The serogroup B meningococcal outer membrane vesicle-based vaccine 4CMenB induces cross-species protection against Neisseria gonorrhoeae

Knowledge, uptake and intention to use antibiotic post-exposure prophylaxis and meningococcal B vaccine (4CMenB) for gonorrhoea among a large, online community sample of men and gender-diverse individuals who have sex with men in the UK

Novel STI prevention interventions, including doxycycline post-exposure prophylaxis (doxyPEP) and meningococcal B vaccination (4CMenB) against gonorrhoea, have been increasingly examined as tools to aid STI control. There is evidence of the efficacy of doxyPEP in preventing bacterial STIs; however, limited data exist on the extent of use in the UK. We examined self-reported knowledge and use of antibiotic post-exposure prophylaxis (PEP), and intention to use (ITU) doxyPEP and 4CMenB among a large, community sample of men and gender-diverse individuals who have sex with men in the UK. Using data collected by the RiiSH survey (November/December 2023), part of a series of online surveys of men and other gender-diverse individuals in the UK, we describe (%, [95% CI]) self-reported knowledge and use of antibiotic PEP (including doxyPEP) and doxyPEP and 4CMenB ITU. Using bivariate and multivariable logistic regression, we examined correlates of ever using antibiotic PEP, doxyPEP ITU, and 4CMenB ITU, respectively, adjusting for sociodemographic characteristics and a composite marker of sexual risk defined as reporting (in the last three months): ≥5 condomless anal sex partners, bacterial STI diagnosis, chemsex, and/or meeting partners at sex-on-premises venues, sex parties, or cruising locations. Of 1,106 participants (median age: 44 years [IQR: 34-54]), 34% (30%-37%) knew of antibiotic PEP; 8% (6%-10%) ever reported antibiotic PEP use. Among those who did, most reported use in the last year (84%, 73/87) and exclusively used doxycycline (69%, 60/87). Over half of participants reported doxyPEP ITU (51% [95% CI: 47%-56%], 568/1,106) while over two-thirds (64% [95% CI: 60%-69%], 713/1,106) reported 4CMenB ITU. Participants with markers of sexual risk and with uptake of other preventative interventions were more likely to report ever using antibiotic PEP as well as doxyPEP and 4CMenB ITU, respectively. HIV-PrEP users and people living with HIV (PLWHIV) were more likely to report antibiotic PEP use and doxyPEP and 4CMenB vaccination ITU than HIV-negative participants not reporting recent HIV-PrEP use. Findings demonstrate considerable interest in the use of novel STI prevention interventions, more so for 4CMenB vaccination relative to doxyPEP. Fewer than one in ten participants had reported ever using antibiotic PEP, with most using appropriate, evidence-based antibiotics. The use of antibiotic PEP and the report of doxyPEP ITU and 4CMenB ITU was more common among those at greater risk of STIs.

Protection against N. gonorrhoeae induced by OMV-based Meningococcal Vaccines are associated with cross-species directed humoral and cellular immune responses

Limited protective immunologic responses to natural N. gonorrhoeae infection and a lack of knowledge about mechanisms of protection have hampered development of an effective vaccine. Recent studies in humans and mice have found meningococcal outer membrane vesicle-containing vaccines (OMV) induce cross species immune responses against gonococci and are associated with protection. The exact mechanisms or how humoral and cellular immunity are related to protection, remain unclear. To study this, we immunized mice with two meningococcal OMV-containing vaccines known to accelerate clearance of N. gonorrhoeae , 4CMenB and OMV from an engineered N. meningitidis strain lacking major surface antigens PorA, PorB, and Rmp (MC58 ΔABR). We assessed serologic and cellular immune signatures associated with these immunizations and assessed bacterial clearance in the mice using a vaginal/cervical gonococcal infection model. Mice immunized with 4CMenB or MC58 ΔABR demonstrated shortened courses of recovery of vaginal N. gonorrhoeae compared to control mice immunized with alum alone. Vaccination with 4CMenB or MC58ΔABR OMV elicited serum and vaginal cross-reactive anti-Ng-OMV antibody responses that were augmented after vaginal challenge with N. gonorrhoeae . Further, splenocytes in 4CMenB and MC58 ΔABR immunized mice exhibited elevated cytokine production after restimulation with heterologous N. gonorrhoeae OMV when compared to splenocytes from Alum immunized mice. We further tested for correlations between bacterial burden and the measured anti-gonococcal immune responses within each vaccination group and found different immunologic parameters associated with reduced bacterial burden for each vaccine. Our findings suggest the cross-protection against gonococcal infection induced by different meningococcal OMV vaccines is likely multifactorial and mediated by different humoral and cellular immune responses induced by these two vaccines.

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.

NHBA antibodies elicited by 4CMenB vaccination are key for serum bactericidal activity against Neisseria gonorrhoeae

The 4CMenB (BexseroR) vaccine contains detergent-extracted outer membrane vesicles (OMVs) from a Neisseria meningitidis (Nm) group B strain NZ98/254 and three recombinant Nm protein antigens: Neisseria adhesin A (NadA), Factor H binding protein (FHbp, as the C-terminal protein in the GNA2091-FHbp fusion), and Neisserial Heparin Binding Antigen (NHBA, as the N-terminal protein in the NHBA-GNA1030 fusion). Previous work has shown that 4CMenB generates serum antibodies to Nm and Neisseria gonorrhoeae (Ng) OMV proteins and lipooligosaccharide (LOS). Mounting evidence indicates 4CMenB can partially protect against mucosal infections with Ng. The immunologic basis for Ng cross protection remains to be fully elucidated. Ten paired human sera obtained pre- and post-immunization with 4CMenB (1 month after a third vaccine dose) were used in ELISAs and in Western blots to determine IgG and IgA serum responses to OMVs from Nm strain NZ98/254 (OMVNm) and two Ng strains, 1291 and CNG20 (OMVNg), and gonococcal recombinant NHBA (rNHBANg) proteins. Post 4CMenB sera, but not pre-sera, showed strong IgG and variable IgA responses to the OMVNm but lower (2-11-fold difference in signal intensity) recognition of OMVNg. All post (not pre) 4CMenB sera showed strong IgG, but variable IgA, recognition of rNHBANg by ELISAs and Western blots. Three post 4CMenB sera at 10% (v/v) concentration had serum bactericidal activity (SBA) against Ng strains 1291 and CNG20 (~30-40% killing), not seen in paired pre-sera. These data confirmed 4CMenB-induced cross-reactive functional antibody responses to Ng. In competitive SBA assays, in which sera were pre-incubated with rNHBA, minimal SBA against Nm strain NZ98/254 was titrated away. However, most of the SBA against Ng strains 1291 and CNG20 required NHBA-specific antibodies, and the Δnhba mutants were resistant to killing by post 4CMenB sera. Removing NHBA-specific and LOS-specific OMV antibodies simultaneously decreased SBA significantly more than the sum of removing individual antibodies alone, suggesting synergy between anti-NHBA and anti-OMV antibodies. Anti- NHBANm antibodies induced by 4CMenB vaccination cross react with NHBANg and substantially contribute to the bactericidal response toward Ng induced by the vaccine.

Breakthrough Rectal Neisseria gonorrhoeae Infections After Meningococcal B Vaccination: Microbiological and Clinical Features

Background

4CMenB appears to be effective in reducing Neisseria gonorrhoeae (Ng) infections. Aims are to assess factors associated with breakthrough rectal Ng after 4CMenB and evaluate clinical and microbiological characteristics of breakthrough infections compared with before vaccination.

Methods

This was a retrospective study of gay, bisexual, and other men who have sex with men (GBMSM) vaccinated with 4CMenB (2 doses) between 2017 and 2023 at the San Raffaele Scientific Institute for Research, Hospitalization and Healthcare (IRCCS San Raffaele Scientific Institute), Milan, Italy, and tested for rectal Ng. Rectal Ng infection is considered breakthrough if it occurs >1 month after the second 4CMenB dose and with positive nucleic acid amplification test (NAAT) result. Follow-up was from July 2017 (first 4CMenB vaccination) to November 2023 (data freeze). Rectal Ng was screened with both NAAT and gonococcal-specific cultures. Characteristics of individuals with or without breakthrough Ng and of Ng infections before or after 4CMenB were compared using Mann-Whitney and χ2/Fisher tests.

