Ribonucleotide reductase, a novel drug target for gonorrhea

Antibiotic-resistant Neisseria gonorrhoeae (Ng) are an emerging public health threat due to increasing numbers of multidrug resistant (MDR) organisms. We identified two novel orally active inhibitors, PTC-847 and PTC-672, that exhibit a narrow spectrum of activity against Ng including MDR isolates. By selecting organisms resistant to the novel inhibitors and sequencing their genomes, we identified a new therapeutic target, the class Ia ribonucleotide reductase (RNR). Resistance mutations in Ng map to the N-terminal cone domain of the α subunit, which we show here is involved in forming an inhibited α4β4 state in the presence of the β subunit and allosteric effector dATP. Enzyme assays confirm that PTC-847 and PTC-672 inhibit Ng RNR and reveal that allosteric effector dATP potentiates the inhibitory effect. Oral administration of PTC-672 reduces Ng infection in a mouse model and may have therapeutic potential for treatment of Ng that is resistant to current drugs.

Neisseria gonorrhoeae subverts formin-dependent actin polymerization to colonize human macrophages

Dynamic reorganization of the actin cytoskeleton dictates plasma membrane morphogenesis and is frequently subverted by bacterial pathogens for entry and colonization of host cells. The human-adapted bacterial pathogen Neisseria gonorrhoeae can colonize and replicate when cultured with human macrophages, however the basic understanding of how this process occurs is incomplete. N. gonorrhoeae is the etiological agent of the sexually transmitted disease gonorrhea and tissue resident macrophages are present in the urogenital mucosa, which is colonized by the bacteria. We uncovered that when gonococci colonize macrophages, they can establish an intracellular or a cell surface-associated niche that support bacterial replication independently. Unlike other intracellular bacterial pathogens, which enter host cells as single bacterium, establish an intracellular niche and then replicate, gonococci invade human macrophages as a colony. Individual diplococci are rapidly phagocytosed by macrophages and transported to lysosomes for degradation. However, we found that surface-associated gonococcal colonies of various sizes can invade macrophages by triggering actin skeleton rearrangement resulting in plasma membrane invaginations that slowly engulf the colony. The resulting intracellular membrane-bound organelle supports robust bacterial replication. The gonococci-occupied vacuoles evaded fusion with the endosomal compartment and were enveloped by a network of actin filaments. We demonstrate that gonococcal colonies invade macrophages via a process mechanistically distinct from phagocytosis that is regulated by the actin nucleating factor FMNL3 and is independent of the Arp2/3 complex. Our work provides insights into the gonococci life-cycle in association with human macrophages and defines key host determinants for macrophage colonization.

During infection, the human-adapted bacterial pathogen Neisseria gonorrhoeae and causative agent of gonorrhea can invade the submucosa of the urogenital tract where it encounters tissue-resident innate immune sentinels, such as macrophages and neutrophils. Instead of eliminating gonococci, macrophages support robust bacterial replication. Here, we detail the life cycle of N. gonorrhoeae in association with macrophages and define key regulators that govern the colonization processes. We uncovered that N. gonorrhoeae establishes two distinct subcellular niches that support bacterial replication autonomously–one niche was on the macrophage surface and another one was intracellular. Gonococci subverted the host actin cytoskeleton through the actin nucleating factor FMNL3 to invade colonized macrophages and occupy a membrane-bound intracellular organelle. We propose that N. gonorrhoeae ability to occupy distinct subcellular niches when colonizing macrophages likely confers broad protection against multiple host defense responses.

Neisseria gonorrhoeae evades autophagic killing by downregulating CD46-cyt1 and remodeling lysosomes

The Gram-negative human pathogen N. gonorrhoeae (Ngo) quickly attaches to epithelial cells, and large numbers of the bacteria remain on the cell surface for prolonged periods. Ngo invades cells but few viable intracellular bacteria are recovered until later stages of infection, leading to the assumption that Ngo is a weak invader. On the cell surface, Ngo quickly recruits CD46-cyt1 to the epithelial cell cortex directly beneath the bacteria and causes its cleavage by metalloproteinases and Presenilin/γSecretease; how these interactions affect the Ngo lifecycle is unknown. Here, we show Ngo induces an autophagic response in the epithelial cell through CD46-cyt1/GOPC, and this response kills early invaders. Throughout infection, the pathogen slowly downregulates CD46-cyt1 and remodeling of lysosomes, another key autophagy component, and these activities ultimately promote intracellular survival. We present a model on the dynamics of Ngo infection and describe how this dual interference with the autophagic pathway allows late invaders to survive within the cell.

Utilizing CMP-Sialic Acid Analogs to Unravel Neisseria gonorrhoeae Lipooligosaccharide-Mediated Complement Resistance and Design Novel Therapeutics

Neisseria gonorrhoeae deploys a novel immune evasion strategy wherein the lacto-N-neotetraose (LNnT) structure of lipooligosaccharide (LOS) is capped by the bacterial sialyltransferase, using host cytidine-5’-monophosphate (CMP)-activated forms of the nine-carbon nonulosonate (NulO) sugar N-acetyl-neuraminic acid (Neu5Ac), a sialic acid (Sia) abundant in humans. This allows evasion of complement-mediated killing by recruiting factor H (FH), an inhibitor of the alternative complement pathway, and by limiting classical pathway activation (“serum-resistance”). We utilized CMP salts of six additional natural or synthetic NulOs, Neu5Gc, Neu5Gc8Me, Neu5Ac9Ac, Neu5Ac9Az, legionaminic acid (Leg5Ac7Ac) and pseudaminic acid (Pse5Ac7Ac), to define structural requirements of Sia-mediated serum-resistance. While all NulOs except Pse5Ac7Ac were incorporated into the LNnT-LOS, only Neu5Gc incorporation yielded high-level serum-resistance and FH binding that was comparable to Neu5Ac, whereas Neu5Ac9Az and Leg5Ac7Ac incorporation left bacteria fully serum-sensitive and did not enhance FH binding. Neu5Ac9Ac and Neu5Gc8Me rendered bacteria resistant only to low serum concentrations. While serum-resistance mediated by Neu5Ac was associated with classical pathway inhibition (decreased IgG binding and C4 deposition), Leg5Ac7Ac and Neu5Ac9Az incorporation did not inhibit the classical pathway. Remarkably, CMP-Neu5Ac9Az and CMP-Leg5Ac7Ac each prevented serum-resistance despite a 100-fold molar excess of CMP-Neu5Ac in growth media. The concomitant presence of Leg5Ac7Ac and Neu5Ac on LOS resulted in uninhibited classical pathway activation. Surprisingly, despite near-maximal FH binding in this instance, the alternative pathway was not regulated and factor Bb remained associated with bacteria. Intravaginal administration of CMP-Leg5Ac7Ac to BALB/c mice infected with gonorrhea (including a multidrug-resistant isolate) reduced clearance times and infection burden. Bacteria recovered from CMP-Leg5Ac7Ac-treated mice were sensitive to human complement ex vivo, simulating in vitro findings. These data reveal critical roles for the Sia exocyclic side-chain in gonococcal serum-resistance. Such CMP-NulO analogs may provide a novel therapeutic strategy against the global threat of multidrug-resistant gonorrhea.

