nasal immunization of heat shock P. gingivalis has a significant impact on the prevention of arteriosclerosis and acts as a potential comparator of statin.