Chlamydia muridarum infection associated host MicroRNAs in the murine genital tract and contribution to generation of host immune response

PROBLEM

Chlamydia trachomatis (CT) is the leading sexually transmitted bacterial infection in humans and is associated with reproductive tract damage. However, little is known about the involvement and regulation of microRNAs (miRs) in genital CT.

METHODS

We analyzed miRs in the genital tract (GT) following C. muridarum (murine strain of CT) challenge of wild type (WT) and CD4(+) T-cell deficient (CD4(-/-)) C57BL/6 mice at days 6 and 12 post-challenge.

RESULTS

At day 6, miRs significantly downregulated in the lower GT were miR-125b-5p, -16, -214, -23b, -135a, -182, -183, -30c, and -30e while -146 and -451 were significantly upregulated, profiles not exhibited at day 12 post-bacterial challenge. Significant differences in miR-125b-5p (+5.06-fold change), -135a (+4.9), -183 (+7.9), and -182 (+3.2) were observed in C. muridarum-infected CD4(-/-) compared to WT mice. In silico prediction and mass spectrometry revealed regulation of miR-135a and -182 and associated proteins, that is, heat-shock protein B1 and alpha-2HS-glycoprotein.

CONCLUSION

This study provides evidence on regulation of miRs following genital chlamydial infection suggesting a role in pathogenesis and host immunity.

A T cell epitope-based vaccine protects against chlamydial infection in HLA-DR4 transgenic mice

Vaccination with recombinant chlamydial protease-like activity factor (rCPAF) has been shown to provide robust protection against genital Chlamydia infection. Adoptive transfer of IFN-γ competent CPAF-specific CD4⁺ T cells was sufficient to induce early resolution of chlamydial infection and reduction of subsequent pathology in recipient IFN-γ-deficient mice indicating the importance of IFN-γ secreting CD4⁺ T cells in host defense against Chlamydia. In this study, we identify CD4⁺ T cell reactive CPAF epitopes and characterize the activation of epitope-specific CD4⁺ T cells following antigen immunization or Chlamydia challenge. Using the HLA-DR4 (HLA-DRB1*0401) transgenic mouse for screening overlapping peptides that induced T cell IFN-γ production, we identified at least 5 CPAF T cell epitopes presented by the HLA-DR4 complex. Immunization of HLA-DR4 transgenic mice with a rCPAFep fusion protein containing these 5 epitopes induced a robust cell-mediated immune response and significantly accelerated the resolution of genital and pulmonary Chlamydia infection. rCPAFep vaccination induced CPAF-specific CD4⁺ T cells in the spleen were detected using HLA-DR4/CPAF-epitope tetramers. Additionally, CPAF-specific CD4⁺ clones could be detected in the mouse spleen following Chlamydia muridarum and a human Chlamydia trachomatis strain challenge using these novel tetramers. These results provide the first direct evidence that a novel CPAF epitope vaccine can provide protection and that HLA-DR4/CPAF-epitope tetramers can detect CPAF epitope-specific CD4⁺ T cells in HLA-DR4 mice following C. muridarum or C. trachomatis infection. Such tetramers could be a useful tool for monitoring CD4⁺ T cells in immunity to Chlamydia infection and in developing epitope-based human vaccines using the murine model.

Shear Stress Enhances Chemokine Secretion from Chlamydia pneumoniae-infected Monocytes

Chlamydia pneumoniae is a common respiratory pathogen that is considered a highly likely risk factor for atherosclerosis. C. pneumoniae is disseminated from the lung into systemic circulation via infected monocytes and lodges at the atherosclerotic sites. During transit, C. pneumoniae-infected monocytes in circulation are subjected to shear stress due to blood flow. The effect of mechanical stimuli on infected monocytes is largely understudied in the context of C. pneumoniae infection and inflammation. We hypothesized that fluid shear stress alters the inflammatory response of C. pneumoniae-infected monocytes and contributes to immune cell recruitment to the site of tissue damage. Using an in vitro model of blood flow, we determined that a physiological shear stress of 7.5 dyn/cm² for 1 h on C. pneumoniae-infected monocytes enhances the production of several chemokines, which in turn is correlated with the recruitment of significantly large number of monocytes. Taken together, these results suggest synergistic interaction between mechanical and chemical factors in C. pneumoniae infection and associated inflammation.

