PAMPs/DAMPs as Biomarkers and Therapeutics

The clinical translation of danger signal biology focuses on utilizing these molecules as disease biomarkers and therapeutic targets. Because PAMP and DAMP levels closely reflect tissue damage and immune activation, their quantification in biofluids provides objective readouts of pathological states. Therapeutically, the dual nature of these signals necessitates context‐dependent strategies: inhibiting their activity can mitigate hyperinflammation in sterile injury and autoimmunity, while activating these pathways can help overcome immune tolerance in malignancies and chronic infections.

PAMPs/DAMPs as Clinical Biomarkers

Beyond their role in pathogenesis, PAMPs serve as valuable biomarkers, offering diagnostic precision, prognostic assessment, and therapeutic guidance in specific infectious contexts (Table 1). Invasive fungal infections exemplify this clinical utility: although culture remains the gold standard for diagnosis, its sensitivity is often suboptimal, and results can take days to obtain. Among nonculture‐based methods, (1→3)‐β‐D‐glucan, a conserved pan‐fungal cell wall component, has emerged as the most widely adopted biomarker, demonstrating excellent negative predictive value at an 80 pg/mL threshold in intensive care settings [154, 155]. Serum (1→3)‐β‐D‐glucan also reflects intestinal inflammation in Crohn's disease, as it translocates across compromised mucosal barriers, and thus serves as a noninvasive indicator of disease activity [156]. Bacterial PAMPs have likewise been harnessed through innovative detection platforms; for instance, polymyxin B‐based probes targeting LSP enable selective quantification of circulating outer membrane vesicles via nano‐flow cytometry, facilitating early diagnosis of bacterial infections even before blood cultures turn positive [157]. Viral PAMPs further expand the biomarker repertoire. Circulating HBV RNA, for example, provides a noninvasive surrogate for monitoring the intrahepatic transcriptional reservoir and guiding safe discontinuation of antiviral therapy in chronic hepatitis B [158, 159].

