---
title: "BECC438 vs BECC470 adjuvants: comparative immunogenicity and protection in a Pseudomonas aeruginos"
id: "frontiers-in-immunology-8-comparative-immunogenicity-and-protective-efficacy-of-becc438-and-becc470"
canonical_url: "https://medichelpline.com/clinical-feed/frontiers-in-immunology-8-comparative-immunogenicity-and-protective-efficacy-of-becc438-and-becc470"
content_type: "clinical_feed_article"
specialty: "Infectious Disease"
source_name: "Frontiers in Immunology"
source_url: "https://www.frontiersin.org/articles/10.3389/fimmu.2026.1908082"
published_at: "2026-09-03T00:00:00.000Z"
evidence_level: "Journal Feed"
license: "CC-BY-NC-4.0 / Informational Use"
---
# BECC438 vs BECC470 adjuvants: comparative immunogenicity and protection in a Pseudomonas aeruginos
## Provenance & Clinical Metadata
- **Canonical URL:** https://medichelpline.com/clinical-feed/frontiers-in-immunology-8-comparative-immunogenicity-and-protective-efficacy-of-becc438-and-becc470
- **Specialty:** [Infectious Disease](https://medichelpline.com/clinical-feed/infectious-disease.md)
- **Primary Source:** Frontiers in Immunology
- **Source URL:** [Original Journal Publication](https://www.frontiersin.org/articles/10.3389/fimmu.2026.1908082)
- **Published At:** 2026-09-03T00:00:00.000Z
- **Evidence Rating:** Journal Feed
## Executive GIST (TL;DR)
- This preclinical study compared two lipid A mimetic adjuvants, **BECC438** and **BECC470**, in biologically derived (b) and synthetic (s) forms combined with an L-PaF subunit antigen against pulmonary Pseudomonas aeruginosa (Pa) in mice. - L-PaF is a genetic fusion of T3SS proteins PcrV and PopB with LTA1 (the active moiety of dmLT) formulated in a squalene-based oil-in-water emulsion (ME). - Formulations contained 1 μg L-PaF and 0.5 μg of BECC adjuvant per dose and were given intranasally (IN) or intramuscularly (IM) on days 0, 14, and 28; immune readouts were collected through day 56 with challenge on day 56. - IN immunization with BECC438 (both synthetic and biologic forms) elicited robust antigen-specific **IgG** and **IgA** responses, with a mixed Th1/Th2–indicative IgG1/IgG3 profile but predominance of IgG1. - BECC438s (synthetic) delivered IN produced the greatest reduction in lung bacterial burden after pulmonary challenge compared with BECC470 formulations and IM routes. - Serum antibody titers and pre- or post-challenge cytokine responses correlated with bacterial clearance, supporting mechanistic links between humoral/cytokine responses and protection. - BECC470 has shown advantages in other contexts (e.g., aged mice in prior reports), but in this Pa pulmonary model BECC470 formulations were less effective than BECC438 at inducing mucosal and systemic immunity. - The BECC platform allows biologically derived (heterogeneous) and chemically synthesized (high-purity) lipid A analogues that selectively engage **TLR4/MD-2**, aiming to balance immunostimulation and reactogenicity. - The study used a clinical Pa strain (mPA08-31) isolated from a CF patient for challenge and included opsonophagocytic killing (OPK) assays, ELISAs for PcrV/PopB IgG, IgA and IgG subclasses, and lung CFU enumeration two days post-challenge. - The authors conclude BECC438, especially the synthetic BECC438s administered intranasally with L-PaF/ME, is a promising mucosal adjuvant candidate for next-generation vaccines against multidrug-resistant Pa; they note further translational studies are needed.
