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Results for “Immune evasion”

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At least 19 recordsLinked to original sources
PubMed2002

Amino acid dimorphism and parasite immune evasion: cellular immune responses to a promiscuous epitope of Plasmodium falciparum merozoite surface protein 1 displaying dimorphic amino acid polymorphism are highly constrained.

Like most other surface-exposed antigens of Plasmodium falciparum, the leading malaria vaccine candidate merozoite surface protein (MSP)-1 contains a large number of dimorphic amino acid positions. This type of diversity is presumed to be associated with parasite immune evasion and represents one major obstacle to malaria subunit vaccine development. To understand the precise role of antigen dimorphism in immune evasion, we have analyzed the flexibility of CD4 T cell immune responses against a semi-conserved sequence stretch of the N-terminal block of MSP-1. While this sequence contains overlapping promiscuous T cell epitopes and is a target for growth inhibitory antibodies, three dimorphic amino acid positions may limit its suitability as component of a multi-epitope malaria vaccine. We have analyzed the CD4 T cell responses in a group of human volunteers immunized with a synthetic malaria peptide vaccine containing a single MSP-143-53 sequence variant. All human T cell lines and HLA-DR- or -DP-restricted T cell clones studied were exclusively specific for the sequence variant used for immunization. Competition peptide binding assays with affinity-purified HLA-DR molecules indicated that dimorphism does not primarily affect HLA binding. Modeling studies of the dominant restricting HLA-DRB1*0801 molecule showed that the dimorphic amino acids represent potential TCR contact residues. Lack of productive triggering of the TCR by MHC/variant peptide ligand complexes thus seems to be the characteristic feature of parasite immune evasion associated with antigen dimorphism.

Amino Acid Sequence↗
PubMed2001

Immunological genomics of Brugia malayi: filarial genes implicated in immune evasion and protective immunity.

Filarial nematodes are metazoan parasites with genome sizes of> 100 million base pairs, probably encoding 15 000-20 000 genes. Within this considerable gene complement, it seems likely that filariae have evolved a spectrum of immune evasion products which underpin their ability to live for many years within the human host. Moreover, no suitable vaccine currently exists for human filarial diseases, and few markers have yet been established for diagnostic use. In this review, we bring together biochemical and immunological data on prominent filarial proteins with the exciting new information provided by the Filarial Genome Project's expressed sequence tag (EST) database. In this discussion, we focus on those genes with the highest immunological profile, such as inhibitors of host enzymes, cytokine homologues and stage-specific surface proteins, as well as products associated with the mosquito-borne infective larva which offer the best opportunity for an anti-filarial vaccine. These gene products provide a fascinating glimpse of the molecular repertoire which helminth parasites have evolved to manipulate and evade the mammalian immune response.

Animals↗
PubMed2004

Human cytomegalovirus inhibits tapasin-dependent peptide loading and optimization of the MHC class I peptide cargo for immune evasion.

The immune evasion protein US3 of human cytomegalovirus binds to and arrests MHC class I molecules in the endoplasmic reticulum (ER). However, substantial amounts of class I molecules still escape US3-mediated ER retention, suggesting that not all class I alleles are affected equally by US3. Here, we identify tapasin inhibition as the mechanism of MHC retention by US3. US3 directly binds tapasin and inhibits tapasin-dependent peptide loading, thereby preventing the optimization of the peptide repertoire presented by class I molecules. Due to the allelic specificity of tapasin toward class I molecules, US3 affects only class I alleles that are dependent on tapasin for peptide loading and surface expression. Accordingly, tapasin-independent class I alleles selectively escape to the cell surface.

Animals↗
PubMed2025

Malaria: Factors affecting disease severity, immune evasion mechanisms, and reversal of immune inhibition to enhance vaccine efficacy.

