The Role of the Insulin/Glucose Ratio in the Regulation of Pathogen Biofilm Formation

During the management of patients in acute trauma the resulting transient hyperglycemia is treated by administration of insulin. Since the effect of insulin, a quorum sensing compound, together with glucose affects biofilm formation in a concentration-specific manner, we hypothesize that the insulin/glucose ratio over the physiologic range modulates biofilm formation potentially influencing the establishment of infection through biofilm formation.

METHODS

A variety of Gram-positive and Gram-negative bacteria were grown in peptone (1%) yeast nitrogen base broth overnight in 96-well plates with various concentrations of glucose and insulin. Biofilm formation was determined by the crystal violet staining procedure. Expression of insulin binding was determined by fluorescent microscopy (FITC-insulin). Controls were buffer alone, insulin alone, and glucose alone.

RESULTS

Overall, maximal biofilm levels were measured at 220 mg/dL of glucose, regardless of insulin concentration (10, 100, 200 µU/mL) of the organism tested. In general, insulin with glucose over the range of 160-180 mg/dL exhibited a pattern of biofilm suppression. However, either above or below this range, the presence of insulin in combination with glucose significantly modulated (increase or decrease) biofilm formation in a microbe-specific pattern. This modulation appears for some organisms to be reflective of the glucose-regulated intrinsic expression of bacterial insulin receptor expression.

CONCLUSION

Insulin at physiologic levels (normal and hyperinsulinemic) in combination with glucose can affect biofilm formation in a concentration-specific and microbe-specific manner. These findings may provide insight into the importance of co-regulation of the insulin/glucose ratio in patient management.

Reemergence of the Murine Bacterial Pathogen Chlamydia muridarum in Research Mouse Colonies

Chlamydia muridarum (Cm) was detected in 2 colonies of mice with lymphoplasmacytic pulmonary infiltrates by using PCR and immunohistochemistry. This discovery was unexpected, as Cm infection had not been reported in laboratory mice since the 1940s. A Cm specific PCR assay was developed and testing implemented for the resident colonies of 8 vivaria from 3 academic institutions, 58 incoming mouse shipments from 39 academic institutions, and mice received from 55 commercial breeding colonies (4 vendors). To estimate Cm's global prevalence in research colonies, a database containing 11,387 metagenomic fecal microbiota samples from 120 institutions and a cohort of 900 diagnostic samples from 96 institutions were examined. Results indicate significant prevalence among academic institutions, with Cm detected in 63% of soiled bedding sentinels from 3 institutions; 33% of incoming mouse shipments from 39 academic institutions; 14% of 120 institutions submitting microbiota samples; and 16% of the diagnostic sample cohort. All samples from commercial breeding colonies were negative. In addition, naïve NOD. Cg-Prkdc^scidIl2rg^tm1Wjl/SzJ (NSG) mice exposed to Cm-shedding mice and/or their soiled bedding developed clinical disease at 21 to 28 d after exposure. These mice had a moderate-to-severe histiocytic and neutro- philic bronchointerstitial pneumonia, with their respiratory epithelium demonstrating inclusions, chlamydial major outer membrane protein immunostaining, and hybridization with a Cm reference sequence (GenBank accession no. U68436). Cm was isolated from lungs, cecum, and feces of a Cm-infected NSG mouse by using HeLa 229 cells. The considerable prevalence of Cm is likely due to widespread global interinstitutional distribution of unique mouse strains and failure to recognize that some of these mice were from enzootically infected colonies. Given that experimental Cm colonization of mice results in a robust immune response and, on occasion, pathology, natural infection may confound experimental results. Therefore, Cm should be excluded and eradicated from enzootically infected mouse colonies.

