The association of IL-8-251T/A polymorphism with complicated malaria in Karbi Anglong district of Assam

Cytokine gene polymorphisms implicated in the pathogenesis of Plasmodium falciparum infection outcome

Cytokines play a critical role in the immune mechanisms involved in fighting infections including malaria. Polymorphisms in cytokine genes may affect immune responses during an infection with Plasmodium parasites and immunization outcomes during routine administration of malaria vaccines. These polymorphisms can increase or reduce susceptibility to this deadly infection, and this may affect the physiologically needed balance between anti-inflammatory and pro-inflammatory cytokines. The purpose of this review is to present an overview of the effect of selected cytokine gene polymorphisms on immune responses against malaria.

A systematic review and meta-analysis of changes in interleukin-8 levels in malaria infection

The roles of interleukin-8 (IL-8) in malaria are inconsistent and unclear. This study synthesised evidence for differences in IL-8 levels in patients with malaria of various levels of severity. Relevant studies were searched in Scopus, MEDLINE, Embase, CENTRAL and PubMed from inception to 22 April 2022. Pooled mean differences (MDs) and 95% confidence intervals (CIs) were estimated using the random effects model. Of 1083 articles retrieved from the databases, 34 were included for syntheses. The meta-analysis revealed increased IL-8 levels in individuals with uncomplicated malaria compared with those without malaria (P = 0.04; MD, 25.57 pg/mL; 95% CI, 1.70 to 49.43 pg/mL; I2, 99.53, 4 studies; 400 uncomplicated malaria, 204 uninfected controls). The meta-analysis revealed comparable levels of IL-8 between the two groups (P = 0.10; MD, 74.46 pg/mL; 95% CI, -15.08 to 164.0 pg/mL; I2, 9.03; 4 studies; 133 severe malaria cases, 568 uncomplicated malaria cases). The study found evidence of increased IL-8 levels in individuals with malaria compared with those without malaria. However, no differences were found in IL-8 levels between patients with severe and non-severe malaria. Further research is needed to investigate the IL-8 cytokine levels in patients with malaria of different levels of severity.

Recent Advances in Understanding the Inflammatory Response in Malaria: A Review of the Dual Role of Cytokines

Malaria is a serious and, in some unfortunate cases, fatal disease caused by a parasite of the Plasmodium genus. It predominantly occurs in tropical areas where it is transmitted through the bite of an infected Anopheles mosquito. The pathogenesis of malaria is complex and incompletely elucidated. During blood-stage infection, in response to the presence of the parasite, the host's immune system produces proinflammatory cytokines including IL-6, IL-8, IFN-γ, and TNF, cytokines which play a pivotal role in controlling the growth of the parasite and its elimination. Regulatory cytokines such as transforming growth factor- (TGF-) β and IL-10 maintain the balance between the proinflammatory and anti-inflammatory responses. However, in many cases, cytokines have a double role. On the one hand, they contribute to parasitic clearance, and on the other, they are responsible for pathological changes encountered in malaria. Cytokine-modulating strategies may represent a promising modern approach in disease management. In this review, we discuss the host immune response in malaria, analyzing the latest studies on the roles of pro- and anti-inflammatory cytokines.

Genetic Diversity of Human Host Genes Involved in Immune Response and the Binding of Malaria Parasite in Patients Residing along the Thai-Myanmar border