Results

Overall, 473 GBMSM vaccinated with 4CMenB were included, with a median age (interquartile range) of 43 (37-51) years; 451 of 473 were living with human immunodeficiency virus. The percentage of NAAT-positive rectal Ng swab samples was 76 of 957 (7.7%) after 4CMenB and 51 of 456 (11.1%) before. Breakthrough rectal Ng after baseline were 76 in 57 of 473 people. People with rectal Ng after 4CMenB were younger, more likely to have a previous sexually transmitted infection, and had more sexual partners than those without (all P < .001). Breakthrough rectal Ng infections were less frequently symptomatic (34.2% vs 66.7%; P = .001) and more likely with negative gonococcal-specific culture (55.3% vs 19.6%; P < .001) compared with before vaccination.

Conclusions

Breakthrough rectal Ng infections after 4CMenB were 76 in 57/473 people, preferentially identified in GBMSM with higher-risk sexual behaviors, were less often symptomatic, and more often with negative gonococcal-specific cultures, suggesting lower infection virulence.

Tackling immunosuppression by Neisseria gonorrhoeae to facilitate vaccine design

Gonorrhoea, caused by Neisseria gonorrhoeae, is a common sexually transmitted infection. Increasing multi-drug resistance and the impact of asymptomatic infections on sexual and reproductive health underline the need for an effective gonococcal vaccine. Outer membrane vesicles (OMVs) from Neisseria meningitidis induce modest cross-protection against gonococcal infection. However, the presence of proteins in OMVs derived from N. gonorrhoeae that manipulate immune responses could hamper their success as a vaccine. Here we modified two key immunomodulatory proteins of the gonococcus; RmpM, which can elicit 'blocking antibodies', and PorB, an outer membrane porin which contributes to immunosuppression. As meningococcal PorB has adjuvant properties, we replaced gonococcal PorB with a meningococcal PorB. Immunisation with OMVs from N. gonorrhoeae lacking rmpM and expressing meningococcal porB elicited higher antibody titres against model antigens in mice compared to OMVs with native PorB. Further, a gonococcal protein microarray revealed stronger IgG antibody responses to a more diverse range of antigens in the Nm PorB OMV immunised group. Finally, meningococcal PorB OMVs resulted in a Th1-skewed response, exemplified by increased serum IgG2a antibody responses and increased IFNɣ production by splenocytes from immunised mice. In summary, we demonstrate that the replacement of PorB in gonococcal OMVs enhances immune responses and offers a strategy for gonococcal vaccine development.

Development and Validation of Multiplex Assays for Mouse and Human IgG and IgA to Neisseria gonorrhoeae Antigens

There is an urgent need for vaccines against Neisseria gonorrhoeae, the causative agent of gonorrhea. Vaccination with an outer membrane vesicle-based Neisseria meningitidis vaccine provides some protection from N. gonorrhoeae; however, the mechanisms underlying this cross-protection are unknown. To address this need, we developed multiplexed bead-based assays for the relative quantification of human and mouse IgG and IgA against N gonorrhoeae antigens. The assays were evaluated for analyte independence, dilutional linearity, specificity, sensitivity, intra- and interassay variability, and robustness to sample storage conditions. The assay was then used to test samples from mice and humans immunized with an N meningitidis outer membrane vesicle vaccine.

Urgent Need to Understand and Prevent Gonococcal Infection: From the Laboratory to Real-World Context

Neisseria gonorrhoeae is widespread globally. Primary prevention is unsuccessful and antimicrobial resistance threatens optimal management. There is no specific vaccine and natural infection studies show that N gonorrhoeae can avoid and suppress immune responses. In addition to extensive variation in expression and specificity of many gonococcal surface antigens, it induces a robust inflammatory response through the Th17 pathway with a large influx of neutrophils and inflammatory cytokines but evades macrophages. The Th1- and Th2-mediated response is suppressed, resulting in low, short-lived antibody titers. Real-world evidence suggests that gonorrhea cases are reduced among recipients of Neisseria meningitidis group B vaccines containing outer membrane vesicles (OMVs). Although the first randomized trial of an OMV-containing MenB vaccine against N gonorrhoeae infection did not show statistically significant vaccine efficacy, ongoing trials might shed further light. Several candidate vaccine antigens for a gonococcal-specific vaccine are being evaluated preclinically but only one has reached clinical trials.

Doxycycline prophylaxis and meningococcal group B vaccine to prevent bacterial sexually transmitted infections in France (ANRS 174 DOXYVAC): a multicentre, open-label, randomised trial with a 2 × 2 factorial design

BACKGROUND

Increased rates of sexually transmitted infections (STIs) are reported among men who have sex with men (MSM) and new interventions are needed. We aimed to assess whether post-exposure prophylaxis (PEP) with doxycycline could reduce the incidence of chlamydia or syphilis (or both) and whether the meningococcal group B vaccine (4CMenB) could reduce the incidence of gonorrhoea in this population.

METHODS

ANRS 174 DOXYVAC is a multicentre, open-label, randomised trial with a 2 × 2 factorial design conducted at ten hospital sites in Paris, France. Eligible participants were MSM aged 18 years or older, HIV negative, had a history of bacterial STIs within the 12 months before enrolment, and who were already included in the ANRS PREVENIR study (a cohort of MSM using pre-exposure prophylaxis with tenofovir and emtricitabine for HIV prevention). Participants were randomly assigned (2:1) to doxycycline PEP (two pills of 100 mg each orally within 72 h after condomless sex, with no more than three doses of 200 mg per week) or no PEP groups and were also randomly assigned (1:1) to the 4CMenB vaccine (GlaxoSmithKline, Paris, France; two intramuscular injections at enrolment and at 2 months) or no vaccine groups, using a computer-generated randomisation list with a permuted fixed block size of four. Follow-up occurred for at least 12 months (with visits every 3 months) up to 24 months. The coprimary outcomes were the risk of a first episode of chlamydia or syphilis (or both) after the enrolment visit at baseline for the doxycycline intervention and the risk of a first episode of gonorrhoea starting at month 3 (ie, 1 month after the second vaccine dose) for the vaccine intervention, analysed in the modified intention-to-treat population (defined as all randomly assigned participants who had at least one follow-up visit). This trial is registered with ClinicalTrials.gov, NCT04597424 (ongoing).

FINDINGS

Between Jan 19, 2021, and Sept 19, 2022, 556 participants were randomly assigned. 545 (98%) participants were included in the modified intention-to-treat analysis for the doxycycline PEP and no PEP groups and 544 (98%) were included for the 4CMenB vaccine and no vaccine groups. The median follow-up was 14 months (IQR 9-18). The median age was 40 years (34-48) and all 545 participants were male. There was no interaction between the two interventions (p≥0·1) for the primary outcome. The incidence of a first episode of chlamydia or syphilis (or both) was 8·8 per 100 person-years (35 events in 362 participants) in the doxycycline PEP group and 53·2 per 100 person-years (80 events in 183 participants) in the no PEP group (adjusted hazard ratio [aHR] 0·17 [95% CI 0·12-0·26]; p<0·0001). The incidence of a first episode of gonorrhoea, starting from month 3 was 58·3 per 100 person-years (103 events in 274 participants) in the 4CmenB vaccine group and 77·1 per 100 person-years (122 events in 270 participants) in the no vaccine group (aHR 0·78 [95% CI 0·60-1·01]; p=0·061). There were no deaths during the study. One drug-related serious adverse event (fixed-drug eruption) occurred in the doxycycline PEP group. Six (2%) participants in the doxycycline group discontinued doxycycline PEP because of gastrointestinal adverse events.

INTERPRETATION

Doxycycline PEP strongly reduced the incidence of chlamydia and syphilis in MSM, but we did not show efficacy of the 4CmenB vaccine for gonorrhoea. Doxycycline PEP should be assessed in other populations, such as heterosexual men and women, and its effect on antimicrobial resistance carefully monitored.

FUNDING

ANRS Maladies Infectieuses Emergentes.

TRANSLATION

For the French translation of the abstract see Supplementary Materials section.

Type 5 secretion system antigens as vaccines against Gram-negative bacterial infections

Infections caused by Gram-negative bacteria are leading causes of mortality worldwide. Due to the rise in antibiotic resistant strains, there is a desperate need for alternative strategies to control infections caused by these organisms. One such approach is the prevention of infection through vaccination. While live attenuated and heat-killed bacterial vaccines are effective, they can lead to adverse reactions. Newer vaccine technologies focus on utilizing polysaccharide or protein subunits for safer and more targeted vaccination approaches. One promising avenue in this regard is the use of proteins released by the Type 5 secretion system (T5SS). This system is the most prevalent secretion system in Gram-negative bacteria. These proteins are compelling vaccine candidates due to their demonstrated protective role in current licensed vaccines. Notably, Pertactin, FHA, and NadA are integral components of licensed vaccines designed to prevent infections caused by Bordetella pertussis or Neisseria meningitidis. In this review, we delve into the significance of incorporating T5SS proteins into licensed vaccines, their contributions to virulence, conserved structural motifs, and the protective immune responses elicited by these proteins.

