Optical Coherence Tomography Angiography Characteristics of Polypoidal Lesions in Caucasians.

Purpose: The aim of the study is to analyze the swept source-optical coherence tomography angiography (SS-OCTA) characteristics of polypoidal lesions in Caucasian patients. Methods: In this retrospective observational case series, 43 polypoidal lesions in 32 eyes of 32 patients were diagnosed using indocyanine green angiography (ICGA) and compared to SS-OCTA at a tertiary medical retina center (Clinic Landstraße, Vienna Healthcare Group, Austria) between June 2017 and March 2020. Vascularity was identified by color-coded B-scan SS-OCTA while morphology was described as revealed by en face SS-OCTA after alignment with ICGA-confirmed findings. Results: In total, SS-OCTA detected all polypoidal lesions, as identified by ICGA. On B-scan SS-OCTA, circumscribed flow was detected in 33 (76.7%) polypoidal lesions and diffuse flow in 10 (23.3%) lesions. On en face SS-OCTA, polypoidal lesions appeared morphologically as 19 tangled vessel balls (44.2%), 6 tangled vessel balls next to dilated vessels (13.9%), 8 vascular dilatations (18.6%), and 8 ill-defined vascular networks (18.6%), leaving 2 lesions (4.6%) undetected. Circumscribed flow was significantly associated with tangled vessel balls (p = 0.005). Conclusion: This study highlights the importance of a multimodal imaging approach, including SS-OCTA, for the evaluation of polypoidal lesions. Our findings suggest a morphological heterogeneity of vascular patterns in Caucasian patients with polypoidal lesions, as pictured by SS-OCTA.

PASSED: Brain atrophy in non-demented individuals in a long-term longitudinal study from two independent cohorts.

Introduction: Alzheimer's disease (AD) is indicated by a decrease in amyloid beta 42 (Aß42) level or the Aß42/Aß40 ratio, and by increased levels of Tau with phosphorylated threonine at position 181 (pTau181) in cerebrospinal fluid (CSF) years before the onset of clinical symptoms. However, once only pTau181 is increased, cognitive decline in individuals with subjective or mild cognitive impairment is slowed compared to individuals with AD. Instead of a decrease in Aß42 levels, an increase in Aß42 was observed in these individuals, leading to the proposal to refer to them as nondemented subjects with increased pTau-levels and Aß surge with subtle cognitive deterioration (PASSED). In this study, we determined the longitudinal atrophy rates of AD, PASSED, and Biomarker-negative nondemented individuals of two independent cohorts to determine whether these groups can be distinguished by their longitudinal atrophy patterns or rates. Methods: Depending on their CSF-levels of pTau 181 (T), total Tau (tTau, N), Aß42 or ratio of Aß42/Aß40 (A), 185 non-demented subjects from the Alzheimer's Disease Neuroimaging Initiative (ADNI) and 62 non-demented subjects from Erlangen AD cohort were assigned to an ATN group (A-T-N-, A-T+N±, A+T-N±and A+T+N±) and underwent T1-weighted structural magnetic resonance imaging (sMRI). Longitudinal grey matter (GM) atrophy patterns were assessed with voxel-based morphometry (VBM) using the cat12 toolbox on spm12 (statistical parametric mapping) of MRI scans from individuals in the ADNI cohort with a mean follow-up of 2 and 5 years, respectively. The annualized atrophy rate for individuals in the Erlangen cohort was determined using region of interest analysis (ROI) in terms of a confirmatory analysis. Results: In the A-T+N± group, VBM did not identify any brain region that showed greater longitudinal atrophy than the A+T+N±, A+T+N± or biomarker negative control group. In contrast, marked longitudinal atrophy in the temporal lobe was evident in the A+T-N± group compared with A+T-N± and biomarker-negative subjects. The ROI in the angular gyrus identified by VBM analysis of the ADNI cohort did not discriminate better than the hippocampal volume and atrophy rate between AD and PASSED in the confirmatory analysis. Discussion: In this study, nondemented subjects with PASSED did not show a unique longitudinal atrophy pattern in comparison to nondemented subjects with AD. The nonsignificant atrophy rate compared with controls suggests that increased pTau181-levels without concomitant amyloidopathy did not indicate a neurodegenerative disorder.

