The Gonococcal Transcriptome during Infection of the Lower Genital Tract in Women.

Ryan Mcclure,Caroline A Genco,Paola Massari,Kathleen Nudel,Peter A Rice,Xiaohong Su,Brian Tjaden,Thomas Rudel

doi:10.1371/journal.pone.0133982

Abstract

Gonorrhea is a highly prevalent disease resulting in significant morbidity worldwide, with an estimated 106 cases reported annually. Neisseria gonorrhoeae, the causative agent of gonorrhea, colonizes and infects the human genital tract and often evades host immune mechanisms until successful antibiotic treatment is used. The alarming increase in antibiotic-resistant strains of N. gonorrhoeae, the often asymptomatic nature of this disease in women and the lack of a vaccine directed at crucial virulence determinants have prompted us to perform transcriptome analysis to understand gonococcal gene expression patterns during natural infection. We sequenced RNA extracted from cervico-vaginal lavage samples collected from women recently exposed to infected male partners and determined the complete N. gonorrhoeae transcriptome during infection of the lower genital tract in women. On average, 3.19% of total RNA isolated from female samples aligned to the N. gonorrhoeae NCCP11945 genome and 1750 gonococcal ORFs (65% of all protein-coding genes) were transcribed. High expression in vivo was observed in genes encoding antimicrobial efflux pumps, iron response, phage production, pilin structure, outer membrane structures and hypothetical proteins. A parallel analysis was performed using the same strains grown in vitro in a chemically defined media (CDM). A total of 140 genes were increased in expression during natural infection compared to growth in CDM, and 165 genes were decreased in expression. Large differences were found in gene expression profiles under each condition, particularly with genes involved in DNA and RNA processing, iron, transposase, pilin and lipoproteins. We specifically interrogated genes encoding DNA binding regulators and iron-scavenging proteins, and identified increased expression of several iron-regulated genes, including tbpAB and fbpAB, during infection in women as compared to growth in vitro, suggesting that during infection of the genital tract in women, the gonococcus is exposed to an iron deplete environment. Collectively, we demonstrate that a large portion of the gonococcal genome is expressed and regulated during mucosal infection including genes involved in regulatory functions and iron scavenging.

Highlights

The sexually transmitted infection (STI) gonorrhea, caused by the Gram-negative bacterium Neisseria gonorrhoeae, is the second most common reportable disease in the U.S In 2014, there were 331,000 reported cases and the total annual number is estimated to be 800,000 due to underreporting (Centers for Disease Control and Prevention)
High expression of several similar genes was detected in each of the vaginal samples (Table 1). These similarities in gene expression occurred despite temporal differences in the exposure of female subjects to the infected partner(s), menstrual cycle and degree of cervico-vaginal neutrophilia (Table 2). This core set of similar genes included those encoding outer membrane housekeeping, stress response, phage associated (NGK_1145) and hypothetical proteins (NGK_0472, NGK_2043) (Table 1)
In this study we report the complete gonococcal transcriptome expressed during infection in women

Summary

Introduction

The sexually transmitted infection (STI) gonorrhea, caused by the Gram-negative bacterium Neisseria gonorrhoeae, is the second most common reportable disease in the U.S In 2014, there were 331,000 reported cases and the total annual number is estimated to be 800,000 due to underreporting (Centers for Disease Control and Prevention). DNA binding proteins that are important in infection include sigma factors, such as RpoH, shown to increase transcription of genes involved in stress response and adherence to epithelial cells [9,10], and OxyR, which regulates expression of genes such as catalase, involved in resistance to bactericidal reactive oxygen species [11]. Another well-known factor crucial for a successful host infection is Fur, which regulates intracellular iron levels [12,13]. Targets of Fur include the ferric-binding protein (FbpA), transferrin binding proteins (TbpAB) and lactoferrin binding proteins (LbpAB)

Methods

Results

Conclusion