Use of a meningococcal group B vaccine (4CMenB) in populations at high risk of gonorrhoea in the UK

The meningococcal group B vaccine, 4CMenB, is a broad-spectrum, recombinant protein vaccine that is licensed for protection against meningococcal group B disease in children and adults. Over the past decade, several observational studies supported by laboratory studies have reported protection by 4CMenB against gonorrhoea, a sexually transmitted infection caused by Neisseria gonorrhoeae. Gonorrhoea is a major global public health problem, with rising numbers of diagnoses and increasing resistance to multiple antibiotics. In England, more than 82 000 cases of gonorrhoea were diagnosed in 2022, with nearly half of the cases diagnosed among gay, bisexual, and other men who have sex with men. There are currently no licensed vaccines against gonorrhoea but 4CMenB is estimated to provide 33-47% protection against gonorrhoea. On Nov 10, 2023, the UK Joint Scientific Committee on Vaccination and Immunisation agreed that a targeted programme should be initiated using 4CMenB to prevent gonorrhoea among individuals at higher risk of infection attending sexual health services in the UK. This decision was made after reviewing evidence from retrospective and prospective observational studies, laboratory and clinical data, national surveillance reports, and health economic analyses. In this Review, we summarise the epidemiology of invasive meningococcal disease and gonorrhoea in England, the evidence supporting the use of 4CMenB for protection against gonorrhoea, and the data needed to inform long-term programme planning and extension to the wider population.

Profiling IgG and IgA antibody responses during vaccination and infection in a high-risk gonorrhoea population

Development of a vaccine against gonorrhoea is a global priority, driven by the rise in antibiotic resistance. Although Neisseria gonorrhoeae (Ng) infection does not induce substantial protective immunity, highly exposed individuals may develop immunity against re-infection with the same strain. Retrospective epidemiological studies have shown that vaccines containing Neisseria meningitidis (Nm) outer membrane vesicles (OMVs) provide a degree of cross-protection against Ng infection. We conducted a clinical trial (NCT04297436) of 4CMenB (Bexsero, GSK), a licensed Nm vaccine containing OMVs and recombinant antigens, comprising a single arm, open label study of two doses with 50 adults in coastal Kenya who have high exposure to Ng. Data from a Ng antigen microarray established that serum IgG and IgA reactivities against the gonococcal homologs of the recombinant antigens in the vaccine peaked at 10 but had declined by 24 weeks. For most reactive OMV-derived antigens, the reverse was the case. A cohort of similar individuals with laboratory-confirmed gonococcal infection were compared before, during, and after infection: their reactivities were weaker and differed from the vaccinated cohort. We conclude that the cross-protection of the 4CMenB vaccine against gonorrhoea could be explained by cross-reaction against a diverse selection of antigens derived from the OMV component.

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.

Covalent coupling of functionalized outer membrane vesicles (OMVs) to gold nanoparticles

Outer membrane vesicle-functionalized nanoparticles (OMV-NPs) have attracted significant interest, especially regarding drug delivery applications and vaccines. Here, we report on novel OMV-NPs by applying bioorthogonal click reaction for encapsulating gold nanoparticles (NPs) within outer membrane vesicles (OMVs) by covalent coupling. For this purpose, outer membrane protein A (OmpA), abundant in large numbers (due to 100,000 copies/cell [1]) in OMVs, was modified via the incorporation of the unnatural amino acid p-azidophenylalanine. The azide group was covalently coupled to alkyne-functionalized NPs after incorporation into OmpA. A simplified procedure using low-speed centrifugation (1,000 x g) was developed for preparing OMV-NPs. The OMV-NPs were characterized by zeta potential, Laurdan-based lipid membrane dynamics studies, and the enzymatic activity of functionalized OMVs with surface-displayed nicotinamide adenine dinucleotide oxidase (Nox). In addition, OMVs from attenuated bacteria (ClearColiTM BL21(DE3), E. coli F470) with surface-displayed Nox or antibody fragments were prepared and successfully coupled to AuNPs. Finally, OMV-NPs displaying single-chain variable fragments from a monoclonal antibody directed against epidermal growth factor receptor were applied to demonstrate the feasibility of OMV-NPs for tumor cell targeting.

A Qualitative Concept Elicitation Study to Understand Patient-Reported Symptoms and Impacts of Neisseria gonorrhoeae Infections in the United States

BACKGROUND

Gonorrhea is the second most common bacterial sexually transmitted infection in the United States, with rising rates. Emerging antimicrobial resistance threatens public health, and vaccines are in development. This study documents patient-reported gonorrhea symptoms and health-related quality-of-life (HRQoL) impact in women who have sex with men (WSM), men who have sex with women (MSW), and men who have sex with men (MSM).

METHODS

Semistructured qualitative interviews were conducted (April 2021-March 2022) among US adults with recent (≤6 months) confirmed gonorrhea. Concept saturation was achieved, confirming adequate participant numbers to meet objectives. Elicited symptom and HRQoL impacts were used to develop a conceptual disease model. Common patient-reported outcome measure (PROM) items were compared with elicited concepts.

RESULTS

Thirty-two participants (15 WSM, 8 MSW, and 9 MSM) were included. Eight were asymptomatic, 6 had repeat infections, and 5 women and 4 men had complications (i.e., infertility or pelvic inflammatory disease, and urethritis, respectively).The most frequently reported symptoms were vaginal discharge (n = 11 of 12), dysuria (n = 10 of 12), and abdominal/vaginal pain (n = 9 of 12) for symptomatic WSM; dysuria (n = 5 of 6) and penile discharge (n = 4 of 6) for symptomatic MSW; and throat, testicular, or rectal pain (n = 4 of 6) for symptomatic MSM. All (symptomatic and asymptomatic) participants reported HRQoL impacts including negative emotional experiences (n = 31 of 32), and interference with sexual activity (n = 30 of 32), relationships (n = 24 of 32), and social life (n = 17 of 32). Concepts were poorly represented in existing PROMs.

CONCLUSIONS

Participants reported a diverse range of symptoms and HRQoL impacts, to help inform the value of new treatment and prevention options. More research is needed to quantify patient burden and develop PROMs.

Sweet complexity: O-linked protein glycosylation in pathogenic Neisseria

The genus Neisseria, which colonizes mucosal surfaces, includes both commensal and pathogenic species that are exclusive to humans. The two pathogenic Neisseria species are closely related but cause quite different diseases, meningococcal sepsis and meningitis (Neisseria meningitidis) and sexually transmitted gonorrhea (Neisseria gonorrhoeae). Although obvious differences in bacterial niches and mechanisms for transmission exists, pathogenic Neisseria have high levels of conservation at the levels of nucleotide sequences, gene content and synteny. Species of Neisseria express broad-spectrum O-linked protein glycosylation where the glycoproteins are largely transmembrane proteins or lipoproteins localized on the cell surface or in the periplasm. There are diverse functions among the identified glycoproteins, for example type IV biogenesis proteins, proteins involved in antimicrobial resistance, as well as surface proteins that have been suggested as vaccine candidates. The most abundant glycoprotein, PilE, is the major subunit of pili which are an important colonization factor. The glycans attached can vary extensively due to phase variation of protein glycosylation (pgl) genes and polymorphic pgl gene content. The exact roles of glycosylation in Neisseria remains to be determined, but increasing evidence suggests that glycan variability can be a strategy to evade the human immune system. In addition, pathogenic and commensal Neisseria appear to have significant glycosylation differences. Here, the current knowledge and implications of protein glycosylation genes, glycan diversity, glycoproteins and immunogenicity in pathogenic Neisseria are summarized and discussed.

