Samantha J. Dando

Chlamydia muridarum Infection-Induced Destruction of Male Germ Cells and Sertoli Cells Is Partially Prevented by Chlamydia Major Outer Membrane Protein-Specific Immune CD4 cells

ABSTRACT Chlamydia trachomatis infections are increasingly prevalent worldwide. Male chlamydial infections are associated with urethritis, epididymitis, and orchitis; however, the role of Chlamydia in prostatitis and male factor infertility remains controversial. Using a model of Chlamydia muridarum infection in male C57BL/6 mice, we investigated the effects of chlamydial infection on spermatogenesis and determined the potential of immune T cells to prevent infection-induced outcomes. Antigen-specific CD4 T cells significantly reduced the infectious burden in the penile urethra, epididymis, and vas deferens. Infection disrupted seminiferous tubules, causing loss of germ cells at 4 and 8 wk after infection, with the most severely affected tubules containing only Sertoli cells. Increased mitotic proliferation, DNA repair, and apoptosis in spermatogonial cells and damaged germ cells were evident in atrophic tubules. Activated caspase 3 (casp3) staining revealed increased (6-fold) numbers of Sertoli cells with abnormal morphology that were casp3 positive in tubules of infected mice, indicating increased levels of apoptosis. Sperm count and motility were both decreased in infected mice, and there was a significant decrease in morphologically normal spermatozoa. Assessment of the spermatogonial stem cell population revealed a decrease in promyelocytic leukemia zinc finger (PLZF)-positive cells in the seminiferous tubules. Interestingly, adoptive transfer of antigen-specific CD4 cells, particularly T-helper 2-like cells, prior to infection prevented these effects in spermatogenesis and Sertoli cells. These data suggest that chlamydial infection adversely affects spermatogenesis and male fertility, and that vaccination can potentially prevent the spread of infection and these adverse outcomes.

Pathogens Penetrating the Central Nervous System: Infection Pathways and the Cellular and Molecular Mechanisms of Invasion

SUMMARY The brain is well protected against microbial invasion by cellular barriers, such as the blood-brain barrier (BBB) and the blood-cerebrospinal fluid barrier (BCSFB). In addition, cells within the central nervous system (CNS) are capable of producing an immune response against invading pathogens. Nonetheless, a range of pathogenic microbes make their way to the CNS, and the resulting infections can cause significant morbidity and mortality. Bacteria, amoebae, fungi, and viruses are capable of CNS invasion, with the latter using axonal transport as a common route of infection. In this review, we compare the mechanisms by which bacterial pathogens reach the CNS and infect the brain. In particular, we focus on recent data regarding mechanisms of bacterial translocation from the nasal mucosa to the brain, which represents a little explored pathway of bacterial invasion but has been proposed as being particularly important in explaining how infection with Burkholderia pseudomallei can result in melioidosis encephalomyelitis.

Burkholderia pseudomallei Penetrates the Brain via Destruction of the Olfactory and Trigeminal Nerves: Implications for the Pathogenesis of Neurological Melioidosis

ABSTRACT Melioidosis is a potentially fatal disease that is endemic to tropical northern Australia and Southeast Asia, with a mortality rate of 14 to 50%. The bacterium Burkholderia pseudomallei is the causative agent which infects numerous parts of the human body, including the brain, which results in the neurological manifestation of melioidosis. The olfactory nerve constitutes a direct conduit from the nasal cavity into the brain, and we have previously reported that B. pseudomallei can colonize this nerve in mice. We have now investigated in detail the mechanism by which the bacteria penetrate the olfactory and trigeminal nerves within the nasal cavity and infect the brain. We found that the olfactory epithelium responded to intranasal B. pseudomallei infection by widespread crenellation followed by disintegration of the neuronal layer to expose the underlying basal layer, which the bacteria then colonized. With the loss of the neuronal cell bodies, olfactory axons also degenerated, and the bacteria then migrated through the now-open conduit of the olfactory nerves. Using immunohistochemistry, we demonstrated that B. pseudomallei migrated through the cribriform plate via the olfactory nerves to enter the outer layer of the olfactory bulb in the brain within 24 h. We also found that the bacteria colonized the thin respiratory epithelium in the nasal cavity and then rapidly migrated along the underlying trigeminal nerve to penetrate the cranial cavity. These results demonstrate that B. pseudomallei invasion of the nerves of the nasal cavity leads to direct infection of the brain and bypasses the blood-brain barrier. IMPORTANCE Melioidosis is a potentially fatal tropical disease that is endemic to northern Australia and Southeast Asia. It is caused by the bacterium Burkholderia pseudomallei, which can infect many organs of the body, including the brain, and results in neurological symptoms. The pathway by which the bacteria can penetrate the brain is unknown, and we have investigated the ability of the bacteria to migrate along nerves that innervate the nasal cavity and enter the frontal region of the brain by using a mouse model of infection. By generating a mutant strain of B. pseudomallei which is unable to survive in the blood, we show that the bacteria rapidly penetrate the cranial cavity using the olfactory (smell) nerve and the trigeminal (sensory) nerve that line the nasal cavity. Melioidosis is a potentially fatal tropical disease that is endemic to northern Australia and Southeast Asia. It is caused by the bacterium Burkholderia pseudomallei, which can infect many organs of the body, including the brain, and results in neurological symptoms. The pathway by which the bacteria can penetrate the brain is unknown, and we have investigated the ability of the bacteria to migrate along nerves that innervate the nasal cavity and enter the frontal region of the brain by using a mouse model of infection. By generating a mutant strain of B. pseudomallei which is unable to survive in the blood, we show that the bacteria rapidly penetrate the cranial cavity using the olfactory (smell) nerve and the trigeminal (sensory) nerve that line the nasal cavity.

