Toward an Alum Free Mono-Component Monovalent Pertussis Vaccine: A CellMediated Immunity Assay

Background: Currently evidence indicates the resurgence of whooping cough despite high coverage of whole-cell (wP) and acellular (aP) pertussis vaccines. Objective: In this study, we investigated the cell-mediated immune response of a genetically inactivated protein containing the S1 subunit of pertussis toxin (PTS1) without and with the Listeriolysin O (LLO-PTS1), developed by the researchers (the authors of this study), in comparison with current wP and aP vaccines in the mice model. Methods: Thirty-six female NMRI mice aged 8 to 12 weeks (25 ± 5 g) were divided into six groups including control (n=6), and five treated groups (n=6/each). Treated groups comprising recombinant PTS1, recombinant fusion LLO-PTS1, aP, wP, and sham (phosphate-buffered saline) were injected intraperitoneally whereas the control group did not receive anything. After 60 days, the serum levels of IFN-γ, IL-4, and IL-17 cytokines (as the T-helper 1, 2, and 17 responses, respectively) were evaluated by mouse ELISA Kit. Results: Our findings showed LLO-PTS1 significantly increased IL-17 and IL-4 cytokines compared with wP and aP vaccines (superiority). IFN-γ failed to significantly increase in the LLO-PTS1 group compared to others but it was non-inferior to standard vaccines (non-inferiority). Conclusion: Our alum free mono-component monovalent recombinant fusion protein (LLOPTS1), registered as a patent in the www.iripo.ssaa.ir, could bear the capacity to stimulate the Th-1 response similar to wP and aP vaccines (non-inferiority) in the mice model. In addition, it showed better results in Th-17 and Th-2 response (superiority). This study can be regarded as a springboard for further probes in booster pertussis vaccine development.