Intranasal vaccination with Chlamydia pneumoniae induces cross-species immunity against genital Chlamydia muridarum challenge in mice

Chlamydia trachomatis is the most common bacterial sexually transmitted disease in the world and specifically in the United States, with the highest incidence in age-groups 14-19 years. In a subset of females, the C. trachomatis genital infection leads to serious pathological sequelae including pelvic inflammatory disease, ectopic pregnancy, and infertility. Chlamydia pneumoniae, another member of the same genus, is a common cause of community acquired respiratory infection with significant number of children aged 5-14 yr displaying sero-conversion. Since these bacteriae share several antigenic determinants, we evaluated whether intranasal immunization with live C. pneumoniae (1×10(6) inclusion forming units; IFU) in 5 week old female C57BL/6 mice would induce cross-species protection against subsequent intravaginal challenge with Chlamydia muridarum (5×10(4) IFU), which causes a similar genital infection and pathology in mice as C. trachomatis in humans. Mice vaccinated intranasally with live C. pneumoniae, but not mock (PBS) immunized animals, displayed high levels of splenic cellular antigen-specific IFN-γ production and serum antibody response against C. muridarum and C. trachomatis. Mice vaccinated with C. pneumoniae displayed a significant reduction in the vaginal C. muridarum shedding as early as day 12 after secondary i.vag. challenge compared to PBS (mock) immunized mice. At day 19 after C. muridarum challenge, 100% of C. pneumoniae vaccinated mice had cleared the infection compared to none (0%) of the mock immunized mice, which cleared the infection by day 27. At day 80 after C. muridarum challenge, C. pneumoniae vaccinated mice displayed a significant reduction in the incidence (50%) and degree of hydrosalpinx compared to mock immunized animals (100%). These results suggest that respiratory C. pneumoniae infection induces accelerated chlamydial clearance and reduction of oviduct pathology following genital C. muridarum challenge, and may have important implications to the C. trachomatis-induced reproductive disease in humans.

Vaginal chlamydial clearance following primary or secondary infection in mice occurs independently of TNF-α

The role of TNF-α in chlamydial clearance is uncertain. Antibody-mediated depletion of TNF-α in mice and guinea pigs has been shown not to significantly affect chlamydial clearance, whereas production of TNF-α in addition to IFN-γ from T cells has been shown to correlate with enhanced clearance. The aim of our study is to evaluate the mechanistic role of TNF-α in clearance of primary and secondary chlamydial infection from the genital tract (GT) using C57BL/6 TNF-α deficient (TNF-α^−/−) and wild type (WT) mice. Chlamydial shedding from the lower GT was evaluated following primary and secondary intravaginal challenge. Also, antibody and antigen specific cytokine responses were analyzed from the infected GT and spleens, and oviduct pathology determined to analyze the role of TNF-α in upper GT pathological sequelae. MHC II^−/− mice, known to display muted adaptive immune responses and failure to resolve genital chlamydial infections, were used as a negative control. Following both primary and secondary genital chlamydial infection, TNF-α^−/− mice exhibited elevated granzyme B production, but similar IFN-γ and antibody responses. Importantly, absence of TNF-α did not significantly alter the resolution of infection. However, TNF-α^−/− mice displayed significantly reduced upper genital tract (UGT) pathology compared to WT mice. This study demonstrates mechanistically that optimal chlamydial clearance following primary and secondary chlamydial genital infection can occur in the complete absence of TNF-α, and considered with the reduction of upper GT pathology in TNF-α^−/− mice, suggests that targeted induction of anti-chlamydial TNF-α responses by vaccination may be unnecessary, and moreover could be potentially pathogenic.

OT-1 mice display minimal upper genital tract pathology following primary intravaginal Chlamydia muridarum infection

Chlamydia trachomatis is the most common bacterial sexually transmitted disease worldwide and leads to serious pathological sequelae in the upper genital tract (UGT) including pelvic inflammatory disease, ectopic pregnancy, and infertility. Several components of the host immune responses have been shown to contribute to the UGT pathology following genital chlamydial infection. We have shown recently that CD8(+) T cells induce the chlamydial UGT pathology via the production of TNF-α. However, those studies did not determine whether the pathology is mediated by bystander or antigen-specific CD8(+) T cells. In this study, we compared chlamydial clearance and UGT pathology in OT-1 transgenic mice and the corresponding C57BL/6J wild-type mice following primary intravaginal Chlamydia muridarum infection. All CD8(+) T cells in the OT-1 mice respond only to the Ova 257-264 peptide and are incapable of responding to other antigenic epitopes including those of Chlamydia. OT-1 mice displayed vaginal chlamydial clearance comparable to the wild-type animals. However, both oviduct and uterine horn pathology were minimal in the OT-1 mice compared with the high degree of pathology observed in the wild-type animals. These results strongly suggest that Chlamydia-specific, not bystander, CD8(+) T cells mediate the UGT pathological sequelae following genital chlamydial infection.