Anaerobic Growth and Maintenance of Mammalian Cell Lines

Most mucosal surfaces along with the midpoints in tumors and stem cell niches are geographic areas of the body that are anoxic. Previous studies show that the incubation in normoxic (5% CO2 in air) or hypoxic (low oxygen levels) conditions followed by an anoxic incubation (an absence of free oxygen) results in limited viability (2-3 days). A novel methodology was developed that enables an anoxic cell cultivation (for at least 17 days; the maximum time tested). The most critical aspect of this methodology is to ensure that no oxygen is introduced into the system. This is obtained by the degassing of media, and by flushing tubes, dishes, flasks, and pipettes with an anaerobic gas mixture (H2, CO2, N2) followed by permitting the materials to equilibrate to the anoxic (non-oxygen) environment prior to usage. Additional care must be exercised when acquiring photomicrographs to ensure that the micrographs obtained do not contain artifacts. In the absence of oxygen, cell morphology is significantly altered. Two distinct morphotypes are noted for all anaerobically-grown cells. The ability to grow and maintain mammalian cells in the absence of oxygen can be applied to the analysis of cell physiology, polymicrobial interactions, and the characterization of biosynthetic pathways for novel cancer drug development.

Differential expression of cytokines and receptor expression during anoxic growth

Objective

Cell density in tumor cell three dimensional (3D) cultures affects secretome expression of components. A microenvironment characteristic shared by high-density 3D cell culture and in vivo tumor masses is poor oxygenation, with anoxia being a natural cell state in tumor centers. Until recently, the ability to study anoxia-adapted cell physiology was not possible. Using a newly-developed methodology, anoxic HeLa cell secretome expression was measured.

Results

Anoxic HeLa cell cytokine levels after 3 days’ (hypoxia inducible factor, HIF1 positive) and 10 days’ growth (HIF1 negative; anaerobic respiration) were significantly (p < 0.01) higher than normoxic controls for: IL-8 (1.8- and 3.4-fold higher, respectively), GRO (1.3- and 1.1-fold higher, respectively), and IL-11 (1.4- and 1.1-fold higher, respectively). In contrast, G-CSF, IFNα2, and CXCL-10 levels decreased over time (day 3 vs. day 10). Thus, metabolically active HeLa cells respond to the lack of oxygen, in part, by regulating the levels of cytokines produced. Cytokines expressed at increased levels, in the absence of oxygen, correspond to a secretomic profile reported for paracrine signaling pathways associated with metastasis. Further studies defining physiologic changes that occur upon anoxic growth may lead to the discovery of novel chemotherapeutic drug targets.

Electronic supplementary material

The online version of this article (10.1186/s13104-018-3520-5) contains supplementary material, which is available to authorized users.

Elimination of Mycoplasma contamination in Chlamydia stocks as a result of in vivo passage or plaque isolation

OBJECTIVE

This study aims to eliminate Mycoplasma spp. contamination from laboratory stocks of Chlamydia spp. by in vivo passage or by plaque assay.

RESULTS

We have described two methods of eliminating Mycoplasma contamination from Chlamydia laboratory stocks. We conclude that Mycoplasma species commonly contaminating chlamydial stocks do not survive passage in mice. Chlamydia may also be derived Mycoplasma-free by plaque assay.

A method for the long-term cultivation of mammalian cells in the absence of oxygen: Characterization of cell replication, hypoxia-inducible factor expression and reactive oxygen species production

The center of tumors, stem cell niches and mucosal surfaces all represent areas of the body that are reported to be anoxic. However, long-term study of anoxic cell physiology is hindered by the lack of a sustainable method permitting cell cultivation in the complete absence of oxygen. A novel methodology was developed that enabled anoxic cell cultivation (17d maximum time tested) and cell passage. In the absence of oxygen, cell morphology is significantly altered. All cells tested exhibited morphologic changes, i.e., a combination of tethered (monolayer-like) and runagate (suspension-like) morphologies. Both morphologies replicated (Vero and HeLa cells tested) and could be passaged anaerobically. In the absence of exogenous oxygen, anoxic cells produced reactive oxygen species (ROS). Anaerobic runagate HeLa and Vero cells increased ROS production from day 3 to day 10 by 2- and 3-fold, respectively. In contrast, anoxic tethered HeLa and Vero cells either showed no significant change in ROS production between days 3 and 10 or exhibited a 3-fold decrease in ROS, respectively. Detection of ROS was inversely related to detection of hypoxia-inducible factor-1α (HIF1) mRNA and HIF-1 protein expression which cycled over a 10-day period. This methodology has broad applications for the study of tumor and stem cell physiology as well as gastrointestinal cell-microbiome interactions. In addition, sustainable anaerobic cell culture may lead to the identification of novel pathways and targets for chemotherapeutic drug development.

