Cells In Infection Research Articles

EXTH-67. ONCOLYTIC ADENOVIRAL INFECTION OF CHORDOMA ACHIEVES TREATMENT EFFICACY THROUGH IMMUNOGENIC CELL DEATH AND TUMOR MICROENVIRONMENT ALTERATION

Abstract Chordomas are locally aggressive neoplasms of the axial skeleton with recurrence rates approaching 40%. Moreover, recurrent chordomas are nearly impossible to eradicate—highlighting an unmet clinical need. Immunotherapeutic approaches, such as immune checkpoint inhibition (ICI), has been a successful tool to modulate the tumor microenvironment (TME) towards a pro-inflammatory, antitumor state. There is emerging interest in exploring immunomodulatory agents for chordomas. Oncolytic viral (OV) therapy uses genetically modified viruses which selectively replicate in tumor cells, mediate tumor cell lysis, and initiate a pro-inflammatory response within the infected TME. These findings suggest that OV therapy may be a clinically relevant, novel immunotherapeutic approach for chordoma. Using the replicating oncolytic adenovirus Delta-24-RGD, we investigate the efficacy of chordoma treatment using in vitro approaches, ex vivo bone scaffolds, and in vivo murine models. Additionally, we explore the underlying mechanism of OV cytotoxicity, immunogenic cell death, Brachyury modulation, and reshaping of the TME towards a pro-inflammatory state. Across a panel of human chordoma cell lines, Delta-24-RGD achieved viral infectivity, oncolysis and immunogenic cell death. This treatment response was similarly demonstrated in chordoma cultured in bone scaffold models. Delta-24-RGD infection was associated with concomitant Brachyury downregulation within both infected and uninfected chordoma cells in vitro, suggesting a pleiotropic effect following oncolytic viral infection. In vivo models of CH22 chordoma treated with Delta-24-RGD demonstrated shrinkage in tumor volume and enhanced overall survival. Utilizing a human chordoma tissue microarray, the immunosuppressive macrophage marker CD163 was associated with shortened recurrence free survival. Using macrophage/chordoma co-culture, Delta-24-RGD infection achieved a reduction in macrophage expression of CD163. Taken together, Delta-24-RGD demonstrated efficacy in multiple models of chordoma including mice bearing CH22 tumors. The chordoma TME is associated with clinical outcomes and Delta-24-RGD infection reverses a deleterious immunosuppressive immune profile. These studies provide a framework for future clinical trial implementation for patients with metastatic or recurrent chordoma.

Assessment of P16 and Ki-67 Proteins Immunoexpressing in Oral Mucosa Among Saudi Smokers.

It is widely known that tobacco use significantly contributes to a variety of health problems, including mouth cancer. The proteins P16 and Ki-67 have a role in regulating the cell cycle and promoting cell growth. Analyzing the levels of these proteins can give us valuable information about the overall health of cells. This study aims to assess the cellular alterations and immunohistochemical expression of P16 and Ki-67 in the oral mucosa of Saudi smokers. From March to December 2023, a cross-sectional study scraped 500 samples from the buccal mucosa. Participants in the study were Saudi citizens of both genders. We selected a total of 300 individuals who smoked cigarettes and 200 individuals who did not smoke tobacco as the control group. The selection process involved two sample techniques: initially purposive sampling and subsequently snowball sampling. The samples underwent an immunohistochemical examination to determine the presence of P16 and Ki-67 protein overexpression. We evaluated the samples by assessing the proportion of cells that exhibited positive staining and the intensity of the staining. The data were examined utilizing SPSS. We identified categorical variables by calculating frequencies and percentages using the chi-squared test. A significance level of p < 0.05 was used to determine statistical significance. A total of 48% of cigarette users had abnormal results, compared to 20% of nonsmokers. These abnormalities included cytological atypia, inflammation, reverse cytological infection, and binucleated or multinucleated cells (p = 0.015). People who smoked had higher levels of P16 and Ki-67 expressions than people who did not smoke, 12% and 5%, respectively (p = 0.042). There were no important changes in P16/Ki-67 expression between participants of different ages (p = 0.68) or between men and women (p = 0.27). These results demonstrate the detrimental effects of smoking on cell health, underscoring the importance of quitting to reduce the risk of cytological abnormalities and related diseases. Smokers have higher levels of the proteins P16 and Ki-67, which shows how important these biomarkers are for understanding the risks to oral health.

