Identification of Chlamydia pneumoniae within human choroidal neovascular membranes secondary to age-related macular degeneration

Association of NLRPs with pathogenesis of dry age-related macular degeneration

BACKGROUND

Age-related macular degeneration (AMD) is the leading cause of blindness in the elderly population, and Dry AMD is the most common clinical subtype. However, effective measures for the early diagnosis and treatment of dry AMD have not been proposed. In recent years, NOD-like receptors (NLRs) have received attention in the study of AMD as an important class of pattern recognition receptors. We attempted to elucidate the pathogenesis of NLRs in dry AMD from the perspective of chronic inflammation.

METHODS

This study involved 13 patients with dry AMD, 10 age- and sex-matched normal population without any history of disease and 8 patients with wet AMD as controls. Using RT-qPCR, the mRNA expression levels of NLRs in peripheral blood peripheral blood mononuclear cells (PBMCs) were compared to analyze the statistical differences in the expression contents among the three populations.

RESULTS

The relative RNA expression of nucleotide-binding oligomerization-like receptor protein 12 (NLRP12) with negative regulation of inflammation was significantly lower in dry AMD patients than in normal people and wet AMD patients. And NLRX1, which also has an anti-inflammatory effect, was lower in dry AMD patients than in wet AMD patients. However, NLRP3 with proinflammatory effect was significantly expressed in wet AMD.

CONCLUSION

The significant decrease in NLRP12 in dry AMD may become a breakthrough in the study of dry AMD and systemic chronic inflammatory response. However, NLRP3 may have a more important role in wet AMD.

Early-life peripheral infections reprogram retinal microglia and aggravate neovascular age-related macular degeneration in later life

Pathological neovascularization in age-related macular degeneration (nvAMD) drives the principal cause of blindness in the elderly. While there is a robust genetic association between genes of innate immunity and AMD, genome-to-phenome relationships are low, suggesting a critical contribution of environmental triggers of disease. Possible insight comes from the observation that a past history of infection with pathogens such as Chlamydia pneumoniae, or other systemic inflammation, can predispose to nvAMD in later life. Using a mouse model of nvAMD with prior C. pneumoniae infection, endotoxin exposure, and genetic ablation of distinct immune cell populations, we demonstrated that peripheral infections elicited epigenetic reprogramming that led to a persistent memory state in retinal CX3CR1+ mononuclear phagocytes (MNPs). The immune imprinting persisted long after the initial inflammation had subsided and ultimately exacerbated choroidal neovascularization in a model of nvAMD. Single-cell assay for transposase-accessible chromatin sequencing (scATAC-seq) identified activating transcription factor 3 (ATF3) as a central mediator of retina-resident MNP reprogramming following peripheral inflammation. ATF3 polarized MNPs toward a reparative phenotype biased toward production of proangiogenic factors in response to subsequent injury. Therefore, a past history of bacterial endotoxin-induced inflammation can lead to immunological reprograming within CNS-resident MNPs and aggravate pathological angiogenesis in the aging retina.

COVID-19 Morbidity and Severity in Patients With Age-Related Macular Degeneration: A Korean Nationwide Cohort Study

PURPOSE

To determine the potential association between age-related macular degeneration (AMD), a representative chronic age-related degenerative disease of the retina associated with inflammation and aging, and susceptibility to SARS-CoV-2 infection and severe COVID-19 outcomes.

DESIGN

Nationwide cohort study with propensity-score matching.

METHODS

A population-based nationwide cohort in Korea was examined. Data were obtained from the Health Insurance Review & Assessment Service of Korea, including all patients aged ≥40 years who underwent SARS-CoV-2 testing in South Korea between January 1, 2020 and May 15, 2020 (excluding self-referral). The primary outcome was SARS-CoV-2 test positivity and the secondary outcome was severe clinical outcome of COVID-19.

RESULTS

The unmatched cohort consisted of 135,435 patients who were tested for SARS-CoV-2: 4531 patients (3.3%) tested positive for SARS-CoV-2 and 5493 (4.1%) had AMD. After propensity score matching, exudative AMD was associated with an increased likelihood of susceptibility to SARS-CoV-2 infection (adjusted odds ratio [aOR], 1.50; 95% confidence interval [CI], 1.03-2.25), and a considerably greater risk of severe clinical outcomes of COVID-19 (aOR, 2.26; 95% CI, 1.02-5.26), but not any AMD and non-exudative AMD.

CONCLUSIONS

In a Korean nationwide cohort, data suggest that clinicians should be aware of the greater risk of susceptibility to severe clinical outcomes of COVID-19 in patients with exudative AMD. These findings provide an improved understanding of the relationship between the pathogenesis of COVID-19 and chronic neurological disorders.

RISK OF AGE-RELATED MACULAR DEGENERATION IN PATIENTS WITH PERIODONTITIS: A Nationwide Population-Based Cohort Study

PURPOSE

Periodontitis is an inflammatory disease that results in loss of connective tissue and bone support. Evidence shows a possible relationship between periodontitis and age-related macular degeneration (AMD).

METHODS

This population-based cohort study was conducted using data from the National Health Insurance Research Database in Taiwan, with a 13-year follow-up, to investigate the risk of AMD in patients with periodontitis. The periodontitis cohort included patients with newly diagnosed periodontitis between 2000 and 2012. The nonperiodontitis cohort was frequency-matched with the periodontitis cohort by age and sex, with a sample size of 41,661 in each cohort.

RESULTS

Patients with periodontitis had an increased risk of developing AMD compared with individuals without periodontitis (5.95 vs. 3.41 per 1,000 person-years, adjusted hazard ratio = 1.58 [95% confidence interval, 1.46-1.70]). The risk of developing AMD remained significant after stratification by age (adjusted hazard ratio = 1.48 [1.34-1.64] for age <65 years and 1.76 [1.57-1.97] for age ≥65 years), sex (adjusted hazard ratio = 1.40 [1.26-1.55] for women and 1.82 [1.63-2.04] for men), and presence of comorbidity (adjusted hazard ratio = 1.52 [1.40-1.66] for with comorbidity and 1.92 [1.63-2.26] for without comorbidity). In addition, patients with periodontitis showed an increased incidence for both nonexudative type AMD (5.43 vs. 3.13 per 1,000 person-years) and exudative type AMD (0.52 vs. 0.28 per 1,000 person-years).

CONCLUSION

People with periodontitis could be at a greater risk of developing AMD than those without periodontitis. However, we need more evidence to support this association.

[Association between age-related macular degeneration and periodontal disease]

PURPOSE

To evaluate the association between age-related macular degeneration (AMD) and periodontal disease, two frequent conditions in the elderly, with some risk factors in common.

