Streptococcus pneumoniae is an infectious pathogen mainly infecting host bodies through the respiratory system. An effective pneumococcal vaccine would be targeted to the mucosa and provide not only protection against invasive infection but also against colonization in the respiratory system. In the present work, we applied bacterium-like particles (BLPs) as an adjuvant for the development of a PspA mucosal vaccine, in which the PspA protein was displayed on the surface of BLPs. Intranasal immunization with the PspA-BLP pneumococcal vaccine, comprised of PspA2 from pneumococcal family 1 and PspA4 from pneumococcal family 2, not only induced a high level of serum IgG antibodies but also a high level of mucosal SIgA antibodies. Analysis of binding of serum antibodies to intact bacteria showed a broad coverage of binding to pneumococcal strains expressing PspA from clade 1 to 5. Immunization with the PspA-BLP vaccine conferred protection against fatal intranasal challenge with both PspA family 1 and family 2 pneumococcal strains regardless of serotype. Therefore, the PspA-BLP pneumococcal vaccine was demonstrated to be a promising strategy for mucosal immunization to enhance both systemic and mucosal immune responses.

Essen regimen, the Thai Red Cross two-site ID regimen, Zagreb schedule, and the eight-site ID regimen are the standard rabies vaccines recommended by the World Health Organization (WHO). In this study, a liposomal rabies vaccine (LipoRV) was developed, which was found to facilitate the production of rabies virus neutralizing antibody (RVNA) in BALB/c mice. Liposome solution was prepared with hydrogenated soya phosphatide and cholesterol. LipoRV composed of liposome solution and inactivated rabies vaccine (IRV). The immune responses were compared between the mice treated with either LipoRV or IRV. Higher levels of interleukin-2 (p < 0.05), interferon-γ (p < 0.01), and natural killer cell activity (p < 0.05) were observed in the mice immunized with LipoRV than those with IRV. The potency of LipoRV was significantly higher than that IRV (p < 0.05). In addition, three injections of LipoRV on days 0, 3, and 14 could elicit similar RVNA levels as the five shots of IRV. Our data also showed a higher survival rate in mice treated with three shots of LipoRV (56.2%) than five shots of IRV (40.6%). In conclusion, liposome enhances the immune response of mice to rabies vaccine and could be applied as a potential immunopotentiator.