HCMV strain- and cell type-specific alterations in membrane contact sites point to the convergent regulation of organelle remodeling.

Viruses are ubiquitous entities that infect organisms across the kingdoms of life. While viruses can infect a range of cells, tissues, and organisms, this aspect is often not explored in cell culture analyses. There is limited information about which infection-induced changes are shared or distinct in different cellular environments. The prevalent pathogen human cytomegalovirus (HCMV) remodels the structure and function of subcellular organelles and their interconnected networks formed by membrane contact sites (MCSs). A large portion of this knowledge has been derived from fibroblasts infected with a lab-adapted HCMV strain. Here, we assess strain- and cell type-specific alterations in MCSs and organelle remodeling induced by HCMV. Integrating quantitative mass spectrometry, super-resolution microscopy, and molecular virology assays, we compare infections with lab-adapted and low-passage HCMV strains in fibroblast and epithelial cells. We determine that, despite baseline proteome disparities between uninfected fibroblast and epithelial cells, infection induces convergent changes and is remarkably similar. We show that hallmarks of HCMV infection in fibroblasts, mitochondria-endoplasmic reticulum (ER) encapsulations and peroxisome proliferation, are also conserved in infected epithelial and macrophage-like cells. Exploring cell type-specific differences, we demonstrate that fibroblasts rely on endosomal cholesterol transport while epithelial cells rely on cholesterol from the Golgi. Despite these mechanistic differences, infections in both cell types result in phenotypically similar cholesterol accumulation at the viral assembly complex. Our findings highlight the adaptability of HCMV, in that infections can be tailored to the initial cell state by inducing both shared and unique proteome alterations, ultimately promoting a unified pro-viral environment.IMPORTANCEHuman cytomegalovirus (HCMV) establishes infections in diverse cell types throughout the body and is connected to a litany of diseases associated with each of these tissues. However, it is still not fully understood how HCMV replication varies in distinct cell types. Here, we compare HCMV replication with lab-adapted and low-passage strains in two primary sites of infection, lung fibroblasts and retinal epithelial cells. We discover that, despite displaying disparate protein compositions prior to infection, these cell types undergo convergent alterations upon HCMV infection, reaching a more similar cellular state late in infection. We find that remodeling of the subcellular landscape is a pervasive feature of HCMV infection, through alterations to both organelle structure-function and the interconnected networks they form via membrane contact sites. Our findings show how HCMV infection in different cell types induces both shared and divergent changes to cellular processes, ultimately leading to a more unified state.

Hyperexpression of PTAFR and PF4 as Possible Platelet Risk Biomarkers in Patients With COVID-19.

SARS-CoV-2 infection presents different severity levels that suggest the influence of genetic factors on the clinical outcome of the disease. In cases of severe COVID-19, the presence of elevated coagulation markers, increased platelet activation and aggregation and the risk of thrombotic complications are described. Given the participation of these cells in several serious viral infections and their negative role when associated with a prothrombotic response, it is important to understand the mechanistic role of SARS-CoV-2 in platelet physiology. This study evaluated the hyperexpression of platelet-activating factor receptor (PTAFR) and platelet factor 4 (PF4) in unvaccinated and hospitalized patients with COVID-19. The study included 43 COVID-19 patients stratified according to WHO guidelines. Subsequently, the expression of the PTAFR and PF4 genes were evaluated using the real-time quantitative PCR and their possible correlation with the severity of the disease and clinical variables including hospitalization, outcome, sex, age and laboratory parameters (platelet count, INR and D-dimer). The analysis demonstrated a significant (p<0.05) hyperexpression of these genes COVID-19 patients (n=43) compared to healthy controls. Expression of these genes in patients was not statistically significant (p>0.05) different between patients stratified according to clinical variables. The expression of PTAFR and PF4 suggests an important molecular pathway in the pathophysiology of the disease and may be valuable platelet biomarkers to indicate increased risk in patients with COVID-19 who require hospital care, contributing to personalized intervention strategies and improving their clinical management.

Gastrointestinal germinal center B cell depletion and reduction in IgA+ plasma cells in HIV-1 infection.