METHODS

Single center, pilot, case-control study performed in a center specialized in the diagnosis and management of AMD. Periodontal status was evaluated in 43 AMD patients and 19 controls. Fundus examination and a complete periodontal examination were performed in all subjects.

RESULTS

AMD patients have a greater percentage of 3-4mm clinical attachment loss compared to controls (47% vs. 38%, [P=0.039]). However, no significant difference was found between the groups with regard to the prevalence of severe periodontitis.

CONCLUSIONS

These results suggest an association between AMD and attachment loss characteristic of periodontal disease and support the need for larger prospective studies to elucidate the relationships between these 2 highly prevalent and potentially severe diseases.

Incomplete response to Anti-VEGF therapy in neovascular AMD: Exploring disease mechanisms and therapeutic opportunities

Intravitreal anti-vascular endothelial growth factor (VEGF) drugs have revolutionized the treatment of neovascular age-related macular degeneration (NVAMD). However, many patients suffer from incomplete response to anti-VEGF therapy (IRT), which is defined as (1) persistent (plasma) fluid exudation; (2) unresolved or new hemorrhage; (3) progressive lesion fibrosis; and/or (4) suboptimal vision recovery. The first three of these collectively comprise the problem of persistent disease activity (PDA) in spite of anti-VEGF therapy. Meanwhile, the problem of suboptimal vision recovery (SVR) is defined as a failure to achieve excellent functional visual acuity of 20/40 or better in spite of sufficient anti-VEGF treatment. Thus, incomplete response to anti-VEGF therapy, and specifically PDA and SVR, represent significant clinical unmet needs. In this review, we will explore PDA and SVR in NVAMD, characterizing the clinical manifestations and exploring the pathobiology of each. We will demonstrate that PDA occurs most frequently in NVAMD patients who develop high-flow CNV lesions with arteriolarization, in contrast to patients with capillary CNV who are highly responsive to anti-VEGF therapy. We will review investigations of experimental CNV and demonstrate that both types of CNV can be modeled in mice. We will present and consider a provocative hypothesis: formation of arteriolar CNV occurs via a distinct pathobiology, termed neovascular remodeling (NVR), wherein blood-derived macrophages infiltrate the incipient CNV lesion, recruit bone marrow-derived mesenchymal precursor cells (MPCs) from the circulation, and activate MPCs to become vascular smooth muscle cells (VSMCs) and myofibroblasts, driving the development of high-flow CNV with arteriolarization and perivascular fibrosis. In considering SVR, we will discuss the concept that limited or poor vision in spite of anti-VEGF may not be caused simply by photoreceptor degeneration but instead may be associated with photoreceptor synaptic dysfunction in the neurosensory retina overlying CNV, triggered by infiltrating blood-derived macrophages and mediated by Müller cell activation Finally, for each of PDA and SVR, we will discuss current approaches to disease management and treatment and consider novel avenues for potential future therapies.

Immunological Aspects of Age-Related Macular Degeneration

Increasing evidence over the past two decades points to a pivotal role for immune mechanisms in age-related macular degeneration (AMD) pathobiology. In this chapter, we will explore immunological aspects of AMD, with a specific focus on how immune mechanisms modulate clinical phenotypes of disease and severity and how components of the immune system may serve as triggers for disease progression in both dry and neovascular AMD. We will briefly review the biology of the immune system, defining the role of immune mechanisms in chronic degenerative disease and differentiating from immune responses to acute injury or infection. We will explore current understanding of the roles of innate immunity (especially macrophages), antigen-specific immunity (T cells, B cells, and autoimmunity), immune amplifications systems, especially complement activity and the NLRP3 inflammasome, in the pathogenesis of both dry and neovascular AMD, reviewing data from pathology, experimental animal models, and clinical studies of AMD patients. We will also assess how interactions between the immune system and infectious pathogens could potentially modulate AMD pathobiology via alterations in in immune effector mechanisms. We will conclude by reviewing the paradigm of "response to injury," which provides a means to integrate various immunologic mechanisms along with nonimmune mechanisms of tissue injury and repair as a model to understand the pathobiology of AMD.

Periodontal Disease and Age-Related Macular Degeneration: A Meta-Analysis of 112,240 Participants

OBJECTIVE

Epidemiological studies have shown a correlation between periodontal disease (PD) and age-related macular degeneration (AMD). However, the results have been inconsistent, and no relevant meta-analysis has been performed on this topic. Hence, we performed a meta-analysis to evaluate whether the two diseases are related. Material and Methods. The PubMed, Embase, Cochrane Library, and Web of Science databases were searched up to April 20, 2020, for related articles. Two authors independently conducted literature screening and data extraction and then used the Stata 15.1 software to calculate the relative risk (RRs) and 95% confidence intervals (CIs) to assess the association between PD and AMD.

RESULTS

A total of 5 observational studies involving 112,240 participants and 5,005 AMD patients were included. The results of meta-analysis using the random-effects model showed that the incidence of AMD in PD patients was 1.35 times that of non-PD patients; the difference was statistically significant (RR = 1.35, 95%CI = 1.07-1.70, P = 0.011). Sensitivity analysis showed that the results were stable.

CONCLUSIONS

PD patients have a higher risk of AMD, but the causal relationship between PD and AMD has not been confirmed. Further research should be carried out to verify the exact relationship between the two.

A Proinflammatory Function of Toll-Like Receptor 2 in the Retinal Pigment Epithelium as a Novel Target for Reducing Choroidal Neovascularization in Age-Related Macular Degeneration

Current treatments for choroidal neovascularization, a major cause of blindness for patients with age-related macular degeneration, treat symptoms but not the underlying causes of the disease. Inflammation has been strongly implicated in the pathogenesis of choroidal neovascularization. We examined the inflammatory role of Toll-like receptor 2 (TLR2) in age-related macular degeneration. TLR2 was robustly expressed by the retinal pigment epithelium in mouse and human eyes, both normal and with macular degeneration/choroidal neovascularization. Nuclear localization of NF-κB, a major downstream target of TLR2 signaling, was detected in the retinal pigment epithelium of human eyes, particularly in eyes with advanced stages of age-related macular degeneration. TLR2 antagonism effectively suppressed initiation and growth of spontaneous choroidal neovascularization in a mouse model, and the combination of anti-TLR2 and antivascular endothelial growth factor receptor 2 yielded an additive therapeutic effect on both area and number of spontaneous choroidal neovascularization lesions. Finally, in primary human fetal retinal pigment epithelium cells, ligand binding to TLR2 induced robust expression of proinflammatory cytokines, and end products of lipid oxidation had a synergistic effect on TLR2 activation. Our data illustrate a functional role for TLR2 in the pathogenesis of choroidal neovascularization, likely by promoting inflammation of the retinal pigment epithelium, and validate TLR2 as a novel therapeutic target for reducing choroidal neovascularization.

