A metagenome-wide association study of gut microbiome in patients with AMD, ASD, RA, T2D & VKH diseases.

Clinical studies have already illustrated the associations between gut microbes and diseases, yet fundamental questions remain unclear that how we can universalize this knowledge. Considering the important role of human gut microbial composition in maintaining overall health, it is important to understand the microbial diversity and altered disease conditions of the human gut. Metagenomics provides a way to analyze and understand the microbes and their role in a community manner. It provides qualitative as well as quantitative measurements, in terms of relative abundance. Various studies are already going on to find out the association between microbes and diseases; still, the mined knowledge is limited. Considering the current scenario, using the targeted metagenomics approach, we analyzed the gut microbiome of 99 samples from healthy and diseased individuals. Our metagenomic analysis mainly targeted five diseased microbiomes (i.e., Age-related macular degeneration, Autism spectrum disorder, Rheumatoid arthritis, Type 2 diabetes and Vogt-Koyanagi harada), with compare to healthy microbiome, and reported disease-associated microbiome shift in different conditions.

High-Fat Diet Alters the Retinal Transcriptome in the Absence of Gut Microbiota.

The relationship between retinal disease, diet, and the gut microbiome has shown increasing importance over recent years. In particular, high-fat diets (HFDs) are associated with development and progression of several retinal diseases, including age-related macular degeneration (AMD) and diabetic retinopathy. However, the complex, overlapping interactions between diet, gut microbiome, and retinal homeostasis are poorly understood. Using high-throughput RNA-sequencing (RNA-seq) of whole retinas, we compare the retinal transcriptome from germ-free (GF) mice on a regular diet (ND) and HFD to investigate transcriptomic changes without influence of gut microbiome. After correction of raw data, 53 differentially expressed genes (DEGs) were identified, of which 19 were upregulated and 34 were downregulated in GF-HFD mice. Key genes involved in retinal inflammation, angiogenesis, and RPE function were identified. Enrichment analysis revealed that the top 3 biological processes affected were regulation of blood vessel diameter, inflammatory response, and negative regulation of endopeptidase. Molecular functions altered include endopeptidase inhibitor activity, protease binding, and cysteine-type endopeptidase inhibitor activity. Human and mouse pathway analysis revealed that the complement and coagulation cascades are significantly affected by HFD. This study demonstrates novel data that diet can directly modulate the retinal transcriptome independently of the gut microbiome.

Local oral and nasal microbiome diversity in age-related macular degeneration.

Age-related macular degeneration (AMD) is a chronic degenerative disease of the retina. Recent reports have highlighted the potential role of mucosal surface microbes in the pathogenesis of AMD. In this case-control study, the composition of the nasal and oral microbiota in newly diagnosed neovascular age-related macular degeneration cases (6 male, 7 female) was compared to controls without retinal diseases (2 male, 3 female). PCR amplification of 16S rRNA genes was performed with universal primers amplifying the V4 variable region (515F-806R). Distinct microbial community characterization was achieved using Principal Coordinates Analysis (PCoA) of the Bray-Curtis index with comparative analysis between cases and controls performed within QIIME 2. Sequencing of all cases and controls revealed clear separation with strong beta diversity between oral and nasal microbial communities (p < 0.001). Microbial composition differed between cases and controls in both oral and nasal samples. The top three oral microbes identified as different compared to controls included Burkholderiales (7.41 log2fold change, p = 3.29E-05), Actinomyceataceae (6.22 log2fold change, p = 3.73E-06) and Gemella (5.28 log2fold change, p = 0.0002). The top three nasal microbes identified as different compared to controls included Rothia (13.6 log2fold change, p = 3.63E-18), Actinobacteria (10.29 log2fold change, p = 9.81E-10) and Propionibacteriales (8.73 log2fold change, p = 6.74E-09). These relative shifts in communities of bacteria detected in newly diagnosed neovascular AMD patients may suggest additional mechanistic links in disease pathogenesis.

