Cytosolic phospholipase A2α–deficient mice are resistant to experimental autoimmune encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE), a Th1-mediated inflammatory disease of the central nervous system (CNS), is a model of human multiple sclerosis. Cytosolic phospholipase A2α (cPLA2α), which initiates production of prostaglandins, leukotrienes, and platelet-activating factor, is present in EAE lesions. Using myelin oligodendrocyte glycoprotein (MOG) immunization, as well as an adoptive transfer model, we showed that cPLA2α−/− mice are resistant to EAE. Histologic examination of the CNS from MOG-immunized mice revealed extensive inflammatory lesions in the cPLA2α+/− mice, whereas the lesions in cPLA2α−/− mice were reduced greatly or completely absent. MOG-specific T cells generated from WT mice induced less severe EAE in cPLA2α−/− mice compared with cPLA2α+/− mice, which indicates that cPLA2α plays a role in the effector phase of EAE. Additionally, MOG-specific T cells from cPLA2α−/− mice, transferred into WT mice, induced EAE with delayed onset and lower severity compared with EAE that was induced by control cells; this indicates that cPLA2α also plays a role in the induction phase of EAE. MOG-specific T cells from cPLA2α−/− mice were deficient in production of Th1-type cytokines. Consistent with this deficiency, in vivo administration of IL-12 rendered cPLA2α−/− mice susceptible to EAE. Our data indicate that cPLA2α plays an important role in EAE development and facilitates differentiation of T cells toward the Th1 phenotype

Human endogenous retrovirus protein activates innate immunity and promotes experimental allergic encephalomyelitis in mice.

International audienceMultiple sclerosis (MS) is a complex multifactorial disease of the central nervous system (CNS) for which animal models have mainly addressed downstream immunopathology but not potential inducers of autoimmunity. In the absence of a pathogen known to cause neuroinflammation in MS, Mycobacterial lysate is commonly used in the form of complete Freund's adjuvant to induce autoimmunity to myelin proteins in Experimental Allergic Encephalomyelitis (EAE), an animal model for MS. The present study demonstrates that a protein from the human endogenous retrovirus HERV-W family (MSRV-Env) can be used instead of mycobacterial lysate to induce autoimmunity and EAE in mice injected with MOG, with typical anti-myelin response and CNS lesions normally seen in this model. MSRV-Env was shown to induce proinflammatory response in human macrophage cells through TLR4 activation pathway. The present results demonstrate a similar activation of murine dendritic cells and show the ability of MSRV-Env to trigger EAE in mice. In previous studies, MSRV-Env protein was reproducibly detected in MS brain lesions within microglia and perivascular macrophages. The present results are therefore likely to provide a model for MS, in which the upstream adjuvant triggering neuroinflammation is the one detected in MS active lesions. This model now allows pre-clinical studies with therapeutic agents targeting this endogenous retroviral protein in MS

Mice lacking Tbk1 activity exhibit immune cell infiltrates in multiple tissues and increased susceptibility to LPS-induced lethality

TBK1 is critical for immunity against microbial pathogens that activate TLR4- and TLR3-dependent signaling pathways. To address the role of TBK1 in inflammation, mice were generated that harbor two copies of a mutant Tbk1 allele. This Tbk1(Delta) allele encodes a truncated Tbk1(Delta) protein that is catalytically inactive and expressed at very low levels. Upon LPS stimulation, macrophages from Tbk1(Delta/Delta) mice produce normal levels of proinflammatory cytokines (e.g., TNF-alpha), but IFN-beta and RANTES expression and IRF3 DNA-binding activity are ablated. Three-month-old Tbk1(Delta/Delta) mice exhibit mononuclear and granulomatous cell infiltrates in multiple organs and inflammatory cell infiltrates in their skin, and they harbor a 2-fold greater amount of circulating monocytes than their Tbk1(+/+) and Tbk1(+/Delta) littermates. Skin from 2-week-old Tbk1(Delta/Delta) mice is characterized by reactive changes, including hyperkeratosis, hyperplasia, necrosis, inflammatory cell infiltrates, and edema. In response to LPS challenge, 3-month-old Tbk1(Delta/Delta) mice die more quickly and in greater numbers than their Tbk1(+/+) and Tbk1(+/Delta) counterparts. This lethality is accompanied by an overproduction of several proinflammatory cytokines in the serum of Tbk1(Delta/Delta) mice, including TNF-alpha, GM-CSF, IL-6, and KC. This overproduction of serum cytokines in Tbk1(Delta/Delta) mice following LPS challenge and their increased susceptibility to LPS-induced lethality may result from the reactions of their larger circulating monocyte compartment and their greater numbers of extravasated immune cells

Histological analysis of cervical spinal cord (mouse #1-1).

<p>A. Microscopic changes in transverse section of spinal cord are shown (100×). Multiple inflammatory foci and some multifocal inflammatory lesions are present in the leptomeninges, around blood vessels in the leptomeninges and white matter, and parenchyma of the white matter (arrows). There is also vacuolation in the white matter that is consistent with edema and demyelination. B. Luxol fast blue stained section of cervical spinal cord (100×). This section is from the same block of tissue as the H&E stained section shown in A. Areas of demyelination are visible within white matter (lighter blue stained areas, in the outer parts of the spinal cord; arrows). C. H&E stained transverse section of thoracic spinal cord (100×). Four multifocal inflammatory lesions are present in the leptomeninges, around blood vessels in the leptomeninges and white matter (box and arrows). There also is vacuolation in the white matter that is consistent with edema and demyelination (box). D. H&E stained section of thoracic spinal cord (400×). Detail of the above slide (boxed area). Two multifocal inflammatory lesions are shown (arrows).</p

Statistical Analysis of EAE-like symptoms after Immunisation with MOG and MSRV-Env complete in C57BL/6 mice.

<p>Data correspond to those illustrated in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0080128#pone-0080128-g004" target="_blank">figure 4C</a>. Time to onset was compared using Wilcoxon's survival test; MMSs were compared using Wilcoxon's non-parametric test; Change in body weight at the end of the study was compared using Student's t-test.</p><p>^* Statistically significant value.</p

EAE mice induced by Env-SU display anti-MOG autoimmunity in splenocytes cultures.

<p>A. γIFN secretion of pooled splenocytes (2 mice for the IFA group and 3 mice for the Env-SU group) of EAE mice assessed by ELISA of culture supernatants 24 h after stimulation. B. Kinetics of γIFN production upon MOG recall on pooled splenocytes of IFA (n = 3) and Env-SU (n = 3) injected EAE mice. IFN-γ secretion is assessed in culture supernatants after 24 h, 48 h and 72 h of incubation. Results are representative of two experiments.</p