| Summary: | <p>Abstract</p> <p>Background</p> <p><it>Burkholderia pseudomallei </it>(<it>Bp</it>) is a category B biothreat organism that causes a potentially fatal disease in humans and animals, namely melioidosis. <it>Burkholderia thailandensis </it>(<it>Bt</it>) is another naturally occurring species that is very closely related to <it>Bp</it>. However, despite this closely related genotype, <it>Bt </it>is considered avirulent as it does not cause the disease. In the present study, we compared the growth kinetics of <it>B. pseudomallei </it>strain 844 (<it>Bp</it>-844) in human monocyte-derived dendritic cells (MoDCs) and macrophages (Mφs), as well as its ability to stimulate host cell responses with those of <it>B. thailandensis </it>strain UE5 (<it>Bt</it>-UE5).</p> <p>Results</p> <p>Primary human MoDCs and Mφs were infected with <it>Bp</it>-844 and its intracellular growth kinetics and ability to induce host cell responses were evaluated. The results were compared with those obtained using the <it>Bt</it>-UE5. In human MoDCs, both bacteria were similar in respect to their ability to survive and replicate intracellularly, induce upregulation of costimulatory molecules and cytokines and bias T helper cell differentiation toward a Th1 phenotype. By contrast, the two bacteria exhibited different growth kinetics in human Mφs, where the intracellular growth of <it>Bt</it>-UE5, but not <it>Bp</it>-844, was significantly suppressed. Moreover, the ability of Mφs to kill <it>Bp</it>-844 was markedly enhanced following stimulation with IFN-γ.</p> <p>Conclusion</p> <p>The data presented showed that while both strains were similar in their ability to survive and replicate in human MoDCs, only <it>Bp</it>-844 could readily replicate in human Mφs. Both bacteria induced similar host cellular responses, particularly with regard to their ability to bias T cell differentiation toward a Th1 phenotype.</p>
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