IVIG induces apoptotic cell death in CD56dim NK cells resulting in inhibition of ADCC effector activity of human PBMC.

The mechanism of the efficacy of Intravenous immunoglobulins (IVIG) in autoimmune and inflammatory diseases is not well understood. This study aimed at understanding mechanisms of IVIG-mediated suppression of effector cell activities of peripheral blood mononuclear cells (PBMC) in antibody-dependent cellular cytotoxicity (ADCC). We were particularly interested in CD56dim NK cells, the main ADCC effector cells in PBMC. Exposure of PBMC to IVIG for at least 48 h induced a caspase-3-dependent apoptotic cell death of CD56dim NK cells without affecting CD56bright NK cells. Induction of apoptosis in CD56dim NK cells and concomitant suppression of ADCC effector activities of PBMC was associated with the monomer fraction of IVIG. Moreover, it was independent of IgG sialyation, did not depend on engagement of FcγRIII and could not be mimicked by IVIG (Fab')2 or IVIG Fc preparations. The described effect could contribute to the reduction of peripheral NK cells observed during IVIG therapy in patients.

[In vitro exposure of the shisha tobacco ingredient glycerol to human mucosa cells and lymphocytes]. / In vitro-Exposition des Shisha-Tabak-Bestandteils Glycerin an humanen Mukosazellen und Lymphozyten.

Shisha tobacco has a higher amount of glycerol than cigarette tobacco. Moreover, new legislation in Germany cancels the old limitation of humectants in shisha tobacco. Although higher amounts of glycerol in tobacco are expected, the knowledge of the toxicological profile of glycerol regarding human cells is incomplete. Aim of the study was to test glycerol for cytotoxic and genotoxic effects and to discuss the risk of humectants in shisha tobacco and the situation of German tobacco control.Lymphocytes and nasal mucosa cells of 10 patients were exposed to different glycerol levels (0.001 mol/l to 6.0 mol/l). Cytotoxic effects were examined by trypan blue exclusion test, genotoxic effects by comet assay and micronucleus test.The trypan blue exclusion test revealed significant cytotoxic effects on lymphocytes and nasal mucosa cells for glycerol concentrations of 1.0 mol/l and higher. In the comet assay a significant DNA damage could be shown for glycerol levels of 1.0 mol/l and higher. No significant micronucleus formation was monitored.While the geno- and cytotoxicity were seen in concentrations of glycerol clearly exceeding the concentrations in main stream smoke of shishas, genotoxicity is a stochastic risk occurring even at subtoxic levels. Furthermore, toxicity in lower levels could result from tobacco combustion or interactions with other smoke components. For an extensive evaluation of the risks of humectants in shisha tobacco further studies are needed. In addition, there is an enormous need for introducing further measures of tobacco control policy in Germany.

Severe malaria in children leads to a significant impairment of transitory otoacoustic emissions--a prospective multicenter cohort study.

BACKGROUND: Severe malaria may influence inner ear function, although this possibility has not been examined prospectively. In a retrospective analysis, hearing impairment was found in 9 of 23 patients with cerebral malaria. An objective method to quickly evaluate the function of the inner ear are the otoacoustic emissions. Negative transient otoacoustic emissions are associated with a threshold shift of 20 dB and above. METHODS: This prospective multicenter study analyses otoacoustic emissions in patients with severe malaria up to the age of 10 years. In three study sites (Ghana, Gabon, Kenya) 144 patients with severe malaria and 108 control children were included. All malaria patients were treated with parental artesunate. RESULTS: In the control group, 92.6 % (n = 108, 95 % confidence interval 86.19-6.2 %) passed otoacoustic emission screening. In malaria patients, 58.5 % (n = 94, malaria vs controls p < 0.001, 95 % confidence interval 48.4-67.9 %) passed otoacoustic emission screening at the baseline measurement. The value increased to 65.2 % (n = 66, p < 0.001, 95 % confidence interval 53.1-75.5 %) at follow up 14-28 days after diagnosis of malaria. The study population was divided into severe non-cerebral malaria and severe malaria with neurological symptoms (cerebral malaria). Whereas otoacoustic emissions in severe malaria improved to a passing percentage of 72.9 % (n = 48, 95 % confidence interval 59-83.4 %) at follow-up, the patients with cerebral malaria showed a drop in the passing percentage to 33 % (n = 18) 3-7 days after diagnosis. This shows a significant impairment in the cerebral malaria group (p = 0.012 at days 3-7, 95 % confidence interval 16.3-56.3 %; p = 0.031 at day 14-28, 95 % confidence interval 24.5-66.3 %). CONCLUSION: The presented data show that 40 % of children have involvement of the inner ear early in severe malaria. In children, audiological screening after severe malaria infection is not currently recommended, but is worth investigating in larger studies.