Malaria is a complex parasitic disease caused by species of Plasmodium parasites. Infection with the parasites can lead to a spectrum of symptoms and disease severity, influenced by various parasite, host, and environmental factors. There have been some successes in developing vaccines against the disease recently, but the vaccine efficacies require improvement. Some issues associated with the difficulties in developing a sterile vaccine include high antigenic diversity, switching expression of the immune targets, and inhibition of immune pathways. Current vaccine research focuses on identifying conserved and protective epitopes, developing multivalent vaccines (including the whole parasite), and using more powerful adjuvants. However, overcoming the systematic immune inhibition and immune cell dysfunction/exhaustion may be required before high titers of protective antibodies can be achieved. Increased expression of surface molecules such as CD86 and MHC II on antigen-presenting cells and blocking immune checkpoint pathways (interactions of PD-1 and PD-L1; CTLA-4 and CD80) using small molecules could be a promising approach for enhancing vaccine efficacy. This assay reviews the factors affecting the disease severity, the genetics of host-parasite interaction, immune evasion mechanisms, and approaches potentially to improve host immune response for vaccine development.

Humans↗
PubMed2001

Expression of Fas ligand by microglia: possible role in glioma immune evasion.

The immune-privileged status of the central nervous system is thought to limit the application of immunotherapy for treatment of malignant brain tumors. Because the Fas pathway has been proposed to play a role in immune evasion, we examined the effect of tumor environment on the expression of Fas ligand (FasL) in a mouse glioma model. Immunoblotting revealed the expression of membrane-bound FasL to nearly double when murine G26 gliomas were propagated intracranially (IC) as compared to subcutaneously (SC). Further analysis by flow cytometry revealed microglia, which were absent in the SC tumors, to account for half of the FasL expression in the IC tumors. Interestingly, when FasL activity was inhibited in IC tumors, the proportion of tumor-infiltrating leukocytes increased three-fold, reaching the same frequency as the SC tumors. These observations suggest that microglia are a major source of FasL expression in brain tumors and possibly contribute to the local immunosuppressive milieu of malignant gliomas.

Animals↗
PubMed2001

Viral immune evasion strategies and the underlying cell biology.

Evasion of the immune system by viruses is a well-studied field. It remains a challenge to understand how these viral tactics affect pathogenesis and the viral lifecycle. At the same time, the study of viral proteins involved in immune evasion has helped us to better understand a number of cellular processes at the molecular level. Here we review recent data on different viral tactics for immune evasion and highlight what these viral interventions might teach us about cell biology.

Animals↗
PubMed1997

Parasite immune evasion and exploitation: reflections and projections.

Recent developments in parasite immune evasion and exploitation are reviewed with special reference to the papers presented in this volume. Parasites, broadly defined, of animals with good immune responses have evolved many strategies that adapt them to survive and reproduce. These strategies may be passive, or may involve active intervention with host immune regulation, and can be categorized as immune evasion, immune exploitation and molecular piracy. The concept of immune evasion began with Paul Ehrlich's demonstration of antigenic variation in African trypanosomes and was reinforced by later ideas on molecular mimicry. Molecular mimicry is updated in the light of recent discoveries about degeneracy and plasticity of TCR/MHC-peptide recognition. Possible connections between two of its postulated consequences, evasion and autoimmunity, are discussed. Another putative consequence of molecular mimicry, host antigenic polymorphism, is also updated. The concept of exploitation of host immune responses by parasites has been reinforced by new data on its first known examples, especially the immune dependence of schistosome egg excretion. Newer examples include use of host cytokines as parasite growth factors, virokines, viroreceptors and helminth pseudocytokines. Finally, questions of host gene capture by viruses and possible horizontal gene transfer between host and parasite mediated by retroviruses are examined. The latter is compared with molecular conservation as a source of molecular mimicry and other aspects of host--parasite coevolution.

Animals↗
PubMed2026

Hypoimmune platforms: from rejection to immune evasion and regulatory implications.