OPTICAL COHERENCE TOMOGRAPHY AND OCT ANGIOGRAPHY CHARACTERISTICS OF INDOCYANINE GREEN ANGIOGRAPHIC PLAQUES IN NONEXUDATIVE AGE-RELATED MACULAR DEGENERATION.

PURPOSE: To describe characteristics of indocyanine green (ICG) angiographic plaques in the nonexudative fellow eye of White patients with unilateral treatment-naïve exudative neovascular age-related macular degeneration through optical coherence tomography (OCT) and OCT angiography (OCTA). METHODS: In this retrospective cross-sectional study, nonexudative eyes with ICG angiographic plaques were analyzed by OCT B-scans for the sensitivity of a double-layer sign, a pigment epithelium detachment, outer retinal atrophy, hyperreflective dots, and subretinal hyperreflective material (SRHM). The ICG angiographic plaque was matched with a macular neovascularization in OCTA en face scans and color-coded B scans. RESULTS: In total, 35 ICG angiographic plaques in 33 of 291 (11%) nonexudative eyes were diagnosed. OCT revealed 27 double-layer sign (78%), eight pigment epithelium detachment (23%), 8 outer retinal atrophy (23%), eight hyperreflective dots (23%), and one subretinal hyperreflective material (3%). OCTA confirmed a macular neovascularization in 28 plaques (80%): 7 (20%) in en face scans, 3 (9%) in color-coded B scans, and 18 (51%) in both. The area size in OCTA was significantly smaller than that of ICG angiography ( P = 0.002). CONCLUSION: The diagnosis of an ICG angiographic plaque in nonexudative fellow eyes of Whites with unilateral treatment-naïve exudative neovascular age-related macular degeneration was highly suggestive of a typical macular neovascularization type 1 as characterized by OCT and OCTA.

Amyloid-ß levels and cognitive trajectories in non-demented pTau181-positive subjects without amyloidopathy.

Phosphorylated Tau181 (pTau181) in CSF and recently in plasma has been associated with Alzheimer's disease. In the absence of amyloidopathy, individuals with increased total Tau levels and/or temporal lobe atrophy experience no or only mild cognitive decline compared with biomarker-negative controls, leading to the proposal to categorize this constellation as suspected non-Alzheimer's disease pathophysiology (SNAP). We investigated whether the characteristics of SNAP also applied to individuals with increased CSF-pTau181 without amyloidopathy. In this long-term observational study, 285 non-demented individuals, including 76 individuals with subjective cognitive impairment and 209 individuals with mild cognitive impairment, were classified based on their CSF levels of pTau181 (T), total Tau (N), amyloid-ß42 (Aß42) and Aß42/Aß40 ratio (A) into A+T+N±, A+T-N±, A-T+N±, and A-T-N-. The longitudinal analysis included 154 subjects with a follow-up of more than 12 months who were followed to a median of 4.6 years (interquartile range = 4.3 years). We employed linear mixed models on psychometric tests and region of interest analysis of structural MRI data. Cognitive decline and hippocampal atrophy rate were significantly higher in A+T+N± compared to A-T+N±, whereas there was no difference between A-T+N± and A-T-N-. Furthermore, there was no significant difference between A-T+N± and controls in dementia risk [hazard ratio 0.3, 95% confidence interval (0.1, 1.9)]. However, A-T+N± and A-T-N- could be distinguished based on their Aß42 and Aß40 levels. Both Aß40 and Aß42 levels were significantly increased in A-T+N± compared to controls. Long term follow-up of A-T+N± individuals revealed no evidence that this biomarker constellation was associated with dementia or more severe hippocampal atrophy rates compared to controls. However, because of the positive association of pTau181 with Aß in the A-T+N± group, a link to the pathophysiology of Alzheimer's disease cannot be excluded in this case. We propose to refer to these individuals in the SNAP group as 'pTau and Aß surge with subtle deterioration' (PASSED). The investigation of the circumstances of simultaneous elevation of pTau and Aß might provide a deeper insight into the process under which Aß becomes pathological.

Evaluation of a calculation model to estimate the impact of the COVID-19 pandemic lockdown on visual acuity in neovascular AMD.

