Abstract

Understanding the pathogenesis of infectious disease requires the examination and successful integration of parameters related to both microbial virulence and host responses. As a practical and powerful method to control microbial gene expression, including in vivo, the tetracycline-regulatable system has recently gained the favor of many investigative groups. However, some immunomodulatory effects of the tetracyclines, including doxycycline, could potentially limit its use to evaluate host responses during infection. Here we have used a well-established murine model of disseminated candidiasis, which is highly dependent on both the virulence displayed by the fungal cells and on the host immune status, to validate the use of this system. We demonstrate that the pathogenesis of the wild type C. albicans CAF2-1 strain, which does not contain any tet-regulatable element, is not affected by the presence of doxycycline. Moreover levels of key cytokines, chemokines and many other biomarkers, as determined by multi-analyte profiling, remain essentially unaltered by the presence of the antibiotic during infection. Our results indicate that the levels of doxycycline needed to control the tetracycline regulatable promoter gene expression system have no detectable effect on global host responses during candidiasis. Because tet-regulatable systems are now being increasingly used in a variety of pathogenic microorganisms, these observations have wide implications in the field of infectious diseases.

Highlights

  • The pathogenesis of infectious disease is complex and results from a very delicate balance between intrinsic virulence attributes displayed by the invading microorganism and the host responses that try to counteract this attack, and it is this interaction which determines the outcome of infection [1,2,3]

  • The CAF2-1 strain does not contain any tetracycline regulatable element. In this strain presence or absence of doxycycline does not regulate gene expression, and should not affect the intrinsic virulence of this strain. It follows that any differences on the overall pathogenicity observed in the presence of the antibiotic using this animal model should be strictly due to an effect on host responses

  • These results demonstrate a lack of effect of the antibiotic on virulence mechanisms and, most importantly for the purpose of the current study, point to a lack of antibiotic effect on the overall pathogenesis of candidiasis

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Summary

Introduction

The pathogenesis of infectious disease is complex and results from a very delicate balance between intrinsic virulence attributes displayed by the invading microorganism and the host responses that try to counteract this attack, and it is this interaction which determines the outcome of infection [1,2,3]. The tet-regulatable system for control of gene expression [6,7] has been adapted and used in a variety of microorganisms, including fungi, parasites and even bacteria [8,9,10,11,12,13]. This system contains a transactivator and a responsive promoter. The high specificity and affinity of the antibiotic allows for the use of doxycycline at low concentrations to confer tight control of gene expression, in the case of ‘‘tet-off’’ systems [6]

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