Burkholderia psuedomallei , the etiologic agent of melioidosis, causes severe disease in both humans and animals. Melioidosis is an emerging bacterial infectious disease that is being increasingly recognized in tropical regions around the world. Diagnosis and treatment of melioidosis can be challenging and no commercial vaccines currently exist. In 2015, the conservative estimated global burden of human melioidosis was ~165,000 cases with ~89,000 deaths which is equivalent to that of measles and exceeds morbidity due to leptospirosis and dengue infection. To address this, researchers at the University of Nevada, Reno recently developed a subunit vaccine formulation that protected 100% of mice against an acute lethal inhalation challenge of B. pseudomallei . The ultimate goal of their work is to better establish surrogates of immunity against B. pseudomallei infections and develop a safe and effective melioidosis vaccine for use in humans.
The subunit vaccine consists of a capsular polysaccharide-based glycoconjugate and a virulence associated type VI secretion system protein co-formulated with a CpG ODN and aluminum hyfroxide adjuvant system. A select agent excluded (BSL-2 compliant) strain of B. pseudomallei as well as E. coli were used to produce the vaccine antigens.
The vaccine contains the minimum number of antigens required to stimulate both protective humoral and cellular immune responses as well as provide immunity against all virulent isolates of B. pseudomallei . Due to the low complexity of the formulation, it is anticipated that it will be safer to use than whole-cell or outer membrane vesicle based preparations as well as enable specific surrogates of antigen-induced immunity to be defined.