The association between periodontal disease and age-related macular degeneration in the Korea National health and nutrition examination survey: A cross-sectional observational study

Periodontal disease (PD) is associated with various systemic diseases. We investigated the association between PD and age-related macular degeneration (AMD).For this population-based, cross-sectional study, we enrolled 13,072 adults at least 40 years of age with gradable retinal fundus photographs and community periodontal index (CPI) data from the Korean National Health and Nutrition Examination Survey (KNHANES) (2008-2010 and 2012). Participants were divided into a middle age group (age ≤62 years) and old age group (age >62 years). PD was divided into 2 categories of mild and severe. Logistic regression analysis was used to evaluate the association between PD and AMD (early and late).The prevalence of PD and AMD in the study population was 37.4% ± 0.8% and 5.6% ± 0.2%, respectively. Overall, there was no significant difference in the proportion of participants with PD between those with and without AMD. Only participants with AMD in the middle age group had more any PD than those without AMD (P = 0.031). Multivariate logistic regression model after adjusting for all confounding factors showed that PD was not significantly associated with AMD (odds ratio [OR] 1.03, 95% confidence interval [CI] 0.86-1.22). However, according to degree of PD, participants with severe PD in the middle age group were 1.61 times more likely to have AMD (OR 1.61, 95% CI 1.02-2.54).Our data, collected from an Asian population, showed that only severe PD is independently associated with AMD in individuals aged 62 years or younger.

MMP20 and ARMS2/HTRA1 Are Associated with Neovascular Lesion Size in Age-Related Macular Degeneration

PURPOSE

Age-related macular degeneration (AMD) is the leading cause of severe visual impairment. Despite treatment, a central scotoma often remains. The size of the scotoma depends on the lesion size of the choroidal neovascular membrane and significantly affects the patient's quality of life, and the lesion size of neovascularization also affects response to treatments. The aim of this study was to identify genes associated with the neovascular lesion size in neovascular AMD.

DESIGN

A genome-wide association study (GWAS).

PARTICIPANTS

We included 1146 Japanese patients with neovascular AMD.

METHODS

We performed a 2-stage GWAS for the lesion size of AMD as a quantitative trait among 1146 (first stage: 727, second stage: 419) Japanese patients with neovascular AMD. Lesion size was determined by the greatest linear dimension measured with fluorescein angiography examination before treatment. We examined the association between the genotypic distribution of each single nucleotide polymorphism (SNP) and the trait using an additive model adjusted for age and sex. To evaluate the associations between AMD development and SNPs associated with lesion size, we also performed a case-control study by using the genotype data from these 1146 Japanese patients as case subjects and the fixed dataset from the Nagahama Study as control subjects.

MAIN OUTCOME MEASURES

Genes associated with the lesion size in neovascular AMD.

RESULTS

In the discovery stage, rs10895322 in MMP20 showed a genome-wide significant P value of 6.95×10(-8), and rs2284665 in ARMS2/HTRA1 showed a P value of 1.55×10(-7). The associations of these 2 SNPs were successfully replicated in the replication stage, and a meta-analysis of both stages showed genome-wide significant P values (2.80×10(-9) and 4.41×10(-9), respectively). In a case-control study using 3248 Japanese subjects as controls, we could not find contribution of MMP20 rs10895322 for AMD development. Although MMP20 has been thought to be expressed only in dental tissues, we confirmed MMP20 expression in the human retina and retinal pigment epithelium/choroid with polymerase chain reaction.

CONCLUSIONS

The growth of choroidal neovascularization in AMD would be affected by 2 genes: MMP20, a newly confirmed gene expressed in the retina, and ARMS2/HTRA1, a well-known susceptibility gene for AMD.

PERIODONTAL DISEASE AND AGE-RELATED MACULAR DEGENERATION: Results From the National Health and Nutrition Examination Survey III

PURPOSE

To study the association between periodontal disease (PD) and age-related macular degeneration (AMD).

METHODS

For this cross-sectional analysis, 8,208 adults aged 40 years or older with retinal photographs graded for AMD were used from the National Health and Nutrition Examination Survey III. National Health and Nutrition Examination Survey III standardized dental measurements of PD status (defined as loss of >3 mm of attachment between the gum and tooth in at least 10% of sites measured). Participants were stratified into 60 years or younger and older than 60 years of age groups. Association between PD and AMD was assessed while controlling for sex, race, education, poverty income ratio, smoking, hypertension, body mass index, cardiovascular disease, and C-reactive protein.

RESULTS

In this population, a total of 52.30% had PD, and the prevalence of AMD was 11.45%. Logistic regression model controlled for confounders and stratified by age 60 years or younger versus older than 60 years showed PD to be independently associated with an increased risk for AMD (odds ratio = 1.96, 95% confidence interval = 1.22-3.14, P = 0.006) for those aged 60 years or younger but not for subjects older than 60 years (odds ratio = 1.32, confidence interval = 0.93-1.90, P = 0.120).

CONCLUSION

In this population-based study, PD is independently associated with AMD in those aged 60 years or younger.

Calcium, ARMS2 genotype, and Chlamydia pneumoniae infection in early age-related macular degeneration: a multivariate analysis from the Nagahama study

Although various risk factors have been identified for the development of age-related macular degeneration (AMD), risk factors of early AMD have been relatively under studied. We aimed to investigate AMD risk factors by evaluating multiple factors in association with large drusen, an important component of AMD, simultaneously. In a community-based cross-sectional survey in Japan, 971 large drusen cases and 3,209 controls were compared for 65 variables, including systemic, environmental, and genetic factors. The association and the effect size of each factor were evaluated with logistic regression analysis using a backward-elimination approach. Multivariate analyses identified a significant association in serum calcium level (odds ratio [OR] = 0.932, P = 1.05 × 10⁻³), ARMS2 A69S (rs10490924) genotype (OR = 1.046, P < 0.001), Chlamydia pneumoniae IgG (OR = 1.020, P = 0.0440), and age (OR = 1.013, P < 0.001) for large drusen. Hypocalcemia was observed in 7.2% of large drusen cases and in 5.5% of controls (P = 0.0490). C. pneumoniae infections was more frequent in large drusen cases (56.4%) than in conrols (51.7%, P = 0.00956). These results suggest that calcium, ARMS2 genotype, C. pneumonia infection, and age are significant factors in the development of the early stages of AMD.