Immunoglobulins stimulate cultured Schwann cell maturation and promote their potential to induce axonal outgrowth.

BACKGROUND: Schwann cells are the myelinating glial cells of the peripheral nervous system and exert important regenerative functions revealing them as central repair components of many peripheral nerve pathologies. Intravenous immunoglobulins (IVIG) are widely used to treat autoimmune and inflammatory diseases including immune-mediated neuropathies. Nevertheless, promotion of peripheral nerve regeneration is currently an unmet therapeutical goal. We therefore examined whether immunoglobulins affect glial cell homeostasis, differentiation, and Schwann cell dependent nerve regenerative processes. METHODS: The responses of different primary Schwann cell culture models to IVIG were investigated: immature or differentiation competent Schwann cells, myelinating neuron/glial cocultures, and dorsal root ganglion explants. Immature or differentiating Schwann cells were used to study cellular proliferation, morphology, and gene/protein expression. Myelination rates were determined using myelinating neuron/glia cocultures, whereas axonal outgrowth was assessed using non-myelinating dorsal root ganglion explants. RESULTS: We found that IVIG specifically bind to Schwann cells and detected CD64 Fc receptor expression on their surface. In response to IVIG binding, Schwann cells reduced proliferation rates and accelerated growth of cellular protrusions. Furthermore, we observed that IVIG treatment transiently boosts myelin gene expression and myelination-related signaling pathways of immature cells, whereas in differentiating Schwann cells, myelin expression is enhanced on a long-term scale. Importantly, myelin gene upregulation was not detected upon application of IgG1 control antibodies. In addition, we demonstrate for the first time that Schwann cells secrete interleukin-18 upon IVIG stimulation and that this cytokine instructs these cells to promote axonal growth. CONCLUSIONS: We conclude that IVIG can positively influence the Schwann cell differentiation process and that it enhances their regenerative potential.

First-in-human dose escalation trial to evaluate the clinical safety and efficacy of an anti-MAGEA1 autologous TCR-transgenic T cell therapy in relapsed and refractory solid tumors.

RATIONALE OF THE TRIAL: Although the use of engineered T cells in cancer immunotherapy has greatly advanced the treatment of hematological malignancies, reaching meaningful clinical responses in the treatment of solid tumors is still challenging. We investigated the safety and tolerability of IMA202 in a first-in-human, dose escalation basket trial in human leucocyte antigen A*02:01 positive patients with melanoma-associated antigen A1 (MAGEA1)-positive advanced solid tumors. TRIAL DESIGN: The 2+2 trial design was an algorithmic design based on a maximally acceptable dose-limiting toxicity (DLT) rate of 25% and the sample size was driven by the algorithmic design with a maximum of 16 patients. IMA202 consists of autologous genetically modified cytotoxic CD8+ T cells expressing a T cell receptor (TCR), which is specific for a nine amino acid peptide derived from MAGEA1. Eligible patients underwent leukapheresis, T cells were isolated, transduced with lentiviral vector carrying MAGEA1-specific TCR and following lymphodepletion (fludarabine/cyclophosphamide), infused with a median of 1.4×109 specific T cells (range, 0.086×109-2.57×109) followed by interleukin 2. SAFETY OF IMA202: No DLT was observed. The most common grade 3-4 adverse events were cytopenias, that is, neutropenia (81.3%), lymphopenia (75.0%), anemia (50.0%), thrombocytopenia (50.0%) and leukopenia (25.0%). 13 patients experienced cytokine release syndrome, including one grade 3 event. Immune effector cell-associated neurotoxicity syndrome was observed in two patients and was grade 1 in both. EFFICACY OF IMA202: Of the 16 patients dosed, 11 (68.8%) patients had stable disease (SD) as their best overall response (Response Evaluation Criteria in Solid Tumors V.1.1). Five patients had initial tumor shrinkage in target lesions and one patient with SD experienced continued shrinkage in target lesions for 3 months in total but had to be classified as progressive disease due to progressive non-target lesions. IMA202 T cells were persistent in peripheral blood for several weeks to months and were also detectable in tumor tissue. Peak persistence was higher in patients who received higher doses. CONCLUSION: In conclusion, IMA202 had a manageable safety profile, and it was associated with biological and potential clinical activity of MAGEA1-targeting genetically engineered TCR-T cells in a poor prognosis, multi-indication solid tumor cohort. TRIAL REGISTRATION NUMBERS: NCT04639245, NCT05430555.