PURPOSE: A model was calculated during the first Austrian coronavirus disease-2019 (COVID-19) pandemic lockdown to estimate the effect of a short-term treatment interruption due to healthcare restrictions on visual acuity (VA) in neovascular age-related macular degeneration (nAMD). The model was compared to the real-life outcomes before treatment re-started. METHODS: Retrospective data-collection of 142 eyes in 142 patients receiving repeated intravitreal injections with anti-VEGF at a retina unit in Vienna in a personalized pro-re-nata regimen prior to the COVID-19 associated lockdown, when treatment was deferred between March 16 and May 4, 2020. During the lockdown, the preliminary data was integrated into pre-existing formulae based on the natural course of the disease in untreated eyes in the long term. Patients were re-scheduled and treated after gradually opening operating rooms. The calculation model was compared to the effective VA change. RESULTS: The model calculated an overall VA loss of 3.5 ± 0.8 letters early treatment diabetes retinopathy study (ETDRS) (p < 0.001 [95% CI:3.3;3.6]) on average compared to 2.5 ± 6 letters ETDRS (p < 0.001 [95% CI:1.5;3.5]) as measured with a mean treatment delay of 61 ± 14 days after previously scheduled appointments. The total difference between the model exercise and the real-life outcomes accounted for 1 ± 5.9 letters ETDRS (p = 0.051 [95% CI: 0.1;1.9]). CONCLUSION: The herein presented calculation model might not be suitable to estimate the effective VA loss correctly over time, although untreated eyes and eyes under therapy show similarities after short-term treatment interruption. However, this study demonstrated the potentially negative impact of the COVID-19 pandemic lockdown on patients compromised by nAMD.

The Diagnostic Capability of Swept Source OCT Angiography in Treatment-Naive Exudative Neovascular Age-Related Macular Degeneration.

PURPOSE: To evaluate the capability of swept source-optical coherence tomography angiography (SS-OCTA) in the detection and localization of treatment-naive macular neovascularization (MNV) secondary to exudative neovascular age-related macular degeneration (nAMD). METHODS: In this prospective, observational case series, 158 eyes of 142 patients were diagnosed with exudative nAMD using fluorescein (FA) and indocyanine green angiography (ICGA) and evaluated by SS-OCTA in a tertiary retina center (Rudolf Foundation Hospital Vienna, Austria). The main outcome measure was the sensitivity of SS-OCTA compared to the standard multimodal imaging approach. Secondary outcome measure was the anatomic analysis of MNV in relation to the retinal pigment epithelium. RESULTS: En-face SS-OCTA confirmed a MNV in 126 eyes (sensitivity: 79.8%), leaving 32 eyes (20.2%) undetected. In 23 of these 32 eyes (71.9%), abnormal flow in cross-sectional SS-OCTA B-scans was identified, giving an overall SS-OCTA sensitivity of 94.3%. Eyes with a pigment epithelium detachment (PED) ≥ 300 µm had a smaller probability for correct MNV detection (p=0.015). Type 1 MNV showed a trend (p=0.051) towards smaller probability for the correct detection compared to all other subtypes. Other relevant factors for the nondetection of MNV in SS-OCTA were image artifacts present in 3 of 32 eyes (9.4%). SS-OCTA confirmed the anatomic localization of 93 in 126 MNVs as compared to FA (sensitivity: 73.8%). There was no influence of age, gender, pseudophakia, visual acuity, central foveal thickness, or subfoveal choroidal thickness on the detection rate of MNV. CONCLUSIONS: SS-OCTA remains inferior to dye-based angiography in the detection rate of exudative nAMD consistent with type 1 MNV and a PED ≥300 µm. The capability to combine imaging modalities and distinguish the respective MNV subtype improves its diagnostic value.

The Effect of Treatment Discontinuation During the COVID-19 Pandemic on Visual Acuity in Exudative Neovascular Age-Related Macular Degeneration: 1-Year Results.

