The Impact of Age and Sex on Mouse Models of Melioidosis.

Mouse models have been used to generate critical data for many infectious diseases. In the case of Burkholderia pseudomallei, mouse models have been invaluable for bacterial pathogenesis studies as well as for testing novel medical countermeasures including both vaccines and therapeutics. Mouse models of melioidosis have also provided a possible way forward to better understand the chronicity associated with this infection, as it appears that BALB/c mice develop an acute infection with B. pseudomallei, whereas the C57BL/6 model is potentially more suggestive of a chronic infection. Several unanswered questions, however, persist around this model. In particular, little attention has been paid to the effect of age or sex on the disease outcome in these animal models. In this report, we determined the LD50 of the B. pseudomallei K96243 strain in both female and male BALB/c and C57BL/6 mice in three distinct age groups. Our data demonstrated a modest increase in susceptibility associated with sex in this model, and we documented important histopathological differences associated with the reproductive systems of each sex. There was a statistically significant inverse correlation between age and susceptibility. The older mice, in most cases, were more susceptible to the infection. Additionally, our retrospective analyses suggested that the impact of animal supplier on disease outcome in mice may be minimal. These observations were consistent regardless of whether the mice were injected with bacteria intraperitoneally or if they were exposed to aerosolized bacteria. All of these factors should be considered when designing experiments using mouse models of melioidosis.

Disease progression in mice exposed to low-doses of aerosolized clinical isolates of Burkholderia pseudomallei.

Mouse models have been essential to generate supporting data for the research of infectious diseases. Burkholderia pseudomallei, the etiological agent of melioidosis, has been studied using mouse models to investigate pathogenesis and efficacy of novel medical countermeasures to include both vaccines and therapeutics. Previous characterization of mouse models of melioidosis have demonstrated that BALB/c mice present with an acute infection, whereas C57BL/6 mice have shown a tendency to be more resistant to infection and may model chronic disease. In this study, either BALB/c or C57BL/6 mice were exposed to aerosolized human clinical isolates of B. pseudomallei. The bacterial strains included HBPUB10134a (virulent isolate from Thailand), MSHR5855 (virulent isolate from Australia), and 1106a (relatively attenuated isolate from Thailand). The LD50 values were calculated and serial sample collections were performed in order to examine the bacterial burdens in tissues, histopathological features of disease, and the immune response mounted by the mice after exposure to aerosolized B. pseudomallei. These data will be important when utilizing these models for testing novel medical countermeasures. Additionally, by comparing highly virulent strains with attenuated isolates, we hope to better understand the complex disease pathogenesis associated with this bacterium.

A novel respiratory model of infection with monkeypox virus in cynomolgus macaques.

Variola, the causative agent of smallpox, and the related monkeypox virus are both select agents that, if purposefully released, would cause public panic and social disruption. For this reason research continues in the areas of animal model and therapeutic development. Orthopoxviruses show a widely varying degree of host specificity, making development of accurate animal models difficult. In this paper, we demonstrate a novel respiratory infection technique that resulted in "classic" orthopox disease in nonhuman primates and takes the field of research one step closer to a better animal model.

Corynebacterial necrohemorrhagic cystitis in two female macaques.

We describe severe necrohemorrhagic cystitis in a female rhesus macaque and a female cynomolgus macaque due to colonization of the urinary bladder by Corynebacterium sp. Clinically, both macaques presented with perineal bleeding and depression and, despite extensive and prolonged treatment, succumbed to the disease. At necropsy, the contents of the urinary bladders in both cases were hemorrhagic to greenish black, and the bladder mucosa was necrotic. The major microscopic finding in each case was transmural necrohemorrhagic cystitis, with vasculitis, fibrin thrombi, and myriad gram-positive coryneform bacilli. Corynebacterium renale, Streptococcus acidominimus, and S. oralis were cultured from the urinary bladder of the rhesus macaque, and a nondiphtheritic Corynebacterium was cultured from the urinary bladder of the cynomolgus macaque. Neither animal had any other noteworthy pathologic lesions unrelated to bacterial cystitis. Corynebacterial necrohemorrhagic cystitis therefore was determined to be the cause of death in both animals. To our knowledge, this is the fi rst report of corynebacterial cystitis in nonhuman primates.

Statin-mediated correction of STAT1 signaling and inducible nitric oxide synthase expression in cystic fibrosis epithelial cells.

The expression of the inducible form of nitric oxide synthase (NOS2) is reduced in cystic fibrosis (CF) epithelium despite the presence of aggressive inflammation. A potential mechanism for reduced NOS2 expression in CF is diminished signal transducer and activator of transcription-1 (STAT1) activity, possibly due to an increase in expression of protein inhibitor of activated STAT1 (PIAS1). Previous evidence also suggests that NOS2 expression can be negatively regulated by increased activation of the GTPase RhoA, leading to the hypothesis that CF-related increases in PIAS1 expression and altered STAT1 signaling may be mediated by Rho GTPase function. Consistent with this hypothesis, data demonstrate increased expression of RhoA in two models of CF epithelium with a proportional increase in the active GTP-bound RhoA. Mouse embryonic fibroblasts null for p190B Rho GTPase-activating protein exhibit increased RhoA protein content and activation, similar to what is observed in CF models, and also exhibit CF-like alterations in STAT1 regulation, including decreased STAT1 activation, increased PIAS1 protein expression, and reduced NOS2 induction, implicating RhoA-mediated signaling in CF-related STAT1 alterations. Inhibition of the Rho GTPase pathway at the level of isoprenoid/cholesterol synthesis with mevastatin reduces PIAS1 expression, increases STAT1 activation, and restores NOS2 expression in models of CF epithelium, suggesting that pharmacological inhibition of the isoprenoid synthesis/Rho GTPase pathway may represent a potential avenue for therapeutic intervention for CF.