Immune Efficacy of a Vaccine Candidate Based on Binding Protein 26 (BP26) from Brucella melitensis Encapsulated in Niosome Nanoparticles Against Brucellosis

Abstract

Purpose Brucellosis is a common zoonosis, affecting animals and humans. Given the high prevalence of brucellosis, as well as the challenges associated with the animal vaccines, there is a need to develop effective vaccines against it. In this study, a Brucella vaccine candidate was developed based on niosome nanoparticles encapsulating BP26 protein from Brucella melitensis. Methods Cloning of amplified bp26 gene, cloning in pET28a-BL21 (DE3), and protein expression were done by optimized protocols. The properties of the synthesized niosome nanoparticles were evaluated using dynamic light scattering (DLS) and electron microscopy. Then, the entrapment efficacy, release profile, and effectiveness of BP26-encapsulated niosomes were assessed in vitro and in vivo. Results Analyses indicated BP26-encapsulated niosomes with an average size of 265.5 nm, entrapment efficacy of 95.4, and release rate of 27.4. The BP26 encapsulated in niosome maintained the humoral immune responses up to 110 days after the initial vaccination in mice. Mice immunized with free BP26 and those receiving BP26.niosome had significantly higher levels of both IgG1 (Th2) and IgG2a (Th1) compared to the controls. In addition, mice vaccinated with niosome encapsulating BP26 produced higher IFN-gamma and IL-2 cytokines as Th1 response indicators compared to BP26 alone, demonstrating the tendency of niosomes to switch the responses toward cellular immunity. Niosomes encapsulating BP26 could significantly protect the mice against Brucella melitensis. Conclusions Our results suggest BP26-encapsulating niosome as a potential vaccine candidate for combating B. melitensis. However, further investigations are needed to present BP26.niosome as a promising Brucella vaccine for clinical trials.