---
title: "Gonococcal OMV Vaccine Candidate Shows Persistent Immunity in Three Mouse Strains and Comparable I"
id: "frontiers-in-immunology-15-a-candidate-gonococcal-outer-membrane-vesicle-vaccine-which-induces-persistent"
canonical_url: "https://medichelpline.com/clinical-feed/frontiers-in-immunology-15-a-candidate-gonococcal-outer-membrane-vesicle-vaccine-which-induces-persistent"
content_type: "clinical_feed_article"
specialty: "Infectious Disease"
source_name: "Frontiers in Immunology"
source_url: "https://www.frontiersin.org/articles/10.3389/fimmu.2026.1923399"
published_at: "2026-10-02T00:00:00.000Z"
evidence_level: "Journal Feed"
license: "CC-BY-NC-4.0 / Informational Use"
---
# Gonococcal OMV Vaccine Candidate Shows Persistent Immunity in Three Mouse Strains and Comparable I
## Provenance & Clinical Metadata
- **Canonical URL:** https://medichelpline.com/clinical-feed/frontiers-in-immunology-15-a-candidate-gonococcal-outer-membrane-vesicle-vaccine-which-induces-persistent
- **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.2026.1923399)
- **Published At:** 2026-10-02T00:00:00.000Z
- **Evidence Rating:** Journal Feed
## Executive GIST (TL;DR)
- The source document available here contains only journal site boilerplate and the article title; the full article text and data were not included in the provided source. - The article title reports a candidate **gonococcal outer membrane vesicle (OMV) vaccine** that elicited **persistent immunity** in three genetically distinct mouse species. - The title also states the vaccine was **similarly immunogenic when formulated with and without aluminium adjuvant**. - No experimental details, numerical outcomes, methods, immunologic readouts, timelines, safety data, or statistical analyses were present in the supplied source. - Because full text and supporting data are missing from the source, specifics about dosing, vaccination schedule, mouse strains used, measures of persistence, or comparative antibody and cellular responses could not be extracted. - The title suggests potential cross-strain durability and an adjuvant-independent immunogenic profile for an OMV-based gonococcal vaccine, but direct interpretation requires the full article for validation. - Readers should consult the full article on Frontiers in Immunology for methods, results, figures, and conclusions; those details were not reported in the provided source.
## Clinical Analysis & Structured Key Points
Frontiers | A candidate gonococcal outer membrane vesicle vaccine which induces persistent immunity in three genetically distinct species of mouse and is similarly immunogenic when formulated with and without aluminium adjuvant ORIGINAL RESEARCH article Front. Immunol. , 02 October 2026 Sec. Vaccines and Molecular Therapeutics Volume 17 - 2026 | https://doi.org/10.3389/fimmu.2026.1923399 Published in Frontiers in Immunology Vaccines and Molecular Therapeutics 7 impact factor 11.3 citescore Editor & Reviewers Edited by D H Daniela Hozbor Reviewed by V P Vivek Phani Varma D G V Giacomo Vezzani 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 ORIGINAL RESEARCH article Front. Immunol. , 02 October 2026 Sec. Vaccines and Molecular Therapeutics Volume 17 - 2026 | https://doi.org/10.3389/fimmu.2026.1923399 A candidate gonococcal outer membrane vesicle vaccine which induces persistent immunity in three genetically distinct species of mouse and is similarly immunogenic when formulated with and without aluminium adjuvant I O Ilaria Onofrio 1 T B Thomas Belcher 1,2 M E Molly E. Quinn 1 E L Emma Lupoli 1 T F Tyler Freslov 1 N O Natasha Owen 1 S N Senuri N. Dissanayake 1 L A Lukasz A. Grudzein 1 P F Paula Freixeiro 1 C S Christine S. Rollier 3 +2 more C A Calman A. MacLennan 1,4,5 * 1. Nuffield Department of Medicine, Jenner Institute, University of Oxford, Oxford, United Kingdom 2. School of Life Sciences, Keele University, Keele, United Kingdom 3. School of Biosciences, University of Surrey, Guildford, United Kingdom 4. Department of Infectious Diseases, Faculty of Medicine, Imperial College London, London, United Kingdom 5. Department of Immunology and Immunotherapy, College of Medicine and Health, University of Birmingham, Birmingham, United Kingdom See more Article metrics View details Abstract Background: The escalating global incidence of multidrug-resistant Neisseria gonorrhoeae necessitates an effective vaccine. While the meningococcal 4CMenB vaccine offers some cross-protection