Peripheral-derived regulatory T cells contribute to tumor-mediated immune suppression in a nonredundant manner.

Identifying tumor-mediated mechanisms that impair immunity is instrumental for the design of new cancer therapies. Regulatory T cells (Tregs) are a key component of cancer-derived immune suppression; however, these lymphocytes are necessary to prevent systemic autoimmunity in mice and humans, and thus, direct targeting of Tregs is not a clinical option for cancer patients. We have previously demonstrated that excising transcription factor Kruppel-like factor 2 (Klf2) within the T cell lineage blocks the generation of peripheral-derived Tregs (pTregs) without impairing production of thymic-derived Tregs. Using this mouse model, we have now demonstrated that eliminating pTregs is sufficient to delay/prevent tumor malignancy without causing autoimmunity. Cancer-bearing mice that expressed KLF2 converted tumor-specific CD4+ T cells into pTregs, which accumulated in secondary lymphoid organs and impaired further T cell effector activity. In contrast, pTreg-deficient mice retained cancer-specific immunity, including improved T cell infiltration into "cold" tumors, reduced T cell exhaustion in tumor beds, restricted generation of tumor-associated myeloid-derived suppressor cells, and the continued production of circulating effector T cells that arose in a cancer-dependent manner. Results indicate that tumor-specific pTregs are critical for early stages of cancer progression and blocking the generation of these inhibitory lymphocytes safely delays/prevents malignancy in preclinical models of melanoma and prostate cancer.

Dendrimer-enabled transformation of Chlamydia trachomatis.

Lack of a system for genetic manipulation of Chlamydia trachomatis has been a key challenge to advancing understanding the molecular genetic basis of virulence for this bacterial pathogen. We developed a non-viral, dendrimer-enabled system for transformation of this organism and used it to characterize the effects of inserting the common 7.5 kbp chlamydial plasmid into strain L2(25667R), a C. trachomatis isolate lacking it. The plasmid was cloned in pUC19 and the clone complexed to polyamidoamine dendrimers, producing ∼83 nm spherical particles. Nearly confluent McCoy cell cultures were infected with L2(25667R) and reference strain L2(434). At 16 h post-infection, medium was replaced with dendrimer-plasmid complexes in medium lacking additives (L2(25667R)) or with additive-free medium alone (L2(434)). Three h later complexes/buffer were removed, and medium was replaced; cultures were harvested at various times post-transformation for analyses. Real time PCR and RT-PCR of nucleic acids from transformed cultures demonstrated plasmid replication and gene expression. A previous report indicated that one or more plasmid-encoded product govern(s) transcription of the glycogen synthase gene (glgA) in standard strains. In L2(25667R) the gene is not expressed, but transformants of that strain given the cloned chlamydial plasmid increase glgA expression, as does L2(434). The cloned plasmid is retained, replicated, and expressed in transformants over at least 5 passages, and GFP is expressed when transformed into growing L2(25667R). This transformation system will allow study of chlamydial gene function in pathogenesis.

Attack rate of Chlamydia-induced reactive arthritis and effect of the CCR5-Delta-32 mutation: a prospective analysis.

OBJECTIVE: Factors that predispose patients to Chlamydia-induced reactive arthritis (CiReA) are poorly defined. Data indirectly suggest chemokine receptor-5 (CCR5)-delta-32 mutation might play a role in CiReA. We investigated the attack rate of CiReA and we hypothesized that the CCR5-delta-32 allele may modulate disease susceptibility. METHODS: Patients who tested positive for Chlamydia trachomatis after either (1) symptoms of an acute venereal disease or (2) sexual contact with an individual known to be positive for the same organism were followed in a prospective fashion. All patients were contacted at Week 6 after their acute infection and queried for symptoms of CiReA. Patients who had new-onset symptoms suggestive of CiReA were followed at Weeks 12, 26, and 52. All subjects were tested for CCR5-delta-32 mutation. RESULTS: A total of 365 study participants were enrolled, with average age 24.4 years, 201 men (55%) and 164 women (45%). We followed up with 149 patients (41%) at Week 6. Twelve of 149 participants (8.1%) had symptoms suggestive of CiReA at Week 6. None of these 12 patients was positive for the CCR5-delta-32 mutation. Of the 12 patients that had symptoms at Week 6, we were able to follow up with 7 through Week 52. All 7 had complete resolution of their symptoms by Week 26. Overall, 25/365 (6.8%) subjects were positive for the CCR5-delta-32 mutation. CONCLUSION: The attack rate of CiReA in our study was higher than previously reported, but the CCR5-delta-32 mutation does not seem to play a role in CiReA disease susceptibility.