Gastrointestinal (GI) B cells and plasma cells (PCs) are critical to mucosal homeostasis and the host response to HIV-1 infection. Here, high-resolution mapping of human B cells and PCs sampled from the colon and ileum during both viremic and suppressed HIV-1 infection identified a reduction in germinal center (GC) B cells and follicular dendritic cells (FDCs) during HIV-1 viremia. Immunoglobulin A-positive (IgA+) PCs are the major cellular output of intestinal GCs and were significantly reduced during viremic HIV-1 infection. PC-associated transcriptional perturbations, including type I interferon signaling, persisted in antiretroviral therapy (ART)-treated individuals, suggesting ongoing disruption of the intestinal immune milieu during ART. GI humoral immune perturbations were associated with changes in the intestinal microbiome composition and systemic inflammation. These findings highlight a key immune defect in the GI mucosa due to HIV-1 viremia.

Virus-specific Th17 Cells Are Induced by Human Cytomegalovirus after Renal Transplantation.

CMV infection and Th17 cells are independently associated with increased risk for late allograft loss after renal transplantation. Although CMV-specific Th17 cells are detectable in animal models and nontransplant clinical populations, evidence linking CMV and Th17 cells after renal transplantation remains unclear. This prospective observational study evaluated a cohort of renal transplant recipients during 12 mo posttransplant to assess the presence of CMV-specific Th17 cells in peripheral blood and their relationship to pretransplant CMV serostatus and CMV DNAemia. CMV-specific Th17 cells were identified among CMV serostatus donor (D)+ and/or recipient (R)+ recipients and expanded during both primary (D+/R-) and reactivated (D+/R+, D-/R+) CMV DNAemia. A subset of CMV-specific Th17 cells coexpressed IFN-γ, indicating a Th1/17 phenotype. These Th17 and Th1/17 cells expressed CCR6, CCR5, activation and terminal differentiation markers (CD95, OX40, HLA-DR, CD57), and a central/effector memory phenotype. CMV-specific Th1/17 cells expressed activating/inhibitory receptors (CD57, 4-1BB, CD160, CTLA-4, PD-1) at higher frequencies than Th17 cells. In contrast, staphylococcal enterotoxin B-induced Th17 cells did not expand during CMV DNAemia, did not differ between CMV serostatus groups over time, expressed CCR6, predominantly coexpressed TNF-α, and had lower expression of activating and inhibitory receptors than pp65-specific Th17 and Th1/17 cells. These data show that CMV-specific Th17 cells expand during episodes of CMV DNAemia among renal transplant recipients, and that these virus-specific Th17 and Th1/17 cells have distinct phenotypes from global circulating Th(1)/17 cells. These results suggest a potential proinflammatory pathway by which CMV-induced Th17 cells may contribute to allograft injury, increasing risk for late allograft loss.

Gastrointestinal germinal center B cell depletion and reduction in IgA + plasma cells in HIV-1 infection.

Intestinal germinal center B cell reduction in HIV-1 infection linked to reduced IgA + plasma cells and systemic inflammation.

Focused Insights into Liposomal Nanotherapeutics for Antimicrobial Treatment.

Addressing infectious conditions presents a formidable challenge, primarily due to the escalating issue of bacterial resistance. This, coupled with limited financial resources and stagnant antibiotic research, compounds the antibiotic crisis. Innovative strategies, including novel antibiotic development and alternative solutions, are crucial to combat microbial resistance. Nanotherapeutics offers a promising approach to enhance drug delivery systems. Integration into lipid-based nanoscale delivery systems, particularly through therapeutic substance encapsulation in liposomal carriers, significantly prolongs drug presence at infection sites. This not only reduces toxicity but also shields antibiotics from degradation. Lipidic carriers, particularly liposomes, exhibit remarkable specificity in targeting infectious cells. This holds great promise in combating antimicrobial resistance and potentially transforming treatment for multi-drug resistant infections. Leveraging liposomal carriers may lead to breakthroughs in addressing drugresistant bacterial infections. This review emphasizes the potential of antimicrobial-loaded liposomes as a novel delivery system for bacterial infections. Encapsulating antimicrobial agents within liposomes enhances treatment efficiency. Moreover, liposomal systems counteract challenges posed by antimicrobial resistance, offering hope in managing persistent multidrug-resistant infections. In the battle against bacterial resistance and the antibiotics crisis, the use of antimicrobial-loaded liposomes as delivery vehicles shows great promise. This innovative approach not only extends drug effectiveness and reduces toxicity but also provides a path to address highly resistant infectious conditions. As research advances, liposomal nanotherapeutics may emerge as a transformative solution in the fight against bacterial infections.

Enhanced Oncolytic Potential of Engineered Newcastle Disease Virus Lasota Strain through Modification of Its F Protein Cleavage Site.

