Intranasal immunization with outer membrane vesicles (OMV) protects against airway colonization and systemic infection with Acinetobacter baumannii

Preparation, Optimization, and Anti-Pulmonary Infection Activity of Casein-Based Chrysin Nanoparticles

Introduction

Chrysin has a wide range of biological activities, but its poor bioavailability greatly limits its use. Here, we attempted to prepare casein (cas)-based nanoparticles to promote the biotransfer of chrysin, which demonstrated better bioavailability and anti-infection activity compared to free chrysin.

Methods

Cas-based chrysin nanoparticles were prepared and characterized, and most of the preparation process was optimized. Then, the in vitro and in vivo release characteristics were studied, and anti-pulmonary infection activity was evaluated.

Results

The constructed chrysin-cas nanoparticles exhibited nearly spherical morphology with particle size and ζ potential of 225.3 nm and -33 mV, respectively. These nanoparticles showed high encapsulation efficiency and drug-loading capacity of 79.84% ± 1.81% and 11.56% ± 0.28%, respectively. In vitro release studies highlighted a significant improvement in the release profile of the chrysin-cas nanoparticles (CCPs). In vivo experiments revealed that the relative oral bioavailability of CCPs was approximately 2.01 times higher than that of the free chrysin suspension. Further investigations indicated that CCPs effectively attenuated pulmonary infections caused by Acinetobacter baumannii by mitigating oxidative stress and reducing pro-inflammatory cytokines levels, and the efficacy was better than that of the free chrysin suspension.

Conclusion

The findings underscore the advantageous bioavailability of CCPs and their protective effects against pulmonary infections. Such advancements position CCPs as a promising pharmaceutical agent and candidate for future therapeutic drug innovations.

Outer Membrane Vesicles from Acinetobacter baumannii: Biogenesis, Functions, and Vaccine Application

This review focuses on Acinetobacter baumannii, a Gram-negative bacterium that causes various infections and whose multidrug resistance has become a significant challenge in clinical practices. There are multiple bacterial mechanisms in A. baumannii that participate in bacterial colonization and immune responses. It is believed that outer membrane vesicles (OMVs) budding from the bacteria play a significant role in mediating bacterial survival and the subsequent attack against the host. Most OMVs originate from the bacterial membranes and molecules are enveloped in them. Elements similar to the pathogen endow OMVs with robust virulence, which provides a new direction for exploring the pathogenicity of A. baumannii and its therapeutic pathways. Although extensive research has been carried out on the feasibility of OMV-based vaccines against pathogens, no study has yet summarized the bioactive elements, biological activity, and vaccine applicability of A. baumannii OMVs. This review summarizes the components, biogenesis, and function of OMVs that contribute to their potential as vaccine candidates and the preparation methods and future directions for their development.

Recent advances in various bio-applications of bacteria-derived outer membrane vesicles

Outer membrane vesicles (OMVs) are spherical nanoparticles released from gram-negative bacteria. OMVs were originally classified into native 'nOMVs' (produced naturally from budding of bacteria) and non-native (produced by mechanical means). nOMVs and detergent (dOMVs) are isolated from cell supernatant without any detergent cell disruption techniques and through detergent extraction, respectively. Growth stages and conditions e.g. different stress factors, including temperature, nutrition deficiency, and exposure to hazardous chemical agents can affect the yield of OMVs production and OMVs content. Because of the presence of bacterial antigens, pathogen-associated molecular patterns (PAMPs), various proteins and the vesicle structure, OMVs have been developed in many biomedical applications. OMVs due to their size can be phagocytized by APCs, enter lymph vessels, transport antigens efficiently, and induce both T and B cells immune responses. Non-engineered OMVs have been frequently used as vaccines against different bacterial and viral infections, and various cancers. OMVs can also be used in combination with different antigens as an attractive vaccine adjuvant. Indeed, foreign antigens from target microorganisms can be trapped in the lumen of nonpathogenic vesicles or can be displayed on the surface through bacterial membrane protein to increase the immunogenicity of the antigens. In this review, different factors affecting OMV production including time of cultivation, growth media, stress conditions and genetic manipulations to enhance vesiculation will be described. Furthermore, recent advances in various biological applications of OMVs such as vaccine, drug delivery, cancer therapy, and enzyme carrier are discussed. Generally, the application of OMVs as vaccine carrier in three categories (i.e., non-engineered OMVs, OMVs as an adjuvant, recombinant OMVs (rOMVs)), as delivery system for small interfering RNA and therapeutic agents, and as enzymes carrier will be discussed.