INTRODUCTION: To evaluate the effect of a 9-week treatment deferral due to healthcare restrictions caused by Austria's first governmental lockdown associated with the coronavirus disease 2019 (COVID-19) pandemic on visual acuity (VA) in eyes compromised by exudative neovascular age-related macular degeneration (nAMD) after 1 year. METHODS: Retrospective data collection of 98 eyes (98 patients) with a treatment discontinuation at a tertiary eye care center (Clinic Landstraße, Vienna Healthcare Group, Austria) between March 16 and May 4, 2020. Prior to the lockdown, patients received multiple intravitreal injections (IVI) of anti-vascular endothelial growth factor with a personalized treatment interval for 3 years on average and at least three IVI after the lockdown. RESULTS: When the treatment interval doubled to 117.6 ± 31.4 days in spring 2020, patients lost 2.2 ± 4.6 ETDRS letters (p = 0.002) on average before reinitiating therapy. In total, 4.1 ± 8.1 letters (p < 0.0001) were lost despite continuous individual re-treatment over the course of the next year. In a univariate analysis, the extended interval time remained statistically significant (p < 0.0001), indicating a larger VA reduction within intervals with increasing interval time in days. CONCLUSION: The short-term treatment interruption had a persistent negative impact on the VA course of eyes under therapy after 1 year. Continuous therapy independent of the underlying treatment regimen remains of utmost importance in exudative nAMD. Our data should create awareness to regulators regarding future decisions despite the global pandemic.

Age-related macular degeneration (AMD) is the leading cause of legal blindness in developed countries. Wet AMD refers to the existence of new vessel growth in the macular, the part of the retina with the highest concentration of photoreceptors and hence the best visual acuity. The gold standard therapy of wet AMD consists of repeated injections of an antibody against new vessel formation into the eye to stabilize the disease. The sudden break of a treatment regimen for an individual person has never been investigated as it is ethically not acceptable. The coronavirus disease 2019 (COVID-19) pandemic and its associated lockdown led to an emerging situation in spring, 2020. We were forced by governmental restrictions to minimize contact with the most vulnerable patient cohort­the elderly. As an initial consequence, the Medical Retina Unit of Department of Ophthalmology (Clinic Landstraße, Vienna Healthcare Group, Austria) postponed appointments of patients with only one eye afflicted by wet AMD. This study examined the effect of a short-term treatment deferral caused by the first national COVID-19 lockdown in eyes of patients with ongoing therapy of wet AMD in Austria. The break led to a persistent visual loss despite re-treatment, which was still evident after 1 year. Our findings provide further support for an adequate and permanent therapy of wet AMD and regard intravitreal injections as urgent standard of care. It should be taken into consideration by authorities in future pandemic planning.

Comparison of macular neovascularization lesion size by the use of Spectral-Domain Optical Coherence Tomography Angiography and Swept-Source Optical Coherence Tomography Angiography versus Indocyanine Green Angiography.

PURPOSE: To compare the lesion sizes of macular neovascularization (MNV) imaged with spectral-domain (SD) and swept-source (SS) optical coherence tomography angiography (OCTA) as well as indocyanine green angiography (ICGA). METHODS: In this prospective, observational case series, patients showing a secured diagnosis of MNV on ICGA or Fluorescein Angiography, were imaged by SD-OCTA and SS-OCTA on the same day. Lesion size was measured on 3 × 3-mm2 and 6 × 6-mm2 scans using the Maestro 2 SD-OCTA (Topcon Corporation, Tokyo Japan) and the Triton SS-OCTA device (Topcon Corporation, Tokyo Japan) and compared to ICGA (Spectralis HRA, Heidelberg, Germany). RESULTS: Twenty eyes from 20 patients (11 females, 55%) were enrolled. The neovascularization area measured on 6 × 6-mm2 SD-OCTA was lower compared to that outlined on SS-OCTA, however, not reaching statistical significance (p = 0.094). Regarding 3 × 3-mm2 measurements, the median lesion sizes between the two OCTA devices were comparable (p = 0.492). Indocyanine green angiography depicted a larger lesion area than both OCTA devices, however, not reaching statistical significance. CONCLUSION: SD-OCTA tends to show smaller areas of MNV extension than SS-OCTA regarding 6 × 6 mm2 scans. The lesion size of MNV can be very well compared between the different devices, emphasizing the use of OCTA for monitoring neovascular area. Lesion measurements on SS-OCTA correlate better with ICGA than SD-OCTA.

Detection rate of diabetic macular microaneurysms comparing dye-based angiography and optical coherence tomography angiography.

