Comparable cellular and humoral immunity upon homologous and heterologous COVID-19 vaccination regimens in kidney transplant recipients

Background

Kidney transplant recipients (KTRs) are at high risk for a severe course of coronavirus disease 2019 (COVID-19); thus, effective vaccination is critical. However, the achievement of protective immunogenicity is hampered by immunosuppressive therapies. We assessed cellular and humoral immunity and breakthrough infection rates in KTRs vaccinated with homologous and heterologous COVID-19 vaccination regimens.

Method

We performed a comparative in-depth analysis of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)–specific T-cell responses using multiplex Fluorospot assays and SARS-CoV-2-specific neutralizing antibodies (NAbs) between three-times homologously (n = 18) and heterologously (n = 8) vaccinated KTRs.

Results

We detected SARS-CoV-2-reactive T cells in 100% of KTRs upon third vaccination, with comparable frequencies, T-cell expression profiles, and relative interferon γ and interleukin 2 production per single cell between homologously and heterologously vaccinated KTRs. SARS-CoV-2-specific NAb positivity rates were significantly higher in heterologously (87.5%) compared to homologously vaccinated (50.0%) KTRs (P < 0.0001), whereas the magnitudes of NAb titers were comparable between both subcohorts after third vaccination. SARS-CoV-2 breakthrough infections occurred in equal numbers in homologously (38.9%) and heterologously (37.5%) vaccinated KTRs with mild-to-moderate courses of COVID-19.

Conclusion

Our data support a more comprehensive assessment of not only humoral but also cellular SARS-CoV-2-specific immunity in KTRs to provide an in-depth understanding about the COVID-19 vaccine–induced immune response in a transplant setting.

Dynamics of humoral and cellular immune responses after homologous and heterologous SARS-CoV-2 vaccination with ChAdOx1 nCoV-19 and BNT162b2

BACKGROUND

Vaccines are an important means to overcome the SARS-CoV-2 pandemic. They induce specific antibody and T-cell responses but it remains open how well vaccine-induced immunity is preserved over time following homologous and heterologous immunization regimens. Here, we compared the dynamics of humoral and cellular immune responses up to 180 days after homologous or heterologous vaccination with either ChAdOx1-nCoV-19 (ChAd) or BNT162b2 (BNT) or both.

METHODS

Various tests were used to determine the humoral and cellular immune response. To quantify the antibody levels, we used the surrogate neutralization (sVNT) assay from YHLO, which we augmented with pseudo- and real virus neutralization tests (pVNT and rVNT). Antibody avidity was measured by a modified ELISA. To determine cellular reactivity, we used an IFN-γ Elispot, IFN-γ/IL Flurospot, and intracellular cytokine staining.

FINDINGS

Antibody responses significantly waned after vaccination, irrespective of the regimen. The capacity to neutralize SARS-CoV-2 - including variants of concern such as Delta or Omicron - was superior after heterologous compared to homologous BNT vaccination, both of which resulted in longer-lasting humoral immunity than homologous ChAd immunization. All vaccination regimens induced stable, polyfunctional T-cell responses.

INTERPRETATION

These findings demonstrate that heterologous vaccination with ChAd and BNT is a potent alternative to induce humoral and cellular immune protection in comparison to the homologous vaccination regimens.

FUNDING

The study was funded by the German Centre for Infection Research (DZIF), the European Union's "Horizon 2020 Research and Innovation Programme" under grant agreement No. 101037867 (VACCELERATE), the "Bayerisches Staatsministerium für Wissenschaft und Kunst" for the CoVaKo-2021 and the For-COVID projects and the Helmholtz Association via the collaborative research program "CoViPa". Further support was obtained from the Federal Ministry of Education and Science (BMBF) through the "Netzwerk Universitätsmedizin", project "B-Fast" and "Cov-Immune". KS is supported by the German Federal Ministry of Education and Research (BMBF, 01KI2013) and the Else Kröner-Stiftung (2020_EKEA.127).

Hepatitis B Vaccine Non-Responders Show Higher Frequencies of CD24highCD38high Regulatory B Cells and Lower Levels of IL-10 Expression Compared to Responders

Background

The cellular mechanisms involved in the lack of protective antibody response after hepatitis B vaccination are still rather unclear. Regulatory B cells (Breg) known as modulators of B-and T-cell responses may contribute to poor vaccine responsiveness. The current study aimed to investigate the role of regulatory B cells (Breg) in hepatitis B vaccine non-responsiveness after immunization with second- or third-generation hepatitis B vaccines.