against gonorrhoea, this protection is limited highlighting the need for a targeted gonococcal vaccine. In this study, we evaluate the durability of immune response and characterise the immunogenicity induced by GonoVac, a native Outer Membrane Vesicle (nOMV) vaccine produced from N. gonorrhoeae GC_0817560 lpxL1 - , across genetically distinct strains of mouse. Methods: We evaluated the longevity of the immune response induced by two and three doses of GonoVac formulated with aluminium hydroxide (Al(OH) 3 ) over a one-year period (49 weeks for C57BL/6 and CD1 mice, 33 weeks for BALB/c mice), compared to the meningococcal group B vaccine, 4CMenB. Identical immunisation schedules were followed in BALB/c, C57BL/6, and CD1 mice. Separately, we examined the impact of Al(OH) 3 on GonoVac immunogenicity in all three mouse strains. Serological, mucosal, and cellular responses were assessed using ELISA, serum bactericidal assays (SBA) and ELISpot. Results: GonoVac with Al(OH) 3 induced robust, long-lasting anti-gonococcal IgG responses in all three strains of mice and significantly higher levels of antibody-dependent complement-mediated killing of gonococci in C57BL/6 and CD1 mice compared with 4CMenB. Immune responses were maintained for up to one year. Serum anti-gonococcal IgG subclass distributions varied across mouse strains and between GonoVac and 4CMenB in the same strain of mouse. GonoVac formulated with and without Al(OH) 3 elicited high levels of antibody-dependent complement-mediated killing of N. gonorrhoeae irrespective of mouse strain. While mucosal IgG responses were robust with both GonoVac formulations, Al(OH) 3 significantly enhancing cellular immunity in BALB/c and CD1 mice compared with C57BL/6 mice. Conclusions: Our findings demonstrate that GonoVac, a preclinical candidate gonococcal nOMV vaccine, induces durable and functional anti-gonococcal immune responses that are higher than 4CMenB, across three commonly used laboratory strains of mice. 1 Introduction Gonorrhoea, caused by the Gram-negative bacterium Neisseria gonorrhoeae , is the second most common sexually transmitted infection (STI), with over 82 million new cases estimated annually ( 1 , 2 ). The disease disproportionately affects women and individuals in low- and middle-income countries (LMICs), where limited access to diagnostic facilities, effective treatment, and surveillance systems often results in asymptomatic infections going undetected and untreated ( 3 ). Left unmanaged, gonorrhoea can lead to serious sexual and reproductive health complications including pelvic inflammatory disease (PID), infertility, ectopic pregnancy, and increased susceptibility to HIV infection ( 4 , 5 ). The growing global threat of antimicrobial-resistant N. gonorrhoeae has intensified concerns regarding future treatment failure, prompting the WHO to designate N. gonorrhoeae as a high priority pathogen and call for urgent development of new interventions, including vaccines ( 6 – 9 ). Recent clinical observational studies have sparked interest in outer membrane vesicle (OMV)-based vaccine platforms, with serogroup B meningococcal OMV vaccines, such as MeNZB and 4CMenB (Bexsero, GSK), demonstrating moderate cross-protection against gonorrhoea ( 10 , 11 ). This protection, estimated at 33-46% ( 12 – 15 ), is attributed to substantial antigenic similarity between N. meningitidis and N. gonorrhoeae , especially among conserved outer membrane proteins ( 16 ). In response to these clinical findings, the United Kingdom recently introduced targeted use of 4CMenB for gonorrhoea prevention among gay, bisexual, and other men who have sex with men, populations disproportionately affected by gonococcal infection ( 17 ). However, no established correlate of protection exists for gonorrhoea, making early gonococcal vaccine evaluation particularly challenging. While serum bactericidal assays (SBA), evaluating antibody-dependent complement-mediated killing in vitro , are the gold standard recognised correlate of protection for meningococcal disease ( 18 ), they remain an uncertain marker in relation to protection against gonorrhoea. Nevertheless, complement-mediated killing is likely to play a role in protection, as individuals with terminal complement deficiencies (C5b-C9), unable to form the Membrane Attack Complex (MAC), as well as those with C2 deficiency, have increased susceptibility to disseminated gonococcal infection (DGI) ( 19 – 22 ). Building