Introduction:Crimean-Congo hemorrhagic fever virus (CCHFV) is a tick-borne pathogen causing severe hemorrhagic disease with high mortality. The viral glycoprotein Gc mediates membrane fusion and represents a key target of CD8⁺ T-cell responses. However, systematic identification and comprehensive evaluation of pan-MHC-I-restricted Gc epitopes remain limited. Methods:An integrated immunoinformatics workflow incorporating five prediction algorithms (IEDB, NetMHCpan4.1, SMMPMBEC, SYFPEITHI, and Rankpep) was applied to identify high-affinity 9-mer epitopes from the CCHFV Gc protein restricted by human HLA-I and murine H2 alleles. Immunogenicity, conservation, toxicity, and allergenicity were assessed using established computational tools. Peptide-MHC interactions were further examined by molecular docking and molecular dynamics simulations. Selected epitopes were experimentally validated by ELISpot assays in BALB/c and SJL mice immunized with a Gc-based DNA vaccine. Results:Ninety-four human HLA-I and thirty-seven murine H2-restricted dominant epitopes were predicted. Among these, 21 epitopes exhibited high binding affinity, favorable immunogenicity, and broad conservation across viral strains. Most candidates showed low predicted toxicity and allergenicity. Structural analyses supported stable peptide-MHC interactions. ELISpot assays confirmed that several epitopes, including APFILLILF and FVKWKVEYI, elicited significant IL-2 responses, indicating functional T-cell activation. Conclusion:This study provides a systematic framework for identifying conserved and immunogenic pan-MHC-I-restricted epitopes within the CCHFV Gc protein. The validated candidates may support the rational design of multi-epitope vaccines and contribute to understanding cellular immune responses against CCHFV.

Human leukocyte antigen (HLA) plays a pivotal role in immune responses. As a classical HLA-Ia among the HLA molecules, HLA-A*02 activates CD8+ T cells by presenting endogenous antigenic peptides, thereby contributing significantly to antiviral immunity. In contrast, the non-classical HLA-Ib molecule HLA-E regulates immune homeostasis through interactions with the CD94/NKG2 receptor expressed on natural killer (NK) cells. Recent studies have revealed that HLA-E could also present pathogen or tumor-derived antigenic peptides to activate specific CD8+ T cells. Notably, the peptide sequences presented by HLA-E exhibit high similarity to those presented by HLA-A*02, suggesting potential cooperative or competitive mechanisms underlying their involvement in CD8+ T cell-mediated anti-pathogen immune responses. This review systematically compares the structural and functional bases of antigen presentation mechanisms, particularly focusing on their shared capacity to present pathogen-derived epitopes during infectious diseases for HLA-A*02 and HLA-E. We further discussed the roles of their co-presentation phenomenon in host defense and immune homeostasis maintenance. The design of novel peptide vaccines based on the co-presentation of antigenic epitopes by HLA-A*02 and HLA-E may overcome limitations posed by HLA polymorphism, offering a theoretical basis and novel strategies for achieving broader and longer-lasting immune protection.

As a bridge between humoral and cellular immunity in the body, CD4+ T cells play an important role in the clearance of Hantaan virus (HTNV) infection. The envelope-anchored glycoprotein (GP) is responsible for orchestrating host cell entry and fusion. In the bioinformatics stage of this study, we assessed 22 dominant B-cell epitopes and 191 T-cell epitopes (including MHC-I and MHC-II restricted) covering MHC genotype frequencies ≥30% in various regions worldwide, using multiple prediction algorithms and HLA population-frequency criteria. Through affinity analysis and molecular docking, the relationship between nonapeptide determinants and 15-mer epitopes suggested that consecutive CD4+ T-cell epitopes may share a nonapeptide that plays a major binding role in multiple HLA genotypes. Sequence alignment of the reported viral variants showed that affinity changes of non-conserved epitopes were tiny in either humoral or cellular immunity. Toxicity and allergenicity screening identified 23 peptides as safe and available to the body. Based on these bioinformatics predictions, we selected candidate peptides for experimental validation. In the wet-lab stage, specialized immunological assays (ELISA and ELISpot) were performed using human peripheral blood samples from vaccinated volunteers, and anti-HTNV humoral and cellular immune epitopes were validated. The results are strongly representative in a certain population and HLA genotypes. Our research is grounded in HTNV GP and provides a theoretical basis for the use of epitopes in the prevention and control of HTNV. More importantly, studies of T-cell and B-cell epitopes from multiple dimensions and perspectives would further deepen the understanding of peptide-based immunotherapy against emerging viral infections and accelerate the development of global public health services.