Neisseria gonorrhoeae, the causative agent of the sexually transmitted infection gonorrhea, has developed widespread resistance to almost every conventional antibiotic currently in clinical use. Novel therapeutics are urgently needed against this pathogen. Gonococci have the capacity to scavenge CMP-N-acetyl-neuraminic acid (CMP-Neu5Ac, a CMP-activated 9-carbon sugar that is a member of the ‘sialic acid family’) from the host to ‘cap’ its lipooligosaccharide with Neu5Ac, which renders gonococci resistant to complement, a key arm of innate immune defenses. Here, we show that gonococci also utilize derivatives (or analogs) of CMP-Neu5Ac, which not only fail to render the bacteria resistant to complement, but also prevent complement inhibition mediated by the ‘physiologic’ human sialic acid donor, CMP-Neu5Ac. When administered intravaginally to mice, a representative analog significantly shortened the duration and burden of gonococcal infection. Thus, CMP-sialic acid analogs may represent promising preventive or therapeutic agents against multidrug-resistant gonorrhea that poses a global threat to public health.

[MOLECULAR MECHANISMS OF DRUG RESISTANCE NEISSERIA GONORRHOEAE HISTORY AND PROSPECTS]

Neisseria gonorrhoeae (gonococcus) is a strict human pathogen, which causes gonorrhea--an infectious disease, whose origin dates back to more than two thousand years. Due to the unique plasticity of the genetic material, these bacteria have acquired the capacity to adapt to the host immune system, cause repeated infections, as well as withstand antimicrobials. Since the introduction of antibiotics in 1930s, gonococcus has displayed its propensity to develop resistance to all clinically useful antibiotics. It is important to note that the known resistance determinants of N. gonorrhoeae were acquired through horizontal gene transfer, recombination and spontaneous mutagenesis, and may be located both in the chromosome and on the plasmid. After introduction of a new antimicrobial drug, gonococcus becomes resistant within two decades and replaces sensitive bacterial population. Currently Ceftriaxone is the last remaining antibiotic for first-line treatment of gonorrhea. However, the first gonococcus displaying high-level resistance to Ceftriaxone was isolated in Japan a few years ago. Therefore, in the near future, gonorrhea may become untreatable. In the present review, we discuss the chronology of the anti-gonorrhea drugs (antibiotics) replacement, the evolution of resistance mechanisms emergence and future perspectives of N. gonorrhoeae treatment.

Pilus phase variation switches gonococcal adherence to invasion by caveolin-1-dependent host cell signaling

Many pathogenic bacteria cause local infections but occasionally invade into the blood stream, often with fatal outcome. Very little is known about the mechanism underlying the switch from local to invasive infection. In the case of Neisseria gonorrhoeae, phase variable type 4 pili (T4P) stabilize local infection by mediating microcolony formation and inducing anti-invasive signals. Outer membrane porin PorB(IA), in contrast, is associated with disseminated infection and facilitates the efficient invasion of gonococci into host cells. Here we demonstrate that loss of pili by natural pilus phase variation is a prerequisite for the transition from local to invasive infection. Unexpectedly, both T4P-mediated inhibition of invasion and PorB(IA)-triggered invasion utilize membrane rafts and signaling pathways that depend on caveolin-1-Y14 phosphorylation (Cav1-pY14). We identified p85 regulatory subunit of PI3 kinase (PI3K) and phospholipase Cγ1 as new, exclusive and essential interaction partners for Cav1-pY14 in the course of PorBIA-induced invasion. Active PI3K induces the uptake of gonococci via a new invasion pathway involving protein kinase D1. Our data describe a novel route of bacterial entry into epithelial cells and offer the first mechanistic insight into the switch from local to invasive gonococcal infection.

Critical role of Th17 responses in a murine model of Neisseria gonorrhoeae genital infection

Host immune responses, including the characteristic influx of neutrophils, against Neisseria gonorrhoeae are poorly understood; adaptive immunity is minimal and non-protective. We hypothesize that N. gonorrhoeae selectively elicits Th17-dependent responses, which trigger innate defense mechanisms, including neutrophils and antimicrobial proteins, that it can resist. We found that N. gonorrhoeae induced the production of interleukin-17 (IL-17) in mouse T-cells and Th17-inducing cytokines in mouse and human APCs in vitro. IL-17 was induced in the iliac lymph nodes in vivo in a female mouse model of genital tract gonococcal infection. Antibody blockade of IL-17 or deletion of the major IL-17 receptor (IL-17R) in IL-17RA(KO) mice led to prolonged infection and diminished neutrophil influx. Genital tract tissue from IL-17RA(KO) mice showed reduced production of neutrophil-attractant chemokines in response to culture with N. gonorrhoeae. These results imply a crucial role for IL-17 and Th17 cells in the immune response to N. gonorrhoeae.

Bim and Bmf synergize to induce apoptosis in Neisseria gonorrhoeae infection

Bcl-2 family proteins including the pro-apoptotic BH3-only proteins are central regulators of apoptotic cell death. Here we show by a focused siRNA miniscreen that the synergistic action of the BH3-only proteins Bim and Bmf is required for apoptosis induced by infection with Neisseria gonorrhoeae (Ngo). While Bim and Bmf were associated with the cytoskeleton of healthy cells, they both were released upon Ngo infection. Loss of Bim and Bmf from the cytoskeleton fraction required the activation of Jun-N-terminal kinase-1 (JNK-1), which in turn depended on Rac-1. Depletion and inhibition of Rac-1, JNK-1, Bim, or Bmf prevented the activation of Bak and Bax and the subsequent activation of caspases. Apoptosis could be reconstituted in Bim-depleted and Bmf-depleted cells by additional silencing of antiapoptotic Mcl-1 and Bcl-X_L, respectively. Our data indicate a synergistic role for both cytoskeletal-associated BH3-only proteins, Bim, and Bmf, in an apoptotic pathway leading to the clearance of Ngo-infected cells.