The oxidative stress product carboxyethylpyrrole potentiates TLR2/TLR1 inflammatory signaling in macrophages

Oxidative stress is key in the pathogenesis of several diseases including age-related macular degeneration (AMD), atherosclerosis, diabetes, and Alzheimer's disease. It has previously been established that a lipid peroxidation product, carboxyethylpyrrole (CEP), accumulates in the retinas of AMD patients. Retinal infiltrating macrophages also accumulate in the retinas of both AMD patients and in a murine model of AMD. We therefore investigated the ability of CEP-adducts to activate innate immune signaling in murine bone-marrow derived macrophages (BMDMs). We found that CEP specifically synergizes with low-dose TLR2-agonists (but not agonists for other TLRs) to induce production of inflammatory cytokines. Moreover, CEP selectively augments TLR2/TLR1-signaling instead of TLR2/TLR6-signaling. These studies uncover a novel synergistic inflammatory relationship between an endogenously produced oxidation molecule and a pathogen-derived product, which may have implications in the AMD disease process and other oxidative stress-driven pathologies.

Serological association of Chlamydia pneumoniae infection with age-related macular degeneration: a systematic review and meta-analysis

Background

We investigated the serological association of Chlamydia pneumoniae infection with age-related macular degeneration (AMD).

Methods

A systematic review and meta-analysis was performed. PubMed, Embase, Web of Science and the Association of Research in Vision and Ophthalmology abstracts were searched to identify studies investigating the serological association of Chlamydia pneumoniae infection with age-related macular degeneration. The quality of original studies was assessed using the Newcastle-Ottawa scale. Heterogeneity was explored with meta-regression. The odds ratios (ORs) and standardized mean differences (SMD) of Chlamydia pneumoniae infection between AMD patients and controls were pooled.

Results

In total, 9 studies met the inclusion criteria using the Newcastle-Ottawa scale scores ranging from 4 to 9. There was heterogeneity among studies due to a difference in the study designs and measurement of exposure to Chlamydia pneumoniae infection. The overall OR of Chlamydia pneumoniae infection with AMD was 1.11 (95% confidence interval: 0.78–1.57, P = 0.56). The overall SMD of antibody titer between AMD and control was 0.43 (95% confidence interval: −0.12 to 0.99, P = 0.13).

Conclusions

Evidence from the current published literature suggested no statistically significant association between Chlamydia pneumoniae infection and AMD.

The Immune System and AMD

Age related macular degeneration (AMD) is a complex, multifactorial disease that has yet to be completely understood. Significant efforts in the basic and clinical sciences have unveiled numerous areas which appear to be critical in the pathogenesis of this disease. The alternative complement pathway, immune cell activation, and autoimmunity are all emerging as important themes to the suspected immunologic origins of this disease. Advancement toward a complete understanding of these processes is important in development of new techniques for disease monitoring and treatment.

Activation of Rap1 inhibits NADPH oxidase-dependent ROS generation in retinal pigment epithelium and reduces choroidal neovascularization

Activation of Rap1 GTPase can improve the integrity of the barrier of the retina pigment epithelium (RPE) and reduce choroidal neovascularization (CNV). Inhibition of NADPH oxidase activation also reduces CNV. We hypothesize that Rap1 inhibits NADPH oxidase-generated ROS and thereby reduces CNV formation. Using a murine model of laser-induced CNV, we determined that reduced Rap1 activity in RPE/choroid occurred with CNV formation and that activation of Rap1 by 2'-O-Me-cAMP (8CPT)-reduced laser-induced CNV via inhibiting NADPH oxidase-generated ROS. In RPE, inhibition of Rap1 by Rap1 GTPase-activating protein (Rap1GAP) increased ROS generation, whereas activation of Rap1 by 8CPT reduced ROS by interfering with the assembly of NADPH oxidase membrane subunit p22phox with NOX4 or cytoplasmic subunit p47phox. Activation of NADPH oxidase with Rap1GAP reduced RPE barrier integrity via cadherin phosphorylation and facilitated choroidal EC migration across the RPE monolayer. Rap1GAP-induced ROS generation was inhibited by active Rap1a, but not Rap1b, and activation of Rap1a by 8CPT in Rap1b(-/-) mice reduced laser-induced CNV, in correlation with decreased ROS generation in RPE/choroid. These findings provide evidence that active Rap1 reduces CNV by interfering with the assembly of NADPH oxidase subunits and increasing the integrity of the RPE barrier.

Low-dose lipopolysaccharide pretreatment suppresses choroidal neovascularization via IL-10 induction

Recent studies have suggested that some kinds of microbial infection may have a crucial role in the development of many diseases such as autoimmune diseases and certain types of cancer. It has been reported that some chronic infections, such as Chlamydia pneumoniae, and immunological dysfunctions are associated with age-related macular degeneration (AMD), a leading cause of blindness. To evaluate the association between systemic low-level inflammation induced by infection and AMD pathogenesis, we investigated whether intraperitoneal injection of lipopolysaccharide (LPS) can modulate the development of laser-induced choroidal neovascularization (CNV), a key feature of AMD. Contrary to our expectations, the sizes of CNV in mice with LPS pretreatment were approximately 65% smaller than those of the control mice. After LPS pretreatment, serum IL-10 concentration and IL-10 gene expression in peritoneal macrophages and in the posterior part of the eye increased. Peritoneal injection of anti-IL10 antibody reduced CNV suppression by LPS pretreatment. Moreover, adoptive transfer of the resident peritoneal macrophages from LPS-treated mice into control littermates resulted in an approximately 26% reduction in the size of CNV compared with PBS-treated mice. We concluded that CNV formation was suppressed by low-dose LPS pretreatment via IL-10 production by macrophages.