Hantaan virus (HTNV) is the predominant causative agent of hemorrhagic fever with renal syndrome (HFRS) in China, yet no specific antiviral therapy is currently available. Neutralizing antibodies (NAbs) represent a promising strategy, but most existing anti-HTNV NAbs are heterologous and carry immunogenicity risks. Here, two fully human antibodies from a previously established human anti-HTNV phage display library were generated and characterized. KJJ3, a VL-VL tandem antibody derived from clone 3–12, showed weak binding to inactivated HTNV and minimal neutralizing activity (IC50 = 27.12 μg/mL). However, KJJ4, an engineered IgG4 antibody derived from clone 4–19 and carrying the S108P hinge mutation to prevent Fab-arm exchange, bound inactivated HTNV antigen and recombinant glycoprotein Gn (residues 19–371) in a dose-dependent manner, with only weak binding to Gc. Surface plasmon resonance yielded an association rate constant of 4.70 × 103 M−1s−1, a dissociation rate constant of 3.06 × 10−3 s−1, and an equilibrium dissociation constant of 650 nM for monomeric Gn19–371. In a Vero E6 focus-reduction microneutralization assay, KJJ4 neutralized HTNV in vitro with an IC50 of 2.879 μg/mL. These data establish KJJ4 as a fully human anti-HTNV antibody with experimentally defined in vitro binding and neutralizing activity, warranting further evaluation in animal models of HTNV infection.

OBJECTIVES:To develop and validate a critical risk prediction model for hemorrhagic fever with renal syndrome caused by Hantaan virus. METHODS:Patients were randomly divided into a training group (n = 344) and a validation group (n = 226). Clinical data were gathered and analyzed. Logistic regression analysis was employed to construct a nomogram-based prediction model, which was subsequently simplified into a novel scoring scale. The calibration curve, receiver operating characteristic curve, and decision curve analysis were used to assess the model's calibration, discrimination, accuracy, and clinical applicability in both the training and validation cohorts. RESULTS:Hypotensive shock, myoglobin, and neutrophils counts were identified as independent predictors of critical risk. Based on these three predictors, a nomogram prediction model was developed and subsequently simplified into a scoring scale. The model demonstrated predictive performance in both the training cohort and the validation cohort (area under the receiver operating characteristic curve >0.8). Furthermore, the calibration of the scoring scale and the nomogram was satisfactory (P >0.05). Decision curve analysis revealed that the model provided significant net clinical benefit within the risk threshold range of 0-90%. CONCLUSIONS:We developed and validated the first prediction model for critically ill hemorrhagic fever with renal syndrome patients, which will aid clinicians in clinical decision-making.