Chlamydia trachomatis is present and metabolically active during the remitting phase in synovial tissues from patients with chronic Chlamydia-induced reactive arthritis.

BACKGROUND: Patients with chronic Chlamydia-induced reactive arthritis (ReA) often show a remitting-relapsing disease phenotype. Some information regarding bacterial and host responses to one another during active disease is available but no information for quiescence. This article presents the first molecular genetic insight into the behavior of bacterium and host during remitting ReA. METHODS: Synovial biopsies were procured from the knees of 4 patients with quiescent ReA by the Parker-Pearson technique. Nucleic acids prepared from them were analyzed by real-time polymerase chain reaction (PCR) and reverse transcription-PCR, and results were compared with data averaged from the knee synovial tissue samples of 10 patients with active ReA. RESULTS: Real-time PCR indicated that bacterial load in remitting samples was approximately 20% of that in active disease samples. Transcripts from the p60-encoding gene were equal to or higher than those seen in active disease. Messenger RNAs (mRNAs) from the paralog p60-encoding genes were equal to or lower than those of active disease. Host mRNAs encoding interleukin-10, tumor necrosis factor-α and interferon-γ were 4-fold lower than those in active disease samples, whereas monocyte chemotactic protein 1 and regulated upon activation, normal t-cell expressed, and secreted mRNA levels were equal to or higher. CONCLUSIONS: Bacterial load in synovial tissue of patients with remitting disease is lower than that of active disease, but mRNAs encoding proinflammatory proteins are equal to or higher than those of active disease. Transcription in the host is attenuated for cytokines and chemokines. These initial results demonstrate that organism is present and metabolically active in synovium during the remitting phase of chronic Chlamydia-induced ReA and that the genetic events characterizing quiescence are complex.

Dendrimer-enabled DNA delivery and transformation of Chlamydia pneumoniae.

The chlamydiae are important human pathogens. Lack of a genetic manipulation system has impeded understanding of the molecular bases of virulence for these bacteria. We developed a dendrimer-enabled system for transformation of chlamydiae and used it to characterize the effects of inserting the C. trachomatis plasmid into C. pneumoniae, which lacks any plasmids. The plasmid was cloned into modified yeast vector pEG(KG) and the clone complexed to polyamidoamine dendrimers, producing 50-100 nm spherical particles. HEp-2 cell cultures were infected with C. pneumoniae strain AR-39. Twenty-four hours later, medium was replaced for 3 hours with dendrimer-plasmid complexes, then removed and the medium replaced. Cultures were harvested at various times post-transformation. Real-time PCR and RT-PCR of nucleic acids from transformed cultures demonstrated plasmid replication and gene expression. The cloned plasmid was replicated and expressed in transformants over 5 passages. This system will allow study of chlamydial gene function, allowing development of novel dendrimer-based therapies. FROM THE CLINICAL EDITOR: This team of investigators developed a dendrimer-enabled system for transformation of chlamydiae and successfully utilized it to characterize the effects of inserting the C. trachomatis plasmid into C. pneumonia. This system will allow study of chlamydial gene function, allowing development of novel dendrimer-based therapies.

Dendrimer-enabled modulation of gene expression in Chlamydia trachomatis.

