Planning for a Gonococcal Vaccine: A Narrative Review of Vaccine Development and Public Health Implications

Adjuvant-dependent impacts on vaccine-induced humoral responses and protection in preclinical models of nasal and genital colonization by pathogenic Neisseria

Neisseria gonorrhoeae, which causes the sexually transmitted infection gonorrhea and Neisseria meningitidis, a leading cause of bacterial meningitis and septicemia, are closely related human-restricted pathogens that inhabit distinct primary mucosal niches. While successful vaccines against invasive meningococcal disease have been available for decades, the rapid rise in antibiotic resistance has led to an urgent need to develop an effective gonococcal vaccine. Several surface antigens are shared among these two pathogens, making cross-species protection an exciting prospect. However, the type of vaccine-mediated immune response required to achieve protection against respiratory versus genital infection remains ill defined. In this study, we utilize well established mouse models of female lower genital tract colonization by N. gonorrhoeae and upper respiratory tract colonization by N. meningitidis to examine the performance of transferrin binding protein B (TbpB) vaccines formulated with immunologically distinct vaccine adjuvants. We demonstrate that vaccine-mediated protection is influenced by the choice of adjuvant, with Th1/2-balanced adjuvants performing optimally against N. gonorrhoeae, and both Th1/2-balanced and Th2-skewing adjuvants leading to a significant reduction in N. meningitidis burden. We further establish a lack of correlation between protection status and the humoral response or bactericidal titre. Combined, this work supports the feasibility for a single vaccine formulation to achieve pan-neisserial coverage.

Cost-effectiveness of 4CMenB Vaccination Against Gonorrhea: Importance of Dosing Schedule, Vaccine Sentiment, Targeting Strategy, and Duration of Protection

BACKGROUND

Observational evidence suggests the 4CMenB meningococcal vaccine may partially protect against gonorrhea, with 1 dose being two-thirds as protective as 2 doses. We examined the cost-effectiveness of vaccinating men who have sex with men (MSM) in England, with 1- or 2-dose primary vaccination.

METHODS

Integrated transmission-dynamic health-economic modeling explored the effects of targeting strategy, first- and second-dose uptake levels, and duration of vaccine protection, using observational estimates of vaccine protection.

RESULTS

Vaccination with 1 or 2 primary doses is always cost-saving, irrespective of uptake, although vaccine sentiment is an important determinant of impact and cost-effectiveness. The most impactful and cost-effective targeting is offering "vaccination according to risk" (VaR), to all patients with gonorrhea plus those reporting high numbers of sexual partners. If VaR is not feasible to implement then the more restrictive strategy of "vaccination on diagnosis" (VoD) with gonorrhea is cost-effective, but much less impactful. Under conservative assumptions, VaR (2-dose) saves £7.62M (95% credible interval [CrI], 1.15-17.52) and gains 81.41 (95% CrI, 28.67-164.23) quality-adjusted life-years (QALYs) over 10 years; VoD (2-dose) saves £3.40M (95% CrI, .48-7.71) and gains 41.26 (95% CrI, 17.52-78.25) QALYs versus no vaccination. Optimistic versus pessimistic vaccine-sentiment assumptions increase net benefits by approximately 30% (VoD) or approximately 60% (VaR).

CONCLUSIONS

At UK costs, targeted 4CMenB vaccination of MSM gains QALYs and is cost-saving at any uptake level. Promoting uptake maximizes benefits and is an important role for behavioral science.

Effectiveness of MenB-4C Vaccine Against Gonorrhea: A Systematic Review and Meta-analysis

BACKGROUND

There is no licensed vaccine against gonorrhea, but Neisseria meningitidis serogroup B outer membrane vesicle-based vaccines, such as MenB-4C, may offer cross-protection against gonorrhea. This systematic review and meta-analysis synthesized the published literature on MenB-4C vaccine effectiveness against gonorrhea.

METHODS

We conducted a literature search of electronic databases (PubMed, Medline, Embase, Global Health, Scopus, Google Scholar, CINAHL, and Cochrane Library) to identify peer-reviewed articles published in English from 1 January 2013 to 11 September 2024 that reported MenB-4C vaccine effectiveness estimates against gonorrhea and gonorrhea/chlamydia coinfection and the duration of MenB-4C vaccine-induced protection. We estimated pooled MenB-4C vaccine effectiveness (≥1 dose) against gonorrhea using the DerSimonian-Laird random effects model.