Macrophages’ promotion of mesenchymal stem cell (MSC) homing is important for fracture healing; but mechanisms are unclear. Migrasomes are newly discovered membrane-bound organelles, which, like exosomes, mediate intercellular communication. This study compare macrophage-derived migrasomes and exosomes in directing MSC homing and enhancing fracture healing.Migrasomes and exosomes isolated from polarized M2 and M1 macrpphages were co-cultured with MSCs to test effects on MSC migration. In addition, M2-migra and M2-exo hydrogel delivery systems, with or without the CXCR4 antagonist AMD3100 or poly(lactic-co-glycolic acid) (PLGA)-encapsulated BMP-2, were injected into mice to evaluate their effects on MSC homing and fracture healing. Single-cell RNA sequencing (scRNA-seq) and microarray analyses were used to define mechanisms.M2-migra, but not M2-exo, expressed abundant CXCL12, which activates the CXCL12/CXCR4 axis to promote MSC migration. AMD3100 (a CXCR4 inhibitor) abolishes this migratory effect, confirming the pathway’s specificity. scRNA-seq revealed that M2-migra modulates neutrophil-derived MMP-9 expression, which enhances EphB2 receptor expression on MSCs. This interaction enhances MSC osteogenic differentiation and fracture healing, providing a previously uncharacterized link between migrasomes, immune cells, and MSC function. A PLGA nanoparticle-encapsulated BMP-2 delivery system combined with an M2-migra hydrogel achieved sustained release of bioactive factors, superior MSC homing, and accelerated bone regeneration compared with M2-migra or BMP-2 alone.M2-migra demonstrates superior MSC homing capacity compared with M2-exo through dual mechanisms: CXCL12/CXCR4-mediated recruitment and neutrophil-MMP-9/MSC-EphB2-induced osteogenic differentiation. Moreover, the migrasome-hydrogel system represents a promising tissue-engineering strategy for fracture repair, offering insights into targeted regenerative medicine.

Hydrogels are among the most promising flexible sensing materials, exhibiting extensive applications in wearable devices, human health monitoring, robotics, etc. Currently, hydrogels that are stretchable, self-healing, antifreezing, and conductive have become the focus of research on wearable sensors. However, integrating high tensile strength, self-healing, frost resistance, and satisfactory mechanical properties into a conductive hydrogel remains challenging. Herein, soy hull nanocellulose, graphene oxide, and CaCl2 were integrated into a polyvinyl alcohol-chitosan framework through green physical-crosslinking and ionic-crosslinking methods to build a porous three-dimensional network structure and develop a strong, tough, self-healing, antifreezing, and multifunctional hydrogel. This hydrogel benefits from abundant hydrogen, ester, and metal coordination bonds and electrostatic interactions, which contribute to its exceptional tensile strength (709.48 %), viscoelasticity (1081.71 kPa), mechanical strength (tensile strength = 4.91 MPa and compressive strength = 5.11 MPa), conductivity (5.11 S/m), and frost resistance (-35 degrees C). Moreover, it exhibits high sensitivity with a measurement factor of 7.14 and maintains impressive electrical stability after 800 cycles of stretching at room temperature (25 degrees C) and a low temperature (-35 degrees C). Further, this hydrogel is used for applications such as human limb bending and heart rate monitoring. Overall, this research offers a promising approach for developing sustainable and multifunctional hydrogels as well as provides notable insights with regard to flexible wearable sensors.

Sepsis, a life-threatening condition driven by dysregulated inflammation, remains a major clinical challenge due to high mortality rates and limited therapeutic options. This study investigates the anti-inflammatory properties of Leucoside, a natural flavonoid isolated from tea seed extract, and its potential as a therapeutic agent for sepsis. Using a bacterial infection-induced septic mouse model and lipopolysaccharide (LPS)-activated macrophages, we demonstrated that Leucoside significantly improves survival rates, reduces hypothermia, and attenuates organ damage by suppressing systemic inflammation. Mechanistically, network pharmacology and molecular docking identified Toll-like receptor 4 (TLR4) as a primary target of Leucoside. Biochemical and structural analyses revealed that Leucoside competitively binds to conserved positively charged residues in the B patch of TLR4, specifically Lys263 and Arg337, forming a spatial barrier that inhibits the formation of the myeloid differentiation protein 2 (MD2)-TLR4 complex and subsequent nuclear factor kappa-B (NF-κB) signaling. This inhibition was further validated through co-immunoprecipitation assays, which showed a reduced effect on the TLR4-MD2 complex dissociation when Lys263 and Arg337 were mutated. These findings highlight Leucoside as a novel TLR4 inhibitor with significant potential for treating sepsis and other TLR4-mediated inflammatory diseases. By elucidating its mechanism of action, this study provides a foundation for developing targeted therapies to address the unmet clinical needs in sepsis management.

