Closed Panel Discussion
NIH Campus, Building 50, Rooms 1227/1233
March 7, 2014, 9:00am– 2:00pm
Invited Panel Members
Arne Akbar, PhD; Professor of Immunology and Associate, Institute of Healthy Ageing, UCL.
Alan Bird, MD; Emeritus Professor of Medical Ophthalmology, Honorary Consultant, Moorfields Eye Hospital.
Rachel Caspi, PhD; Immunoregulation Section Head, Laboratory of Immunology, NEI.
Chi-Chao Chan, MD; Immunopathology Section Head, Laboratory of Immunology, NEI.
**Pete Coffey, DPhil; Professor, Cellular Therapy and Visual Sciences, UCL. Director, London Project to Cure Blindness.
Andrew Dick, BSc, MBBS, MD, FRCS, FRCP, FRCOphth, FMedSci; Professor of Ophthalmology, Infection and Immunity Research, University of Bristol. Theme lead-Inflammation and immunotherapy, NIHR Biomedical Research Centre.
Charles Egwuagu, PhD, MPH; Molecular Imaging Section Head, Laboratory of Immunology, NEI.
Frederick Ferris, MD; Director, Division of Epidemiology and Clinical Applications & Clinical Director, NEI.
Igal Gery, PhD; Experimental Immunology Section Head, Laboratory of Immunology, NEI.
Robyn Guymer, MBBS, PhD, FRANZCO; Macular Research Unit Head and Deputy Director, Centre for Eye Research Australia.
Tom Hohman, PhD; Vice President, Retina Translation Medicine, Allergan, Inc.
Michael Klein, MD; Clinician, Macular Degeneration Center, OHSU Casey Eye Institute.
*Richard Lee, BMedSci, BMBS, MRCS, MRCOphth, PhD. Lead for Experimental Medicine, Inflammation and Immunotherapy Theme, NIHR Biomedical Research Centre, UK*
Philip Luthert, BSc, MBBS, FRCP, FRCPath, FRCOphth; Director, Institute of Ophthalmology & Head, Division of Pathology, UCL.
Matthew McMahon, PhD; Senior Advisor for Translational Research, NEI.
Loré Anne McNicol, PhD; Director, Division of Extramural Research, NEI.
Sheldon Miller, PhD Scientific Director & Section on Epithelial and Retinal Physiology and Disease Head, NEI.
Meghan Mott, MS, PhD; Science & Technology Policy Fellow, Institute of Medicine of the National Academies
**Robert Nussenblatt, MD, MPH; Chief & Clinical Immunology Section Head, Laboratory of Immunology, NEI.
Praveen Patel, MA, MB BChir, FRCOphth, MD(Res), Consultant Ophthalmologist & Medical Retina Clinical Trials Lead Consultant, NIHR Biomedical Research Centre, Moorfields Eye Hospital.
Gyan Prakash, PhD, MBA; Associate Director, Office of International Programs, NEI.
H. Nida Sen, MD, MHSc; Staff Clinician & Director, Uveitis and Ocular Immunology Fellowship Program, NEI.
Paul Sieving, MD, PhD; Director of NEI.
Adnan Tufail, MBBS, MD, FRCOphth, Consultant Ophthalmologist, Moorfields Eye Hospital. Theme Lead-Translational Research in AMD, NIHR Biomedical Research Centre.
Howard Weiner, MD; Co-Director, The Center for Neurologic Diseases & Chief, Division of Multiple Sclerosis and Neuro-Immunology, Department of Neurology, Brigham and Women’s Hospital.