Method

We performed comparative phenotypic and frequency analysis of Breg subsets (CD24⁺CD27⁺ and CD24^highCD38^high Breg) in second-generation hepatitis B vaccine non-responders (2^nd HBvac NR, n = 11) and responders (2^nd HBvac R, n = 8) before (d0), on day 7 (d7), and 28 (d28) after booster vaccination. Cryopreserved peripheral blood mononuclear cells were stimulated ex vivo with a combination of CpG, PMA, and Ionomycin (CpG+P/I) and analyzed for numbers and IL-10 expression levels of Breg by flow cytometry-based analyses.

Results

Flow cytometry-based analyses revealed elevated frequencies of CD24⁺CD27⁺ Breg at all time points and significantly higher frequencies of CD24^highCD38^high Breg on d0 (p = 0.004) and 28 (p = 0.012) in 2^nd HBvac NR compared to 2^nd HBvac R. In parallel, we observed significantly lower levels of CpG+P/I-induced IL-10 expression levels of CD24⁺CD27⁺ and CD24^highCD38^high Breg (d0: p < 0.0001; d7: p = 0.0004; d28: p = 0.0003 and d0: p = 0.016; d7: p = 0.016, respectively) in 2^nd HBvac NR compared to 2^nd HBvac R before and after booster immunization. Frequencies of CD24⁺CD27⁺ and CD24^highCD38^high Breg significantly decreased after third-generation hepatitis B booster vaccination (d7: p = 0.014; d28: p = 0.032 and d7: p = 0.045, respectively), whereas IL-10 expression levels of both Breg subsets remained stable.

Conclusion

Here we report significantly higher frequencies of CD24^highCD38^high Breg in parallel with significantly lower IL-10 expression levels of CD24⁺CD27⁺ and CD24^highCD38^high Breg in 2^nd HBvac NR compared to 2^nd HBvac R. Anti-HBs seroconversion accompanied by a decrease of Breg numbers after booster immunization with a third-generation hepatitis B vaccine could indicate a positive effect of third-generation hepatitis B vaccines on Breg-mediated immunomodulation in hepatitis B vaccine non-responders.

Differential upregulation of host cell protein kinases by the replication of α-, β- and γ-herpesviruses provides a signature of virus-specific signalling

Infections with human herpesviruses share several molecular characteristics, but the diversified medical outcomes are distinct to viral subfamilies and species. Notably, both clinical and molecular correlates of infection are a challenging field and distinct patterns of virus-host interaction have rarely been defined; this study therefore focuses on the search for virus-specific molecular indicators. As previous studies have demonstrated the impact of herpesvirus infections on changes in host signalling pathways, we illustrate virus-modulated expression levels of individual cellular protein kinases. Current data reveal (i) α-, β- and γ-herpesvirus-specific patterns of kinase modulation as well as (ii) differential levels of up-/downregulated kinase expression and phosphorylation, which collectively suggest (iii) defined signalling patterns specific for the various viruses (VSS) that may prove useful for defining molecular indicators. Combined, the study confirms the correlation between herpesviral replication and modulation of signalling kinases, possibly exploitable for the in vitro characterization of viral infections.

Evaluation of T-activated proteins as recall antigens to monitor Epstein-Barr virus and human cytomegalovirus-specific T cells in a clinical trial setting

BACKGROUND

Pools of overlapping synthetic peptides are routinely used for ex vivo monitoring of antigen-specific T-cell responses. However, it is rather unlikely that these peptides match those resulting from naturally processed antigens. T-activated proteins have been described as immunogenic and more natural stimulants, since they have to pass through antigen processing and comprise activation of all clinically relevant effector cell populations.

METHODS

We performed comparative analysis of numbers and cytokine expression pattern of CD4 and CD8 T cells after stimulation with recombinant, urea-formulated T-activated EBV-BZLF1, -EBNA3A, and HCMV-IE1, and -pp65 proteins or corresponding overlapping peptide pools. Freshly isolated and cryopreserved PBMC of 30 EBV- and 19 HCMV-seropositive and seven EBV- and HCMV-seronegative subjects were stimulated ex vivo and analysed for IFN-γ, TNF and IL-2 production by flow cytometry-based intracellular cytokine staining.