Macrophage activation associated with chronic murine cytomegalovirus infection results in more severe experimental choroidal neovascularization

The neovascular (wet) form of age-related macular degeneration (AMD) leads to vision loss due to choroidal neovascularization (CNV). Since macrophages are important in CNV development, and cytomegalovirus (CMV)-specific IgG serum titers in patients with wet AMD are elevated, we hypothesized that chronic CMV infection contributes to wet AMD, possibly by pro-angiogenic macrophage activation. This hypothesis was tested using an established mouse model of experimental CNV. At 6 days, 6 weeks, or 12 weeks after infection with murine CMV (MCMV), laser-induced CNV was performed, and CNV severity was determined 4 weeks later by analysis of choroidal flatmounts. Although all MCMV-infected mice exhibited more severe CNV when compared with control mice, the most severe CNV developed in mice with chronic infection, a time when MCMV-specific gene sequences could not be detected within choroidal tissues. Splenic macrophages collected from mice with chronic MCMV infection, however, expressed significantly greater levels of TNF-α, COX-2, MMP-9, and, most significantly, VEGF transcripts by quantitative RT-PCR assay when compared to splenic macrophages from control mice. Direct MCMV infection of monolayers of IC-21 mouse macrophages confirmed significant stimulation of VEGF mRNA and VEGF protein as determined by quantitative RT-PCR assay, ELISA, and immunostaining. Stimulation of VEGF production in vivo and in vitro was sensitive to the antiviral ganciclovir. These studies suggest that chronic CMV infection may serve as a heretofore unrecognized risk factor in the pathogenesis of wet AMD. One mechanism by which chronic CMV infection might promote increased CNV severity is via stimulation of macrophages to make pro-angiogenic factors (VEGF), an outcome that requires active virus replication.

Complement factor H 402H variant and reticular macular disease

OBJECTIVE

To determine the association of high-risk alleles in the complement factor H (CFH; Y402H, rs1061170) and age-related maculopathy susceptibility (ARMS2; A69S, rs10490924) genes with reticular macular disease (RMD), a major clinical subphenotype of age-related macular degeneration (AMD).

METHODS

Using retinal images from the Columbia Macular Genetics Study, we identified 67 subject individuals with RMD. A comparison group of 64 subjects with AMD without RMD was matched by ethnicity, age, sex, and AMD clinical stage.

RESULTS

In the RMD group, 53 of 67 subjects (79.1%) were female, the mean age was 83 years, and 47 of 67 (70.1%) had late AMD, with closely matched values in the non-RMD group. The frequencies of the CFH 402H allele were 39.6% in the RMD group (53 of 134 individuals) and 58.6% in the non-RMD group (75 of 128 individuals) (χ(2) = 8.8; P = .003; odds ratio, 0.46 [95% confidence interval, 0.28-0.76]). The corresponding frequencies of the risk allele for ARMS2 were 44.0% (40 of 128 individuals) and 31.3% (40 of 128 individuals), respectively (χ(2) = 4.0; P = .045; odds ratio, 1.73 [95% confidence interval, 1.04-2.90]). Homozygosity for 402H was particularly associated with the absence of RMD, occurring in 8 of 67 subjects (11.9%) with RMD vs 24 of 64 subjects (37.5%) without RMD (P < .001). Retinal macular disease also was associated with hypertension among male patients.

CONCLUSIONS

The AMD-associated CFH 402H risk variant is significantly associated with the absence of RMD but enhanced risk for RMD is conferred by the ARMS2 69S AMD risk allele. These results are consistent with the hypothesis that 402H may confer a survival benefit against certain infections, some of which may cause RMD.

CLINICAL RELEVANCE

Reticular macular disease may be genetically distinct from the rest of AMD.

Statin use and the risk of age related macular degeneration in a large health organization in Israel

OBJECTIVE

To investigate the association between persistent use of statins and the risk of age-related macular degeneration (AMD).

DESIGN

A population-based retrospective cohort among adults who began statin therapy between 1998 and 2006 in a large health organization in Israel. The organization's central computerized databases were used to collect data on incident AMD cases diagnosed by ophthalmologists.

RESULTS

A total of 108,973 individuals aged 55 or older were identified. During the study follow-up period 409,113 person-years, there were 2,732 incident AMD cases (6.68 per 1,000 person-years). The crude incidence density rate of AMD among patients at the lowest quintile of persistence with statins (7.18 per 1,000) was comparable to that of highest persistence quintile (7.13 per 1,000). After adjustment for potential confounders, patients in the highest quintile of persistence with statins had a hazard ratio of 0.99 (95% Confidence Interval: 0.78-1.26) for AMD compared with patients in the lowest proportion of days covered (PDC) quintile. In addition to age, AMD was found to associate with past smoking, asthma, diabetes and frequent visits to ophthalmologists or primary physicians prior to index date.

CONCLUSIONS

Our study agrees with previous studies that showed no association between persistent use of statins and reduced risk of AMD. These results suggest that the early reports on a strong protective effect of statins against AMD development were probably a result of a small study effect.

Elevated serum immunoglobulin G titers against Chlamydia pneumoniae in primary open-angle glaucoma patients without systemic disease

PURPOSE

To determine if Chlamydia pneumoniae infection is associated with primary open-angle glaucoma (POAG).

PATIENTS AND METHODS

Consecutive patients with newly diagnosed primary POAG attending the Glaucoma clinic of Keio University Hospital between June 2007 and January 2008 were considered for inclusion in this prospective case-control study. Forty consecutive POAG patients and 41 normal healthy individuals as a control population met the inclusion criteria. The exclusion criteria for both groups were; taking steroids or immunosuppressive agents, smoking, and history of any acute or chronic systemic disease including stroke, heart attack, diabetes mellitus, hypertension, asthma, and autoimmune diseases. The serum was analyzed for C. pneumoniae and C. trachomatis immunoglobulin G antibody titers by enzyme-linked immunosorbent assay. Seroactivity to each antigen between case and control groups was evaluated by Mann-Whitney U test.

RESULTS

The age, male/female ratio, and intraocular pressure of the cases and control groups were not significantly different. Immunoglobulin G titers for C. pneuemoniae was significantly higher in patients with POAG than in controls (P=0.009). The titers to C. trachomatis were not significantly different between the 2 groups (P=0.99).

CONCLUSION

The results suggest that higher C. pneumoniae titers are associated with POAG. If confirmed, this may indicate either a common factor that causes susceptibilities to both glaucoma and C. pneumoniae infection or that C. pneumoniae may be a causal factor for developing POAG.

Mycoplasma pneumoniae and Chlamydia pneumoniae seropositivity in patients with age-related macular degeneration

Background

To determine a possible relation between Mycoplasma pneumoniae (MP) or Chlamidia pneumoniae (CP) seropositivity and age-related macular degeneration (AMD).

Methods

Sixty patients (20 wet AMD, 20 dry AMD and 20 non-AMD controls) were included in the study. Serum samples were collected for analysis of IgM and IgG antibody seropositivity for CP and MP by enzyme-linked immunosorbent assay (ELISA). Comparison of the distribution of seropositivity of these antibodies among patients with wet and dry AMD, and controls was performed. A prospective comparative clinical trial was applied.

Results

There was no major difference in the distribution of IgM and IgG seropositivity to CP and MP in patients with wet and dry AMD, and in controls (p > 0.05).

Conclusions

We found no significant association between MP as well as CP antibody titers and AMD. It seems that MP or CP infection is not a risk factor for AMD.