NK cells could participate in the pathogenesis process of virus infectious diseases through the inhibitory receptor CD94/NKG2A interacting with HLA-E/virus-derived peptide complex. However, the effects and mechanisms of NKG2A-HLA-E axis-mediated NK cell responses in hemorrhagic fever with renal syndrome (HFRS) caused by Hantaan virus (HTNV) infection remain unclear. Single-cell RNA sequencing and flow cytometry were employed to analyze the phenotype and function of different NK cell subsets in HFRS patients. The K562/HLA-E cells binding assay was used for peptide affinity detection. The binding capacity of HLA-E/peptide-CD94/NKG2A was detected using ligand-receptor binding assay and tetramer staining. The cytotoxicity assay of NK cells against peptide-pulsed K562/HLA-E cells was conducted for functional evaluation. In this study, CD56dimCD16+NKG2A+ NK cells were the main subset in HFRS patients, showing activation and proliferation phenotypes with NKG2C-CD57- and the ability to secrete tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ) and cytotoxic mediators. Notably, none of the four identified HTNV epitopes presented by HLA-E could be recognized by CD94/NKG2A on CD56dimNKG2A+ NK cells. Furthermore, the subset of CD56dimNKG2A+ NK cells showed the enhanced cytolytic capacity against HTNV peptide pulsed K562/HLA-E cells ex vivo. Taken together, the findings demonstrate that HTNV-derived peptides presented by HLA-E could "abrogate" the inhibition of CD56dimNKG2A+ NK cells, contributing to the antiviral immune response in HFRS patients.

Marjolin's ulcer (MU) is a rare, aggressive skin tumor. There are numerous case reports but large long-term studies are lacking, necessitating further exploration of its treatment. This study aimed to summarize and analyze the characteristics, treatment methods, and prognosis of MU. We retrospectively analyzed the clinical data of 126 patients with MU, treated between January 2013 and January 2023 at the burn center. Demographic data, clinical characteristics, treatment, and prognosis were statistically analyzed. Of the 126 included patients, 104 were followed up for 0.1-10.2 years. The most common cause of the primary injury was flame burn (50.8%). Lesions were commonly observed on the lower limbs (47.6%). The predominant histopathological type was squamous cell carcinoma (92.8%). Among the 126 patients, 35 (27.8%) presented with bone invasion, 37 (29.4%) presented with enlarged lymph nodes, and 9 (7.1%) had lymph node metastasis. Extensive local excision (83.3%) was the most common surgical procedure; the defect was repaired using skin grafting (41.9%), free flaps (37.1%), and local flaps (21.0%). Multivariate analysis revealed that bone invasion and lymph node involvement were risk factors for postoperative recurrence. Survival analysis showed that age, latency period, pathological type, and recurrence were significant risk factors for survival. Extensive local resection is necessary to eradicate tumors, and patient follow-up should be more frequent within 1 year postoperatively. As MU is preventable, it is essential to reach a quick diagnosis and avoid delayed management before the occurrence of deadly metastases.

During antiviral immunity, MHC‑I molecules display endogenous peptides to CD8+ T‑cell receptors, prompting cytotoxic elimination of infected cells. The present study focused on dominant epitopes derived from the nucleocapsid protein (NP) of Hantaan virus (HTNV) and revealed their high affinity for the HLA‑I and H‑2 superfamilies. Through immunogenicity and conservation analyses, four selective epitopes were precisely identified. Molecular docking validated the binding characteristics of selective epitopes with MHC‑I molecules. Bidirectional hierarchical clustering analysis uncovered complex interaction patterns between NP 9‑mer peptides and MHC‑I haplotypes. Moreover, in‑depth investigation of 11 HTNV variants revealed three amino acid substitutions (I241S, E242A and F384I) within the four selective epitopes; however, these substitutions did not significantly affect the pan‑HLA‑I immunoreactivity of these epitopes. Safety assessments highlighted the potential of four selective epitopes for practical applications. Utilizing ELISpot, ELISA and flow cytometry, the immunogenicity of these selective epitopes was comprehensively confirmed. In summary, the present study thoroughly evaluated the pan‑MHC‑I immunoreactivity of HTNV NP, providing a robust foundation for developing effective epitope vaccines for population immunity.

