Association of Chlamydia pneumoniae with central nervous system disease

Olfactory immunology: the missing piece in airway and CNS defence

The olfactory mucosa is a component of the nasal airway that mediates the sense of smell. Recent studies point to an important role for the olfactory mucosa as a barrier to both respiratory pathogens and to neuroinvasive pathogens that hijack the olfactory nerve and invade the CNS. In particular, the COVID-19 pandemic has demonstrated that the olfactory mucosa is an integral part of a heterogeneous nasal mucosal barrier critical to upper airway immunity. However, our insufficient knowledge of olfactory mucosal immunity hinders attempts to protect this tissue from infection and other diseases. This Review summarizes the state of olfactory immunology by highlighting the unique immunologically relevant anatomy of the olfactory mucosa, describing what is known of olfactory immune cells, and considering the impact of common infectious diseases and inflammatory disorders at this site. We will offer our perspective on the future of the field and the many unresolved questions pertaining to olfactory immunity.

Chlamydia pneumonia infection and risk of multiple sclerosis: A meta-analysis

BACKGROUND

The role of infectious agents, including Chlamydia pneumoniae (Cpn), in the development of multiple sclerosis (MS), is still a matter of major contention.

OBJECTIVE

This meta-analysis study aimed to assess the actual involvement of Cpn in MS development.

METHODS

We undertook a search of international scientific databases to identify eligible studies. We used a random-effects meta-analysis model (REM) to generate the pooled odds ratio (OR) and 95% confidence intervals (CIs). Heterogeneity was calculated using the I2 statistic. Sensitivity and subgroup analyses were applied to assess the effects of study characteristics and socio-demographic variables on the pooled OR.

RESULTS

We identified 37 studies comprising 51 datasets that satisfied the inclusion criteria. Considering diagnostic methods for Cpn, 26 and 25 datasets used PCR- and serological-based methods, respectively. In PCR-based datasets, REM showed a significant positive association between Cpn infection and the development of MS (OR, 5.29; 95% CI, 3.12-8.97), while a non-significant positive association was achieved in serological-based datasets (OR, 1.34; 95% CI, 0.88-2.03). In subgroup analyses on PCR-based datasets, results were significant for both CSF (OR, 5.70) and serum (OR, 4.84) samples; both healthy (OR, 16.11) and hospital-based (OR, 2.88) controls; and both moderate (OR, 5.14) and high (OR, 5.48) quality studies. In serological-based datasets, only those that used CSF samples yielded significant results (OR, 3.41).

CONCLUSIONS

Our findings verify the significant positive relationship between Cpn infection and MS. We advocate prospective cohort studies with lifelong follow-ups and also experimental studies to better understand the role of Cpn in MS development.

The porin AaxA protein model from Chlamydia pneumonia

Chlamydophila pneumoniae is an intracellular pathogen accountable for various acute respiratory infections. C. pneumoniae has a gene cluster which encodes a putative outer membrane porin (aaxA), arginine decarboxylase (CPn1032 or aaxB) and a putative cytoplasmic membrane transporter (CPn1031 or aaxC). Therefore, it is of interest to document a molecular protein model of porin AaxA from Chlamydia pneumonia to gain structure to functional insight on the protein.

Dendrimer-conjugated peptide vaccine enhances clearance of Chlamydia trachomatis genital infection

Peptide-based vaccines have emerged in recent years as promising candidates in the prevention of infectious diseases. However, there are many challenges to maintaining in vivo peptide stability and enhancement of peptide immunogenicity to generate protective immunity which enhances clearance of infections. Here, a dendrimer-based carrier system is proposed for peptide-based vaccine delivery, and shows its anti-microbial feasibility in a mouse model of Chlamydia trachomatis. Chlamydiae are the most prevalent sexually transmitted bacteria worldwide, and also the causal agent of trachoma, the leading cause of preventable infectious blindness. In spite of the prevalence of this infectious agent and the many previous vaccine-related studies, there is no vaccine commercially available. The carrier system proposed consists of generation 4, hydroxyl-terminated, polyamidoamine (PAMAM) dendrimers (G4OH), to which a peptide mimic of a chlamydial glycolipid antigen-Peptide 4 (Pep4, AFPQFRSATLLL) was conjugated through an ester bond. The ester bond between G4OH and Pep4 is expected to break down mainly in the intracellular environment for antigen presentation. Pep4 conjugated to dendrimer induced Chlamydia-specific serum antibodies after subcutaneous immunizations. Further, this new vaccine formulation significantly protected immunized animals from vaginal challenge with infectious Chlamydia trachomatis, and it reduced infectious loads and tissue (genital tract) damage. Pep4 conjugated to G4OH or only mixed with peptide provided enhanced protection compared to Pep4 and adjuvant (i.e. alum), suggesting a potential adjuvant effect of the PAMAM dendrimer. Combined, these results demonstrate that hydroxyl-terminated PAMAM dendrimer is a promising polymeric nanocarrier platform for the delivery of peptide vaccines and this approach has potential to be expanded to other infectious intracellular bacteria and viruses of public health significance.