Diabetic maculopathy (DM) is a microvascular dysfunction clinically characterized by microaneurysms (MA) leading to edema and central visual deprivation. This prospective explorative study investigated 27 eyes of 17 patients with DM by fluorescein/indocyanine green angiography (FA/ICGA; SPECTRALIS HRA-OCT, Heidelberg Engineering) and by swept source-optical coherence tomography angiography (SS-OCTA; DRI-OCT Triton Plus, Topcon) to identify clinically relevant MAs. The SS-OCTA cubes were split into the superficial capillary plexus (SCP) and the deep capillary plexus (DCP) according to the automated segmentation. The images of all modalities were superimposed for alignment by an Early Treatment Diabetic Retinopathy Study grid overlay and compared to each other. In total, the mean number of MAs in FA was 33.4 ± 22 (standard deviation) (median 27.5 [q1:21.75;q3:38.25]), in ICGA 24.9 ± 16.9 (17.5 [14;35]), in the SCP 6.5 ± 3.7 (5.5 [3.75;9.25]) and in the DCP 18.1 ± 10.5 (18.5 [10.75;23.5]). Mixed effects models between ICGA and the DCP were borderline significant (p = 0.048; 95% confidence interval 0.21 to 13.49), whereas all other imaging methods differed significantly. Quantitative analysis of MAs in DM showed a plausible agreement between ICGA and the DCP in SS-OCTA. These findings contribute to the imaging methodology in DM.

Correction to: Drusen characteristics of type 2 macular neovascularization in age-related macular degeneration.

An amendment to this paper has been published and can be accessed via the original article.

Drusen characteristics of type 2 macular neovascularization in age-related macular degeneration.

BACKGROUND: Type 2 macular neovascularization (MNV) is supposed to be a rare condition in age-related macular degeneration (AMD). The main purpose of this study was to assess accompanying factors of type 2 MNV in AMD. METHODS: Retrospective data analysis of eyes previously diagnosed with neovascular AMD in a tertiary eye care center (Medical Retina Unit, Rudolf Foundation Hospital, Vienna, Austria) between June 2008 and December 2017. Drusen subtypes, fibrosis, atrophy and subfoveal choroidal thickness (SFCT) of both eyes in patients with type 2 MNV lesions were categorized based on multimodal imaging. RESULTS: Type 2 MNV was diagnosed in 27 (3.2%) of 835 eyes (749 patients). Drusen characteristics in type 2 MNV were observed as followed: drusen < 63 µm in 2 eyes (7.4%), drusen ≥63 µm in 10 eyes (37%), subretinal drusenoid deposits (SDD) in 8 eyes (29.6%), cuticular drusen in 2 eye (7.4%) and no drusen were evident in 10 eyes (37%). Drusen distribution in 23 fellow eyes was detected as followed: drusen < 63 µm in 2 eyes (8.7%), drusen ≥63 µm in 9 eyes (39.1%), SDD in 5 eyes (21.7%), cuticular drusen in 1 eye (4.3%) and no drusen were evident in 9 eyes (39.1%). Mean SFCT was 140 ± 49 µm in affected eyes and 152 ± 41 µm in the fellow eyes. Patients with drusen or SDD were significantly younger (mean 70.88 ± 6.85, p = 0.04) than patients without deposits (mean 77.40 ± 5.74). CONCLUSIONS: Type 2 MNV remains a rare entity in AMD. It was frequently seen in the absence of drusen, a hallmark of AMD. These findings contribute to the heterogeneity of phenotypes related to pure type 2 lesions.

Seven-Year Visual and Anatomical Outcomes of Intravitreal Vascular Endothelial Growth Factor Inhibition for Neovascular Age-Related Macular Degeneration.

