Advances in immune checkpoint-based immunotherapies for multiple sclerosis: rationale and practice

Beyond the encouraging results and broad clinical applicability of immune checkpoint (ICP) inhibitors in cancer therapy, ICP-based immunotherapies in the context of autoimmune disease, particularly multiple sclerosis (MS), have garnered considerable attention and hold great potential for developing effective therapeutic strategies. Given the well-established immunoregulatory role of ICPs in maintaining a balance between stimulatory and inhibitory signaling pathways to promote immune tolerance to self-antigens, a dysregulated expression pattern of ICPs has been observed in a significant proportion of patients with MS and its animal model called experimental autoimmune encephalomyelitis (EAE), which is associated with autoreactivity towards myelin and neurodegeneration. Consequently, there is a rationale for developing immunotherapeutic strategies to induce inhibitory ICPs while suppressing stimulatory ICPs, including engineering immune cells to overexpress ligands for inhibitory ICP receptors, such as program death-1 (PD-1), or designing fusion proteins, namely abatacept, to bind and inhibit the co-stimulatory pathways involved in overactivated T-cell mediated autoimmunity, and other strategies that will be discussed in-depth in the current review. Video Abstract.

The Role of Cytotoxic T-Lymphocyte Antigen 4 in the Pathogenesis of Multiple Sclerosis

Multiple sclerosis (MS) is an autoimmune neurodegenerative disorder of the central nervous system that presents heterogeneous clinical manifestations and course. It has been shown that different immune checkpoints, including Cytotoxic T-Lymphocyte Antigen 4 (CTLA-4), can be involved in the pathogenesis of MS. CTLA-4 is a critical regulator of T-cell homeostasis and self-tolerance and represents a key inhibitor of autoimmunity. In this scopingreview, we resume the current preclinical and clinical studies investigating the role of CTLA-4 in MS with different approaches. While some of these studies assessed the expression levels of CTLA-4 on T cells by comparing MS patients with healthy controls, others focused on the evaluation of the effects of common MS therapies on CTLA-4 modulation or on the study of the CTLA-4 blockade or deficiency in experimental autoimmune encephalomyelitis models. Moreover, other studies in this field aimed to discover if the CTLA-4 gene might be involved in the predisposition to MS, whereas others evaluated the effects of treatment with CTLA4-Ig in MS. Although these results are of great interest, they are often conflicting. Therefore, further studies are needed to reveal the exact mechanisms underlying the action of a crucial immune checkpoint such as CTLA-4 in MS to identify novel immunotherapeutic strategies for MS patients.

The role of immune regulatory molecules in multiple sclerosis

Multiple sclerosis (MS) is the most common demyelinating disease which mainly impacts the integrity of central nervous system (CNS). MS etiology is not clearly known but genetic, environmental factors and immune system are the most frequently explored risk factors. Adaptive immune responses have a critical role in MS pathogenesis in which auto-reactive T-cells and autoantibodies are main orchestrators. Immune responses are modulated by inhibitory molecules which regulates adaptive system activation and hemostasis interface. These molecules suppress immune responses through inhibition of cytokine secretion and T cell proliferation and subsequently reducing the inflammation and respective damage. Therefore the critical role of inhibitory molecules in regulating the healthy and safe immune responses make them very attractive target for immunotherapy. In this review paper, the role of inhibitory molecules expressed on the various immune cell types in MS pathogenesis and experimental autoimmune encephalomyelitis (EAE) animal model will be summarized.

Correlation between CTLA-4 gene rs221775A>G single nucleotide polymorphism and multiple sclerosis susceptibility. A meta-analysis

OBJECTIVE

The aim of this meta-analysis was to undertake a meta-analysis to evaluate the correlation between cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) gene rs221775 A>G single nucleotide polymorphism and the susceptibility of multiple sclerosis (MS) susceptibility.

METHOD

Published manuscripts about CTLA-4 gene rs221775A>G single nucleotide polymorphism and multiple sclerosis susceptibility were searched in the computerized bibliographic searches of Pubmed Embase and China National Knowledge Infrastructure (CNKI). Potential studies were screened and data for 5025 MS patients and 4706 controls from 20 publications were included. The association between CTLA-4 gene rs221775A>G single nucleotide polymorphism and multiple sclerosis susceptibility were demonstrated by odds ratio (OR) and 95% confidence interval (95%CI).