## Clinical Analysis & Structured Key Points
Frontiers | Comparative immunogenicity and protective efficacy of BECC438 and BECC470 adjuvants in a vaccine formulation against Pseudomonas aeruginosa ORIGINAL RESEARCH article Front. Immunol. , 03 September 2026 Sec. Vaccines and Molecular Therapeutics Volume 17 - 2026 | https://doi.org/10.3389/fimmu.2026.1908082 Published in Frontiers in Immunology Vaccines and Molecular Therapeutics 7 impact factor 11.3 citescore Editor & Reviewers Edited by S S Salman Sadullah Usmani Reviewed by A O Alex Odoom M M Mohamed Medhat Shamseldin Outline Figures and Tables Figure 1 View in article Figure 2 View in article Figure 3 View in article Figure 4 View in article Figure 5 View in article Figure 6 View in article Figure 7 View in article Figure 8 View in article Figure 9 View in article ORIGINAL RESEARCH article Front. Immunol. , 03 September 2026 Sec. Vaccines and Molecular Therapeutics Volume 17 - 2026 | https://doi.org/10.3389/fimmu.2026.1908082 Comparative immunogenicity and protective efficacy of BECC438 and BECC470 adjuvants in a vaccine formulation against Pseudomonas aeruginosa P H Prolay Halder 1,2 D R Debaki Ranjan Howlader 1,2 † S B Satabdi Biswas 1,2 R H Risha Haldar 1,2 S M Suhrid Maiti 1,2 S D Sayan Das 3 Z K Zackary K. Dietz 1,2 T L Ti Lu 1,2 S K Sean K. Whittier 1,2 R K Robert K. Ernst 3 W D William D. Picking 1,2 +3 more W L Wendy L. Picking 1,2 * 1. Bond Life Sciences Center, University of Missouri, Columbia, MO, United States 2. Department of Pathobiology & Integrative Biomedical Sciences, University of Missouri, Columbia, MO, United States 3. Department of Microbial Pathogenesis, University of Maryland, Baltimore, MD, United States See more Article metrics View details Abstract The development of effective vaccines against the opportunistic pathogen Pseudomonas aeruginosa (Pa) remains a critical public health priority for susceptible individuals due, in part, to the pathogen’s intrinsic resistance mechanisms. This study evaluates the comparative immunogenicity and protective efficacy of two novel lipid A mimetic adjuvants, BECC438 (BECC438s or BECC438b) and BECC470 (BECC470s or BECC470b), in a subunit vaccine (L-PaF – a genetic fusion of Pa type III secretion system proteins PcrV and PopB with LTA1, the active moiety of heat-labile enterotoxin from enterotoxigenic E. coli ) formulated into an oil-in-water (o/w) emulsion to target Pa. BECC438b and BECC470b are biologically derived lipid A analogues produced using a Bacterial Enzymatic Combinatorial Chemistry (BECC) platform. In contrast, BECC438s and BECC470s are chemically synthesized counterparts designed to achieve high purity, eliminating congener species that could interfere with selective Toll-like receptor 4 (TLR4) activation while minimizing potential reactogenicity. Vaccine formulations incorporating BECC438 or BECC470 with Pa antigens were administered to mice via intranasal (IN) or intramuscular (IM) routes, followed by assessment of immune responses and lung burden post-challenge with Pa. IN immunization with BECC438s or BECC438b induced robust antigen-specific IgG and IgA responses, with a balanced IgG1/IgG3 profile that is indicative of mixed Th1/Th2 polarization, however, IgG1 remained the predominant antibody subclass. BECC438s conferred the highest protection against Pa challenge by reducing bacterial burden and improving immune responses following IN immunization. Moreover, L-PaF/ME/BECC438s delivered IN provided superior protection when compared to IM immunization. Serum antibody titers and pre-challenged or post-challenged cytokine responses were directly correlated with bacterial clearance upon Pa pulmonary challenge. These findings suggest that BECC438 offers enhanced mucosal and systemic immunity over BECC470 in this infection model, making it a promising candidate for inclusion in mucosal next-generation Pa vaccines. Overall, this comparative analysis highlights the potential of BECC derived adjuvants to improve vaccine performance against multidrug-resistant pathogens like Pa following IN immunization. Further studies are warranted to evaluate their translational potential in human populations. Introduction Pseudomonas aeruginosa (Pa) is a Gram-negative opportunistic pathogen that poses a significant threat to immunocompromised individuals, particularly those with cystic fibrosis (CF), burn wounds, or ventilator-associated pneumonia ( 1 , 2 ). Its intrinsic resistance to antibiotics, coupled with its ability to acquire