RESULTS

T-activated proteins showed a high specificity of 100% (EBV-BZLF1, HCMV-IE1, and -pp65) and 86% (EBV-EBNA3A), and a high T-cell stimulatory capacity of 73-95% and 67-95% using freshly isolated and cryopreserved PBMC, respectively. The overall CD4 T-cell response rates in both cohorts were comparable after stimulation with either T-activated protein or peptide pools with the exception of lower numbers of CD8 T cells detected after stimulation with T-activated EBV-EBNA3A- (p = 0.038) and HCMV-pp65- (p = 0.0006). Overall, the number of detectable antigen-specific T cells varied strongly between individuals. Cytokine expression patterns in response to T-activated protein and peptide pool-based stimulation were similar for CD4, but significantly different for CD8 T-cell responses.

CONCLUSION

EBV and HCMV-derived T-activated proteins represent innovative, highly specific recall antigens suitable for use in immunological endpoint assays to evaluate success or failure in immunotherapy clinical trials (e.g. to assess the risk of EBV and/or HCMV reactivation after allogenic hematopoietic stem cell transplantation). T-activated proteins could be of particular importance, if an impaired antigen processing (e.g. in a post-transplant setting) must be taken into account.

Epstein-Barr virus strain heterogeneity impairs human T-cell immunity

The Epstein-Barr virus (EBV) establishes lifelong infections in > 90% of the human population. Although contained as asymptomatic infection by the immune system in most individuals, EBV is associated with the pathogenesis of approximately 1.5% of all cancers in humans. Some of these EBV-associated tumors have been successfully treated by the infusion of virus-specific T-cell lines. Recent sequence analyses of a large number of viral isolates suggested that distinct EBV strains have evolved in different parts of the world. Here, we assessed the impact of such sequence variations on EBV-specific T-cell immunity. With the exceptions of EBNA2 and the EBNA3 family of proteins, an overall low protein sequence disparity of about 1% was noted between Asian viral isolates, including the newly characterized M81 strain, and the prototypic EBV type 1 and type 2 strains. However, when T-cell epitopes including their flanking regions were compared, a substantial proportion was found to be polymorphic in different EBV strains. Importantly, CD4+ and CD8+ T-cell clones specific for viral epitopes from one strain often showed diminished recognition of the corresponding epitopes in other strains. In addition, T-cell recognition of a conserved epitope was affected by amino acid exchanges within the epitope flanking region. Moreover, the CD8+ T-cell response against polymorphic epitopes varied between donors and often ignored antigen variants. These results demonstrate that viral strain heterogeneity may impair antiviral T-cell immunity and suggest that immunotherapeutic approaches against EBV should preferably target broad sets of conserved epitopes including their flanking regions.

Training Load, Immune Status, and Clinical Outcomes in Young Athletes: A Controlled, Prospective, Longitudinal Study

Introduction: Beside positive effects on athlete's health, competitive sport can be linked with an increased risk of illness and injury. Because of high relative increases in training, additional physical and psychological strains, and an earlier specialization and professionalization, adolescent athletes needs an increased attention. Training can alter the immune system by inducing a temporary immunosuppression, finally developing infection symptoms. Previous studies identified Epstein Barr Virus (EBV) as potential indicator for the immune status. In addition to the identification of triggering risk factors for recurrent infections, the aim was to determine the interaction between training load, stress sense, immunological parameters, and clinical symptoms.

Methods: A controlled, prospective, longitudinal study on young athletes (n = 274, mean age: 13.8 ± 1.5 yrs) was conducted between 2010 and 2014. Also 285 controls (students, who did not perform competitive sports, mean age: 14.5 ± 1.9 yrs) were recruited. Athletes were examined 3 times each year to determine the effects of stress factors (training load: training hours per week [Th/w]) on selected outcome parameters (clinical [susceptibility to infection, WURSS-21: 21-item Wisconsin Upper Respiratory Symptom Survey], immunological, psychological end points). As part of each visit, EBV serostatus and EBV-specific IgG tiers were studied longitudinally as potential immune markers.