Human pharyngeal microbiota in age-related macular degeneration.

BACKGROUND: While the aetiology of age-related macular degeneration (AMD)-a major blinding disease-remains unknown, the disease is strongly associated with variants in the complement factor H (CFH) gene. CFH variants also confer susceptibility to invasive infection with several bacterial colonizers of the nasopharyngeal mucosa. This shared susceptibility locus implicates complement deregulation as a common disease mechanism, and suggests the possibility that microbial interactions with host complement may trigger AMD. In this study, we address this possibility by testing the hypothesis that AMD is associated with specific microbial colonization of the human nasopharynx. RESULTS: High-throughput Illumina sequencing of the V3-V6 region of the microbial 16S ribosomal RNA gene was used to comprehensively and accurately describe the human pharyngeal microbiome, at genus level, in 245 AMD patients and 386 controls. Based on mean and differential microbial abundance analyses, we determined an overview of the pharyngeal microbiota, as well as candidate genera (Prevotella and Gemella) suggesting an association towards AMD health and disease conditions. CONCLUSIONS: Utilizing an extensive study population from Singapore, our results provided an accurate description of the pharyngeal microbiota profiles in AMD health and disease conditions. Through identification of candidate genera that are different between conditions, we provide preliminary evidence for the existence of microbial triggers for AMD. Ethical approval for this study was obtained through the Singapore Health Clinical Institutional Review Board, reference numbers R799/63/2010 and 2010/585/A.

The Role of Microbiota in Retinal Disease.

The ten years since the first publications on the human microbiome project have brought enormous attention and insight into the role of the human microbiome in health and disease. Connections between populations of microbiota and ocular disease are now being established, and increased accessibility to microbiome research and insights into other diseases is expected to yield enormous information in the coming years. With the characterization of the ocular microbiome, important insights have already been made regarding corneal and conjunctival tissues. Roles for non-ocular microbiomes in complex retinal diseases are now being evaluated. For example, the gut microbiome has been implicated in the pathogenesis of uveitis. This short review will summarize the few studies linking gut or oral microbiota to diabetic retinopathy (DR), glaucoma, and age-related macular degeneration (AMD). We will also conjecture where the most significant findings still remain to be elucidated. Finally, we will propose the gut-retina axis, related but distinct from the gut-brain axis.

Gut microbiota modify risk for dietary glycemia-induced age-related macular degeneration.

Age-related macular degeneration (AMD) is a leading cause of blindness world-wide. Although the etiology of AMD is multifactorial, diet and nutrition have strong epidemiologic associations with disease onset and progression. Recent studies indicate a role for gut microbiota in development of AMD in mouse models and in some forms of human AMD. We previously found that consuming lower glycemia diets is associated with protection against AMD in humans and switching from higher to lower glycemia diets arrests AMD phenotypes in mice. Gut microbiota populations and circulating microbial cometabolites were altered in response to dietary carbohydrates, indicating a gut-retina axis. Here we explore additional gut microbiota-AMD interactions that point toward pathogenic roles for some gut microbiota families, including Ruminococcaceae and Lachnospiraceae, and individual members of Turicibacteraceae, Clostridiaceae, and Mogibacteriaceae. We also speculate on potential mechanisms by which gut microbiota influence AMD, with the objective of devising new AMD diagnoses and treatments.

Association of the Intestinal Microbiome with the Development of Neovascular Age-Related Macular Degeneration.

Age-related macular degeneration (AMD) is the most frequent cause of blindness in the elderly. There is evidence that nutrition, inflammation and genetic risk factors play an important role in the development of AMD. Recent studies suggest that the composition of the intestinal microbiome is associated with metabolic diseases through modulation of inflammation and host metabolism. To investigate whether compositional and functional alterations of the intestinal microbiome are associated with AMD, we sequenced the gut metagenomes of patients with AMD and controls. The genera Anaerotruncus and Oscillibacter as well as Ruminococcus torques and Eubacterium ventriosum were relatively enriched in patients with AMD, whereas Bacteroides eggerthii was enriched in controls. Patient's intestinal microbiomes were enriched in genes of the L-alanine fermentation, glutamate degradation and arginine biosynthesis pathways and decreased in genes of the fatty acid elongation pathway. These findings suggest that modifications in the intestinal microbiome are associated with AMD, inferring that this common sight threatening disease may be targeted by microbiome-altering interventions.