new resistance mechanisms, has rendered many conventional treatments ineffective, prompting the World Health Organization (WHO) to classify Pa as a critical priority pathogen for the development of new antimicrobial strategies ( 3 ). From 2017 to 2018, hospital-onset Pa infections in U.S. acute care hospitals declined by 15% ( 4 ); however, the global burden surged in 2019 with over 500,000 deaths attributed to Pa, including more than 250,000 deaths linked to antimicrobial resistance (AMR). In 2020, during the COVID-19 pandemic, increased ventilator use and prolonged hospital stays led to a 29% increase in infections and 44% rise in carbapenem-resistant Pa (CRPA) infections compared to 2019 ( 4 ). By 2021–2022, multidrug-resistant (MDR) Pa prevalence in Asia and Africa reached 46%, with 19.6% of the isolates classified as extensively drug-resistant (XDR). Resistance to β-lactams exceeded 84%, while polymyxin resistance remained low ( 96% sequence conservation ( 14 ). These proteins are essential for T3SS function, and mutations typically attenuate virulence, minimizing vaccine escape ( 15 ). Previously, we have shown that intranasal (IN) administration of PcrV and PopB with dmLT, double-mutant labile toxin from enterotoxigenic E. coli , protected mice from pulmonary Pa challenge ( 16 ). dmLT is an adjuvant that triggers an immune response characterized by increased IgG2a, IgA, and IL-17A at mucosal sites ( 17 ). A PcrV-PopB fusion protein (PaF) was subsequently fused with LTA1, the active moiety of dmLT, to create the self‑adjuvanting L-PaF in a move to further improve its immunogenic potential. We have previously demonstrated that L-PaF induces strong IgG, IgA, IL-17A, and opsonophagocytic killing responses, allowing for lung clearance in animal models that is independent of serotype ( 18 ). These findings support the potential for L-PaF to be a broadly protective mucosal vaccine, particularly for high-risk groups like those with CF or ventilator-associated pneumonia ( 19 , 20 ). Adjuvants play a pivotal role in enhancing vaccine efficacy by modulating the magnitude and quality of the immune response. Traditional adjuvants, such as aluminum salts, primarily induce Th2-biased responses, which may be suboptimal for pathogens like Pa that require robust Th1 and Th17 immunity for effective clearance ( 21 ). The respiratory mucosa presents unique challenges for vaccine delivery, as mucociliary clearance mechanisms and the presence of a thick mucus layer can rapidly remove or trap vaccine antigens, thereby limiting antigen uptake and retention at the site of immunization ( 22 ). These barriers highlight the need for adjuvants that actively stimulate local innate immune responses and promote engagement of mucosal dendritic cell networks. In recent years, novel adjuvant platforms including toll-like receptor (TLR) agonists that mimic pathogen-associated molecular patterns (PAMPs) and activate innate immunity, have been developed. Among these, the Bacterial Enzymatic Combinatorial Chemistry (BECC) platform has gained attention for its ability to generate novel lipid A analogues that selectively engage the MD-2/TLR4 receptor complex. BECC438b and BECC470b are two engineered lipid A derivatives designed to retain immunostimulatory properties while minimizing endotoxicity ( 23 ). These molecules act as partial TLR4 agonists, promoting balanced Th1/Th2 responses and enhancing antigen-specific antibody production without triggering excessive inflammation ( 24 ). They are also attractive because they can enhance dendritic cell activation and antigen presentation and support the development of protective adaptive immunity while maintaining a favorable safety profile ( 25 ). Preclinical studies have demonstrated the potential of BECC438b and BECC470b as adjuvants in bacterial and viral subunit vaccines ( 23 , 26 ). Notably, BECC470b has shown superior performance in aged mouse models, suggesting its utility in vulnerable immunosenescent populations ( 26 ). More recently, highly pure synthetic forms of these adjuvants (BECC438s and BECC470s) have been generated and found to have physical properties that are distinct from those of their biologically-derived counterparts (BECC438b and BECC470b) ( 27 ). Despite these promising findings, the comparative immunogenicity and protective efficacy of BECC438 (b and s) versus BECC470 (b and s) in the context of Pa vaccination remain unexplored. This study aims to assess the immunogenic profiles and protective outcomes