Results: Athletes (A) trained 14.9 ± 5.6 h weekly. Controls (C) showed no lower stress levels compared to athletes (p = 0.387). Twelve percent of athletes reported recurrent infections (C: 8.5%, p = 0.153), the presence of an upper respiratory tract infection (URTI) was achieved in 30.7%. EBV seroprevalence of athletes was 60.3% (C: 56.6%, p = 0.339). Mean EBV-specific IgG titer of athletes was 166 ± 115 U/ml (C: 137 ± 112 U/ml, p = 0.030). With increasing Th/w, higher stress levels were observed (p < 0.001). Analyzes of WURSS-21 data revealed no relationship to training load (p = 0.323). Also, training load had no relation to EBV serostatus (p = 0.057) or the level of EBV-specific IgG titers (p = 0.364).

Discussion: Young elite athletes showed no increased sense of stress, no higher prevalence of recurrent infections, and no different EBV-specific serological parameters compared to controls. Also, no direct relationship between training loads, clinical complaints, and EBV-specific immune responses was found. With increasing training loads athletes felt more stressed, but significant associations to EBV-specific serological parameters were absent. In summary, EBV serostatus and EBV-specific IgG titers do not allow risk stratification for impaired health. Further investigations are needed to identify additional risk factors and immune markers, with the aim to avoid inappropriate strains by early detection and following intervention.

Kanaloplastik ab interno – eine minimalinvasive Alternative

Zweck Beschreibung und Bewertung der Wirksamkeit der Kanaloplastik ab interno (ABiC) bei Patienten mit primärem Offenwinkelglaukom (POAG).

Methoden In diese monozentrische konsekutive Fallstudienreihe wurden Patienten mit Katarakt und Offenwinkelglaukom (kombiniertes Verfahren) und pseudophake Patienten (Durchschnittsalter: 78 Jahre, Bereich: 66–90 Jahre) mit POAG aufgenommen und einer ABiC mit dem iTrack™ 250-Mikron-Mikrokatheter (Ellex Medical Lasers Pty Ltd, Adelaide, Australien) unterzogen, um den Schlemm-Kanal zirkumferenziell zu viskodilatieren und zu intubieren, ohne eine Spannnaht anzubringen. Die primären Endpunkte waren der mittlere Augeninnendruck (IOP) und die mittlere Anzahl Glaukommedikamente bis 1, 3, 6, 9 und 12 Monate nach der Operation.

Ergebnisse 23 Patienten (23 Augen) wurden in die Studie aufgenommen. Der mittlere IOP ohne Wash-out sank von 18,8 ± 5,63 mmHg vor der Operation auf jeweils 14,9 ± 2,90 mmHg (n = 22), 13,82 ± 2,98 (n = 19), 14,69 ± 2,36 mmHg (n = 13), 16,0 ± 2,09 (n = 11) und 14,73 ± 2,97 (n = 11) bis 1, 3, 6, 9 und 12 Monate nach der Operation. Die mittlere Anzahl Medikamente wurde reduziert von 1,69 vor der Operation auf 0,21 bei der letzten Follow-up-Visite. Es gab eine Komplikation mit begrenzter Descemetolyse nahe dem Limbus.

Schlussfolgerung Die ABiC war bei dieser Patientengruppe einfach in der Durchführung und brachte nur minimale Komplikationen mit sich. Erste Ergebnisse in dieser Studie weisen darauf hin, dass die ABiC den IOP und somit auch die Abhängigkeit von Medikamenten vergleichbar zur konventionellen Kanaloplastik senkt.

Validation of an IFNγ/IL2 FluoroSpot assay for clinical trial monitoring

Background

The FluoroSpot assay, an advancement of the ELISpot assay, enables simultaneous measurement of different analytes secreted at a single-cell level. This allows parallel detection of several cytokines secreted by immune cells upon antigen recognition. Easier standardization, higher sensitivity and reduced labour intensity render FluoroSpot assays an interesting alternative to flow-cytometry based assays for analysis of clinical samples. While the use of immunoassays to study immunological primary and secondary endpoints becomes increasingly attractive, assays used require pre-trial validation. Here we describe the assay validation (precision, specificity and linearity) of a FluoroSpot immunological endpoint assay detecting Interferon γ (IFNγ) and Interleukin 2 (IL2) for use in clinical trial immune monitoring.