The relationship of Chlamydophila pneumoniae with schizophrenia: The role of brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) in this relationship

Several pathogens have been suspected of playing a role in the pathogenesis of schizophrenia. Chronic inflammation has been proposed to occur as a result of persistent infection caused by Chlamydophila pneumoniae cells that reside in brain endothelial cells for many years. It was recently hypothesized that brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) may play prominent roles in the development of schizophrenia. NT-3 and BDNF levels have been suggested to change in response to various manifestations of infection. Therefore, we aimed to elucidate the roles of BDNF and NT3 in the schizophrenia-C. pneumoniae infection relationship. RT-PCR, immunofluorescence and ELISA methods were used. Fifty patients suffering from schizophrenia and 35 healthy individuals were included as the patient group (PG) and the healthy control group (HCG), respectively. We detected persistent infection in 14 of the 50 individuals in the PG and in 1 of the 35 individuals in the HCG. A significant difference was found between the two groups (p<0.05). Twenty-two individuals in the PG and 13 in the HCG showed seropositivity for past C. pneumoniae infection, and no difference was observed between the groups (p>0.05). C. pneumoniae DNA was not detected in any group. A significant difference in NT-3 levels was observed between the groups, with very low levels in the PG (p<0.001). A significant difference in BDNF levels was also found, with lower levels in the PG (p<0.05). The mean serum NT-3 level was higher in the PG cases with C. pneumoniae seropositivity than in seronegative cases; however, this difference was not statistically significant (p>0.05). In conclusion, we suggest that NT-3 levels during persistent C. pneumoniae infection may play a role in this relationship.

Chlamydia pneumoniae infection and the risk of multiple sclerosis: a meta-analysis

We conducted a meta-analysis of studies comparing the presence of Chlamydia pneumoniae (Cpn) between multiple sclerosis (MS) patients and other neurological diseases patients or healthy controls. We identified 26 studies with 1332 MS patients and 1464 controls. Using random-effects methods, MS patients were found more likely to have detectable levels of Cpn DNA (OR = 3.216; 95% CI: 1.204, 8.585) in their cerebrospinal fluid, and intrathecally synthesized immunoglobulins (OR = 3.842; 95% CI: 1.317, 11.212), compared to other patients with neurological diseases. There is no evidence for increased levels of serum immunoglobulins (OR = 1.068; 95% CI: 0.745, 1.530), even though this result is confounded by the presence of studies using normal subjects as controls. Similarly, there is no evidence for association of immunoglobulins against Cpn in the cerebrospinal fluid (OR = 3.815; 95% CI: 0.715, 20.369). Up to 59.7% of the between-studies variability could be explained by the inappropriate matching of cases and controls for gender. In random-effects meta-regressions, adjusting for the confounding effect of gender differences results in stronger and statistically significant associations of MS with detectable levels of Cpn DNA, intrathecally synthesized immunoglobulins and immunoglobulins in the cerebrospinal fluid. Even though the presence of Cpn is clearly more likely in MS patients, these findings are insufficient to establish an etiologic relation.

Chlamydia Pneumoniae in PBMC: Reproducibility of the OMPA Nested Touchdown PCR

The aim of our study was to evaluate whether the replicate PCR testing may provide more accurate estimates of C. pneumoniae DNA prevalence in PBMC of patients undergoing carotid endarterectomy. Clinical sensitivity and reproducibility of ompA nested touchdown PCR was also performed. Clinical sensitivity and reproducibility was examined by testing C. pneumoniae-negative PBMC spiked with serial dilutions of semipurified C. pneumoniae elementary bodies (from 8 to 0.002 IFU/ml). Detection of C. pneumoniae DNA was performed by ompA nested touchdown PCR. Each clinical and spiked PBMC DNA specimen was analyzed in replicates of 1,3,5 and 10. PCR results of serial dilutions of C. pneumoniae DNA performed in replicates of 10 were analysed by probit analysis.