Morphological features in eyes with endophthalmitis after cataract surgery - histopathology and optical coherence tomography assessment.

PURPOSE: To assess the ocular damage that occurs in eyes with postoperative endophthalmitis after cataract surgery (PE) based on optical coherence tomography (OCT) retinal scans of PE eyes and histological specimens of eyes removed due to PE. METHODS: Case-control study and case series. Fifty-one patients who had previously developed PE were clinically examined with OCT scans of the retina of both eyes. Histological specimens of 10 removed PE eyes were studied. RESULTS: The OCT scans showed that PE eyes had a statistically significantly higher frequency of hyperdense elements on the internal limiting membrane (ILM) of the retina (14 eyes versus 3 eyes, p = 0.015) and a higher degree of retinal atrophy temporal to the fovea (13 eyes versus 1 eye, p = 0.013) compared to fellow eyes. The histopathological analyses showed the formation of epiretinal membranes, derangement of all retinal layers with a reduced number of nuclei in the nuclear layers, loss of photoreceptor outer segments and massive retinal gliosis. CONCLUSIONS: Optical coherence tomography scans of the retina and histopathology analyses provide insights in the pathological process occurring in PE.

Gene expression regulation in retinal pigment epithelial cells induced by viral RNA and viral/bacterial DNA.

PURPOSE: The pathogenesis of age-related macular degeneration (AMD) is associated with systemic and local inflammation. Various studies suggested that viral or bacterial infection may aggravate retinal inflammation in the aged retina. We compared the effects of synthetic viral RNA (poly(I:C)) and viral/bacterial DNA (CpG-ODN) on the expression of genes known to be involved in the development of AMD in retinal pigment epithelial (RPE) cells. METHODS: Cultured human RPE cells were stimulated with poly(I:C; 500 µg/ml) or CpG-ODN (500 nM). Alterations in gene expression and protein secretion were determined with real-time RT-PCR and ELISA, respectively. Phosphorylation of signal transduction molecules was revealed by western blotting. RESULTS: Poly(I:C) induced gene expression of the pattern recognition receptor TLR3, transcription factors (HIF-1α, p65/NF-κB), the angiogenic factor bFGF, inflammatory factors (IL-1ß, IL-6, TNFα, MCP-1, MIP-2), and complement factors (C5, C9, CFB). Poly(I:C) also induced phosphorylation of ERK1/2 and p38 MAPK proteins, and the secretion of bFGF and TNFα from the cells. CpG-ODN induced moderate gene expression of transcription factors (p65/NF-κB, NFAT5) and complement factors (C5, C9), while it had no effect on the expression of various TLR, angiogenic factor, and inflammatory factor genes. The activities of various signal transduction pathways and transcription factors were differentially involved in mediating the poly(I:C)-induced transcriptional activation of distinct genes. CONCLUSIONS: The widespread effects of viral RNA, and the restricted effects of viral/bacterial DNA, on the gene expression pattern of RPE cells may suggest that viral RNA rather than viral/bacterial DNA induces physiologic alterations of RPE cells, which may aggravate inflammation in the aged retina. The data also suggest that selective inhibition of distinct signal transduction pathways or individual transcription factors may not be effective to inhibit viral retinal inflammation.

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.

Chlamydia infection status, genotype, and age-related macular degeneration.

