Osteopontin Impairs Host Defense during Established Gram-Negative Sepsis Caused by Burkholderia pseudomallei (Melioidosis)

Melioidosis is a severe tropical disease caused by infection with the bacterium Burkholderia (B.) pseudomallei. In northeast Thailand infection with this bacterium is the major cause of community-acquired septicemia with a mortality rate up to 40%. Extending the knowledge on the mechanisms of host defense against B. pseudomallei infection would be helpful to improve treatment of this severe illness. Osteopontin (OPN) is a cytokine that is involved in several immune responses that occur during bacterial infection. In this study, we investigated levels of OPN in patients with melioidosis, and studied the function of OPN during experimental melioidosis in mice. We found that OPN concentrations were elevated in patients with severe melioidosis, and that high OPN concentrations are associated with poor outcome in patients with melioidosis. In experimental melioidosis in mice plasma and lung OPN levels were also increased. Moreover, mice with melioidosis that were deficient for OPN demonstrated reduced bacterial numbers in their lungs, diminished pulmonary tissue injury, and decreased neutrophil infiltration into the lungs during established melioidosis. Moreover, these mice displayed a delayed mortality as compared to control mice. In conclusion, sustained production of OPN impairs host defense during melioidosis

Ecological Paradigms for the Tropics: Old Questions and Continuing Challenges

This chapter focuses on the ecological response mechanisms of the Luquillo Mountains tonatural and human-induced disturbances, such as hurricanes and land cover change. It identifies the ecosystems of the Luquillo Mountains as a perfect representation of large masses of a non-frost tropical land because of its naturally occurring features: high rainfall, hurricane disturbances, maritime climate, and insularity. It then sets out the Luquillo Long-Term Ecological Research (LTER) program as a by-product of the 20th and 21st century experimentations, and discusses its contributions to the basic understanding of the ecological make-up and biogeochemistry of the Luquillo Mountains