RESULTS

The pooled results showed no significant association between CTLA-4 gene rs221775A>G single nucleotide polymorphism and multiple sclerosis susceptibility for dominant genetic model [OR=1.02, 95%CI:0.90~1.05, (P=0.80)], homozygous genetic model [OR=0.85,95%CI:0.71 ~1.03,(P=0.10)] and recessive genetic model [OR=0.99,95% CI:0.89~1.10,(P=0.90)].

CONCLUSION

With current evidence, CTLA-4 gene rs221775A>G single nucleotide polymorphism had no association with the susceptibility of multiple sclerosis.

CTLA-4 gene and the susceptibility of multiple sclerosis: an updated meta-analysis study including 12,916 cases and 15,455 controls

Abstract Cytotoxic T-lymphocyte antigen-4 (CTLA-4) is a cell surface molecule involved in the regulation of T cells. Single-nucleotide polymorphisms (SNPs) of CTLA-4 gene are known to be associated with susceptibility to several autoimmune diseases, including multiple sclerosis (MS). This study aimed to evaluate the association between CTLA-4 and the risk of MS. Comprehensive meta-analysis was applied to case-control studies of the association between MS and CTLA-4 to assess the joint evidence for the association, the influence of individual studies, and evidence for publication bias. The authors searched PubMed, MEDLINE, Cochrane Library, and reference lists of relevant studies to September 2013. In all, the allele or genotype analysis showed no significant association between + 49A/G, - 318C/T, or CT60A/G and MS. And the subgroups of the three polymorphisms divided into Americas, Europe, and Asia showed no significant association with MS. The sensitivity analysis or publication bias analysis showed no significance. In conclusion, this comprehensive meta-analysis suggested that + 49A/G, - 318C/T, or CT60A/G polymorphism, either in total analysis or in subgroup analyses, has no significant association with MS disease.

Cytotoxic T-lymphocyte antigen 4 (CTLA4) +49AG and CT60 gene polymorphisms in Alopecia Areata: a case-control association study in the Italian population

Alopecia Areata (AA) is an autoimmune disease characterized by well-circumscribed patches of hair loss especially from the scalp. Cytotoxic T-lymphocyte antigen 4 (CTLA4) gene, a negative regulator of T cells, has been associated with predisposition to most autoimmune disorders. We evaluated two CTLA4 functional single-nucleotide polymorphisms (SNPs) for potential association with Alopecia Areata in an Italian population using a case-control approach. We genotyped +49AG (rs231775) and CT60 (rs3087243) variants in 130 AA patients and 189 ethnically matched controls by the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. CTLA4 +49AG analysis revealed no statistically significant difference in both the allele and genotype frequencies between patients and controls. As regarding CT60 SNP, we found that AA cases less frequently than healthy subjects carried A/A genotype with a higher prevalence of A/G and G/G genotypes (83.8 and 75.1 %; p = 0.041, OR = 0.58, 95 % CI 0.32-1.03), consistent with a dominant effect of G disease risk allele. In particular, it seemed to exert effects mainly in DQ7-negative patients with a less aggressive form of the disease. Haplotype analysis suggested that the G(+49AG), A(CT60) allelic combination was significantly related to a reduced disease risk (p = 0.014, OR = 0.28, 95 % 0.09-0.82). Altogether, our findings confirm that only CTLA4 CT60 polymorphism seems to be an important genetic determinant of Alopecia Areata development in Italian subjects.

Fractalkine gene receptor polymorphism in patients with multiple sclerosis

BACKGROUND

Although the immunopathogenesis of multiple sclerosis (MS) has been intensely investigated in recent years, some associated molecules still have not been examined. For instance, no study has been conducted to investigate a possible polymorphism in the fractalkine receptor gene.

METHODS

In order to examine fractalkine gene receptor polymorphisms, 3 mL of serum from 92 MS patients and 91 controls were stored at -20°C. DNA was extracted from the serum samples that were purified, and the gene regions in CX3CR1 (i.e., the fractalkine regions) containing the T280M and V294I fractalkine receptor haplotypes were amplified via the polymerase chain reaction (PCR) technique. The obtained fragments were then cut using restriction enzymes, and agarose gel electrophoresis was performed.

RESULTS

In a comparison of the patients and controls, we found that the median values of the Expanded Disability Status Scale (EDSS) scores among genotypes of the V294I polymorphism in the fractalkine gene receptor were statistically higher in genotype II than genotype VI. Also, relapsing/remitting MS (RRMS) was statistically higher in genotype VI than in genotype II, whereas the frequency of secondary progressive MS (SPMS) was statistically higher in genotype VV than in the genotype VI for the same polymorphism.