*Moderating session. **Attending via Teleconference
Key Topics Identified:
Techniques which could be used to interrogate the disease pathogenesis in models and in man
Better use of post-mortem pathology material with targeting of AMD patients and controls
How to identify the antigens, specific to AMD, targeted by the immune system
Identify the differences in the immunology of anatomical compartments relevant to AMD e.g. neural retina, sub-retinal space, retinal pigment epithelium (RPE), sub-RPE, choroidal space
Explore the interaction between ocular senescence and immunosenescence in relation to AMD
Improved phenotypic stratification of age-related macular changes to aid patient selection for biomarker collection and clinical trials
Investigate the link between AMD and the human microbiome both intestinal and extra-intestinal
Study potential therapeutic mechanisms to modify the putative immunological dysfunction in AMD
1. Investigative Techniques and Strategies
Examine the effects in epidemiological natural history studies of both systemic medications e.g. metformin and aspirin, and systemic diseases e.g. rheumatoid arthritis and obesity
Investigate the immune response of individuals with AMD to age-matched controls – initially a cross-sectional observation of blood titers then later a measure of the longitudinal response to a antigenic insult e.g. standard preplanned vaccinations for the older age group (pneumococcus or herpes zoster)
Use new antigenic array techniques to perform the above, and to interrogate the laboratory models of disease
RPE animal models - developing an animal model focusing on RPE is crucial as RPE has multiple roles in AMD: phagocytic activity decline, cytokines promoting neovascularization, etc.
Develop models using induced pluripotent stem cells (iPS) transformed into RPE cultures with a simulated natural environment to allow more normal cellular activity and responses
iPS-derived RPE from young skin is intrinsically different from that of iPS from old skin. Also these two RPEs differ in their ability to bind complement.
Use established aging biomarkers as stains in aged RPE vs young RPE. If there is a difference could these markers be used to further phenotype AMD patients?
Use proposed new clinical imaging techniques including labelling of immune cell types and ultra-high resolution optical coherence tomography (OCT) of retinal structures including microglia.
Employ genetically engineered animal models where immune cells fluoresce and correlate immune response in aging skin vs aging eye.
New markers have been found that specifically target microglia (versus monocytes) or utilize Annexin A5 as a marker of apoptotic cells in vivo in the eye.
Interrogate drusen by
Adding them to new iPS derived RPE cultures
Collect fresh drusen from post-mortem samples and examining contents for e.g. macrophages
2. Immunosenescence and Ocular Senescence
Determine the etiological balance in AMD between the aging immune system and the senescence of ocular cells themselves – Is an AMD eye more senescent than an age matched control eye?
Previous studies have linked cataract formation, but not AMD, to mortality so it has not been thought there is a direct link between AMD and physiologic markers of senescence
Possible biomarkers to interrogate this could include
Systemic biomarkers of senescence already used in gerontology – for example ß-galactosidase
Complement system markers of dysregulation
Blood vessel caliber
Cytomegalovirus (CMV) serotyping - Is there any evidence for CMV reactivation in AMD? Is CMV latent in retinal tissue? (In AIDS we don’t think CMV is latent in retinal tissue itself)
Can ocular senescence be correlated with CNS senescence e.g. amyloid plaques, microglial function? Studies have been initiated looking for phenotypic associations between AMD and Alzheimer’s
Senescence biomarkers could be measured in a cross-sectional or longitudinal manner in natural history trials, but also may function as stains for histopathological examinations
Once techniques are agreed it will be important to interrogate senescence in the different compartments of the eye e.g. choriocapillaris vs photoreceptor layer
Use proposed clinical phenotypic classifications from the Beckman Group (or a modification of) for future trials
But remember that just as important patient selection may be the immune phenotype elucidated through the biomarkers described already
Small hard drusen may represent an inevitable consequence of ocular senescence with reduced ability to remove waste materials, the discussion as to their immunological importance continues
Some believe they have little significance beyond being a marker of impaired function
Others that they may be protective with decreased rates of AMD progression attributed to either encapsulation of damaging proteins or even recruitment of beneficial immune cells.
Medium and large soft drusen may represent the clinically visible portion of widespread RPE level dysfunction and basal laminar deposits. They are likely to represent the major interaction with immune system in AMD.
Other clinically important groups to identify and investigate are
Patients under 50 years old who develop drusen – do they have a different microbiome or markers of ocular or immunosenescence
Patients who are undergoing loss of drusen – is this a danger signal of increased damage and impending atrophy, or does it represent a para-inflammatory like response?