The growing gap between organ demand and clinical availability has renewed interest in immune-evasive graft strategies, yet rejection and lifelong immunosuppression remain major barriers to durable success. Advances in genome editing enable immune-evasive cell platforms designed to avoid immune recognition while replacing missing function in allogeneic settings. This review summarizes current strategies for engineering immune-evasive grafts that simultaneously suppress adaptive and innate immune responses. We discuss how coordinated modulation of antigen presentation and immune checkpoint pathways can protect transplanted allogeneic cells and tissues from T, NK, and macrophage-mediated rejection. We also present the emerging concept of integrating hypoimmune engineering with genetically modified porcine donors, where extensive genome editing has reduced, but not eliminated, xenogeneic immune barriers. Combining donor genome modification with immune-evasive graft design represents a promising conceptual advance toward xenograft survival, though whether full elimination of systemic immunosuppression is achievable remains to be established clinically. We further examine how the regulatory landscape for these products is evolving across major jurisdictions, and how differences in approval pathways, manufacturing standards, and long-term surveillance requirements shape the path to clinical translation. Finally, we outline the safety considerations and remaining limitations in immune evasion that must be addressed to enable clinical implementation.

Graft Rejection↗
PubMed2026

Machine learning and multi-omics clustering to map cellular rewiring and immune evasion in ccRCC.

Immune checkpoint blockade (ICB) efficacy in clear cell renal cell carcinoma (ccRCC) is limited by tumor microenvironment (TME) heterogeneity. Because traditional bulk-derived models lack spatial resolution, we developed an integrated framework connecting macroscopic survival risks to microscopic TME structures. We applied ten algorithms to establish multi-omics subtypes and evaluated 101 machine-learning combinations across three independent cohorts to generate a Consensus Machine Learning-driven Signature (CMLS). The signature's spatial and cellular origins were decoded using spatial transcriptomics (ST) and a 140,000-cell scRNA-seq atlas. Expression of key genes was experimentally validated via RT-qPCR in 17 paired ccRCC clinical tissues. We identified two molecular subtypes with distinct clinical and epigenetic profiles. SuperPC optimization yielded a 24-gene CMLS serving as an independent prognostic factor. scRNA-seq and ST deconvolution revealed these signals predominantly originate from cancer-associated fibroblasts (CAFs) and malignant epithelial cells, which collaborate to drive spatial immune exclusion. RT-qPCR confirmed significant overexpression of five core CMLS genes in ccRCC versus adjacent normal tissues. Low CMLS scores correlated with enhanced ICB responsiveness, whereas high-CMLS tumors demonstrated specific vulnerability to dasatinib and dabrafenib. The CMLS translates spatial immune-exclusion dynamics into a quantifiable metric, outperforming tumor mutational burden in predicting ICB benefits, providing a robust tool for patient stratification in ccRCC.

Humans↗
PubMed2003

Blocking immune evasion as a novel approach for prevention and treatment of herpes simplex virus infection.

Many microorganisms encode immune evasion molecules to escape host defenses. Herpes simplex virus type 1 glycoprotein gC is an immunoevasin that inhibits complement activation by binding complement C3b. gC is expressed on the virus envelope and infected cell surface, which makes gC potentially accessible to blocking antibodies. Mice passively immunized with gC monoclonal antibodies prior to infection were protected against herpes simplex virus challenge only if the gC antibodies blocked C3b binding. Mice treated 1 or 2 days postinfection with gC monoclonal antibodies that block C3b binding had less severe disease than control mice treated with nonimmune immunoglobulin G (IgG). Mice immunized with gC protein produced antibodies that blocked C3b binding to gC. Immunized mice were significantly protected against challenge by wild-type virus, but not against a gC mutant virus lacking the C3b binding domain, suggesting that protection was mediated by antibodies that target the gC immune evasion domain. IgG and complement from subjects immunized with an experimental herpes simplex virus glycoprotein gD vaccine neutralized far more mutant virus defective in immune evasion than wild-type virus, supporting the importance of immune evasion molecules in reducing vaccine potency. These results suggest that it is possible to block immune evasion domains on herpes simplex virus and that this approach has therapeutic potential and may enhance vaccine efficacy.

Animals↗
PubMed1994

Was exposure to directly antiviral cytokines during primary infection an important selective pressure in the evolution of unique immune evasion strategies by viruses?

