Nano selenium-enriched probiotic Lactobacillus enhances alum adjuvanticity and promotes antigen-specific systemic and mucosal immunity

Proof of concept in utilizing the peptidoglycan skeleton of pathogenic bacteria as antigen delivery platform for enhanced immune response

Subunit vaccines are becoming increasingly important because of their safety and effectiveness. However, subunit vaccines often exhibit limited immunogenicity, necessitating the use of suitable adjuvants to elicit robust immune responses. In this study, we demonstrated for the first time that pathogenic bacteria can be prepared into a purified peptidoglycan skeleton without nucleic acids and proteins, presenting bacterium-like particles (pBLP). Our results showed that the peptidoglycan skeletons screened from four pathogens could activate Toll-like receptor1/2 receptors better than bacterium-like particles from Lactococcus lactis in macrophages. We observed that pBLP was safe in mouse models of multiple ages. Furthermore, pBLP improved the performance of two commercial vaccines in vivo. We confirmed that pBLP successfully loaded antigens onto the surface and proved to be an effective antigen delivery platform with enhanced antibody titers, antibody avidity, balanced subclass distribution, and mucosal immunity. These results indicate that the peptidoglycan skeleton of pathogenic bacteria represents a new strategy for developing subunit vaccine delivery systems.

Antimicrobial and antibiofilm properties of selenium-chitosan-loaded salicylic acid nanoparticles for the removal of emerging contaminants from bacterial pathogens

In this study salicylic acid loaded containing selenium nanoparticles was synthesized and called SA@CS-Se NPs. the chitosan was used as a natural stabilizer during the synthesis process. Fourier transforms infrared spectroscopy (FTIR), Powder X-ray diffraction (XRD), field emission electron microscopy (FESEM), and transmission electron microscopy (TEM) were used to describe the physicochemical characteristics of the SA@CS-Se NPs. The PXRD examination revealed that the grain size was around 31.9 nm. TEM and FESEM techniques showed the spherical shape of SA@CS-Se NPs. Additionally, the analysis of experiments showed that SA@CS-Se NPs have antibacterial properties against 4 ATCC bacteria; So that with concentrations of 75, 125, 150, and 100 µg/ml, it inhibited the biofilm formation of Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, and Staphylococcus aureus respectively. Also, at the concentration of 300 µg/ml, it removed 22.76, 23.2, 10.62, and 18.08% biofilm caused by E. coli, P. aeruginosa, B. subtilis, and S. aureus respectively. The synthesized SA@CS-Se NPs may find an application to reduce the unsafe influence of pathogenic microbes and, hence, eliminate microbial contamination.

Biogenic Selenium Nanoparticles Synthesized by L. brevis 23017 Enhance Aluminum Adjuvanticity and Make Up for its Disadvantage in Mice

The most popular vaccine adjuvants are aluminum ones, which have significantly reduced the incidence and mortality of many diseases. However, aluminum-adjuvanted vaccines are constrained by their limited capacity to elicit cellular and mucosal immune responses, thus constraining their broader utilization. Biogenic selenium nanoparticles are a low-cost, environmentally friendly, low-toxicity, and highly bioactive form of selenium supplementation. Here, we purified selenium nanoparticles synthesized by Levilactobacillus brevis 23017 (L-SeNP) and characterized them using Fourier-transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, scanning electron microscopy, and transmission electron microscopy. The results indicate that the L-SeNP has a particle size ranging from 30 to 200 nm and is coated with proteins and polysaccharides. Subsequently, we assessed the immune-enhancing properties of L-SeNP in combination with an adjuvant-inactivated Clostridium perfringens type A vaccine using a mouse model. The findings demonstrate that L-SeNP can elevate the IgG and SIgA titers in immunized mice and modulate the Th1/Th2 immune response, thereby enhancing the protective effect of aluminum-adjuvanted vaccines. Furthermore, we observed that L-SeNP increases selenoprotein expression and regulates oxidative stress in immunized mice, which may be how L-SeNP regulates immunity. In conclusion, L-SeNP has the potential to augment the immune response of aluminum adjuvant vaccines and compensate for their limitations in eliciting Th1 and mucosal immune responses.