Apolipoprotein B100 is a suppressor of Staphylococcus aureus-induced innate immune responses in humans and mice.

Plasma lipoproteins such as LDL (low-density lipoprotein) are important therapeutic targets as they play a crucial role in macrophage biology and metabolic disorders. The impact of lipoprotein profiles on host defense pathways against Gram-positive bacteria is poorly understood. In this report, we discovered that human serum lipoproteins bind to lipoteichoic acid (LTA) from Staphylococcus aureus and thereby alter the immune response to these bacteria. Size-exclusion chromatography and solid-phase-binding analysis of serum revealed the direct interaction of LTA with apolipoproteins (Apo) B100, ApoA1, and ApoA2. Only ApoB100 and the corresponding LDL exerted biological effects as this binding significantly inhibited LTA-induced cytokine releases from human and murine immune cells. Serum from hypercholesterolemic mice or humans significantly diminished cytokine induction in response to S. aureus or its LTA. Sera taken from the patients with familial hypercholesterolemia before and after ApoB100-directed immuno-apheresis confirmed that ApoB100 inhibited LTA-induced inflammation in humans. In addition, mice in which LDL secretion was pharmacologically inhibited, displayed significantly increased serum cytokine levels upon infection with S. aureus in vivo. The present study identifies ApoB100 as an important suppressor of innate immune activation in response to S. aureus and its LTA.

Release of intracranial pressure leads to improvement of otoacoustic emissions--a case report of a Kenyan child with complicated tuberculous meningitis.

Intracranial pressure usually is measured with invasive techniques. The usability of transient evoked otoacoustic emissions as non-invasive approach has been evaluated only once by Frank et al. This article presents the case of a Kenyan boy with tuberculous meningitis and an active malresorptive hydrocephalus. At this stage, the otoacoustic emissions did show very low correlations. After releasing pressure, the otoacoustic emissions improved significantly. This case report points out the possible usability of otoacoustic emissions in intracranial pressure monitoring.

An ultra-high-throughput screen for the evaluation of peptide HLA-Binder interactions.

Peptide human leukocyte antigen (pHLA) targeting therapeutics like T-cell receptor based adoptive cell therapy or bispecific T cell engaging receptor molecules hold great promise for the treatment of cancer. Comprehensive pre-clinical screening of therapeutic candidates is important to ensure patient safety but is challenging because of the size of the potential off-target space. By combining stabilized peptide-receptive HLA molecules with microarray printing and screening, we have developed an ultra-high-throughput screening platform named ValidaTe that enables large scale evaluation of pHLA-binder interactions. We demonstrate its potential by measuring and analyzing over 30.000 binding curves for a high-affinity T cell Engaging Receptor towards a large pHLA library. Compared to a dataset obtained by conventional bio-layer interferometry measurements, we illustrate that a massively increased throughput (over 650 fold) is obtained by our microarray screening, paving the way for use in pre-clinical safety screening of pHLA-targeting drugs.