Different virus families are characterized by various immune evasion strategies. These viruses have co-evolved with an increasingly sophisticated mammalian immune system which has continually placed pressure on their continued survival. This paper proposes that exposure to directly antiviral cytokines, namely TNF and members of the IFN family, during inflammatory and early immune responses, exerted particularly strong selective pressures on viruses, and has had a critical influence on the development of viral immune evasion strategies and pathogenesis. In the context of antiviral cytokine activity, this report concentrates on two DNA virus families with contrasting pathogenic and immune evasion strategies, namely poxviruses and HSV.

Animals↗
PubMed2026

Multi-omics and spatial transcriptomics reveal that S100A10 drives CD8+ T-cell exhaustion and immune evasion in hepatocellular carcinoma through cPLA2-5-LOX-mediated arachidonic acid metabolism and ferroptosis.

Immune evasion in hepatocellular carcinoma (HCC) represents a major biological barrier limiting the efficacy of immunotherapy, yet its molecular basis remains incompletely understood. Increasing evidence indicates that tumor metabolic reprogramming and ferroptosis-related signaling play critical roles in shaping an immunosuppressive tumor microenvironment (TME); however, the specific regulatory factors involved remain unclear. This study aims to systematically elucidate the functional role of S100 calcium-binding protein A10 (S100A10) in immune evasion in HCC, with a particular focus on the molecular mechanisms by which S100A10 regulates CD8+ T-cell exhaustion through arachidonic acid (AA) metabolism and ferroptosis, as well as its potential therapeutic implications. To this end, data from The Cancer Genome Atlas Liver Hepatocellular Carcinoma (TCGA-LIHC) cohort are integrated to analyze the expression patterns of S100A10, its prognostic value, and its association with the immune microenvironment. S100A10 overexpression and knockout models are established in HCCLM3 and MHCC97L cell lines, and S100A10-mediated metabolic pathway reprogramming is characterized using transcriptomic profiling, untargeted metabolomics, and ferroptosis-related functional assays. In parallel, single-cell RNA sequencing (scRNA-seq) and spatial transcriptomics are employed to delineate the cell-type specificity and spatial distribution of S100A10. Furthermore, human CD8+ T-cell co-culture systems and orthotopic mouse HCC models are used to evaluate the impact of S100A10 on immune function and responsiveness to anti-programmed cell death protein 1 (anti-PD-1) therapy. The results demonstrate that S100A10 is significantly upregulated in HCC and is closely associated with poor prognosis and an immunosuppressive state. Mechanistically, S100A10 activates cytosolic phospholipase A2-arachidonate 5-lipoxygenase (cPLA2-5-LOX)-mediated AA oxidative metabolism, leading to the accumulation of lipid peroxidation products and ferroptosis-associated signals, thereby driving CD8+ T-cell exhaustion and promoting immune evasion. Significantly, inhibition of S100A10 reshapes the tumor immune microenvironment (TIME) and enhances the therapeutic efficacy of anti-PD-1 treatment. Collectively, these findings identify S100A10 as a critical regulator of metabolic-immune coupling in HCC and provide a theoretical basis for combinatorial strategies targeting metabolism and immunotherapy.

Arachidonic acid metabolism↗
PubMed2003

Differential chemokine, chemokine receptor, cytokine and cytokine receptor expression in pulmonary adenocarcinoma: diffuse down-regulation is associated with immune evasion and brain metastasis.

