In-vivo Immune Analysis of Capsular Type Ia Antigen of Streptococcus Agalactiae Encapsulated with PLGA

Background: Streptococcus agalactiae (S. agalactiae) due to the polysaccharide capsule and causing invasive infections, bacteremia, pneumonia, and meningitis in neonatal with 5% mortality considered the most critical pathogen. In order to increase the immunity level by the capsular type Ia antigen of S. agalactiae, conjugated polydlyl lactide-co-glycolide nanoparticles (PLGA_NP), we proposed a more effective vaccine against infections caused by S. agalactiae. In addition, the cytotoxicity of the NPs as a carrier in the fabrication of the nano-vaccine in the animal model of rats was investigated. Materials & methods: Isolation of capsules from S. agalactiae, and preparation of PLGA nanoparticles containing type Ia capsules done. After conjugating the PLGA_NP with type Ia capsules, it was characterized using spectroscopy techniques. Rat vaccination and immunization process, rat survival model, spleen culture method on rats and neonatal rats, and opsonophagocytosis test were performed. Results: The zeta potential of PLGA_NP was -19 mv, and for the conjugated capsule (CPS)-PLGA was -10.34 mv. The size of PLGA-CPS is 256.5 nm. The mean of the pathogenic strain of S. agalactiaeafter exposure to the immune system of the CPS-PLGA group was lower than in other experimental groups. Reduced growth of S. agalactiae colonies in the vaccine candidate group compared to the other groups reported (p < 0.05), and in rat opsonophagocytosis test, the CPS-PLGA vaccine candidate group has the lowest growth value in the percentage of grown colonies compared to other tested groups (p < 0.05). Conclusion: It can be concluded that the potential performance of the CPS-PLGA vaccine candidate group is ineffective stimulation and enhancement of infection for diagnosis. On the other hand, according to data analysis, this vaccine group has a significant difference from other vaccine groups (p < 0.05). The prepared antigen can be used as a candidate vaccine to treat congenital infections and premature invasive neonatal infections in the animal model of rats due to its high efficacy in infection.