Immunization with dendritic cells pulsed ex vivo with recombinant chlamydial protease-like activity factor induces protective immunity against genital chlamydiamuridarum challenge

We have shown that immunization with soluble recombinant chlamydial protease-like activity factor (rCPAF) and a T helper 1 type adjuvant can induce significantly enhanced bacterial clearance and protection against Chlamydia-induced pathological sequelae in the genital tract. In this study, we investigated the use of bone marrow derived dendritic cells (BMDCs) pulsed ex vivo with rCPAF + CpG in an adoptive subcutaneous immunization for the ability to induce protective immunity against genital chlamydial infection. We found that BMDCs pulsed with rCPAF + CpG efficiently up-regulated the expression of activation markers CD86, CD80, CD40, and major histocompatibility complex class II (MHC II), and secreted interleukin-12, but not IL-10 and IL-4. Mice adoptively immunized with rCPAF + CpG-pulsed BMDCs or UV-EB + CpG-pulsed BMDCs produced elevated levels of antigen-specific IFN-γ and enhanced IgG1 and IgG2a antibodies. Moreover, mice immunized with rCPAF + CpG-pulsed BMDCs or UV-EB + CpG-pulsed BMDCs exhibited significantly reduced genital Chlamydia shedding, accelerated resolution of infection, and reduced oviduct pathology when compared to infected mock-immunized animals. These results suggest that adoptive subcutaneous immunization with ex vivo rCPAF-pulsed BMDCs is an effective approach, comparable to that induced by UV-EB–BMDCs, for inducing robust anti-Chlamydia immunity.

Non-FcεR bearing mast cells secrete sufficient interleukin-4 to control Francisella tularensis replication within macrophages

Mast cells have classically been implicated in the triggering of allergic and anaphylactic reactions. However, recent findings have elucidated the ability of these cells to selectively release a variety of cytokines leading to bacterial clearance through neutrophil and dendritic cell mobilization, and suggest an important role in innate host defenses. Our laboratory has established a primary bone marrow derived mast cell-macrophage co-culture system and found that mast cells mediated a significant inhibition of Francisella tularensis live vaccine strain (LVS) uptake and replication within macrophages through contact and the secreted product interleukin-4 (IL-4). In this study, we utilized P815 mast cells and J774 macrophages to further investigate whether mast cell activation by non-FcεR driven signals could produce IL-4 and control intramacrophage LVS replication. P815 supernatants collected upon activation by the mast cell activating peptide MP7, as well as P815 cells co-cultured with J774 macrophages, exhibited marked inhibition of bacterial uptake and replication, which correlated with the production of IL-4. The inhibition noted in vitro was titratable and preserved at ratios relevant to cellular infiltration events following pulmonary challenge. Collectively, our data suggest that both primary mast cell and P815 mast cell (lacking FcεR) secreted IL-4 can control intramacrophage Francisella replication.

Evasion of IFN-γ signaling by Francisella novicida is dependent upon Francisella outer membrane protein C

Background

Francisella tularensis is a Gram-negative facultative intracellular bacterium and the causative agent of the lethal disease tularemia. An outer membrane protein (FTT0918) of F. tularensis subsp. tularensis has been identified as a virulence factor. We generated a F. novicida (F. tularensis subsp. novicida) FTN_0444 (homolog of FTT0918) fopC mutant to study the virulence-associated mechanism(s) of FTT0918.

Methods and Findings

The ΔfopC strain phenotype was characterized using immunological and biochemical assays. Attenuated virulence via the pulmonary route in wildtype C57BL/6 and BALB/c mice, as well as in knockout (KO) mice, including MHC I, MHC II, and µmT (B cell deficient), but not in IFN-γ or IFN-γR KO mice was observed. Primary bone marrow derived macrophages (BMDM) prepared from C57BL/6 mice treated with rIFN-γ exhibited greater inhibition of intracellular ΔfopC than wildtype U112 strain replication; whereas, IFN-γR KO macrophages showed no IFN-γ-dependent inhibition of ΔfopC replication. Moreover, phosphorylation of STAT1 was downregulated by the wildtype strain, but not the fopC mutant, in rIFN-γ treated macrophages. Addition of N^G-monomethyl-L-arginine, an NOS inhibitor, led to an increase of ΔfopC replication to that seen in the BMDM unstimulated with rIFN-γ. Enzymatic screening of ΔfopC revealed aberrant acid phosphatase activity and localization. Furthermore, a greater abundance of different proteins in the culture supernatants of ΔfopC than that in the wildtype U112 strain was observed.