Determination of Biofilm Initiation on Virus-infected Cells by Bacteria and Fungi

The study of polymicrobial interactions across the taxonomic kingdoms that include fungi, bacteria and virus have not been previously examined with respect to how viral members of the microbiome affect subsequent microbe interactions with these virus-infected host cells. The co-habitation of virus with bacteria and fungi is principally present on the mucosal surfaces of the oral cavity and genital tract. Mucosal cells, particularly those with persistent chronic or persistent latent viral infections, could have a significant impact on members of the microbiome through virus alteration in number and type of receptors expressed. Modification in host cell membrane architecture would result in altered ability of subsequent members of the normal flora and opportunistic pathogens to initiate the first step in biofilm formation, i.e., adherence. This study describes a method for quantitation and visual examination of HSV's effect on the initiation of biofilm formation (adherence) of S. aureus and C. albicans.

Detection of Chlamydia infection in Peromyscus species rodents from sylvatic and laboratory sources

To determine if Chlamydia muridarum, or other chlamydiae, are enzootic in rodents, we probed a serum bank of wild Peromyscus spp. mice for immunoglobulin G-antibody reactivity to ultraviolet light-inactivated C. muridarum elementary bodies (EBs) using an enzyme-linked immunoassay. Applying a cut-off for a positive reaction of OD(405) nm = 0.1 at a 1:20 dilution, we found titratable antibody reactivity in 190 of 247 specimens surveyed (77%, mean OD(405) = 0.33 ± 0.26, range = 0.11-1.81, median = 0.25). In addition, serum samples were obtained from a colony of specific pathogen-free Peromyscus spp. maintained at the University of South Carolina and six of 12 samples were reactive (50%, mean OD(405) = 0.19 +/- 0.08, range = 0.1-0.32, median = 0.18). Lastly, 40 additional wild Peromyscus spp. were captured in a disparate region of Midwestern USA and 22 serum specimens were reactive (55%, mean OD(405) = 0.22 +/- 0.11, range = 0.1-0.48, median = 0.2). Specificity of selected reactive sera for chlamydial antigen was confirmed on Western blot using resolved purified EBs as the detecting antigen. From tissues removed from several mice at necropsy, the gene for chlamydial 16S ribosomal ribonucleic acid (rRNA) was amplified by polymerase chain reaction (PCR). Positive samples of 16S rRNA were subjected to additional PCR for the major outer membrane protein gene (ompA). The amplicons of three select ompA positive samples were sequenced with ≥99% homology with C. muridarum. Our findings indicate that chlamydial infection is enzootic for Peromyscus spp., and that C. muridarum, or a closely related species or strain, is likely the agent in the tested rodent species.

Genomic variant representation in a Chlamydia population is dynamic and adaptive with dependence on in vitro and in vivo passage

We have previously shown that Chlamydia muridarum has multiple genomic variants that concomitantly vary in their in vitro and in vivo phenotype. Herein, we used real-time polymerase chain reaction-based genotyping assays to query plaque-cloned isolates of C. muridarum for the frequency of eight selected polymorphisms. These strains had no history of passage in vivo since their original isolation from laboratory mice. There was significant variance in the frequency of two of the eight polymorphisms assessed with the remaining exhibiting a low rate of variance. To determine if any of these polymorphisms were more favorable for in vivo conditions, we blindly passaged non-clonal C. muridarum three times at 7-day intervals through the urogenital tract of mice. Seven of the eight polymorphisms varied in frequency following in vivo passage and four of these varied between C. muridarum strains. Selected isolates displayed variable growth rates and cytopathic effect in vitro. We conclude that multiple genotypic variants are present within the existing known C. muridarum strains and that the frequency of these variants changes upon introduction into the mouse host. These findings lend support to the concept that genotypic proportional representation in a chlamydial population is dynamic and adaptive.

