Immunization with Inactivated <i>Bacillus subtilis</i> Spores Expressing TonB-Dependent Receptor (TBDR) Protects Against Multidrug-Resistant <i>Acinetobacter baumannii</i> Infection
Background/Objectives: The emergence of multidrug-resistant <i>Acinetobacter baumannii</i> (MDR <i>A. baumannii</i>) as a leading cause of fatal hospital-acquired infections underscores the urgent need for effective vaccines. While oral vaccines using live <i>Bacillus s...
Saved in:
| Main Authors: | , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2025-06-01
|
| Series: | Vaccines |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2076-393X/13/6/616 |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| _version_ | 1850164448527908864 |
|---|---|
| author | Amalia A. Saperi Atiqah Hazan Nurfatihah Zulkifli Hai-Yen Lee Nor-Aziyah MatRahim Sazaly AbuBakar |
| author_facet | Amalia A. Saperi Atiqah Hazan Nurfatihah Zulkifli Hai-Yen Lee Nor-Aziyah MatRahim Sazaly AbuBakar |
| author_sort | Amalia A. Saperi |
| collection | DOAJ |
| description | Background/Objectives: The emergence of multidrug-resistant <i>Acinetobacter baumannii</i> (MDR <i>A. baumannii</i>) as a leading cause of fatal hospital-acquired infections underscores the urgent need for effective vaccines. While oral vaccines using live <i>Bacillus subtilis</i> spores expressing <i>A. baumannii</i> TonB-dependent receptor (TBDR) show promise, biosafety concerns regarding recombinant spore persistence necessitate alternative strategies. Here, we evaluated chemically inactivated <i>B. subtilis</i> spores displaying TBDR as a safer yet immunogenic vaccine candidate. Methods: Recombinant spores were inactivated using iron-ethanol sporicidal solution and administered to BALB/c mice (8–12 weeks old) to assess safety and immunogenicity. Toxicity was evaluated through clinical monitoring, serum biochemistry, and histopathology. Immune responses were characterized by T/B cell activation, IgG/IgA titers, and mucosal sIgA levels. Protective efficacy was determined by challenging immunized mice with MDR <i>A. baumannii</i> Ab35 and quantifying bacterial loads and examining tissue pathology. Results: The inactivated spores exhibited an excellent safety profile, with no adverse effects on clinical parameters, organ function, or tissue integrity. Immunization induced robust systemic and mucosal immunity, evidenced by elevated CD4+/CD8+ T cells, B cells, and antigen-specific IgG/IgA in serum and mucosal secretions. Following the challenge, vaccinated mice showed significantly reduced pulmonary bacterial burdens (>90% reduction), and preserved lung and spleen architecture compared to controls, which developed severe inflammation and tissue damage. Conclusions: These findings demonstrate that inactivated <i>B. subtilis</i> spores expressing TBDR are a safe, orally administrable vaccine platform that elicits protective immunity against MDR <i>A. baumannii</i>. By addressing biosafety concerns associated with live spores while maintaining efficacy, this approach represents a critical advance toward preventing high-risk nosocomial infections. |
| format | Article |
| id | doaj-art-ddda0e2ea9f444198f1d727d65c792ea |
| institution | OA Journals |
| issn | 2076-393X |
| language | English |
| publishDate | 2025-06-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Vaccines |
| spelling | doaj-art-ddda0e2ea9f444198f1d727d65c792ea2025-08-20T02:21:58ZengMDPI AGVaccines2076-393X2025-06-0113661610.3390/vaccines13060616Immunization with Inactivated <i>Bacillus subtilis</i> Spores Expressing TonB-Dependent Receptor (TBDR) Protects Against Multidrug-Resistant <i>Acinetobacter baumannii</i> InfectionAmalia A. Saperi0Atiqah Hazan1Nurfatihah Zulkifli2Hai-Yen Lee3Nor-Aziyah MatRahim4Sazaly AbuBakar5Tropical Infectious Diseases Research and Education Centre (TIDREC), University Malaya, Kuala Lumpur 50603, MalaysiaTropical Infectious Diseases Research and Education Centre (TIDREC), University Malaya, Kuala Lumpur 50603, MalaysiaTropical Infectious Diseases Research and Education Centre (TIDREC), University Malaya, Kuala Lumpur 50603, MalaysiaTropical Infectious Diseases Research and Education Centre (TIDREC), University Malaya, Kuala Lumpur 50603, MalaysiaInstitute for Medical Research (IMR), Setia Alam, Shah Alam 40170, MalaysiaTropical Infectious Diseases Research and Education Centre (TIDREC), University Malaya, Kuala Lumpur 50603, MalaysiaBackground/Objectives: The emergence of multidrug-resistant <i>Acinetobacter baumannii</i> (MDR <i>A. baumannii</i>) as a leading cause of fatal hospital-acquired infections underscores the urgent need for effective vaccines. While oral vaccines using live <i>Bacillus