Biomarker name | Disease | Sample | Clinical utility | Detection technique | Reference
β‐D‐glucan | Nondialysis chronic kidney disease | Serum | Treatment response | ELISA | [168]
β‐D‐glucan | Invasive candidiasis | Serum | Treatment response | Chromogenic assay | [169, 170, 171]
Lipoarabinomannan | Tuberculosis | Sputum | Treatment response | ELISA | [172]
Lipopolysaccharides | Gastrointestinal discomfort | Fecal | Treatment response | ELISA | [173]
Lipopolysaccharides | Gastrointestinal syndrome | Plasma | Treatment response | ELISA | [174]
Lipopolysaccharides | Metabolic endotoxemia | Serum | Early diagnosis | ELISA | [175]
Lipopolysaccharides | Obesity | Serum | Treatment response | ELISA | [176]
Lipopolysaccharides | Coronary artery diseases | Serum | Treatment response | ELISA | [177]
Lipopolysaccharides | Gut barrier dysfunction | Serum | Treatment response | ELISA | [178, 179]
Lipopolysaccharides | Abdominal pain | Fecal | Treatment response | ELISA | [180]
Hepatitis B Virus RNA | Chronic hepatitis B | Serum | Treatment response | PCR | [159]
Hepatitis B Virus RNA | Chronic hepatitis B | Serum | Treatment response | PCR | [181]
HIV‐1 RNA | HIV‐1 infection | Plasma | Prognostic prediction, treatment response | PCR | [182]
SARS‐CoV‐2 RNA | COVID‐19 | Plasma | Prognostic prediction, treatment response | PCR | [183]
HMGB1 | Breast cancer | Plasma | Treatment response | ELISA | [184]
HMGB1 | Systemic lupus erythematosus | Urine | Early diagnosis | Flow Cytometry | [185]
HMGB1 | Sepsis | Serum | Treatment response | ELISA | [186]
HMGB1 | Sepsis | Plasma & IP Fluid | Treatment response | ELISA | [187]
mtDNA | Sepsis | Plasma | Prognostic prediction | qPCR | [165]
HMGB1 | Polycystic ovary syndrome (PCOS) | Blood | Early diagnosis, treatment response | ELISA | [188]
HMGB1 | Pneumococcal bacteremia | Sputum | Early diagnosis | ELISA | [189]
HMGB1, HSP70, LL‐37, S100A8 | COPD | Sputum | Early diagnosis | ELISA | [190]
HMGB1, S100A9, LL37 | COPD | Serum | Early diagnosis | ELISA | [191]
HMGB1 | Pneumonia | Serum | Prognostic prediction | ELISA | [192]
HMGB1 | Lung cancer | Lung tissue | Treatment response | ELISA | [193]
HMGB1 | Kidney transplantation | Serum | Prognostic prediction | ELISA | [194]
HMGB1 | ARDS | Serum | Treatment response | ELISA | [195]
HMGB1 | ARDS, MODS | Plasma | Prognostic prediction, treatment response | ELISA | [196]
HMGB1 | Urothelial carcinoma of bladder | Serum | Early diagnosis | ELISA | [161]
HMGB1 | Recurrent ovarian cancer | Plasma | Treatment response | ELISA | [197]
HMGB1 | Liver fibrosis | Serum | Early diagnosis | ELISA | [198]
HMGB1 | Cirrhosis | Serum | Treatment response | ELISA | [199]
HMGB1 | β‐thalassemia major | Serum | Early diagnosis, prognostic prediction | ELISA | [200]
HMGB1 | Parkinson's disease | Serum | Treatment response | ELISA | [201]
HMGB1 | Epilepsy | Serum | Treatment response | ELISA | [202]
HMGB1 | Type 2 diabetes mellitus | Serum | Treatment response | ELISA | [203]
DAMPs (HMGB1, HSP70, mtDNA) | Surgical stress | Plasma | Prognostic prediction | ELISA, qPCR | [204]
HMGB1 | Leiomyosarcoma | Blood | Prognostic prediction | ELISA | [205]
HMGB1 | Acute cerebral infarction | Serum | Treatment response | RT‐qPCR, ELISA | [206]
HMGB1 | Colorectal disease | Plasma | Treatment response | ELISA | [207]
HMGB1 | Unstable angina | Serum | Treatment response | ELISA | [208]
S100A9 | Meibomian gland dysfunction‐related dry eye | Tear | Treatment response | ELISA | [209]
S100A8/9, S100A12 | Polyarticular Juvenile idiopathic arthritis | Serum | Treatment response | ELISA | [210]
S100A8/A9 | Atopic dermatitis | Cheek and antecubital fossa | Early diagnosis | ELISA | [211]
S100A8/A9 | Periprosthetic Joint Infection | Synovial Fluid | Early diagnosis | ionization time‐of‐flight mass spectrometry | [212]
S100A8 | Necrotizing soft‐tissue infections | Plasma | Early diagnosis | Luminex multiplex assays | [213]
S100A8/A9 | Breast cancer | Serum | Prognostic prediction | ELISA | [214]
S100A8/A9 | Acquired aplastic anemia and myelodysplastic syndromes | Plasma | Early diagnosis | ELISA | [215]
S100A8/A9 | Hodgkin lymphoma | Serum | Treatment response | ELISA | [216]
S100A8/A9 | Vasculitis | Serum | Prognostic prediction | ELISA | [217]
S100B | Postoperative brain injury | Serum, plasma | Prognostic prediction | ELISA | [218]
S100A12 | Rheumatoid arthritis | Plasma, synovial tissue | Treatment response | ELISA, immunohistochemistry | [164]
mtDNA | Myocardial infarction | Plasma | Prognostic prediction | qPCR | [219]
mtDNA | Subarachnoid hemorrhage | Serum | Prognostic prediction | qPCR | [220]
mtDNA | Inflamm‐aging | Plasma | Prognostic prediction | [221]
mtDNA | Chronic kidney disease | Serum | Prognostic prediction | RT‐PCR | [222]
mtDNA | SIRS, MODS | Plasma | Prognostic prediction | qPCR | [223]
mtDNA | Sickle cell disease | Plasma | Prognostic prediction | qPCR | [224]
mtDNA | Postoperative pneumonia | Plasma | Prognostic prediction | qPCR | [225]
mtDNA | Colorectal cancer | Plasma | Early diagnosis | qPCR | [226]
mtDNA | Living donor kidney transplantation | Plasma | Prognostic prediction | qPCR | [227]