RESULTS

Eight articles met our eligibility criteria. Receipt of ≥1 dose of MenB-4C vaccine was 23% to 47% effective against gonorrhea. Two doses of MenB-4C vaccine were 33% to 40% effective against gonorrhea, and 1 dose of MenB-4C vaccine was 26% effective. MenB-4C vaccine effectiveness against gonorrhea/chlamydia coinfection was mixed, with 2 studies reporting effectiveness estimates of 32% and 44% and 2 other studies showing no protective effect. MenB-4C vaccine effectiveness against gonorrhea was comparable in people with HIV (44%) and people without HIV (23%-47%). Pooled MenB-4C vaccine effectiveness (≥1 dose) against gonorrhea was 32.4%. One study concluded that MenB-4C vaccine effectiveness against gonorrhea may wane approximately 36 months postvaccination.

CONCLUSIONS

MenB-4C vaccine is moderately effective against gonorrhea in various populations. Prospective clinical trials that assess the efficacy of MenB-4C against gonorrhea, gonorrhea/chlamydia coinfection, and duration of protection are warranted to strengthen this evidence.

Management and prevention of Neisseria meningitidis and Neisseria gonorrhoeae infections in the context of evolving antimicrobial resistance trends

PURPOSE

To describe the relationships between Neisseria meningitidis (NM) and Neisseria gonorrhoeae (NG) at genetic, population, and individual levels; to review historical trends in antimicrobial resistance (AMR); to review the treatment and preventive landscapes and explore their potential impact on AMR.

METHODS

A narrative literature search was conducted in PubMed, with searches restricted to 2003-2023 and additional articles included based on expertise.

RESULTS

NM and NG are closely related bacterial pathogens causing invasive meningococcal disease (IMD) and gonorrhea, respectively. NM can currently be treated with most antibiotics and generally has a wild-type susceptibility profile, whereas NG is increasingly resistant even in the first line of treatment. These pathogens share 80-90% genetic identity and can asymptomatically cohabit the pharynx. While AMR has historically been rare for NM, recent reports show this to be an emerging clinical concern. Extensively drug-resistant NG are reported globally, with data available from 73 countries, and can lead to treatment failure. Importantly, Neisseria commensals within the normal microbiota in the pharynx can act as a genetic reservoir of resistance to extended-spectrum cephalosporins. Novel oral antibiotics are urgently needed to treat a growing threat from antibiotic-resistant NG, recognized as a major global concern to public health by the World Health Organization. Numerous vaccines are available to prevent IMD, but none are approved for gonorrhea. Research to identify suitable candidates is ongoing.

CONCLUSION

Holistic management of AMR in IMD and gonorrhea should couple judicious use of existing antibiotics, optimization of vaccination programs, and development of novel antibiotics and vaccines.

Effectiveness of a serogroup B meningococcal vaccine against gonorrhea: A retrospective study

BACKGROUND

Outer membrane vesicle (OMV) meningococcal serogroup B (MenB) vaccines might be protective against gonorrhea. We evaluated the effectiveness of MenB-4C, an OMV MenB vaccine, against gonorrhea.

METHODS

We identified gonococcal mono-infections, chlamydial mono-infections, and gonococcal/chlamydial co-infections among persons aged 15-30 years in the electronic health records of Kaiser Permanente Northern California during 2016-2021. We determined MenB-4C vaccination status (vaccinated [≥1 MenB-4C vaccine dose] or unvaccinated [MenB-4C vaccine naïve]) at each infection. We used log-binomial regression with generalized estimating equations to calculate adjusted prevalence ratios (APR) and 95 % confidence intervals (CI) to determine if MenB-4C vaccination was protective against gonococcal mono-infections compared to chlamydial mono-infection. We also evaluated if MenB-4C vaccination was protective against gonococcal/chlamydial co-infections. Because of concerns with small sample size of vaccinated persons, we estimated effects using a limited model (adjusting for race/ethnicity only) and an expanded model (adjusting for additional potential confounders).

RESULTS

Of 68,454 persons, we identified 558 (0.8 %) MenB-4C vaccinated persons and 85,393 infections (13,000 gonococcal mono-infections, 68,008 chlamydial mono-infections, and 4385 gonococcal/chlamydial co-infections). After adjusting for race/ethnicity, MenB-4C vaccination was 23 % protective against gonococcal mono-infection compared to chlamydial mono-infection (APR = 0.77, 95 % CI = 0.64-0.99) in the limited model but not in the expanded model.