Microorganism-derived extracellular vesicles: emerging contributors to female reproductive health

Extracellular vesicles (EVs) are cell-derived nanoparticles that carry small molecules, nucleic acids, and proteins long distances in the body facilitating cell-cell communication. Microorganism-derived EVs mediate communication between parent cells and host cells, with recent evidence supporting their role in biofilm formation, horizontal gene transfer, and suppression of the host immune system. As lipid-bound bacterial byproducts, EVs demonstrate improved cellular uptake and distribution in vivo compared to cell-free nucleic acids, proteins, or small molecules, allowing these biological nanoparticles to recapitulate the effects of parent cells and contribute to a range of human health outcomes. Here, we focus on how EVs derived from vaginal microorganisms contribute to gynecologic and obstetric outcomes. As the composition of the vaginal microbiome significantly impacts women's health, we discuss bacterial EVs from both healthy and dysbiotic vaginal microbiota. We also examine recent work done to evaluate the role of EVs from common vaginal bacterial, fungal, and parasitic pathogens in pathogenesis of female reproductive tract disease. We highlight evidence for the role of EVs in women's health, gaps in current knowledge, and opportunities for future work. Finally, we discuss how leveraging the innate interactions between microorganisms and mammalian cells may establish EVs as a novel therapeutic modality for gynecologic and obstetric indications.

Gonococcal PorB: a multifaceted modulator of host immune responses

Neisseria gonorrhoeae is a human-specific pathogen responsible for the sexually transmitted infection, gonorrhoea. N. gonorrhoeae promotes its survival by manipulating both innate and adaptive immune responses. The most abundant gonococcal outer-membrane protein is PorB, an essential porin that facilitates ion exchange. Importantly, gonococcal PorB has several immunomodulatory properties. To subvert the innate immune response, PorB suppresses killing mechanisms of macrophages and neutrophils, and recruits negative regulators of complement to the gonococcal cell surface. For manipulation of adaptive immune responses, gonococcal PorB suppresses the capability of dendritic cells to stimulate proliferation of T cells. As gonococcal PorB is highly abundant in outer-membrane vesicles, consideration of the immunomodulatory properties of this porin is critical when designing gonococcal vaccines.

Neisseria gonorrhoeae vaccines: a contemporary overview

Neisseria gonorrhoeae infection is an important public health issue, with an annual global incidence of 87 million. N. gonorrhoeae infection causes significant morbidity and can have serious long-term impacts on reproductive and neonatal health and may rarely cause life-threatening disease. Global rates of N. gonorrhoeae infection have increased over the past 20 years. Importantly, rates of antimicrobial resistance to key antimicrobials also continue to increase, with the United States Centers for Disease Control and Prevention identifying drug-resistant N. gonorrhoeae as an urgent threat to public health. This review summarizes the current evidence for N. gonorrhoeae vaccines, including historical clinical trials, key N. gonorrhoeae vaccine preclinical studies, and studies of the impact of Neisseria meningitidis vaccines on N. gonorrhoeae infection. A comprehensive survey of potential vaccine antigens, including those identified through traditional vaccine immunogenicity approaches, as well as those identified using more contemporary reverse vaccinology approaches, are also described. Finally, the potential epidemiological impacts of a N. gonorrhoeae vaccine and research priorities for further vaccine development are described.

On The Horizon: Novel Approaches to Sexually Transmitted Infection Prevention

Rates of sexually transmitted infections (STIs), especially cases of infectious and congenital syphilis, are increasing in the United States. Novel strategies for STI prevention are being explored and include doxycycline post-exposure prophylaxis and the potential utility of vaccines against gonorrhea. Self-collection of samples and point of care testing for STI are increasingly being employed in a variety of settings. Both can improve uptake of screening and lead to earlier detection and treatment of incident STI in target populations. Overcoming existing regulatory issues and optimizing implementation of current evidence-based strategies will be key to maximizing future STI prevention efforts. Here we provide an update for primary care providers on selected new strategies for STI prevention either currently available or under development for possible future use.

Outer membrane vesicles as a platform for the discovery of antibodies to bacterial pathogens

Bacterial outer membrane vesicles (OMVs) are nanosized spheroidal particles shed by gram-negative bacteria that contain biomolecules derived from the periplasmic space, the bacterial outer membrane, and possibly other compartments. OMVs can be purified from bacterial culture supernatants, and by genetically manipulating the bacterial cells that produce them, they can be engineered to harbor cargoes and/or display molecules of interest on their surfaces including antigens that are immunogenic in mammals. Since OMV bilayer-embedded components presumably maintain their native structures, OMVs may represent highly useful tools for generating antibodies to bacterial outer membrane targets. OMVs have historically been utilized as vaccines or vaccine constituents. Antibodies that target bacterial surfaces are increasingly being explored as antimicrobial agents either in unmodified form or as targeting moieties for bactericidal compounds. Here, we review the properties of OMVs, their use as immunogens, and their ability to elicit antibody responses against bacterial antigens. We highlight antigens from bacterial pathogens that have been successfully targeted using antibodies derived from OMV-based immunization and describe opportunities and limitations for OMVs as a platform for antimicrobial antibody development. KEY POINTS: • Outer membrane vesicles (OMVs) of gram-negative bacteria bear cell-surface molecules • OMV immunization allows rapid antibody (Ab) isolation to bacterial membrane targets • Review and analysis of OMV-based immunogens for antimicrobial Ab development.

Neisseria gonorrhoeae lipooligosaccharide glycan epitopes recognized by bactericidal IgG antibodies elicited by the meningococcal group B-directed vaccine, MenB-4C

Introduction

Outer membrane vesicles (OMVs) of Neisseria meningitidis in the group B-directed vaccine MenB-4C (BexseroR) protect against infections with Neisseria gonorrhoeae. The immunological basis for protection remains unclear. N. meningitidis OMV vaccines generate human antibodies to N. meningitidis and N. gonorrhoeae lipooligosaccharide (LOS/endotoxin), but the structural specificity of these LOS antibodies is not defined.

Methods

Ten paired human sera obtained pre- and post-MenB-4C immunization were used in Western blots to probe N. meningitidis and N. gonorrhoeae LOS. Post-MenB-4C sera (7v5, 19v5, and 17v5), representing individual human variability in LOS recognition, were then used to interrogate structurally defined LOSs of N. meningitidis and N. gonorrhoeae strains and mutants and studied in bactericidal assays.

Results and discussion

Post-MenB-4C sera recognized both N. meningitidis and N. gonorrhoeae LOS species, ~10% of total IgG to gonococcal OMV antigens. N. meningitidis and N. gonorrhoeae LOSs were broadly recognized by post-IgG antibodies, but with individual variability for LOS structures. Deep truncation of LOS, specifically a rfaK mutant without α-, β-, or γ-chain glycosylation, eliminated LOS recognition by all post-vaccine sera. Serum 7v5 IgG antibodies recognized the unsialyated L1 α-chain, and a 3-PEA-HepII or 6-PEA-HepII was part of the conformational epitope. Replacing the 3-PEA on HepII with a 3-Glc blocked 7v5 IgG antibody recognition of N. meningitidis and N. gonorrhoeae LOSs. Serum 19v5 recognized lactoneotetrose (LNT) or L1 LOS-expressing N. meningitidis or N. gonorrhoeae with a minimal α-chain structure of Gal-Glc-HepI (L8), a 3-PEA-HepII or 6-PEA-HepII was again part of the conformational epitope and a 3-Glc-HepII blocked 19v5 antibody binding. Serum 17v5 LOS antibodies recognized LNT or L1 α-chains with a minimal HepI structure of three sugars and no requirement for HepII modifications. These LOS antibodies contributed to the serum bactericidal activity against N. gonorrhoeae. The MenB-4C vaccination elicits bactericidal IgG antibodies to N. gonorrhoeae conformational epitopes involving HepI and HepII glycosylated LOS structures shared between N. meningitidis and N. gonorrhoeae. LOS structures should be considered in next-generation gonococcal vaccine design.

Bacteria-derived extracellular vesicles: endogenous roles, therapeutic potentials and their biomimetics for the treatment and prevention of sepsis

Sepsis is one of the medical conditions with a high mortality rate and lacks specific treatment despite several years of extensive research. Bacterial extracellular vesicles (bEVs) are emerging as a focal target in the pathophysiology and treatment of sepsis. Extracellular vesicles (EVs) derived from pathogenic microorganisms carry pathogenic factors such as carbohydrates, proteins, lipids, nucleic acids, and virulence factors and are regarded as "long-range weapons" to trigger an inflammatory response. In particular, the small size of bEVs can cross the blood-brain and placental barriers that are difficult for pathogens to cross, deliver pathogenic agents to host cells, activate the host immune system, and possibly accelerate the bacterial infection process and subsequent sepsis. Over the years, research into host-derived EVs has increased, leading to breakthroughs in cancer and sepsis treatments. However, related approaches to the role and use of bacterial-derived EVs are still rare in the treatment of sepsis. Herein, this review looked at the dual nature of bEVs in sepsis by highlighting their inherent functions and emphasizing their therapeutic characteristics and potential. Various biomimetics of bEVs for the treatment and prevention of sepsis have also been reviewed. Finally, the latest progress and various obstacles in the clinical application of bEVs have been highlighted.