of vaccine formulations incorporating BECC438 and BECC470 in a murine pulmonary model of Pa infection. We hypothesize that both adjuvants will enhance antigen-specific immune responses but may differ in their ability to induce optimal protective immunity and cytokine polarization. By dissecting these differences, we seek to inform the selection of optimal adjuvant candidates for future clinical development against Pa and other multidrug-resistant pathogens. Materials and methods Materials BECC438b and BECC470b were prepared by extraction from Yersinia pestis after introducing lipid-A modifying enzymes ( 28 ). To overcome heterogeneity in the biological production of BECC438b and BECC470b, the chemically synthesized forms, BECC438s and BECC470s, were produced ( 27 ). They have been previously shown to be non-toxic in rodent ( 29 , 30 ). Squalene was purchased from Echelon Biosciences (Salt Lake City, UT). Pa mPa08-31, provided by Dr. Susan E. Birket, is a clinical strain isolated from a CF patient at the University of Alabama-Birmingham. Chromatography columns were from GE Healthcare (Piscataway, NJ, USA). All other reagents and chemicals were from Millipore-Sigma Chemical Co. (St. Louis, MO) or Thermo-Fisher Scientific (Waltham, MA) and were chemical-grade or higher. Protein preparation L-PaF was produced as previously described with minor modifications ( 16 , 31 ). Briefly, E. coli HMS174(DE3) harboring ltA1-pcrV-popB / histag-pcrH //pACYCDuet-1 cultures were grown in LB containing 42 µg/mL chloramphenicol at 37 °C. When the cultures reached OD 600 ≈ 0.8, protein expression was induced by the addition of 1 mM IPTG and incubated for an additional 3 h. Cells were harvested, lysed and clarified by centrifugation. The supernatant was subjected to IMAC column chromatography followed by Q anion exchange column chromatography to isolate the L-PaF/HT-PcrH complex. HT-PcrH dissociation was achieved by adding 0.1% LDAO and passing the mixture over a final IMAC column with the L-PaF in the flow-through. The protein was dialyzed into storage buffer, pH 6.5 (0.01 M NaH 2 PO 4 /Na 2 HPO 4 , 100 mM NaCl, 5% sucrose, 0.05% LDAO) and stored at −80 °C. Endotoxin levels were verified to be < 5 EU/mg protein using NexGen PTS (EndoSafe cartridges, Charles River Laboratories). Preparation of L- PaF BECC438 and BECC470/ME formulations A squalene-based oil-in-water emulsion was prepared to provide a formulation for this Pa vaccine. Briefly, a homogeneous oil phase was achieved by mixing polysorbate 80 (2% by weight) with squalene (8% by weight). 40 mM histidine (pH 6) and 20% sucrose were added to the oil phase and combined at 7500 rpm using a Silverson L5M-A standard high-speed mixer. This was followed by six passes through a Microfluidics 110P microfluidizer at 20,000 pressure to create a milky emulsion of 4 X ME (MedImmune Emulsion) ( 32 ). BECC438b/s (0.5 mg/ml) was made by vortexing it in 0.5% triethylamine, then sonicating it for 30 min at 60 °C in a water bath sonicator until it was fully dissolved. Using 1 M HCl, the BECC438b/s solution pH was adjusted to 7.2. BECC438b/s and ME were combined by vortexing for two min, and then the mixture was incubated overnight at 4 °C. The subsequent day, to get the intended final antigen concentration, L-PaF was combined with the ME-BECC438 solution at a volumetric ratio of 1:1. The BECC470b/s formulation methodology was identical to the BECC438b/s formulation methodology ( 31 , 33 ). Ethics statement All animal procedures were reviewed and approved by the Institutional Animal Care and Use Committee (IACUC) animal use statement (Protocol 38241) from the University of Missouri. Mouse immunization and sample collection Female C57BL/6J mice aged 6 to 8 weeks (n = 5 per cage) from Jackson Laboratories (Bar Harbor, ME) were used during the study. All groups received vaccinations either intranasally (IN) or intramuscularly (IM), depending on the experimental group’s preferred method. The following formulations were made in 30 µl volumes before dosing. The groups were vaccinated with PBS, 1 μg of L-PaF in ME with 0.5 μg BECC438b (L-PaF/ME/BECC438b). 1 μg of L-PaF in ME with 0.5 μg BECC438s (L-PaF/ME/BECC438s). 1 μg of L-PaF in ME with 0.5 μg BECC470b (L-PaF/ME/BECC 470b). 