CONCLUSION

MenB-4C vaccination was protective against gonococcal mono-infection, independent of race/ethnicity. This protective effect was not observed when other potential confounders were included in the analysis. Protection against gonococcal/chlamydial co-infection was not observed. Efficacy data from clinical trials are needed.

Intranasal trivalent candidate vaccine induces strong mucosal and systemic immune responses against Neisseria gonorrhoeae

The spread of multidrug-resistant strains of Neisseria gonorrhoeae poses a great challenge in gonorrhea treatment. At present, vaccination is the best strategy for gonorrhea control. However, given the extensive antigenic variability of N. gonorrhoeae, the effectiveness of monovalent vaccines is limited. Therefore, increasing the coverage of vaccination by using a multivalent vaccine may be more effective. In this study, a trivalent vaccine comprising three conserved antigens, namely, the App passenger domain, MetQ, and neisserial heparin binding antigen (NHBA), was constructed, and its protective effect was evaluated. Trivalent vaccines induced stronger circulating IgG and IgA antibody responses in mice than monovalent vaccines, in addition to eliciting Th1, Th2, and Th17 immune responses. Antiserum generated by the trivalent vaccine killed N. gonorrhoeae strains (homologous FA1090 and heterologous FA19), exhibiting superior bactericidal capacity than NHBA and MetQ vaccine antisera against N. gonorrhoeae, but similar capacities to those of the App vaccine antiserum. In addition, the trivalent vaccine antiserum achieved greater inhibition of N. gonorrhoeae FA1090 strain adherence to ME-180 cells compared to that elicited by the monovalent vaccine antiserum. In a mouse vaginal infection model, the trivalent vaccine was modestly effective (9.2% decrease in mean area under curve compared to the pCold-TF control mice), which was somewhat better than the protection seen with the monovalent vaccines. Our findings suggest that recombinant multivalent vaccines targeting N. gonorrhoeae exhibit advantages in protective efficacy compared to monovalent vaccines, and future research on multivalent vaccines should focus on optimizing different antigen combinations.

Vaccine effectiveness and impact of meningococcal vaccines against gonococcal infections: A systematic review and meta-analysis

OBJECTIVES

To systematically review and synthesis the evidence of vaccine effectiveness (VE) and impact (VI) of meningococcal vaccines in preventing gonorrhoea.

METHODS

We systematically evaluated studies. Literature searches were conducted in PubMed, Embase, Cochrane Library, CINAHL, Google Scholar, clinical trial registries, and major health and immunisation conferences. Meta-analysis was performed with the DerSimonian-Laird random-effects model to estimate the pooled VE.

RESULTS

Twelve studies met the criteria for inclusion. VE of meningococcal B (MenB) outer membrane vesicle (OMV) vaccines was evaluated in nine studies, with one study evaluating a non-OMV vaccine, MenB-FHbp. The majority of studies targeted individuals aged 15-30 years. Adjusted VE for OMV vaccines against gonorrhoea ranged from 22% to 46%. MenB-FHbp did not show protection against gonorrhoea. The pooled VE estimates of OMV vaccines against any gonorrhoea infection following the full vaccine series were 33-34%. VI was assessed for 4CMenB in Canada and Australia, for VA-MENGOC-BC in Cuba; and for MenBvac in Norway. VI ranged from a 30% to 59% reduction in gonorrhoea incidence.

CONCLUSIONS

4CMenB and other MenB-OMV vaccines show moderate effectiveness against gonorrhoea. Further research is required to explore the factors associated with vaccine protection, informing more effective vaccination strategies for the management of gonococcal infections.

The Management of Gonorrhea in the Era of Emerging Antimicrobial Resistance: What Primary Care Clinicians Should Know

Gonorrhea rates continue to rise in the United States and Neisseria gonorrhoeae's propensity to develop resistance to all therapies used for treatment has complicated the management of gonorrhea. Ceftriaxone is the only remaining highly effective recommended regimen for gonococcal treatment and few new anti-gonococcal antimicrobials are being developed. The 2021 CDC STI Treatment Guidelines increased the dose of ceftriaxone to 500 mg (1 g if ≥ 150 kg) for uncomplicated infections. It is recommended that all clinicians should be aware of antimicrobial resistant gonorrhea and be able to appropriately manage any suspected gonorrhea treatment failure case.