Internalization and coreceptor expression are critical for TLR2-mediated recognition of lipoteichoic acid in human peripheral blood.

Lipoteichoic acid (LTA), a ubiquitous cell wall component of Gram-positive bacteria, represents a potent immunostimulatory molecule. Because LTA of a mutant Staphylococcus aureus strain lacking lipoproteins (Deltalgt-LTA) has been described to be immunobiologically inactive despite a lack of ascertained structural differences to wild-type LTA (wt-LTA), we investigated the functional requirements for the recognition of Deltalgt-LTA by human peripheral blood cells. In this study, we demonstrate that Deltalgt-LTA-induced immune activation critically depends on the immobilization of LTA and the presence of human serum components, which, to a lesser degree, was also observed for wt-LTA. Under experimental conditions allowing LTA-mediated stimulation, we found no differences between the immunostimulatory capacity of Deltalgt-LTA and wt-LTA in human blood cells, arguing for a limited contribution of possible lipoprotein contaminants to wt-LTA-mediated immune activation. In contrast to human blood cells, TLR2-transfected human embryonic kidney 293 cells could be activated only by wt-LTA, whereas activation of these cells by Deltalgt-LTA required the additional expression of TLR6 and CD14, suggesting that activation of human embryonic kidney 293 cells expressing solely TLR2 is probably mediated by residual lipoproteins in wt-LTA. Notably, in human peripheral blood, LTA-specific IgG Abs are essential for Deltalgt-LTA-mediated immune activation and appear to induce the phagocytic uptake of Deltalgt-LTA via engagement of FcgammaRII. In this study, we have elucidated a novel mechanism of LTA-induced cytokine induction in human peripheral blood cells that involves uptake of LTA and subsequent intracellular recognition driven by TLR2, TLR6, and CD14.

Mammalian Display Platform for the Maturation of Bispecific TCR-Based Molecules.

Bispecific T cell receptor (TCR)-based molecules capable of redirecting and activating T cells towards tumor cells represent a novel and promising class of biotherapeutics for the treatment of cancer. Usage of TCRs allows for targeting of intracellularly expressed and highly selective cancer antigens, but also requires a complex maturation process to increase the naturally low affinity and stability of TCRs. Even though TCR domains can be matured via phage and yeast display, these techniques share the disadvantages of non-human glycosylation patterns and the need for a later reformatting into the final bispecific format. Here, we describe the development and application of a Chinese Hamster Ovary (CHO) display for affinity engineering of TCRs in the context of the final bispecific TCR format. The recombinase-mediated cassette exchange (RCME)-based system allows for stable, single-copy integration of bispecific TCR molecules with high efficiency into a defined genetic locus of CHO cells. We used the system to isolate affinity-increased variants of bispecific T cell engaging receptor (TCER) molecules from a library encoding different CDR variants of a model TCR targeting preferentially expressed antigen in melanoma (PRAME). When expressed as a soluble protein, the selected TCER molecules exhibited strong reactivity against PRAME-positive tumor cells associated with a pronounced cytokine release from activated T cells. The obtained data support the usage of the CHO display-based maturation system for TCR affinity maturation in the context of the final bispecific TCER format.

Quantitative immunopeptidomics reveals a tumor stroma-specific target for T cell therapy.

T cell receptor (TCR)-based immunotherapy has emerged as a promising therapeutic approach for the treatment of patients with solid cancers. Identifying peptide-human leukocyte antigen (pHLA) complexes highly presented on tumors and rarely expressed on healthy tissue in combination with high-affinity TCRs that when introduced into T cells can redirect T cells to eliminate tumor but not healthy tissue is a key requirement for safe and efficacious TCR-based therapies. To discover promising shared tumor antigens that could be targeted via TCR-based adoptive T cell therapy, we employed population-scale immunopeptidomics using quantitative mass spectrometry across ~1500 tumor and normal tissue samples. We identified an HLA-A*02:01-restricted pan-cancer epitope within the collagen type VI α-3 (COL6A3) gene that is highly presented on tumor stroma across multiple solid cancers due to a tumor-specific alternative splicing event that rarely occurs outside the tumor microenvironment. T cells expressing natural COL6A3-specific TCRs demonstrated only modest activity against cells presenting high copy numbers of COL6A3 pHLAs. One of these TCRs was affinity-enhanced, enabling transduced T cells to specifically eliminate tumors in vivo that expressed similar copy numbers of pHLAs as primary tumor specimens. The enhanced TCR variants exhibited a favorable safety profile with no detectable off-target reactivity, paving the way to initiate clinical trials using COL6A3-specific TCRs to target an array of solid tumors.

