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Abstract
Background: With the emergence of the global coronavirus pandemic, increasing concerns have been raised about the course of SARS-CoV-2 infection in people with immune-mediated disorders.
Objectives: In this study we aimed to assess the time course of proven SARS-CoV-2 infection, development of humoral immunity with detectable antibodies to the virus and evaluate any changes in antibody titres over time.
Methods: We recruited 114 participants in total who had potential symptoms of Covid-19 infection. Participants were recruited from rheumatology or inflammatory bowel disease (IBD) clinics from their records who attended a London Teaching hospital for care. Ethical Approval was in place for the study. Age- and gender- matched control participants without any underlying rheumatological condition/IBD were recruited as a comparator group. Clinical symptoms for Covid-19 infection were assessed using the Covid-19 Rheumatology Global Alliance assessment criteria (https://rheum-covid.org/). Information about Disease Modifying Anti-Rheumatic Drug (DMARD) drug use was also recorded. Participants’ serum samples were collected for quantitative serological assessment of antibodies to SARS-CoV-2 using the Mologic Enzyme-Linked ImmunoSorbent Assay (ELISA) IgG kit. The optical density values were plotted aganist time using a normalisation as previously described (1). A cut-off above 0 indicated positive serology.
Results: A total of 114 subjects were recruited into the study. Subjects were recruited if they had suspected Covid symptoms. Of the population recruited, the total number subsequently testing positive for SARS-CoV-2 was n=59 (either on serology or PCR). The number of subjects with autoimmune conditions diagnosed with Covid-19 was 32, with 30 subjects being symptomatic (the asymptomatic 2 subjects were excluded from further analyses). Of the 30 symptomatic subjects, the average age was 56, with a female to male ratio of 19:11. The most prevalent diagnoses were RA (30%), Psoriatic Arthritis (16.7%), SLE (10%), sarcoidosis 10%), Ulcerative Colitis (10%), Crohn’s disease (10%), seronegative inflammatory arthritis (6.7%), Sjogren’s (3.3%) and Juvenile Idiopathic Arthritis (3.3%). The majority were on csDMARDs (60%), biologic DMARDs (20%), tacrolimus (3.3%) and the remaining 16.7% were not on DMARDs. Most subjects required treatment in hospital (56.7%), a smaller number required high dependency care (6.7%) and the rest were treated at home (36.6%). The majority required no oxygen (63.3%), with a further 30% requiring oxygen and 6.7% needed more supportive care i.e. CPAP/ventilation. We also had a matched control group (n=29) of subjects who developed SARS-CoV-2 but had no underlying autoimmune conditions. These subjects had a mean age of 55, female: male ratio 18: 11. Of these 31% had home management, 55.2% had ward level treatments and 13.8% had intensive care treatment. Of the controls, 48.3% did not require oxygen, 37.9% needed simple oxygen and 13.8% were on CPAP. A total of 35 subjects from the original study have attended for follow-up visits. Antibody titres for IgG using the Mologic ELISA detection assay were compared at two visits for the control and autoimmune group. Results showed that subjects with autoimmune conditions and those without who developed SARS-CoV-2 showed very similar antibody titres by optical density (OD) (Figure 1) and maintained antibody responses beyond 6 months in most cases.
Conclusion: Serological assays can assist in the understanding of disease severity of SAR-CoV-2 infection. They can be a useful tool for patient surveillance, especially in people who are on immunomodulatory drugs and are being seen in Rheumatology services. Future work is needed to assess the duration and potential protective nature of humoral antibody responses to SARS-CoV-2.
References: [1]Staines HM, Kirwan D, Clark DJ et al. Dynamics of IgG seroconversion and pathophysiology of COVID:19 infections. medRxiv preprint doi: https://doi.org/10.1101/2020.06.07.20124636.
Disclosure of Interests: Kathryn Biddle: None declared, Soraya Koushesh: None declared, Anna Blundell: None declared, David Clark: None declared, Sanjeev Krishna: None declared, Nidhi Sofat Consultant of: Advisory work for Pfizer and Eli Lilly, Grant/research support from: Received grants from Bristol Myers Squibb and Pfizer for Investigator Initiated Studies.