Hantaan virus (HTNV) triggers an epidemic of hemorrhagic fever with renal syndrome (HFRS), which is predominantly prevalent in Asia. Mucosal-associated invariant T (MAIT) cells, categorized as innate-like T lymphocytes, perform crucial functions in the innate host defense mechanism during virus infection. We previously showed that MAIT cells played antiviral roles in vitro. But marked reduction of MAIT cells was present in the peripheral blood of HFRS patients. Till now, the role of MAIT cells in vivo and the mechanisms of HTNV-induced the MAIT cell deficiency have not yet been fully explored. In this study, by combining the clinical samples, MAIT deficiency mice and in vitro infected MAIT cell models, we find that pyroptosis was the main reason of MAIT cell loss in the peripheral blood of HFRS patients. The molecular mechanisms are related to the overload of calcium in the endoplasmic reticulum (ER) of MAIT cells, which subsequently induces inosital-requiring enzyme-1α (IRE1α)-mediated ER-stress and following pyroptosis. ER-stress inhibitor can reverse the pyroptosis of MAIT cells during HTNV infection. In conclusion, this study firstly reveals the underlying molecular mechanisms for the deficiency of MAIT cells during HTNV infection, and suggests a potential way to stabilize the MAIT cells population in HFRS.

Objective To investigate the phenotypic and functional characteristics of normal human peripheral blood neutrophils. Methods Normal human peripheral blood neutrophils were isolated through density gradient centrifugation followed by red blood cell lysis, and their surface markers and distribution characteristics in different neutrophil subsets were detected using multi-color immunofluorescence staining and flow cytometry. The phagocytic activity of neutrophils was evaluated with pHrodoTM Green E.coli BioParticlesTM. The morphological characteristics of neutrophils undergoing the formation of neutrophil extracellular traps (NET) in vitro were examined via Wright-Giemsa staining and immunofluorescence staining, and were observed using standard light microscopy and confocal microscopy, respectively. Results CD66b, CD11b and CD16 were all highly expressed on normal human peripheral blood neutrophils and the percentage of CD16 positive neutrophils was higher compared to CD11b positive neutrophils. Neutrophils could be classified into three subsets based on the density of CD16 expression: namely, CD16hi neutrophil, CD16int neutrophil and CD16lo neutrophil. The proportion of the CD16hi neutrophil was the highest among the three subsets. The inhibitory molecule programmed cell death ligand 1 (PD-L1) was expressed on all neutrophil subsets without significant differences; however, the expression level of another inhibitory molecule, CD300LD, was markedly higher in the CD16hi neutrophil compared to CD16int or CD16lo neutrophil. Each neutrophil subset demonstrated high levels of adhesion molecule CD62L without notable differences. Notably, the mean fluorescence intensity (MFI) value for pHrodoTM Green E.coli BioParticlesTM in the CD16int neutrophil was the highest among three subsets; and that in CD16hi neutrophil was higher compared to CD16lo neutrophil. Results of Wright-Giemsa staining showed that normal peripheral blood neutrophils typically possessed lobulated nuclei; upon stimulation with phorbol 12-myristate 13-acetate (PMA), the nuclei of these neutrophils formed a network structure while losing their lobulated nuclear morphology. Laser confocal microscopy results showed an increased release of neutrophil elastase (NE) with network formation in neutrophils after PMA stimulation. Conclusions Normal human peripheral blood neutrophils are heterogenous population with different expression of surface marker molecules, which might exert different immune functions. NET formation can be induced by PMA stimulation, and the differences of NET formation in different neutrophil subsets need to be further studied.

