Therefore, in the experimental conditions used, CT161 may not be expressed by strain L2/434. In summary, the RT-qPCR experiments supported that CT053, CT105, CT142, CT143, CT338, and CT429, and also CT144,

CT656, or CT849, could be C. trachomatis T3S effectors, possibly acting at different times of the developmental cycle. Figure 5 mRNA levels of newly identified putative effectors during the developmental cycle of C. trachomatis . The mRNA levels of ct053, ct105, ct142, ct143, ct144, ct161, ct338, ct429, ct656, and ct849 were analyzed by RT-qPCR during the developmental cycle of C. trachomatis strain L2/434, at the indicated time-points. The expression values (mean ± SEM) resulted from raw RT-qPCR

data (105) of each gene normalized to that of the 16 s rRNA gene and are from three independent experiments. Discussion Earlier studies using heterologous systems have led to SHP099 in vitro the identification of several bona-fide or putative C. trachomatis T3S effectors [13–15, 21, 22, 24–27]. While these and other analyses covered a significant portion of all C. trachomatis proteins, we hypothesized that there could be previously unidentified T3S substrates. By combining basic bioinformatics searches, exhaustive T3S assays, translocation assays, and analyses of chlamydial gene expression in infected cells, we revealed 10 C. trachomatis proteins (CT053, CT105, CT142, CT143, CT144, CT161, CT338, CT429, CT656, and CT849) as likely T3S substrates and possible find more effectors. In Phospholipase D1 particular, CT053, CT105, CT142, CT143, CT338, and CT429 were type III secreted by Y. enterocolitica, could be translocated into host cells, and their encoding genes were clearly expressed in C. trachomatis strain L2/434. Therefore, these 6 proteins have a high likelihood of being effectors. However, additional future studies are required to show that all of these 10 proteins are indeed translocated by C. trachomatis into host cells and to show that they are bona-fide effectors, i.e.,

that they interfere with host cell processes. Among the likely T3S effectors of C. trachomatis that we identified, CT105 and CT142 have been previously singled out as possible modulators of host cell functions, based on the phenotypic consequences of their ectopic expression in yeast S. cerevisiae[19]. In addition, the genes encoding CT142, CT143, and CT144 have been shown to be markedly transcriptionally regulated by a protein (Pgp4) encoded by the Chlamydia virulence plasmid [65]. This plasmid is present in almost all C. trachomatis EPZ015938 purchase clinical isolates [66], and studies in animal models of infection showed that it is a virulence factor in vivo[67, 68]. Additional studies are needed to understand if the putative effector function of CT142, CT143, and CT144 can partially explain the virulence role of the chlamydial plasmid.