Conclusions

F. novicida FopC protein facilitates evasion of IFN-γ-mediated immune defense(s) by down-regulation of STAT1 phosphorylation and nitric oxide production, thereby promoting virulence. Additionally, the FopC protein also may play a role in maintaining outer membrane stability (integrity) facilitating the activity and localization of acid phosphatases and other F. novicida cell components.

Mast cell/IL-4 control of Francisella tularensis replication and host cell death is associated with increased ATP production and phagosomal acidification

Mast cells are now recognized as effective modulators of innate immunity. We recently reported that mast cells and secreted interleukin-4 (IL-4) effectively control intramacrophage replication of Francisella tularensis Live Vaccine Strain (LVS), and that mice deficient in mast cells or IL-4 receptor (IL-4R(-/-)) exhibit greater susceptibility to pulmonary challenge. In this study, we further evaluated the mechanism(s) by which mast cells/IL-4 control intramacrophage bacterial replication and host cell death, and found that IL-4R(-/-) mice exhibited significantly greater induction of active caspase-3 within lung macrophages than wild-type animals following intranasal challenge with either LVS or the human virulent type A strain SCHU S4. Treatment of LVS-infected bone-marrow-derived macrophages with a pancaspase inhibitor (zVAD) did not alter bacterial replication, but minimized active caspase-3 and other markers (Annexin V and propidium iodide) of cell death, whereas treatment with both rIL-4 and zVAD resulted in concomitant reduction of both parameters, suggesting that inhibition of bacterial replication by IL-4 was independent of caspase activation. Interestingly, IL-4-treated infected macrophages exhibited significantly increased ATP production and phagolysosomal acidification, as well as enhanced mannose receptor upregulation and increased internalization with acidification, which correlated with observations in mast cell-macrophage co-cultures, with resultant decreases in F. tularensis replication.

Mannose-containing oligosaccharides of non-specific human secretory immunoglobulin A mediate inhibition of Vibrio cholerae biofilm formation

The role of antigen-specific secretory IgA (SIgA) has been studied extensively, whereas there is a limited body of evidence regarding the contribution of non-specific SIgA to innate immune defenses against invading pathogens. In this study, we evaluated the effects of non-specific SIgA against infection with Vibrio cholerae O139 strain MO10 and biofilm formation. Seven day old infant mice deficient in IgA (IgA^-/- mice) displayed significantly greater intestinal MO10 burden at 24 hr post-challenge when compared to IgA^+/+ pups. Importantly, cross-fostering of IgA^-/- pups with IgA^+/+ nursing dams reversed the greater susceptibility to MO10 infection, suggesting a role for non-specific SIgA in protection against the infection. Since biofilm formation is associated with virulence of MO10, we further examined the role of human non-specific SIgA on this virulence phenotype of the pathogen. Human non-specific SIgA, in a dose-dependent fashion, significantly reduced the biofilm formation by MO10 without affecting the viability of the bacterium. Such an inhibitory effect was not induced by human serum IgA, IgG, or IgM, suggesting a role for the oligosaccharide-rich secretory component (SC) of SIgA. This was supported by the demonstration that SIgA treated with endoglycosidase H, to cleave the high-mannose containing terminal chitobiose residues, did not induce a reduction in biofilm formation by MO10. Furthermore, the addition of free mannose per se, across a wide dose range, induced significant reduction in MO10 biofilm formation. Collectively, these results suggest that mannose containing oligosacchardies within human non-specific secretory IgA can alter important virulence phenotypes of Vibrio cholerae such as biofilm formation, without affecting viability of the microorganism. Such effects may contribute significantly to innate immune defenses against invading pathogens in vivo in the gastrointestinal tract.