Polymorphisms of the genes encoding proteins involved in immune functions and the binding of malaria parasites to human host cells have been the focus of research in recent years, aiming to understand malaria pathogenesis and case severity and to exploit this knowledge to assert control over malaria. This study investigated the genetic diversity of the human host genes encoding proteins that are involved in immune functions and malaria parasite binding, i.e., MCP1 (−2518), TGFβ1 (−509), TNFα (−308), IL4 (VNTR), IL6 (−174), IL10 (−3575), TLR4 (299), CD36 (−188), and ICAM1 (469) in patients with mono-infection of Plasmodium falciparum and Plasmodium vivax infections in the multidrug-resistant areas along the Thai-Myanmar border. The association between gene polymorphisms and parasite density was also investigated. Genomic DNA (gDNA) of P. falciparum and P. vivax were extracted from whole blood and dried blood spot (DBS). Gene amplification and genotyping were performed by PCR and PCR-RFLP analysis, respectively. Of these samples, 178 and 209 samples were, respectively, mono-infection with P. falciparum and P. vivax. The ratio of P. falciparum: P. vivax was 46%:54%. Results showed marked variation in the frequency distribution and patterns of the genotypes and gene alleles of the nine immune response genes or human host genes. The SNPs of TGFβ1, IL10 and ICAM1, were significantly associated with P. falciparum, but not P. vivax parasite density. TGFβ1, IL10 and ICAM1, may play more significant roles in modulating P. falciparum than P. vivax parasitemia. The prevalence of the genotypes and gene alleles of these genes, including their association with parasite density, may vary depending on patient ethnicity and endemic areas. Information obtained from each endemic area is essential for treatment strategies and the development of vaccines for malaria prophylaxis in specific areas.

The Interface Between Inflammatory Mediators and MicroRNAs in Plasmodium vivax Severe Thrombocytopenia

Severe thrombocytopenia can be a determinant factor in the morbidity of Plasmodium vivax, the most widespread human malaria parasite. Although immune mechanisms may drive P. vivax-induced severe thrombocytopenia (PvST), the current data on the cytokine landscape in PvST is scarce and often conflicting. Here, we hypothesized that the analysis of the bidirectional circuit of inflammatory mediators and their regulatory miRNAs would lead to a better understanding of the mechanisms underlying PvST. For that, we combined Luminex proteomics, NanoString miRNA quantification, and machine learning to evaluate an extensive array of plasma mediators in uncomplicated P. vivax patients with different degrees of thrombocytopenia. Unsupervised clustering analysis identified a set of PvST-linked inflammatory (CXCL10, CCL4, and IL-18) and regulatory (IL-10, IL-1Ra, HGF) mediators. Among the mediators associated with PvST, IL-6 and IL-8 were critical to discriminate P. vivax subgroups, while CCL2 and IFN-γ from healthy controls. Supervised machine learning spotlighted IL-10 in P. vivax-mediated thrombocytopenia and provided evidence for a potential signaling route involving IL-8 and HGF. Finally, we identified a set of miRNAs capable of modulating these signaling pathways. In conclusion, the results place IL-10 and IL-8/HGF in the center of PvST and propose investigating these signaling pathways across the spectrum of malaria infections.

Early Changes in CD4+ T-Cell Activation During Blood-Stage Plasmodium falciparum Infection

We examined transcriptional changes in CD4+ T cells during blood-stage Plasmodium falciparum infection in individuals without a history of previous parasite exposure. Transcription of CXCL8 (encoding interleukin 8) in CD4+ T cells was identified as an early biomarker of submicroscopic P. falciparum infection, with predictive power for parasite growth. Following antiparasitic drug treatment, a CD4+ T-cell regulatory phenotype developed. PD1 expression on CD49b+CD4+ T (putative type I regulatory T) cells after drug treatment negatively correlated with earlier parasite growth. Blockade of PD1 but no other immune checkpoint molecules tested increased interferon γ and interleukin 10 production in an ex vivo antigen-specific cellular assay at the peak of infection. These results demonstrate the early development of an immunoregulatory CD4+ T-cell phenotype in blood-stage P. falciparum infection and show that a selective immune checkpoint blockade may be used to modulate early developing antiparasitic immunoregulatory pathways as part of malaria vaccine and/or drug treatment protocols.

Disease severity and blood cytokine concentrations in dogs with natural Babesia rossi infection

AIMS

Babesia rossi causes severe disease in dogs. Here, we describe the association between serum cytokine concentrations and disease severity.

METHODS

Seventeen controls and 55 PCR confirmed B rossi-infected dogs were included. Diseased dogs were subdivided into 23 critically ill and 32 relatively well cases. Serum concentrations of 11 cytokines and biochemical markers of disease severity were determined.