Keywords

Mycoplasma pneumoniae; Chlamydia pneumoniae; Age-related macular degeneration; Serology

Endoplasmic reticulum stress as a primary pathogenic mechanism leading to age-related macular degeneration

Age-related macular degeneration (AMD) is a multi-factorial disease and a leading cause of blindness. Proteomic and genetic data suggest that activation or de-repression of the alternate complement cascade of innate immunity is involved in end-stage disease. Several lines of evidence suggest that production of reactive oxygen species and chronic oxidative stress lead to protein and lipid modifications that initiate the complement cascade. Understanding the triggers of these pathogenic pathways and the site of the primary insult will be important for development of targeted therapeutics. Endoplasmic reticulum (ER) stress from misfolded mutant proteins and other sources are an important potential tributary mechanism. We propose that misfolded-protein-induced ER stress in the retinal-pigmented epithelium and/or choroid could lead to chronic oxidative stress, complement deregulation and AMD. Small molecules targeted to ER stress and oxidative stress could allow for a shift from disease treatment to disease prevention.

Complement factor H gene polymorphisms and Chlamydia pneumoniae infection in age-related macular degeneration

PURPOSE

To investigate the association of the complement factor H gene (CFH)Y402H polymorphism and age-related macular degeneration (AMD) in the Austrian population (Caucasoid descent), and to determine whether there is an association between exposure to Chlamydia pneumoniae-responsible for up to 20% of community-acquired pneumoniae-and the AMD-associated CFHrisk polymorphism.

METHODS

Genotypes were determined by polymerase chain reaction-restriction fragment length polymorphism analysis in 75 unrelated AMD patients and compared with 75 healthy, age-matched control subjects. C. pneumoniaeserum IgG was tested by ELISA (R&D) in both groups. The association between the CFHY402H genetic polymorphism and the disease was examined by chi (2)-test and logistic regression.

RESULTS

CFH Y402H genotypefrequencies differed significantly between AMD patients and healthy controls (1277 TT, 22.7%; 1277 TC, 53.3%; and 1277 CC, 22.7% in the AMD group; 1277 TT, 48.0%; 1277 TC, 38.7%; and 1277 CC, 13.3% in the control group) showing a P-value <0.005 (OR:2.920/3.811).No association was found between a positive C. pneumoniae titre and AMD (P=0.192), nor was any association found between C. pneumoniae and the CFH Y402H polymorphism.

CONCLUSIONS

Our data confirm that the CFHY402H polymorphism is a risk factor for AMD in the Austrian population with a higher frequency of the Y402 polymorphism in AMD patients. No association between preceding C. pneumoniaeinfection and diagnosed AMD was found.

Autoimmunity in retinal degeneration: autoimmune retinopathy and age-related macular degeneration

Autoantibody production is associated with a variety of ocular disorders, including autoimmune retinopathy (AIR) and age-related macular degeneration (AMD). A breakdown of immunologic tolerance (ocular immune privilege), including the blood-retinal barrier, anti-immune and anti-inflammatory proteins, and anterior chamber-associated immune deviation may play important roles in these disorders. Although the exact triggers for ocular autoimmunity are unknown, autoimmune targeting of retinal tissue is clearly associated with and may contribute to the pathogenesis of both AIR and AMD. Autoantibody production has long been associated with AIR, a collection of disorders that includes cancer-associated retinopathy, melanoma-associated retinopathy and non-paraneoplastic autoimmune retinopathy. A growing body of evidence indicates that AMD pathogenesis, too, involves ocular inflammation and autoimmunity. Identification and quantification of autoantibodies produced in patients with AIR and AMD may assist with diagnosis, prognosis, and choice of treatments. Animal models that allow investigation of ocular autoimmunity will also be needed to better understand the disease processes and to develop novel therapies. In this review we discuss ocular immune privilege and potential mechanisms of autoimmunity in the eye. We describe how autoimmunity relates to the pathogenesis of AIR and AMD. We explain how the antigen microarray technique is used to detect autoantibodies in patient serum samples, and discuss how current animal models for AMD can be used to investigate autoimmune pathogenesis. Finally, we outline unanswered questions and exciting areas of future study related to autoimmune retinal degeneration.

Proteasome inactivation promotes p38 mitogen-activated protein kinase-dependent phosphatidylinositol 3-kinase activation and increases interleukin-8 production in retinal pigment epithelial cells

Oxidative stress and inflammation are implicated in the pathogenesis of many age-related diseases. We have demonstrated previously that oxidative inactivation of the proteasome is a molecular link between oxidative stress and overexpression of interleukin (IL)-8. Here, we elucidated a novel signaling cascade that leads to up-regulation of IL-8 in response to proteasome inactivation. The sequence of events in this cascade includes proteasome inactivation, activation of mitogen-activated protein kinase kinase (MKK)3/MKK6, activation of p38 mitogen-activated protein kinase (MAPK), epidermal growth factor receptor phosphorylation, phosphatidylinositol 3-kinase (PI3K) activation and increased IL-8 expression. Blocking any of these signaling pathways abolished the up-regulation of IL-8 induced by proteasome inhibition. Although Akt is also activated in response to proteasome inactivation, we found that the PI3K-dependent up-regulation of IL-8 is independent of 3-phosphoinositide-dependent protein kinase (PDK)1 and Akt. Inhibition of PDK1 and Akt with chemical inhibitors or expression of constitutive active Akt had little effects on IL-8 expression in response to proteasome inactivation. In contrast, inhibition of interleukin 2-inducible T cell kinase, a kinase downstream of PI3K, significantly reduced the expression and secretion of IL-8 in response to proteasome inactivation. Together, these data elucidate a novel signaling network that leads to increased IL-8 production in response to proteasome inactivation.

Progress and perspectives on the role of RPE cell inflammatory responses in the development of age-related macular degeneration

Age-related macular degeneration (AMD) is the leading cause of blindness in developed countries. The etiology of AMD remains poorly understood and no treatment is currently available for the atrophic form of AMD. Atrophic AMD has been proposed to involve abnormalities of the retinal pigment epithelium (RPE), which lies beneath the photoreceptor cells and normally provides critical metabolic support to these light-sensing cells. Cumulative oxidative stress and local inflammation are thought to represent pathological processes involved in the etiology of atrophic AMD. Studies of tissue culture and animal models reveal that oxidative stress-induced injury to the RPE results in a chronic inflammatory response, drusen formation, and RPE atrophy. RPE degeneration in turn causes a progressive degeneration of photoreceptors, leading to the irreversible loss of vision. This review describes some of the potential major molecular and cellular events contributing to RPE death and inflammatory responses. In addition, potential target areas for therapeutic intervention will be discussed and new experimental therapeutic strategies for atrophic AMD will be presented.

