Immune analysis of long covid to inform rational choices in diagnostic testing and therapeutics – Working out the Immunology of Long COvid (WILCO) - COV-LT2-0027
Plain English Summary The WILCO cohort ('Working out the Immunology of Long Covid'), both adult and paediatric, is novel in terms of being a large, UK cohort of individuals who were largely non-hospitalised during their acute infections and have here been followed longitudinally and in detail, at the level of symptom profile and immunological parameters. Data from this cohort establish a number of key points. This is a large cohort, many of whom have been persistently unwell with multi-system, multi-organ disease for 3-4 years. Longitudinal analysis shows that most symptoms show little improvement across an interval of more than a year. WILCO participants are indicative of Long Covid (LC) trends nationally and globally insofar as many have lost jobs or changed to part-time work as a consequence of their disability. We were able to identify a number of immune correlates of LC, likely contributing to immunopathogenesis: altered immunoglobulin isotype profiles, altered T cell immunity to spike, altered patterns of autoimmunity and altered B cell plasmablast and natural killer cell subsets. Our findings aid in defining the mechanisms underpinning Long Covid, offer potential directions for therapeutic trials and also for diagnostic tests. Executive Summary Background: During the past 4-years, much has been learnt around the world about Long Covid – the chronic, post-viral sequelae persisting more than 12 weeks and, generally, some years, after COVID-19. It is estimated that there are some 400-million sufferers globally and by Office for National Statistics (ONS) Data, 2-million in the UK. These individuals are unable to regain their baseline health, often suffering disability that makes it impossible to return fully to their former employment. This large, new disease burden has profound implications for the workforce, the NHS, and for healthcare planning and provision. This proposal made the point that this is hypothesised to be an immune/inflammatory-mediated disease process, and that we need immune analysis in order to understand the basis of the condition, design diagnostic tests, and build an understanding of the likely approaches for therapeutic drug trials. The work has gone well. The cohort was termed ‘WILCO’ for ‘Working Out the Immunology of Long Covid’ and we were able to recruit nearly 1000 individuals into the cohort. This is a novel and informative Long Covid study cohort since it comprises people with well-characterised Long Covid symptoms, in many cases affected now for 3-4 years, and with their condition deriving from infections across each of the COVID-19 variant waves: ancestral Wuhan Hu-1 (the 2020-wave), Alpha, Delta, and Omicron. Because the analysis is longitudinal, we have been able to understand the persistence of symptoms, their long-term effects and immune correlates. We have also been able to relate symptoms and immune parameters in the adult cohort to our parallel, paediatric Long Covid cohort. Study aims and methods: Our goal was to work towards development of clear, diagnostic tests through high-granularity immunological analysis for biomarker discovery. Analysis would use peripheral blood samples, the study groups comprising: i) Healthy controls, ii) Individuals who had confirmed COVID-19 with rapid recovery and iii) Individuals who meet the criteria for Long Covid - greater than 12 weeks from the start of acute COVID-19 infection without recovery back to baseline health. iv) We would relate findings in this adult, largely non-hospitalised cohort to an additional cohort - a paediatric cohort recruited through referral to the Paediatric Long Covid clinical service at KCL and the Evelina Hospital. The specific questions to be addressed in the lab using cohort blood samples were as follows: • Analysis of white blood cell immune subsets using an approach termed multi-parameter flow cytometry. That is, measuring the specific profile of lymphocyte subsets contributing to immunity using fluorescently labelled antibodies. We would thus compare immune subsets in people with Long Covid relative to people who made a full recovery from acute infection to investigate perturbations in immune subsets. • In related lab analyses, we would make RNA from blood to analyse the differential programmes driving immune subsets in Long Covid and fully recovered controls • We would correlate disease symptoms with specific patterns of antibody and/or T cell autoimmunity, addressing the hypothesis that the origins of Long Covid may be partly through the ability of the virus to drive an autoimmune condition whereby the immune system erroneously attacks cells in the body. Results and key findings: Since the start of the award we have achieved each of our milestones. A cohort of nearly 1000 was consented and recruited at Imperial College London, detailed symptom and clinical history questionnaires were completed at two longitudinal timepoints, analysed and clustered by machine learning, participants gave blood samples which were used in detailed immunological investigations as described above, and these immune parameters have illuminated understanding of the processes underlying Long Covid, offering potential tests and clues to therapeutic approaches. The initial deliverable was to establish the infrastructure to recruit, build and characterise a UK-based, largely non-hospitalised, Long Covid research cohort and recovered controls, representative of the experience of the majority of Long Covid sufferers. Participants were recruited in response to adverts posted through community newsletters, social media, Long Covid support networks, general and Long Covid clinics. All participants completed a detailed, questionnaire-based symptom history using a validated, published, protocol. In most cases this was done at 2 timepoints separated by 12-18 months. This follow-up comprised a second, expanded questionnaire and additional blood sample...