What made you start researching Sjogren’s?
In 2008 upon the deciphering of the human salivary proteome, we did a collaborative study with Dr. Gil Omenn at University of Michigan to compare the saliva and plasma proteome (1). Amongst the many intriguing findings is the linear distribution of immunoglobulins between plasma and saliva. Regardless of isotype, subtype of immunoglobulins, distribution between saliva and plasma exhibited a distribute R2 >0.9, comparing a Southern Californian (saliva) and Michigan (plasma) population. Figure 1 showed the linear immunoglobulin distributions in the saliva with plasma.
We hypothesized that autoantibodies anti-SSA/Ro and anti-SSB/La to the chronic autoimmune disease, Sjögren’s , in the serum of these patients would be detectable in saliva. Using ELISA and Luminex based platforms, no Ro nor La salivary signals were discernable. It is well known that detection of antibodies in saliva has not been consistent and met with technical challenges using current technologies of ELISA and bead-based Luminex technologies (2). The only technology that can detect Ro and La in saliva of Sjögren’s patients is an electrochemical platform EFIRM (electric field induced released and measurement) developed by the UCLA lab for salivaomics research. EFIRM discriminatorily detected and stratified the Ro and La signals in saliva of Sjögren’s patients.
Your project, “EFIRM Liquid Biopsy for Early Detection of Sjögren’s and Sicca Patients,” was the Foundation 2020-2021 High Impact Research Grant. What were some of the key points that made this project so exciting?
Using the novel diagnostic platform, electric field-induced release and measurement (EFIRM), our research group demonstrated that the EFIRM-based immunoassay can quantify SARS-CoV-2 saliva antibodies that are 100-fold less compared to plasma antibodies in paired samples. With the support from Sjögren’s Foundation 2020-2021 High Impact Research Grant, we demonstrated EFIRM to directly detect and quantify salivary SSA/Ro-52 autoantibodies Sjögren’s patients. Specifically, 94% (32/34) of Sjögren’s patients with 85% (29/34) seropositivity and 60% (21/35) of seronegative sicca patients had EFIRM-detectable SSA/Ro-52 autoantibodies in saliva. Most importantly, our findings lead to the discovery of the “autoimmune-sicca” patient cohort who are anti-SSA/Ro saliva positive and serum negative. Salivary SSA/Ro-52 autoantibodies significantly discriminated patients with Sjögren’s or autoimmune-sicca from healthy subjects with an area under the ROC curve, 0.91 with 95% confidence interval of 0.86–0.96. To our knowledge, this study is the first saliva immunoassay with clinical sensitivity to quantitatively detect SSA/Ro-52 autoantibodies in the saliva of 80% (4/5) Sjögren’s and 60% (21/35) sicca seronegative patients.
Were you happy with the results during your one-year grant period?
During the one-year grant period, we developed and clinically verified the performance of the saliva anti-SSA/Ro-52 immunoassay. It can impactfully serve as a screening test to distinguish Sjögren’s and autoimmune-sicca from non-autoimmune sicca and healthy. The proposed saliva SSA/Ro-52 immunoassay can benefit seronegative Sjögren’s and autoimmune-sicca patients in obtaining accurate diagnosis and appropriate treatment to improve outcome. The novel EFIRM platform addresses an unmet clinical need by non-invasively quantify saliva anti-SSA/Ro-52, permitting early detection in sicca and seronegative patients while minimizes healthcare burden.
Have you continued this research since the completion of this study?
Our lab continued on with Sjögren’s research under the support of the National Institutes of Health. We aim to validate the EFIRM immunoassay in additional clinical cohorts and further the understanding of the pathogenesis of Sjögren’s to permit timely therapeutic intervention early in the disease course, before irreversible destruction of the salivary gland by local autoimmunity.
What current research in the field of Sjögren’s do you find most exciting?
The current investigations suggest that autoimmune-sicca can be considered a localized Sjögren’s, whereas when anti-SSA/Ro autoantibody starts to appear in serum, systemic disease ensues. Additional findings suggested salivary anti-Ro52/SSA IgA1 to correlate to salivary gland biopsy focus scores. IgA exists in two isotypes, IgA1 and IgA2, and IgA1 can further be subdivided into monomeric (mIgA1) and polymeric (pIgA1) subclasses. Human serum IgA1 mostly exists as monomeric form (85-90%) whereas saliva secretory IgA1 are predominantly polymeric form (90-95%) secreted by polymeric Ig receptor (pIgR). In addition to structural differences, mIgA1 and pIgA1 also exhibit differential immunoregulatory roles as immune suppressor and inducer respectively. We hypothesize that salivary pIgA1 anti-Ro52/SSA in Sjögren’s patients is associated with salivary gland tissue destruction, measured by biopsy focus score. The regulatory roles of monomeric IgA1 and polymeric IgA1 may contribute to heterogenous clinical presentations of salivary gland destruction in autoimmune-sicca and Sjögren’s patients. We are interested to investigate whether or not Sjögren’s and autoimmune-sicca is a disease continuum. Early detection of SSA/Ro autoantibodies in saliva and further the understanding of the pathogenesis of primary Sjögren’s might enable earlier detection and development of new therapeutics for autoimmune-sicca and Sjögren’s autoimmunity.
1. Yan W, Apweiler R, Balgley BM, Boontheung P, Bundy JL, Cargile BJ, Cole S, Fang X, Gonzalez-Begne M, Griffin TJ, Hagen F, Hu S, Wolinsky LE, Lee CS, Malamud D, Melvin JE, Menon R, Mueller M, Qiao R, Rhodus NL, Sevinsky JR, States D, Stephenson JL, Than S, Yates JR, Yu W, Xie H, Xie Y, Omenn GS, Loo JA, Wong DT. Systematic comparison of the human saliva and plasma proteomes. Proteomics Clin Appl. 2009;3(1):116-34. Epub 2009/11/10. doi: 10.1002/prca.200800140. PubMed PMID: 19898684; PMCID: PMC2773554.
2. Mitchell JS, Lowe TE. Matrix effects on an antigen immobilized format for competitive enzyme immunoassay of salivary testosterone. Journal Of Immunological Methods. 2009;349(1-2):61-6. Epub 2009/08/08. doi: 10.1016/j.jim.2009.07.012. PubMed PMID: 19660465.