Pulmonary adenocarcinoma is frequently associated with brain metastasis at some stage during the disease course. Host immunity, particularly T cell immunity, plays an important role in the clinicopathological features of carcinoma proliferation and metastasis. Cytokines and chemokines are members of a family of small secreted proteins. The relationships between the cytokines and cytokine receptor (R), and between chemokines and chemokine R are important determinants of selectivity in local immunity. RCAS1 (receptor-binding cancer antigen expressed on SiSo cells) and Fas ligand (FasL) are present in neoplastic cells, induce apoptosis of NK/T cells, and play a role in immune evasion. To investigate differences in host immunity between pulmonary adenocarcinoma with and without brain metastasis, we performed gene expression profiling, using chemokine, chemokine R, cytokine and cytokine R DNA chips. In addition, to assess the extent of immune evasion, we examined the expression of RCAS and FasL. We studied five cases of pulmonary adenocarcinoma with brain metastasis (meta) and five cases without brain metastasis (non-meta). The brain meta cases exhibited diffuse down-regulated profiles, in comparison with normal non-carcinomatous lungs, which were used as controls. Non-meta cases also displayed diffuse down-regulation, however the degree was variable. Expression of RCAS and FasL was detected in almost all cases, but was stronger in meta than non-meta cases. Our findings suggested that tumor cells evaded host immunity. In the gene tree analysis, brain meta cases and non-meta cases exhibited distinct clustering. Brain meta cases exhibited significantly lower expression of interleukin 13 receptor alpha2 (IL-13Ralpha2) than non-meta cases. The reduction of IL-13Ralpha2 expression was confirmed by RT-PCR. Immunohistochemically, non-meta adenocarcinoma cells frequently expressed IL-13Ralpha2, however, IL-13Ralpha2 expression was rare or weak in adenocarcinomas with meta. Our results suggested that, in addition to immune evasion, the characteristics of the adenocarcinoma tumors themselves were important for brain metastasis. However, our study demonstrated the enormous potential of gene expression profiling in clarifying the pathogenesis of brain metastasis in pulmonary adenocarcinoma.

Adenocarcinoma↗
PubMed2001

Multiple mechanisms of immune evasion can coexist in melanoma tumor cell lines derived from the same patient.

Progressive tumor growth may be associated with suppression of the immune response. Many different mechanisms may contribute to immune evasion. We investigated some of these mechanisms in melanoma cells lines generated from two patients. These cell lines show a complex pattern of altered HLA expression; however, the resulting phenotype did not satisfactorily explain the simultaneous evasion of T and NK cell cytotoxicity. Two additional alterations have now been detected in these melanoma cell lines: (1) resistance to FAS-induced apoptosis caused by defective FAS gene expression, and (2) constitutive expression of immunosuppressive cytokines. Our results show that several of the major mechanisms for immune evasion may coexist in a single tumor. This suggests that tumor progression may give rise to an extremely resistant phenotype, which may be an impediment to some immunotherapeutic strategies. We hypothesize that the simultaneous presence of several mechanisms involved in tumor immune evasion must be the result of progressive selection of characteristics that are advantageous for tumor survival in a competent host. Our findings do not support the possibility that FASL expression is a common mechanism of evasion of immune response in melanoma cells.

Apoptosis↗
PubMed2026

Convergent evolution of immune evasion in ESKAPE pathogens: A cross-pathogen architecture of conserved host-defense checkpoints.

Antimicrobial resistance in ESKAPE pathogens is primarily attributed to resistance genes, yet persistent infections despite appropriate therapy implicate immune evasion as an independent driver of treatment failure. Although immune-evasion mechanisms have been extensively characterized in individual pathogens, their shared architecture across the ESKAPE group remains insufficiently integrated. This review synthesizes current evidence to show that phylogenetically diverse ESKAPE pathogens have convergently evolved conserved strategies to evade host immunity under comparable selective pressures. A cross-pathogen immune-evasion framework emerges, encompassing impaired pathogen recognition, complement inhibition, phagocyte dysfunction, immunometabolic reprogramming, biofilm-mediated protection, and persistence-promoting inflammation, together with pathogen-specific virulence mechanisms. These processes intersect with adaptive immune dysfunction and emerging concepts, including quorum-sensing-mediated immunomodulation, trained immunity, and the itaconate-succinate immunometabolic axis, forming an interconnected persistence network rather than isolated virulence traits. This systems-level perspective identifies conserved host-directed therapeutic targets that may complement conventional antimicrobial therapy across species. However, host-directed therapies, immunotherapeutics, and vaccines remain largely preclinical or have shown inconsistent clinical efficacy. Mechanistic evidence is strongest for Staphylococcus aureus, Pseudomonas aeruginosa, and Klebsiella pneumoniae, whereas substantial knowledge gaps persist for Enterococcus faecium, Acinetobacter baumannii, and Enterobacter spp. Overcoming persistent ESKAPE infections will require targeting conserved host-pathogen interactions alongside pathogen-specific antimicrobial resistance mechanisms.