PURPOSE: To evaluate whether Chlamydia (C.) infections are associated with age-related macular degeneration (AMD) and to assess if this association is influenced by the complement factor H (CFH) Y402H or the high temperature requirement A serine peptidase 1 (HTRA1) rs11200638 risk genotypes. METHODS: One hundred ninety-nine AMD patients with early and late forms of the disease and 100 unaffected controls, at least 50 years old were included in the study. Patients in the AMD and control groups were selected based on known CFH Y402H variant genotype status (one third homozygous CC, one third heterozygous CT, and one third wild-type TT). Plasma from all patients and controls was tested for C. pneumoniae, C. trachomatis, and C. psittaci IgG seropositivity using a micro-immunofluorescent assay to establish previous infection status. Assays were conducted blind to risk genotypes and the results analyzed using univariate and multivariate (logistic regression) analysis. RESULTS: IgG seropositivity to C. pneumoniae was most prevalent (69.2%, n=207), followed by C. trachomatis (7.4%, n=22) and C. psittaci (3.3%, n=10). No association was found between each of the three Chlamydia species IgG seropositivity and AMD status or severity (early/late). There was also no significant association between Chlamydia species IgG seropositivity and AMD status or severity, in patients carrying at least one CFH Y402H risk allele (C) or HTRA1 rs11200638 risk allele (A), with univariate or logistic regression analysis. CONCLUSIONS: Chlamydia infection status does not appear to be associated with AMD status or severity. The presence of CFH Y402H and HTRA1 rs11200638 risk genotypes does not alter this negative association.

[Preoperative conjunctival bacterial microbiota of antiangiogenic intravitreous injection for age-related macular degeneration compared to cataract surgery preoperative microbiota]. / Microbiota bacteriana da conjuntiva no pré-operatório de injeção intravítrea de antiangiogênico por degeneração macular relacionada à idade comparada com a de cirurgia de catarata.

PURPOSE: To evaluate the conjunctival bacterial microbiota and antibiogram profile in the preoperative of antiangiogenic intravitreous injection for age-related macular degeneration, and compare to the preoperative microbiota of patients submitted to cataract surgery. METHODS: Cross-sectional, observational, case series study. Two groups were organized: group I (macular degeneration) with 26 eyes from 26 patients (12 men/14 women) with mean age of 69.2 +/- 11.5 years; group II (cataract) with 27 eyes from 27 patients (9 men/18 women) with mean age of 67.6 +/- 7.9 years. The groups were similar regarding age (p=0.538) and gender (p=0.787). The lower conjunctival sac was swabbed and the obtained material was immediately put in a tube filled with liquid culture media BHI ("brain heart infusion"). Samples were processed according to standard laboratory techniques and antibiogram was determined for each bacterial colony. RESULTS: Twenty-six bacterial colonies growth in group I, with 2 eyes showing no growth and 30 colonies growth in group II. Gram positive bacteria were more prevalent in both groups: 23/26 colonies (88.4%) in group I and 29/30 colonies (96.7%) in group II, with a Staphylococcus aureus predominance in both groups, with 16 samples (61.5%) and 17 (56.7%), respectively. Coagulase negative Staphylococcus was the second most common identified bacteria, with 19.2% in group I and 20.0% in group II. No differences between the groups reached statistical significance. No statistically significant difference was noted on the antibiotic sensibility between both groups. CONCLUSIONS: There was no difference in the distribution of bacteria and antibiogram profile of the conjunctival microbiota in the preoperative of intravitreous injection of antiangiogenic for macular degeneration compared to the preoperative of cataract surgery.

Microbiota bacteriana da conjuntiva no pré-operatório de injeção intravítrea de antiangiogênico por degeneração macular relacionada à idade comparada com a de cirurgia de catarata / Preoperative conjunctival bacterial microbiota of antiangiogenic intravitreous injection for age-related macular degeneration compared to cataract surgery preoperative microbiota