Newcastle disease virus (NDV) is an oncolytic virus whose F protein cleavage activity is associated with viral infectivity. To explore the potential of modifying F protein cleavage activity to enhance antitumor effects, we constructed a recombinant NDV LaSota strain by replacing its F protein cleavage site with that from the mesogenic Beaudette C (BC) strain using reverse genetics techniques. The resulting virus, rLaSota-BC-RFP, demonstrated significantly enhanced infectivity and tumor cell suppression on the murine melanoma B16F10 cell, characterized by higher cytotoxicity and increased apoptosis compared to its parental strain, rLaSota-RFP. In vivo, rLaSota-BC-RFP treatment of B16F10 tumors in C57BL/6 mice resulted in significant tumor growth inhibition, improved survival rate, and induction of tumor-specific apoptosis and necrosis. Additionally, the rLaSota-BC-RFP treatment enhanced immunostimulatory effects within the tumor microenvironment (TME), characterized by increased infiltration of CD4+ and CD8+ T cells and elevated levels of antitumor immune modulator cytokines, including mouse IL-12, IFN-γ, IL-15, and TNF-α, in the rLaSota-BC-RFP-treated tumor tissues. Collectively, these findings demonstrate that the mesogenic F protein cleavage site enhances the oncolytic potential of the NDV LaSota strain, suggesting that rLaSota-BC-RFP is a promising oncolytic viral vector for gene delivery in cancer immunotherapy.

Neutralisation resistance of SARS-CoV-2 spike-variants is primarily mediated by synergistic receptor binding domain substitutions

ABSTRACT The evolution of SARS-CoV-2 has led to the emergence of numerous variants of concern (VOCs), marked by changes in the viral spike glycoprotein, the primary target for neutralising antibody (nAb) responses. Emerging VOCs, particularly omicron sub-lineages, show resistance to nAbs induced by prior infection or vaccination. The precise spike protein changes contributing to this resistance remain unclear in infectious cell culture systems. In the present study, a large panel of infectious SARS-CoV-2 mutant viruses, each with spike protein changes found in VOCs, including omicron JN.1 and its derivatives KP.2 and KP.3, was generated using a reverse genetic system. The susceptibility of these viruses to antibody neutralisation was measured using plasma from convalescent and vaccinated individuals. Synergistic roles of combined substitutions in the spike receptor binding domain (RBD) were observed in neutralisation resistance. However, recombinant viruses with the entire spike protein from a specific VOC showed enhanced resistance, indicating that changes outside the RBD are also significant. In silico analyses of spike antibody epitopes suggested that changes in neutralisation could be due to altered antibody binding affinities. Assessing ACE2 usage for entry through anti-ACE2 antibody blocking and ACE2 siRNA revealed that omicron BA.2.86 and JN.1 mutant viruses were less dependent on ACE2 for entry. However, surface plasmon resonance analysis showed increased affinity for ACE2 for both BA.2.86 and JN.1 compared to the ancestral spike. This detailed analysis of specific changes in the SARS-CoV-2 spike enhances understanding of coronavirus evolution, particularly regarding neutralising antibody evasion and ACE2 entry receptor dependence.

Two plant membrane-shaping reticulon-like proteins play contrasting complex roles in turnip mosaic virus infection.

Positive-sense RNA viruses remodel cellular cytoplasmic membranes as the membranous sources for the formation of viral replication organelles (VROs) for viral genome replication. In plants, they traffic through plasmodesmata (PD), plasma membrane-lined pores enabling cytoplasmic connections between cells for intercellular movement and systemic infection. In this study, we employed turnip mosaic virus (TuMV), a plant RNA virus to investigate the involvement of RTNLB3 and RTNLB6, two ER (endoplasmic reticulum) membrane-bending, PD-located reticulon-like (RTNL) non-metazoan group B proteins (RTNLBs) in viral infection. We show that RTNLB3 interacts with TuMV 6K2 integral membrane protein and RTNLB6 binds to TuMV coat protein (CP). Knockdown of RTNLB3 promoted viral infection, whereas downregulation of RTNLB6 restricted viral infection, suggesting that these two RTNLs play contrasting roles in TuMV infection. We further demonstrate that RTNLB3 targets the α-helix motif 42LRKSM46 of 6K2 to interrupt 6K2 self-interactions and compromise 6K2-induced VRO formation. Moreover, overexpression of AtRTNLB3 apparently promoted the selective degradation of the ER and ER-associated protein calnexin, but not 6K2. Intriguingly, mutation of the α-helix motif of 6K2 that is required for induction of VROs severely affected 6K2 stability and abolished TuMV infection. Thus, RTNLB3 attenuates TuMV replication, probably through the suppression of 6K2 function. We also show that RTNLB6 promotes viral intercellular movement but does not affect viral replication. Therefore, the proviral role of RTNLB6 is probably by enhancing viral cell-to-cell trafficking. Taken together, our data demonstrate that RTNL family proteins may play diverse complex, even opposite, roles in viral infection in plants.

