Cytokines and chemokines expression pattern in herpes simplex virus type-1 encephalitis

Interleukin-2 and its receptors: Implications and therapeutic prospects in immune-mediated disorders of central nervous system

Interleukin-2 (IL-2), the first cloned cytokine, is a multifunctional molecule with diverse cellular origins. As a pivotal T-cell growth factor, IL-2 is crucial for T-cell proliferation and the generation of effector and memory cells. Besides, IL-2 and its receptor (IL-2R) are expressed in various cell types within the brain and have been implicated in the pathogenesis of several neurological disorders. In conditions characterized by primary or secondary inflammatory processes, such as multiple sclerosis, Alzheimer's disease, ischemic stroke, and encephalitis, IL-2/IL-2R expression exhibits region- and subtype-specific and variations associated with disease stages in plasma, cerebrospinal fluid (CSF), and brain tissues. These variations highlight the potential of IL-2/IL-2R as promising diagnostic and prognostic biomarkers, as well as therapeutic targets. This review provides a comprehensive summary of the roles, expression patterns, and regulatory mechanisms of IL-2/IL-2R in immune-mediated disorders of the central nervous system (CNS), with particular emphasis on the impact of genetic polymorphisms in IL-2 and IL-2R subunits on disease susceptibility and progression. In addition, the research advances in IL-2/IL-2R-targeted therapies are also discussed, offering novel insights into the immunotherapeutic strategies for CNS diseases.

Investigation of the association between circulating inflammatory proteins and encephalitis risk in Europeans by two-sample Mendelian randomization analysis

Background

Cytokines are powerful immune response factors that operate at inflammation sites and are also found in the blood. Nevertheless, research on encephalitis and these circulating inflammatory proteins is quite limited.

Methods

This study investigated the potential causal effects of 91 circulating inflammatory proteins on three different types of encephalitis using a two-sample Mendelian randomisation analysis. The data source for encephalitis was the latest Finngen_R12 dataset, released in 2024. The study investigated causal effects mainly using Steiger, MR-Egger, weighted median and inverse variance weighting (IVW) methods. In addition, sensitivity analyses were performed, including heterogeneity assessment, horizontal pleiotropy and leave-one-out techniques.

Results

In this study, 91 circulating inflammatory proteins were subjected to MR analysis of causality with each of the three types of encephalitis. The results suggest that the inflammatory factors with a potential causal relationship with viral encephalitis are artemin, C-C motif chemokine 28, C-X-C motif chemokine 1, interleukin-10 and neurotrophin-3. Inflammatory factors potentially causally associated with acute disseminated encephalomyelitis are monocyte chemoattractant protein 2, interleukin-10 receptor subunit beta and matrix metalloproteinase-1. Inflammatory factors potentially causally associated with autoimmune encephalitis are C-C motif chemokine 28 levels and Macrophage inflammatory protein 1a levels.

Conclusion

This study identifies potential causal effects of certain circulating inflammatory factors on susceptibility to three types of encephalitis. Although the exact mechanisms by which inflammatory proteins contribute to the pathogenesis of different encephalitis subtypes remain unclear, our findings provide new perspectives on these potential causal relationships.

Causal relationship between circulating inflammatory proteins and risk of different types of encephalitis: A two-sample Mendelian randomization study

BACKGROUND

Cytokines are potent molecules of the immune response. They act at the site of inflammation and circulate in the bloodstream. However, there are few studies on encephalitis and circulating inflammatory proteins.

METHODS

In this study, Mendelian randomization (MR) was used to explore the potential causal effect of 91 circulating inflammatory proteins on 3 different types of encephalitis. Causal effects were examined using Steiger, MR-Egger, weighted median, and inverse variance weighting (IVW) methods. IVW methods were primarily used for results interpretation. In addition, sensitivity analyses were performed, including assessment of heterogeneity, horizontal pleiotropy, and Leave-one-out techniques.

RESULTS

We subjected 91 circulating inflammatory proteins to MR analysis of causality with each of the three types of encephalitis. The results suggested that the inflammatory factors with a potential causal relationship with viral encephalitis were caspase 8, C-X-C motif chemokine 6, interleukin-10, interleukin-15 receptor subunit alpha, interleukin-7, and TNF-beta. Inflammatory factors potentially causally associated with acute disseminated encephalomyelitis are beta-nerve growth factor, cystatin D, interleukin-7, Latency-associated peptide transforming growth factor beta 1,and neurotrophin-3.Inflammatory factors potentially causally associated with autoimmune encephalitis are C-C motif chemokine 25, hepatocyte growth factor, latency-associated peptide transforming growth factor beta 1, programmed cell death 1 ligand 1, sulfotransferase 1A1, and tumor necrosis factor.

CONCLUSION

This finding identifies potential causal effects of certain circulating inflammatory factors on susceptibility to three types of encephalitis. It also suggests the therapeutic potential of modulating the levels of these cytokines. A basis for further research is provided.

Cytokines and chemokines profile in encephalitis patients: A meta-analysis

BACKGROUND

Encephalitis is caused by autoimmune or infectious agents marked by brain inflammation. Investigations have reported altered concentrations of the cytokines in encephalitis. This study was conducted to determine the relationship between encephalitis and alterations of cytokine levels in cerebrospinal fluid (CSF) and serum.

METHODS

We found possibly suitable studies by searching PubMed, Embase, Scopus, and Web of Science, systematically from inception to August 2021. 23 articles were included in the meta-analysis. To investigate sources of heterogeneity, subgroup analysis and sensitivity analysis were conducted. The protocol of the study has been registered in PROSPERO with a registration ID of CRD42021289298.

RESULTS

A total of 23 met our eligibility criteria to be included in the meta-analysis. A total of 12 cytokines were included in the meta-analysis of CSF concentration. Moreover, 5 cytokines were also included in the serum/plasma concentration meta-analysis. According to the analyses, patients with encephalitis had higher CSF amounts of IL-6, IL-8, IL-10, CXCL10, and TNF-α than healthy controls. The alteration in the concentration of IL-2, IL-4, IL-17, CCL2, CXCL9, CXCL13, and IFN-γ was not significant. In addition, the serum/plasma levels of the TNF-α were increased in encephalitis patients, but serum/plasma concentration of the IL-6, IL-10, CXCL10, and CXCL13 remained unchanged.

CONCLUSIONS

This meta-analysis provides evidence for higher CSF concentrations of IL-6, IL-8, IL-10, CXCL10, and TNF-α in encephalitis patients compared to controls. The diagnostic and prognostic value of these cytokines and chemokines should be investigated in future studies.