Plasmid deficiency in urogenital isolates of Chlamydia trachomatis reduces infectivity and virulence in a mouse model

We hypothesized that the plasmid of urogenital isolates of Chlamydia trachomatis would modulate infectivity and virulence in a mouse model. To test this hypothesis, we infected female mice in the respiratory or urogenital tract with graded doses of a human urogenital isolate of C. trachomatis, serovar F, possessing the cognate plasmid. For comparison, we inoculated mice with a plasmid‐free serovar F isolate. Following urogenital inoculation, the plasmid‐free isolate displayed significantly reduced infectivity compared with the wild‐type strain with the latter yielding a 17‐fold lower infectious dose to yield 50% infection. When inoculated via the respiratory tract, the plasmid‐free isolate exhibited reduced infectivity and virulence (as measured by weight change) when compared to the wild‐type isolate. Further, differences in infectivity, but not in virulence were observed in a C. trachomatis, serovar E isolate with a deletion within the plasmid coding sequence 1 when compared to a serovar E isolate with no mutations in the plasmid. We conclude that plasmid loss reduces virulence and infectivity in this mouse model. These findings further support a role for the chlamydial plasmid in infectivity and virulence in vivo.

Role of heparan sulfate in sexually transmitted infections

Cell surface heparan sulfate (HS), a polysaccharide composed of alternating uronic acid and glucosamine residues, represents a common link that many sexually transmitted infections (STIs) require for infection. Variable modifications within the monomeric units of HS chains together with their unique structural conformations generate heterogeneity, which expands the ability of HS to bind a diverse array of host and microbial proteins. Recent advances made in the field of glycobiology have critically enhanced our understanding of HS and its interactions with microbes and their significance in important human diseases. The role of HS has been elaborated for several STIs to include those caused by herpes simplex virus, human immunodeficiency virus, human papillomavirus, and Chlamydia. In addition, gonorrhea, syphilis, and yeast infections are also dependent on the presence of HS on human target cells. Critical steps such as pathogen adhesion or binding to host cells followed by internalization to enhance intracellular survival and possible spread to other cells are mediated by HS. In addition, HS guided cell signaling plays a role in the development of angiogenesis and inflammation associated with many STIs. Past and ongoing investigations are providing new push for the development of HS-mimetics and analogs as novel prevention strategies against many different STIs. This review article summarizes the significance of HS in STIs and describes how emerging new products that target HS can be used to control the spread of STIs.

A role for CXC chemokine receptor-2 in the pathogenesis of urogenital Chlamydia muridarum infection in mice

We tested the hypothesis that a specific chemokine receptor, CXC chemokine receptor-2 (CXCR2), mediates acute inflammatory damage during chlamydial urogenital infection, which ultimately leads to the chronic sequelae of hydrosalpinx - a surrogate marker of infertility. Homozygous CXCR2 genetic knockouts (CXCR2-/-), heterozygous littermates (CXCR2+/-) or homozygous wild-type (wt) controls (CXCR2+/+) were infected intravaginally with Chlamydia muridarum. Although no change was observed in the infection in the lower genital tract based on CXCR zygosity, a delay in the ascension of infection into the upper genital tract was seen in CXCR2-/- mice. Significantly elevated peripheral blood neutrophil counts were observed in CXCR2-/- mice when compared with controls. Reduced rates of acute inflammatory indices were observed in the affected tissue, indicating reduced neutrophil extravasation capacity in the absence of CXCR2. Of note was a reduction in the postinfection development of hydrosalpinx that correlated with CXCR2 zygosity, with both CXCR2-/- (13%) and their CXCR2+/- (35%) littermates displaying significantly lower rates of hydrosalpinx formation than the wt CXCR2-sufficient mice (93%). We conclude that CXCR2 ligands are a major chemotactic signal that induces damaging acute inflammation and the resulting chronic pathology during the repair phase of the host response, but are dispensable for the resolution of infection.

