Evaluation of pro-inflammatory activity and immunogenicity of an inactivated SBA-15 silica vaccine against Mycoplasma hyopneumoniae in piglets

Mycoplasma (M.) hyopneumoniae, the agent of porcine enzootic pneumonia (PEP), a primary pathogen of porcine respiratory disease complex (PRDC), reduces productivity and increases economic losses in swine production, with vaccination being the most important method to control the disease in the producing farms. This study evaluates the pro-inflammatory activity and immunogenicity of an inactivated vaccine for M. hyopneumoniae using an SBA-15 silica-based adjuvant in piglets. Forty-eight weaned piglets were divided into four groups (n = 12/group): a commercial vaccine group (CV); an SBA-15 adjuvanted vaccine group (SBA-15-Vac); a control group, receiving a suspension of SBA-15 with PBS, without the antigen (SBA-15-Cont), and a group that received saline solution (NV). SBA-15-Cont group served as a control for adjuvant-related effects, while the NV group served as negative control for lung lesion analysis, only. All animals were challenged, 21 days post vaccination, with M. hyopneumoniae strain 232. The evaluation of clinical signs was performed, and the inflammatory response was evaluated by measuring acute-phase proteins, as well as anti-M. hyopneumoniae IgG and IgA antibody levels. The SBA-15 adjuvant control group demonstrated mild inflammatory responses maintaining stable transferrin and haptoglobin levels after vaccination, suggesting a controlled inflammatory response compared to the commercial vaccine. The SBA-15 group exhibited a delayed but sustained immune response, suggesting a possible depot effect. Acute-phase protein levels, particularly ceruloplasmin and haptoglobin. Our findings support the potential of SBA-15 as a safe and effective adjuvant and highlight that SBA-15 silica nanoparticles are a promising and safe adjuvant in swine vaccines against M. hyopneumoniae.