The obligate intracellular bacterium Chlamydia trachomatis is an important human pathogen. The genome of this organism is small but encodes many genes of currently unknown function that are thought to be involved in virulence. Lack of a system for genetic manipulation has been a key challenge to advancing the understanding of molecular genetics underlying virulence for this bacterium. We developed a dendrimer-enabled system for transformation of C. trachomatis, and used it to demonstrate the efficient and highly specific knockdown of transcript levels from targeted genes. Antisense, sense, and other control oligonucleotides targeting two sets of duplicated genes on the chlamydial chromosome were designed, commercially synthesized, and complexed with generation-4 polyamidoamine (PAMAM) dendrimers. The complexes were given to HEp-2 cell cultures infected for 16 h with C. trachomatis serovar K and then removed three hours later. Infected cultures were harvested 6 h after pulsing, and DNA and RNA/cDNA were prepared for assessment of transcript levels compared to those for the same genes in infected cultures, without dendrimer complexation. In all cases, the targeted gene complexed to dendrimer, but not its duplicate, showed up to 90% transcript attenuation. The duration of attenuation can be extended by repeated pulsing, and in some cases transcript levels from multiple genes can be attenuated in the same organism. This system will allow study of chlamydial gene function in pathogenesis, leading to more effective therapies to treat Chlamydia-induced diseases in a targeted manner.

The molecular basis for disease phenotype in chronic Chlamydia-induced arthritis.

Genital Chlamydia trachomatis infections can elicit an inflammatory arthritis in some individuals, and recent surprising studies have demonstrated that only ocular (trachoma) strains, not genital strains, of the organism are present in the synovial tissues of patients with the disease. This observation suggests an explanation for the small proportion of genitally-infected patients who develop Chlamydia-induced arthritis. Other recent studies have begun to identify the specific chlamydial gene products that elicit the synovial inflammatory response during both active and quiescent disease, although much more study will be required to complete the understanding of that complex process of host-pathogen interaction. Several newly developed experimental methods and approaches for study of the process will enable identification of new therapeutic targets, and possibly strategies for prevention of the disease altogether.

Combination antibiotics for the treatment of Chlamydia-induced reactive arthritis: is a cure in sight?

The inflammatory arthritis that develops in some patients subsequent to urogenital infection by the obligate intracellular bacterial pathogen Chlamydia trachomatis, and that induced subsequent to pulmonary infection with C. pneumoniae, both have proved difficult to treat in either their acute or chronic forms. Over the last two decades, molecular genetic and other studies of these pathogens have provided a good deal of information regarding their metabolic and genetic structures, as well as the detailed means by which they interact with their host cells. In turn, these insights have provided for the first time a window into the bases for treatment failures for the inflammatory arthritis. In this article we discuss the biological bases for those treatment failures, provide suggestions as to research directions that should allow improvement in treatment modalities, and speculate on how treatment regimens that currently show promise might be significantly improved over the near future using nanotechological means.

PAMAM dendrimer-azithromycin conjugate nanodevices for the treatment of Chlamydia trachomatis infections.

Chlamydia trachomatis is an important bacterial pathogen known to be etiological in genital infections, as well as several serious disease sequelae, including inflammatory arthritis. Chlamydiae can persist in infection, making treatment with antibiotics such as azithromycin (AZ) a challenge. The authors explore the use of neutral generation-4 polyamidoamine (PAMAM) dendrimers as intracellular drug-delivery vehicles into chlamydial inclusions. Azithromycin was successfully conjugated with the dendrimers, and the conjugate (D-AZ) released ≈ 90% of the drug over 16 hours. The conjugate readily entered both the Chlamydia-infected HEp-2 cells and the chlamydial inclusions. The conjugate was significantly better than free drug in preventing productive infections in the cells when added at the time of infection, and better in reducing the size and number of inclusions when added either 24 hours or 48 hours post infection. These studies show that dendrimers can deliver drugs efficiently to growing intracellular C. trachomatis, even if the organism is in the persistent form. FROM THE CLINICAL EDITOR: In this report, the use of polyamidoamine dendrimers as intracellular drug-delivery vehicles into chlamydial inclusions is investigated. This method results in efficient intracellular delivery of azithromycin to address chlamydia infection.