A link between neutrophils and chronic disease manifestations of Chlamydia muridarum urogenital infection of mice

Vigorous acute inflammatory responses accompany Chlamydia muridarum infections in mice and are positively correlated with adverse urogenital and respiratory tract infection outcomes in the mouse model. Thus, we tested the hypothesis that neutrophils induce an acute inflammatory insult that, in the repair phase, leads to the chronic sequelae of hydrosalpinx - a surrogate marker of infertility in the mouse model. To this end, we induced neutropenia in mice using a neutrophil-depleting monoclonal antibody during acute phases of C. muridarum urogenital infection only (days 2-21 postinfection). To prove induced neutropenia, peripheral blood was monitored for neutrophils during the treatment regimen. Neutropenic mice had a similar infection course as control mice, but had significantly reduced levels of certain histopathological parameters, reduced production of matrix metalloproteinase-9 (MMP-9) and reduced rates of hydrosalpinx following resolution of the infection. We conclude that neutrophils are a major source of MMP-9, a previously proved pathological factor in this model. Further, we conclude that acute inflammation in the form of neutrophils and neutrophil activation products are at least partially responsible for inducing the histological changes that ultimately result in fibrosis and infertility in the mouse model of chlamydial upper genital tract disease.

A role for matrix metalloproteinase-9 in pathogenesis of urogenital Chlamydia muridarum infection in mice

Matrix metalloproteinases (MMPs) are a family of host-derived enzymes involved in the turnover of extracellular matrix (ECM) molecules and the processing of cytokines, chemokines and growth factors. We have previously reported that global inhibition of MMP in Chlamydia muridarum urogenital tract infection of susceptible strains of female mice impeded ascension of C. muridarum into the upper genital tract, blunted acute inflammatory responses and reduced the rate of formation of chronic disease. Because we have also observed that MMP-9 (also known as gelatinase B) is expressed in relatively large quantities in susceptible strains of mice in response to infection during acute phases of infection, we explored this further in a more selected fashion. We infected MMP-9 gene knockout mice and wild type controls intravaginally with C. muridarum. Both groups of mice had similar isolation rates from the lower urogenital tract but the absence of MMP-9 resulted in a slightly lower isolation rate in the upper genital tract, blunted acute inflammatory indices in the affected tissues and a reduced rate of formation of hydrosalpinx-a surrogate marker of infertility. These results imply that MMP-9 is involved in pathogenesis of chlamydial infection in this model possibly by amplifying inflammatory responses.

Inhibition of matrix metalloproteinases protects mice from ascending infection and chronic disease manifestations resulting from urogenital Chlamydia muridarum infection

Matrix metalloproteinases (MMP) are a family of host-derived enzymes involved in the turnover of extracellular matrix molecules. We have previously reported enhanced expression of matrix metalloproteinases in Chlamydia muridarum urogenital tract infection of female mice. Kinetics and patterns of MMP expression as well as enhanced expression in susceptible strains of mice in the prior study implied a role for MMP in pathogenesis. To explore this further, we infected a susceptible strain of mice (C3H/HeN) with C. muridarum and treated two groups of mice with either one of two chemical inhibitors of MMP (MMPi; captopril and a chemically modified tetracycline) and reserved infected sham-treated mice as controls. Neither of the treatments affected shedding of viable chlamydiae from the lower urogenital tract, but the administration of either MMPi protected mice from the formation of hydrosalpinx-a surrogate marker of oviduct occlusion and infertility. Interestingly, the mechanism of protection for mice treated with chemically modified tetracycline 3, appeared to be related to prevention of ascending upper genital tract infection. These results imply that MMP are involved in pathogenesis of chlamydial infection in this model by mediating ascension of the infection into the upper genital tract.

Outcome of urogenital infection with Chlamydia muridarum in CD14 gene knockout mice

BACKGROUND

CD14 has been postulated to play a role in chlamydial immunity and immunopathology. There is evidence to support this role in human infections but its function in a mouse model has not been investigated.

METHODS

Female CD14 gene knockout and C57BL/6J wild type mice were infected intravaginally with Chlamydia muridarum. The infection course was monitored by detection of viable chlamydiae from serially collected cervical-vaginal swabs. The sequela of tubal factor infertility was assessed using hydrosalpinx formation as a surrogate marker.