High-throughput peptide-MHC complex generation and kinetic screenings of TCRs with peptide-receptive HLA-A*02:01 molecules.

Major histocompatibility complex (MHC) class I molecules present short peptide ligands on the cell surface for interrogation by cytotoxic CD8+ T cells. MHC class I complexes presenting tumor-associated peptides such as neoantigens represent key targets of cancer immunotherapy approaches currently in development, making them important for efficacy and safety screenings. Without peptide ligand, MHC class I complexes are unstable and decay quickly, making the production of soluble monomers for analytical purposes labor intensive. We have developed a disulfide-stabilized HLA-A*02:01 molecule that is stable without peptide but can form peptide-MHC complexes (pMHCs) with ligands of choice in a one-step loading procedure. We illustrate the similarity between the engineered mutant and the wild-type molecule with respect to affinity of wild-type or affinity-matured T cell receptors (TCRs) and present a crystal structure corroborating the binding kinetics measurements. In addition, we demonstrate a high-throughput binding kinetics measurement platform to analyze the binding characteristics of bispecific TCR (bsTCR) molecules against diverse pMHC libraries produced with the disulfide-stabilized HLA-A*02:01 molecule. We show that bsTCR affinities for pMHCs are indicative of in vitro function and generate a bsTCR binding motif to identify potential off-target interactions in the human proteome. These findings showcase the potential of the platform and the engineered HLA-A*02:01 molecule in the emerging field of pMHC-targeting biologics.

IL-10 release requires stronger toll-like receptor 4-triggering than TNF: a possible explanation for the selective effects of heterozygous TLR4 polymorphism Asp(299)Gly on IL-10 release.

The toll-like receptor 4 Asp(299)Gly polymorphism results in an inactive receptor. Heterozygosis is associated with reduced LPS-inducible IL-10 protein and IL-10 mRNA from blood leukocytes and isolated monocytes, while numerous other mediators are not affected. We could exclude that this effect is due to the differences in the kinetics of IL-10 release, in the expression of total surface TLR4 or in LPS-binding to monocytes between subjects heterozygous for the Asp(299)Gly polymorphism or homozygous carriers of the wild-type allele. Furthermore, we could show that IL-10 induction in general requires stronger LPS-triggering than TNF and is more sensitive to LPS inhibitors. The lower number of responsive wild-type TLR4 receptors on monocytes of heterozygotes may explain why only IL-10 release is affected.

Evaluation of transient-evoked otoacoustic emissions in a healthy 1 to 10 year pediatric cohort in Sub-Saharan Africa.