Chlamydia pneumoniae infection, complement factor H variants and age-related macular degeneration

BACKGROUND/AIMS

Impaired inhibition of the alternative complement pathway by complement factor H (CFH) is linked to age-related macular degeneration (AMD) based on the strong association between CFH variant and AMD. Chlamydia pneumoniae (C pneumoniae) infection can trigger the alternative pathway, but the evidence for an association between C pneumoniae and AMD is contradictory. This study investigated whether C pneumoniae infection is associated with AMD and whether the presence of C pneumonia modulates AMD risk conferred by CFH variants.

METHODS

Genomic DNA extracted from peripheral blood of 148 advanced AMD patients and 162 controls was subjected to Taqman and PCR-RFLP for the CFH polymorphism and PCR for the C pneumoniae gene. Genomic DNA was also examined from microdissected macular cells from 59 AMD and 16 age-matched non-AMD archived slides. chi(2) testing was performed for case-control analysis.

RESULTS

C pneumoniae infection was associated with increased risk of AMD (OR = 2.17, p<0.017). A CFH variant was also linked to increased risk of AMD (OR = 1.98, p<0.0001). However, no relationship was found between risk-conferring CFH variant and C pneumoniae (OR = 1.81, p = 0.08).

CONCLUSION

There is a possible association between AMD and C pneumoniae infection, although CFH may not be directly involved in the pathogenesis of C pneumoniae infection-mediated AMD.

Molecular pathology of age-related macular degeneration

Age-related macular degeneration (AMD) is a leading cause of irreversible blindness in the world. Although the etiology and pathogenesis of AMD remain largely unclear, a complex interaction of genetic and environmental factors is thought to exist. AMD pathology is characterized by degeneration involving the retinal photoreceptors, retinal pigment epithelium, and Bruch's membrane, as well as, in some cases, alterations in choroidal capillaries. Recent research on the genetic and molecular underpinnings of AMD brings to light several basic molecular pathways and pathophysiological processes that might mediate AMD risk, progression, and/or response to therapy. This review summarizes, in detail, the molecular pathological findings in both humans and animal models, including genetic variations in CFH, CX3CR1, and ARMS2/HtrA1, as well as the role of numerous molecules implicated in inflammation, apoptosis, cholesterol trafficking, angiogenesis, and oxidative stress.

Pegaptanib combined with intravitreal injection of moxifloxacin as treatment of wet macular degeneration

PURPOSE

To evaluate the effectiveness of pegaptanib combined with intravitreal injection of moxifloxacin as treatment of wet macular degeneration.

METHODS

This retrospective review included patients who received pegaptanib combined with 165 microg of moxifloxacin every 6 weeks. Ophthalmic examination was performed, and adverse events were recorded at each visit; additional assessments (e.g., optical coherence tomography) were performed when indicated.

RESULTS

Eighty eyes of 65 patients were identified; the median length of follow-up was 13.2 months (range, 10-16 months), and eyes received an average of 6 injections (range, 4-9 months). Seventy eyes of 80 patients have been followed for >or=1 year; 80% (65/70) had stable or improved vision, and 97% (68/70) lost <15 letters of vision.

CONCLUSION

Pegaptanib combined with intravitreal injection of moxifloxacin appears to be effective treatment of wet macular degeneration.

Oxidative inactivation of the proteasome in retinal pigment epithelial cells. A potential link between oxidative stress and up-regulation of interleukin-8

Oxidative stress and inflammation are implicated in the pathogenesis of many age-related diseases. Stress-induced overproduction of inflammatory cytokines, such as interleukin-8 (IL-8), is one of the early events of inflammation. The objective of this study was to elucidate mechanistic links between oxidative stress and overproduction of IL-8 in retinal pigment epithelial (RPE) cells. We found that exposure of RPE cells to H(2)O(2), paraquat, or A2E-mediated photooxidation resulted in increased expression and secretion of IL-8. All of these oxidative stressors also inactivated the proteasome in RPE cells. In contrast, tert-butylhydroperoxide (TBH), a lipophilic oxidant that did not stimulate IL-8 production, also did not inactivate the proteasome. Moreover, prolonged treatment of RPE cells with proteasome-specific inhibitors recapitulated the stimulation of IL-8 production. These data suggest that oxidative inactivation of the proteasome is a potential mechanistic link between oxidative stress and up-regulation of the proinflammatory IL-8. The downstream signaling pathways that govern the production of IL-8 include NF-kappaB and p38 MAPK. Proteasome inhibition both attenuated the activation and delayed the turnoff of NF-kappaB, resulting in biphasic effects on the production of IL-8. Prolonged proteasome inhibition (>2 h) resulted in activation of p38 MAPK via activation of MKK3/6 and increased the production of IL-8. Chemically inhibiting the p38 MAPK blocked the proteasome inhibition-induced up-regulation of IL-8. Together, these data indicate that oxidative inactivation of the proteasome and the related activation of the p38 MAPK pathway provide a potential link between oxidative stress and overproduction of proinflammatory cytokines, such as IL-8.

Vascular endothelial growth factor in eye disease

Collectively, angiogenic ocular conditions represent the leading cause of irreversible vision loss in developed countries. In the US, for example, retinopathy of prematurity, diabetic retinopathy and age-related macular degeneration are the principal causes of blindness in the infant, working age and elderly populations, respectively. Evidence suggests that vascular endothelial growth factor (VEGF), a 40kDa dimeric glycoprotein, promotes angiogenesis in each of these conditions, making it a highly significant therapeutic target. However, VEGF is pleiotropic, affecting a broad spectrum of endothelial, neuronal and glial behaviors, and confounding the validity of anti-VEGF strategies, particularly under chronic disease conditions. In fact, among other functions VEGF can influence cell proliferation, cell migration, proteolysis, cell survival and vessel permeability in a wide variety of biological contexts. This article will describe the roles played by VEGF in the pathogenesis of retinopathy of prematurity, diabetic retinopathy and age-related macular degeneration. The potential disadvantages of inhibiting VEGF will be discussed, as will the rationales for targeting other VEGF-related modulators of angiogenesis.

Immunopathological aspects of age-related macular degeneration

Age-related macular degeneration (AMD) represents a leading cause of blindness worldwide. While the clinical and histopathological aspects of AMD are well characterized, its etiology and pathogenesis remain unclear. Recent findings suggest a role for immunologic processes in AMD pathogenesis, including the age-related generation of extracellular deposits inside the Brusch membrane and beneath the retinal pigment epithelium, recruitment of macrophages for clearance of these deposits, complement activation, recruitment of tissue-destructive macrophages, microglial activation and accumulation, and proinflammatory effects of chronic inflammation by Chlamydia pneumoniae. This review discusses the evidence for the role of inflammation in human AMD and in animal models of AMD.