RESULTS

A significantly abbreviated infection course was observed in the CD14 gene knockout mice but hydrosalpinx formation occurred at similar rates between the two groups.

CONCLUSION

Involvement of CD14 during chlamydial infection impedes infection resolution but this does not affect the sequela of infertility as assessed by hydrosalpinx formation.

Expression of matrix metalloproteinases subsequent to urogenital Chlamydia muridarum infection of mice

The central hypothesis of this study was that matrix metalloproteinases (MMPs) would be enhanced following murine chlamydial infection and that their expression would vary in mouse strains that differ in their susceptibility to chronic chlamydia-induced disease. To address this hypothesis, female C3H/HeN and C57BL/6 mice were infected intravaginally with Chlamydia muridarum. Uterine and oviduct tissues were assessed for transcription of MMP genes and their tissue inhibitors. An increased activity of MMP genes relative to preinfection tissues was observed in the C3H/HeN mice when compared to C57BL/6 mice. Using gelatin zymography, we detected constitutive MMP-2 activity in both strains of mice but an increase in MMP-9. Casein zymography indicated the presence of two elastase-like activities consistent with MMP-12 and possibly MMP-7. Western blotting and antigen capture enzyme-linked immunoassay also confirmed an increase in MMP-9 but constitutive MMP-2 expression subsequent to the infection in both strains of mice. In C57BL/6 mice, MMP-9 was present in monomer and dimer form throughout the 56-day monitoring period. C3H/HeN mice produced dimeric MMP-9, but increases in the monomer form were also observed through day 14. Post-translational modification of MMP-9 between the two strains also differed. Immunohistochemistry revealed neutrophils as a prominent source for MMP-9 in both strains of mice. We conclude that differences in the relative expression and activity of MMPs, particularly MMP-9, occur in mice differing in their susceptibility to the development of chronic chlamydial disease. These differences may account for disparate outcomes with regard to chronic sequelae of the disease.

Histopathologic Changes Related to Fibrotic Oviduct Occlusion After Genital Tract Infection of Mice With Chlamydia muridarum

OBJECTIVES

We sought to determine if intraluminal occluding fibrosis of the oviduct occurs after urogenital Chlamydia muridarum infection in mice.

STUDY

Oviduct occlusion was assessed by infusing dye into the distal uterus and tracking the diffusion of the dye into the oviduct. We also conducted histologic assessment of the affected tissues using hematoxylin and eosin (H&E) and Masson trichrome stains.

RESULTS

All previously infected susceptible mice had occluded oviducts compared with 17.5% of previously uninfected mice. Oviduct occlusion correlated with hydrosalpinx formation and infertility. Intraluminal oviduct fibrosis was observed in several sections of tissue displaying hydrosalpinx but not in tissues without hydrosalpinx. Fibrosis was localized to the oviduct isthmus and oviduct proper, proximal to the uterus.

CONCLUSION

Intralumenal occluding fibrosis of the oviduct is a sequela of infection with C. muridarum in this model. These observations support the use of the murine model to study pathogenesis of chlamydial upper genital tract infection.

Inducible nitric oxide synthase regulates production of isoprostanes in vivo during chlamydial genital infection in mice

Urinary nitrite and F(2)-isoprostanes, an index of oxidant stress, were elevated during chlamydial genital infection of mice. Enhancement of urinary nitrite and F(2)-isoprostanes was observed in phagocyte oxidase-deficient mice. Inhibition of inducible nitric oxide synthase reduced isoprostane excretion. We conclude that nitrogen radicals induce F(2)-isoprostane production and excretion during murine chlamydial genital infection.

Chlamydia trachomatis enhances the expression of matrix metalloproteinases in an in vitro model of the human fallopian tube infection

OBJECTIVE

The sequelae of sexually transmitted Chlamydia trachomatis infection include fallopian tube scarring, which implies modification of the extracellular matrix. Our objective was to describe the production of two matrix metalloproteinases in response to chlamydial infection in vitro.