CONCLUSIONS

Although many polymorphism studies have focused on patients with MS, there is no polymorphism study about the fractalkine receptor which is a chemokine and plays an important role in neuroinflammation and neurodegeneration. Our results provide information about disease progression and may also be beneficial in developing new strategies for the treatment of the disease.

The sad plight of multiple sclerosis research (low on fact, high on fiction): critical data to support it being a neurocristopathy

The literature for evidence of autoimmunity in multiple sclerosis (MS) is analysed critically. In contrast to the accepted theory, the human counterpart of the animal model experimental autoimmune demyelinating disease, experimental allergic encephalomyelitis (EAE), is not MS but a different demyelinating disorder, i.e. acute disseminated encephalomyelitis and acute haemorrhagic leucoencephalitis. Extrapolation of EAE research to MS has been guided largely by faith and a blind acceptance rather than sound, scientific rationale. No specific or sensitive immunological test exists that is diagnostic of MS despite the extensive application of modern technology. Immunosuppression has failed to have any consistent effect on prognosis or disease progression. The available data on MS immunotherapy are conflicting, at times contradictory and are based on findings in animals with EAE. They show predominantly a 30% effect in relapsing/remitting MS which suggests powerful placebo effect. Critical analysis of the epidemiological data shows no association with any specific autoimmune diseases, but does suggest that geographic factors and age at development posit an early onset possibly dependent on environmental influences. Certain neurological diseases are, however, found in association with MS, namely hypertrophic peripheral neuropathy, neurofibromatosis-1, cerebral glioma, glioblastoma multiforme and certain familial forms of narcolepsy. These share a common genetic influence possibly from genes on chromosome 17 affecting cell proliferation. A significant number of these disorders are of neural crest origin, the classical example being abnormalities of the Schwann cell. These and other data allow us to propose that MS is a developmental neural crest disorder, i.e. a cristopathy, implicating glial cell dysfunction with diffuse blood-brain barrier breakdown. The data on transcription factor SOX10 mutations in animals may explain these bizarre clinical associations with MS and the phenotypic variability of such alterations (Cossais et al. 2010). Research directed to the area of neural crest associations is likely to be rewarding.

CTLA4 -1661A/G and 3'UTR long repeat polymorphisms are associated with ulcerative colitis and influence CTLA4 mRNA and protein expression

Reduced cytotoxic T-lymphocyte antigen 4 (CTLA4) expression has been proposed as a risk for autoimmunity. CTLA4 polymorphisms have been associated with several autoimmune diseases, including ulcerative colitis (UC). In this study, we performed genotyping for CTLA4 -1661A/G, -1722T/C and 3' untranslated region (AT)n repeat polymorphisms in 300 Chinese UC patients and in 700 healthy controls, and evaluated the effects of polymorphisms on full-length (flCTLA4) and soluble CTLA4 (sCTLA4) expression in UC patients. The frequency of the -1661G allele was higher in UC patients than in healthy controls (16.5 vs 11.4%, P=0.003, odds ratio (OR)=1.53, 95% confidence interval (95% CI): 1.17-2.01). The prevalence of (AT)n repeats of the CTLA4 gene carrying long alleles (≥116 bp) was more common in UC patients than in healthy controls (22.0 vs 6.3%, P<0.001, OR=4.21, 95% CI: 2.79-6.33), and was associated with extensive colitis (P=0.008). Among UC patients, long-allele carriers expressed lower levels of flCTLA4 and sCTLA4 mRNA and sCTLA4 protein than did short-allele carriers (P<0.001, P<0.001, P<0.001, respectively). CTLA4 gene -1661A/G and long 3' untranslated region (AT)n repeat polymorphisms are associated with UC in Central China. This is likely from decreased expressions of sCTLA4 mRNA and sCTLA4 protein. Our study suggests that CTLA4 has an important role in susceptibility for UC in Central China.

Type 1 diabetes mellitus and multiple sclerosis: common etiological features

Type 1 diabetes mellitus and multiple sclerosis have been largely seen as different, organ-specific diseases, which are managed by different medical specialties. Research studies on these diseases have for the most part followed independent tracks. In this Review, we highlight the latest epidemiological and genetic findings, which have identified many features common to both disorders. Experts consider it increasingly likely that the environment contributes substantially to this overlap. However, although genetic elements that are distinct to each disease probably determine the ultimate form of autoimmunity that is manifested, strikingly broad parallels are seen between the components of genetic risk of type 1 diabetes mellitus and multiple sclerosis. Similarities and differences between these two diseases draw attention to shared disease pathways but insights into each disorder are providing mutual illumination of their pathogenesis.