Promising developments in gonococcal vaccines

PURPOSE OF REVIEW

While effective vaccines to prevent invasive infections by Neisseria meningitidis have been deployed around the world, development of a vaccine to prevent Neisseria gonorrhoeae has lagged. After multiple failed vaccine candidates, vaccine development for N. gonorrhoeae is showing promise for the first time in several decades. This review highlights recent progress in the field.

RECENT FINDINGS

Vaccines containing outer-membrane vesicles (OMV) have been used to manage outbreaks of the serogroup B N. meningitidis in a number of countries. Epidemiologic studies indicate these vaccination campaigns were associated with reductions in reported N. gonorrhoeae infections. Recently, a serogroup B N. meningitidis vaccine containing both recombinant antigens and OMV has been licensed through much of the world. Epidemiologic studies also demonstrate associations between 4CMenB immunization and reduced N. gonorrhoeae infections. Additionally, mathematical modeling studies have begun to identify potential strategies for vaccine deployment to maximize reduction of infections.

SUMMARY

After several decades with little progress towards an effective gonococcal vaccine, large observational studies have provided evidence that a new generation of group B N. meningitidis vaccines containing OMV have serendipitously restarted the field. Ongoing clinical trials will soon provide definitive evidence regarding the efficacy of these vaccines in preventing N. gonorrhoeae infection.

Public willingness to receive chlamydia, gonorrhea, syphilis, and trichomoniasis vaccines: a scoping review

BACKGROUND

Sexually transmitted infections (STIs) like chlamydia, gonorrhea, syphilis, and trichomoniasis contribute significantly to global morbidity and mortality. Researchers are pursuing vaccines for these STIs, and a clinical trial is currently underway for a chlamydia vaccine. However, there is little research available on individuals' willingness to receive chlamydia, gonorrhea, syphilis, and trichomoniasis vaccines. The purpose of this analysis was to map the existing literature we have on individuals' willingness to receive these bacterial/parasitic STI vaccines and understand what information on vaccine acceptability is still needed.

METHODS

We searched seven databases for literature on STI vaccine acceptability, then conducted title/abstract and full-text reviews to assess eligibility. All reviews and abstractions were conducted blindly by two reviewers, with discrepancies settled by discussion or the input of a third reviewer.

RESULTS

Eight of the original 2,259 texts of interest met inclusion criteria. After data abstraction, we found that gonorrhea was the most commonly examined, followed by chlamydia and syphilis. Trichomoniasis vaccine acceptability was not reported. Most texts reported high acceptability, but there did not appear to be data describing how vaccine characteristics affect acceptability. Similarly, while the literature covers a variety of populations, most of the study populations were based out of the United States or Canada and were patrons of healthcare facilities or participants from a larger health intervention study. Therefore, more information is needed on populations outside North America, and on groups with lower healthcare access and utilization.

CONCLUSION

As the incidence of bacterial and parasitic STIs increase, and as we grow nearer vaccines for these illnesses, understanding how likely the public is to accept and receive these vaccines is crucial to their success. While the existing literature describes STI vaccine acceptability in a variety of populations, their overall number is small. More research into STI vaccine acceptability outside of North America, and especially examining how factors like number of doses, timing, and cost influence vaccine acceptability is needed to ensure effective future vaccine rollouts.

Real-world implementation of 4-component meningococcal serogroup B vaccine (4CMenB): implications for clinical practices

INTRODUCTION

Invasive meningococcal disease due to serogroup B (MenB) is an uncommon but life-threatening disease. The 4-component meningococcal serogroup B vaccine (4CMenB) is the only MenB vaccine with real-world evidence supporting a reduction in incidence without safety concerns.

AREAS COVERED

We reviewed recommendations and real-world implementation of 4CMenB in National Immunization Programs (NIPs) and implications for clinical practice through a non-systematic literature search.

EXPERT OPINION

4CMenB is registered in 45 countries, 33 of which recommend it clinically: nine for infants, children, adolescents, and high-risk groups; 11 for infants and high-risk groups; the US for individuals aged 16-23 years and high-risk groups; two for infants; 10 for high-risk groups and/or outbreak control. Dosing schedule varies between countries. To date, nine countries include 4CMenB in their NIP: UK, Andorra, Ireland, Italy, San Marino, Lithuania, Malta, Czech Republic, and Portugal. Australia funds it for Aboriginal and Torres Strait Islander children under 2 years, and high-risk individuals. South Australia funds for all infants and adolescents. Many factors influenced introduction into NIPs: disease burden, public awareness, cost-effectiveness, prior meningococcal vaccination programs, efficacy and safety profile. In the future, more countries might consider including 4CMenB in their NIP due to growing evidence on effectiveness and safety.

