Background
Cardiovascular disease (CVD) risk is 1.5- to 2-fold higher in people living with HIV (PLWH). The heightened risk persists despite suppression of plasma viremia and control of traditional risk factors, partly due to chronic inflammation. Subcutaneous adipose tissue (SAT) regulates metabolic health, but inflammation and insulin resistance can shift its secretome to a pro-inflammatory, pro-atherogenic state. FCHSD2 is an adapter protein involved in insulin secretion and has been implicated in the pathogenesis of diabetes. B cells have been associated with cardiometabolic disease and are present in SAT
Methods
B cell subsets in the SAT were characterized using single-cell RNA sequencing (CITE-seq) and B cell receptor (BCR) sequencing in a cohort of 91 PLWH and people without HIV (PWoH) with similar traditional CVD risk profiles. Plasmablasts, naïve cells, and memory B cells were compared across metabolic subgroups (diabetic and non-diabetic). The top ten clonal BCRs from PLWH were expressed as recombinant antibodies and tested for reactivity against CMV using ELISA and reactivity against human proteins using a human protein microarray with over 21,000+ unique human proteins (CDI Labs). We verified the specificity of a clonal antibody against FCHSD2 using transient transfection of 293K cells with plasmids expressing FCHSD2 (Figure A).
Results
SAT of diabetic PLWH and PWoH had significantly higher plasmablasts and fewer naïve B cells than non-diabetic PLWH (p<0.01). B cells from PWoH with diabetes had higher expression of genes with regulatory functions, including LGALS1, SPP1, and LNMA. In contrast, B cells from PLWH with and without diabetes expressed higher CD69, CD40, and CXCR4 (all, p<0.0001), consistent with an activated immune response. One of the ten clones was reactive against CMV. Another clone, identified initially as an IgA, was reactive against FCHSD2 (EC50 12.69 ng/ml). Out of 41 PLWH, ten had high titers of anti-FCHSD2 antibodies in plasma, six of which had diabetes (Figure B). Notably, the anti-FCHSD2 clone has undergone somatic hypermutation, resulting in an IgH sequence identity of 93.13% and an IgL sequence identity of 93.55 compared to its original germline sequence.
Conclusions
HIV infection and co-infections are associated with changes in B cells which have implications for cardiometabolic disease. Anti-FCHSD2 autoantibodies highlight a novel autoimmune mechanism in PLWH that links immune dysregulation and metabolic dysfunction, which has implications for CVD.