The CTLA-4 gene polymorphisms are associated with CTLA-4 protein expression levels in multiple sclerosis patients and with susceptibility to disease

Cytotoxic T-lymphocyte antigen-4 (CTLA-4) is an important molecule in the down-regulation of T-cell activation. A study was undertaken to evaluate the association of the CTLA-4 gene polymorphisms -319C/T, +49A/G, (AT)(n), CT60A/G and Jo31G/T with the levels of membrane CTLA-4 (mCTLA-4) and cytoplasmic CTLA-4 (cCTLA-4) in CD4(+) T lymphocytes from patients with multiple sclerosis (MS) and with susceptibility to MS, and the course of the disease. It was found that the Jo31GG and CT60GG genotypes were associated with decreased mean fluorescence intensity (MFI) of total CTLA-4 (mCTLA-4 + cCTLA-4) molecules in CD4(+) T cells from both relapsing-remitting (RR) and secondary progressive (SP) MS patients compared with others. Consequently, possessing the Jo31G allele and/or the CT60G allele were associated with susceptibility to MS. The percentages of cells expressing mCTLA-4 and cCTLA-4 in RR patients were higher in carriers of the alleles non-predisposing to MS (namely CT60A and Jo31T), but the percentages of corresponding cells were unexpectedly significantly lower in SP patients than in RR patients. Increased risk of paresthesia and pyramidal signs as a first manifestation of disease, and earlier transition to the SP form in those patients, was also noted. It is hypothesized that the decreasing frequencies of cells expressing immunosuppressive mCTLA-4 and cCTLA-4 in carriers of alleles non-predisposing to MS (i.e. CT60A and Jo31T) may lead to inadequate down-regulation of ongoing T-cell responses in these patients and, as a consequence, earlier progression of disease from the RR form to the SP form.

Genomic regulation of CTLA4 and multiple sclerosis

The cytotoxic T lymphocyte antigen 4 gene (CTLA4) is a critical regulator of T-cell activation and it is an important therapeutic target for cancer and autoimmune diseases. Here, we analyzed the genomic regulation of CTLA4 gene expression in order to identify single nucleotide polymorphisms (SNPs) that affect its expression and splicing, and to assess their association with Multiple Sclerosis (MS). We analyzed 152 healthy subjects and 146 patients with MS, of which 52 controls and 51 patients were used for gene expression analysis. We genotyped 17 SNPs in the CTLA4 gene using the SNaPshot Multiplex Kit, and in addition gene expression of the soluble (sCTLA4) and full length (flCTLA4) isoforms was quantified by real-time PCR, while protein levels of sCTLA4 were measured by ELISA. We found that the SNPs at -1577, +6230, +10242, +10717 and +12310 influence CTLA4 expression and the combination of the -1577 GG and +6230 GG genotypes provokes the strongest decrease in CTLA4 gene expression. We found that the SNP at -658 only acted as a regulatory SNP in patients with MS, suggesting the existence of epigenetic changes due to this disease. We also identified a decrease in CTLA4 gene expression levels in patients receiving chemotherapy, although no association was observed between MS and any of the polymorphisms studied. In conclusion, we have identified several SNPs in the CTLA4 gene and studied their influence on its genetic regulation. The involvement of CTLA4 in the pathogenesis of MS may be subtle and related to the functional changes in its pathway rather than predisposing genetic polymorphisms.

Cytotoxic T lymphocyte associated antigen-4 exon 1 A/G polymorphism in Iranian patients with multiple sclerosis

BACKGROUND

Cytotoxic T lymphocyte antigen-4 (CTLA-4) is a T-cell surface receptor of activated T cells.

MATERIAL AND METHODS

We studied 100 Iranian patients with clinically definite multiple sclerosis (MS) and 100 ethnic, sex- and age-matched controls. CTLA-4 exon 1 A/G polymorphism was compared amongst patients and controls.

RESULTS

There was no statistically significant difference in the allelic [odds ratio (OR): 1.19, confidence interval (CI) 95%: 0.76-1.85, P = 0.4] and genotypes (OR: 1.60, CI 95%: 0.911-2.824, P = 0.102) distribution amongst patients and controls. Also gender, course and progression index did not reveal any statistically significant differences in allele and genotype distribution of A/G polymorphism.

CONCLUSION

As a non-European patient population, our results are consistent with the major previous studies showing no significant associations between CTLA4 exon 1 polymorphism and neither MS nor any of its subtypes.