A variety of physiological death signals, as well as pathological insults, trigger apoptosis, a genetically programmed form of cell death. Pathogens often induce host cell apoptosis to establish a successful infection. Neisseria gonorrhoeae (Ngo), the etiological agent of the sexually transmitted disease gonorrhoea, is a highly adapted obligate human-specific pathogen and has been shown to induce apoptosis in infected cells. Here we unveil the molecular mechanisms leading to apoptosis of infected cells. We show that Ngo-mediated apoptosis requires a special subset of proapoptotic proteins from the group of BH3-only proteins. BH3-only proteins act as stress sensors to translate toxic environmental signals to the initiation of apoptosis. In a siRNA-based miniscreen, we found Bim and Bmf, BH3-only proteins associated with the cytoskeleton, necessary to induce host cell apoptosis upon infection. Bim and Bmf inactivated different inhibitors of apoptosis and thereby induced cell death in response to infection. Our data unveil a novel pathway of infection-induced apoptosis that enhances our understanding of the mechanism by which BH3-only proteins control apoptotic cell death.

Properdin can initiate complement activation by binding specific target surfaces and providing a platform for de novo convertase assembly

Complement promotes the rapid recognition and elimination of pathogens, infected cells, and immune complexes. The biochemical basis for its target specificity is incompletely understood. In this report, we demonstrate that properdin can directly bind to microbial targets and provide a platform for the in situ assembly and function of the alternative pathway C3 convertases. This mechanism differs from the standard model wherein nascent C3b generated in the fluid phase attaches nonspecifically to its targets. Properdin-directed complement activation occurred on yeast cell walls (zymosan) and Neisseria gonorrhoeae. Properdin did not bind wild-type Escherichia coli, but it readily bound E. coli LPS mutants, and the properdin-binding capacity of each strain correlated with its respective serum-dependent AP activation rate. Moreover, properdin:single-chain Ab constructs were used to direct serum-dependent complement activation to novel targets. We conclude properdin participates in two distinct complement activation pathways: one that occurs by the standard model and one that proceeds by the properdin-directed model. The properdin-directed model is consistent with a proposal made by Pillemer and his colleagues >50 years ago.

The specific innate immune receptor CEACAM3 triggers neutrophil bactericidal activities via a Syk kinase-dependent pathway

The human-restricted pathogens Neisseria gonorrhoeae, Neisseria meningitidis, Haemophilus influenzae and Moraxella catarrhalis colonize host tissues via carcinoembryonic antigen-related cellular adhesion molecules (CEACAMs). One such receptor, CEACAM3, acts in a host-protective manner by orchestrating the capture and engulfment of invasive bacteria by human neutrophils. Herein, we show that bacterial binding to CEACAM3 causes recruitment of the cytoplasmic tyrosine kinase Syk, resulting in the phosphorylation of both CEACAM3 and Syk. This interaction is specific for the immunoreceptor tyrosine-based activation motif (ITAM) in the CEACAM3 cytoplasmic domain. While dispensable for the phagocytic uptake of single bacteria by CEACAM3, Syk is necessary for internalization when cargo size increases or when the density of CEACAM-binding ligand on the cargo surface is below a critical threshold. Moreover, Syk engagement is required for an effective bacterial killing response, including the neutrophil oxidative burst and degranulation functions in response to N. gonorrhoeae. These data reveal CEACAM3 as a specific innate immune receptor that mediates the opsonin-independent clearance of CEACAM-binding bacteria via Syk, a molecular trigger for functional immunoreceptor responses of both the adaptive (TCR, BCR, FcR) and innate (Dectin-1, CEACAM3) immune systems.

Structure of the N-terminal domain of human CEACAM1: binding target of the opacity proteins during invasion of Neisseria meningitidis and N. gonorrhoeae

CEACAM1 is a cellular adhesion molecule whose protein expression is down-regulated in several carcinomas and which also contributes to the pathogenicity of Neisseria by acting as a receptor for Opa proteins. The crystal structure of the N-terminal (D1) domain of human CEACAM1 has been determined at 2.2 Angstrom resolution. The structure shows several differences compared with a lower resolution model of the same domain from mouse solved previously, especially in the functional regions. Mapping of the sites of mutations that lower or abolish the binding of CEACAM1 to Opa proteins shows a distinct clustering of residues on the GFCC'C'' face of the molecule. Prominent amongst these are residues in the C, C' and F strands and the CC' loop. A similar analysis shows that the region responsible for homophilic or heterophilic interactions of CEACAM1 is also on the GFCC'C'' face and overlaps partially with the Opa-binding region. This higher resolution structure of CEACAM1 will facilitate a more precise dissection of its functional regions in the context of neisserial pathogenesis, cellular adhesion and immune evasion.

Type IV pili of Neisseria gonorrhoeae influence the activation of human CD4+ T cells

Neisseria gonorrhoeae is the causative agent of the sexually transmitted disease gonorrhea, and infection with this organism is typically associated with an intense inflammatory response. In many individuals, however, the infection is asymptomatic and can progress to serious secondary complications. The type IV pili of Neisseria gonorrhoeae mediate binding of the bacteria to host cells and are involved in cellular signal transduction. In these studies we have demonstrated that gonococcal pili influence human CD4+ T cells by using isogenic strains of N. gonorrhoeae with piliated and nonpiliated phenotypes. To determine the impact of piliation on the cellular status, we examined the expression of activation markers, cellular proliferation, and the production of cytokines after infection. The activation marker CD69 showed significantly increased expression on cells infected with the piliated strain, and this expression was dependent on costimulation of the T-cell receptor. Infection with piliated gonococci also altered T-cell proliferation and influenced the production of the regulatory cytokine interleukin-10. PilC, the putative pilus adhesin, was also observed to influence cellular activation but had no impact on the proliferation of cells further indicating that pilus-mediated adhesion is important in gonococcal stimulation of CD4+ T cells. These results show that the piliation status of gonococci influences CD4+ T-cell activation and that the adhesion mediated by pilus components aids in the regulation of the T-cell response to N. gonorrhoeae.