PURPOSE: To evaluate 7-year visual and anatomical outcomes of intravitreal injections (IVI) with antivascular endothelial growth factor (anti-VEGF) for neovascular age-related macular degeneration (nAMD) based on a personalized pro re nata (PRN) regimen. METHODS: Anonymized data of 124 consecutive eyes in 121 patients with treatment-naïve nAMD were initially collected in 2010. Of those, 45 received anti-VEGF IVI at least every 6months until 2017 in one single center in Austria and hence were retrospectively analyzed. All eyes had been initiated on a loading dose of 3 monthly IVI with different anti-VEGF agents followed by a PRN regimen in the first year. At year 2, monitoring as well as therapeutic intervention could be prolonged every 2weeks up to intervals of 3months without capping treatment. Primary outcome measure was the change of visual acuity (VA) assessed by Early Treatment Diabetic Retinopathy Study charts at 4 meters (ETDRS) in letters-counting every correctly read letter-and converted to Snellen. Secondary outcome measures were number of injections and change of central retinal thickness (CMT) from baseline. RESULTS: Mean baseline VA was 20/63 + 1 (0.63 ± 0.26 ETDRS) and declined to 20/100 + 2 (0.45 ± 0.33) with an overall loss of 9 letters ETDRS after 7years (p = 0.001). An average of 3.5 ± 1.9 IVI was given per year and eye. Mean CMT at baseline was 322 ± 95 µm, decreased by 52 µm, decreased by 52 µm, decreased by 52 µm, decreased by 52 µm to 270 ± 70 µm within the first year, and remained below baseline at year 7 (271 ± 106 µm; p = 0.001). An average of 3.5 ± 1.9 IVI was given per year and eye. Mean CMT at baseline was 322 ± 95 µm, decreased by 52 µm to 270 ± 70 µm within the first year, and remained below baseline at year 7 (271 ± 106 µm; p < 0.001). CONCLUSIONS: Our data confirm an absolute vision loss in eyes compromised by nAMD after 7 years of continuous VEGF inhibition. The visual decline was significantly related to baseline VA as well as the number of injections. We suggest following patients thoroughly independent of the initial VA and a greater incentive for the physician to treat.

Development of Secondary Choroidal Neovascularization in Focal Choroidal Excavation of Punctate Inner Choroidopathy.

Purpose: To elaborate a case of focal choroidal excavation (FCE) in punctate inner choroidopathy (PIC) complicated by secondary choroidal neovascularization (CNV) based on multimodal imaging findings.Methods: In this retrospective case report, multimodal imaging including near-infrared reflectance, blue peak autofluorescence, spectral domain-optical coherence tomography (OCT), fluorescein and indocyanine green angiography (Heidelberg Engineering GmbH, Germany), and swept source-OCT angiography (SS-OCTA; Topcon Corporation, Japan) was performed.Patients: A 27-year-old moderate myopic woman presented with inactive CNV of unknown origin in her left eye, which had been previously treated with intravitreal anti-vascular endothelial growth factor.Results: Multimodal imaging revealed PIC as the causative disease and systemic corticosteroids were administered. Similar complaints 13 months later showed new CNV formation at the already documented FCE. No sign of PIC could be detected at follow-up.Conclusion: This well-documented case highlighted FCE as the preferential location for CNV development in PIC with multimodal imaging emphasizing a chorioretinal entity.Summary: This case report demonstrated the clinical course of focal choroidal excavation in a patient initially diagnosed with punctate inner choroidopathy complicated by choroidal neovascularization and its treatment response, well documented by multimodal imaging including optical coherence tomography angiography.

Effect of intravitreal C3F8 gas in patients with vitreomacular traction: A retrospective case series.

BACKGROUND: We aimed to assess the efficacy of a single intravitreal perfluoropropane (C3F8) gas injection for the treatment of vitreomacular traction with or without a macular hole. METHODS: In this retrospective case series, seven eyes of six patients with symptomatic vitreomacular traction documented on optical coherence tomography, one with a macular hole additionally, received a single intravitreal C3F8 gas injection of up to 0.3 ml. The primary endpoint was vitreomacular traction release at 1 month after injection. Secondary endpoints included resolution of vitreomacular adhesion within 6 months, nonsurgical closure of macular holes, and change in central foveal thickness and best-corrected visual acuity. RESULTS: Overall, on optical coherence tomography, six of seven eyes (85.7%) had release of vitreomacular traction during the entire study duration: three within 1 month of injection and the other three within 6 months. Of the latter group, two of the three eyes showed a concurrent epiretinal membrane and one concurrent diabetic retino- and maculopathy. The patient with a macular hole had resolution of vitreomacular traction within 1 month but had to undergo vitrectomy because of nonclosure of the macular hole. Associated adverse events were macular edema with a consequent lamellar hole after injection in one patient, and another patient developed retinal detachment. CONCLUSION: Intravitreal C3F8gas injection is an inexpensive and promising minimally invasive option for the treatment of symptomatic and persistent vitreomacular traction with or without a macular hole. Further larger studies, especially comparing C3F8 gas injection with other treatment options, are needed.

The orientation of HIV-1 gp120 binding to the CD4 receptor differentially modulates CD4+ T cell activation.