The Duration of Chlamydia muridarum Genital Tract Infection and Associated Chronic Pathological Changes Are Reduced in IL-17 Knockout Mice but Protection Is Not Increased Further by Immunization

IL-17 is believed to be important for protection against extracellular pathogens, where clearance is dependent on neutrophil recruitment and local activation of epithelial cell defences. However, the role of IL-17 in protection against intracellular pathogens such as Chlamydia is less clear. We have compared (i) the course of natural genital tract C. muridarum infection, (ii) the development of oviduct pathology and (iii) the development of vaccine-induced immunity against infection in wild type (WT) BALB/c and IL-17 knockout mice (IL-17-/-) to determine if IL-17-mediated immunity is implicated in the development of infection-induced pathology and/or protection. Both the magnitude and duration of genital infection was significantly reduced in IL-17-/- mice compared to BALB/c. Similarly, hydrosalpinx was also greatly reduced in IL-17-/- mice and this correlated with reduced neutrophil and macrophage infiltration of oviduct tissues. Matrix metalloproteinase (MMP) 9 and MMP2 were increased in WT oviducts compared to IL-17-/- animals at day 7 post-infection. In contrast, oviducts from IL-17-/- mice contained higher MMP9 and MMP2 at day 21. Infection also elicited higher levels of Chlamydia -neutralizing antibody in serum of IL-17-/- mice than WT mice. Following intranasal immunization with C. muridarum Major Outer Membrane Protein (MOMP) and cholera toxin plus CpG adjuvants, significantly higher levels of chlamydial MOMP-specific IgG and IgA were found in serum and vaginal washes of IL-17-/- mice. T cell proliferation and IFNγ production by splenocytes was greater in WT animals following in vitro re-stimulation, however vaccination was only effective at reducing infection in WT, not IL-17-/- mice. Intranasal or transcutaneous immunization protected WT but not IL-17-/- mice against hydrosalpinx development. Our data show that in the absence of IL-17, the severity of C. muridarum genital infection and associated oviduct pathology are significantly attenuated, however neither infection or pathology can be reduced further by vaccination protocols that effectively protect WT mice.

The Severity of Chorioamnionitis in Pregnant Sheep Is Associated with In Vivo Variation of the Surface-Exposed Multiple-Banded Antigen/Gene of Ureaplasma parvum

Ureaplasma species are the bacteria most frequently isolated from human amniotic fluid in asymptomatic pregnancies and placental infections. Ureaplasma parvum serovars 3 and 6 are the most prevalent serovars isolated from men and women. We hypothesized that the effects on the fetus and chorioamnion of chronic ureaplasma infection in amniotic fluid are dependent on the serovar, dose, and variation of the ureaplasma multiple-banded antigen (MBA) and mba gene. We injected high- or low-dose U. parvum serovar 3, serovar 6, or vehicle intra-amniotically into pregnant ewes at 55 days of gestation (term = 150 days) and examined the chorioamnion, amniotic fluid, and fetal lung tissue of animals delivered by cesarean section at 125 days of gestation. Variation of the multiple banded antigen/mba generated by serovar 3 and serovar 6 ureaplasmas in vivo were compared by PCR assay and Western blot. Ureaplasma inoculums demonstrated only one (serovar 3) or two (serovar 6) MBA variants in vitro, but numerous antigenic variants were generated in vivo: serovar 6 passage 1 amniotic fluid cultures contained more MBA size variants than serovar 3 (P = 0.005), and ureaplasma titers were inversely related to the number of variants (P = 0.025). The severity of chorioamnionitis varied between animals. Low numbers of mba size variants (five or fewer) within amniotic fluid were associated with severe inflammation, whereas the chorioamnion from animals with nine or more mba variants showed little or no inflammation. These differences in chorioamnion inflammation may explain why not all women with in utero Ureaplasma spp. experience adverse pregnancy outcomes.