C. pneumoniae DNA was detected in 14 of the 30 (46.7%) PBMC clinical specimens examined when 10 replicates were tested. When we analyzed 1, 3 and 5 replicates, 4 (13.3%), 7(23.3%), 12(40%) of the 30 specimens were positive, respectively. The limit of detection of ompA nested PCR touchdown was 0.008 IFU/ml when 10 replicates were tested. The ompA nested PCR had reproducibility scores of 10 for 10 from 8 to 4 IFU/ml concentration, but scores decreased for smaller numbers of IFU/ml. Our results showed that repeat testing of the same specimen increased clinical sensitivity as well as reproducibility of the ompA nested touchdown PCR. In conclusion the replicate PCR testing improves the performance of ompA nested touchdown PCR and provides a more accurate estimates of the prevalence of C. pneumoniae in PBMC of patients with atherosclerotic cardiovascular disease.

Subversion of Cell-Autonomous Host Defense by Chlamydia Infection

Obligate intracellular bacteria entirely depend on the metabolites of their host cell for survival and generation of progeny. Due to their lifestyle inside a eukaryotic cell and the lack of any extracellular niche, they have to perfectly adapt to compartmentalized intracellular environment of the host cell and counteract the numerous defense strategies intrinsically present in all eukaryotic cells. This so-called cell-autonomous defense is present in all cell types encountering Chlamydia infection and is in addition closely linked to the cellular innate immune defense of the mammalian host. Cell type and chlamydial species-restricted mechanisms point a long-term evolutionary adaptation that builds the basis of the currently observed host and cell-type tropism among different Chlamydia species. This review will summarize the current knowledge on the strategies pathogenic Chlamydia species have developed to subvert and overcome the multiple mechanisms by which eukaryotic cells defend themselves against intracellular pathogens.

Interaction of Chlamydiae with human macrophages

The phylum Chlamydiae contains several members that are well-known human pathogens, like Chlamydia trachomatis and C. pneumoniae. Establishing a chronic bacterial infection requires the active evasion of the host immune response. A major arm of the innate immune defence is constituted by macrophages, which fight infections by removing bacteria and triggering an adaptive immune response. However, some pathogenic Chlamydia infect and survive in macrophages at least for a certain period of time. Therefore, macrophages can serve as vehicles for the dissemination of bacterial infections from the primary infection site via the urogenital or respiratory tract to distant sites in the body. The capacity to infect macrophages seems to depend on the chlamydial strain and the source of macrophages. In vitro infections of macrophages with C. trachomatis, C. psittaci and C. pneumoniae reveal low efficiency of infection and progeny formation, as well as failure to develop mature inclusions. In contrast, the emerging pathogen, Simkania negevensis, actively replicates in macrophages. Here we summarize the current knowledge of the intracellular and molecular key mechanisms of C. trachomatis, C. pneumoniae and S. negevensis infections in human macrophages.

Amoebal endosymbiont Protochlamydia induces apoptosis to human immortal HEp-2 cells

Protochlamydia, an environmental chlamydia and obligate amoebal endosymbiotic bacterium, evolved to survive within protist hosts, such as Acanthamobae, 700 million years ago. However, these bacteria do not live in vertebrates, including humans. This raises the possibility that interactions between Protochlamydia and human cells could induce a novel cytopathic effect, leading to new insights into host-parasite relationships. Therefore, we studied the effect of Protochlamydia on the survival of human immortal cell line, HEp-2 cells and primary peripheral blood mononuclear cells (PBMC). Using mainly 4',6-diamidino-2-phenylindole staining, fluorescent in situ hybridization, transmission electron microscopy, and also TUNEL and Transwell assays, we demonstrated that the Protochlamydia induced apoptosis in HEp-2 cells. The attachment of viable bacterial cells, but not an increase of bacterial infectious progenies within the cells, was required for the apoptosis. Other chlamydiae [Parachlamydia acanthamoebae and Chlamydia trachomatis (serovars D and L2)] did not induce the same phenomena, indicating that the observed apoptosis may be specific to the Protochlamydia. Furthermore, the bacteria had no effect on the survival of primary PBMCs collected from five volunteers, regardless of activation. We concluded that Protochlamydia induces apoptosis in human-immortal HEp-2 cells and that this endosymbiont could potentially be used as a biological tool for the elucidation of novel host-parasite relationships.