on this foundation, we developed GonoVac, a native OMV (nOMV) vaccine derived from a genetically modified strain of N. gonorrhoeae , GC_0817560 lpxL1 - , designed to reduce reactogenicity while preserving key immunogenic components ( 23 , 24 ). GonoVac induces robust immunogenicity in BALB/c mice, including strong systemic and mucosal IgG responses, immunoglobulin class switching, and high levels of antibody-dependent complement-mediated killing ( 24 ). As with 4CMenB, GonoVac induces relatively low amounts of serum anti-gonococcal IgA and negligible mucosal anti-gonococcal IgA ( 24 ). Nevertheless, we have demonstrated that gonococcal nOMV candidate vaccines accelerate clearance of gonococcal infection in the β-oestradiol mouse model compared with 4CMenB ( 23 ). Most early-stage vaccine studies are conducted in a single inbred mouse strain, often BALB/c mice, which are associated with a Th2 immune phenotype ( 25 – 28 ). This limited scope may not fully capture the immunological variability seen in humans. Indeed, differences in vaccine-induced immune magnitude, kinetics, and durability between inbred and outbred strains of mouse can significantly influence translational relevance. Such variability in vaccine responses due to host genetic factors is well-documented for other pathogens and vaccines, including those against influenza, hepatitis B, and measles, where genetic polymorphisms can influence antibody levels, duration of immunity, and occurrence of non-responsiveness ( 29 – 31 ). While BALB/c mice are often used for investigating humoral immune responses, C57BL/6 mice are associated with Th1 immunity and often used for assessing T cell responses ( 25 , 32 – 34 ). Outbred mouse strains, such as CD1, more closely mimic human genetic diversity, offering an additional layer of insight into vaccine responsiveness ( 35 , 36 ). Durability of immunity is another critical consideration for a gonococcal vaccine. As vaccination strategies are likely to target adolescents prior to sexual debut, protective immune responses must persist for many years to provide meaningful public health benefit ( 37 ), and may vary across different genetic backgrounds. Available clinical effectiveness data suggest that the OMV in the 4CMenB vaccine offer limited duration of protection against gonorrhoea, although interpretation is limited due to reduced power when splitting subjects according to time since vaccination ( 10 ). In this study, we investigated two key aspects of the immune response induced by the GonoVac candidate vaccine in three genetically distinct strains of mouse. First, we evaluated the durability of systemic antibody responses to GonoVac formulated with Al(OH) 3 over a one-year period (49 weeks for C57BL/6 and CD1 mice, 33 weeks for BALB/c mice), including anti-gonococcal IgG titres, subclass distribution, avidity, and SBA titres. The licensed 4CMenB vaccine was used as a comparator, given its partial effectiveness against gonorrhoea in humans and in the murine model against gonococcal lower genital tract infection ( 12 , 13 , 15 , 23 , 38 ). Second, we characterised the immunogenicity of GonoVac formulated with and without Al(OH) 3 , by assessing both humoral responses and cellular immunity (IFN-γ-, IL-4-, IL-17A-producing cells), across three strains of mouse. Therefore, this study collectively evaluates the breadth and persistence of GonoVac-induced immunity, addressing inter-strain variability to support further translation to human clinical trials. 2 Materials and methods 2.1 Strains and growth of N. gonorrhoeae N. gonorrhoeae GC_0817560 used in this study was obtained from the WHO Collaborating Centre for Gonorrhoea and other Sexually Transmitted Infections (Örebro, Sweden). As previously described, the strain was genetically modified to attenuate endotoxin activity by deleting the lpxL1 gene for GonoVac nOMV production ( 23 ). Bacteria were cultured from frozen glycerol stocks on gonococcal agar (GCA) plates supplemented with 2% Vitox (Oxoid, Becton Dickinson, UK), and incubated overnight at 37 °C in 5% CO 2 ( 24 ). For liquid culture, colonies were inoculated into gonococcal broth composed of 15 g/L protease peptone no. 3, 4 g/L K 2 HPO 4 , 1 g/L KH 2 PO 4 , and 5 g/L NaCl (pH 7.2). The medium was supplemented with 1% Kellogg’s supplement I (containing 400 g/L D-glucose, 10 g/L L-glutamine, and 0.002% w/v thiamine pyrophosphate, filter-sterilised using a 0.2 µm filter) ( 39 ). Cultures were incubated at 37 °C with 5% CO 2 under shaking conditions (170 rpm). 