Early colonization of the rat upper respiratory tract by temperature modulated Bordetella bronchiseptica

Statistical Design of Experiment (DoE) based development and optimization of DB213 in situ thermosensitive gel for intranasal delivery

DB213 is an HIV-1 replication inhibitor targeting the Central Nervous System for the treatment of HIV-associated neurocognitive disorders. Current study aims to develop an in situ thermosensitive gelling system for intranasal delivery of DB213 facilitated by Statistical Design of Experiment (DoE) to conduct a more efficient experimentation by extracting the maximum amount of information from limited experiments. In our current study, information was extracted from twenty-five experimental designs from MODDE^® Software and a mathematical model was successfully developed to predict formulations to achieve desired performance as well as to analyze relationships between the amount of Pluronic F-127, Pluronic F-68, Chitosan, DB213 and the performances of in situ thermosensitive gels. Based on DoE, in situ thermosensitive gels of 1% DB213 (F1) and 5% DB213 (F2) were developed for further in vivo bioavailability and brain uptake evaluations in Sprague-Dawley rats and C57BL/6 mice, respectively. In comparison to DB213 water solution, intranasal administrations of F1 at 1 mg/kg in rats and F2 at 25 mg/kg in mice demonstrated relative bioavailabilities of 145% and 165% with significant increase in brain uptake.

Demonstration of differential virulence gene promoter activation in vivo in Bordetella pertussis using RIVET

Bordetella pertussis, the etiologic agent of whooping cough, causes disease by employing an array of virulence factors controlled by the BvgA-BvgS two-component signal transduction system. Regulation by this system has been extensively characterized in vitro, where bvg-activated genes are repressed in a process known as phenotypic modulation. Differential regulation of these genes by the response regulator BvgA results in promoters that are activated early, middle, or late after being released from modulation. However, the in vivo environmental signal and regulation pattern has not been described. In order to investigate BvgAS-mediated regulation of B. pertussis virulence factors in vivo using the mouse aerosol challenge model, we have adapted the recombinase-based in vivo technology (RIVET) system for use in B. pertussis. We have demonstrated that these strains show resolution during in vitro growth under non-modulating conditions. In addition, we have demonstrated that modulating strains by growth on media containing MgSO4 does not affect virulence in the mouse aerosol challenge model. We have therefore used the RIVET system to reveal the time-course of gene expression in vivo for selected B. pertussis virulence factors (cya, fha, prn and ptx). Our data indicate that this method can be effectively used to monitor and compare in vivo and in vitro gene expression in B. pertussis, and that temporal regulation patterns previously observed in vitro are mirrored in vivo.

Adherence of Burkholderia pseudomallei cells to cultured human epithelial cell lines is regulated by growth temperature

We have investigated the adherence of Burkholderia pseudomallei, cultured under a number of different conditions, to six human epithelial cell lines. While several complex medium compositions had relatively little effect on adherence, growth at 30 degrees C was found to significantly increase adherence to all cell lines relative to that of cultures grown at 37 degrees C (P < 0.001).

Environmental sensing mechanisms in Bordetella

The success of a bacterial pathogen may depend on its ability to sense and respond to different environments. This is particularly true of those pathogens whose survival depends on adaptation to different niches both within and outside the host. Members of the genus Bordetella cause infections in humans, other animals and birds. Two closely related species, B. pertussis and B. bronchiseptica, cause respiratory disease and express a similar range of virulence factors during infection, but exhibit different host ranges and responses to environmental change. B. pertussis has no known reservoir other than humans and is assumed to be transmitted directly via aerosol droplets between hosts. B. bronchiseptica, on the other hand, has the potential to survive and grow in the natural environment. Comparison of the manner in which these two organisms respond to external signals has provided important insights into the co-ordinate regulation of gene expression as a response to a changing environment. During infection, both species produce a range of virulence factors whose expression is co-ordinated by two members of the two-component family of signal transduction proteins, the bvg (bordetella virulence gene) and ris (regulator of intracellular stress response) loci. When active, the bvg locus directs the activity of a number of virulence determinants in both species whose products, such as adhesins and toxins, establish colonization of the host by the bacteria, although each organism has evolved a slightly different strategy during pathogenesis. B. pertussis, the causative agent of whooping cough, promotes an acute disease and tends to be more virulent than B. bronchiseptica which generally causes chronic and persistent asymptomatic colonization of the respiratory tract. The recently identified ris locus appears to control the expression of factors important for intracellular survival of B. bronchiseptica, but a role for this regulatory locus in B. pertussis infection has not been established. Expression of the virulence determinants controlled by the bvg and ris loci is subject to modulation by different environmental signals, such as low temperature, which act through these two-component systems. Evidence indicates that, for B. bronchiseptica, bvg-controlled determinants expressed under modulating conditions, such as motility, facilitate adaptation and survival in environments outside the host. With B. pertussis, however, there is no apparent requirement for prolonged survival outside the host and this difference is reflected in the expression of different, as yet uncharacterized, determinants as a response to modulating signals. The nature of the gene products involved and their assumed role in the life cycle of B. pertussis remains to be determined. Thus, comparative analysis of these species provides an excellent model for understanding the genetic requirements for pathogenesis of respiratory infection and adaptation to changing environments, both within and outside the host.