{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,27]],"date-time":"2026-03-27T12:07:19Z","timestamp":1774613239321,"version":"3.50.1"},"reference-count":44,"publisher":"MDPI AG","issue":"4","license":[{"start":{"date-parts":[[2026,3,27]],"date-time":"2026-03-27T00:00:00Z","timestamp":1774569600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Prevention and Control of Emerging and Major Infectious Diseases-National Science and Technology Major Project","award":["2025ZD01904000"],"award-info":[{"award-number":["2025ZD01904000"]}]},{"name":"Prevention and Control of Emerging and Major Infectious Diseases-National Science and Technology Major Project","award":["2025ZD01907500"],"award-info":[{"award-number":["2025ZD01907500"]}]},{"name":"Shanghai Municipal Science and Technology Major Project","award":["ZD2021CY001"],"award-info":[{"award-number":["ZD2021CY001"]}]},{"name":"National Natural and Science Foundation of China\n\t\t\t\t\t\t\t\t\t\t\t\t              https:\/\/ror.org\/01h0zpd94","award":["32470998"],"award-info":[{"award-number":["32470998"]}]},{"name":"National Natural and Science Foundation of China\n\t\t\t\t\t\t\t\t\t\t\t\t              https:\/\/ror.org\/01h0zpd94","award":["32394014"],"award-info":[{"award-number":["32394014"]}]},{"DOI":"10.13039\/501100007279","name":"Shanghai Municipal Health Bureau","doi-asserted-by":"publisher","award":["2024ZZ1029"],"award-info":[{"award-number":["2024ZZ1029"]}],"id":[{"id":"10.13039\/501100007279","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100007279","name":"Shanghai Municipal Health Bureau","doi-asserted-by":"publisher","award":["2022XD060"],"award-info":[{"award-number":["2022XD060"]}],"id":[{"id":"10.13039\/501100007279","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Vaccines"],"abstract":"<jats:p>Background: Infections caused by multidrug-resistant bacteria and inadequate vaccine coverage against opportunistic pathogens highlight the need for interventions that broadly and durably enhance host defense beyond antigen-specific adaptive immunity. Trained immunity, driven by metabolic and epigenetic reprogramming of innate immune cells, has been predominantly characterized using Bacille Calmette\u2013Gu\u00e9rin and \u03b2-glucan, whereas its induction by Gram-negative bacteria remains poorly defined. To address this gap, we aimed to determine whether heat-killed Klebsiella pneumoniae (HK Kp) induces trained immunity through metabolic and hematopoietic reprogramming to confer heterologous antibacterial protection. Methods: HK Kp-trained murine bone marrow-derived macrophages and HK Kp-immunized C57BL\/6 mice were employed to interrogate functional, metabolic, and transcriptomic reprogramming in vitro, hematopoietic progenitor remodeling in vivo, and protective efficacy against systemic Salmonella Typhimurium and Staphylococcus aureus infection. Results: HK Kp-trained macrophages showed markedly enhanced IL-1\u03b2 secretion across all restimulation conditions, stimulus-dependent amplification of TNF-\u03b1 responses, increased phagocytosis, and improved intracellular control of S. typhimurium, together with sustained upregulation of the glycolytic enzymes-encoding genes Hk2 and Pfkfb3. Transcriptomic profiling revealed extensive reprogramming enriched in glycolysis\/gluconeogenesis and hematopoietic cell lineage pathways. In vivo, HK Kp immunization shifted bone marrow stem\/progenitor compartments toward a myeloid-biased state. HK Kp-trained mice challenged with lethal S. typhimurium or S. aureus exhibited less weight loss, improved survival rates, and reduced bacterial burdens. Conclusions: Inactivated K. pneumoniae orchestrates metabolic and hematopoietic reprogramming to establish enhanced innate immune responsiveness and confer heterologous protection in murine S. typhimurium and S. aureus sepsis models, supporting its potential as a potent inducer of trained immunity. These findings establish HK Kp-based trained immunity as a promising strategy for combating multidrug-resistant and vaccine-evading pathogens.