2.2 nOMV production GonoVac nOMV were prepared in shake-flasks and bioreactors as previously described ( 23 , 24 ). nOMV were formulated in phosphate-buffered saline (PBS) and sterile-filtered. Total protein content was determined by BCA assay (Thermo Scientific). A brief proteomic summary of GonoVac (N. gonorrhoeae GC_0817560 lpxL1 - nOMV) has previously been described ( 23 ). 2.3 Gonococcal lysate preparation Lysates for ELISA and cellular assays were prepared from N. gonorrhoeae GC_0817560 cultures via mechanical disruption (FastPrep-24) and debris removal by centrifugation and filtration, as previously reported ( 24 ). 2.4 Animals and immunisation All animal procedures received approval from the University of Oxford Animal Welfare and Ethical Review Body and were conducted under UK Home Office licence PP2250582 (Study 1) and PP7685090 (Study 2). Female 6–8-week-old inbred BALB/c and C57BL/6, and outbred CD1 mice (Envigo, UK) were immunised intramuscularly in the tibialis muscle (50 μL total per leg) under light isoflurane anaesthesia. Each vaccine dose contained 5 μg GonoVac in PBS, with or without Al(OH) 3 (Croda). Intermediate blood samples were collected via tail bleed, while terminal samples were obtained by cardiac puncture. Serum was separated after clotting by two cycles of centrifugations (13, 000 x g for 10 min) and stored at -40 °C. Vaginal washes were collected by flushing the vaginal canal three times with 30 μL of PBS each time, giving a total volume of 90 μL. 2.5 ELISA for serum and mucosal antibodies ELISA to quantify total IgG, IgM, IgG isotypes (IgG1, IgG2a, IgG2b, IgG3), and mucosal IgG against N. gonorrhoeae GC_0817560 lysate were carried out as previously described ( 24 ). Briefly, Nunc-Immuno Maxisorp 96-well plates were coated overnight with 6 μg/mL gonococcal lysate in PBS. Plates were blocked with 1% Bovine Serum Albumin (BSA, Sigma Aldrich) in PBS, followed by incubation with serially diluted test samples or standard curves (pooled sera from gonococcal OMV-immunised animals). HRP-conjugated goat anti-mouse secondary antibodies were applied (total IgG: 1:10, 000 Jackson ImmunoResearch; IgG isotypes/IgM: 1:8, 000 SouthernBiotech). Plates were developed using 3, 3′, 5, 5′-Tetramethylbenzidine (TMB) substrate (MP Biomedicals). The colorimetric reaction was stopped with 2 M H 2 SO 4 , and absorbance read at 630 and 450 nm using BioTek microplate reader. Antibody concentrations, expressed in Arbitrary ELISA Units (AEU), were interpolated using a 4-parameter logistic (4PL) model in Gen5 software and normalised to a 1:100 dilution factor for serum. The lower limit of quantification/detection was defined as the end of the linear range of the standard curve, corresponding to 1 AEU multiplied by the minimum dilution factor of 100, i.e. 100 AEU. Accordingly, samples with a titre of ≤100 AEU were considered below the detection limit and reported as 100 AEU. Values below this threshold were not treated as quantifiable measurements. 2.6 Avidity ELISA Anti-gonococcal IgG avidity was assessed by a urea-elution modified ELISA ( 24 ). Each serum sample was plated at a single dilution in duplicate on two separate halves of an ELISA plate. After initial binding and washes, one half of the plate was treated with 50 μL/well of 6 M urea (Sigma Aldrich) in PBS for 30 minutes at room temperature, while the other half, which also contained controls and standard curve serum dilutions, was incubated with PBS. The above ELISA protocol was then followed. Avidity Index (AI) was calculated as: AI (%) = (IgG titre with urea/IgG titre without urea) × 100. 2.7 Serum bactericidal assay SBA was performed as described previously ( 24 ). Briefly, 20 μL of serially diluted heat-inactivated mouse sera in bactericidal buffer (BB; Hank’s Balanced Salt Solution (HBSS; Gibco) containing 0.5% BSA (Sigma-Aldrich)) was incubated with 10 μL N. gonorrhoeae GC_0817560 (6 x 10 4 CFU/mL). A 10 μL aliquot of pooled human IgM/IgG/IgA-depleted human serum (Pel-freez), serving as an external complement source (previously diluted 1:2 in BB, 12.5% final assay concentration), was then added. Reactions were incubated for 45 min at 37 °C with shaking. Live bacterial cells were enumerated by plating onto GC agar. Bactericidal titres were defined as the highest serum dilution yielding ≥50% killing compared to complement-only controls. 