Vaccination with the defined chlamydial secreted protein CPAF induces robust protection against female infertility following repeated genital chlamydial challenge

We previously have shown the efficacy of recombinant (r) chlamydial protease-like activity factor (CPAF) vaccination against hydrosalpinx development following primary genital chlamydial challenge. In this study, we evaluated further the protection induced by rCPAF vaccination against infertility. Following primary challenge, fertility levels were not significantly different between the mock- and CPAF-vaccinated and Chlamydia alone challenged mice. However, following secondary genital chlamydial challenge, mock (PBS) immunized mice displayed a significant reduction of fertility compared to age-matched naïve mice, while mice vaccinated intranasally with rCPAF+CpG displayed significant prevention of infertility. These results suggest that hydrosalpinx may be a reliable indicator of impending infertility, and that rCPAF is a promising candidate to prevent infertility resulting from repeated genital chlamydial infections.

Hydrodynamic regulation of monocyte inflammatory response to an intracellular pathogen

Systemic bacterial infections elicit inflammatory response that promotes acute or chronic complications such as sepsis, arthritis or atherosclerosis. Of interest, cells in circulation experience hydrodynamic shear forces, which have been shown to be a potent regulator of cellular function in the vasculature and play an important role in maintaining tissue homeostasis. In this study, we have examined the effect of shear forces due to blood flow in modulating the inflammatory response of cells to infection. Using an in vitro model, we analyzed the effects of physiological levels of shear stress on the inflammatory response of monocytes infected with chlamydia, an intracellular pathogen which causes bronchitis and is implicated in the development of atherosclerosis. We found that chlamydial infection alters the morphology of monocytes and trigger the release of pro-inflammatory cytokines TNF-α, IL-8, IL-1β and IL-6. We also found that the exposure of chlamydia-infected monocytes to short durations of arterial shear stress significantly enhances the secretion of cytokines in a time-dependent manner and the expression of surface adhesion molecule ICAM-1. As a functional consequence, infection and shear stress increased monocyte adhesion to endothelial cells under flow and in the activation and aggregation of platelets. Overall, our study demonstrates that shear stress enhances the inflammatory response of monocytes to infection, suggesting that mechanical forces may contribute to disease pathophysiology. These results provide a novel perspective on our understanding of systemic infection and inflammation.

The contribution of interleukin-12/interferon-gamma axis in protection against neonatal pulmonary Chlamydia muridarum challenge

Neonatal Chlamydia trachomatis pneumonia has been associated with respiratory sequelae in later life. We recently established a mouse model of neonatal pulmonary Chlamydia muridaum infection and found an important contribution of IFN-gamma to protective immunity. In this study, we further characterized the role of Th1-type cytokines; IL-12, IFN-gamma, and IFN-gamma signaling using mice genetically deficient in IL-12, IFN-gamma, or IFN-gamma receptor 1. All 3 knockout (KO) mice challenged intranasally with C. muridarum 1 day after birth exhibited 100% mortality by day 17 post-challenge whereas wild-type (WT) animals survived the monitoring period of 1 month. The KO mice exhibited greater lung bacterial burdens and enhanced dissemination to the liver, compared to WT animals. The inflammatory cellular infiltration in C. muridarum-challenged KO animals was significantly reduced in the lungs, but markedly enhanced in the livers of the KO mice compared to similarly challenged WT mice. It was also found that a deficiency in IL-12 or IFN-gamma resulted in correspondingly reduced IFN-gamma or IL-12 production, respectively, suggesting an intricate interdependence in the induction of these cytokines. Collectively, these results suggest that the IL-12/ IFN-gamma axis induces pulmonary cellular infiltration, induces bacterial clearance from the lung, reduces dissemination to other organs, and promotes the survival of the host during neonatal pulmonary chlamydial infection.

The Fischer 344 rat reflects human susceptibility to francisella pulmonary challenge and provides a new platform for virulence and protection studies

Background

The pathogenesis of Francisella tularensis, the causative agent of tularemia, has been primarily characterized in mice. However, the high degree of sensitivity of mice to bacterial challenge, especially with the human virulent strains of F. tularensis, limits this animal model for screening of defined attenuated vaccine candidates for protection studies.