RESULTS

Significant differences were detected for IL-6, IL-8, IL-10, MCP-1 and TNF-α between the groups. Generally, the more complicated the disease, the more pro-inflammatory the cytokine milieu. IL-8 showed a reverse trend and was negatively correlated with disease severity. IL-6, MCP-1 and TNF-α were also significantly higher in the dogs that died (n = 9) compared to the dogs that survived (n = 46). IL-8 showed the opposite. MCP-1 and TNF-α were negatively correlated with biochemical markers of severity. Glucose was negatively correlated with IL-6. Cortisol, peripheral parasite density and band neutrophil count were positively correlated, whilst thyroid hormone was negatively correlated with IL-6, MCP-1 and TNF-α.

CONCLUSIONS

As in malaria and sepsis, B rossi infection induces a pro-inflammatory cytokine storm that correlates with disease severity and adverse outcome. The multiplicity of cytokines involved argues for redundancy in the system once the disease is established.

Investigation of association between IL-8 serum levels and IL8 polymorphisms in Chinese patients with sepsis

OBJECTIVE

To assess the clinical relevance of IL8 gene polymorphisms in patients with sepsis and its association with systemic IL-8 levels.

METHODS

PCR and DNA sequencing were used to examine the polymorphism of IL8 in 152 patients with sepsis and in 199 healthy volunteers in China. The distribution frequencies of the genotype and allele were compared among different groups. The serum IL-8 was measured by ELISA and analyzed in relation to polymorphisms of IL8.

RESULTS

The homozygote TT genotype and T allele of rs4073 (genotype: p=0.01, allele: p=0.002), the homozygote CC genotype and C allele (genotype: p=0.03, allele: p=0.003) of rs2227306, homozygote AA genotype and A allele of re1126647 (genotype: p=0.01, allele: p=0.002) were associated with susceptibility to sepsis in males. Serum IL-8 levels were significantly increased in patients with sepsis but showed no correlation with IL8 rs4073, rs2227306 and rs1126647 polymorphisms.

CONCLUSIONS

The male population carrying the homozygote TT genotype and T allele of rs4073, the homozygote CC genotype and C allele of rs2227306 and homozygote AA genotype and A allele of rs1126647 are more susceptible to sepsis, suggesting there is a protective effect in females carrying these genotypes and alleles respectively. There was no association between rs4073, rs2227306 and rs1126647 polymorphisms and serum levels of IL-8 in patients with sepsis.

Lower expression of GATA3 and T-bet correlates with downregulated IL-10 in severe falciparum malaria

Interleukin (IL)-10, a non-redundant anti-inflammatory cytokine is produced by different cells and its production involves activation of cell-specific transcriptional regulatory machinery in response to specific pathogen. We have previously demonstrated downregulated levels of IL-10 in severe falciparum malaria. The present study investigated transcriptional regulation of IL-10 in severe malaria. Comparative expression analysis of cell-specific signalling proteins and transcription factors for IL-10 production during the stage of active infection and with resolution of parasitaemia was performed. Interestingly, T-bet and GATA3, the Th1 and Th2 transcription factors, respectively, were downregulated in severe malaria with fold change values of 0.59 and 0.86. Increase in the levels of both the factors with resolution of parasitaemia implicated a role for parasite in depressed levels of these factors. Further support for probable parasite manipulation of GATA3 was obtained from negative correlation of GATA3 with parasitaemia. In addition, a role for interferon-α in suppressing IL-10 transcription was evident from its negative correlation with GATA3 and IL-10 levels. In summary, IL-10 transcription in Th1 and Th2 is defective and appears to have major contribution to low levels in severe malaria.

Cytokine network in adults with falciparum Malaria and HIV-1: increased IL-8 and IP-10 levels are associated with disease severity

Background

Co-infection with malaria and HIV increases the severity and mortality of both diseases, but the cytokine responses related to this co-infection are only partially characterised. The aim of this study was to explore cytokine responses in relation to severity and mortality in malaria patients with and without HIV co-infection.