The Role of the Multiple Banded Antigen of Ureaplasma parvum in Intra-Amniotic Infection: Major Virulence Factor or Decoy?

The multiple banded antigen (MBA) is a predicted virulence factor of Ureaplasma species. Antigenic variation of the MBA is a potential mechanism by which ureaplasmas avoid immune recognition and cause chronic infections of the upper genital tract of pregnant women. We tested whether the MBA is involved in the pathogenesis of intra-amniotic infection and chorioamnionitis by injecting virulent or avirulent-derived ureaplasma clones (expressing single MBA variants) into the amniotic fluid of pregnant sheep. At 55 days of gestation pregnant ewes (n = 20) received intra-amniotic injections of virulent-derived or avirulent-derived U. parvum serovar 6 strains (2×104 CFU), or 10B medium (n = 5). Amniotic fluid was collected every two weeks post-infection and fetal tissues were collected at the time of surgical delivery of the fetus (140 days of gestation). Whilst chronic colonisation was established in the amniotic fluid of animals infected with avirulent-derived and virulent-derived ureaplasmas, the severity of chorioamnionitis and fetal inflammation was not different between these groups (p>0.05). MBA size variants (32–170 kDa) were generated in vivo in amniotic fluid samples from both the avirulent and virulent groups, whereas in vitro antibody selection experiments led to the emergence of MBA-negative escape variants in both strains. Anti-ureaplasma IgG antibodies were detected in the maternal serum of animals from the avirulent (40%) and virulent (55%) groups, and these antibodies correlated with increased IL-1β, IL-6 and IL-8 expression in chorioamnion tissue (p<0.05). We demonstrate that ureaplasmas are capable of MBA phase variation in vitro; however, ureaplasmas undergo MBA size variation in vivo, to potentially prevent eradication by the immune response. Size variation of the MBA did not correlate with the severity of chorioamnionitis. Nonetheless, the correlation between a maternal humoral response and the expression of chorioamnion cytokines is a novel finding. This host response may be important in the pathogenesis of inflammation-mediated adverse pregnancy outcomes.

Maternal Administration of Erythromycin Fails to Eradicate Intrauterine Ureaplasma Infection in an Ovine Model

Erythromycin is the standard antibiotic used for treatment of infection with Ureaplasma spp. during pregnancy; however, maternally administered erythromycin may be ineffective at eliminating intra-amniotic ureaplasma infections. We examined whether erythromycin would eradicate intra-amniotic ureaplasma infections in pregnant sheep. At Gestational Day (GD) 50 (term, GD 150), pregnant ewes received intra-amniotic injections of erythromycin-sensitive Ureaplasma parvum serovar 3 (n = 16) or 10B medium (n = 16). At GD 100, amniocentesis was performed; five fetal losses (ureaplasma group, n = 4; 10B group, n = 1) had occurred by this time. Remaining ewes were allocated into treatment subgroups: medium only (n = 7), medium and erythromycin (n = 8), ureaplasma only (Up; n = 6), or ureaplasma and erythromycin (Up/E; n = 6). Erythromycin was administered intramuscularly (500 mg) every 8 h for 4 days (GDs 100–104). Amniotic fluid samples were collected at GD 105. At GD 125, preterm fetuses were surgically delivered, and specimens were collected for culture and histology. Erythromycin was quantified in amniotic fluid by liquid chromatography-mass spectrometry. Ureaplasmas were isolated from the amniotic fluid, chorioamnion, and fetal lung of animals from the Up and Up/E groups, however, the numbers of U. parvum recovered were not different between these groups. Inflammation in the chorioamnion, cord, and fetal lung was increased in ureaplasma-exposed animals compared to controls but was not different between the Up and Up/E groups. Erythromycin was detected in amniotic fluid samples, although concentrations were low (<10–76 ng/ml). This study demonstrates that maternally administered erythromycin does not eradicate chronic, intra-amniotic ureaplasma infections or improve fetal outcomes in an ovine model, potentially because of the poor placental passage of erythromycin.

A case of mistaken identity: CD11c-eYFP(+) cells in the normal mouse brain parenchyma and neural retina display the phenotype of microglia, not dendritic cells.