Global gene expression and the role of sigma factors in Neisseria gonorrhoeae in interactions with epithelial cells

Like many bacterial pathogens, Neisseria gonorrhoeae must adapt to environmental changes in order to successfully colonize and proliferate in a new host. Modulation of gene expression in response to environmental signals is an efficient mechanism used by bacteria to achieve this goal. Using DNA microarrays and a tissue culture model for gonococcal infection, we examined global changes in gene expression in N. gonorrhoeae in response to adherence to host cells. Among those genes induced upon adherence to human epithelial cells in culture was rpoH, which encodes a homolog of the heat shock sigma factor, sigma(32) (RpoH), as well as genes of the RpoH regulon, groEL and groES. Attempts to construct an rpoH null mutant in N. gonorrhoeae were unsuccessful, suggesting that RpoH is essential for viability of N. gonorrhoeae. The extracytoplasmic sigma factor, RpoE (sigma(E)), while known to regulate rpoH in other bacteria, was found not to be necessary for the up-regulation of rpoH in gonococci upon adherence to host cells. To examine the role of RpoH in host cell interactions, an N. gonorrhoeae strain conditionally expressing rpoH was constructed. The results of our experiments showed that while induction of rpoH expression is not necessary for adherence of gonococci to epithelial cells, it is important for the subsequent invasion step, as gonococci depleted for rpoH invade cells two- to threefold less efficiently than a wild-type strain. Taken together, these results indicate that sigma(32), but not sigma(E), is important for the response of gonococci in the initial steps of an infection.

Distinct defensin profiles in Neisseria gonorrhoeae and Chlamydia trachomatis urethritis reveal novel epithelial cell-neutrophil interactions

Defensins are key participants in mucosal innate defense. The varied antimicrobial activity and differential distribution of defensins at mucosal sites indicate that peptide repertoires are tailored to site-specific innate defense requirements. Nonetheless, few studies have investigated changes in peptide profiles and function after in vivo pathogen challenge. Here, we determined defensin profiles in urethral secretions of healthy men and men with Chlamydia trachomatis- and Neisseria gonorrhoeae-mediated urethritis by immunoblotting for the epithelial defensins HBD1, HBD2, and HD5 and the neutrophil defensins HNP1 to -3 (HNP1-3). HBD1 was not detectable in secretions, and HBD2 was only induced in a small proportion of the urethritis patients; however, HD5 and HNP1-3 were increased in C. trachomatis infection and significantly elevated in N. gonorrhoeae infection. When HNP1-3 levels were low, HD5 appeared mostly as the propeptide; however, when HNP1-3 levels were >10 microg/ml, HD5 was proteolytically processed, suggesting neutrophil proteases might contribute to HD5 processing. HD5 and HNP1-3 were bactericidal against C. trachomatis and N. gonorrhoeae, but HD5 activity was dependent upon N-terminal processing of the peptide. In vitro proteolysis of proHD5 by neutrophil proteases and analysis of urethral secretions by surface-enhanced laser desorption ionization substantiated that neutrophils contribute the key convertases for proHD5 in the urethra during these infections. This contrasts with the small intestine, where Paneth cells secrete both proHD5 and its processing enzyme, trypsin. In conclusion, we describe a unique defensin expression repertoire in response to inflammatory sexually transmitted infections and a novel host defense mechanism wherein epithelial cells collaborate with neutrophils to establish an antimicrobial barrier during infection.

Investigation of oxidative stress defenses of Neisseria gonorrhoeae by using a human polymorphonuclear leukocyte survival assay

Neisseria gonorrhoeae has well-characterized oxidative stress defense systems that protect against oxidative killing in in vitro assays. In contrast, mutant strains of N. gonorrhoeae lacking oxidative stress defenses are identical to the wild type when tested in an ex vivo survival assay using human polymorphonuclear leukocytes.

The gonococcal Fur-regulated tbpA and tbpB genes are expressed during natural mucosal gonococcal infection

Iron is limiting in the human host, and bacterial pathogens respond to this environment by regulating gene expression through the ferric uptake regulator protein (Fur). In vitro studies have demonstrated that Neisseria gonorrhoeae controls the expression of several critical genes through an iron- and Fur-mediated mechanism. While most in vitro experiments are designed to determine the response of N. gonorrhoeae to an exogenous iron concentration of zero, these organisms are unlikely to be exposed to such severe limitations of iron in vivo. To determine if N. gonorrhoeae expresses iron- and Fur-regulated genes in vivo during uncomplicated gonococcal infection, we examined gene expression profiles of specimens obtained from male subjects with urethral infections. RNA was isolated from urethral swab specimens and used as a template to amplify, by reverse transcriptase PCR (RT-PCR), gonococcal genes known to be regulated by iron and Fur (tbpA, tbpB, and fur). The constitutively expressed gonococcal rmp gene was used as a positive control. RT-PCR analysis indicated that gonorrhea-positive specimens where rmp expression was seen were also 93% (51/55) fbpA positive, 87% (48/55) tbpA positive, and 86% (14 of 16 tested) tbpB positive. In addition, we detected a fur transcript in 79% (37 of 47 tested) of positive specimens. We also measured increases in levels of immunoglobulin G antibody against TbpA (91%) and TbpB (73%) antigens in sera from infected male subjects compared to those in uninfected controls. A positive trend between tbpA gene expression and TbpA antibody levels in sera indicated a relationship between levels of gene expression and immune response in male subjects infected with gonorrhea for the first time. These results indicate that gonococcal iron- and Fur-regulated tbpA and tbpB genes are expressed in gonococcal infection and that male subjects with mucosal gonococcal infections exhibit antibodies to these proteins.