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.

Experimental Urethral Infection with Neisseria gonorrhoeae

Gonorrhea rates and antibiotic resistance are both increasing. Neisseria gonorrhoeae (Ng) is an exclusively human pathogen and is exquisitely adapted to its natural host. Ng can subvert immune responses and undergoes frequent antigenic variation, resulting in limited immunity and protection from reinfection. Previous gonococcal vaccine efforts have been largely unsuccessful, and the last vaccine to be tested in humans was more than 35 years ago. Advancing technologies and the threat of untreatable gonorrhea have fueled renewed pursuit of a vaccine as a long-term sustainable solution for gonorrhea control. Despite the development of a female mouse model of genital gonococcal infection two decades ago, correlates of immunity or protection remain largely unknown, making the gonococcus a challenging vaccine target. The controlled human urethral infection model of gonorrhea (Ng CHIM) has been used to study gonococcal pathogenesis and the basis of anti-gonococcal immunity. Over 200 participants have been inoculated without serious adverse events. The Ng CHIM replicates the early natural course of urethral infection. We are now at an inflexion point to pivot the use of the model for vaccine testing to address the urgency of improved gonorrhea control. Herein we discuss the need for gonorrhea vaccines, and the advantages and limitations of the Ng CHIM in accelerating the development of gonorrhea vaccines.

Preclinical efficacy of a cell division protein candidate gonococcal vaccine identified by artificial intelligence

IMPORTANCE

Vaccines to curb the global spread of multidrug-resistant gonorrhea are urgently needed. Here, 26 vaccine candidates identified by an artificial intelligence-driven platform (Efficacy Discriminative Educated Network[EDEN]) were screened for efficacy in the mouse vaginal colonization model. Complement-dependent bactericidal activity of antisera and the EDEN protective scores both correlated positively with the reduction in overall bacterial colonization burden. NGO1549 (FtsN) and NGO0265, both involved in cell division, displayed the best activity and were selected for further development. Both antigens, when fused to create a chimeric protein, elicited bactericidal antibodies against a wide array of gonococcal isolates and significantly attenuated the duration and burden of gonococcal colonization of mouse vaginas. Protection was abrogated in mice that lacked complement C9, the last step in the formation of the membrane attack complex pore, suggesting complement-dependent bactericidal activity as a mechanistic correlate of protection of the vaccine. FtsN and NGO0265 represent promising vaccine candidates against gonorrhea.

Evaluating vaccine-elicited antibody activities against Neisseria gonorrhoeae: cross-protective responses elicited by the 4CMenB meningococcal vaccine

The bacterial pathogen Neisseria gonorrhoeae is an urgent global health problem due to increasing numbers of infections, coupled with rampant antibiotic resistance. Vaccines against gonorrhea are being prioritized to combat drug-resistant N. gonorrhoeae. Meningococcal serogroup B vaccines such as four-component meningococcal B vaccine (4CMenB) are predicted by epidemiology studies to cross-protect individuals from natural infection with N. gonorrhoeae and elicit antibodies that cross-react with N. gonorrhoeae. Evaluation of vaccine candidates for gonorrhea requires a suite of assays for predicting efficacy in vitro and in animal models of infection, including the role of antibodies elicited by immunization. Here, we present the development and optimization of assays to evaluate antibody functionality after immunization of mice: antibody binding to intact N. gonorrhoeae, serum bactericidal activity, and opsonophagocytic killing activity using primary human neutrophils [polymorphonuclear leukocytes (PMNs)]. These assays were developed with purified antibodies against N. gonorrhoeae and used to evaluate serum from mice that were vaccinated with 4CMenB or given alum as a negative control. Results from these assays will help prioritize gonorrhea vaccine candidates for advanced preclinical to early clinical studies and will contribute to identifying correlates and mechanisms of immune protection against N. gonorrhoeae.

Recent advances in various bio-applications of bacteria-derived outer membrane vesicles

Outer membrane vesicles (OMVs) are spherical nanoparticles released from gram-negative bacteria. OMVs were originally classified into native 'nOMVs' (produced naturally from budding of bacteria) and non-native (produced by mechanical means). nOMVs and detergent (dOMVs) are isolated from cell supernatant without any detergent cell disruption techniques and through detergent extraction, respectively. Growth stages and conditions e.g. different stress factors, including temperature, nutrition deficiency, and exposure to hazardous chemical agents can affect the yield of OMVs production and OMVs content. Because of the presence of bacterial antigens, pathogen-associated molecular patterns (PAMPs), various proteins and the vesicle structure, OMVs have been developed in many biomedical applications. OMVs due to their size can be phagocytized by APCs, enter lymph vessels, transport antigens efficiently, and induce both T and B cells immune responses. Non-engineered OMVs have been frequently used as vaccines against different bacterial and viral infections, and various cancers. OMVs can also be used in combination with different antigens as an attractive vaccine adjuvant. Indeed, foreign antigens from target microorganisms can be trapped in the lumen of nonpathogenic vesicles or can be displayed on the surface through bacterial membrane protein to increase the immunogenicity of the antigens. In this review, different factors affecting OMV production including time of cultivation, growth media, stress conditions and genetic manipulations to enhance vesiculation will be described. Furthermore, recent advances in various biological applications of OMVs such as vaccine, drug delivery, cancer therapy, and enzyme carrier are discussed. Generally, the application of OMVs as vaccine carrier in three categories (i.e., non-engineered OMVs, OMVs as an adjuvant, recombinant OMVs (rOMVs)), as delivery system for small interfering RNA and therapeutic agents, and as enzymes carrier will be discussed.

Bacterial growth stage determines the yields, protein composition, and periodontal pathogenicity of Porphyromonas gingivalis outer membrane vesicles

Introduction

P. gingivalis (W83), as the keystone pathogen in chronic periodontitis, has been found to be tightly bound to systemic diseases. Outer membrane vesicles (OMVs) produced by P. gingivalis (W83) are thought to serve key functions in bacterial virulence and pathogenicity. This study aims to comprehend the biological functions of P. gingivalis OMVs isolated from different growth stages by comparing their physicochemical properties and pathogenicity.

Methods

Protein composition was analyzed via isotope-labeled relative and absolute quantification (iTRAQ). Macrophage polarization and the expression of IL-6 and IL-1β were detected. The proliferation, migration, osteogenic differentiation, and IL-1b/NLRP3 expression of periodontal ligament stem cells (PDLSCs) were evaluated. P. gingivalis/P. gingivalis OMVs-induced periodontal models were also constructed in Sprague Dawley rats.

Results

The protein composition of P. gingivalis OMVs isolated from different growth stages demonstrated obvious differences ranging from 25 KDa to 75 KDa. In the results of flow cytometry, we found that in vitro experiments the M1 subtype of macrophages was more abundant in the late-log OMVs and stationary OMVs groups which boosted the production of inflammatory cytokines more than pre-log OMVs. Compared to pre-log OMVs, late-log OMVs and stationary OMVs had more pronounced inhibitory effects on proliferation, migration, and early osteogenesis of PDLSCs. The NLRP3 inflammasome was activated to a larger extent in the stationary OMVs group. Micro-computed tomography (Micro CT), hematoxylin-eosin staining (HE), and tartrate acid phosphatase (TRAP) results showed that the periodontal damage in the stationary OMVs group was worse than that in the pre-log OMVs and late-log OMVs group, but almost equal to that in the positive control group (P. gingivalis).

Discussion

In general, both in vivo and in vitro experiments showed that late-log OMVs and stationary OMVs have more significant pathogenicity in periodontal disease.