Gonococcal invasion into epithelial cells depends on both cell polarity and ezrin

Neisseria gonorrhoeae (GC) establishes infection in women from the cervix, lined with heterogeneous epithelial cells from non-polarized stratified at the ectocervix to polarized columnar at the endocervix. We have previously shown that GC differentially colonize and transmigrate across the ecto and endocervical epithelia. However, whether and how GC invade into heterogeneous cervical epithelial cells is unknown. This study examined GC entry of epithelial cells with various properties, using human cervical tissue explant and non-polarized/polarized epithelial cell line models. While adhering to non-polarized and polarized epithelial cells at similar levels, GC invaded into non-polarized more efficiently than polarized epithelial cells. The enhanced GC invasion in non-polarized epithelial cells was associated with increased ezrin phosphorylation, F-actin and ezrin recruitment to GC adherent sites, and the elongation of GC-associated microvilli. Inhibition of ezrin phosphorylation inhibited F-actin and ezrin recruitment and microvilli elongation, leading to a reduction in GC invasion. The reduced GC invasion in polarized epithelial cells was associated with non-muscle myosin II-mediated F-actin disassembly and microvilli denudation at GC adherence sites. Surprisingly, intraepithelial GC were only detected inside epithelial cells shedding from the cervix by immunofluorescence microscopy, but not significantly in the ectocervical and the endocervical regions. We observed similar ezrin and F-actin recruitment in exfoliated cervical epithelial cells but not in those that remained in the ectocervical epithelium, as the luminal layer of ectocervical epithelial cells expressed ten-fold lower levels of ezrin than those beneath. However, GC inoculation induced F-actin reduction and myosin recruitment in the endocervix, similar to what was seen in polarized epithelial cells. Collectively, our results suggest that while GC invade non-polarized epithelial cells through ezrin-driven microvilli elongation, the apical polarization of ezrin and F-actin inhibits GC entry into polarized epithelial cells.

Neisseria gonorrhoeae (GC) causes gonorrhea in women by infecting the female reproductive tract. GC entry of epithelial cells has long been observed in patients’ biopsies and studied in various types of epithelial cells. However, how GC invade into the heterogeneous epithelia of the human cervix is unknown. This study reveals that both the expression level of ezrin, an actin-membrane linker protein, and the polarization of ezrin-actin networks in epithelial cells regulate GC invasion. GC interactions with non-polarized squamous epithelial cells expressing ezrin induce ezrin activation, ezrin-actin accumulation, and microvilli elongation at GC adherent sites, leading to invasion. Low ezrin expression levels in the luminal ectocervical epithelial cells are associated with low levels of intraepithelial GC. In contrast, apical polarization of ezrin-actin networks in columnar endocervical epithelial cells reduces GC invasion. GC interactions induce myosin activation, which causes disassembly of ezrin-actin networks and microvilli modification at GC adherent sites, extending GC-epithelial contact. Expression of opacity-associated proteins on GC promotes GC invasion by enhancing ezrin-actin accumulation in squamous epithelial cells and inhibiting ezrin-actin disassembly in columnar endocervical epithelial cells. Thus, reduced ezrin expression and ezrin-actin polarization are potential ways for cervical epithelial cells to curtail GC invasion.

Vaccine Candidates for the Control and Prevention of the Sexually Transmitted Disease Gonorrhea

The World Health Organization (WHO) has placed N. gonorrhoeae on the global priority list of antimicrobial resistant pathogens and is urgently seeking the development of new intervention strategies. N. gonorrhoeae causes 86.9 million cases globally per annum. The effects of gonococcal disease are seen predominantly in women and children and especially in the Australian Indigenous community. While economic modelling suggests that this infection alone may directly cost the USA health care system USD 11.0–20.6 billion, indirect costs associated with adverse disease and pregnancy outcomes, disease prevention, and productivity loss, mean that the overall effect of the disease is far greater still. In this review, we summate the current progress towards the development of a gonorrhea vaccine and describe the clinical trials being undertaken in Australia to assess the efficacy of the current formulation of Bexsero^® in controlling disease.