Objetivo: Avaliar a microbiota bacteriana da conjuntiva e perfil de antibiograma no pré-operatório de injeção intravítrea de antiangiogênico por degeneração macular relacionada à idade, comparando com a de pacientes no pré-operatório de cirurgia de catarata. Métodos: Realizou-se estudo transversal, observacional, tipo série de casos. Foram constituídos dois grupos: grupo I (degeneração macular) com 26 olhos de 26 pacientes (12 homens/14 mulheres) com média de idades de 69,2 ± 11,5 anos; grupo II (catarata) com 27 olhos de 27 pacientes (9 homens/18 mulheres) com média de idades de 67,6 ± 7,9 anos. Os grupos foram homogêneos em relação à idade (p=0,538) e ao sexo (p=0,787). Foi realizada coleta de secreção do fundo de saco inferior da conjuntiva, através de "swab", e imediatamente colocado em tubo contendo meio líquido BHI ("brain heart infusion"). As amostras foram processadas conforme técnicas laboratoriais padrão e realizado antibiograma de cada colônia isolada. Resultados: Houve crescimento de 26 colônias bacterianas no grupo I, com 2 olhos não apresentando crescimento e 30 colônias no grupo II. Houve maior frequência de bactérias Gram positivas nos dois grupos: 23/26 colônias (88,4 por cento) no grupo I e 29/30 colônias (96,7 por cento) no grupo II, com predomínio de Staphylococcus aureus em ambos os grupos, com 16 amostras (61,5 por cento) e 17 (56,7 por cento), respectivamente. Staphylococcus coagulase negativa foi a segunda bactéria mais identificada, com 19,2 por cento no grupo I e 20,0 por cento no grupo II. Nenhuma diferença de frequência entre os grupos alcançou significância estatística. Não foi observada diferença estatisticamente significante nas sensibilidades das bactérias aos antibióticos testados entre os dois grupos. Conclusões: Não houve diferença na distribuição das bactérias e no perfil de antibiograma da microbiota conjuntival de pacientes no pré-operatório de injeção intravítrea por degeneração macular, comparada ...

Purpose: To evaluate the conjunctival bacterial microbiota and antibiogram profile in the preoperative of antiangiogenic intravitreous injection for age-related macular degeneration, and compare to the preoperative microbiota of patients submitted to cataract surgery. Methods: Cross-sectional, observational, case series study. Two groups were organized: group I (macular degeneration) with 26 eyes from 26 patients (12 men/14 women) with mean age of 69.2 ± 11.5 years; group II (cataract) with 27 eyes from 27 patients (9 men/18 women) with mean age of 67.6 ± 7.9 years. The groups were similar regarding age (p=0.538) and gender (p=0.787). The lower conjunctival sac was swabbed and the obtained material was immediately put in a tube filled with liquid culture media BHI ("brain heart infusion"). Samples were processed according to standard laboratory techniques and antibiogram was determined for each bacterial colony. Results: Twenty-six bacterial colonies growth in group I, with 2 eyes showing no growth and 30 colonies growth in group II. Gram positive bacteria were more prevalent in both groups: 23/26 colonies (88.4 percent) in group I and 29/30 colonies (96.7 percent) in group II, with a Staphylococcus aureus predominance in both groups, with 16 samples (61.5 percent) and 17 (56.7 percent), respectively. Coagulase negative Staphylococcus was the second most common identified bacteria, with 19.2 percent in group I and 20.0 percent in group II. No differences between the groups reached statistical significance. No statistically significant difference was noted on the antibiotic sensibility between both groups. Conclusions: There was no difference in the distribution of bacteria and antibiogram profile of the conjunctival microbiota in the preoperative of intravitreous injection of antiangiogenic for macular degeneration compared to the preoperative of cataract surgery.

Choroidal neovascularization enhanced by Chlamydia pneumoniae via Toll-like receptor 2 in the retinal pigment epithelium.