Comparison of lipooligosaccharides from human challenge strains of Neisseria gonorrhoeae

The alarming rise of antibiotic resistance and the emergence of new vaccine technologies have increased the focus on vaccination to control gonorrhea. Neisseria gonorrhoeae strains FA1090 and MS11 have been used in challenge studies in human males. We used negative-ion MALDI-TOF MS to profile intact lipooligosaccharide (LOS) from strains MS11mkA, MS11mkC, FA1090 A23a, and FA1090 1-81-S2. The MS11mkC and 1-81-S2 variants were isolated from male volunteers infected with MS11mkA and A23a, respectively. LOS profiles were obtained after purification using the classical phenol water extraction method and by microwave-enhanced enzymatic digestion, which is more amenable for small-scale work. Despite detecting some differences in the LOS profiles, the same major species were observed, indicating that microwave-enhanced enzymatic digestion is appropriate for MS studies. The compositions determined for MS11mkA and mkC LOS were consistent with previous reports. FA1090 is strongly recognized by mAb 2C7, an antibody-binding LOS with both α- and β-chains if the latter is a lactosyl group. The spectra of the A23a and 1-81-S2 FA1090 LOS were similar to each other and consistent with the expression of α-chain lacto-N-neotetraose and β-chain lactosyl moieties that can both be acceptor sites for sialic acid substitution. 1-81-S2 LOS was analyzed after culture with and without media supplemented with cytidine-5'-monophosphate N-acetylneuraminic acid (CMP-Neu5Ac), which N. gonorrhoeae needs to sialylate its LOS. LOS sialylation reduces the infectivity of gonococci in men, although it induces serum resistance in serum-sensitive strains and reduces killing by neutrophils and antimicrobial peptides. The infectivity of FA1090 in men is much lower than that of MS11mkC, but the reason for this difference is unclear. Interestingly, some peaks in the spectra of 1-81-S2 LOS after bacterial culture with CMP-Neu5Ac were consistent with disialylation of the LOS, which could be relevant to the reduced infectivity of FA1090 in men and could have implications regarding the phase variation of the LOS and the natural history of infection.

Evaluating vaccine-elicited antibody activities against Neisseria gonorrhoeae: cross-protective responses elicited by the 4CMenB meningococcal vaccine

The bacterial pathogen Neisseria gonorrhoeae is an urgent global health problem due to increasing numbers of infections, coupled with rampant antibiotic resistance. Vaccines against gonorrhea are being prioritized to combat drug-resistant N. gonorrhoeae. Meningococcal serogroup B vaccines such as 4CMenB are predicted by epidemiology studies to cross-protect individuals from natural infection with N. gonorrhoeae and elicit antibodies that cross-react with N. gonorrhoeae. Evaluation of vaccine candidates for gonorrhea requires a suite of assays for predicting efficacy in vitro and in animal models of infection, including the role of antibodies elicited by immunization. Here we present assays to evaluate antibody functionality after immunization: antibody binding to intact N. gonorrhoeae, serum bactericidal activity, and opsonophagocytic killing activity using primary human neutrophils (polymorphonuclear leukocytes). These assays were developed with purified antibodies against N. gonorrhoeae and used to evaluate serum from mice that were vaccinated with 4CMenB or given alum as a negative control. Results from these assays will help prioritize gonorrhea vaccine candidates for advanced preclinical to early clinical study and will contribute to identifying correlates and mechanisms of immune protection against N. gonorrhoeae .

Neisseria gonorrhoeae MtrCDE Efflux Pump During In Vivo Experimental Genital Tract Infection in Men and Mice Reveals the Presence of Within-Host Colonization Bottleneck

The MtrCDE efflux pump of Neisseria gonorrhoeae exports a wide range of antimicrobial compounds that the gonococcus encounters at mucosal surfaces during colonization and infection. Here, we evaluate the role of this efflux pump system in strain FA1090 in human male urethral infection with a Controlled Human Infection Model. Using the strategy of competitive multi-strain infection with wild-type FA1090 and an isogenic mutant strain that does not contain a functional MtrCDE pump, we found that the presence of the efflux pump during human experimental infection did not confer a competitive advantage. This finding is in contrast to previous findings in female mice, which demonstrated that gonococci of strain FA19 lacking a functional MtrCDE pump had a significantly reduced fitness compared to the wild type strain in the lower genital tract of female mice. We conducted competitive infections in female mice with FA19 and FA1090 strains, including mutants that do not assemble a functional Mtr efflux pump, demonstrating the fitness advantage provided byt the MtrCDE efflux pump during infection of mice is strain dependent. Our data indicate that new gonorrhea treatment strategies targeting the MtrCDE efflux pump functions may not be universally efficacious in naturally occurring infections. Owing to the equal fitness of FA1090 strains in men, our experiments unexpectedly demonstrated the likely presence of an early colonization bottleneck of N. gonorrhoeae in the human male urethra.

TRIAL REGISTRATION

Clinicaltrials.gov NCT03840811 .

Increasing human monoclonal antibody cloning efficiency with a whole-cell modified immunoglobulin-capture assay (mICA)

Expression cloning of fully human monoclonal antibodies (hmAbs) is seeing powerful utility in the field of vaccinology, especially for elucidating vaccine-induced B-cell responses and novel vaccine candidate antigen discovery. Precision of the hmAb cloning process relies on efficient isolation of hmAb-producing plasmablasts of interest. Previously, a novel immunoglobulin-capture assay (ICA) was developed, using single protein vaccine antigens, to enhance the pathogen-specific hmAb cloning output. Here, we report a novel modification of this single-antigen ICA using formalin-treated, fluorescently stained whole cell suspensions of the human bacterial invasive pathogens, Streptococcus pneumoniae and Neisseria meningitidis. Sequestration of IgG secreted by individual vaccine antigen-specific plasmablasts was achieved by the formation of an anti-CD45-streptavidin and biotin anti-IgG scaffold. Suspensions containing heterologous pneumococcal and meningococcal strains were then used to enrich for polysaccharide- and protein antigen-specific plasmablasts, respectively, during single cell sorting. Following application of the modified whole-cell ICA (mICA), ~61% (19/31) of anti-pneumococcal polysaccharide hmAbs were cloned compared to 14% (8/59) obtained using standard (non-mICA) methods - representing a ~4.4-fold increase in hmAb cloning precision. A more modest ~1.7-fold difference was obtained for anti-meningococcal vaccine hmAb cloning; ~88% of hmAbs cloned via mICA versus ~53% cloned via the standard method were specific for a meningococcal surface protein. VDJ sequencing revealed that cloned hmAbs reflected an anamnestic response to both pneumococcal and meningococcal vaccines; diversification within hmAb clones occurred by positive selection for replacement mutations. Thus, we have shown successful utilization of whole bacterial cells in the ICA protocol enabling isolation of hmAbs targeting multiple disparate epitopes, thereby increasing the power of approaches such as reverse vaccinology 2.0 (RV 2.0) for bacterial vaccine antigen discovery.

Healthy Vaccinee Bias and MenB-FHbp Vaccine Effectiveness Against Gonorrhea

ABSTRACT

Observational studies demonstrated 30% to 40% effectiveness of outer-membrane vesicle (OMV) meningococcal serogroup B vaccines against gonorrhea. To explore whether healthy vaccinee bias influenced such findings, we examined the effectiveness of MenB-FHbp, a non-OMV vaccine that is not protective against gonorrhea. MenB-FHbp was ineffective against gonorrhea. Healthy vaccinee bias likely did not confound earlier studies of OMV vaccines.

Meningococcus B Vaccination Effectiveness Against Neisseria gonorrhoeae Infection in People Living With HIV: A Case-Control Study

BACKGROUND

We assessed the vaccination effectiveness (VE) of multicomponent meningococcal serogroup B (4CMenB) vaccine against gonorrhea among people living with HIV (PLWH) with a previous diagnosis of sexually transmitted infection.

METHODS

Unmatched case-control study on men who have sex with men living with HIV, in care at San Raffaele Scientific Institute, Milan, Italy, with gonorrhea, syphilis, chlamydia, or anal human papillomavirus between July 2016 (beginning of 4CMenB vaccination) and February 2021 (date of freezing). For the analysis, cases were people with ≥1 gonorrhea infection since July 2016, and controls were people with ≥1 syphilis, chlamydia, or anal human papillomavirus infection since July 2016. Logistic regression was used to provide the estimate of 4CMenB VE against gonorrhea.

RESULTS

Included people living with HIV were 1051 (103 cases, 948 controls); 349 of 1051 (33%) received 2 doses of 4CMenB vaccination. The median follow-up was 3.8 years (2.1-4.3 years). The unadjusted estimate for VE against gonorrhea was 42% (95% confidence interval, 6%-64%; P = 0.027). Logistic regression showed that VE against gonorrhea remained significant (44%; 95% confidence interval, 9%-65%; P = 0.020) after adjusting for some factors that might have a potential influence on VE or those with significant unbalanced distributions between cases and controls at univariable analysis.

CONCLUSIONS

4CMenB vaccination is associated with a lower risk of gonorrhea in the setting of men who have sex with men living with HIV with a previous sexually transmitted infection.

