Immune Responses to Irradiated Pneumococcal Whole Cell Vaccine

Abstract

Streptococcus pneumoniae (pneumococcus) can cause respiratory and systemic diseases. Recently, γ-irradiation-inactivated, non-encapsulated, intranasal S. pneumoniae (r-SP) vaccine has been introduced as a novel serotype-independent and cost-effective vaccine. However, the immunogenic mechanism of r-SP is poorly understood. Here, we comparatively investigated the protective immunity and immunogenicity of r-SP to the heat-(h-SP) or formalin-inactivated vaccine (f-SP) without adjuvants. Mice were intranasally immunized with each vaccine three times and then challenged with a lethal dose of S. pneumoniae TIGR4 strain and then subsequently evaluated for their immune responses. Immunization with r-SP elicited modestly higher protection against S. pneumoniae than h-SP or f-SP. Immunization with r-SP enhanced pneumococcal-specific IgA in the nasal wash and IgG in bronchoalveolar lavage fluid. Immunization with r-SP enhanced S. pneumoniae-specific IgG, IgG1, and IgG2b in the serum. r-SP more potently induced the maturation of dendritic cells in the cervical lymph nodes than h-SP or f-SP. Interestingly, populations of follicular helper T cells and IL-4-producing cells were potently increased in cervical lymph nodes of r-SP-immunized mice. Collectively, r-SP could be an effective intranasal, inactivated whole-cell vaccine in that it elicits S. pneumoniae-specific antibody production and follicular helper T cell activation leading to protective immune responses against S. pneumoniae infection.

Gamma-Irradiated Non-Capsule Group B Streptococcus Promotes T-Cell Dependent Immunity and Provides a Cross-Protective Reaction

“…DC activation and antigen presentation following bacterial exposure are critical for eliciting adaptive immunity and initially activate T-cell dependent cytotoxic activity [ 54 ]. Previously, irradiated S. pneumoniae was found to upregulate DC expression of co-stimulatory molecules and MHC II in vitro, and the DCs effectively processed and presented exogenously administered antigens with BM-DCs compared to h-SP and f-SP [ 55 ]. In the present study, Rad-GBS significantly induced the maturation markers CD80 and MHCI in BM-DCs.…”