Methods

We validated an IFNγ/IL2 FluoroSpot assay to determine Epstein-Barr virus (EBV)-specific cellular immune responses (IFNγ, IL2 and double positive IFNγ + IL2 responses), using overlapping peptide pools corresponding to EBV-proteins BZLF1 and EBNA3A. Assay validation was performed using cryopreserved PBMC of 16 EBV-seropositive and 6 EBV-seronegative donors. Precision was assessed by (i) testing 16 donors using three replicates per assay (intra-assay precision/repeatability) (ii) using two plates in parallel (intermediate precision/plate-to-plate variability) and (iii) by performing the assays on three different days (inter-assay precision/reproducibility). In addition, we determined specificity, linearity and quantification limits of the assay. Further we tested precision across the two assay systems, IFNγ/IL2 FluoroSpot and the corresponding enzymatic single cytokine ELISpot.

Results

The validation revealed: (1) a high intra-assay precision (coefficient of variation (CV) 9.96, 8.85 and 13.05 %), intermediate precision (CV 6.48, 10.20 and 12.97 %) and reproducibility (CV 20.81 %, 12,75 % and 12.07 %) depending on the analyte and antigen used; (2) a specificity of 100 %; (3) a linearity with R² values from 0.93 to 0.99 depending on the analyte. The testing of the precision across the two assay systems, adduced a concordance correlation coefficient p_c = 0.99 for IFNγ responses and p_c = 0.93 for IL2 responses, indicating a large agreement between both assay methods.

Conclusions

The validated primary endpoint assay, an EBV peptide pool specific IFNγ/IL2 FluoroSpot assay was found to be suitable for the detection of EBV-specific immune responses subject to the requirement of standardized assay procedure and data analysis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-016-0932-7) contains supplementary material, which is available to authorized users.

An optimized IFN-γ ELISpot assay using T-activated ® proteins for determination of CMV-specific cell-mediated immunity

In healthy individuals, Cytomegalovirus (CMV) infections are controlled by CMV-specific cell-mediated immunity (CMI). However, functional impairment of the CMI in immunocompromized individuals can lead to uncontrolled CMV-replication. Thus, monitoring CMV-specific CMI is highly relevant for the prognosis of CMV-associated diseases. Here we show the optimization and technical validation of a monitoring tool for the determination of CMV-specific CMI.

Phenotype, quantity and cytokine expression profile of T cells from 19 CMV-seropositive healthy donors reactivated by CMV (IE-1, pp65) -specific pools of overlapping 15mer peptides and the corresponding T-activated proteins® were compared using a 10-parameter flow cytometry-based intracellular cytokine staining assay. Subsequently, an IFN-g ELISpot protocol using T-activated proteins® was established and validated.

Pp65 peptide pool stimulation revealed significant higher CD8+ T-cell responses as the corresponding T-activated proteins® (p=0.006). CD4+ T-cell responses however were comparable. Testing of T-activated proteins® in seronegative donors revealed a specificity of 100%. Use of T-activated proteins® with the optimized IFN-g ELISpot resulted in coefficients of variation for inter-assay, inter-operator and inter-site variations of less than 22 %. A linear correlation between the amount of CMV protein-reactive cells and total PBMC counts was observed.

Given the natural antigen processing of T-activated proteins® along the cross-presentation pathway, reflecting the in vivo situation, these proteins in combination with the optimized IFN-g ELISpot serve as a valuable tool to monitor the CMV-specific CMI.

[Can an intrascleral implant and/or the combined cataract surgery improve the long-term outcome of viscocanalostomy in glaucoma?]

BACKGROUND

Beside the established methods in glaucoma surgery, several procedures have been developed in the recent past including viscocanalostomy as a non-penetrating surgery. The efficiency of a combination of this procedure with an intrascleral implant and/or with cataract surgery was examined in this retrospective study over a period to 60 months postoperatively.

PATIENTS AND METHODS

67 eyes from 49 patients with glaucoma were operated in two different operational groups. 39 eyes had a viscocanalostomy (Group "V"). 16 eyes in this group additionally got a T-Flux implant ("ViskoT"), 23 did not ("Visko"). A combined cataract extraction and viscocanalostomy was undertaken in 28 eyes (Group "VK"), 18 of which did not ("ViskoKa"), and 10 of which did receive a T-flux implant ("ViskoKaT").