OpcA and PorB are novel bactericidal antigens of the 4CMenB vaccine in mice and humans

The ability of Neisseria meningitidis Outer Membrane Vesicles (OMV) to induce protective responses in humans is well established and mainly attributed to Porin A (PorA). However, the contribution of additional protein antigens to protection remains to be elucidated. In this study we dissected the immunogenicity of antigens originating from the OMV component of the 4CMenB vaccine in mice and humans. We collected functional data on a panel of strains for which bactericidal responses to 4CMenB in infants was attributable to the OMV component and evaluated the role of 30 OMV-specific protein antigens in cross-coverage. By using tailor-made protein microarrays, the immunosignature of OMV antigens was determined. Three of these proteins, OpcA, NspA, and PorB, triggered mouse antibodies that were bactericidal against several N. meningitidis strains. Finally, by genetic deletion and/or serum depletion studies, we demonstrated the ability of OpcA and PorB to induce functional immune responses in infant sera after vaccination. In conclusion, while confirming the role of PorA in eliciting protective immunity, we identified two OMV antigens playing a key role in protection of infants vaccinated with the 4CMenB vaccine against different N. meningitidis serogroup B strains.

Microencapsulated IL-12 Drives Genital Tract Immune Responses to Intranasal Gonococcal Outer Membrane Vesicle Vaccine and Induces Resistance to Vaginal Infection with Diverse Strains of Neisseria gonorrhoeae

An experimental gonococcal vaccine consisting of outer membrane vesicles (OMVs) and microsphere (ms)-encapsulated interleukin-12 (IL-12 ms) induces Th1-driven immunity, with circulating and genital antibodies to Neisseria gonorrhoeae, after intravaginal (i.vag.) administration in female mice, and generates resistance to vaginal challenge infection. Because i.vag. administration is inapplicable to males and may not be acceptable to women, we determined whether intranasal (i.n.) administration would generate protective immunity against N. gonorrhoeae. Female and male mice were immunized i.n. with gonococcal OMVs plus IL-12 ms or blank microspheres (blank ms). Responses to i.n. immunization were similar to those with i.vag. immunization, with serum IgG, salivary IgA, and vaginal IgG and IgA antigonococcal antibodies induced when OMVs were administered with IL-12 ms. Male mice responded with serum IgG and salivary IgA antibodies similarly to female mice. Gamma interferon (IFN-γ) production by CD4⁺ T cells from iliac lymph nodes was elevated after i.n. or i.vag. immunization with OMVs plus IL-12 ms. Female mice immunized with OMVs plus IL-12 ms by either route resisted challenge with N. gonorrhoeae to an equal extent, and resistance generated by i.n. immunization extended to heterologous strains of N. gonorrhoeae. Detergent-extracted OMVs, which have diminished lipooligosaccharide, generated protective immunity to challenge similar to native OMVs. OMVs from mutant N. gonorrhoeae, in which genes for Rmp and LpxL1 were deleted to eliminate the induction of blocking antibodies against Rmp and diminish lipooligosaccharide endotoxicity, also generated resistance to challenge infection similar to wild-type OMVs when administered i.n. with IL-12 ms. IMPORTANCE We previously demonstrated that female mice can be immunized intravaginally with gonococcal outer membrane vesicles (OMVs) plus microsphere (ms)-encapsulated interleukin-12 (IL-12 ms) to induce antigonococcal antibodies and resistance to genital tract challenge with live Neisseria gonorrhoeae. However, this route of vaccination may be impractical for human vaccine development and is inapplicable to males. Because intranasal immunization has previously been shown to induce antibody responses in both male and female genital tracts, we have evaluated this route of immunization with gonococcal OMVs plus IL-12 ms. In addition, we have refined the composition of gonococcal OMVs to reduce the endotoxicity of lipooligosaccharide and to eliminate the membrane protein Rmp, which induces countereffective blocking antibodies. The resulting vaccine may be more suitable for ultimate translation to human application against the sexually transmitted infection gonorrhea, which is becoming increasingly resistant to treatment with antibiotics.

Insight into Prevention of Neisseria Gonorrhoeae: A Short Review

Neisseria gonorrhoeae (gonococcus) and Neisseria meningitidis (meningococcus) are important global pathogens which cause the sexually transmitted diseases gonorrhea and meningitis, respectively, as well as sepsis. We prepared a review according to the preferred reporting items for systematic reviews and meta-analyses (PRISMA), with the aims of (a) evaluating the data on the MenB vaccination as protection against sexually transmitted infections by N. gonorrhoeae and (b) to briefly comment on the data of ongoing studies of new vaccines. We evaluated existing evidence on the effect of 4CMenB, a multi-component vaccine, on invasive diseases caused by different meningococcal serogroups and on gonorrhea. Non-B meningococcal serogroups showed that the 4CMenB vaccine could potentially offer some level of protection against non-B meningococcal serogroups and N. gonorrhoeae. The assessment of the potential protection conferred by 4CMenB is further challenged by the fact that further studies are still needed to fully understand natural immune responses against gonococcal infections. A further limitation could be the potential differences between the protection mechanisms against N. gonorrhoeae, which causes local infections, and the protection mechanisms against N. meningitidis, which causes systemic infections.

The early-life gut microbiome and vaccine efficacy

Vaccines are one of the greatest successes of public health, preventing millions of cases of disease and death in children each year. However, the efficacy of many vaccines can vary greatly between infants from geographically and socioeconomically distinct locations. Differences in the composition of the intestinal microbiome have emerged as one of the main factors that can account for variations in immunisation outcomes. In this Review, we assess the influence of the gut microbiota upon early life immunity, focusing on two important members of the microbiota with health-promoting and immunomodulatory properties: Bifidobacterium and Bacteroides. Additionally, we discuss their immune stimulatory microbial properties, interactions with the host, and their effect on vaccine responses and efficacy in infants. We also provide an overview of current microbiota-based approaches to enhance vaccine outcomes, and describe novel microbe-derived components that could lead to safer, more effective vaccines and vaccine adjuvants.

Infection With the US Neisseria meningitidis Urethritis Clade Does Not Lower Future Risk of Urethral Gonorrhea

BACKGROUND

Cross-protective immunity between Neisseria meningitidis (Nm) and Neisseria gonorrhoeae (Ng) may inform gonococcal vaccine development. Meningococcal serogroup B (MenB) outer membrane vesicle (OMV) vaccines confer modest protection against gonorrhea. However, whether urethral Nm infection protects against gonorrhea is unknown. We examined gonorrhea risk among men with US Nm urethritis clade (US_NmUC) infections.

METHODS

We conducted a retrospective cohort study of men with urethral US_NmUC (n = 128) between January 2015 and April 2018. Using diagnosis date as the baseline visit, we examined Ng status at return visits to compute urethral Ng risk. We compared these data to 3 referent populations: men with urethral Ng (n = 253), urethral chlamydia (Ct) (n = 251), and no urethral Ng or Ct (n = 255). We conducted sensitivity analyses to assess varied approaches to censoring, missing data, and anatomical site of infection. We also compared sequences of protein antigens in the OMV-based MenB-4C vaccine, US_NmUC, and Ng.

RESULTS

Participants were primarily Black (65%) and heterosexual (82%). Over follow-up, 91 men acquired urethral Ng. Men with urethral US_NmUC had similar Ng risk to men with prior urethral Ng (adjusted hazard ratio [aHR]: 1.27; 95% CI: .65-2.48). Men with urethral US_NmUC had nonsignificantly increased Ng risk compared with men with urethral Ct (aHR: 1.51; 95% CI: .79-2.88), and significantly increased Ng risk compared with men without urethral Ng or Ct (aHR: 3.55; 95% CI: 1.27-9.91). Most of the protein antigens analyzed shared high sequence similarity.

CONCLUSIONS

Urethral US_NmUC infection did not protect against gonorrhea despite substantial sequence similarities in shared protein antigens.