Under steady‐state conditions the central nervous system (CNS) is traditionally thought to be devoid of antigen presenting cells; however, putative dendritic cells (DCs) expressing enhanced yellow fluorescent protein (eYFP) are present in the retina and brain parenchyma of CD11c‐eYFP mice. We previously showed that these mice carry the Crb1rd8 mutation, which causes retinal dystrophic lesions; therefore we hypothesized that the presence of CD11c‐eYFP+ cells within the CNS may be due to pathology associated with the Crb1rd8 mutation. We generated CD11c‐eYFP Crb1wt/wt mice and compared the distribution and immunophenotype of CD11c‐eYFP+ cells in CD11c‐eYFP mice with and without the Crb1rd8 mutation. The number and distribution of CD11c‐eYFP+ cells in the CNS was similar between CD11c‐eYFP Crb1wt/wt and CD11c‐eYFP Crb1rd8/rd8 mice. CD11c‐eYFP+ cells were distributed throughout the inner retina, and clustered in brain regions that receive input from the external environment or lack a blood‐brain barrier. CD11c‐eYFP+ cells within the retina and cerebral cortex of CD11c‐eYFP Crb1wt/wt mice expressed CD11b, F4/80, CD115 and Iba‐1, but not DC or antigen presentation markers, whereas CD11c‐eYFP+ cells within the choroid plexus and pia mater expressed CD11c, I‐A/I‐E, CD80, CD86, CD103, DEC205, CD8α and CD135. The immunophenotype of CD11c‐eYFP+ cells and microglia within the CNS was similar between CD11c‐eYFP Crb1wt/wt and CD11c‐eYFP Crb1rd8/rd8 mice; however, CD11c and I‐A/I‐E expression was significantly increased in CD11c‐eYFP Crb1rd8/rd8 mice. This study demonstrates that the overwhelming majority of CNS CD11c‐eYFP+ cells do not display the phenotype of DCs or their precursors and are most likely a subpopulation of microglia. GLIA 2016. GLIA 2016;64:1331–1349

The Human Ureaplasma Species as Causative Agents of Chorioamnionitis

SUMMARY The human Ureaplasma species are the most frequently isolated microorganisms from the amniotic fluid and placentae of women who deliver preterm and are also associated with spontaneous abortions or miscarriages, neonatal respiratory diseases, and chorioamnionitis. Despite the fact that these microorganisms have been habitually found within placentae of pregnancies with chorioamnionitis, the role of Ureaplasma species as a causative agent has not been satisfactorily explained. There is also controversy surrounding their role in disease, particularly as not all women infected with Ureaplasma spp. develop chorioamnionitis. In this review, we provide evidence that Ureaplasma spp. are associated with diseases of pregnancy and discuss recent findings which demonstrate that Ureaplasma spp. are associated with chorioamnionitis, regardless of gestational age at the time of delivery. Here, we also discuss the proposed major virulence factors of Ureaplasma spp., with a focus on the multiple-banded antigen (MBA), which may facilitate modulation/alteration of the host immune response and potentially explain why only subpopulations of infected women experience adverse pregnancy outcomes. The information presented within this review confirms that Ureaplasma spp. are not simply “innocent bystanders” in disease and highlights that these microorganisms are an often underestimated pathogen of pregnancy.

Ureaplasma parvum Serovar 3 Multiple Banded Antigen Size Variation after Chronic Intra-Amniotic Infection/Colonization

Ureaplasma species are the microorganisms most frequently associated with adverse pregnancy outcomes. The multiple banded antigen (MBA), a surface-exposed lipoprotein, is a key virulence factor of ureaplasmas. The MBA demonstrates size variation, which we have shown previously to be correlated with the severity of chorioamnion inflammation. We aimed to investigate U. parvum serovar 3 pathogenesis in vivo, using a sheep model, by investigating: MBA variation after long term (chronic) and short term (acute) durations of in utero ureaplasma infections, and the severity of chorioamnionitis and inflammation in other fetal tissues. Inocula of 2×107 colony-forming-units (CFU) of U. parvum serovar 3 (Up) or media controls (C) were injected intra-amniotically into pregnant ewes at one of three time points: day 55 (69d Up, n = 8; C69, n = 4); day 117 (7d Up, n = 8; C7, n = 2); and day 121 (3d Up, n = 8; C3, n = 2) of gestation (term = 145–150d). At day 124, preterm fetuses were delivered surgically. Samples of chorioamnion, fetal lung, and umbilical cord were: (i) snap frozen for subsequent ureaplasma culture, and (ii) fixed, embedded, sectioned and stained by haematoxylin and eosin stain for histological analysis. Selected fetal lung clinical ureaplasma isolates were cloned and filtered to obtain cultures from a single CFU. Passage 1 and clone 2 ureaplasma cultures were tested by western blot to demonstrate MBA variation. In acute durations of ureaplasma infection no MBA variants (3d Up) or very few MBA variants (7d Up) were present when compared to the original inoculum. However, numerous MBA size variants were generated in vivo (alike within contiguous tissues, amniotic fluid and fetal lung, but different variants were present within chorioamnion), during chronic, 69d exposure to ureaplasma infection. For the first time we have shown that the degree of ureaplasma MBA variation in vivo increased with the duration of gestation.