Functional CCR5 receptor protects patients with arthritis from high synovial burden of infecting Chlamydia trachomatis.

INTRODUCTION: The CCR5 chemokine receptor occurs in a wild-type (wt) and a nonfunctional deleted form (Δ32). Reports suggested that Chlamydia-induced reproductive tract pathology is attenuated in women bearing Δ32. The authors asked whether the mutation affects synovial prevalence and burden of Chlamydia trachomatis. METHODS: Polymerase chain reaction (PCR) defined CCR5 genotype in synovial tissue DNA from 218 individuals: 21 controls, 110 with reactive arthritis (ReA), 83 with undifferentiated oligoarthritis (UO), 4 with osteoarthritis (OA). Disease durations were 0.5 to 21 years. Additional PCR assays defined the presence of C trachomatis DNA. Bacterial load was assessed by real-time PCR in selected samples. RESULTS: Five controls were wt/Δ32, 16 were wt/wt; 2 of 21 controls (both wt/wt) were PCR positive for C trachomatis. Eighty-five (44%) patients with arthritis were PCR positive for C trachomatis (69 ReA and 16 UO). For patients with ReA, 14 (13%) had wt/Δ32, 10 (71%) of whom were PCR positive. Nineteen patients with UO (23%) were wt/Δ32, with 1 (1%) PCR positive. No differences existed for gender or other factors. One patient with OA had wt/Δ32. In ReA and UO samples, wt/Δ32 heterozygotes had a 5- to 10-fold higher bacterial burden than did wt/wt patients (P = 0.03), regardless of diagnosis. CONCLUSION: These results indicate that the wt/wt genotype is associated with attenuated synovial bacterial load compared with loads in wt/Δ32 patients. Although no alleles other than Δ32 were assessed, our data suggest that this allele provides little/no protection from ReA in patients infected with Chlamydia- but it may provide some protection in patients with UO. The basis of this possible differential effect of CCR5 genotype is under study.

The pathogenic role of Chlamydia in spondyloarthritis.

PURPOSE OF REVIEW: Topics relating to the spondyloarthropathies have been reviewed recently, but the detailed roles of Chlamydia trachomatis and C. pneumoniae in induction of spondyloarthritis have not been discussed. This review focuses on new information regarding how these pathogens elicit joint disease, with emphasis on C. trachomatis in its role in Chlamydia-induced reactive arthritis. RECENT FINDINGS: Molecular methods continue to provide insights into the molecular genetic and cell biologic basis for chlamydial pathogenesis. For chlamydiae, residence in the synovium in patients with acute or chronic Chlamydia-induced arthritis involves organisms in an unusual infection state designated persistence. The profiles of overall metabolism and gene expression characteristic of chlamydial persistence have been assessed and unusual aspects noted, including transcriptional attenuation of one hsp60 paralog and upregulation of expression for another. Strain determinations have demonstrated that genital serotypes of C. trachomatis are not present in the joint; rather, inflammation at that site is elicited by ocular serotypes of the organism. This indicates that much remains to be learned concerning the biology of chlamydial dissemination from the urogenital tract. Analyses of undifferentiated spondyloarthritis continue to suggest that chlamydiae, and perhaps other pathogens function in the etiology of the disease. Progress has been made in developing effective treatment for patients with Chlamydia-induced arthritis. SUMMARY: Molecular genetic analyses regarding the role of chlamydiae in induction of inflammatory arthritis have increased our detailed understanding of the pathogenic mechanisms utilized by these organisms in the joint. Importantly, progress has been made in developing effective therapies for treatment of Chlamydia-induced arthritis.