Chlamydia pneumoniae infection suppresses Staphylococcus enterotoxin B-induced proliferation associated with down-expression of CD25 in lymphocytes

Chlamydia pneumoniae (Chlamydophila pneumoniae) infects lymphocytes and modulates their immune functions; this is critical in the development of chronic inflammatory diseases associated with this pathogen. Therefore, to clarify this immune modulation due to C. pneumoniae infection, the effect of this infection on the proliferation of human peripheral blood lymphocytes was examined. Lymphocytes were proliferated by stimulation with Staphylococcus aureus enterotoxin B, and the cell number was increased up to 3 times the unstimulated lymphocyte number. Further, induction of CD25 expression was observed in 55.8% of lymphocytes. Infection with C. pneumoniae suppressed the proliferation of almost half the lymphocytes induced by stimulation with S. aureus enterotoxin B, and CD25 induction was inhibited in 64.7% of lymphocytes. Inhibition of CD25 expression was observed in both infected and uninfected lymphocytes in culture. However, the expression of VLA4 was not affected by C. pneumoniae infection. Furthermore, inhibition was observed only by infection with viable C. pneumoniae and not by the heat-killed bacteria. These results suggest that C. pneumoniae affects lymphocyte function by inhibiting proliferation and CD25 expression in response to immunological stimulation, possibly via humoral mediator(s).

Chlamydophila pneumoniae Infection and Its Role in Neurological Disorders

Chlamydophila pneumoniae is an intracellular pathogen responsible for a number of different acute and chronic infections. The recent deepening of knowledge on the biology and the use of increasingly more sensitive and specific molecular techniques has allowed demonstration of C. pneumoniae in a large number of persons suffering from different diseases including cardiovascular (atherosclerosis and stroke) and central nervous system (CNS) disorders. Despite this, many important issues remain unanswered with regard to the role that C. pneumoniae may play in initiating atheroma or in the progression of the disease. A growing body of evidence concerns the involvement of this pathogen in chronic neurological disorders and particularly in Alzheimer's disease (AD) and Multiple Sclerosis (MS). Monocytes may traffic C. pneumoniae across the blood-brain-barrier, shed the organism in the CNS and induce neuroinflammation. The demonstration of C. pneumoniae by histopathological, molecular and culture techniques in the late-onset AD dementia has suggested a relationship between CNS infection with C. pneumoniae and the AD neuropathogenesis. In particular subsets of MS patients, C. pneumoniae could induce a chronic persistent brain infection acting as a cofactor in the development of the disease. The role of Chlamydia in the pathogenesis of mental or neurobehavioral disorders including schizophrenia and autism is uncertain and fragmentary and will require further confirmation.

Molecular detection of Parachlamydia-like organisms in cerebrospinal fluid of patients with multiple sclerosis

The presence of Chlamydia-like organism DNA was investigated by polymerase chain reaction (PCR) in cerebrospinal fluid (CSF) samples from 27 patients previously found positive for Chlamydia pneumoniae DNA: 12 with multiple sclerosis (MS), grouped according to clinical and magnetic resonance imaging (MRI) evidence of disease activity, 8 with other inflammatory neurological disorders and 7 with non-inflammatory neurological disorders. PCR evidence of Chlamydia-like organisms in CSF was observed only in two relapsing-remitting MS patients with clinical and MRI disease activity. These findings suggest a possible association between C. pneumoniae and Chlamydia-like organism brain infections as a cofactor in MS development.

Chlamydia Pneumoniae and Chronic Diseases with a Great Impact on Public Health

Chlamydia pneumoniae is recognised as a common cause of respiratory tract infections and has recently been implicated in several extrapulmonary chronic diseases, with great impact on public health, such as atherosclerosis, multiple sclerosis and Alzheimer's disease. The involvement of C. pneumoniae in such diseases may be correlated to characteristic features of this pathogen, including intracellular growth and ability to induce persistent forms. C. pneumoniae persistent forms are inherently more suited to evade the host immune response and are more difficult to eradicate by antibiotics. Our preliminary experimental findings show that interaction of C. pneumoniae with macrophages and/or T cells characterized by interference with TNF-α production, and redox state, culminates in the induction of T cell apoptosis and survival of infected macrophages. Based on our evidence, the poor cooperation between T cells and macrophages could lead to an inappropriate immune response against C. pneumoniae that may therefore promote the development of extrapulmonary chronic diseases.