DAMPs have emerged as premier candidates for biomarker development, owing to their high detectability and quantifiable abundance (Table 1). As endogenously derived molecules released extracellularly, DAMPs readily accumulate in accessible biofluids such as serum, plasma, and synovial fluid, thereby facilitating minimally invasive diagnostic procedures [160]. In clinical practice, DAMPs serve as pivotal indicators for early diagnosis. For instance, HMGB1 has exhibited favorable sensitivity and specificity profiles and demonstrated significant correlations with key clinicopathological parameters, positioning it as a promising diagnostic candidate for early detection of urothelial bladder cancer [161]. In addition, DAMPs facilitate the longitudinal monitoring of disease progression. Elevated circulating S100A8/A9, for example, has been validated as a reliable marker of disease activity in ANCA‐associated vasculitis [162]. Notably, S100A8/A9 has also emerged as a powerful predictor of heart failure following acute myocardial infarction, demonstrating prognostic performance that even surpasses established biomarkers including cardiac troponin I (cTnI), B‐type natriuretic peptide (BNP), and C‐reactive protein (CRP) [163]. Furthermore, DAMPs can predict the efficacy of interventions. A progressive decline in serum S100A12 levels serves as a molecular surrogate for attenuated synovial neutrophil activation, effectively mirroring the success of anti‐inflammatory therapies such as intra‐articular corticosteroid treatment in rheumatoid arthritis [164]. Interestingly, DAMPs exhibit superior diagnostic performance compared with PAMPs in certain contexts. For instance, in early sepsis, cell‐free DNA (cfDNA) predominantly comes from host origin (∼99.86%), whereas microbial‐derived cfDNA (a PAMP) constitutes a negligible fraction (∼0.077%), suggesting that host‐derived DAMPs provide a more robust signal for early detection than pathogen‐derived markers [165].

Despite substantial progress, several methodological limitations complicate the interpretation of DAMP biology. First, conventional detection methods such as ELISA primarily quantify total protein levels and fail to distinguish functionally distinct isoforms governed by posttranslational modifications. This technical shortfall may explain the inconsistent correlations observed between total DAMP concentrations and disease progression in clinical studies [166]. While mass spectrometry remains the gold standard for characterizing posttranslational modifications, such as the critical redox states of HMGB1, its high cost and technical complexity currently render it incompatible with routine diagnostics [166]. Second, once released, certain DAMPs undergo rapid extracellular degradation. Serum HMGB1, for example, exhibits a relatively short half‐life of approximately 11 ± 1 h, with its thiol isoform decaying even more rapidly at 17 ± 1 min [167]. The rapid turnover makes it difficult for accurate diagnosis. Third, circulating DAMP concentrations may not faithfully reflect local tissue events due to dilution effects and enzymatic degradation by nucleases and proteases. DAMPs typically accumulate at high concentrations within damaged tissues, such as bone defects or cirrhotic liver parenchyma, but become substantially diluted or sequestered by clearance receptors upon entering the peripheral circulation. Consequently, peripheral blood measurements may underestimate the true burden of danger signals within the tissue microenvironment, posing a significant challenge for biomarker development and clinical translation.

PAMPs/DAMPs as Therapy Targets

The PAMP/DAMP signaling axis represents a versatile therapeutic target that requires a bi‐directional modulation strategy depending on the specific immunological environment. In hyperinflammatory contexts such as sepsis or autoimmunity, clinical strategies prioritize attenuating these danger signals to quench cytokine storms and prevent systemic organ dysfunction. Conversely, in immune‐silent environments like tumors or chronic infections, therapy focuses on the strategic augmentation of PAMP/DAMP signaling to restore immunological vigilance. In recent years, several therapeutic interventions targeting these pathways have already entered clinical‐phase evaluation across diverse disease models (Table 2). In the following section, we will introduce advances in both aspects (Figure 5).