RESULTS

The mean preoperative intraocular pressure was 27.1 ± 4.5 mmHg and went down to 17.4 ± 2.9 mmHg postoperative up to the point of 60 months: there was a significant difference in the overall postoperative intraocular pressure in comparison to the preoperative intraocular pressure. There was, however, no significant effect to be found until after 5 years on the postoperative intraocular pressure by cataract extractions and also not by the implantation of a T-Flux. However, significantly less medication was applied up to the postoperative point of 12 and 36 months in the group with cataract surgery (VK). This difference was lost in the course of time and was no longer detectable after 60 months. However, an overall rise in both medication and goniopuncture (31.3 %) of the Descemet using YAG laser was necessary in the course of time, in order to keep a constant level of the postoperative intraocular pressure.

CONCLUSIONS

Viscocanalostomy represents a safe surgical antiglaucomatous method for improving the intraocular pressure. A respective clinical improvement could be observed during the follow-up period of up to 60 months. The prognosis of intraocular pressure does not improve by the use of intrascleral implants and viscocanalostomy with simultaneous cataract surgery, however.

Overnight resting of PBMC changes functional signatures of antigen specific T- cell responses: impact for immune monitoring within clinical trials

Polyfunctional CD4 or CD8 T cells are proposed to represent a correlate of immune control for persistent viruses as well as for vaccine mediated protection against infection. A well-suited methodology to study complex functional phenotypes of antiviral T cells is the combined staining of intracellular cytokines and phenotypic marker expression using polychromatic flow cytometry. In this study we analyzed the effect of an overnight resting period at 37°C on the quantity and functionality of HIV-1, EBV, CMV, HBV and HCV specific CD4 and CD8 T-cell responses in a cohort of 21 individuals. We quantified total antigen specific T cells by multimer staining and used 10-color intracellular cytokine staining (ICS) to determine IFNγ, TNFα, IL2 and MIP1β production. After an overnight resting significantly higher numbers of functionally active T cells were detectable by ICS for all tested antigen specificities, whereas the total number of antigen specific T cells determined by multimer staining remained unchanged. Overnight resting shifted the quality of T-cell responses towards polyfunctionality and increased antigen sensitivity of T cells. Our data suggest that the observed effect is mediated by T cells rather than by antigen presenting cells. We conclude that overnight resting of PBMC prior to ex vivo analysis of antiviral T-cell responses represents an efficient method to increase sensitivity of ICS-based methods and has a prominent impact on the functional phenotype of T cells.

Indocyanine green fluorescence-guided sentinel lymph node biopsy in dermato-oncology

BACKGROUND

Sentinel lymph node biopsy (SLNB) for cutaneous malignancies usually carried out with radioactive nanocolloids (Tc-99m). The SLNE is controversially discussed internationally. This is especially given to the high false-negative rate up to 44 %. An alternative could be the fluorescent dye indocyanine green (ICG).

MATERIAL AND METHODS

We investigated the advantage of intraoperative fluorescence detection of lymphatic vessels and SLN with a Near-Infrared (NIR) camera in comparison to conventional methods using preoperative lymphoscintigraphy and SPECT/CT in 22 patients with malignant melanoma.

RESULTS

A total of 61 SLNs were removed in 22 operative procedures. In 7 SLN (10.3 %; 7/68) the histopathological assessment could demonstrate a metasta-tic involvement. 11 additional SLN (19.1 %) in 8 patients were only identified using the fluorescent labeling. Two of these additional SLN (9.1 %; 2/22) showed metastatic involvement.

CONCLUSION

The ICG fluorescence-guided SLNB is an innovative imaging technique for dermato-oncology, reliable and providing additional information in the detection of SLN. Therefore SLNB with fluorescence-dye is an attractive option with intraoperative real-time lymphoscintigraphy to improve the detection of SLN in cutaneous malignancies and potential reduction of the false negative rate in SLN.

Video fluorescein angiography: method and clinical application

Video fluorescein angiography, combined with a picture analyzing system, is a clinically applicable, objective method of evaluating the retinal blood-flow parameters. Optical density measurements were performed on videorecordings of fluorescence angiograms by means of a picture-analyzing system in order to determine the circulation parameters of the retina. These included: the arm-retina time (ART), the arteriovenous passage time (AVP), and the mean arterial dye-bolus velocity (MDV). Normal values for these parameters were derived from measurements in 75 healthy volunteers. The mean arm-retina time (ART) was 11.2 +/- 3.3 s, the mean arteriovenous passage time (AVP) 1.45 +/- 0.4 s and the mean arterial dye-bolus velocity (MDV) 6.39 +/- 1.7 mm/s. No significant correlation could be shown between pulse or blood pressure and one of the retinal circulation parameters. A group of ten healthy volunteers was examined twice in order to obtain the intraindividual variation for the measuring parameters. The coefficient of variation for the ART was 18%, 10% for the AVP, and 26% for the MDV.

