Anti-apolipoprotein A-1 (ApoA-1) and anti-immunodominant F3L1 peptide positivity correlated with greater disease activity in systemic lupus erythematosus (SLE), according to study data results published in Rheumatology.
The Swiss SLE Cohort Study consecutively enrolled 176 patients who satisfied at least 4 American College of Rheumatology SLE criteria. Serum samples were collected at baseline; follow-up included an annual collection from 354 distinct biologic samples. Disease activity was captured with the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI). Patient interviews were conducted to assess other clinical characteristics, including treatment history and anamnestic cardiovascular events. Serum samples were tested for the presence of anti-ApoA-1 immunoglobin G (IgG), anti-F3L1 IgG, anti-double-stranded DNA (anti-dsDNA) IgG, and anti-phospholipid antibodies.
Of 176 patients, 85% were women and 78% were white. Mean (standard deviation) age at inclusion was 44 years (15 years; age range, 17-85 years). Anti-ApoA-1 IgG positivity was observed in 76 (43%) of the 176 patients. Both anti-ApoA-1 and anti-F3L1 IgG positivity were associated with higher SLEDAI (P =.028 and P =.025, respectively), driven largely by concomitant dsDNA IgG positivity and low complement. In multiple regression analyses adjusted for anti-dsDNA, the contribution of anti-ApoA-1 and anti-F3L1 antibodies to SLEDAI lost significance.
Variations in time of anti-ApoA-1 IgG levels between annual samples were positively correlated with variations in anti-dsDNA IgG and inversely correlated with variations in C3 levels (P <.001). Similarly, longitudinal anti-F3L1 IgG levels correlated positively with anti-dsDNA and negatively with C3 and C4 (P <.001). Anti-F3L1 was found to dose-dependently inhibit anti-ApoA-1 reactivity. However, no cross-reactivity was observed between anti-ApoA-1 and anti-dsDNA IgG. A significantly higher frequency of anti-ApoA-1 positivity was observed among patients receiving >10 mg/d prednisone compared with patients receiving <10 mg/d (P =.04). Although cardiovascular events occurred frequently in patients in the study cohort, the events were not correlated with anti-ApoA-1 or anti-F3L1 IgG positivity.
These data suggest that ApoA-1 and F3L1 may be important biomarkers for disease activity in SLE. As the number of patients providing serum samples decreased during follow-up, results may be at risk for selection bias. Despite this, investigators endorsed routine monitoring of anti-ApoA-1 IgG as a means of monitoring SLE.
Nigolian H, Ribi C, Courvoisier DS, et al. Anti-apolipoprotein A-1 autoantibodies correlate with disease activity in systemic lupus erythematosus [published online August 3, 2019]. Rheumatology (Oxford). doi:10.1093/rheumatology/kez306