Methods and Findings

We analyzed the susceptibility of the Fischer 344 rat to pulmonary (intratracheal) challenge with three different subspecies (subsp) of F. tularensis that reflect different levels of virulence in humans, and characterized the bacterial replication profile in rat bone marrow-derived macrophages (BMDM). In contrast to the mouse, Fischer 344 rats exhibit a broader range of sensitivity to pulmonary challenge with the human virulent subsp. tularensis and holarctica. Unlike mice, Fischer rats exhibited a high degree of resistance to pulmonary challenge with LVS (an attenuated derivative of subsp. holarctica) and subsp. novicida. Within BMDM, subsp. tularensis and LVS showed minimal replication, subsp. novicida showed marginal replication, and subsp. holartica replicated robustly. The limited intramacrophage replication of subsp. tularensis and novicida strains was correlated with the induction of nitric oxide production. Importantly, Fischer 344 rats that survived pulmonary infection with subsp. novicida were markedly protected against subsequent pulmonary challenge with subsp. tularensis, suggesting that subsp. novicida may be a useful platform for the development of vaccines against subsp. tularensis.

Conclusions

The Fischer 344 rat exhibits similar sensitivity to F. tularensis strains as that reported for humans, and thus the Fischer 344 ray may serve as a better animal model for tularemia vaccine development.

Heat denatured enzymatically inactive recombinant chlamydial protease-like activity factor induces robust protective immunity against genital chlamydial challenge

We have shown previously that vaccination with recombinant chlamydial protease-like activity factor (rCPAF) plus interleukin-12 as an adjuvant induces robust protective immunity against primary genital Chlamydia muridarum challenge in mice. Since CPAF is a protease, we compared the effects of enzymatically active and inactive (heat denatured) rCPAF to determine whether proteolytic activity is expendable for the induction of protective immunity against chlamydial challenge. Active, but not inactive, rCPAF immunization induced high levels of anti-active CPAF antibody, whereas both induced robust splenic CPAF-specific IFN-gamma production. Vaccination with active or inactive rCPAF induced enhanced vaginal chlamydial clearance as early as day 6 with complete resolution of infection by day 18, compared to day 30 in mock-vaccinated and challenged animals. Importantly, significant and comparable reductions in oviduct pathology were observed in active and inactive rCPAF-vaccinated mice compared to mock-vaccinated animals. Thus, rCPAF induced anti-chlamydial immunity is largely independent of enzymatic activity and secondary or higher order protein conformation.

Chlamydial protease-like activity factor--insights into immunity and vaccine development

Chlamydia trachomatis is a Gram-negative obligate intracellular pathogen that remains the leading cause of bacterial sexually transmitted disease worldwide, despite the availability of efficacious antimicrobial therapy. Given that chlamydial infections cause severe pathological sequelae in the upper genital tract, a licensed vaccine to prevent infection and disease would be an ideal solution. Chlamydial protease-like activity factor (CPAF) is a protein secreted in considerable amounts into the cytosol of infected cells and released into the extracellular milieu upon cellular lysis, which therefore is accessible to the host immune system. This is further substantiated by the observation that CPAF is immunodominant among other antigens in Chlamydia sero-positive humans. The efficacy of vaccination with CPAF against genital chlamydial challenge has been evaluated extensively in the murine model. This review will discuss important insights into the potential of CPAF as a component of an anti-chlamydial vaccine.

A limited role for antibody in protective immunity induced by rCPAF and CpG vaccination against primary genital Chlamydia muridarum challenge

Mice deficient in B cells (micromT mice) were used to evaluate the role of antibody in enhanced chlamydial clearance and reduction of pathology afforded by vaccination with recombinant chlamydial protease-like activity factor (rCPAF). Enhanced, but comparable, chlamydial clearance was observed in micromT and wild-type (WT) mice after rCPAF+CpG vaccination. Chlamydia-induced pathology was present in mock-immunized animals, but at significantly greater levels in micromT than WT mice, whereas vaccinated micromT and WT mice exhibited similar reductions in pathology. Thus, antibodies may play a role in protection against chlamydial pathology after primary infection, but were largely dispensable in rCPAF+CpG-induced chlamydial clearance and reduction in pathology.

Donepezil treatment of patients with MCI: a 48-week randomized, placebo-controlled trial

BACKGROUND

Treatment of mild cognitive impairment (MCI) with cholinesterase inhibitors may improve symptoms.

METHODS

In this multicenter, randomized, placebo-controlled trial, subjects with MCI entered a 3-week placebo run-in period followed by 48 weeks of double-blind donepezil (5 mg/day for 6 weeks, then 10 mg/day for 42 weeks) or placebo treatment. Primary efficacy variables included change from baseline in the modified Alzheimer Disease Assessment Scale-cognitive subscale (ADAS-Cog) and Clinical Dementia Rating Scale-sum of boxes (CDR-SB) after 48 weeks of treatment (modified intention-to-treat analysis). Secondary efficacy measures evaluated cognition, behavior, and function.

