Evaluation of biochemical differences and Immunological effects of LPS and Lipid A extracted from Brucella strains

Background: The intrinsic heterogeneity determination in Brucella Lipopolysaccharide (LPS) is important for explaining its chemicalnature and biological behavior. This is significant for practical purposes, since LPS is the most relevant antigen during infectionand vaccination.Objectives: The purpose of the present study was to compare biochemical and immunological differences of LPS and lipid A inthree strains of Brucella: B. melitensis (virulent strain), B. melitensis (vaccine strain, Rev1), and B. abortus (vaccine strain, S19).Materials and methods: LPSs were extracted from Brucella strains using hot phenol-water method, and lipid A was obtainedthrough mild acid hydrolysis. Glycan, phosphate, KDO, and protein concentration were evaluated in both LPS and lipid A samples.Immunological effects of Brucella LPS and lipid A were investigated measuring mitogenesis, IL-6, and Nitric Oxide (NO) production.Results: LPS and lipid A of B. melitensis have more glycan, KDO, protein, and phosphate compared with B. abortus. Differentspecies of Brucella LPS and lipid A induced NO production in a time- and dose-dependent manner via J774A.1 cells. One μg/mlLPS extracted from different strains of Brucella can induce maximum NO production. However, lipid A from S19 cannot induce NOand lipid A from B. melitensis induces NO production in higher doses of KDO than its LPS. Maximal production of IL-6 and highermitogenic index in human lymphocytes was observed by Rev1 LPS.Conclusions: Regarding the diverse biochemical and immunostimulatory properties of LPS and lipid A, these strains of Brucella canbe used potentially for different approaches, such as designing subunit brucellosis vaccines or effective adjuvants. For instance,LPS from B. abortus, as an effective and safe adjuvant due to its less toxicity, and Rev1 LPS, as subunit vaccines in developing anti-Brucella vaccines due to its high immunopotency, have been applied in several studies.