Screening for Neoehrlichia mikurensis and other emerging tick-borne pathogens in Swedish patients with systemic lupus erythematosus receiving B-cell-targeted therapies

The management of moderate to severe systemic lupus erythematosus (SLE) has advanced considerably with the introduction of B-cell-targeted therapies. Several emerging tick-borne diseases (eTBDs) have gained increasing attention as causes of febrile illness with potentially serious complications in predominantly immunocompromised, B-cell-depleted individuals. Since the occurrence of eTBDs remains insufficiently studied in SLE, we aimed to determine whether such infections remain undetected among patients living in a tick-endemic region of Southeastern Sweden. Biobanked sera (n = 143) collected during 2015–2024 from 48 SLE patients receiving rituximab or belimumab in Region Östergötland were included. As comparators, samples from patients with quiescent disease on hydroxychloroquine treatment only (n = 50) were analysed. All samples were investigated by real-time polymerase chain reaction assays for the presence of the eTBD pathogens Neoehrlichia mikurensis, Borrelia burgdorferi sensu lato, Borrelia miyamotoi, Anaplasma phagocytophilum, Spiroplasma ixodetis, and Babesia spp. No pathogen-specific DNA for the examined eTBDs was detected in serum samples from the included patients. Evidence suggests that B-cell-targeted therapies may raise eTBD risk; however, none of the individuals with SLE included herein was found to be infected, despite the documented presence of these pathogens in Southeastern Sweden. Our findings contrast with those from Norwegian immunocompromised patients, but are in line with data from the Danish nationwide Rheumatological Database, including patients with arthritis receiving tumour necrosis factor inhibitors. Hypothetically, higher doses of glucocorticoids impair B-cell function and increase the risk of eTBD further. Nevertheless, routine eTBD screening of patients with SLE in Southeastern Sweden is not supported by our data.