Brucella species are the causative agents of one of the most prevalent zoonotic diseases: brucellosis. Infections by Brucella species cause major economic losses in agriculture, leading to abortions in infected animals and resulting in a severe, although rarely lethal, debilitating disease in humans. Brucella species persist as intracellular pathogens that manage to effectively evade recognition by the host's immune system. Sugar-modified components in the Brucella cell envelope play an important role in their host interaction. Brucella lipopolysaccharide (LPS), unlike Escherichia coli LPS, does not trigger the host's innate immune system. Brucella produces cyclic -1,2-glucans, which are important for targeting them to their replicative niche in the endoplasmic reticulum within the host cell. This paper will focus on the role of LPS and cyclic -1,2-glucans in Brucella-mammalian infections and discuss the use of mutants, within the biosynthesis pathway of these cell envelope structures, in vaccine development. 1. Introduction Brucellosis is a disease that can be found in most countries around the world and is transferred from animals to humans [1]. With more than 500,000 new cases of human infections each year, it is the most prevalent zoonotic disease worldwide [1]. Although brucellosis very rarely leads to the death of the patient, it is a seriously debilitating disease that presents with, among other symptoms, fever, fatigue, nausea, and weight loss [2]. Brucellosis is thought to be underreported as the symptoms very often are mistaken for a common flu [2]. However, if not properly treated, brucellosis can become a chronic and asymptomatic disease that can re-emerge months after the initial infection [2]. The causative agents of brucellosis are brucellae, nonmotile, Gram-negative α-proteobacteria that are facultative intracellular pathogens [2]. The genus Brucella currently contains ten species, named primarily after their preferred host organism or symptoms of the infection: B. melitensis (goats and sheep), B. abortus (cattle) [3], B. suis (swine, reindeer and rodents) [4], B. canis (dogs) [5], B. ovis (sheep) [6], B. neomtomae (rodents) [7], B. microti (voles and red foxes) [8], B. inopinata (unknown) [9], B. pinnipedialis (seals), and B. ceti (dolphins and porpoises) [10]. Most human Brucella infections can be traced back to the three species, B. melitensis, B. suis, and B. abortus [11]. The isolation of marine mammal Brucella species (B. pinnipedialis and B. ceti) from human patients, however, suggests that these species are emerging human
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