may be the etiological agent of human melioidosis, a disease with a broad spectrum of clinical manifestations ranging from fatal septicemia to chronic localized infection or asymptomatic latent infection. interferon (IFN-), interleukin-6 (IL-6), monocyte JIB-04 chemotactic protein-1 (MCP-1), and tumor necrosis factor- (TNF-) were induced during chronic infection, and histopathological analysis showed features in common with human melioidosis. Interestingly, many of these features were similar to those induced by in humans, such as development of a collagen cord that encapsulates the lesions, the presence of multinucleated giant cells, and granulomas with a caseous necrotic center, which may explain why chronic melioidosis is often misdiagnosed as tuberculosis. Our model now provides a relevant and practical tool to define the immunological features of chronic melioidosis and aid in the development of more effective treatment of this disease in humans. is a Gram-negative soil bacterium that is the causative agent of melioidosis. This pathogen is endemic in Southeast Asia and Northern Australia, but cases of melioidosis are now being reported in numerous other tropical areas, suggesting a more global distribution of the organism in the environment.1,2 The main routes of infection are believed to be via inhalation of aerosols during the rainy season or via cutaneous inoculation in people who have direct contact with wet soil.3 The consequences of infection with are remarkably diverse, ranging from an acute septicemia to a chronic localized disease or an asymptomatic latent infection. Acute infection is characterized by bacteremia, progression to septic shock with the induction of a massive but ineffective cytokine response, and a high mortality JIB-04 rate.3C5 Chronic infection is generally less severe and often characterized by persistent, localized infection that is difficult to eradicate.3,6 Recurrent disease is also common, and it is mostly due to relapse rather than reinfection. 7 The disease can also reactivate after decades of clinical latency, 8 suggesting that the bacteria may enter a dormant state where it can avoid immune surveillance.9 Despite the clear impact of this infection on public health in endemic regions, we do not understand how evades the immune response and causes a chronic infection. Chronic melioidosis is frequently misdiagnosed as tuberculosis, and the two diseases share several histological features,2,10 suggesting the possibility of common immunological mechanisms between these two infections. Animal models represent powerful tools to study immunity and virulence factors, and both outbred and inbred strains have been previously described as models to study human melioidosis.10C15 Typically, BALB/c mice, which are very susceptible, have been used to study acute melioidosis.14,16,17 In contrast, C57BL/6 mice show increased resistance to infection but are unable to clear infection, so they are better candidates to mimic chronic infection in humans.11,14 The mechanisms that regulate the development of either acute, chronic, or latent melioidosis remain unclear. However, it has been suggested that differential inflammatory responses in BALB/c mice versus C57BL/6 after infection may be responsible JIB-04 for different susceptibility to infection, suggesting that high levels of inflammatory cytokines in BALB/c may contribute JIB-04 to the immunopathogenesis.18 Other animals such as hamsters, guinea pigs, and rats have also been used,10,19 but there is little information on truly chronic models where disease progression is monitored over several months post-challenge.10,20 No licensed vaccine exists for either prophylactic or therapeutic use against 576 and investigated the histological and inflammatory responses to infection over an extended time course. Our aim was to develop a murine model of chronic disease that JIB-04 reflects chronic disease in humans. In the longer term, this model would be invaluable for evaluating pretreatments and therapeutics that might be used to treat or eliminate chronic infections. Materials and Methods Bacteria Strain strain 576 was originally isolated from a patient with a fatal case of human melioidosis in Thailand, and was kindly provided by Dr. Tyrone Pitt (Health Protection Agency, London, UK). Frozen stocks were prepared as previously described.32 All procedures involving live bacteria were performed under ACDP (Advisory Committee on Dangerous Pathogens) containment level 3 conditions. Infection of Mice and Determination of Tissue and Blood Bacterial Load Female C57BL/6 mice (6- to 8-week-old; Harlan Laboratories, Bicester, Oxon, UK) were used throughout the studies. All animal experiments were performed in accordance with the guidelines of the Animals (Scientific Procedures) Act of 1986 and were approved by the local ethical review committee at the London School of Hygiene and Tropical Medicine. A total number of 241 animals were used (191 chronically infected, 10 acutely infected, and 40 uninfected controls), distributed in 11 independent experiments. The number of animals used per experiment Rabbit polyclonal to ZNF562 and the number of experiments are shown in the figure legends. For survival curves, a total of 76 mice were used. Bacterial load and.