We evaluated cellular immune responses induced by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines in an immunized population based on HLA-E-restricted CD8+ T cell epitope identification. HLA-E-restricted SARS-CoV-2 CD8+ T cell nonamer peptides were predicted with software. An HLA-E-transfected K562 cell binding assay was used to screen for high-affinity peptides. IFN-γ enzyme-linked immunospot assays were used to identify HLA-E-restricted epitopes. An HLA-E/epitope tetramer was employed to detect the frequencies of epitope-specific CD8+ T cells. Four CD8+ T cell epitopes on the spike protein of SARS-CoV-2 restricted by both HLA-E*0101 and E*0103 were identified. HLA-E-restricted epitope-specific IFN-γ-secreting CD8+ T cell responses could be detected in individuals vaccinated with SARS-CoV-2 vaccines. Importantly, the frequencies of epitope-specific CD8+ T cells in Ad5-nCoV vaccinated individuals were higher than in individuals vaccinated with recombinant protein or inactivated vaccines. Moreover, the frequencies of epitope-specific CD8+ T cells could be maintained for at least 120 days after only one dose of Ad5-nCoV vaccine, while the frequencies of epitope-specific CD8+ T cells decreased in individuals after two doses of Ad5-nCoV vaccine. These findings may contribute to a more comprehensive evaluation of the protective effects of vaccines for SARS-CoV-2; meanwhile, they may provide information to characterize HLA-E-restricted CD8+ T cell immunity against SARS-CoV-2 infection.

CX3CL1, also named fractalkine or neurotactin, the only known member of the CX3C chemokine family that can chemoattract several immune cells. CX3CL1 exists in both membrane-anchored and soluble forms, each mediating distinct biological activities. CX3CL1 signals are transmitted through its unique receptor, CX3CR1, primarily expressed in microglia of central nervous system (CNS). In the CNS, CX3CL1 acts as a regulator of microglia activation in response to brain disorders or inflammation. Recently, there has been a growing interest in the roles of CX3CL1 in regulating cell adhesion, chemotaxis, and host immune response in viral infection. Here, we provide a comprehensive review of the changes and function of CX3CL1 in various viral infections such as human immunodeficiency virus (HIV), SARS-CoV-2, influenza virus and cytomegalovirus (CMV) infection, to highlight the emerging roles of CX3CL1 in viral infection and the associated diseases.

The Qa-1 in mice is homologous to human leukocyte antigen E(HLA-E), and both of them belong to the non-classical major histocompatibility complex I b(MHC-I b) molecules. Qa-1 is capable of presenting self or exogenous antigen peptides to interact with two distinct receptors, namely T cell receptor (TCR) and natural killer cell group 2 member A (or C) (NKG2A/C), thus playing an important role in immune response and regulation. Qa-1-restricted regulatory CD8+ T cell (CD8+ Treg) is one of the most studied CD8+ Treg subgroups, which can maintain immune homeostasis and autoimmune tolerance by exerting immunosuppressive effects. Consequently, Qa-1-restricted CD8+Treg cells are closely associated with the occurrence and development of various clinical diseases, such as tumors, infections, autoimmune diseases, and transplant rejections. This paper provides a comprehensive review of the phenotypic characteristics, functional effects, regulatory mechanisms of Qa-1-restricted CD8+ Treg cells, as well as the latest research progresses of Qa-1-restricted CD8+ Treg cells involved in the pathogenesis of infectious diseases.