The anti-inflammatory compound curcumin inhibits Neisseria gonorrhoeae-induced NF-κB signaling, release of pro-inflammatory cytokines/chemokines and attenuates adhesion in late infection

Neisseria gonorrhoeae(Ngo) is a Gram-negative pathogenic bacterium responsible for an array of diseases ranging from urethritis to disseminated gonococcal infections. Early events in the establishment of infection involve interactions betweenNgoand the mucosal epithelium, which induce a local inflammatory response. Here we analyzed the molecular mechanism involved in theNgo-induced induction of the proinflammatory cytokines tumor necrosis factor α (TNFα), interleukin-6 (IL-6), and IL-8. We identified the immediate early response transcription factor nuclear factor κB (NF-κB) as a key molecule for the induction of cytokine release.Ngo-induced activation of direct upstream signaling molecules was demonstrated for IκB kinase α and β (IKKα and IKKβ) by phosphorylation of IκBα as a substrate and IKK autophosphorylation. Using dominant negative cDNAs encoding kinase-dead IKKα, IKKβ, and NF-κB-inducing kinase (NIK),Ngo-induced NF-κB activity was significantly inhibited. Curcumin, the yellow pigment derived fromCurcuma longa, inhibited IKKα, IKKβ and NIK, indicating its strong potential to block NF-κB-mediated cytokine release and the innate immune response. In addition to the inhibition ofNgo-induced signaling, curcumin treatment of cells completely abolished the adherence of bacteria to cells in late infection, underlining the high potential of curcumin as an anti-microbial compound without cytotoxic side effects.

A gonococcal efflux pump system enhances bacterial survival in a female mouse model of genital tract infection

Active efflux of antimicrobial substances is likely to be an important bacterial defense against inhibitory host factors inherent to different body sites. Two well-characterized multidrug resistance efflux systems (MtrCDE and FarAB-MtrE) exist in Neisseria gonorrhoeae, a bacterial pathogen of the human genital mucosae. In vitro studies suggest that the MtrCDE and FarAB-MtrE efflux systems protect the gonococcus from hydrophobic antimicrobial substances that are likely to be present on mucosal surfaces. Here we report that a functional MtrCDE efflux system, but not a functional FarAB-MtrE system, enhances experimental gonococcal genital tract infection in female mice. Specifically, the recovery of mtrD and mtrE mutants, but not a farB mutant, from mice inoculated with mutant or wild-type gonococci was reduced compared with that of the wild-type strain. Competitive-infection experiments confirmed the survival disadvantage of MtrCDE-deficient gonococci. This report is the first direct evidence that a multidrug resistance efflux system enhances survival of a bacterial pathogen in the genital tract. Additionally, experiments using ovariectomized mice showed that MtrCDE-deficient gonococci were more rapidly cleared from mice that were capable of secreting gonadal hormones. MtrCDE-deficient gonococci were more sensitive to nonphysiological concentrations of progesterone in vitro than were wild-type or FarAB-MtrE-deficient gonococci. These results suggest that progesterone may play an inhibitory role in vivo. However, hormonally regulated factors rather than progesterone itself may be responsible for the more rapid clearance of mtr-deficient gonococci from intact mice.

A co-operative interaction between Neisseria gonorrhoeae and complement receptor 3 mediates infection of primary cervical epithelial cells

Little is known about the pathogenesis of gonococcal infection within the lower female genital tract. We recently described the distribution of complement receptor 3 (CR3) on epithelia of the female genital tract. Our studies further indicate that CR3-mediated endocytosis serves as a primary mechanism by which N. gonorrhoeae elicits membrane ruffling and cellular invasion of primary, human, cervical epithelial cells. We have extended these studies to describe the nature of the gonococcus-CR3 interaction. Western Blot analysis demonstrated production of alternative pathway complement components by ecto- and endocervical cells which allows C3b deposition on gonococci and its rapid conversion to iC3b. Anti-iC3b and -factor I antibodies significantly inhibited adherence and invasion of primary cervical cells, suggesting that iC3b covalently bound to the gonococcus serves as a primary ligand for CR3 adherence. However, gonococcal porin and pili also bound to the I-domain of CR3 in a non-opsonic manner. Binding of porin and pili to CR3 were required for adherence to and invasion of cervical epithelia. Collectively, these data suggest that gonococcal adherence to CR3 occurs in a co-operative manner, which requires gonococcal iC3b-opsonization, porin and pilus. In conjunction, these molecules facilitate targeting to and successful infection of the cervical epithelium.

Increased adhesiveness and internalization of Neisseria gonorrhoeae and changes in the expression of epithelial gonococcal receptors in the Fallopian tube of copper T and Norplant users

Interaction of Neisseria gonorrhoeae with the oviductal epithelium in vitro was examined in 2 cm length segments obtained after surgical sterilization from users of copper T intrauterine device (IUD) or Norplant and control women. Segments perfused with N.gonorrhoeae suspensions were incubated from 30 min up to 4 h, fixed, frozen and cut in 6--10 microm sections. Bacteria were detected immunohistochemically with rabbit anti-gonococcal serum followed by light and confocal microscopy. Adhesion and internalization of gonococci by epithelial cells were observed at all incubation times, and both were higher in explants from users of copper T IUD or Norplant implants than controls. The epithelium of controls expressed CD66 and syndecan-1; but CD46 was found in only one out of six cases. The epithelium of copper T IUD users expressed CD66 but not syndecan-1 or CD46. Users of Norplant exhibited expression of CD46, CD66 and syndecan-1. Label was always found along the luminal border of the epithelium. There were more intraepithelial lymphocytes in users of contraceptive methods than in controls. Results indicate that (i) N.gonorrhoeae invade the oviductal epithelium from the first minutes of exposure, (ii) the epithelium is constitutively endowed with two known receptors for the gonococcus, CD66 and syndecan-1, (iii) copper T IUD and Norplant users exhibit higher rates of attachment and internalization of the gonococcus into the oviductal epithelium associated with changes in expression of gonococcal receptors.

Interaction of primary human endometrial cells with Neisseria gonorrhoeae expressing green fluorescent protein

Infection of the endometrium by Neisseria gonorrhoeae is a pivotal stage in the development of pelvic inflammatory disease in women. An ex vivo model of cultures of primary human endometrial cells was developed to study gonococcal-host cell interactions. To facilitate these studies, gonococci were transformed with a hybrid shuttle vector containing the gfp gene from Aequoria victoria, encoding the green fluorescent protein (GFP), to produce intrinsically fluorescent bacteria. The model demonstrated that both pili and Opa proteins were important for both mediating gonococcal interactions with endometrial cells and inducing the secretion of pro-inflammatory cytokines and chemokines. Pil+ gonococci showed high levels of adherence and invasion, regardless of Opa expression, which was associated with increased secretion of IL-8 chemokine and reduced secretion of IL-6 cytokine. Gonococcal challenge also caused increased secretion of TNF-alpha cytokine, but this did not correlate with expression of pili or Opa, suggesting that release of components from non-adherent bacteria may be involved in TNF-alpha induction. Thus, the use of cultured primary endometrial cells, together with gonococci expressing green fluorescent protein, has the potential to extend significantly our knowledge, at the molecular level, of the role of this important human pathogen in the immunobiology of pelvic inflammatory disease.