Role of genetic factors and inflammation in age-related macular degeneration

Complement factor H (CFH) has been implicated in the predisposition to advanced forms of age-related macular degeneration (AMD). The purpose of this review is to highlight recent discoveries implicating single nucleotide polymorphisms on 1q32, 6p21, and 10q26 in the risk for development of AMD. In addition, the central role of CFH in the complement cascade and its role in the inflammatory hypothesis for AMD are reviewed.

Triple therapy for choroidal neovascularization due to age-related macular degeneration: verteporfin PDT, bevacizumab, and dexamethasone

PURPOSE

To evaluate the efficacy and safety of triple therapy with verteporfin photodynamic therapy (PDT), dexamethasone, and bevacizumab in choroidal neovascularization (CNV) secondary to age-related macular degeneration (AMD).

METHODS

This prospective, noncomparative, interventional case series included 104 patients. Verteporfin PDT was administered with a reduced light dose (42 J/cm, accomplished by light delivery time of 70 seconds). Approximately 16 hours after PDT, dexamethasone (800 microg) and bevacizumab (1.5 mg) were injected intravitreally. Patients attended follow-up visits every 6 weeks, undergoing visual acuity and intraocular pressure measurement, slit-lamp and ophthalmoscopic examination, and optical coherence tomography (OCT). Fluorescein angiography was performed every 3 months or earlier if OCT showed significant edema.

RESULTS

All 104 patients received one triple therapy cycle (5 patients received a second triple treatment due to remaining CNV activity). The triple therapy was complemented in 18 patients (17.3%) by an additional intravitreal injection of bevacizumab. The mean follow-up period was 40 weeks (range, 22-60 weeks). Mean increase in visual acuity was 1.8 lines (P < 0.01). Mean decrease in retinal thickness was 182 microm (P < 0.01). No serious adverse events have been observed.

CONCLUSION

In most patients with CNV due to AMD, triple therapy results in significant and sustained visual acuity improvement after only one cycle of treatment. In addition, the therapy offers a good safety profile, potentially lower cost compared with therapies that must be administered more frequently, and convenience for patients.

Chlamydia pneumoniae and age-related macular degeneration: a role in pathogenesis or merely a chance association?

The role of inflammation in the aetiology of age-related macular degeneration (AMD) has become very topical as the discovery that genetic variation in complement pathway genes influences the risk of developing AMD. Complement factor H gene, an inhibitor of the alternative complement activation pathway along with other complement pathway genes factor F (BF) and C2 show significant contribution to the risk of AMD. The alternative complement pathway is activated by a trigger, which is often microbial in nature. One current model of AMD aetiology implicates aberrant regulation of the alternative pathway of complement, in combination with some unknown infectious agents. Chlamydia pneumoniae could be one such potential trigger of the alternative complement pathway and several investigations have linked C. pneumoniae to AMD. However, there are only a few studies to date and numbers in most studies are small. Also there are many difficulties in verifying laboratory techniques for the detection of C. pneumoniae chronic infection. As such we need to be cautious not to over interpret the current results. However, the findings certainly give impetus for further work on C. pneumoniae and AMD. This paper provides an overview of work in this area.

Emerging drugs for age-related macular degeneration

Age-related macular degeneration (AMD) is a leading cause of blindness that until recently had no recognised drug treatment. In wet AMD, choroidal neovascularisation (CNV) causes a profound loss of central vision. CNV is a complex process in which tissue ischaemia and/or inflammation is thought to trigger production of angiogenic signal molecules. The release of VEGF appears to be particularly important. Verteporfin photodynamic therapy was the first drug therapy to be licensed for the treatment of some types of wet AMD. Other treatments directly targeting VEGF or other aspects of angiogenesis, such as pegaptanib, ranibizumab and anecortave acetate, have either recently been licensed or are in the advanced stages of development. These and other promising treatment options such as combination strategies are reviewed.

Chlamydienerkrankungen des Auges – eine kurze Übersicht

In this short review, new data on the taxonomy of Chlamydia and the association of these pathogens with various ocular diseases are presented. Clinical diagnosis and laboratory tests for ocular C. trachomatis infection are discussed. The actual therapy consists in oral azithromycin.

Macular degeneration: recent advances and therapeutic opportunities

The central retina mediates high acuity vision, and its progressive dysfunction due to macular degeneration is the leading cause of visual disability among adults in industrialized societies. Here, we summarize recent progress in understanding the pathophysiology of macular degeneration and the implications of this new knowledge for treatment and prevention. The past decade has witnessed remarkable advances in this field, including the development of new, non-invasive retinal imaging technologies, the development of animal models for macular disease, and the isolation of many of the genes responsible for both early- and late-onset macular diseases. These advances have set the stage for the development of effective mechanism-based therapies.

Detection by broad-range real-time PCR assay of Chlamydia species infecting human and animals

BACKGROUND

Tests available for molecular diagnosis of chlamydial infections detect Chlamydiatrachomatis, but do not find other Chlamydia species associated with genital, ophthalmic, cardiovascular, respiratory or neurological diseases. The routine detection of all Chlamydia species would improve the prognosis of infected people and guide therapeutic choices.

AIM

To design and validate a sensitive, specific, reproducible, inexpensive and easy-to-perform assay to quantify most Chlamydia species.

METHODS

Primers and probe were selected using the gene coding for the 16S rRNA. The detection limits were assessed for suspensions of Chlamydia trachomatis, Chlamydia psittaci and Chlamydia pneumoniae. The performance of this test was compared with that of two commercial kits (Amplicor-Roche and Artus) on 100 samples obtained from children with trachoma.

RESULTS

The detection capacities for Chlamydia trachomatis of the broad-range real-time polymerase chain reaction (PCR) were similar or slightly better than those obtained with commercial kits (0.2 copies of DNA/microl). Only the broad-range PCR identified specimens containing Chlamydia psittaci and Chlamydia pneumoniae. The commercial kits and the broad-range assay detected Chlamydia species in 5% and in 11%, respectively, of samples from children with trachoma.

CONCLUSIONS

This new real-time PCR offers a sensitive, reproducible assay that produces results in <3 h. With panels of quantified Chlamydia species, this real-time PCR can be run with all real-time PCR equipment. Larger trials are needed to confirm the utility of this test in diagnosis and for therapeutic follow-up.