RESULTS

The dual primary efficacy endpoint was not reached. We noted a small, but significant, decrease in modified ADAS-Cog scores in favor of donepezil at study endpoint. Little change from baseline in CDR-SB and secondary variables was observed for either group. Patient Global Assessment scores favored donepezil at all time points except week 12 (p < or = 0.05). Perceived Deficits Questionnaire scores favored donepezil at week 24 (p = 0.05). Clinical Global Impression of Change-MCI scores favored donepezil only at week 6 (p = 0.04). Adverse events were generally mild or moderate. More donepezil-treated subjects (18.4%) discontinued treatment due to adverse events than placebo-treated subjects (8.3%).

CONCLUSIONS

Donepezil demonstrated small but significant improvement on the primary measure of cognition but there was no change on the primary measure of global function. Most other measures of global impairment, cognition, and function were not improved, possibly because these measures are insensitive to change in MCI. Responses on subjective measures suggest subjects perceived benefits with donepezil treatment.

Antigen-specific CD4+ T cells produce sufficient IFN-gamma to mediate robust protective immunity against genital Chlamydia muridarum infection

Chlamydia has been shown to evade host-specific IFN-gamma-mediated bacterial killing; however, IFN-gamma-deficient mice exhibit suboptimal late phase vaginal Chlamydia muridarum clearance, greater dissemination, and oviduct pathology. These findings introduce constraints in understanding results from murine chlamydial vaccination studies in context of potential implications to humans. In this study, we used mice deficient in either IFN-gamma or the IFN-gamma receptor for intranasal vaccination with a defined secreted chlamydial Ag, chlamydial protease-like activity factor (CPAF), plus CpG and examined the role of IFN-gamma derived from adoptively transferred Ag-specific CD4+ T cells in protective immunity against genital C. muridarum infection. We found that early Ag-specific IFN-gamma induction and CD4+ T cell infiltration correlates with the onset of genital chlamydial clearance. Adoptively transferred IFN-gamma competent CPAF-specific CD4+ T cells failed to enhance the resolution of genital chlamydial infection within recipient IFN-gamma receptor-deficient mice. Conversely, IFN-gamma production from adoptively transferred CPAF-specific CD4+ T cells was sufficient in IFN-gamma-deficient mice to induce early resolution of infection and reduction of subsequent pathology. These results provide the first direct evidence that enhanced anti-C. muridarum protective immunity induced by Ag-specific CD4+ T cells is dependent upon IFN-gamma signaling and that such cells produce sufficient IFN-gamma to mediate the protective effects. Additionally, MHC class II pathway was sufficient for induction of robust protective anti-C. muridarum immunity. Thus, targeting soluble candidate Ags via MHC class II to CD4+ T cells may be a viable vaccine strategy to induce optimal IFN-gamma production for effective protective immunity against human genital chlamydial infection.

Endogenous IFN-gamma production is induced and required for protective immunity against pulmonary chlamydial infection in neonatal mice

Chlamydia trachomatis infection in neonates, not adults, has been associated with the development of chronic respiratory sequelae. Adult chlamydial infections induce Th1-type responses that subsequently clear the infection, whereas the neonatal immune milieu in general has been reported to be biased toward Th2-type responses. We examined the protective immune responses against intranasal Chlamydia muridarum challenge in 1-day-old C57BL/6 and BALB/c mice. Infected C57BL/6 pups displayed earlier chlamydial clearance (day 14) compared with BALB/c pups (day 21). However, challenged C57BL/6 pups exhibited prolonged deficits in body weight gain (days 12-30) compared with BALB/c pups (days 9-12), which correlated with continual pulmonary cellular infiltration. Both strains exhibited a robust Th1-type response, including elevated titers of serum antichlamydial IgG2a and IgG2b, not IgG1, and elevated levels of splenic C. muridarum-specific IFN-gamma, not IL-4, production. Additionally, elevated IFN-gamma, not IL-4 expression, was observed locally in the infected lungs of both mouse strains. The immune responses in C57BL/6 pups were significantly greater compared with BALB/c pups after chlamydial challenge. Importantly, infected mice deficient in IFN-gamma or IFN-gamma receptor demonstrated enhanced chlamydial dissemination, and 100% of animals died by 2 wk postchallenge. Collectively, these results indicate that neonatal pulmonary chlamydial infection induces a robust Th1-type response, with elevated pulmonary IFN-gamma production, and that endogenous IFN-gamma is important in protection against this infection. The enhanced IFN-gamma induction in the immature neonatal lung also may be relevant to the development of respiratory sequelae in adult life.