Experimental gonococcal genital tract infection and opacity protein expression in estradiol-treated mice

The development of effective prophylactic agents against gonorrhea and the study of adaptation by Neisseria gonorrhoeae to the urogenital mucosa are hindered by the lack of a well-established animal model of gonococcal genital tract infection. Here, a murine model of long-term gonococcal genital tract infection is described. Female BALB/c mice were treated with 17-beta-estradiol and inoculated intravaginally with wild-type gonococcal strain FA1090 or MS11. N. gonorrhoeae was recovered from vaginal swabs for an average of 12 to 13 days following inoculation with 10(6) CFU of either strain. Inflammation occurred in over 80% of infected mice, and diplococci were associated with epithelial cells and neutrophils in stained vaginal smears. Ascended infection occurred in 17 to 20% of mice inoculated with strain FA1090. An outbred mouse strain (SLC:ddY) previously reported to be naturally susceptible to N. gonorrhoeae was also tested; however, as with BALB/c mice, estradiol was required for prolonged infection. Although piliation was not maintained during experimental murine infection, 46 to 100% of vaginal isolates from four of eight BALB/c mice and three of four SLC:ddY mice expressed one or more opacity (Opa) proteins within 4 days after inoculation with an Opa-negative variant of strain FA1090. The observed selection for and/or induction of gonococcal Opa protein expression during murine infection appears to parallel events that occur during experimental urethritis in volunteers.

Gonococcal infection of human fallopian tube mucosa in organ culture: relationship of mucosal tissue TNF-alpha concentration to sloughing of ciliated cells

BACKGROUND AND OBJECTIVES

An experimental model consisting of gonococcal infection of human fallopian tube mucosa in organ culture has proven useful in studying the molecular pathogenesis of acute gonococcal salpingitis and postsalpingitis sequelae. Gonococcal infection of human fallopian tube mucosa in organ culture results in the sloughing of ciliated epithelial cells from the mucosa. This damage to the mucosa can be quantified on fallopian tube pieces by an assay of the percent of the periphery that has ciliary activity (PPCA) remaining at specific time points after infection. Although assay of the PPCA has been quite valuable, it is labor-intensive, somewhat subjective, and requires that the observers have training and experience. A more practical assay for genital mucosal damage is desirable for further investigations that employ the fallopian tube experimental model. Gonococcal infection of fallopian tube mucosa in organ culture also results in the production of easily quantified tumor necrosis factor-alpha (TNF-alpha) by the mucosa. Furthermore, treatment of the organ cultures with recombinant human TNF-alpha (rHuTNFalpha) alone also causes sloughing of ciliated cells from the mucosa. These findings strongly suggest that TNF-alpha is a mediator of the mucosal damage that attends gonococcal infection.

GOALS OF THE STUDY

To determine: (1) whether the PPCA values and the TNF-alpha concentrations in fallopian tube mucosal tissues correlate closely enough to allow prediction of the PPCA from a measurement of the mucosal tissue TNF-alpha concentration; and (2) whether the correlation of the TNF-alpha mucosal tissue concentration with the sloughing of ciliated cells (measured by the PPCA) supports the hypothesis that induction of TNF-alpha by gonococcal infection, with resultant sloughing of ciliated cells, is likely to be a major pathogenic mechanism of gonococcal salpingitis and might mediate postsalpingitis infertility and ectopic pregnancy.

STUDY DESIGN

A metaanalysis was performed on studies from three research groups (two laboratories in the United States and one in the United Kingdom, using identical techniques for quantifying the PPCA, TNF-alpha, or both.

RESULTS

There was a close and statistically significant correlation between the TNF-alpha mucosal tissue concentration and the proportion of ciliated cells lost from the mucosa as measured by the PPCA (r = 0.95, p < 0.001). Therefore, as the mucosal tissue concentration of endogenous TNF-alpha increased, the loss of ciliated cells from the epithelium increased proportionately.

CONCLUSIONS

During gonococcal infection of human fallopian tube mucosa in organ culture, the mucosal tissue concentration of TNF-alpha can be used to predict the PPCA, and therefore, the extent of mucosal damage. This finding should facilitate studies of the molecular pathogenesis of infectious diseases involving human genital mucosa. Further, the close correlation of mucosal TNF-alpha concentration with genital mucosal damage, evaluated by the PPCA, supports the hypothesis that induction of the proinflammatory cytokine, TNF-alpha, by gonococcal infection, with resultant inflammation and sloughing of ciliated cells, is an important pathogenic mechanism of gonococcal salpingitis and may mediate postsalpingitis infertility and ectopic pregnancy as well.

Evaluation of immunoglobulin A1 (IgA1) protease and IgA1 protease-inhibitory activity in human female genital infection with Neisseria gonorrhoeae

Immunoglobulin A1 (IgA1) protease, an enzyme that selectively cleaves human IgA1, may be a virulence factor for pathogenic organisms such as Neisseria gonorrhoeae. Host protection from the effects of IgA1 protease includes antibody-mediated inhibition of IgA1 protease activity, and it is believed that the relative balance between IgA1 protease and inhibitory antibodies contributes to the pathogenesis of disease caused by IgA1 protease-producing organisms. We have examined the levels of these two opposing factors in genital tract secretions and sera from women with uncomplicated infection with N. gonorrhoeae. When IgA1 in cervical mucus was examined by Western blotting, no evidence of cleavage fragments characteristic of IgA1 protease activity was seen in gonococcus-infected or control patients. Cleavage fragments typical of IgA1 protease were detected, however, after the addition of exogenous IgA1 protease to cervical mucus. Degraded IgA1 was detected in some vaginal wash samples, but the fragment pattern was not typical of IgA1 protease activity. All N. gonorrhoeae isolates from the infected patients produced IgA1 protease in vitro. All but two serum samples and 16 of 65 cervical mucus samples displayed inhibitory activity against gonococcal IgA1 protease, but there was no significant difference in the level of inhibitory activity between gonococcus-infected and noninfected patients in either cervical mucus or serum. There was no difference in the levels of IgA1 protease-inhibitory activity in serum or cervical mucus collected from patients at recruitment and 2 weeks later. These results suggest that cleavage of IgA1 by gonococcal IgA1 protease within the lumen of the female lower genital tract is unlikely to be a significant factor in the pathogenesis of infections by N. gonorrhoeae.