Method to Assess Immunosenescent CD8+ T Cells in Respiratory Viral Infections.

Immunosenescence is a well-characterized phenomenon that occurs with increasing age in all immune and somatic cells. In order to best study immunosenescence, it is imperative to develop methods to accurately identify immunosenescent cells. Elderly patients are known to have impaired immune responses to respiratory viruses, and it is hypothesized that this is due, in part, to immunosenescent, terminally exhausted CD8+ T cells. To test this hypothesis, we developed an aged mouse model and a flow cytometry protocol using the Cytek® Aurora to assess the CD8+ T-cell response during respiratory viral infection and identify immunosenescent CD8+ T cells. This protocol and our aged mouse model have great potential to be incredibly valuable for future studies elucidating how to rejuvenate and possibly reverse immunosenescent CD8+ T cells, which could improve the immune response to respiratory viruses in this at-risk population.

Dielectric Signatures of Late Carcinoma Immune Cells Using MMTV-PyMT Mammary Carcinoma Models.

Peripheral blood mononuclear cells (PBMCs) are specialized immune cells produced from hematopoietic stem cells (HSC). They actively surveil for any signs of infection, foreign invaders, and abnormal or aberrant cells associated with diseases. Numerous inherent interactions between PBMCs and proliferating cancer cells facilitate cellular communication, inducing alterations in the composition of the PBMCs. These subtle alterations can be detected by using dielectrophoresis (DEP). The ultimate objective is to apply this knowledge in a clinical setting to achieve noninvasive early detection of breast cancer while minimizing the occurrence of false positives and negatives commonly associated with standard screening methods like mammography. To realize our long-term goal, we are probing the dielectric properties of the PBMCs from FVB/N MMTV-PyMT+ (late carcinoma, PyMT+ PBMC) and FVB/N (wild-type, WT-PBMC) age-matched mice at 14+ weeks using dielectrophoresis on a microfluidic platform. The central hypothesis of this research is that the changes triggered in the subcellular components, such as the cytoskeleton, lipid bilayer membrane, cytoplasm, focal adhesion proteins, and extracellular matrix (ECM) at the onset of carcinoma, regulate dielectric properties (conductivity, σ; and permittivity, ε), thus affecting the bioelectric signals that aid in the detection of breast cancer. The ANOVA results suggest a significant difference in PyMT+ PBMCs crossover frequencies at 0.01 and 0.05 S/m medium conductivity levels. Post hoc pairwise analysis of WT-PBMCs showed that the crossover frequencies are distinct across the medium conductivity ranges from 0.01 to 0.05 S/m. This study revealed that on average, PyMT+ PBMCs have increased crossover frequency, polarizability, higher membrane capacitance, and a folding factor compared with the age-matched wild-type PBMCs.

The unappreciated role of developing B cells in chronic gammaherpesvirus infections

The unappreciated role of developing B cells in chronic gammaherpesvirus infections

Epigenetic tuning of PD-1 expression improves exhausted T cell function and viral control.

PD-1 is a key negative regulator of CD8+ T cell activation and is highly expressed by exhausted T cells in cancer and chronic viral infection. Although PD-1 blockade can improve viral and tumor control, physiological PD-1 expression prevents immunopathology and improves memory formation. The mechanisms driving high PD-1 expression in exhaustion are not well understood and could be critical to disentangling its beneficial and detrimental effects. Here, we functionally interrogated the epigenetic regulation of PD-1 using a mouse model with deletion of an exhaustion-specific PD-1 enhancer. Enhancer deletion exclusively alters PD-1 expression in CD8+ T cells in chronic infection, creating a 'sweet spot' of intermediate expression where T cell function is optimized compared to wild-type and Pdcd1-knockout cells. This permits improved control of chronic infection without additional immunopathology. Together, these results demonstrate that tuning PD-1 via epigenetic editing can reduce CD8+ T cell dysfunction while avoiding excess immunopathology.