Patients with Chlamydia-associated arthritis have ocular (trachoma), not genital, serovars of C. trachomatis in synovial tissue.

Some individuals with a genital Chlamydia trachomatis infection develop inflammatory arthritis, but it is unknown whether particular chlamydial serovar(s) engender the disease more often than others. We defined serovar in synovial tissues from arthritis patients infected with this organism. DNA from synovial biopsies of 36 patients with PCR-confirmed synovial C. trachomatis was analyzed. Diagnoses included reactive arthritis, undifferentiated oligoarthritis, rheumatoid arthritis, and osteoarthritis. The chlamydial omp1 and trpA genes were amplified, cloned, and 10 or more clones from each sample were sequenced. The cytotoxin locus also was analyzed. omp1 sequences showed 2 patients having only C. trachomatis A serovar, 1 with only B, and 33 having only C, all ocular serovars. Analyses of trpA and the cytotoxin locus uniformly displayed standard ocular serovar characteristics for each patient. Identification of ocular chlamydial serovars in the synovia of arthritis patients is unexpected. These observations suggest that urogenital chlamydial infections, while consisting primarily of organisms of genital serovars, include some of ocular serovar(s). They further suggest that during such infections unknown selection pressures favor establishment of the latter in the synovium to the exclusion of genital serovar chlamydiae.

Molecular biology of infectious agents in chronic arthritis.

Severe and chronic inflammatory arthritis sometimes follows urogenital infection with Chlamydia trachomatis or gastrointestinal infection with enteric bacterial pathogens. A similar clinical entity can be elicited by the respiratory pathogen Chlamydophila (Chlamydia) pneumoniae. Arthritogenesis does not universally require viable enteric bacteria in the joint. In arthritis induced by either of the chlamydial species, organisms are viable and metabolically active in the synovium. They exist in a "persistent" state of infection. Conventional antibiotic treatment of patients with Chlamydia-induced arthritis is largely ineffective. The authors outline the current understanding of the molecular genetic and biologic aspects underlying bacterially-induced joint pathogenesis, available information regarding host-pathogen interaction at that site, and several directions for future study to inform development of more effective therapies.

Chlamydiae as etiologic agents in chronic undifferentiated spondylarthritis.

OBJECTIVE: The majority of patients with Chlamydia-induced reactive arthritis do not present with the classic triad of arthritis, conjunctivitis/iritis, and urethritis. Moreover, acute chlamydial infections are often asymptomatic. The aim of the present study was to assess the prevalence of synovial Chlamydia trachomatis and Chlamydia pneumoniae infections in patients with chronic undifferentiated spondylarthritis (uSpA). METHODS: Study patients met the European Spondylarthropathy Study Group criteria for SpA, without evidence of ankylosing spondylitis, psoriasis, inflammatory bowel disease, or preceding dysentery. Symptoms were present for >or=6 months. Each patient underwent a synovial biopsy; tissue and concomitantly obtained peripheral blood mononuclear cells (PBMCs) were analyzed by polymerase chain reaction (PCR) for C trachomatis and C pneumoniae DNA. Other data collected on the day of the biopsy included standard demographic information and medical history, including any known history of C trachomatis or C pneumoniae. Physical examination (including joint count, evaluation for dactylitis and/or enthesitis, and skin examination) and HLA-B27 typing were performed. Synovial tissue (ST) samples from 167 patients with osteoarthritis (OA) were used as controls. RESULTS: Twenty-six patients met the entry criteria and underwent synovial biopsy (25 knee, 1 wrist). Sixteen of them (62%) were positive for C trachomatis and/or C pneumoniae DNA (10 for C trachomatis, 4 for C pneumoniae, and 2 for both). PCR analysis of ST revealed the presence of Chlamydia significantly more frequently in patients with uSpA than in OA controls (P<0.0001). No specific clinical characteristics differentiated Chlamydia-positive from Chlamydia-negative patients. PBMCs from 4 of the 26 uSpA patients (15%) were positive for Chlamydia, and Chlamydia was found in ST from 2 of these 4 patients. No significant correlation between PCR positivity and HLA-B27 positivity was found. CONCLUSION: The frequency of Chlamydia-positive ST samples, as determined by PCR, was found to be significantly higher in patients with uSpA than in patients with OA. Our results suggest that in many patients with uSpA, chlamydial infection, which is often occult, may be the cause.