Progressive quantitative and qualitative decline of CD4(+) T cell responses is one hallmark of HIV-1 infection and likely depends on several factors, including a possible contribution by the HIV-1 envelope glycoprotein gp120, which binds with high affinity to the CD4 receptor. Besides virion-associated and cell-expressed gp120, considerable amounts of soluble gp120 are found in plasma or lymphoid tissue, predominantly in the form of gp120-anti-gp120 immune complexes (ICs). Because the functional consequences of gp120 binding to CD4(+) T cells are controversially discussed, we investigated how gp120 affects TCR-mediated activation of human CD4(+) T cells by agonistic anti-CD3 mAb or by HLA class II-presented peptide Ags. We show that the spatial orientation of gp120-CD4 receptor binding relative to the site of TCR engagement differentially affects TCR signaling efficiency and hence CD4(+) T cell activation. Whereas spatially and temporally linked CD4 and TCR triggering at a defined site promotes CD4(+) T cell activation by exceeding local thresholds for signaling propagation, CD4 receptor engagement by gp120-containing ICs all around the CD4(+) T cell undermine its capacity in supporting proximal TCR signaling. In vitro, gp120 ICs are efficiently captured by CD4(+) T cells and thereby render them hyporesponsive to TCR stimulation. Consistent with these in vitro results we show that CD4(+) T cells isolated from HIV(+) individuals are covered with ICs, which at least partially contain gp120, and suggest that IC binding to CD4 receptors might contribute to the progressive decline of CD4(+) T cell function during HIV-1 infection.

Systemic antibody responses to gut microbes in health and disease.

Gastrointestinal commensal microbes usually exist in mutualistic relationship with their mammalian host. This relationship exists even though the mammalian host immune system is equipped with exquisite sensors for microbial chemical structures which trigger powerful immune defense mechanisms. Such beneficial mutualism is specifically maintained at the gut mucosal interface by a variety of physical and bioactive barriers as well as specific immunregulatory mechanisms. In addition, there is a strict compartmentalization between systemic and gut mucosal immunity--at least in inbred mice--which focuses adaptive immunity to gut microbes specifically to the gut tissue and the gut lumen. Only in circumstances of increased gut microbial exposure due to elevated gut epithelial permeability, due to genetic deficiencies in local defense mechanisms, due to imbalances in local immune regulation or in case of gastrointestinal pathogenic bacterial infections this compartmentalization is broken and systemic immune responses to gut microbes are induced, which manifest for example as systemic antibody responses specific for gut microbial antigens. Here we briefly discuss the abundance of systemic antibody responses to commensal gut bacteria in healthy humans and how it is altered in situations with chronic enteropathies such as in inflammatory bowel disease and HIV-1 infection or infection with gut bacterial pathogens.

Antigen-dependent and -independent mechanisms of T and B cell hyperactivation during chronic HIV-1 infection.

Continuous loss of CD4(+) T lymphocytes and systemic immune activation are hallmarks of untreated chronic HIV-1 infection. Chronic immune activation during HIV-1 infection is characterized by increased expression of activation markers on T cells, elevated levels of proinflammatory cytokines, and B cell hyperactivation together with hypergammaglobulinemia. Importantly, hyperactivation of T cells is one of the best predictive markers for progression toward AIDS, and it is closely linked to CD4(+) T cell depletion and sustained viral replication. Aberrant activation of T cells is observed mainly for memory CD4(+) and CD8(+) T cells and is documented, in addition to increased expression of surface activation markers, by increased cell cycling and apoptosis. Notably, the majority of these activated T cells are neither HIV specific nor HIV infected, and the antigen specificities of hyperactivated T cells are largely unknown, as are the exact mechanisms driving their activation. B cells are also severely affected by HIV-1 infection, which is manifested by major changes in B cell subpopulations, B cell hyperactivation, and hypergammaglobulinemia. Similar to those of T cells, the mechanisms underlying this aberrant B cell activation remain largely unknown. In this review, we summarized current knowledge about proposed antigen-dependent and -independent mechanisms leading to lymphocyte hyperactivation in the context of HIV-1 infection.

Systemic antibody responses to gut commensal bacteria during chronic HIV-1 infection.