1 μg of L-PaF in ME with 0.5 μg BECC470s (L-PaF/ME/BECC 470s). Mice were anesthetized using isoflurane (~4% in oxygen) dispensed through a precision vaporizer and immunized either IN or IM with the respective formulations. For the IN trials, the indicated formulations were delivered as previously described using a pipette tip to the nares ( 34 ). The specified formulations were then made for the IM trials and administered to the inner thigh ( 33 ). The initial group size (n = 10 mice/group), the longitudinal blood sampling strategy, with the subsequent division of animals into two terminal sub-cohorts (n = 5 mice/group) for immunological analyses and challenge studies. A summary of the experimental design is described in Figure 1 . Vaccinations were given on days 0, 14, and 28, and blood samples were taken on days 0, 28, 42, and 56. To evaluate the pre-challenge immunological state, lungs of five mice were removed on day 56. Lastly, five mice were used for the Pa challenge studies. Mice were euthanized using CO 2 administered at a rate of 30-70% of the chamber volume per minute. Mice were monitored until cessation of respiration and cervical dislocation was performed. Figure 1 An overview of the experimental setup showing details for each phase of the research. The arrows show the steps in the experimental methods’ advancement and time points. (This figure was generated using BioRender.com ). Enzyme-linked immunosorbent assay Serum IgG and IgA responses to purified recombinant PcrV and PopB were measured by ELISA as previously described with minor modifications ( 16 ). Briefly, 96‑well plates were coated with PcrV or PopB (1 μg/mL in PBS) and blocked overnight at 4 °C with 10% non‑fat dry milk. Serum samples were added and incubated for 1 h at 37 °C. After washing with 0.05% PBS-Tween, anti‑mouse IgG (1:1000, cat. #5450-0011 (474–1806) Sera Care, USA) or IgA (1:4000, cat. #OB1040-05, Southern Biotech, USA) was used as secondary antibodies. Endpoint titers were subsequently measured and expressed as ELISA units per milliliter. IgG1 and IgG3 subclasses were also measured using anti‑mouse IgG1 (1:1000, cat # 1070-05, Southern Biotech, USA) and anti-mouse IgG3 (1:4000, cat # 1191-05, Southern Biotech, USA). Opsonophagocytic assay Opsonophagocytic killing (OPK) assays were performed as described previously, where no exogenous complement source was used ( 16 , 31 ). Briefly, mPA08‑31 was grown to mid‑log phase and prepared (2 × 10 7 CFU/mL) in MEM containing 10% BSA. J774A.1 murine macrophages (ATCC, Manassas, VA) were cultured to near (90%) confluence, and the bacterial concentration was adjusted to an MOI of 0.1 in 10% MEM-BSA. Heat‑inactivated sera (at 56 °C for 30 min on day 42 post-immunization) from vaccinated mice were diluted (1:500) and combined with the bacteria and macrophages in 1:1:1 volumetric ratio to reach a final volume of 300 µL, they were then incubated at 37 °C for 30 min. Afterward, samples were serially diluted and plated onto Pseudomonas Isolation Agar (PIA) to quantify surviving bacteria. The formula used to measure bactericidal activity was: Bacterial culture and lung challenge mPA08–31 was incubated overnight at 37 °C with 200 rpm shaking. The culture was diluted 1:100 into fresh low-salt LB medium. mPa08–31 was grown to an A 600 ~0.3. The bacteria were then adjusted to a concentration of 4 × 10 7 CFU in 30 µL. IN challenges were performed on 56 days after the initial vaccination under isoflurane anesthesia. Each mouse was given 30 µl of the bacterial suspension. On day 2 post-infection, mice (n = 5) from each group were euthanized, and the lungs were harvested and processed. Lung homogenates were plated on PIA to determine the CFU/lung. Experimental conditions were kept consistent throughout the study ( 31 ). The formula used to measure % reduction of lung burden was calculated by: Organ processing The lungs and spleens were aseptically collected in MACS ® Tissue Storage Solution (Miltenyi Biotec, USA) and processed using a lung or spleen dissociation kit (Miltenyi Biotec, USA), respectively, into single cell suspensions for immunological investigation. The cell number was adjusted to 1 × 10 7 cells/ml after an erythrocyte lysis step. Subsequently, these cells were further processed to produce cytokines (see below). Post-challenge necropsies were performed two days after infection, while pre-challenge necropsies were performed 56 days after first vaccination. Cytokine determinations For the pre-challenged cytokine assay, both lung and spleen cells were stimulated for 48 h at 37 °C with 10 μg/ml PcrV, PopB, or PBS. For the post-challenged cytokine assay ( in vivo pro-inflammatory responses induced by bacterial challenge), lun
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