Enhanced Systemic and Mucosal Immune Responses to Haemophilus parasuis by Intranasal Administration of Lactic-Co-Glycolic Acid Microspheres

Swine Glasser's disease, instigated by <i>Haemophilus parasuis</i> (<i>H. parasuis</i>), is a significant bacterial infection that causes substantial economic losses in pig farming operations. The role of mucosal immunity is pivotal in defending against <i>H. parasuis</i>. This study focused on the construction of PLGA microspheres that encapsulate the outer membrane protein OMP16 from <i>H. parasuis</i> (PLGA-OMP16) and evaluated their immunological effectiveness in a mouse model. After being intranasally immunized twice, the PLGA-OMP16 microspheres effectively induced IgAs in saliva and nasal and lung fluids. The PLGA-OMP16 microspheres also significantly increased the number of anti <i>H. parasuis</i> IgGs in serum. Furthermore, the PLGA-OMP16 microspheres triggered elevated levels of IL-2, IL-4, and IFN-γ. The mice vaccinated with PLGA-OMP16 showed a significant reduction in <i>H. parasuis</i> burden in the spleen and lungs following bacterial challenge. These results indicate that intranasal immunization using PLGA microspheres is a promising adjuvant delivery system for vaccines targeting <i>H. parasuis</i>.