Measurement of retinal blood flow in various pathological conditions by video fluorescence angiography

Many ophthalmological disorders are due to poor local microcirculation, examples being central retinal vein occlusion, acute retinal artery occlusion, and ischaemic eye disease. Generalized changes have been found in arterial hypertension, diabetes mellitus, and arteriosclerosis. It is only at a few places that the microcirculation can be investigated non-invasively in man, and in this connection the retina is of particular interest because it is one of the regions supplied by the intracranial part of the internal carotid. The retinal blood supply is divided into four clearly separate quadrants, normally not communicating via anastomoses. The time of the arteriovenous passage (AVP) can therefore serve as a good indicator of retinal microcirculation. This parameter was measured before and after treatment in patients with diabetic retinopathy, angiosclerosis of the fundus, and lacunar stroke. Video fluorescence angiography reveals the abnormalities of the microcirculation in the area supplied by the carotid artery and can be used to check on therapeutic effects.

Microcirculation and hemorheology of children with type I diabetes

A group of 53 children, suffering from diabetes mellitus type I and a group of 12 healthy children were compared. In both groups the following data were determined: Haemoglobin A1C, retinal blood flow (video fluorescence angiography), erythrocyte velocity in finger nailfold capillaries (video capillaroscopy), capillary tortuosity, plasma viscosity, erythrocyte rigidity, and haematocrit. The degree of capillary tortuosity was significantly elevated and erythrocyte velocity was significantly diminished in the group of diabetic children in comparison to the healthy children. Regarding rheological data there was a significant decrease in erythrocyte deformability for the diabetic children. Diabetic children with good stabilization presented better rheological parameters than the poorly stabilized ones. Although these findings provided sufficient information, it will be necessary to cover a long follow up period to judge the prognosis of good and poorly stabilized diabetic children.

Circulatory parameters of the retina in patients with lacunar stroke

Ophthalmological data were obtained in 40 patients presenting with lacunar stroke. The stroke was verified clinically as well as by computed tomography. Vision was tested and the visual field, intraocular pressure, retinal arteriovenous passage time, arm-retina time, and erythrocyte flow velocity in the conjunctival capillaries were all determined; ophthalmoscopy was also carried out. Microcirculatory parameters were obtained from 21 patients. Significant disturbances of the retinal arteriovenous passage time were observed, but there were no significant disturbances of the conjunctival erythrocyte flow velocity. The concurrently measured haemorheological parameters were all pathological with the exception of the haematocrit. Ophthalmoscopic examination revealed arteriosclerotic alterations in 38 of 40 patients. These angiological and rheological findings confirm the importance of disturbed microcirculation in lacunar stroke.

The haemorheological features of lacunar strokes

Clinical and haemorheological data were recorded in 40 patients with lacunar strokes confirmed clinically and by computed tomography. The following haemorheological variables were monitored: haematocrit, erythrocyte aggregation, erythrocyte deformability, plasma viscosity, fibrinogen concentration and yield shear stress. Clinically, most patients had case histories and features according to the description of Fisher. All haemorheological parameters with the exception of the haematocrit were pathological when compared with values obtained from a normal control group. In descending order of frequency the pathological changes were in erythrocyte aggregation, plasma viscosity and erythrocyte deformability.

[Television fluorescence angiography and image analysis: clinical use with a case example]

The clinical application of TV fluorescein angiography with subsequent image analysis as performed on a patient with familial Mediterranean fever (FMF), who was suffering from an arterial branch occlusion, is discussed. In addition, the diagnostic relevance of rheologic parameters to the diagnostic evaluation of retinal circulatory disorders is emphasized.

The capillary tube plasma viscometer--an automatical instrument for measuring plasma viscosity

A new capillary viscometer was developed to eliminate the measuring errors due to insufficient cleaning or the residue of cleaning solution in the capillary. A disposable polyurethane tube which can be discarded after each determination is used as a measuring chamber. This device has been constructed for bed-side application (light weight, dry, thermostat-controlled measuring capillaries, short measuring period, automated process, and easy operation). The PEARSON correlation coefficient for comparative measurements with the COULTER-HARKNESS viscometer was r = 0.979.