Therapeutic agent | Clinical indication | Mechanism of action | Molecular target | Clinical trial no. | Trial phase | Reference
CD24Fc | Severe COVID‐19 | Neutralize HMGB1 and HSPs | HMGB1, HSPs | NCT04317040 | Phase III | [228]
CD24Fc | Acute GVHD | Neutralize DAMPs | DAMPs | NCT02663622 | Phase IIa | [229]
Glycyrrhizin | Progressive vitiligo | Inhibit HMGB1 release | HMGB1 | ChiCTR2400085923, ChiCTR2400086844 | Phase II | [230]
DSTAT + azacitidine | AML or MDS | Block HMGB1 | HMGB1 | NCT02995655 | Pilot Study (Phase Ib/II) | [231]
Standard‐volume plasma‐exchange | Acute liver failure | Extracorporeal physical removal of endotoxin and DAMPs | Endotoxin and DAMPs | NCT02718079 | Phase II (RCT) | [232]
DIALIVE | Acute‐on‐chronic liver failure | Extracorporeal removal of endotoxin, inflammasome ligands, and dysfunctional albumin. | Endotoxin, cytokeratin‐18, and inflammasome ligands | NCT03065699 | Phase I (First‐in‐man) | [233]
Efferon LPS Cartridges | Sepsis | Extracorporeal physical removal of PAMPs | LPS | NCT04827407 | Multicenter RCT | [234]
SM17 | Allergic asthma | Blocks IL‐17RB | IL‐17RB | NCT05332834 | Phase I | [235]
Selnoflast | Ulcerative colitis | NLRP3 inhibitor | NLRP3 inflammasome | ISRCTN16847938 | Phase Ib | [236]
DNX‐2401 | Recurrent malignant glioma | Aggregate adaptive immune response by promoting ICD‐triggered DAMPs release | Tumor cell | NCT00805376 | Phase I | [237]
Doxorubicin + dacarbazine + nivolumab | Advanced leiomyosarcoma | Aggregate adaptive immune response by promoting ICD‐triggered DAMPs release | Tumor cell | NCT03277924 | Phase Ib | [205]
Imprime + pembrolizumab | Metastatic TNBC | PAMP‐mediated immune activation | β‐Glucan | NCT02981303 | Phase II | [238]
SpFN/ALFQ vaccine | COVID‐19 | Vaccine with PAMP‐rich adjuvant to induce adaptive immunity | Viral spike protein, MPLA | NCT04784767 | Phase I | [239]

FIGURE 5: Therapeutic modalities targeting the PAMP/DAMP axis through pathological inhibition and immunological harnessing. Inhibition of danger signaling (left) involves a hierarchical approach to quench hyperinflammation: (A) mitigation of release by blocking active secretory pathways or passive membrane leakage; (B) extracellular clearance using molecular scavengers, extracorporeal purification, or antibody‐mediated neutralization; and (C) signaling interruption via selective receptor antagonism and downstream pathway blockade. Harnessing danger signals (right) utilizes these molecules as therapeutic stimuli to revitalize host defenses: (A) innate enhancement through biomaterial‐based PAMP delivery to trigger immediate defense and the induction of trained immunity via metabolic/epigenetic reprogramming of central and peripheral progenitors; and (B) adaptive stimulation by leveraging PAMPs as vaccine adjuvants or triggering immunogenic cell death (ICD) to liberate endogenous DAMPs that license robust T cell‐mediated antitumor immunity.

Inhibition of PAMP/DAMP Activity

Targeted inhibition of excessive PAMP/DAMP signaling represents a pivotal strategy for mitigating hyperinflammation and preventing collateral tissue damage. Current pharmacological research can be concluded at three levels: mitigating the initial release of danger signals, clearing or neutralizing PAMPs/DAMPs, and interrupting downstream receptor engagement or intracellular signaling.