Influence of ovarian hormones on urogenital infection

Numerous studies have examined the influence of hormones on infectious diseases and there is now a wealth of data relating to the more specific effect of the sex hormones, oestrogen and progesterone, on urogenital infections. The interaction between these hormones and the immune system is complex and the variation of hormonal effect between species further complicates the true picture as related to humans. Although it is difficult therefore to draw general conclusions regarding predominant effects of specific hormones, there is the suggestion that oestrogen enhances the pathogenicity of many urogenital micro-organisms. Our understanding of the influential role played by sex hormones in disease pathogenesis is at an early stage and illustrates well the importance of drawing together and interpreting as a whole both epidemiological and molecular studies.

Natural proteoglycan receptor analogs determine the dynamics of Opa adhesin-mediated gonococcal infection of Chang epithelial cells

Many bacterial pathogens possess a complex machinery for the induction and/or secretion of factors that promote their uptake by mammalian cells. We searched for the molecular basis of the 60- to 90-min lag time in the interaction of Neisseria gonorrhoeae carrying the heparin-binding Opa adhesin with Chang epithelial cells. Infection assays in the presence of chloramphenicol demonstrated that the Opa-mediated gonococcal infection of Chang cells required bacterial protein synthesis when the microorganisms were derived from GC agar but not when grown in liquid media. Further analysis indicated that contact with agar ingredients rather than the growth state of the microorganisms determined the infection dynamics. DEAE chromatography of GC agar extracts and sodium dodecyl sulfate-polyacrylamide gel electrophoresis analyses and testing of collected fractions in infection assays identified negatively charged high-molecular-weight polysaccharides in the agar as inhibitors of the cellular infection. Electron microscopy showed that agar-grown gonococci were surrounded by a coat of alcian blue-positive material, probably representing accreted polysaccharides. Similar antiphagocytic material was isolated from bovine serum, indicating that in biological fluids gonococci producing the heparin-binding Opa adhesin may become covered with externally derived polysaccharides as well. Binding assays with gonococci and epithelial proteoglycan receptors revealed that polysaccharides derived from agar or serum compete with the proteoglycans for binding of the heparin-binding Opa adhesin and thus act as receptor analogs. Growth of gonococci in a polysaccharide-free environment resulted in optimal proteoglycan receptor binding and rapid bacterial entry into Chang cells. The recognition that gonococci with certain phenotypes can recruit surface polysaccharides that determine in vitro infection dynamics adds a different dimension to the well-recognized biological significance of genetic variation for this pathogen.

Expression of paragloboside-like lipooligosaccharides may be a necessary component of gonococcal pathogenesis in men

To learn how lipooligosaccharide (LOS) phase variations affect pathogenesis, we studied two male volunteers who were challenged intraurethrally with Neisseria gonorrhoeae that make a single LOS of 3,600 daltons and sequentially followed LOS expression by gonococci as urethritis developed. LOS variation occurred in vivo. Signs and symptoms of gonorrhea began with the appearance of variants making 4,700-dalton LOS that are immunochemically similar to glycosphingolipids of human hematopoietic cells (Mandrell, R.E., J.M. Griffiss, and B.A. Macher. 1989. J. Exp. Med. 168:107) and that have acceptors for sialic acid. A variant that appeared at the onset of leukorrhoea was shed by 34/36 men with naturally acquired gonorrhea at the time they sought medical attention; the other two shed the variant associated with dysuria. None shed the challenge variant. These data show that in vivo phase shifts to higher molecular mass LOS that mimic human cell membrane glycolipids are associated with the development of gonococcal leukorrhea.

Heterosexual gonorrhoea in central Sydney: implications for HIV control

Gonorrhoea is a sexually transmissible disease (STD) characteristic of a core group of individuals and their contacts. From the experience of a Sydney STD clinic, as well as local and national population-based reports, trends in heterosexually acquired gonorrhoea in Australia over a decade were examined. An overall decline of 90% in case numbers between 1981 and 1989 was found, with an average yearly decline of 30%. The improved compliance with condom use by Sydney prostitutes and their clients could have been a major factor. This occurred in an environment of peer and public education about AIDS and the decriminalisation of prostitution. Improved health professional training and public access to specialist STD services against a background of demographic changes may also have contributed. However a persistent "seeding" of penicillinase-producing strains of gonorrhoea from Southeast Asia through men not using condoms was detected. These data have potential implications for the importation of heterosexually acquired human immunodeficiency virus infection into Australia.

Expression of outer membrane protein II by gonococci in experimental gonorrhea

Gonorrheal urethritis was induced in three males by intraurethral instillation of predominantly pilus+ protein II- gonococci. Virtually all gonococci reisolated from the infected men exhibited protein II+ phenotype. The reisolated gonococci expressed five distinct outer membrane protein II species. Protein IIc+ organisms predominated in urines of all three subjects, but variants expressing this particular protein II were rarely spawned in vitro by input organisms. Protein IIc+ gonococci appeared early in one man's infection; they were joined later by variants that displayed eight other protein II phenotypes, including protein II-. These results show that input protein II- gonococci are supplanted by protein IIc+ variants during incipient gonorrheal urethritis. As infection progresses, a broader variety of protein II+ variants appears.

Synovial fluid lactate levels in septic and non-septic arthritides

Lactate concentration was studied in 383 synovial fluid specimens from patients with various arthritides. The highest concentrations of lactate occurred in non-gonococcal septic synovial fluids. High values were recorded in seropositive rheumatoid arthritis and crystal-induced arthritides, medium values in synovial fluids from seronegative rheumatoid arthritis, seronegative spondylarthritides, gonococcal arthritis and haemarthrosis, and the lowest values in aspirates from osteoarthrotic joints. There was a positive correlation between synovial pH and lactic acid concentration. These data suggest that determination of lactate in synovial fluid can be valuable in the rapid exclusion of septic arthritis. Its value for differentiating between other inflammatory arthritides is discussed.

