Various strategies adapted to develop an efficient vaccine against foodborne pathogen, Listeria monocytogenes, have met with little success. Spheroplasts (bacterial cell devoid of cell wall) are likely to undergo membrane-membrane fusion, leading to the delivery of their content to the cytosol of antigen-presenting cells, thus facilitating MHC class I antigen processing and presentation. In this study, we evaluated the prophylactic potential of Listeria spheroplast-based vaccine against experimental murine listeriosis in comparison with heat-killed Listeria (HKL) and archaeosome-entrapped Listeria whole-cell protein (LWCP). Compared with HKL, the spheroplast-based vaccine was found to evoke better Th1 response as exhibited by the presence of type 1 cytokines in the host (interferon-γ and IL-12) and a high IgG2a /IgG1 ratio. Robust lympho-proliferative efficacy was apparent in both spheroplast-immunized and archaeosome-entrapped LWCP-immunized groups. The upregulation of costimulatory and effector memory markers upon immunization with spheroplasts was found to be at par with that evoked by archaeosome-entrapped LWCP-immunized group. Central memory response in gated CD8(+) T cell was much higher in spheroplast-immunized animals when compared with archaeosome-entrapped LWCP group. The data presented here clearly demonstrate that spheroplasts evoked a robust immune response and offer better prophylactic potential against L. monocytogenes.
© 2015 John Wiley & Sons Ltd.