OBJECTIVE: Transient-evoked otoacoustic emissions (TEOAEs) monitor cochlear function. High pass rates have been reported for industrialized countries. Pass rates in low and middle income countries such as Sub-Saharan Africa are rare, essentially lower and available for children up to 4 years of age and frequently based on hospital recruitments. This study aims at providing additional TEOAE pass rates of a healthy Sub-Saharan cohort aged 1-10 years with data from Gabon, Ghana and Kenya. Potentially confounding factors (recruitment site, age) are taken into consideration. METHODS: Healthy children were recruited in hospitals, schools and kindergartens. Inclusion criteria were age 1-10 years and normal otoscopic findings. Exclusion criteria were any sickness or physical ailment potentially impairing the hearing capacity. Five measurements per ear were performed with Capella Cochlear Emission Analyzer (MADSEN, Germany). An overall wave reproducibility of above 60% served as pass-criterion. Pass rates were compared between recruitment sites and age groups (1-5 and 6-10 years). RESULTS: Overall pass rate was 87.5% (n = 264; 231 passes vs. 33 fails). Of these 84.0% of hospital recruited children passed (n = 156; 131 passes vs. 25 fails), compared to 92.6% of community recruitments (n = 108; 100 passes vs. 8 fails), which was significantly different p = 0.039). If analyzed by age groups, this difference was only observed in children younger than 6 years (p = 0.007). CONCLUSION: Hospitals as recruitment sites for healthy controls seem to affect TEOAE pass rates. We advise for a cautious approach when recruiting healthy TEOAE control collectives under the age of 6 in a hospital setting. In children older than 6 years conventional pure-tone audiometry remains the standard method for hearing screening.

Antigens of persistent Chlamydia pneumoniae within coronary atheroma from patients undergoing heart transplantation.

AIMS: In order for Chlamydia pneumoniae to play a causative role in chronic human disease, it would need to persist within infected tissue for extended periods of time. Current theory suggests that C pneumoniae may persist at the site of infection via an alternative replicative form, known as an aberrant body. METHODS: A panel of C pneumoniae-specific antibodies upregulated by the aberrant body was used to probe tissue specimens from the coronary atheroma from 13 explanted hearts to identify patterns of reactivity in these tissues, as well as to determine the presence and prevalence of C pneumoniae aberrant bodies. RESULTS: Six of 13 patients had an ischaemic cardiomyopathy secondary to coronary atherosclerosis, while another six patients had an idiopathic, dilated cardiomyopathy. One additional patient, a young (24 years) woman with cardiomyopathy, had no history of atherosclerotic disease. Eleven patients were positive by immunohistochemistry with at least one antibody. Coronary arteries of the two other patients were negative by immunohistochemistry with all antibodies. One of these patients was the 24-year-old woman with grade I disease and no risk factors for coronary artery disease. CONCLUSIONS: The protein antigens of persistent C pneumoniae infection found in the atheromatous lesions from patients in this study could potentially be used as markers to detect such infections and some may be virulence factors or immunogens specific to C pneumoniae, thus serving as target molecules for diagnostic use or therapeutic intervention.

Human anti-Aß IgGs target conformational epitopes on synthetic dimer assemblies and the AD brain-derived peptide.

Soluble non-fibrillar assemblies of amyloid-beta (Aß) and aggregated tau protein are the proximate synaptotoxic species associated with Alzheimer's disease (AD). Anti-Aß immunotherapy is a promising and advanced therapeutic strategy, but the precise Aß species to target is not yet known. Previously, we and others have shown that natural human IgGs (NAbs) target diverse Aß conformers and have therapeutic potential. We now demonstrate that these antibodies bound with nM avidity to conformational epitopes on plate-immobilized synthetic Aß dimer assemblies, including synaptotoxic protofibrils, and targeted these conformers in solution. Importantly, NAbs also recognized Aß extracted from the water-soluble phase of human AD brain, including species that migrated on denaturing PAGE as SDS-stable dimers. The critical reliance on Aß's conformational state for NAb binding, and not a linear sequence epitope, was confirmed by the antibody's nM reactivity with plate-immobilized protofibrills, and weak uM binding to synthetic Aß monomers and peptide fragments. The antibody's lack of reactivity against a linear sequence epitope was confirmed by our ability to isolate anti-Aß NAbs from intravenous immunoglobulin using affinity matrices, immunoglobulin light chain fibrils and Cibacron blue, which had no sequence similarity with the peptide. These findings suggest that further investigations on the molecular basis and the therapeutic/diagnostic potential of anti-Aß NAbs are warranted.

Biomarker candidates of Chlamydophila pneumoniae proteins and protein fragments identified by affinity-proteomics using FTICR-MS and LC-MS/MS.