The primary defensive strategy involves sequestering danger molecules within their original compartments. Preventing DAMP release is achievable by modulating either active secretion or passive release. Active secretion pathways can be targeted using endosomal inhibitors. Chloroquine, a well‐tolerated lysosomotropic agent, disrupts endosomal trafficking and subsequent DAMP export, positioning it as a potential therapy following traumatic injury or during early‐stage sepsis [240]. Passive release of DAMPs during regulated cell death can be attenuated by preserving membrane integrity. Ferrostatin‐1 exerts protective effects by inhibiting lipid peroxidation‐induced lytic death, acting upstream of the NINJ1‐mediated membrane rupture pathway to diminish the release of DAMPs and thereby alleviate acute lung injury [241].

Once liberated, circulating danger signals must be rapidly depleted to curtail their pro‐inflammatory effects. Host‐directed clearance utilizing Opsonic peptide 18, a multi‐DAMP scavenger, facilitates the phagocytic engulfment of diverse DAMPs, protecting against ischemia‐reperfusion injury by alleviating inflammation and tissue damage [242]. Comprehensive clearance strategies targeting both PAMPs and DAMPs simultaneously have also been developed. Extracorporeal blood purification techniques aim to remove cytokines, PAMPs, and DAMPs in sepsis [243]. However, basic extracorporeal blood purification lacks the selective clearance of PAMPs and DAMPs. To address this limitation, multitarget strategies such as telodendritic polymer‐based nanotraps (TD‐NTs) have been developed. It utilizes multivalent, charge‐based interactions to selectively capture inflammatory molecules with high efficiency (92%–99%) [244]. Notably, the efficacy of TD‐NT therapy is highly time‐dependent: early depletion may impair essential innate defenses, whereas delayed administration (3–8 h post‐insult) significantly improves survival, especially when combined with antibiotics [244]. Furthermore, RNases and nucleic acid‐binding microfibers enable specialized depletion of DNA‐ and RNA‐containing signals to prevent PRR hyperactivation [245].

Beyond clearance, direct neutralization of bioactive PAMPs and DAMPs has demonstrated therapeutic utility. Neutralization strategies utilize decoys or antibodies to “blind” circulating signals. Pathogen‐specific neutralization is exemplified by TCP‐25, a thrombin‐derived antimicrobial peptide. By sequestering LPS, TCP‐25 prevents CD14 interaction and TLR dimerization, effectively quenching downstream immune activation when delivered via functionalized hydrogels [246]. In bacterial sepsis, monoclonal antibodies targeting flagellin subtypes can restrict systemic dissemination and morbidity [247]. On the host side, S100A4‐neutralizing antibodies (e.g., 6B12) show potency in attenuating fibrosis [248]. However, the potential benefits of broad‐spectrum DAMP inhibition must be carefully calibrated against the risk of excessive immunosuppression. For example, combined blockade of DAMPs like MRP14 and HMGB1 may prove counterproductive [249]. Therefore, host‐directed therapy targeting only one type of DAMP can be sufficient to improve clinical outcomes in specific infectious contexts [249].

The final tier of intervention targets the interface between danger signals and their sensors. Small‐molecule inhibitors like Tasquinimod impede the binding of S100A8/A9 to TLR4 and RAGE, thereby reversing fibrotic phenotypes [138]. To preserve essential host defense, the tetramer P5779 specifically antagonizes the MD‐2/HMGB1 interaction while sparing LPS‐induced signaling, offering protection against sterile injury without compromising pathogen sensing [250]. Direct receptor antagonism, such as the TLR4 antagonist TAK‐242, remains a robust focus for acute inflammatory management [251]. Furthermore, in acute liver injury, blocking calcium release‐activated calcium channels prevents PAMP‐triggered vascular leakage and pulmonary edema by stabilizing the endothelial barrier [252].

Harnessing DAMPs/PAMPs for Therapeutic Benefit

While the predominant therapeutic focus remains on inhibiting PAMP/DAMP‐mediated inflammation, the strategic activation of these pathways offers a powerful approach to overcoming immune tolerance in chronic infections and oncology. This context‐dependent duality allows clinicians to harness innate immune sensing to eliminate persistent pathogen infection or convert immunologically cold tumors into responsive lesions by repurposing ancient danger signatures as potent therapeutic stimuli. These strategies can be broadly categorized based on their primary targets: those enhancing innate immunity (boosting antimicrobial responses and inducing trained immunity) and those potentiating adaptive immunity (augmenting T cell‐mediated responses).