STUDY DESIGN

Human fallopian tube organ cultures were infected with Chlamydia, and the production of matrix metalloproteinases was assessed by gelatin zymography, antigen capture enzyme-linked immunosorbent assay, immunohistochemistry, and in situ zymography.

RESULTS

Significantly elevated levels of matrix metalloproteinase-2 and matrix metalloproteinase-9 were found in supernatants of infected segments. Immunohistochemistry and in situ zymography revealed that epithelial cells tended toward matrix metalloproteinase-2 production and that matrix metalloproteinase-9 exhibited a more diffuse stromal staining pattern.

CONCLUSION

Matrix metalloproteinase-2 and matrix metalloproteinase-9 are expressed in vitro in response to chlamydial infection. Enhanced matrix metalloproteinase production in some individuals in response to infection may lead to tubal scarring through the increased turnover and subsequent repair of the extracellular matrix.

Role for inducible nitric oxide synthase in protection from chronic Chlamydia trachomatis urogenital disease in mice and its regulation by oxygen free radicals

It has been previously reported that although inducible nitric oxide synthase (iNOS) gene knockout (NOS2(-/-)) mice resolve Chlamydia trachomatis genital infection, the production of reactive nitrogen species (RNS) via iNOS protects a significant proportion of mice from hydrosalpinx formation and infertility. We now report that higher in vivo RNS production correlates with mouse strain-related innate resistance to hydrosalpinx formation. We also show that mice with a deletion of a key component of phagocyte NADPH oxidase (p47(phox-/-)) resolve infection, produce greater amounts of RNS in vivo, and sustain lower rates of hydrosalpinx formation than both wild-type (WT) NOS2(+/+) and NOS2(-/-) controls. When we induced an in vivo chemical block in iNOS activity in p47(phox-/-) mice using N(G)-monomethyl-L-arginine (L-NMMA), a large proportion of these mice eventually succumbed to opportunistic infections, but not before they resolved their chlamydial infections. Interestingly, when compared to WT and untreated p47(phox-/-) controls, L-NMMA-treated p47(phox-/-) mice resolved their infections more rapidly. However, L-NMMA-treated p47(phox-/-) mice lost resistance to chronic chlamydial disease, as evidenced by an increased rate of hydrosalpinx formation that was comparable to that for NOS2(-/-) mice. We conclude that phagocyte oxidase-derived reactive oxygen species (ROS) regulate RNS during chlamydial urogenital infection in the mouse. We further conclude that while neither phagocyte oxidase-derived ROS nor iNOS-derived RNS are essential for resolution of infection, RNS protect from chronic chlamydial disease in this model.

Chlamydia trachomatis persistence in the female mouse genital tract: inducible nitric oxide synthase and infection outcome

It was previously reported that female mice resolve a primary Chlamydia trachomatis urogenital infection independent of inducible nitric oxide synthase (iNOS). We now report that although iNOS-deficient (NOS2(-/-)) mice resolve culture-apparent infection in a fashion similar to that of normal control (NOS2(+/+)) mice, they sustain significantly increased rates of disease, as assessed by hydrosalpinx formation. PCR amplification of ompA followed by Southern blot detection of amplicands revealed the presence of chlamydial DNA in the lower genital tracts of both NOS2(-/-) and NOS2(+/+) mice at > or =120 days postinfection and in upper genital tract tissues at >120 days postinfection. However, only NOS2(-/-) mice shed low numbers of viable chlamydiae from the lower genital tract after immunosuppressive treatment at 120 days postinfection. When cultured primary murine lung fibroblasts were activated in the presence of gamma interferon (IFN-gamma), inhibition of chlamydial growth occurred in both NOS2(+/+) and NOS2(-/-) cells, but the inhibition was reversible after removal of the cytokine in the NOS2(-/-) primary cell culture only. The iNOS-independent inhibition was microbistatic but was independent of 2,3-indoleamine dioxygenase activity. We conclude that chlamydial DNA and antigens persist in mice subsequent to culture-apparent resolution. In addition, IFN-gamma induces in vivo inhibition of chlamydial growth through microbistatic mechanisms in the absence of iNOS activity, but in the presence of iNOS activity, IFN-gamma is microbicidal and effects eradication.