Application of a Neisseria meningitidis antigen microarray to identify candidate vaccine proteins from a human Phase I clinical trial

Meningococcal meningitis is a rare but serious condition affecting mainly children and young adults. Outer membrane vesicles (OMV) from Neisseria meningitidis have been used successfully as vaccines against the disease, although they only provide protection against a limited number of the many existing variants. There have been many attempts to identify suitable protein antigens for use in defined vaccines that provide broad protection against the disease, such as that leading to the development of the four component 4CMenB vaccine. We previously reported the use of a protein antigen microarray to screen for IgG antibodies in sera derived from human recipients of an OMV-based vaccine, as part of a Phase I clinical trial. Here, we show that computational methods can be used to cluster antigens that elicit similar responses in the same individuals. Fitting of IgG antibody binding data to 4,005 linear regressions identified pairs of antigens that exhibited significant correlations. Some were from the same antigens in different quaternary states, whilst others might be correlated for functional or immunological reasons. We also conducted statistical analyses to examine correlations between individual serum bactericidal antibody (SBA) titres and IgG reactivity against specific antigens. Both Kendall's tau and Spearman's rank correlation coefficient statistics identified specific antigens that correlated with log(SBA) titre in five different isolates. The principal antigens identified were PorA and PorB, RmpM, OpcA, and the type IV pilus assembly secretin, PilQ. Other minor antigens identified included a lipoprotein, two proteins from the BAM complex and the efflux channel MtrE. Our results suggest that consideration of the entire antigen composition, and allowance for potential interaction between antigens, could be valuable in designing future meningococcal vaccines. Such an approach has the advantages that it uses data derived from human, rather than animal, immunization and that it avoids the need to screen individual antigens.

Recent Progress Towards a Gonococcal Vaccine

Gonorrhea is a global health concern. Its etiological agent, Neisseria gonorrhoeae, rapidly acquires antimicrobial resistance and does not confer protective immunity as a consequence of infection. Attempts to generate an effective vaccine for gonorrhea have thus far been unsuccessful, as many structures on the bacterial envelope have the propensity to rapidly change, thus complicating recognition by the human immune system. In response to recent efforts from global health authorities to spur the efforts towards development of a vaccine, several new and promising steps have been made towards this goal, aided by advancements in computational epitope identification and prediction methods. Here, we provide a short review of recent progress towards a viable gonococcal vaccine, with a focus on antigen identification and characterization, and discuss a few of the tools that may be important in furthering these efforts.

Meningococcal Carriage in 'Men Having Sex With Men' With Pharyngeal Gonorrhoea

We assessed the characteristics of Neisseria meningitidis pharyngeal carriage in a cohort of ‘men having sex with men’, including patients with pharyngeal Neisseria gonorrhoeae infection. In the period 2017-2019, among all the oropharyngeal samples tested for gonorrhoea from MSM attending a STI Clinic in Bologna (Italy), we randomly selected 244 N. gonorrhoeae-positive samples and 403 negatives (n=647). Pharyngeal specimens were tested for N. meningitidis presence, by the detection of sodC gene. N. meningitidis-positive samples were further grouped by PCR tests for the major invasive genogroups (i.e., A, B, C, W, and Y). A molecular assay, targeting capsule transporter gene, was used to determine meningococcal capsular status. Overall, 75.8% (491/647) of samples tested positive for sodC gene, indicating a pharyngeal meningococcal carriage. Meningococcal colonisation was significantly more frequent in younger subjects (P=0.009), with no association with HIV infection. Non-groupable meningococci represented most of pharyngeal carriages (about 71%). The commonest N. meningitidis serogroup was B (23.6%), followed by C (2.1%), Y (1.8%) and W (1.1%). Meningococci were often characterized by the genetic potential of capsule production. Interestingly, a negative association between N. meningitidis and N. gonorrhoeae was found: pharyngeal gonorrhoea was significantly more present in patients without meningococcal carriage (P=0.03). Although preliminary, our data added knowledge on the epidemiology of meningococcal carriage in MSM communities at high risk of gonococcal infections, gaining new insights into the interactions/dynamics between N. meningitidis and N. gonorrhoeae.

Update on the Neisseria Macrophage Infectivity Potentiator-Like PPIase Protein

Neisseria pathogens express a Macrophage Infectivity Potentiator Protein (MIP), which belongs to the FK506 binding protein (FKBP) family of proteins that exhibit peptidyl-prolyl cis/trans isomerase (PPIase) activity. Neisseria MIP proteins are potential candidates for inclusion into vaccines for gonorrhoea caused by N. gonorrhoeae infection, and meningitis/sepsis caused by M. meningitidis infection. Neisseria MIP proteins are also potential targets for directed drug treatments, although this remains relatively unexplored. In this mini-review, we provide an update into the vaccine potential of Neisseria MIP and the few published drug targeting studies, and explore further the diversity of this protein amongst both pathogenic and commensal Neisseria spp.

Equity in vaccination policies to overcome social deprivation as a risk factor for invasive meningococcal disease

INTRODUCTION

Social deprivation is associated with poorer healthcare access. Vaccination is among the most effective public health interventions and achieving equity in vaccination access is vitally important. However, vaccines are often reimbursed by public funds only when recommended in national immunization programs (NIPs), which can increase inequity between high and low socioeconomic groups. Invasive meningococcal disease (IMD) is a serious vaccination-preventable disease. This review focuses on vaccination strategies against IMD designed to reduce inequity.

AREAS COVERED

We reviewed meningococcal epidemiology and current vaccination recommendations worldwide. We also reviewed studies demonstrating an association between social deprivation and risk of meningococcal disease, as well as studies demonstrating an impact of social deprivation on uptake of meningococcal vaccines. We discuss factors influencing inclusion of meningococcal vaccines in NIPs.

EXPERT OPINION

Incorporating meningococcal vaccines in NIPs is necessary to reduce inequity, but insufficient alone. Inclusion provides clear guidance to healthcare professionals and helps to ensure that vaccines are offered universally to all target groups. Beyond NIPs, cost of vaccination should be reimbursed especially for disadvantaged individuals. These approaches should help to achieve optimal protection against IMD, by increasing access and immunization rates, eventually reducing social inequities, and helping to protect those at greatest risk.

Looking beyond meningococcal B with the 4CMenB vaccine: the Neisseria effect

Infections with Neisseria meningitidis and Neisseria gonorrhoeae have different clinical manifestations, but the bacteria share up to 80-90% genome sequence identity. The recombinant meningococcal serogroup B (MenB) vaccine 4CMenB consists of four antigenic components that can be present in non-B meningococcal and gonococcal strains. This comprehensive review summarizes scientific evidence on the genotypic and phenotypic similarities between vaccine antigens and their homologs expressed by non-B meningococcal and gonococcal strains. It also includes immune responses of 4CMenB-vaccinated individuals and effectiveness and impact of 4CMenB against these strains. Varying degrees of strain coverage were estimated depending on the non-B meningococcal serogroup and antigenic repertoire. 4CMenB elicits immune responses against non-B meningococcal serogroups and N. gonorrhoeae. Real-world evidence showed risk reductions of 69% for meningococcal serogroup W clonal complex 11 disease and 40% for gonorrhea after 4CMenB immunization. In conclusion, functional antibody activity and real-world evidence indicate that 4CMenB has the potential to provide some protection beyond MenB disease.

Evolving strategies for meningococcal vaccination in Europe: Overview and key determinants for current and future considerations

Invasive meningococcal disease (IMD) is a life-threatening, unpredictable condition. Vaccines are available against 5 of the 6 meningococcal serogroups (Men) accounting for nearly all IMD cases worldwide; conjugate monovalent MenC, quadrivalent MenACWY, and protein-based MenB vaccines are commonly used. We provide a comprehensive overview of the evolution of meningococcal vaccination strategies employed in national immunization programmes (NIPs) and their impact on IMD incidence in Europe. A more in-depth description is given for several countries: the United Kingdom (UK), the Netherlands, Greece, Italy, and Ireland. We searched European health authorities' websites and PubMed. Various vaccines and immunization schedules are used in 21 NIPs. Most countries implement MenC vaccination in infants, MenACWY in adolescents, and a growing number, MenB in infants. Only Malta has introduced MenACWY vaccination in infants, and several countries reimburse immunization of toddlers. The UK, Italy, Ireland, Malta, Andorra, and San Marino recommend MenB vaccination in infants and MenACWY vaccination in adolescents, targeting the most prevalent serogroups in the most impacted age groups. Main factors determining new vaccination strategies are fluctuating IMD epidemiology, ease of vaccine implementation, ability to induce herd protection, favorable benefit-risk balance, and acceptable cost-effectiveness. Since 1999, when the UK introduced MenC vaccination, the reduction in IMD incidence has been gradually enhanced as other countries adopted routine meningococcal vaccinations. Meningococcal vaccination strategies in each country are continually adapted to regional epidemiology and national healthcare priorities. Future strategies may include broader coverage vaccines when available (e.g., MenABCWY, MenACWY), depending on prevailing epidemiology.