The treatment of gonorrhoea--beta lactamase producers

The high endemicity of PPNG in some regions preclude the continued routine use of procaine penicillin as treatment for gonorrhoea. The aminoglycosides, spectinomycin, second and third generation cephalosporins are highly effective and on epidemiological grounds, should replace penicillin as the first choice antibiotic. However, due cognizance has to be given to the impact of this recommendation on the non PPNG strains and the development of chromosomal resistance to the latter antibiotics. Also, the discontinuation of penicillin as the first line drug for gonorrhoea may see a resurgence of early syphilis. All future recommendations on the treatment of gonorrhoea should take these factors into consideration. Synergetic combination of beta lactam antibiotics and beta lactamase inhibitors or combination therapy may be the lines along which future research should head.

Turnover in the transferrin iron pool during the hypoferremic phase of experimental Neisseria meningitidis infection in mice

Mouse transferrin was used to specifically label the plasma transferrin iron pool for studies of iron kinetics in normal mice and infected mice during the hypoferremic phase of experimental meningococcal infection. The plasma transferrin iron pool of normal mice was found to be very dynamic, with a half-life of iron in the pool of 0.7 h. Iron left the plasma pool, entered the bone marrow, and was released into the blood in erythrocytes. Iron from the transferrin pool also entered the liver and spleen and was presumably in the reticuloendothelial system components of these organs. Most of the iron that had been supplied as transferrin iron was found in erythrocytes by 48 h after injection. Studies with mice infected with Neisseria meningitidis strain M1011 revealed similar kinetics for transferrin iron. There was no redistribution of iron within the various iron pools as a result of infection. Iron turnover in the plasma transferrin pool during the hypoferremic phase was similar to control rates, and iron leaving the pool entered its normal erythroid compartments. The lack of accelerated turnover of plasma iron and the finding that plasma iron was not rerouted to storage compartments during the hypoferremic phase provided good evidence that lactoferrin and leukocytic endogenous mediator were not directly involved in redirecting transferrin iron. Our evidence has implicated an impaired return of reticuloendothelial system-processed iron to the transferrin pool during the hypoferremic response. This appears to be a logical point in the erythroid iron cycle for host-mediated iron sequestration, as the reticuloendothelial system is involved in iron storage and may regulate iron levels in the plasma transferrin pool under normal conditions.

Comparative study of bacampicillin and ampicillin in the treatment of uncomplicated gonorrhoea

Bacampicillin hydrochloride, a pro-drug ester of ampicillin trihydrate which is hydrolysed to ampicillin after absorption, was used in a randomised comparative study of ampicillin 3.5 g and bacampicillin 1.6g (each with probenecid 1 g) in the treatment of uncomplicated gonorrhoea. This dose of bacampicillin was selected because in serum it gives approximately the same peak concentration of ampicillin as 3.5 g of the present drug. Genital, pharyngeal, and anal cultures were performed at the initial visit and at follow up 5-9 days after treatment. There was no statistically significant difference in the microbiological or clinical response of patients with genital gonorrhoea who were treated with ampicilin and those treated with bacampicillin. At 5-9 days after treatment, 93% of the ampicillin-treated patients and 89% of the bacampicillin-treated patients had negative genital, pharyngeal, and anal culture results; furthermore, 87% and 89% respectively had no symptoms of infection. Fewer gastrointestinal side effects were noted in the patients treated with bacampicillin.

Synovial fluid lactic acid. A diagnostic aid in septic arthritis

Lactic acid concentrations in the synovial fluid of 84 patients with acute monoarticular arthritis were determined by gas liquid chromatography. Lactic acid values in 27 cases of nongonococcal septic arthritis were strikingly higher (mean 1170 mg/100ml) than in 45 cases of inflammatory or degenerative arthritis (mean 34 mg/100 ml), as well as in 12 cases of gonococcal arthritis (mean 27 mg/100 ml). With the proper equipment, determination of lactic acid can be a relatively rapid, reliable procedure. Synovial fluid lactic acid concentrations therefore can be used as a rapid, supplemental diagnostic aid in differentiating nongonococcal septic arthritis from both gonococcal and nonseptic acute arthritis.

Role of iron in disseminated gonococcal infections

Strains of Neisseria gonorrhoeae isolated from disseminated gonococcal infections have enhanced ability to acquire iron in an experimental host when compared with urogenital gonococcal isolates from patients with uncomplicated infections.

Magnesium and zinc in seminal fluid of healthy males and patients with non-acute prostatitis with and without gonorrhoea

The concentrations of magnesium and zinc in the seminal fluid of 41 patients with symptoms of non-acute prostatitis and of 11 healthy age-matched males were determined by atomic absorption spectrophotometry. Possible sources of error in the determination of these metals in seminal fluid are discussed. The mean concentration of magnesium in the patients was 56.6 mug/ml (range 19-190) and in the controls 64.5 mug/ml (range 36-165). The corresponding figures for zinc were 79.2 mug/ml (range 13-283) and 67.5 mug/mg (range 34-116). Both in the patients and in the controls there was a significant correlation between the concentration of magnesium and that of zinc. No significant difference was found between the patients and the controls regarding the concentration of magnesium or zinc. From none of the patients could gonococci be cultured. However, in 6 of them, immunofluorescent studies revealed gonococci. The concentration of zinc (48.3 mug/ml) in seminal fluid from these 6 patients was significantly lower than in the remaining 35. Neither in the patients, nor in the controls, was any correlation found between the concentration of magnesium or zinc and that of fructose in seminal fluid. A significant correlation was found between the concentrations of these metals and the antibacterial activity (determined as the inhibitory effect on the growth of Staphylococcus albus) of the seminal fluid from the patients. A negative correlation was found between the concentration of zinc and an increase in the number of white blood cells in expressed prostatic fluid. No correlation was found between magnesium or zinc and the number of spermatozoa or the percentage of abnormal spermatozoa. The findings in the present study suggest that the secretion of magnesium and zinc is decreased in prostatitis. Because of the wide range of variation of magnesium and zinc in seminal fluid of healthy males, determination of these metals is of limited value in the diagnoses of prostatitis in a given case.