Research progress on T-cell immunity in patients infected with SARS-CoV-2

Patients with SARS-CoV-2 infection often exhibit significant changes in T cells, particularly a reduction in CD4+T and CD8+T cells in peripheral blood, which has become a key feature of severe respiratory infection. These immune changes in T lymphocytes are closely associated with disease progression, but the specific mechanisms remain unclear and warrant further investigation. This paper reviewed the changes in the number and function of T cells in respiratory viral infections, with a focus on SARS-CoV-2, and summarized related therapeutic explorations. We believe that improving and enhancing the number and function of T lymphocytes in infected hosts is a promising strategy for the treatment of respiratory viral infections, although more systematic and in-depth scientific research is still needed.

From foes to friends; bacterial proteins for optimal wart cryotherapy

Warts are a common skin complaint caused by viral infections. Cryotherapy is a well-established approach for wart removal, which apply low temperatures to freeze and destroy infectious cells. However, this process may face-up several unwanted side effect on healthy nearby tissues. Besides, proper penetration of such temperature is also required to cause irreversible damages in deep-root infectious layers. In this respect, ice-producing proteins that are naturally found in some bacterial species, knowing as ice nucleation active (INA) bacteria, may be practical. In the current work, we hypothesized purification and encapsulation of these proteins into vesicular lipid particles (such as liposomes, niosomes, and exosomes) for an intralesional injection. Thereby, effective wart removal would be achieved even at low temperatures without undesirable effects.

Role of HLA-B*58:01-restricted CD8+ T cells in HIV-1 subtype AE infection

Abstract HLA-B*58:01 and HLA-B*57 are protective alleles against HIV-1 subtype B or C infection whereas these HLA alleles have not been reported as protective in HIV-1 subtype AE infection. Although HLA-B*58:01-restricted and HLA-B*57-restricted HIV-1-specific CD8+ T cells have been thoroughly analyzed in subtype B or C infection, they have only been partially analyzed in subtype AE infection. We identified six HLA-B*58:01-restricted subtype AE epitopes in Vietnamese individuals infected with subtype AE. HLA-B*58:01-restricted T-cell responses to Gag epitopes, which may control disease progression in HLA-B*58:01+ and HLA-B*57+ individuals infected with subtype B or C, were not protective in subtype AE infection. These findings suggest that the loss of HLA-B*58:01-restricted T cells specific for some Gag epitopes and/or their reduced ability may account for the lack of protective effects conferred by HLA-B*58:01 in subtype AE infection.

Depletion of monocytic myeloid-derived suppressor cells in LP-BM5 murine retroviral infection has a positive impact on virus-induced host immunodeficiency

We have shown the induction of CD11b+Ly6C+ monocytic myeloid-derived suppressor cells (M-MDSCs) during infection of B6 mice by LP-BM5 immunodeficiency-inducing retrovirus. We published that the molecular mechanisms of these M-MDSCs vary, and depend on the cell type targeted by the suppression –defined by use of biochemical inhibitors, mouse M-MDSCs knock-out strains and blocking antibodies. These M-MDSCs suppressed proliferation and function of T cells, via nitric oxide synthase/nitric oxide; and that of B cells, ∼50% via INOS/NO along with the negative checkpoint regulator VISTA, reactive nitrogen and oxygen species, and other soluble mediators. Here, LP-BM5 infected mice were treated weekly with 5-Fluorouracil (5-FU), resulting in depletion of peripheral blood and splenic M-MDSCs, reduced MDSC activity, and significantly decreased standard disease parameters of: splenomegaly, impaired B-and T-cell ex vivo polyclonal responses, and viral load. In addition, 5-FU treatment significantly increased percentages of CD4+ and CD8+ T cells.

Research Advances on Natural Killer Cells in Infections

Natural killer (NK) cells play a crucial role in the human immune system, swiftly recognizing and eliminating infected cells through non-specific immune mechanisms. This paper reviews the mechanisms by which NK cells act in various infections, including those caused by viruses, bacteria, parasites, and fungi, and explores their biological characteristics and functional regulation in the context of infection. By thoroughly analyzing the regulatory mechanisms of cytokines, receptor-ligand interactions, and the microenvironment on NK cell function, this paper further elucidates the response mechanisms of NK cells under different infection scenarios. Finally, it discusses the clinical application prospects of NK cells in treating infectious diseases and outlines future research directions, providing new ideas and possibilities for NK cell-based immunotherapy strategies.