2.8 Cellular immune responses Vaccine-induced cellular responses were quantified by FluoroSpot assays (Mabtech, FSP-4144-10) detecting IFN-γ-, IL-4-, and IL-17A-secreting cells, as previously reported ( 24 ). Spleens were harvested and processed into single-cell suspensions using gentleMACS Dissociators and C tubes (Miltenyi Biotec). Cells were treated with RBC lysis buffer, washed, filtered, and resuspended in R10 media (RPMI (Gibco) with 10% of heat-inactivated Foetal Calf Serum (FCS) (Sigma-Aldrich)), 1% L-glutamine (Sigma-Aldrich), 1% Penicillin-Streptomycin (pen/strep; Sigma-Aldrich). Viable cells were counted using a Countess II FL Automated Cell Counter. Cells (2.5 x 10 6 cells/mL) were added to FluoroSpot plates pre-coated with anti-IFN-γ, anti-IL4, and anti-IL17A monoclonal antibodies. N. gonorrhoeae GC_0817560 lysates (75 μg/mL final concentration) with 0.2 µg/mL CD28 as co-stimulus were used for antigen-specific stimulation in triplicate wells. Positive control wells (1 well per sample) contained 25 ng/mL of Phorbol 12-myristate 13-acetate (PMA, Cayman Chemical) and 500 ng/mL of ionomycin (IO, Sigma-Aldrich) (final concentrations). Negative control wells contained unstimulated cells and media only. Cells were stimulated for 24 h, and spots were detected according to manufacturer’s instructions and counted using AID ELISpot software 8.0. Results were averaged from triplicate wells and the unstimulated background control was subtracted. 2.9 Statistical analysis Statistical analyses were performed using GraphPad Prism 10. Data normality was assessed before selecting parametric (ANOVA) or non-parametric (Kruskal–Wallis) tests, followed by appropriate post hoc analyses (Tukey’s or Dunn’s test). Two-way ANOVA with Šidák’s correction was used for investigations involving two factors. Antibody ELISA and SBA data were logarithmically transformed (log10 and log2, respectively) prior to two-way ANOVA to minimise variability. 3 Results 3.1 GonoVac is highly immunogenic in three genetically distinct strains of mouse with serum anti-gonococcal IgG levels that persist unchanged over a year duration in two mouse strains The persistence of the immune response to GonoVac was assessed over a one-year period in three strains of mouse, BALB/c, C57BL/6 and CD1. Ten 6-8-week-old female mice per group were immunised with either two or three doses of GonoVac, produced in shake flasks and formulated with Al(OH) 3 (5 µg GonoVac OMV protein-equivalent/259.5µg Al 3+ ) in PBS, or 5 µg 4CMenB (OMV protein-equivalent) and administered intramuscularly. CD1 and C57BL/6 were monitored for 49 weeks post-first immunisation, while BALB/c mice were sacrificed at 33 weeks post-first immunisation due to the development of tumours with age. As some mice were lost after reaching humane endpoints due to the length of the study, a subset of 5 to 6 randomly selected mice per group was used for the immunogenicity assessment. Serum samples collected at 9 weeks and at terminal time points (33–49 weeks) were analysed to assess anti-gonococcal antibody responses ( Figure 1A ). This analysis aimed to determine (i) the immune response to GonoVac across different mouse strains, (ii) how the response compared with 4CMenB, and (iii) the durability of the immune response over time. Figure 1 Persistence of the serum anti-gonococcal IgG responses induced by 2 or 3 doses of GonoVac/Al(OH) 3 or 4CMenB in C57BL/6, BALB/c, and CD1 mice. (A) Immunisation schedule: 6-8-week-old female mice were immunised intramuscularly at weeks 0 and 3 or 0, 3 and 6 with 5 µg of flask-produced GonoVac/Al(OH) 3 or 5 µg of 4CMenB (OMV protein-equivalent) Figure made with https://www.biorender.com/ . (B) Serum anti-gonococcal IgG responses were measured by ELISA with N. gonorrhoeae GC_0817560 lysate as antigen. Responses were assessed at week 9 and at the end of the study (week 49 or 33) in all strains of mouse. Statistical test: 2-way ANOVA with Šídák’s correction for multiple comparisons. P values: **p<0.01, ***p<0.001. Individual mice are represented by circles. Horizontal bars signify medians ± 95% CI. n=5–6 mice/group. (C) Persistence of the serum anti-gonococcal IgG response between week 9 and week 33/49 post first immunisation. Statistical tests: 2-way ANOVA with Šídák’s correction for multiple comparisons. Circles represent medians ± 95% CI. n=5–6 mice/group. Significant differences between week 9 and terminal bleed IgG titres are
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