Quantification of characteristic blood-flow parameters in the vessels of the retina with a picture analysis system for video-fluorescence angiograms: initial findings

Fluorescence angiograms of the retina were performed on 12 healthy, adult subjects between the ages of 20 and 52 years with a 30 degrees fundus camera (C. Zeiss), a low-light TV camera and a video recorder. Characteristic blood-flow parameters for the retina were obtained from the video recording using the picture-analysis system (Mikrovideomat 3, C. Zeiss). These included: the arm-retina time (ART), the arteriovenous passage time (AVP) and the arterial contrast-medium velocity (ACMV). Normal values for these parameters were derived for the four retinal quadrants and then discussed. In addition, the filling characteristics of venules were measured and discussed.

Measuring the microcirculation in the human conjunctiva bulbi under normal and hyperperfusion conditions

We present a system consisting of a slit lamp stereomicroscope and an adapted video system for the examination of the conjunctival microcirculation. This system permits measurement of the flow of erythrocytes in the vessels of the bulbar conjunctiva. We present values obtained from clinically normal individuals under normal conditions and under conditions of hyperperfusion.

Rheologic findings in patients with acute central retinal artery occlusion

The most important rheologic parameters were examined in six patients with acute occlusion of the central retinal artery. Blood samples were taken as part of the initial clinical examination on the day of the occlusion before the onset of therapy, and the following parameters were studied: (1) yield shear stress; (2) hematocrit; (3) plasma viscosity; (4) extent of erythrocyte aggregation; (5) erythrocyte deformability; (6) plasma fibrinogen concentration. A definite shear stress could be measured in all patients, something not possible in rheologically healthy volunteers. Hematocrit values were in the upper normal range; plasma viscosity was significantly increased. The extent of erythrocyte aggregation was greater than normal, erythrocyte deformability was markedly reduced, and the plasma fibrinogen was markedly higher than the normal level. Aside from the well-known pathologic findings in the carotid arteries of many patients with acute retinal vascular occlusion, rheologic factors seem to be of great importance in this disease.

[Arterial retinal circulatory disorders: an urgent indication for Doppler sonographic study of the carotid flow system]

Nineteen subjects with retinal strokes of different degrees of severity (amaurosis fugax, occlusion of individual retinal arteries or of the central retinal artery) were examined by continuous-wave Doppler sonography. Evaluation of periorbital Doppler flow and direct examination of the major neck vessels were performed. Twelve subjects presented with homolateral arteriosclerotic lesions at the carotid bifurcation. The ultrasonographic findings were confirmed by carotid arteriography. High-grade stenosis or occlusion of the internal carotid artery were found in approximately 50% of the patients; the remainder turned out to have low-grade stenoses or nonstenosing plaques. These findings emphasize the role of emboli from the major neck arteries in the pathogenesis of retinal and cerebral insults. Hemodynamic effects seem to be of minor significance. Continuous-wave Doppler sonography is a completely non invasive, but nevertheless reliable method for the detection of clinically relevant carotid lesions. Especially patients suffering from retinal insults should be examined by Doppler sonography, since they are at high risk for further cerebral stroke.

[Capabilities and limitations of TV fluorescein angiography of the retina (author's transl)]

The authors report on their experience with television fluorescein angiography (TVFA) in routine clinical work. Examples of possible indications and the technical-optical limitations of the procedure are described.

[Utility of low light level television cameras for the fluorescein angiography of the retina (author's transl)]

A survey of the major proportion of low-light level TV cameras available on the German market is described. A comparison and an assessment of the applicability of televised fluorescein angiography were carried out with the aid of technical data and measured results. It became evident that some systems were practicable for clinical use. With those it was possible to record angiograms at minimal illumination levels and patient inconvenience was reduced significantly. Measurements of blood flow parameters were possible with good temporal and geometrical resolution and full reproducibility.

[Televised flurescein angiography of the retina--new technical aspects (author's transl)]

A television-fundus-camera is described, which makes possible video-tape recordings of both conventional fundal- appearances as well as fluorescein-angiograms. Minimal illumination of the fundus with a spectral lamp is utilized. The use of a spectral lamp optimizes the excitation of fluorescein dye and the intensity of the illumination can therefore be reduced to a minimal level. Thus, patient inconvenience is minimized and ocular immobility can be maintained for the duration of the examination, which results in better quality recordings.