Lack of evidence for bacterial infections in skin in patients with systemic sclerosis.

BACKGROUND: In some patients with systemic sclerosis (SSc), persistent bacterial infection involving dermal microvascular endothelial cells may result in endothelial injury, leading to the obliterative microvasculopathy typical of the disease. Alternatively, in some patients with SSc persistent bacterial infection involving activated dermal fibroblasts or other cells found in scleroderma skin might result in the fibrosing features of this disease. In this study, we investigated bacterial infection in skin in patients with SSc. METHODS: Chlamydiae of many species are known to undergo persistent infection. Highly sensitive and specific PCR assays targeting chromosomal DNA sequences from C. trachomatis and C. pneumoniae were used to screen skin biopsy samples from each of 18 patients and 26 control individuals. Additional screening was performed using a highly sensitive "pan-bacteria" PCR screening system. RESULTS: All patient and control samples proved to be PCR-negative for both chlamydial species. Similarly, all patient and control samples were PCR-negative when the broad range pan-bacteria assay system was used. CONCLUSION: Although some caveats apply, the data presented here do not support the contention that persistent bacterial infections play an important role in the pathogenesis of SSc.

The transcript profile of persistent Chlamydophila (Chlamydia) pneumoniae in vitro depends on the means by which persistence is induced.

Expression of specific bacterial genes is differentially regulated during persistent, vs. active, chlamydial infection. Transcript patterns were examined using real-time reverse transcriptase-PCR in four in vitro models of persistence for Chlamydia pneumoniae strain CWL 029, using HeLa cells and normal human monocytes as host. Differential expression of genes encoding cell division proteins was variable when persistence was induced by interferon-gamma, penicillin G, or deferoxamine mesylate treatment, and in the monocyte model of persistence. Expression of genes encoding hsp60s and those specifying sigma-factors also was variable among models. These in vitro observations indicate that chlamydial persistence is not characterizable by a single transcript profile under all circumstances, supporting the idea that persistent infection in vivo is a complex, flexible strategy that promotes long-term survival of these organisms. Each model system studied here can provide information regarding the molecular characteristics of persistent C. pneumoniae infection. However, we do not know which aspect(s) of which model correspond to in vivo disease or other contexts.

Initial characterization of Chlamydophila (Chlamydia) pneumoniae cultured from the late-onset Alzheimer brain.

Previous studies from this laboratory provided evidence that the intracellular bacterial pathogen Chlamydophila (Chlamydia) pneumoniae is present in the late-onset Alzheimer's disease (AD) brain. Here we report culture of the organism from two AD brain samples, each of which originated from a different geographic region of North America. Culturable organisms were detectable after one and two passages in HEp-2 cells for the two samples. Both isolates, designated Tor-1 and Phi-1, were demonstrated to be authentic C. pneumoniae using PCR assays targeting the C. pneumoniae-specific genes Cpn0695, Cpn1046, and tyrP. Assessment of inclusion morphology and quantitation of infectious yields in epithelial (HEp-2), astrocytic (U-87 MG), and microglial (CHME-5) cell lines demonstrated an active, rather than a persistent, growth phenotype for both isolates in all host cell types. Sequencing of the omp1 gene from each isolate, and directly from DNA prepared from several additional AD brain tissue samples PCR-positive for C. pneumoniae, revealed genetically diverse chlamydial populations. Both brain isolates carry several copies of the tyrP gene, a triple copy in Tor-1, and predominantly a triple copy in Phi-1 with a minor population component having a double copy. This observation indicated that the brain isolates are more closely related to respiratory than to vascular/atheroma strains of C. pneumoniae.