BACKGROUND: Human systemic antibody responses to commensal microbiota are not well characterised during health and disease. Of particular interest is the analysis of their potential modulation caused by chronic HIV-1 infection which is associated with sustained enteropathy and systemic B cell disturbances reflected by impaired B cell responses and chronic B cell hyperactivity. The mechanisms underlying B cell hyperactivation and the specificities of the resulting hypergammaglobulinaemia are only poorly understood. METHODS: By a technique referred to as live bacterial FACS (fluorescence-activated cell sorting), the present study investigated systemic antibody responses to several gut and skin commensal bacteria as well as Candida albicans in longitudinal plasma and serum samples from healthy donors, chronic HIV-1-infected individuals with or without diarrhoea and patients with inflammatory bowel disease (IBD). RESULTS: The data show that systemic antibody responses to the commensal microbiota were abundantly present in humans and remained remarkably stable over years. Overall systemic antibody responses to gut commensal bacteria were not affected during chronic HIV-1 infection, with titres decreasing when normalised to elevated plasma immunoglobulin G (IgG) levels found in patients with HIV. In contrast, increases in the titres of high affinity antimicrobiota antibodies were detected in patients with IBD, demonstrating that conditions with known increased intestinal permeability and aberrant mutualism can induce changes in antibody titres observed in these assays. CONCLUSION: Neither HIV-associated enteropathy nor B cell dysfunction impact on the high-affinity systemic antibody responses to gut commensal bacteria. HIV-associated hypergammaglobulinaemia is therefore unlikely to be driven by induction of antimicrobiota antibodies.

HIV-1 replication activates CD4+ T cells with specificities for persistent herpes viruses.

Hyperactivation of CD4+ T cells is a hallmark of untreated HIV-1 infection. The antigenic specificities of activated CD4+ T cells and the underlying mechanisms leading to their activation remain thus far elusive. We report here that during HIV rebound the dynamics of HIV-specific CD4+ T cells is highly correlated with the dynamics of CD4+ T cells specific for persistent antigens derived from various members of the herpes virus family, whereas CD4 responses towards non-persistent antigens were unaffected by HIV replication. Notably, the dynamics of HIV and herpes viral antigen-specific CD4+ T cells responses correlated with the expression level of activation markers on dendritic cells (DCs) and activated DCs were more potent in restimulating memory T cells. These data strongly suggest that HIV replication costimulates activation of CD4+ T cells specific for persistent herpes viral antigens via activation of DCs. We propose that a large proportion of activated T cells during untreated HIV infection may be specific for herpes viral antigens and identify a novel mechanism contributing to chronic immune activation in untreated HIV-1 infection.

Intracellular Phospho-Flow cytometry reveals novel insights into TCR proximal signaling events. A comparison with Western blot.

Phospho-site specific antibodies become increasingly available, enabling the study of signaling events by Western blotting (WB) or intracellular flow cytometry (Phospho-Flow). Here we compared data generated by WB or Phospho-Flow regarding the kinetics and degree of phosphorylation of membrane proximal TCR signaling molecules. Phosphorylation events in Jurkat T cells were triggered by anti-CD3 stimulation (OKT3) or by oxidative stress (H(2)O(2)) and were analyzed by Phospho-Flow or WB. Both techniques showed that OKT3- or H(2)O(2)-induced, transient phosphorylation of ZAP70 or LAT was dependent on functional Lck. Phospho-Flow data revealed differences in the kinetics and the degree of H(2)O(2)- or OKT3-mediated protein phosphorylation compared with WB data. In addition, using Phospho-Flow we discovered that H(2)O(2)-induced phosphorylation of TCR signaling proteins was inhibited by small molecular weight kinase inhibitors far more potently than OKT3-triggered protein phosphorylation, despite a superior induction of phosphorylation by H(2)O(2). This finding was confirmed by WB. Interestingly, we identified by Phospho-Flow that, in P116 Jurkat cells lacking ZAP70 protein expression, H(2)O(2) potently triggered the phosphorylation of ZAP70 residues Y493 and Y292 but not Y319. The phosphorylation of these ZAP70 tyrosine residues cells was blocked by an Lck inhibitor, suggesting the existence of an Lck-coupled truncated ZAP70 protein or a novel isoform of ZAP70 in P116 cells. Phospho-Flow is a largely quantitative technology with excellent throughput, highly suited in studying the function or inhibition of TCR signaling pathways and allowing the detection of novel pathway insights. It can serve as a good complement to Western blot analysis.