Natural killer (NK) cells directly lysis the virus-infected cells through rapidly releasing cytotoxic mediators and cytokines. The balance between inhibitory and activated receptors on the surface of NK cells, as well as the corresponding ligands expressed on target cells are involved in the regulation of the cytotoxic function of NK cells. NKG2A is one of the highly anticipated inhibitory receptors expressed on NK cells, which can inhibit the cytotoxicity of NK cells to autologous normal tissue cells through interacting with the ligand HLA-E. The studies have shown that HLA-E is overexpressed on virus-infected cells and forms a complex with peptides derived from viral proteins. The interaction of HLA-E and NKG2A can regulate the functions of NK cells, participateing the pathogenesis process of virus infectious diseases. This review outlines the characteristics of the molecular interaction between NKG2A and HLA-E, as well as the mechanisms of NKG2A-HLA-E axis in regulating NK cell responses.

CX3CL1, also named fractalkine or neurotactin, is the only known member of the CX3C chemokine family that can chemoattract several immune cells. CX3CL1 exists in both membrane-anchored and soluble forms, with each mediating distinct biological activities. CX3CL1 signals are transmitted through its unique receptor, CX3CR1, primarily expressed in the microglia of the central nervous system (CNS). In the CNS, CX3CL1 acts as a regulator of microglia activation in response to brain disorders or inflammation. Recently, there has been a growing interest in the role of CX3CL1 in regulating cell adhesion, chemotaxis, and host immune response in viral infection. Here, we provide a comprehensive review of the changes and function of CX3CL1 in various viral infections, such as human immunodeficiency virus (HIV), SARS-CoV-2, influenza virus, and cytomegalovirus (CMV) infection, to highlight the emerging roles of CX3CL1 in viral infection and associated diseases.

Objective To investigate the relationship between disease courses and severity and monocyte subsets distribution and surface CD31 intensity in patients of hemorrhagic fever with renal syndrome (HFRS). Methods Peripheral blood samples from 29 HFRS patients and 13 normal controls were collected. The dynamic changes of classical monocyte subsets (CD14++CD16-), intermediated monocyte subsets (CD14++CD16+) and non-classical monocyte subsets (CD14+CD16++) and the mean fluorescent intensity (MFI) of CD31 on monocyte subsets were detected by multiple-immunofluorescent staining and flow cytometry. Results In acute phase of HFRS, the ratio of classical monocyte subsets to total monocytes was dramatically decreased compared to convalescent phase and normal control. It was still much lower in convalescent phase compared to normal controls. The ratio of classical monocyte subsets to total monocytes were decreased in HFRS patients compared to that in normal control, whereas there was no difference between severe/critical groups and mild/moderate groups. On the contrary, the ratio of intermediate monocyte subsets to total monocytes in acute phase of HFRS was significantly increased compared to convalescent phase and normal control. The ratio of intermediate monocyte subsets to total monocytes were increased in HFRS patients compared to that in normal control, whereas no difference was found between severe/critical groups and mild/moderate groups. Phases or severity groups had no difference in ratio of non-classical monocyte subsets to total monocytes. Additionally, the ratio of classical monocyte subsets had a tendency to decline and that of intermediate monocyte subsets showed an increase both to total monocytes between the acute and convalescent phases in 11 HFRS patients with paired-samples. Moreover, in acute phase of HFRS, the mean fluorescent intensity (MFI) of CD31 on three monocyte subsets all decreased, specifically classical monocyte subsets showed the highest MFI of CD31 while the normal control reported the highest MFI of CD31 in non-classical monocyte subsets. In convalescent phase, the MFI of CD31 on classical and intermediated monocyte subsets were both lower than that of normal control, while MFI of CD31 was still significantly lower than normal control on non-classical monocyte subsets. Finally, MFI of CD31 on classical and intermediated monocyte subsets in severe/critical group were both lower than those in mild/moderate group, showing no statistical difference in MFI of CD31 on non-classical monocyte subset across groups of different disease severity. Conclusion The ratio of classical and intermediated monocyte subsets to total monocytes are correlated with the course of HFRS, and so are the surface intensity of CD31 on these monocyte subsets with the disease course and severity. The surface intensity of CD31 on non-classical monocyte subsets, however, is correlated only with the course of the disease. Together, the underlying mechanisms for the observed changes in monocyte subsets in HFRS patients should be further investigated.