Genetic manipulation of Chlamydia trachomatis to investigate immune escaping strategies

Chlamydia trachomatis (C. trachomatis) is an obligate intracellular pathogen that primarily infects epithelial cells in the eye and urogenital tract. It is the most frequent cause of bacterial sexually transmitted diseases worldwide. Due to the pathogen’s immune escaping strategies, infections frequently remain asymptomatic and, if untreated, can lead to the development of severe chronic conditions like pelvic inflammatory disease, ectopic pregnancy and infertility. During C. trachomatis infections, the first immune cells that are recruited are neutrophils. However, it has been observed that the pathogen attenuates the neutrophil (PMN) response via different mechanisms, some of which remain to be clarified. To understand the mechanisms that allow the bacteria to evade the host defenses, a valuable approach is to genetically manipulate the pathogen to produce gene-specific knockout mutants. However, mutagenesis of C. trachomatis has always been challenging because of its unique biphasic life cycle and its intracellular nature. In this study Fluorescence Reported Allelic Exchange Mutagenesis (FRAEM) was successfully applied to obtain gene knock-out in C. trachomatis. In the second part of the study, neutrophils were isolated from human blood and infected with the generated mutant strains. Preliminary results suggest that cdu2, one of the genes under investigation, may play a role in attenuating the neutrophil response to Chlamydia infection. These findings provide further insights into the complex interactions between C. trachomatis and the host immune system, offering potential new avenues for future research.