Chlamydophila pneumoniae DNA and mRNA transcript levels in peripheral blood mononuclear cells and cerebrospinal fluid of patients with multiple sclerosis

Chlamydophila pneumoniae DNA and mRNA transcripts were investigated by PCR and RT-PCR in fresh CSF and PBMC specimens co-cultured in Hep-2 cell lines and collected from 14 patients with definite RR MS and 19 patients with other inflammatory (OIND) and non-inflammatory (NIND) neurological controls. A positivity for C. pneumoniae DNA and mRNA was detected in CSF and PBMCs of 9 RR MS patients (64.2%) with evidence of disease activity, whereas only 3 controls were positive for Chlamydial DNA. These preliminary findings suggest that C. pneumoniae may occur in a persistent and metabolically active state at both peripheral and intrathecal levels in MS, but not in OIND and NIND.

Association of Alzheimer's disease and Chlamydophila pneumoniae

This paper critically reviews the association of infection by Chlamydophila pneumoniae (C. pneumoniae) and Alzheimer's disease (AD). The aging population has increased interest in finding the cause of AD, but studies have yielded contradictory results that are likely due to varying diagnostic tools and different uses of diagnostic tests. Knowledge of AD's characteristics, risk factors, and hypothesized etiologies has expanded since Alois Alzheimer's initial description of AD. Epidemiologic and projection studies provide incidence estimates of AD through a two-stage method: (1) primary diagnosis of dementia by cognitive testing such as Mini-Mental State Examination (MMSE), and (2) clinical diagnosis of AD through criteria such as National Institute of Neurological and Communicative Diseases and Stroke/Alzheimer's Disease and Related Disorders Association (NINCDS-ADRDA). Cross-sectional studies yield prevalence estimates of infection by C. pneumoniae by detecting immunoglobulins through laboratory tests such as microimmunofluorescence (MIF). Studies examining the association of C. pneumoniae and AD are limited, but brain autopsy provides information about presence, proximity to areas associated with AD, and bacterial load. Standardization of diagnostic techniques would allow for better comparability of studies, but uncertainty about the best method of diagnosis of infection by C. pneumoniae and AD may call for revised or novel diagnostic tools.

Chlamydia pneumoniae GroEL1 protein is cell surface associated and required for infection of HEp-2 cells

Chlamydia pneumoniae is an important obligate intracellular pathogen that replicates within an inclusion in the eukaryotic cell. The initial event of a chlamydial infection is the adherence to and subsequent uptake of the infectious elementary bodies (EBs) by the human cell. These processes require yet-unidentified bacterial and eukaryotic surface proteins. The GroEL1 protein, which exhibits a very strong antigenicity and in vitro can activate various eukaryotic cells, is a potential pathogenicity factor. We localized the protein during the infection process and found it in the inclusion but outside the chlamydial particles. GroEL1 was also localized on the surface of EBs, and the protein could be washed off the EBs. Latex beads coated with recombinantly produced GroEL1 (rGroEL1) bound in a dose-dependent manner to HEp-2 cells. Likewise, GroEL1, when expressed and displayed on the yeast cell surface, mediated adhesion to HEp-2 cells. Interestingly, the homologous GroEL2 and GroEL3 proteins showed no adhesive properties. Incubation of primary umbilical vein endothelial cells with soluble GroEL1 and GroEL1-coated latex beads activated the translocation of the general transcription factor NF-kappaB into the nucleus. Finally, preincubation of HEp-2 cells with rGroEL1 significantly reduced subsequent infection with C. pneumoniae, although adhesion of infectious bacteria to eukaryotic cells was not affected. Taken together, these data support a role for extracellular GroEL1 in the establishment of the chlamydial infection.

Systemic infections in multiple sclerosis and experimental autoimmune encephalomyelitis

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system (CNS). It has been suggested that viral and bacterial infections contribute to the pathogenesis of MS. This review will give an overview about the influence of viral and bacterial infections on MS and experimental autoimmune encephalomyelitis (EAE). It will focus on bacterial infections and will also emphasise therapeutic consequences such as the impact of antibiotic treatment on the course of EAE. In summary, a growing body of evidence suggests that systemic infections are a risk factor for the initiation of autoimmune processes including the induction of acute events in MS. Experimental and clinical data strongly suggest early treatment of bacterial infections in MS patients to avoid aggravation and relapse.

