VAV1 regulates experimental autoimmune arthritis and is associated with anti-CCP negative rheumatoid arthritis.

Rheumatoid arthritis (RA) patients can be stratified into two subgroups defined by the presence or absence of antibodies against citrullinated circular peptides (anti-CCP) with most of the genetic association found in anti-CCP positive RA. Here we addressed the role of VAV1, previously associated to multiple sclerosis (MS), in the pathogenesis of RA in experimental models and in a genetic association study. Experimental arthritis triggered by pristane or collagen type II was induced in DA rats and in the DA.BN-R25 congenic line that carries a polymorphism in Vav1. Difference in arthritis severity was observed only after immunization with pristane. In a case-control study, 34 SNPs from VAV1 locus were analyzed by Immunochip genotyping in 11475 RA patients (7573 anti-CCP positive and 3902 negative) and 15,870 controls in six cohorts of European Caucasians. A combination of the previous MS-associated haplotype and two additional SNPs was associated with anti-CCP negative RA (alleles G-G-A-A of rs682626-rs2546133-rs2617822-rs12979659, OR=1.13, P=1.27 × 10-5). The same markers also contributed to activity of RA at baseline with the strongest association in the anti-CCP negative group for the rs682626-rs12979659 G-A haplotype (ß=-0.283, P=0.0048). Our study suggests a role for VAV1 and T-cell signaling in the pathology of anti-CCP-negative RA.

The multiple sclerosis risk gene IL22RA2 contributes to a more severe murine autoimmune neuroinflammation.

Single-nucleotide polymorphisms close to IL22RA2, coding for the soluble interleukin (IL)-22-binding protein (IL-22BP), are strongly and reproducibly associated with multiple sclerosis (MS), but there is little data on how this molecule may affect neuroinflammation. Here, we have studied the mouse ortholog in C57BL/6 wild-type and Il22ra2-deficient mice in the context of experimental autoimmune encephalomyelitis (myelin oligodendrocyte glycoprotein-EAE). In wild-type mice, we demonstrated changes in the levels of transcripts for IL-22, the signaling IL-22 receptor and IL-22BP in lymphoid tissues at the time of T-cell priming and in the inflamed central nervous system (CNS). Because IL-22BP is known to antagonize IL-22 signaling, a primarily pro-inflammatory cytokine, we hypothesized that the Il22ra2-deficient mice would have more severe EAE. Paradoxically, the knockout mice displayed a less severe disease course, less demyelination and less infiltration of immune cells in the CNS. The most straightforward interpretation of our findings is that lack of IL-22BP leads to a higher availability of IL-22, which in the case of CNS inflammation, surprisingly acts in a protective fashion. Thus, deletion of the ortholog of the MS risk gene Il22ra2 in mice has beneficial effects on EAE, which may be considered in new therapeutic strategies for treating neuroinflammation.

Anti-MOG antibodies are under polygenic regulation with the most significant control coming from the C-type lectin-like gene locus.

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system that is genetically complex. There is evidence supporting a role of myelin oligodendrocyte glycoprotein (MOG) humoral immunity in MS. We aimed to determine the genetic regulation of anti-MOG antibodies and their involvement in disease, by using MOG-induced experimental autoimmune encephalomyelitis (EAE) in rat, an animal model that closely mimics human MS. We show polygenic regulation of anti-MOG antibodies in two backcross populations, including a major genetic determinant for antibody expression on chromosome 4, Amig3. We fine-mapped the region to 539 kilobases (kb) consisting of a complex of seven C-type lectin receptor genes (Dcir4, Dcir3, Dcir2, Dcir1, Dcar1, Mcl and Mincle) that was captured in the APLEC congenic strain. We confirmed that Amig3 regulates anti-MOG antibody levels in MOG-EAE, and further showed that immune reactions during initiation of EAE were skewed toward increased numbers of B cells in the EAE-protected APLEC strain, together with higher anti-MOG IgG1 and lower IgG2b levels. Taken together, our data demonstrated complex regulation of the antibody response during EAE and that skewing the antibody response toward Th2 contributed to protection from EAE.