Abstract
Background:
Pseudomonas aeruginosa is considered one of the major opportunistic bacteria that cause infections in both animals and humans. It is a significant problem in global health care due to its high inherent resistance to numerous antibiotics. Pathologic microorganisms are resistant to the number of available treatments, highlighting the pressing need for efficient immunization and immunotherapeutic approaches.

Aim:
Data regarding the use of nanoparticles as delivery are limited; therefore, we sought to develop an adjuvant vaccine to lessen the chance of developing a P. aeruginosa infection.

Methods:
Thirty mice were randomly assigned to three groups: T1 (Naïve control), T2 (non-nave control), and T3 (non-nave control) received two intraperitoneal (IP) doses (2-week interval) of 0.5 mg/mL of killed whole sonicated P. aeruginosa antigens (KWSPAgs) and two (IP) doses (2-week interval) of 1 mg/mL of KWSPAgs and aluminum oxide nanoparticles. At 14 days post-immunization, cell-mediated immunity was evaluated by delayed-type hypersensitivity, and at day 28, humoral immunity was assessed via ELISA to measure serum levels of IgG, TLR2, and IL-2. All groups were challenged (IP) with P. aeruginosa (0.2 × 10⁷ CFU/mL). After 14 days post-immunization, mice were sacrificed for bacterial isolation, and internal organs were collected for histopathological and immunohistochemical analysis.

Results:
P. aeruginosa antigens were sufficient to elicit immunogenicity. Moreover, the use of NPs markedly enhanced immunogenicity through the delivery of KWSPAgs. Our results have shown that group with NP with KWSPAgs were able to induce inflammation and cellular immunity by increasing IL2 and foot pad thickness, both of which are indicators of T lymphocyte proliferation. In addition, our data indicated that group with NP were able to induce humoral immunity by increasing the IgG and TLR2 levels in the immunized groups compared with Naïve control. The histopathological lesions and immune-positive cells in the infected and non-infected groups were different. Lesions were significantly higher in the infected group than in the noninfected control group at the observed time points.

Conclusion:
Overall, these findings highlight that NPs are a good activator for inducing cellular and humoral immunity, enhancing the delivery of future vaccine designs and/or target therapies against P. aeruginosa.

Key words: Aluminum oxide; Bacterial vaccine; Immune responses; Immunohistochemistry; Phonological changes.