Background/Purpose:

M-phase phosphoprotein (MPP-1), also termed kinesin interacting protein (KIF20B), is a 210 kDa protein that is highly expressed during cell division. Autoantibodies to MPP-1 were first described in approximately 25% of patients with idiopathic ataxia, but recent studies have indicated that they are also found in systemic lupus erythematosus (SLE). The goals of this study were to determine the frequency of anti-MPP-1 in a local SLE cohort and then identify demographic, clinical, and serologic correlations.

Methods:

Patients fulfilling the American College of Rheumatology (ACR) or Systemic Lupus International Collaborating Clinics (SLICC) Classification Criteria for SLE were enrolled in a local cohort. Demographic, clinical information (disease activity – SLEDAI-2K; damage – SLICC/ACR DI), and sera were collected at time of enrollment. Antibodies to MPP-1 were determined by an addressable laser bead immunoassay (ALBIA) utilizing an in vitro expressed MPP-1 cDNA construct inserted into a GFP vector (Clontech Laboratories Inc., Saint-German-en-Laye, France). ALBIA results were expressed as median florescence units (MFU) and a dilution of greater than or equal to 1:500 MFU was considered highly positive. Univariable and multivariable analysis were performed to determine associations between the prevalence of high positive anti-MPP-1 and demographic (age, sex, race/ethnicity), clinical features (SLEDAI-2K and SLICC/ACR DI total scores and subscales and neurological subscale of the ACR and SLICC Classification Criteria), medications, and other autoantibodies (anti-dsDNA, extractable nuclear antigens, and anti-phospholipid antibodies).

Results:

One hundred and fifty-six SLE patients were included; 89.8% were female with a mean age of 47.5 years (SD 15.8) and disease duration of 13.6 years (SD 11.8). The prevalence of high titre anti-MPP-1 was 14.1% (22/156). Univariable analysis demonstrated that high anti-MPP-1 positivity was associated with a higher total SLEDAI-2K score (Odds Ratio (OR), 1.1 [95% CI 1.0, 1.3]), particularly with the serositis (OR 2.7, [95% CI 1.3, 5.6]) and immunological SLEDAI-2K subscales (OR 1.9, [95% CI 1.3, 2.7]). High anti-MPP-1 positivity was also associated with anti-dsDNA (OR 4.7 [95% CI 1.7, 13.4]) and anti-phosphotidylserine/prothrombin complex (aPS/PT)-IgG (OR 3.2 [95% CI 1.1, 9.9]). In the multivariable analysis, only the serositis (OR 2.5, [95% CI 1.1, 5.7]) and immunological SLEDAI-2K subscales (OR 1.9, [95% CI 1.3, 2.7]) were independently associated with anti-MPP-1 positivity.

Conclusion:

High titer anti-MPP-1 antibodies were relatively common in this SLE cohort (14.1%) and may be associated with greater clinical and serologic SLE disease activity. A larger study is currently underway to more clearly delineate its role as a biomarker in SLE.

« Back to 2018 ACR/ARHP Annual Meeting

ACR Meeting Abstracts - https://acrabstracts.org/abstract/autoantibodies-to-m-phase-phosphoprotein-i-mpp-1-kif20b-in-systemic-lupus-erythematosus/