live vaccine and pathogenic strains of B. abortus using the in vitro murine BMDC model. This would provide additional information on the potential of IR or HK vaccines for human use. Based on our data, which demonstrated that while HK and IR strain RB51 induced upregulation of costimulatory molecules, but not TNF-α or IL-12 production, the question remains as to whether live vs. HK or IR strains can also upregulate T-cell function and ultimately protect against challenge. On comparing Brucella, with other live strains of intracellular organisms such as Listeria monocytogenes (Muraille et al., 2005) and Chlamydia trachomatis (Rey-Ladino et al., 2005), live strains induced higher levels of DC maturation

compared with their HK or UV-IR forms, respectively. high throughput screening compounds see more Muraille et al. (2005) and Tsunetsugu-Yokota et al. (2002) showed that the T-lymphocytes primed by HK Listeria or Mycobacterium pulsed DCs did not fully differentiate and that only infection with live organisms induced long-term CD8+ T-cell-mediated immunity. Additionally, only live Listeria and Bacillus Calmette-Guerin strains of Mycobacterium protected against challenge (Muraille et al., 2005). On comparing our data with results from other laboratories, we found that our data were in contrast

with the data presented by Zwerdling et al. (2008) and Macedo et al. (2008). Their results showed that DC–cytokine secretion was not dependent on bacterial viability and HK B. abortus strain 2308 (at 108 or 109 bacteria mL−1) induced DC maturation and TNF-α and IL-12 secretion in a dose-dependent

fashion. The probable reasons for this discrepancy could be the lower DC (5 × 105 cells mL−1), HK and IR Methane monooxygenase cell concentrations used in our study. Our studies with live bacteria do support that live bacteria induce a dose-dependent upregulation of DC costimulatory molecule expression and cytokine production (Surendran et al., 2010). In this study, there was a dose-dependent response between 1 : 10 and 1 : 100 for HK and IR, but while higher doses stimulated more costimulatory molecule expression, neither the HK or the IR strains induced DC cytokine production at the doses tested here. With live strains, there appears to be a threshold of DC activation needed for cytokine production (Surendran et al., 2010). In this study, for an appropriate comparison between strains, we used the same doses of live, HK and IR strains RB51 and 2308 for infecting the DCs. Besides the differences in DC activation and function reported by Macedo et al. (2008) and Zwerdling et al. (2008), our results were also different from those reported by Vemulapalli (Sanakkayala et al., 2005) and Datta (Datta et al., 2006). Vemulapalli and colleagues, found that both HK and IR strain RB51 induced similar DC activation and IR vs. HK strain RB51 induced increased IL-12 secretion correlating with protection against strain 2308.