Study of the Viral Load and Humoral and Cellular B and T Responses in Patients With Rheumatoid Arthritis and Spondyloarthritis Under Immunosuppressive Treatments

Rheumatoid arthritis (RA) and spondyloarthritis (SPA) are the two most common chronic inflammatory rheumatic diseases, with a prevalence of 0.5-1% for RA and about 0.35% for SPA. Many studies have described an increased risk of serious infectious diseases directly associated with increased morbidity and mortality among those patients. This increased risk (frequency and severity) results from the disease itself, especially if the rheumatism is not controlled with high disease activity, but also due to the immunosuppressive treatments used to treat these patients. The risk of infection is measured by the Incidence Rate (IR) corresponding to the number of events (infections) per 100 patients/years of follow-up. This risk is accepted as comparable between patients with SpA or RA and ranges from 22 to 34/100 patient-years, depending on the studies, for patients on biologics. The risk of infection is higher for patients on biotherapy than for patients on Disease Modifying Anti-Rheumatic Drugs (DMARDs - mainly Methotrexate) and the combination of corticosteroid therapy with the biotherapies further increases this risk of infection. Lung and upper respiratory tract infections are the most common infections observed under biotherapy. The risk of infection may be different depending on the biotherapy considered. Moreover, the vaccine response is also highly variable depending on the biotherapy, treatments with Rituximab, methotrexate and abatacept being those interfering the most with the quality of the vaccine response. The working hypothesis is therefore that certain immunosuppressive treatments used in these inflammatory rheumatic conditions may interfere with the humoral and/or cellular anti-SarS-Cov-2 immune response.

Since December 2019, the first SARS-Cov-2 (Severe acute respiratory coronavirus 2 syndrome) infections have been described in Wuhan province in China. In April 2020, 1,824,950 people were officially infected in 193 countries worldwide with 112,510 deaths reported (Agence France Presse and World Health Organization; 13 April 2020). To date, the investigators have a limited amount of data concerning the seroconversion of infected subjects, the protective or non-protective nature of the specific antibodies generated, and the duration of protection. No data have been generated on the specific B and T responses of SarS-Cov-2. In addition, the few available data in the literature on SarS-Cov-2 only concern the general population, not exposed to immunosuppressive treatments.

However, major questions are currently unanswered for patients on immunosuppressive treatments: Are they excreting the virus for longer periods of time? How long can this viral excretion be measured in the upper airways and in the stool? Do they develop a humoral and cellular immune response similar to the general population? Accurate knowledge of the dynamics of the virus and the immune response induced will be essential for the development of strategies for antiviral treatment, vaccination protocols and for the epidemiological control of Covid-19.