Little is known about mechanisms that drive the development of progressive multiple sclerosis (MS), although inflammatory factors, such as macrophage migration inhibitory factor (MIF), its homolog D-dopachrome tautomerase (D-DT), and their common receptor CD74 may contribute to disease worsening. Our findings demonstrate elevated MIF and D-DT levels in males with progressive disease compared with relapsing-remitting males (RRMS) and female MS subjects, with increased levels of CD74 in females vs. males with high MS disease severity. Furthermore, increased MIF and D-DT levels in males with progressive disease were significantly correlated with the presence of two high-expression promoter polymorphisms located in the gene, a -794CATT microsatellite repeat and a -173 G/C SNP. Conversely, mice lacking MIF or D-DT developed less-severe signs of experimental autoimmune encephalomyelitis, a murine model of MS, thus implicating both homologs as copathogenic contributors. These findings indicate that genetically controlled high MIF expression (and D-DT) promotes MS progression in males, suggesting that these two factors are sex-specific disease modifiers and raising the possibility that aggressive anti-MIF treatment of clinically isolated syndrome or RRMS males with a high-expresser genotype might slow or prevent the onset of progressive MS. Additionally, selective targeting of MIF:CD74 signaling might provide an effective, trackable therapeutic approach for MS subjects of both sexes.

Summary Resistance to antimalarials targeting the folate pathway is widespread. GTP-cyclohydrolase (gch1), the first enzyme in this pathway, exhibits extensive copy number variation (CNV) in parasite isolates from areas with a history of longstanding antifolate use. Increased CN of gch1 is associated with a greater number of point mutations in enzymes targeted by the antifolates, pyrimethamine and sulfadoxine. While these observations suggest that increases in gch1 CN are an adaptation to drug pressure, changes in CN have not been experimentally demonstrated to directly alter drug susceptibility. To determine if changes in gch1 expression alone modify pyrimethamine sensitivity, we manipulated gch1 CN in several parasite lines to test the effect on drug sensitivity. We report that increases in gch1 CN alter pyrimethamine resistance in most parasites lines. However we find evidence of a detrimental effect of very high levels of gch1 overexpression in parasite lines with high endogenous levels of gch1 expression, revealing the importance of maintaining balance in the folate pathway and implicating changes in gch1 expression in preserving proper metabolic flux. This work expands our understanding of parasite adaptation to drug pressure and provides a possible mechanism for how specific mutations become fixed within parasite populations.

Plasmodium species produce an ortholog of the cytokine macrophage migration inhibitory factor, PMIF, which modulates the host inflammatory response to malaria. Using a novel RNA replicon-based vaccine, we show the impact of PMIF immunoneutralization on the host response and observed improved control of liver and blood-stage Plasmodium infection, and complete protection from re-infection. Vaccination against PMIF delayed blood-stage patency after sporozoite infection, reduced the expression of the Th1-associated inflammatory markers TNF-α, IL-12, and IFN-γ during blood-stage infection, augmented Tfh cell and germinal center responses, increased anti-Plasmodium antibody titers, and enhanced the differentiation of antigen-experienced memory CD4 T cells and liver-resident CD8 T cells. Protection from re-infection was recapitulated by the adoptive transfer of CD8 or CD4 T cells from PMIF RNA immunized hosts. Parasite MIF inhibition may be a useful approach to promote immunity to Plasmodium and potentially other parasite genera that produce MIF orthologous proteins.

Sphingosine-1-phosphate (S1P) is an anabolic clastokine. SPHK is the rate-limiting enzyme in S1P production and has two isoforms. To evaluate the roles of SPHK1 and SPHK2 in bone, we examined the skeletal phenotype of mice with selective deletion of SPHK1 in osteoclasts (SPHK1-Oc -/-) and mice in which the SPHK2 gene was deleted in all tissues (SPHK2 -/-). SPHK1-Oc -/- had normal bone mass. By contrast, SPHK2 -/- female mice had a 14% lower spinal BMD (p<0.01) and males a 22% lower BMD at the same site (p<0.001). SPHK2 -/- and control mice were subsequently treated either with daily PTH(1-34) or vehicle for 29 days. The response to PTH was significantly attenuated in the SPHK2 -/-mice. The mean femoral BV/TV increased by 24.8% in the PTH-treated female control animals vs 10.6% in the vehicle-treated female controls (p <0.01). In contrast, in the SPHK2 -/- female mice the difference in femoral trabecular BV/TV at the end of treatment was not significant (20.5 vs.13.3%, PTH vs. vehicle, p = NS). The anabolic response to PTH was significantly attenuated in the spine of male SPHK2 -/- mice (29.7% vs. 23.1%, PTH vs. vehicle, in controls, p <0.05; 26.9% vs. 19.5% PTH vs. vehicle in SPHK2 -/- mice, p = NS). The spine responded normally in the SPHK2 -/- female mice. Interestingly, suppression of Sost was blunted in the SPHK2 -/- mice when those animals were treated with an anabolic PTH regimen. We conclude that SPHK2 has an important role in mediating both normal bone remodeling and the anabolic response to PTH.

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