Methods

This was a prospective cross-sectional study. Clinical data and blood samples were collected from adults in Mozambique. Plasma was analysed for 21 classical pro- and anti-inflammatory cytokines, including interleukins, interferons, and chemokines.

Results

We included 212 in-patients with fever and/or suspected malaria and 56 healthy controls. Falciparum malaria was diagnosed in 131 patients, of whom 70 were co-infected with HIV-1. The malaria patients had marked increases in their cytokine responses compared with the healthy controls. Some of these changes, particularly interleukin 8 (IL-8) and interferon-γ-inducing protein 10 (IP-10) were strongly associated with falciparum malaria and disease severity. Both these chemokines were markedly increased in patients with falciparum malaria as compared with healthy controls, and raised levels of IL-8 and IP-10 were associated with increased disease severity, even after adjusting for relevant confounders. For IL-8, particularly high levels were found in malaria patients that were co-infected with HIV and in those who died during hospitalization.

Interpretations

Our findings underscore the complex role of inflammation during infection with P. falciparum, and suggest a potential pathogenic role for IL-8 and IP-10. However, the correlations do not necessarily mean any causal relationship, and further both clinical and mechanistic research is necessary to elucidate the role of cytokines in pathogenesis and protection during falciparum malaria.

Heightened inflammation in severe malaria is associated with decreased IL-10 expression levels and neutrophils

Dysregulation of the cytokine network in severe malaria owing to variations in factors like parasite load, strains and host factors is well documented but the key cytokines that are dysregulated remain poorly elucidated. Longitudinal changes in cytokine levels in an individual with parasitemia and disease resolution is likely to identify the key cytokines. We have analyzed the mRNA expression of cytokines over a 7-d period in severe (SM) and uncomplicated (UM) Plasmodium falciparum malaria. We found up-regulated expression of TNF-α, IL-1β, IFN-γ and TGF-β in SM, with decreased expression of IL-10 on d 0. Further, we observed a negative correlation of IL-10 expression with parasitemia and pro-inflammatory cytokines, suggesting IL-10 to be the key cytokine in tilting the balance to an inflammatory response. Longitudinal analysis revealed that the key cytokines associated with disease were TNF-α, IL-1β, IFN-γ, IL-12α, RANTES and TGF-β, while TNF-α, IL-10 and TGF-β discriminated between SM and UM. A higher neutrophil count in SM and its positive association with parasite density and IL-1β and IL-8 provides support for neutrophils in inflammation in malaria. Our findings suggest subversion of anti-inflammatory response in SM by parasite factors towards an exaggerated pro-inflammatory response with involvement of neutrophils, the classical inflammatory cells.

Analysis of LPS-induced, NFκB-dependent interleukin-8 transcription in kidney embryonic cell line expressing TLR4 using luciferase assay

Gene expression is orchestrated by a complex network of signal transduction pathways that typically originate on cell surface receptors and culminate in DNA-binding transcription factors, which translocate to the nucleus and bind cis-regulatory elements in promoter regions of genes, thereby inducing de novo synthesis of the nascent RNA transcripts and their splicing. Gene expression arrays monitor abundance of the matured, spliced cDNA, which undergoes additional posttranscriptional modifications that greatly affect the half-life of the cDNA. Thus, the relative abundance of cDNA is not necessarily commensurable with the activity of promoters of the corresponding genes. In contrast, reporter gene assays provide valuable insight into the regulation of gene expression at the level of transcription and allow for discerning the contribution of individual transcription factors into changes in gene expression. Here, we describe a robust reporter gene assay method that is useful for exploration of transcription regulatory network, which regulates gene expression in response to inflammation. The method is exemplified by using the promoter region of the prototypic pro-inflammatory chemokine interleukin-8 (IL-8, CXCL8), which plays an important role in immune response as well as carcinogenesis. Using the luciferase reporter gene assay, we analyze the activation status of the IL-8 promoter in lipopolysaccharide (LPS)-stimulated human embryonic kidney cells.