The investigation of Chlamydophila pneumoniae in patients with multiple sclerosis

Totally 32 cerebrospinal fluid samples from Multiple sclerosis (MS) patients were collected. DNA was extracted by High Pure PCR Template Preparation Kit. Two genomic segments, outer membrane protein genes ompA and omp9, were targeted for the detection of C. pneumoniae DNA in the samples by PCR tests. To detect ompA, a nested-PCR assay was designed, whereas for omp9, a PCR-Enyzme immunoassay (PCR-EIA) depending on streptavidin-biotin capture and dig detection of the PCR products was performed. C. pneumoniae DNA was not detected by each assays in patient samples.

Chlamydia pneumoniae infection of brain cells: An in vitro study

Inspired by the suggested associations between neurological diseases and infections, we determined the susceptibility of brain cells to Chlamydia pneumoniae (Cpn). Murine astrocyte (C8D1A), neuronal (NB41A3) and microglial (BV-2) cell lines were inoculated with Cpn. Infection was established by immunofluorescence and real-time PCR at various time points. Productive infection was assessed by transferring medium of infected cells to a detection layer. Finally, apoptosis and necrosis post-infection was determined. Our data demonstrate that the neuronal cell line is highly sensitive to Cpn, produces viable progeny and is prone to die after infection by necrosis. Cpn tropism was similar in an astrocyte cell line, apart from the higher production of extracellular Cpn and less pronounced necrosis. In contrast, the microglial cell line is highly resistant to Cpn as the immunohistochemical signs almost completely disappeared after 24 h. Nevertheless, significant Cpn DNA amounts could be detected, suggesting Cpn persistence. Low viable progeny and hardly any necrotic microglial cells were observed. Further research is warranted to determine whether these cell types show the same sensitivity to Cpn in an in vivo setting.

Inflammatory responses following Chlamydia pneumoniae infection of glial cells

Recently, infections have been implicated in the pathogenesis of Alzheimer's disease. Apart from the direct effects of pathogens, it can be hypothesized that inflammatory mechanisms, such as the production of pro-inflammatory mediators by resident glia, may result in neurotoxicity. Here, we examined the inflammatory responses in murine microglial cell (MMC) and murine astrocyte cell (MAC) lines following infection with Chlamydia pneumoniae (Cpn), a pathogen that has recently been associated with Alzheimer's disease. Furthermore, we determined whether these inflammatory responses are sufficient to cause neuronal cell death in vitro. MMCs and MACs were infected with Cpn. Subsequently, various chemo- and cytokines were determined in the culture supernatant fluid of infected/control cells at different time points post-infection. Significantly higher levels of monocyte chemoattractant protein 1, interleukin (IL)-6, tumour necrosis factor (TNF)-alpha and IL-1beta were found in supernatant fluids of infected MMCs compared with controls. In contrast, in the supernatant fluid of infected MACs, only monocyte chemoattractant protein 1 and IL-6 displayed significantly higher levels compared with controls. Moreover, neurotoxicity was examined up to 72 h after transferring the conditioned supernatant fluid to a neuronal cell layer. No neuronal cell death was observed when supernatant fluids from infected/mock-treated MACs were transferred. However, when neurones were exposed to conditioned supernatant fluid from infected MMCs, a significant increase in cell death was observed compared with mock. Furthermore, adding neutralizing antibodies against IL-6 and TNF-alpha to that conditioned supernatant fluid prevented neuronal cell death by approximately 50%. In conclusion, these data suggest that Cpn infection results in a pro-inflammatory milieu, particularly by activating MMCs, that ultimately results in neurodegeneration with prominent roles for both IL-6 and TNF-alpha.