<\/jats:p>","DOI":"10.3390\/vaccines14040300","type":"journal-article","created":{"date-parts":[[2026,3,27]],"date-time":"2026-03-27T11:12:25Z","timestamp":1774609945000},"page":"300","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Inactivated Klebsiella pneumoniae Induces Metabolic and Hematopoietic Reprogramming to Promote Trained Immunity and Heterologous Antibacterial Protection"],"prefix":"10.3390","volume":"14","author":[{"given":"Xiang","family":"Cheng","sequence":"first","affiliation":[{"name":"Shanghai Institute of Infectious Disease and Biosecurity, Fudan University, Shanghai 200032, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Shaoqiong","family":"Huang","sequence":"additional","affiliation":[{"name":"Shanghai Public Health Clinical Center, Fudan University, Shanghai 201508, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8490-4389","authenticated-orcid":false,"given":"Zhidong","family":"Hu","sequence":"additional","affiliation":[{"name":"Shanghai Public Health Clinical Center, Fudan University, Shanghai 201508, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6654-3559","authenticated-orcid":false,"given":"Xiaoyong","family":"Fan","sequence":"additional","affiliation":[{"name":"Shanghai Institute of Infectious Disease and Biosecurity, Fudan University, Shanghai 200032, China"},{"name":"Shanghai Public Health Clinical Center, Fudan University, Shanghai 201508, China"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2026,3,27]]},"reference":[{"key":"ref_1","unstructured":"(2024). GBD 2021 Antimicrobial Resistance Collaborators. Global burden of bacterial antimicrobial resistance 1990\u20132021: A systematic analysis with forecasts to 2050. Lancet, 404, 1199\u20131226."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"417","DOI":"10.1128\/MMBR.00016-10","article-title":"Origins and evolution of antibiotic resistance","volume":"74","author":"Davies","year":"2010","journal-title":"Microbiol. Mol. Biol. Rev."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"287","DOI":"10.1038\/s41579-020-00506-3","article-title":"The role of vaccines in combatting antimicrobial resistance","volume":"19","author":"Micoli","year":"2021","journal-title":"Nat. Rev. Microbiol."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"1368","DOI":"10.1001\/jama.2013.3010","article-title":"Effect of an Investigational Vaccine for Preventing Staphylococcus aureus Infections After Cardiothoracic Surgery: A Randomized Trial","volume":"309","author":"Fowler","year":"2013","journal-title":"JAMA"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"223","DOI":"10.1016\/j.chom.2012.06.006","article-title":"Candida albicans infection affords protection against reinfection via functional reprogramming of monocytes","volume":"12","author":"Quintin","year":"2012","journal-title":"Cell Host Microbe"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"355","DOI":"10.1016\/j.chom.2011.04.006","article-title":"Trained immunity: A memory for innate host defense","volume":"9","author":"Netea","year":"2011","journal-title":"Cell Host Microbe"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"23","DOI":"10.1038\/s41581-022-00633-5","article-title":"Trained immunity\u2014Basic concepts and contributions to immunopathology","volume":"19","author":"Ochando","year":"2023","journal-title":"Nat. Rev. Nephrol."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"176","DOI":"10.1016\/j.cell.2017.12.031","article-title":"BCG Educates Hematopoietic Stem Cells to Generate Protective Innate Immunity against Tuberculosis","volume":"172","author":"Kaufmann","year":"2018","journal-title":"Cell"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"aaf1098","DOI":"10.1126\/science.aaf1098","article-title":"Trained immunity: A program of innate immune memory in health and disease","volume":"352","author":"Netea","year":"2016","journal-title":"Science"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"32","DOI":"10.1016\/j.immuni.2020.10.011","article-title":"The Intersection of Epigenetics and Metabolism in Trained Immunity","volume":"54","author":"Fanucchi","year":"2021","journal-title":"Immunity"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"1251086","DOI":"10.1126\/science.1251086","article-title":"Epigenetic programming of monocyte-to-macrophage differentiation and trained innate immunity","volume":"345","author":"Saeed","year":"2014","journal-title":"Science"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"464","DOI":"10.1038\/s41577-020-0338-x","article-title":"The non-specific and sex-differential effects of vaccines","volume":"20","author":"Aaby","year":"2020","journal-title":"Nat. Rev. Immunol."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"e274","DOI":"10.1016\/S1473-3099(19)30742-X","article-title":"Vaccinology: Time to change the paradigm?","volume":"20","author":"Benn","year":"2020","journal-title":"Lancet Infect. Dis."