Strategies that harness PAMPs and DAMPs help restore host defense during infection. While the early host response to sepsis is characterized by hyperinflammation, this state is often accompanied by a concurrent failure to eradicate the primary pathogen and a heightened susceptibility to secondary infections [10]. To counteract this immunosuppression, an innovative vaccine technology, ciVAX, has been developed. ciVAX integrates PAMPs from inactivated pathogens, which are captured by an engineered opsonin, into a biomaterial scaffold with GM‐CSF and CpG. This assembly recruits and activates dendritic cells to prevent septic shock and enhance pathogen clearance [253]. In chronic viral management, such as for HBV, synthetic PAMP mimics are utilized to unmask viruses that typically evade host surveillance by maintaining cccDNA “invisibility”. For instance, PAMP mimics (e.g., 5‐triphosphate‐poly‐U/UC RNA) bridge this recognition gap, facilitating an IRF3‐dependent antiviral state that accelerates the decay of viral reservoirs when combined with standard nucleoside analogs [254]. Furthermore, the induction of trained immunity via fungal PAMPs, like chitin, has shown promise. Research found that chitin, a fungal PAMP, promotes the production of TNF‐α and IL‐6 through phagosome acidification, effectively “reprogramming” monocyte‐derived macrophages to enhance their long‐term antibacterial vigilance [255].

In the oncology landscape, the immunostimulatory properties of PAMPs and DAMPs have been extensively exploited, operating through effects on both adaptive immunity and innate immune training. The essential role of PAMPs in adaptive immunity is underscored by observations that cancer vaccination fails to elicit responses in the absence of gut microbiota, implicating microbial PAMPs as requisite co‐stimuli. Specific PRR agonists demonstrate remarkable synergy in the maturation of dendritic cells and in enhancing antigen‐presenting capacity. CpG oligonucleotides (TLR9 ligands) and poly(I:C) (TLR3 ligands) represent well‐characterized examples [256]. This dual‐stimulation approach significantly bolsters CD8+ T cell antitumor efficacy, particularly during periods of metabolic stasis. Bio‐inspired delivery systems, such as bacteria‐derived outer membrane vesicles, exploit the natural PAMP‐rich architecture of microbes to precisely target tumor tissues [257]. These polysaccharide‐ and nucleic acid‐based adjuvants provide the necessary “second signal” for T cell activation while driving metabolic reprogramming of immune cells, ensuring sustained therapeutic responses in vaccine design and glioma models.

Deliberate ICD induction converts the tumor microenvironment from immunosuppressive to immunostimulatory by promoting DAMP release. Gas plasma and gaseous signaling molecules, notably nitric oxide, trigger potent ICD effects through endoplasmic reticulum stress and mitochondrial dysfunction, promoting emission of DAMPs that serve as danger signals and elicit robust immunological protection against tumor rechallenge [258, 259]. Spermidine similarly facilitates DAMP liberation, alleviating immune surveillance and enhancing tumor recognition [260]. Furthermore, nanoscale metal‐organic frameworks (nMOFs) enable the synchronized, in situ delivery of PAMPs alongside liberated tumor antigens and DAMPs, thereby creating a personalized vaccine directly within the TME [261].

Beyond adaptive immunity, PAMPs and DAMPs exert therapeutic effects in oncology through innate immune training. Treatment with β‐glucan engages the Dectin‐1/mTOR/HIF‐1α axis, inducing a metabolic shift that polarizes macrophages toward a pro‐inflammatory M1‐like phenotype and enhances NK cell‐mediated cytotoxicity [262, 263]. This innate memory not only enhances phagocytic clearance of malignant cells but also facilitates the recruitment of mature DCs, thereby bridging the innate‐adaptive divide for comprehensive tumor surveillance [264].