Convergent immune evasion↗
PubMed2001

The multiple immune-evasion genes of murine cytomegalovirus are not redundant: m4 and m152 inhibit antigen presentation in a complementary and cooperative fashion.

Both human cytomegaloviruses (HCMVs) and murine cytomegaloviruses (MCMVs) encode multiple genes that interfere with antigen presentation by major histocompatibility complex (MHC) class I, and thus protect infected targets from lysis by virus-specific cytotoxic T lymphocytes (CTLs). HCMV has been shown to encode four such genes and MCMV to encode two. MCMV m152 blocks the export of class I from a pre-Golgi compartment, and MCMV m6 directs class I to the lysosome for degradation. A third MCMV gene, m4, encodes a glycoprotein which is expressed at the cell surface in association with class I. Here we here show that m4 is a CTL-evasion gene which, unlike previously described immune-evasion genes, inhibited CTLs without blocking class I surface expression. m152 was necessary to block antigen presentation to both K(b)- and D(b)-restricted CTL clones, while m4 was necessary to block presentation only to K(b)-restricted clones. m152 caused complete retention of D(b), but only partial retention of K(b), in a pre-Golgi compartment. Thus, while m152 effectively inhibited D(b)-restricted CTLs, m4 was required to completely inhibit K(b)-restricted CTLs. We propose that cytomegaloviruses encode multiple immune-evasion genes in order to cope with the diversity of class I molecules in outbred host populations.

Animals↗
PubMed2001

Expression dynamics of human cytomegalovirus immune evasion genes US3, US6, and US11 in the blood of lung transplant recipients.

Delayed elimination of human cytomegalovirus (HCMV)-infected cells by the host immune system may contribute to viral dissemination and pathogenesis of HCMV infection. The mRNA expression dynamics of HCMV-encoded immune evasion genes US3, US6, and US11 expressed after active HCMV infection were analyzed in blood samples of lung transplant recipients by means of quantitative nucleic acid sequence-based amplification. The results were compared with the expression dynamics of IE1 mRNA and pp67 late mRNA, levels of pp65 antigenemia, and antiviral treatment. During acute infection, high levels of US3 and US6 RNA were detected before antigenemia, which were detected simultaneously with IE1 RNA. US11 RNA was detected simultaneously with antigenemia but before late pp67 RNA. These data suggest an active role of viral immune evasion during HCMV infection in vivo. Interestingly, immune evasion RNA remained detectable after clinical recovery, often independently of IE1 RNA expression, indicating persistent viral activity, which may have implications for long-term control of HCMV.

Antigens, Viral↗
PubMed2005

Role of immature myeloid cells in mechanisms of immune evasion in cancer.

Tumor affects myelopoiesis by inhibiting the process of differentiation/maturation of antigen-presenting cells from their myeloid precursors and by stimulating an accumulation of immature myeloid cells in cancer patients and tumor-bearing mice. These immature myeloid cells can contribute greatly to tumor progression and promote tumor evasion from immune attack: i) by inhibiting development of adaptive immune responses against tumor in lymphoid organs; ii) by migrating into tumor site and differentiating there into highly immune suppressive tumor-associated macrophages. Immature myeloid cells and tumor-associated macrophages utilize different JAK/STAT signaling pathways and different mechanisms to control T cell responses, which include increased production of TGF-beta, reactive oxygen species, peroxynitrites, as well as enhanced L-arginine metabolism. Understanding of precise mechanisms, which tumors use to affect differentiation of APC from myeloid cell precursors and inhibit T cell responses, could help to develop new approaches for cancer therapy and substantially improve efficiency of existing cancer vaccination strategies.

Animals↗