Patients who develop photoreceptor atrophy and lose vision without evidence of drusen (as demonstrated by loss of vision in the control arm of large natural history studies)
Patients with spreading geographic atrophy and a hyper-autofluorescent border– could they respond to immunosuppression?
4. The microbiome and AMD
Collection in a clinical cohort should be along new phenotypic classifications
It would be important to perform both a case-control study comparing AMD patients to age-matched controls, but also to interrogate the microbiome over time as the clinical phenotype changes
Preliminary investigations could include examining the effect of the microbiome on mouse models of AMD – through germ free techniques and changing the established microbiome with antibiotics
The microbiome of the eye itself should not be forgotten, although it is expected to play a smaller part than the intestinal microbiome, it can be linked with histopathological studies
The technique of microbiome sampling (fecal collection vs intestinal wall scraping) should be examined to ensure high patient uptake with maximum scientific validity according to the literature
5. Therapeutic Interventions: Oral tolerance
The aim of AMD treatment should be to intervene early and prevent the progression to the advanced changes of geographic atrophy or choroidal neovascular membrane formation
Induced tolerance is an attractive proposition with the ability to treat long-term with a safe compound that even with 10-30% efficacy could have major public health implications
In animal models of parainflammation (atherosclerosis and arthritis), mucosal oral tolerance has been successful.
In human trials, oral tolerance was seen to suppress immune reactions in studies related to peanut allergy, diabetes, and arthritis. However, oral tolerance has well documented failures highlighting our relative naivety around the immune mechanisms involved
Oral vs nasal spray therapy - oral was preferred due to its ability to induce TGF-ß producing cells primarily as opposed to nasal spray which can induce IL-10 cells
“Tolerance” in the literature has come to mean both induction of T-regulatory cells (T-regs) and also direct inhibition of antigen reactive cells – the tolerance discussed here involves induction of T-regs
Ideally a large trial would be designed with the ability to act both as a treatment trial but almost more importantly a natural history trial that could investigate several outcomes listed above; validity of phenotypic classifications, microbiome studies, new imaging techniques, senescence biomarkers, antigenic arrays and pathological studies when available.
Scientific justification for a larger trial could be established with a smaller proof of concept trial restricted to those patients with an immune phenotype most likely to respond to oral tolerance (chosen by array testing of their response to retinal antigens) – it is thought this group would likely include patients with medium to large soft drusen. As such the power of a smaller trial could be enhanced by including quantitative measures such as change in drusen volume (calculated by OCT).
Questions and Problems to be addressed include
Which antigen should be used?
Should multiple antigens including S-Antigen and Beta-Amyloid be used? If so would a factorial design for the trial be required?
Recruitment of some of the patient groups listed before will be a challenge
Which outcome measures can be used in patients with very early disease – functional testing, ultra-high resolution OCT proposed
The compartment being targeted by retinal antigen oral tolerance is anatomically distinct from the RPE/Bruch’s complex
The therapy relies upon the bystander effect from induced regulatory immune cells trafficking through the eye and releasing anti-inflammatory cytokines intended for damaged photoreceptors but acting on the underlying RPE/Bruch’s complex
Although oral tolerance was the main therapeutic intervention discussed, others raised by the panel were:
Anti-complement therapy – the complement pathway appears directly relevant to the development and progression of AMD but is not specific to AMD. Does the senescent profile of a cell affect the ability to secrete regulatory complement factors to protect? Given the ubiquity of complement, from a therapeutic and prevention standpoint it will be difficult to challenge subjects with anti-complement therapy.
Targeting drusen directly possibly with a drug such as being attempted with the amyloid plaques of Alzheimer’s disease or with laser application – this has been shown to effectively remove drusen in late AMD but did not affect the rate of geographic atrophy development when compared to the fellow control eye.
The NEI’s audacious goal the Intersection of Aging & Biological Mechanisms of Eye Disease has been addressed with our discussions of role of the immune system in AMD. It was agreed to move forward with plans for a proof of concept clinical trial investigating oral tolerance induction in AMD patients identified through clinical and immune phenotyping.