subtilis</i> spores expressing <i>A. baumannii</i> TonB-dependent receptor (TBDR) show promise, biosafety concerns regarding recombinant spore persistence necessitate alternative strategies. Here, we evaluated chemically inactivated <i>B. subtilis</i> spores displaying TBDR as a safer yet immunogenic vaccine candidate. Methods: Recombinant spores were inactivated using iron-ethanol sporicidal solution and administered to BALB/c mice (8–12 weeks old) to assess safety and immunogenicity. Toxicity was evaluated through clinical monitoring, serum biochemistry, and histopathology. Immune responses were characterized by T/B cell activation, IgG/IgA titers, and mucosal sIgA levels. Protective efficacy was determined by challenging immunized mice with MDR <i>A. baumannii</i> Ab35 and quantifying bacterial loads and examining tissue pathology. Results: The inactivated spores exhibited an excellent safety profile, with no adverse effects on clinical parameters, organ function, or tissue integrity. Immunization induced robust systemic and mucosal immunity, evidenced by elevated CD4+/CD8+ T cells, B cells, and antigen-specific IgG/IgA in serum and mucosal secretions. Following the challenge, vaccinated mice showed significantly reduced pulmonary bacterial burdens (>90% reduction), and preserved lung and spleen architecture compared to controls, which developed severe inflammation and tissue damage. Conclusions: These findings demonstrate that inactivated <i>B. subtilis</i> spores expressing TBDR are a safe, orally administrable vaccine platform that elicits protective immunity against MDR <i>A. baumannii</i>. By addressing biosafety concerns associated with live spores while maintaining efficacy, this approach represents a critical advance toward preventing high-risk nosocomial infections.https://www.mdpi.com/2076-393X/13/6/616<i>Acinetobacter baumannii</i><i>Bacillus subtilis</i>pneumoniasporesvaccine |
| spellingShingle | Amalia A. Saperi Atiqah Hazan Nurfatihah Zulkifli Hai-Yen Lee Nor-Aziyah MatRahim Sazaly AbuBakar Immunization with Inactivated <i>Bacillus subtilis</i> Spores Expressing TonB-Dependent Receptor (TBDR) Protects Against Multidrug-Resistant <i>Acinetobacter baumannii</i> Infection Vaccines <i>Acinetobacter baumannii</i> <i>Bacillus subtilis</i> pneumonia spores vaccine |
| title | Immunization with Inactivated <i>Bacillus subtilis</i> Spores Expressing TonB-Dependent Receptor (TBDR) Protects Against Multidrug-Resistant <i>Acinetobacter baumannii</i> Infection |
| title_full | Immunization with Inactivated <i>Bacillus subtilis</i> Spores Expressing TonB-Dependent Receptor (TBDR) Protects Against Multidrug-Resistant <i>Acinetobacter baumannii</i> Infection |
| title_fullStr | Immunization with Inactivated <i>Bacillus subtilis</i> Spores Expressing TonB-Dependent Receptor (TBDR) Protects Against Multidrug-Resistant <i>Acinetobacter baumannii</i> Infection |
| title_full_unstemmed | Immunization with Inactivated <i>Bacillus subtilis</i> Spores Expressing TonB-Dependent Receptor (TBDR) Protects Against Multidrug-Resistant <i>Acinetobacter baumannii</i> Infection |
| title_short | Immunization with Inactivated <i>Bacillus subtilis</i> Spores Expressing TonB-Dependent Receptor (TBDR) Protects Against Multidrug-Resistant <i>Acinetobacter baumannii</i> Infection |
| title_sort | immunization with inactivated i bacillus subtilis i spores expressing tonb dependent receptor tbdr protects against multidrug resistant i acinetobacter baumannii i infection |
| topic | <i>Acinetobacter baumannii</i> <i>Bacillus subtilis</i> pneumonia spores vaccine |
| url | https://www.mdpi.com/2076-393X/13/6/616 |
| work_keys_str_mv | AT amaliaasaperi immunizationwithinactivatedibacillussubtilisisporesexpressingtonbdependentreceptortbdrprotectsagainstmultidrugresistantiacinetobacterbaumanniiiinfection AT atiqahhazan immunizationwithinactivatedibacillussubtilisisporesexpressingtonbdependentreceptortbdrprotectsagainstmultidrugresistantiacinetobacterbaumanniiiinfection AT nurfatihahzulkifli immunizationwithinactivatedibacillussubtilisisporesexpressingtonbdependentreceptortbdrprotectsagainstmultidrugresistantiacinetobacterbaumanniiiinfection AT haiyenlee immunizationwithinactivatedibacillussubtilisisporesexpressingtonbdependentreceptortbdrprotectsagainstmultidrugresistantiacinetobacterbaumanniiiinfection AT noraziyahmatrahim immunizationwithinactivatedibacillussubtilisisporesexpressingtonbdependentreceptortbdrprotectsagainstmultidrugresistantiacinetobacterbaumanniiiinfection AT sazalyabubakar immunizationwithinactivatedibacillussubtilisisporesexpressingtonbdependentreceptortbdrprotectsagainstmultidrugresistantiacinetobacterbaumanniiiinfection |