We report here an affinity-proteomics approach that combines 2D-gel electrophoresis and immunoblotting with high performance mass spectrometry to the identification of both full length protein antigens and antigenic fragments of Chlamydophila pneumoniae (C. pneumoniae). The present affinity-mass spectrometry approach effectively utilized high resolution FTICR mass spectrometry and LC-tandem-MS for protein identification, and enabled the identification of several new highly antigenic C. pneumoniae proteins that were not hitherto reported or previously detected only in other Chlamydia species, such as Chlamydia trachomatis. Moreover, high resolution affinity-MS provided the identification of several neo-antigenic protein fragments containing N- and C-terminal, and central domains such as fragments of the membrane protein Pmp21 and the secreted chlamydial proteasome-like factor (Cpaf), representing specific biomarker candidates.

Chlamydia pneumoniae-induced memory CD4+ T-cell activation in human peripheral blood correlates with distinct antibody response patterns.

Chlamydia pneumoniae is a frequent pathogen of the respiratory tract, and persistent infections with this obligate intracellular bacterium have been associated with different severe sequelae. Although T-cell activation during acute C. pneumoniae infections has been described, little is known about the frequency or the role of the C. pneumoniae-specific memory T cells that reside in the human body after the resolution of the infection. In the present study, the C. pneumoniae-induced T-cell responses in peripheral blood mononuclear cells of 56 healthy volunteers were analyzed and compared to the donor's serum antibody reactivity toward whole C. pneumoniae as well as recombinant C. pneumoniae antigens. Following short-term stimulation with C. pneumoniae, both gamma interferon (IFN-gamma)- and interleukin-2 (IL-2)-producing CD4(+) T-cell responses could be detected in 16 of 56 healthy individuals. C. pneumoniae-activated CD4(+) T cells expressed CD154, a marker for T-cell receptor-dependent activation, and displayed a phenotype of central memory T cells showing dominant IL-2 production but also IFN-gamma production. Interestingly, individuals with both IFN-gamma- and IL-2-producing responses showed significantly decreased immunoglobulin G reactivity toward C. pneumoniae RpoA and DnaK, antigens known to be strongly upregulated during chlamydial persistence, compared to IgG reactivity of seropositive individuals with no T-cell response or CD4(+) T-cell responses involving the production of a single cytokine (IFN-gamma or IL-2). Our results demonstrate that memory CD4(+) T cells responding to C. pneumoniae stimulation can be detected in the circulation of healthy donors. Furthermore, among seropositive individuals, the presence or the absence of dual IFN-gamma- and IL-2-producing T-cell responses was associated with distinct patterns of antibody responses toward persistence-associated C. pneumoniae antigens.

Immunoproteomic identification and serological responses to novel Chlamydia pneumoniae antigens that are associated with persistent C. pneumoniae infections.

The controversial discussion about the role of Chlamydia pneumoniae in atherosclerosis cannot be solved without a reliable diagnosis that allows discrimination between past and persistent infections. Using a proteomic approach and immunoblotting with human sera, we identified 31 major C. pneumoniae Ags originating from 27 different C. pneumoniae proteins. More than half of the proteins represent Chlamydia Ags not described previously. Using a comparative analysis of spot reactivity Pmp6, OMP2, GroEL, DnaK, RpoA, EF-Tu, as well as CpB0704 and CpB0837, were found to be immunodominant. The comparison of Ab-response patterns of sera from subjects with and without evidence for persisting C. pneumoniae, determined by multiple PCR analysis of PBMC and vasculatory samples, resulted in differential reactivity for 12 proteins, which is not reflected by reactivity of the sera in the microimmunofluorescence test, the current gold standard for serodiagnosis. Although reactivity of sera from PCR-positive donors was increased toward RpoA, MOMP, YscC, Pmp10, PorB, Pmp21, GroEL, and Cpaf, the reactivity toward YscL, Rho, LCrE, and CpB0837 was decreased, reflecting the altered protein expression of persisting C. pneumoniae in vitro. Our data provide the first evidence of a unique Ab-response pattern associated with persistent C. pneumoniae infections, which is a prerequisite for the serological determination of persistently infected patients.