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"17537","DOI":"10.1073\/pnas.1202870109","article-title":"Bacille Calmette-Guerin induces NOD2-dependent nonspecific protection from reinfection via epigenetic reprogramming of monocytes","volume":"109","author":"Kleinnijenhuis","year":"2012","journal-title":"Proc. Natl. Acad. Sci. USA"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"2785","DOI":"10.4049\/jimmunol.2100107","article-title":"beta-Glucan Induces Distinct and Protective Innate Immune Memory in Differentiated Macrophages","volume":"207","author":"Stothers","year":"2021","journal-title":"J. Immunol."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"152","DOI":"10.1159\/000355628","article-title":"Long-lasting effects of BCG vaccination on both heterologous Th1\/Th17 responses and innate trained immunity","volume":"6","author":"Kleinnijenhuis","year":"2014","journal-title":"J. Innate Immun."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"807","DOI":"10.1016\/j.cmet.2016.10.008","article-title":"Glutaminolysis and Fumarate Accumulation Integrate Immunometabolic and Epigenetic Programs in Trained Immunity","volume":"24","author":"Arts","year":"2016","journal-title":"Cell Metab."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"1250684","DOI":"10.1126\/science.1250684","article-title":"mTOR- and HIF-1alpha-mediated aerobic glycolysis as metabolic basis for trained immunity","volume":"345","author":"Cheng","year":"2014","journal-title":"Science"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"771","DOI":"10.1038\/cr.2015.68","article-title":"Metabolic reprogramming in macrophages and dendritic cells in innate immunity","volume":"25","author":"Kelly","year":"2015","journal-title":"Cell Res."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"112","DOI":"10.1016\/j.stem.2022.12.005","article-title":"C\/EBPbeta-Dependent Epigenetic Memory Induces Trained Immunity in Hematopoietic Stem Cells","volume":"30","author":"Maurizio","year":"2023","journal-title":"Cell Stem Cell"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"1709","DOI":"10.1016\/j.cell.2022.03.043","article-title":"Maladaptive innate immune training of myelopoiesis links inflammatory comorbidities","volume":"185","author":"Li","year":"2022","journal-title":"Cell"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"162","DOI":"10.1016\/j.cell.2017.12.013","article-title":"Western Diet Triggers NLRP3-Dependent Innate Immune Reprogramming","volume":"172","author":"Christ","year":"2018","journal-title":"Cell"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"147","DOI":"10.1016\/j.cell.2017.11.034","article-title":"Modulation of Myelopoiesis Progenitors Is an Integral Component of Trained Immunity","volume":"172","author":"Mitroulis","year":"2018","journal-title":"Cell"},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"107","DOI":"10.4161\/viru.22718","article-title":"Hypervirulent (hypermucoviscous) Klebsiella pneumoniae: A new and dangerous breed","volume":"4","author":"Shon","year":"2013","journal-title":"Virulence"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"866","DOI":"10.1016\/j.amjmed.2009.03.034","article-title":"Incidence, Risk Factors, and Outcomes of Klebsiella pneumoniae Bacteremia","volume":"122","author":"Meatherall","year":"2009","journal-title":"Am. J. Med."},{"key":"ref_26","doi-asserted-by":"crossref","unstructured":"Karampatakis, T., Tsergouli, K., and Behzadi, P. (2023). Carbapenem-Resistant Klebsiella pneumoniae: Virulence Factors, Molecular Epidemiology and Latest Updates in Treatment Options. Antibiotics, 12.","DOI":"10.3390\/antibiotics12020234"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"97","DOI":"10.1186\/s13567-022-01116-y","article-title":"KbvR mutant of Klebsiella pneumoniae affects the synthesis of type 1 fimbriae and provides protection to mice as a live attenuated vaccine","volume":"53","author":"Zhang","year":"2022","journal-title":"Vet. Res."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"21","DOI":"10.1186\/s13293-024-00597-0","article-title":"XX sex chromosome complement modulates immune responses to heat-killed Streptococcus pneumoniae immunization in a microbiome-dependent manner","volume":"15","author":"Hopen","year":"2024","journal-title":"Biol. Sex Differ."},{"key":"ref_29","doi-asserted-by":"crossref","unstructured":"Assoni, L., Ciaparin, I., Trentini, M.M., Baboghlian, J., Rodrigo, G., Ferreira, B.V., Pereira, J.A., Martinez, C., Ferraz, L., and Girardello, R. (2025). Protection Against Pneumonia Induced by Vaccination with Fimbriae Subunits from Klebsiella pneumoniae. Vaccines, 13.","DOI":"10.3390\/vaccines13030303"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"629","DOI":"10.1128\/MMBR.00078-15","article-title":"Klebsiella pneumoniae: Going on the Offense with a Strong Defense","volume":"80","author":"Paczosa","year":"2016","journal-title":"Microbiol. Mol. Biol. Rev."