Chlamydophila pneumoniae and the etiology of late-onset Alzheimer's disease.

Sporadic, late-onset Alzheimer's disease (LOAD) is a non-familial, progressive neurodegenerative disease that is now the most common and severe form of dementia in the elderly. That dementia is a direct result of neuronal damage and loss associated with accumulations of abnormal protein deposits in the brain. Great strides have been made in the past 20 years with regard to understanding the pathological entities that arise in the AD brain, both for familial AD ( approximately 5% of all cases) and LOAD ( approximately 95% of all cases). The neuropathology observed includes: neuritic senile plaques (NSPs), neurofibrillary tangles (NFTs), neuropil threads (NPs), and often deposits of cerebrovascular amyloid. Genetic, biochemical, and immunological analyses have provided a relatively detailed knowledge of these entities, but our understanding of the "trigger" events leading to the many cascades resulting in this pathology and neurodegeneration is still quite limited. For this reason, the etiology of AD, in particular LOAD, has remained elusive. However, a number of recent and ongoing studies have implicated infection in the etiology and pathogenesis of LOAD. This review focuses specifically on infection with Chlamydophila (Chlamydia) pneumoniae in LOAD and how this infection may function as a "trigger or initiator" in the pathogenesis of this disease.

Up-regulation of a cellular protein at the translational level by a retrovirus.

Mink cell focus-forming (MCF) murine leukemia viruses (MLVs) are the etiologic agent of thymic lymphoma in mice. We have observed previously that superinfection by MCF13 MLV of certain cell types, such as preleukemic thymic lymphocytes and cultured mink epithelial cells, results in the accumulation of the viral envelope precursor polyprotein, leading to the induction of endoplasmic reticulum (ER) stress. In this study, we demonstrate that the induction of ER stress by MCF13 MLV infection results in an increase in the phosphorylation of the alpha-subunit of eukaryotic initiation factor 2. In cells in which this occurs, we have detected an up-regulation of the cellular inhibitor of apoptosis protein 1 (c-IAP1). The results of real-time RT-PCR quantification of message levels and protein turnover assays indicate that up-regulation of c-IAP1 occurs at the translational level. Elevation of c-IAP1 levels at a posttranscriptional step was detectable in MCF13 MLV-induced thymic lymphomas and chronically infected mink epithelial cells. The ability of a simple retrovirus to regulate cellular gene expression at the translational level may be an important mechanism that contributes to pathogenesis.

Apolipoprotein E4 enhances attachment of Chlamydophila (Chlamydia) pneumoniae elementary bodies to host cells.

Chlamydophila (Chlamydia) pneumoniae is an intracellular respiratory pathogen known to cause community-acquired pneumonia. Infection with this organism has been associated with atherosclerosis, inflammatory arthritis, and other chronic diseases, many of which also have been associated with possession of the epsilon4 allele at the APOE locus on (human) chromosome 19. An earlier study from this laboratory suggested that some relationship exists between apolipoprotein E4 (apoE4), the product of the epsilon4 allele, and the pathobiology of C. pneumoniae. A standard attachment assay and real time PCR targeting a sequence on the C. pneumoniae chromosome were used to monitor host cell binding of elementary bodies (EB) of that organism. Our data indicate that 3-fold more EB of strain AR-39 attach to an epsilon3 homozygous human cell line transfected with a plasmid expressing the epsilon4 coding sequence than to the same cell line harboring empty vector, vector containing an irrelevant insert sequence, or vector containing the DNA sequence encoding apoE3. The quantitative real time data were confirmed by immunolabeling of chlamydial inclusions in parallel attachment and infection assays. Experiments using Chlamydophila trachomatis EB showed no enhancement of attachment in the presence of the epsilon4 allele in any assays. These observations indicate that apoE4 enhances attachment of C. pneumoniae EB, but not those of C. trachomatis, to target host cells.