Comparison of transcriptional profiles of Treponema pallidum during experimental infection of rabbits and in vitro culture: Highly similar, yet different

Abstract

Treponema pallidum ssp. pallidum, the causative agent of syphilis, can now be cultured continuously in vitro utilizing a tissue culture system, and the multiplication rates are similar to those obtained in experimental infection of rabbits. In this study, the RNA transcript profiles of the T. pallidum Nichols during in vitro culture and rabbit infection were compared to examine whether gene expression patterns differed in these two environments. To this end, RNA preparations were converted to cDNA and subjected to RNA-seq using high throughput Illumina sequencing; reverse transcriptase quantitative PCR was also performed on selected genes for validation of results. The transcript profiles in the in vivo and in vitro environments were remarkably similar, exhibiting a high degree of concordance overall. However, transcript levels of 94 genes (9%) out of the 1,063 predicted genes in the T. pallidum genome were significantly different during rabbit infection versus in vitro culture, varying by up to 8-fold in the two environments. Genes that exhibited significantly higher transcript levels during rabbit infection included those encoding multiple ribosomal proteins, several prominent membrane proteins, glycolysis-associated enzymes, replication initiator DnaA, rubredoxin, thioredoxin, two putative regulatory proteins, and proteins associated with solute transport. In vitro cultured T. pallidum had higher transcript levels of DNA repair proteins, cofactor synthesis enzymes, and several hypothetical proteins. The overall concordance of the transcript profiles may indicate that these environments are highly similar in terms of their effects on T. pallidum physiology and growth, and may also reflect a relatively low level of transcriptional regulation in this reduced genome organism.

High-throughput nanopore sequencing of Treponema pallidum tandem repeat genes arp and tp0470 reveals clade-specific patterns and recapitulates global whole genome phylogeny

“…There is ample evidence the proteins encoded by tp0470 and arp genes are present during infection: Previous studies have shown that the tp0470 transcript is expressed ( Smajs et al, 2005 ; De Lay et al, 2021 ), and sera from infected rabbits ( McKevitt et al, 2005 ) and patients ( Brinkman et al, 2006 ) are reactive to TP0470 protein. The arp transcript is expressed ( Smajs et al, 2005 ; De Lay et al, 2021 ), and the ARP protein was found to be one of the top 10% most abundant proteins by mass spectrometry ( Osbak et al, 2016 ). T. pallidum -infected rabbit sera are reactive to ARP ( McKevitt et al, 2005 ; Liu et al, 2007 ), while sera from infected human patients are weakly reactive to ARP during primary infection ( Brinkman et al, 2006 ).…”

Notes on syphilis vaccine development

“…As the genomics gap is being closed at unprecedented speed for T. pallidum , the application of other “-omics,” mainly transcriptomics and proteomics, will provide complementary information to help identify vaccine candidates ( 32 , 33 ). Only limited work to date has focused on analyzing the T. pallidum transcriptome and proteome ( 32 – 38 ).…”

“…In addition to being poorly expressed, selected OMP-encoding genes have been reported to undergo stochastic modulation of gene expression through phase variation, which might contribute to changing the pathogen surface antigenic profile ( 39 , 40 ). To date, a microarray study describing transcriptome of Nichols strain was conducted and found that the RNA transcript of T. pallidum profiles between in vitro culture and rabbit infection were similar ( 33 ). A better understanding of gene regulation and gene expression could lead to exclusion of specific vaccine candidates whose transcription might be turned off with no detriment to the pathogen.…”

“…To date, transcriptional profiles of T. pallidum have been obtained from rabbit or in vitro -propagated strains ( 33 ). Although those studies are valuable in improving our understanding of gene expression in T. pallidum , an equally important endeavor would be to assess gene expression in spirochetes from patient samples.…”

Treponema pallidum protein Tp0136 promoting MMPs/TIMPs imbalance via PI3K, MAPK and NF-κB signalling pathways in HDVSMCs

“…T. pallidum protein Tp0136, a fibronectin-binding protein is known to induce fibroblasts to produce MMP9 [ 15 ]. In addition, Tp0136 mRNA transcript levels have been reported to be considerably higher when compared with the rest of the transcriptome during syphilis infection [ 16 , 17 ], suggesting that Tp0136 might have a significant role in the process of T. pallidum infection. Based on this finding, we stipulated that Tp0136 would promote the expression of MMP or TIMP, which in turn might contribute to the imbalance of MMP/TIMP, which can induce T. pallidum invasion and dissemination from the site of entry.…”