Intranasal immunization with chlamydial protease-like activity factor and CpG deoxynucleotides enhances protective immunity against genital Chlamydia muridarum infection

We have reported recently that intranasal (i.n.) vaccination with chlamydial protease-like activity factor (CPAF) and interleukin-12 (IL-12) enhances protective immunity against genital chlamydial challenge. In this study, we show that i.n. or intraperitoneal (i.p.) vaccination with CPAF plus CpG deoxynucleotides (CpG), an alternative T helper 1 (Th1) adjuvant, induced robust CPAF-specific IFN-gamma responses and elevated levels of serum antibody and vaginal IgA production. CPAF+CpG vaccinated animals displayed accelerated genital chlamydial clearance, and minimal hydrosalpinx and inflammatory cellular infiltration compared to mock-immunized (PBS) challenged animals. Together, CpG dexoynucleotides are an efficacious alternative Th1 adjuvant with CPAF to induce protective anti-chlamydial immunity.

Intranasal vaccination with a secreted chlamydial protein enhances resolution of genital Chlamydia muridarum infection, protects against oviduct pathology, and is highly dependent upon endogenous gamma interferon production

There is currently no licensed vaccine against Chlamydia trachomatis, the leading cause of sexually transmitted bacterial disease worldwide. Conventional vaccination attempts using surface-exposed chlamydial antigens have achieved only partial success. We have employed a novel vaccination strategy using a secreted protein, chlamydial protease-like activity factor (CPAF), which has been shown to degrade host major histocompatibility complex transcription factors and keratin-8 and therefore may allow immune evasion and establishment of a productive infection. Intranasal immunization using recombinant CPAF (rCPAF) plus interleukin-12 (IL-12) (rCPAF+IL-12 immunization) was used to assess the protective immunity against genital Chlamydia muridarum infection in BALB/c mice. rCPAF+IL-12 immunization induced robust gamma interferon (IFN-gamma) production and minimal IL-4 production by splenocytes upon in vitro recall with rCPAF. The total and immunoglobulin G2a (IgG2a) anti-rCPAF antibody levels in serum were significantly elevated after rCPAF+IL-12 vaccination, as were the total antibody, IgG2a, and IgA levels in bronchoalveolar lavage and vaginal fluids when the animals were compared to animals that received rCPAF alone. rCPAF+IL-12-vaccinated mice displayed significantly reduced bacterial shedding upon chlamydial challenge and accelerated resolution of infection compared to mock-immunized (phosphate-buffered saline) animals. Moreover, rCPAF+IL-12-immunized animals exhibited protection against pathological consequences of chlamydial infection, including the development of hydrosalpinx and oviduct dilatation. This vaccination regimen also reduced the development of fibrosis and the influx of neutrophils into the upper genital tract when the animals were compared to mock-immunized (phosphate-buffered saline) animals after bacterial challenge. rCPAF+IL-12-mediated resolution of the bacterial infection and protection against Chlamydia-induced inflammatory disease were highly dependent on endogenous IFN-gamma production. Together, these results demonstrate that secreted chlamydial antigens may be novel vaccine candidates to induce protective immunity.

The protective efficacy of chlamydial protease-like activity factor vaccination is dependent upon CD4+ T cells

We have previously determined the protective efficacy of intranasal vaccination with chlamydial protease-like activity factor (CPAF) against genital chlamydial infection. Since T-helper 1 (Th1) responses are important for anti-chlamydial immunity, we examined the contribution of CD4(+) T cells in CPAF mediated immunity against intravaginal (i.vag.) Chlamydia muridarum infection in C57BL/6 mice. CPAF+IL-12 vaccination induced antigen-specific CD4(+) T cells that secreted elevated levels of IFN-gamma, and generated strong humoral responses. The protective effects of CPAF vaccination against genital chlamydial challenge were abrogated by anti-CD4 neutralizing antibody treatment. Moreover, anti-chlamydial immunity could be adoptively transferred to naïve recipients using CPAF-specific CD4(+) T cells. Therefore, CPAF mediated anti-chlamydial immunity is highly dependent upon antigen-specific CD4(+) T cells.