Pathogenic potential of novel Chlamydiae and diagnostic approaches to infections due to these obligate intracellular bacteria

Novel chlamydiae are newly recognized members of the phylum Chlamydiales that are only distantly related to the classic Chlamydiaceae, i.e., Chlamydia and Chlamydophila species. They also exhibit an obligate biphasic intracellular life cycle within eukaryote host cells. Some of these new chlamydiae are currently considered potential emerging human and/or animal pathogens. Parachlamydia acanthamoebae and Simkania negevensis are both emerging respiratory human pathogens, Waddlia chondrophila could be a novel abortigenic bovine agent, and Piscichlamydia salmonis has recently been identified as an agent of the gill epitheliocystis in the Atlantic salmon. Fritschea spp. and Rhabdochlamydia spp. seem to be confined to arthropods, but some evidence for human exposure exists. In this review, we first summarize the data supporting a pathogenic potential of the novel chlamydiae for humans and other vertebrates and the interactions that most of these chlamydiae have with free-living amoebae. We then review the diagnostic approaches to infections potentially due to the novel chlamydiae, especially focusing on the currently available PCR-based protocols, mammalian cell culture, the amoebal coculture system, and serology.

Could Chlamydia Pneumoniae Be Considered an Infectious Risk Factor for Inflammatory Diseases Such as Atherosclerosis ?

Chlamydia pneumoniae, a Gram-negative intracellular obligate bacteria, is recognised as a common cause of upper respiratory tract infections, and accounts for ∼10% of community-acquired pneumonia. In recent years, chronic and persistent infection with C. pneumoniae has been implicated in the pathogenesis of atherosclerosis. Atherosclerosis is regarded as a chronic inflammatory disease that results from complex interactions between a variety of cell types such as endothelial cells, vascular smooth muscle cells, monocytes/macrophages and inflammatory mediators. Involvement of C. pneumoniae in the pathogenesis of atherosclerosis has been supported by findings from seroepidemiologic studies, direct detection of chlamydial DNA, experimental animal and in vitro studies, and antibiotic intervention trials. The spectrum of cell biological, animal, and human clinical data suggests that C. pneumoniae may be considered an infectious risk factor for atherosclerosis but further studies are needed to clarify the etiopathogenetic role of C. pneumoniae in atherosclerotic vessel walls.

CD8+ T cells specific for a potential HLA-A*0201 epitope from Chlamydophila pneumoniae are present in the PBMCs from infected patients

Infection with the common pathogen Chlamydophila pneumoniae (Cpn, previously Chlamydia pneumoniae) has a high prevalence in patients suffering from arteriosclerosis and may trigger or contribute to heart disease. In mice, CD8-positive T cells are critical for the eradication of the infection and the development of immune memory against Cpn. Although several H2-class I epitopes have been described, no HLA-class I-associated peptides from Cpn are known. In order to define HLA-A*0201 epitopes from Cpn, we focused on the bacterial heat shock proteins (HSP) 60 and 70 which are known to be recognized by the immune system. Using epitope prediction, peptide binding studies and peptide-specific CTLs from HLA-A2 transgenic mice, we could define a potential HSP-70-derived epitope. The study of PBMCs from Cpn-infected individuals using fluorescent MHC tetramers revealed that some patients have CD8(+) T cells capable of recognizing the Cpn HSP-70 HLA-A*0201 epitope. Our studies pave the way to the immunomonitoring of the anti-Cpn CTL immune response present in patients suffering from different diseases potentially linked to Cpn or anti-Cpn immunity.

Detection of Chlamydophila pneumoniae in the bone marrow of two patients with unexplained chronic anaemia

Anaemia of chronic disease (ACD) is a common finding involving iron deficiency and signs of inflammation. Here, we report on two patients with ACD where a persistent infection with Chlamydophila (Chlamydia) pneumoniae (CP) was detected in bone marrow (BM) biopsies. Infection was suspected by routine cytology and confirmed by immunofluorescence, electron microscopy, polymerase chain reaction (PCR) including different primer sets and laboratories and sequencing of the PCR product. This is a first report of chlamydial presence in the BM of anaemic patients. The cases are presented because persistent chlamydial infection may contribute more frequently to chronic refractory anaemia than previously suspected.

Emerging intracellular bacterial infections

Human infections by intracellular bacteria have been recognized for many years, but much of what we know about the pathogenesis of these diseases and their etiologic organisms has emerged within the past few years as a result of improved molecular-based means for their detection and classification. New insights concerning the epidemiology and pathogenesis of intracellular bacterial infections and methods for the detection of Chlamydophila pneumoniae, Ehrlichia chaffeensis, Anaplasma phagocytophilum, and Rickettsia species have made an impact on how we view them as agents of human disease. Emerging evidence suggesting a possible intracellular existence for another organism, Mycoplasma pneumoniae, may explain how this organism interacts with the host to induce chronic inflammatory conditions of the respiratory tract.