Josée Poirier

Preferential recruitment of interferon-γ-expressing TH17 cells in multiple sclerosis

There is substantial evidence supporting the role of interferon (IFN)‐γ–producing T helper (TH) 1 and interleukin (IL)‐17–expressing TH17 lymphocytes in multiple sclerosis (MS) and its animal model, experimental allergic encephalomyelitis (EAE). However, to date little is known about the potential cooperative interplay between these 2 cytokines. In the current study, we sought to evaluate the frequency of IFN‐γ–expressing TH17 lymphocytes in MS and EAE, and study their recruitment into the central nervous system (CNS).

Location score and haplotype analyses of the locus for autosomal recessive spastic ataxia of Charlevoix-Saguenay, in chromosome region 13q11.

Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) is a clinically homogeneous form of early-onset familial spastic ataxia with prominent myelinated retinal nerve fibers. More than 300 patients have been identified, and most of their families originated in the Charlevoix-Saguenay region of northeastern Quebec, where the carrier prevalence has been estimated to be 1/22. Consistent with the hypothesis of a founder effect, we observed excess shared homozygosity at 13q11, among patients in a genomewide scan of 12 families. Analysis of 19 pedigrees demonstrated very tight linkage between the ARSACS locus and an intragenic polymorphism of the gamma-sarcoglycan (SGCG) gene, but genomic DNA sequence analysis of all eight exons of SGCG revealed no disease-causing mutation. On the basis of haplotypes composed of seven marker loci that spanned 11.1 cM, the most likely position of the ARSACS locus was 0.42 cM distal to the SGCG polymorphism. Two groups of ARSACS-associated haplotypes were identified: a large group that carries a common SGCG allele and a small group that carries a rare SGCG allele. The haplotype groups do not appear to be closely related. Therefore, although chromosomes within each haplotype group may harbor a single ARSACS mutation identical by descent, the two mutations could have independent origins.

Melanoma cell adhesion molecule identifies encephalitogenic T lymphocytes and promotes their recruitment to the central nervous system.

In multiple sclerosis, encephalitogenic CD4(+) lymphocytes require adhesion molecules to accumulate into central nervous system inflammatory lesions. Using proteomic techniques, we identified expression of melanoma cell adhesion molecule (MCAM) on a subset of human effector memory CD4(+) lymphocytes and on human blood-brain barrier endothelium. Herein, we demonstrate that MCAM is a stable surface marker that refines the identification of interleukin 17(+), interleukin 22(+), RAR-related orphan receptor γ and interleukin 23 receptor(+) cells within the CD161(+)CCR6(+) subset of memory CD4(+) lymphocytes. We also show that MCAM(+) lymphocytes express significantly more granulocyte/macrophage colony stimulating factor and granzyme B than MCAM(-) lymphocytes. Furthermore, the proportion of MCAM(+) CD4(+) lymphocytes is significantly increased in the blood and in the central nervous system of patients with multiple sclerosis and experimental autoimmune encephalomyelitis animals compared with healthy controls or other neurological diseases, and MCAM expression is upregulated at the blood-brain barrier within inflammatory lesions. Moreover, blockade of MCAM or depletion of MCAM(+) CD4(+) T lymphocytes both restrict the migration of T(H)17 lymphocytes across blood-brain barrier endothelial cells and decrease the severity of experimental autoimmune encephalomyelitis. Our findings indicate that MCAM could serve as a potential biomarker for multiple sclerosis and represents a valuable target for the treatment of neuroinflammatory conditions.

Central nervous system recruitment of effector memory CD8+ T lymphocytes during neuroinflammation is dependent on α4 integrin

Abstract Clonally expanded CD8+ T lymphocytes are present in multiple sclerosis lesions, as well as in the cerebrospinal fluid of patients with multiple sclerosis. In experimental autoimmune encephalomyelitis, CD8+ T lymphocytes are found in spinal cord and brainstem lesions. However, the exact phenotype of central nervous system-infiltrating CD8+ T lymphocytes and the mechanism by which these cells cross the blood–brain barrier remain largely unknown. Using cerebrospinal fluid from patients with multiple sclerosis, spinal cord from experimental autoimmune encephalomyelitis and coronavirus-induced encephalitis, we demonstrate that central nervous system-infiltrating CD8+ T lymphocytes are mostly of the effector memory phenotype (CD62L− CCR7− granzymeBhi). We further show that purified human effector memory CD8+ T lymphocytes transmigrate more readily across blood-brain barrier-endothelial cells than non-effector memory CD8+ T lymphocytes, and that blood-brain barrier endothelium promotes the selective recruitment of effector memory CD8+ T lymphocytes. Furthermore, we provide evidence for the recruitment of interferon-γ- and interleukin-17-secreting CD8+ T lymphocytes by human and mouse blood-brain barrier endothelium. Finally, we show that in vitro migration of CD8+ T lymphocytes across blood-brain barrier-endothelial cells is dependent on α4 integrin, but independent of intercellular adhesion molecule-1/leucocyte function-associated antigen-1, activated leucocyte cell adhesion molecule/CD6 and the chemokine monocyte chemotactic protein-1/CCL2. We also demonstrate that in vivo neutralization of very late antigen-4 restricts central nervous system infiltration of CD8+ T lymphocytes in active immunization and adoptive transfer experimental autoimmune encephalomyelitis, and in coronavirus-induced encephalitis. Our study thus demonstrates an active role of the blood-brain barrier in the recruitment of effector memory CD8+ T lymphocytes to the CNS compartment and defines α4 integrin as a major contributor of CD8+ T lymphocyte entry into the brain.

A novel locus for idiopathic generalized epilepsy in French-Canadian families maps to 10p11.

Idiopathic generalized epilepsy (IGE) has evidence of a strong genetic etiology. We conducted genomewide linkage analysis for genes responsible for familial IGE in French‐Canadian pedigrees. Twenty families segregating autosomal dominant epilepsy were collected. Four larger IGE families sufficiently powerful for independent linkage analysis were genome‐scanned and follow‐up fine mapping was performed over regions with LOD scores >3.0. The genotyping of 16 smaller families was carried out at significantly linked loci for supportive linkage analysis and haplotype comparisons. One of the four families provided a significant linkage result at marker D10S1426 on chromosome 10 (two‐point LOD score = 3.05, theta = 0, multipoint LOD score = 3.18). Fine mapping revealed a segregating haplotype and key recombination breakpoints, suggesting a candidate gene interval of 6.5 Mb. Multipoint linkage analyses using the additional 16 families yielded a maximum LOD score under heterogeneity of 4.23 (alpha = 0.34) at this locus. Evaluation of recombination breakpoints in these families narrowed the candidate region to 1.7 Mb. Sequencing of the two known genes in this region, NRP1 and PARD3, was negative for mutation. Replication of linkage to this locus in other cohorts of IGE families is essential to characterize the underlying genetic mechanism for the disease.