PURPOSE: Choroidal neovascularization (CNV) is directly related to visual loss in persons with age-related macular degeneration (AMD) and other macular disorders. Chlamydia pneumoniae, a prokaryotic pathogen that causes chronic inflammation, is recognized as a risk factor for cardiovascular diseases. In this study, the authors investigated the association between C. pneumoniae infection and AMD using a laser-induced CNV model in mice. METHODS: C57BL/6 mice, myeloid differentiation factor (MyD) 88 knockout (KO) mice, Toll-like receptor (TLR) 2 KO mice, and TLR4 KO mice were used. Experimental CNV was induced by rupturing the Bruch's membrane by laser photocoagulation (PC). Seven days after PC, the eyes were enucleated and the areas of CNV were measured in choroidal flat mounts. Cytokine gene expression by quantitative real-time PCR in the primary cultured retinal pigment epithelium (RPE) cells was also examined. RESULTS: Vitreous injection of the C. pneumoniae antigen increased the size of CNV. Although lipopolysaccharide stimulation can induce multiple cytokines, cultured mouse RPE cells from C57BL/6 mice expressed IL-6 and VEGF, but not TNF-alpha mRNA, in response to C. pneumoniae antigen. RPE cells from either MyD88 KO mice or TLR2 KO mice did not respond to the C. pneumoniae antigen. TLR2 KO mice did not augment the size increase of experimental CNV by C. pneumoniae antigen in vivo. CONCLUSIONS: C. pneumoniae can trigger inflammatory responses in the eye and promote experimental CNV in a TLR2-dependent manner. These data provide experimental evidence to imply persistent C. pneumoniae infection is a risk factor for AMD.

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.

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.

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.

Chlamydia pneumoniae is not detectable in subretinal neovascular membranes in the exudative stage of age-related macular degeneration.

PURPOSE: Age-related macular degeneration (AMD) is the most frequent cause of severe visual impairment in western countries, but its aetiology remains unclear. A growing body of evidence suggests that inflammation contributes to the pathogenesis of AMD, similarly to that shown for atherosclerosis. In view of a number of shared risk factors between the two entities and the hypothesized link between Chlamydia pneumoniae infection and atherosclerosis, we investigated whether C. pneumoniae might be involved in exudative AMD. METHODS: To examine whether C. pneumoniae contributes to the development of subretinal neovascular (SRNV) membranes in AMD, 13 consecutive SRNV membranes surgically excised from patients with exudative AMD were collected and assayed for the presence of C. pneumoniae or other bacterial pathogens by means of polymerase chain reaction (PCR). RESULTS: The age of patients ranged from 68 to 85 years (median 73.5 years). In all 13 SRNV membranes, no DNA of either C. pneumoniae or other pathogens was found by PCR. CONCLUSIONS: These findings indicate that C. pneumoniae is not associated with the development of SRNV membranes in exudative AMD.

Exposure to Chlamydia pneumoniae infection and progression of age-related macular degeneration.

Recent studies have found an association between exposure to Chlamydia pneumoniae infection and risk of age-related macular degeneration (AMD). To assess a potential risk of AMD progression posed by exposure to C. pneumoniae, the authors reexamined Australian residents in 2001-2002 who were aged 51-89 years with early AMD at baseline (1992-1995). Examination included macular photography and an enzyme-linked immunosorbent assay to determine antibody titers to the elementary bodies from C. pneumoniae AR39. AMD progression was assessed quantitatively, using both coarse and fine progression steps following an international classification for AMD grading, and also qualitatively, by side-by-side comparison of baseline and follow-up macular photographs. Serologic data were available for 246 of 254 (97%) subjects. AMD progression was associated with a higher antibody titer. After adjustment for age, smoking, family history of AMD, history of cardiovascular diseases, and source study, the subjects in the upper tertiles of antibody titers were 2.1 (95% confidence interval: 0.92, 4.69), 2.6 (95% confidence interval: 1.24, 5.41), and 3.0 (95% confidence interval: 1.46, 6.37) times more at risk of progression than those in the lowest tertile, using three definitions of progression, respectively. The fact that seroreactivity to C. pneumoniae was independently associated with the risk of AMD progression suggests that C. pneumoniae infection may be an additional risk factor for AMD progression.