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"34","DOI":"10.1186\/s11658-025-00717-7","article-title":"Insights into the roles of macrophages in Klebsiella pneumoniae infections: A comprehensive review","volume":"30","author":"Li","year":"2025","journal-title":"Cell Mol. Biol. Lett."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"103267","DOI":"10.1016\/j.xpro.2024.103267","article-title":"Protocol for analyzing BCG-induced trained immunity in murine bone marrow-derived macrophages","volume":"5","author":"Xu","year":"2024","journal-title":"STAR Protoc."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"eadk8093","DOI":"10.1126\/sciadv.adk8093","article-title":"Multi-omics analysis reveals that linoleic acid metabolism is associated with variations of trained immunity induced by distinct BCG strains","volume":"10","author":"Xu","year":"2024","journal-title":"Sci. Adv."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"2562","DOI":"10.1016\/j.celrep.2016.11.011","article-title":"Immunometabolic Pathways in BCG-Induced Trained Immunity","volume":"17","author":"Arts","year":"2016","journal-title":"Cell Rep."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"7","DOI":"10.1007\/s00281-024-01015-8","article-title":"Metabolic Regulation in the Induction of Trained Immunity","volume":"46","author":"Ferreira","year":"2024","journal-title":"Semin. Immunopathol."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"425","DOI":"10.1016\/j.smim.2016.09.002","article-title":"Immunometabolic circuits in trained immunity","volume":"28","author":"Arts","year":"2016","journal-title":"Semin. Immunol."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"2095","DOI":"10.1016\/j.immuni.2024.07.021","article-title":"BCG vaccination alters the epigenetic landscape of progenitor cells in human bone marrow to influence innate immune responses","volume":"57","author":"Sun","year":"2024","journal-title":"Immunity"},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"322","DOI":"10.1016\/j.chom.2020.05.014","article-title":"BCG Vaccination in Humans Elicits Trained Immunity via the Hematopoietic Progenitor Compartment","volume":"28","author":"Cirovic","year":"2020","journal-title":"Cell Host Microbe"},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"107596","DOI":"10.1016\/j.isci.2023.107596","article-title":"Hematopoietic stem and progenitor cells confer cross-protective trained immunity in mouse models","volume":"26","author":"Kain","year":"2023","journal-title":"iScience"},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"1651","DOI":"10.1016\/j.stemcr.2024.09.004","article-title":"Interleukin-1beta induces trained innate immunity in human hematopoietic progenitor cells in vitro","volume":"19","author":"Hobo","year":"2024","journal-title":"Stem. Cell Rep."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"315","DOI":"10.1016\/j.cell.2020.08.051","article-title":"Activate: Randomized Clinical Trial of BCG Vaccination against Infection in the Elderly","volume":"183","author":"Tsilika","year":"2020","journal-title":"Cell"},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"245","DOI":"10.1093\/infdis\/jir240","article-title":"Randomized trial of BCG vaccination at birth to low-birth-weight children: Beneficial nonspecific effects in the neonatal period?","volume":"204","author":"Aaby","year":"2011","journal-title":"J. Infect. Dis."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"1611","DOI":"10.1093\/cid\/civ144","article-title":"Nonspecific (Heterologous) Protection of Neonatal BCG Vaccination Against Hospitalization Due to Respiratory Infection and Sepsis","volume":"60","year":"2015","journal-title":"Clin. Infect. Dis."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"1473","DOI":"10.1016\/j.cmi.2019.04.020","article-title":"Non-specific effects of BCG vaccine on viral infections","volume":"25","author":"Moorlag","year":"2019","journal-title":"Clin. Microbiol. Infect."}],"container-title":["Vaccines"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2076-393X\/14\/4\/300\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,3,27]],"date-time":"2026-03-27T11:13:14Z","timestamp":1774609994000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2076-393X\/14\/4\/300"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,3,27]]},"references-count":44,"journal-issue":{"issue":"4","published-online":{"date-parts":[[2026,4]]}},"alternative-id":["vaccines14040300"],"URL":"https:\/\/doi.org\/10.3390\/vaccines14040300","relation":{},"ISSN":["2076-393X"],"issn-type":[{"value":"2076-393X","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,3,27]]}}}