Toward an Alum Free Mono-Component Monovalent Pertussis Vaccine: A Cytokine Response Assay.

Background: Current evidence indicates the resurgence of whooping cough despite high coverage of whole-cell (wP) and acellular (aP) pertussis vaccines.

Objective: To investigate the cytokine response to a genetically inactivated protein containing the S1 subunit of pertussis toxin (PTS1) with and without the Listeriolysin O (LLO-PTS1), 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 received intraperitoneal injection of recombinant PTS1, recombinant fusion LLO-PTS1, aP, wP, and sham (phosphate-buffered saline), whereas the control group did not receive anything. After 60 days, the serum levels of IFN-γ, IL-4, and IL-17 cytokines were evaluated by ELISA method.

Results: Our findings showed LLO-PTS1 significantly increased IL-17 and IL-4 cytokines compared with wP and aP vaccines. IFN-γ failed to increase substantially in the LLO-PTS1 group compared to others, but it was non-inferior to standard vaccines.

Conclusion: Our alum free mono-component monovalent recombinant fusion protein (LLO-PTS1) could bear the capacity to stimulate the release of IFN-γ similar to wP and aP vaccines in the mouse model. Besides, it showed better results in stimulating the release of IL-17 and IL-4 response. This study can be regarded as a platform for further probes in booster pertussis vaccine development.