Efficacy of an experimental gonococcal lipooligosaccharide mimitope vaccine requires terminal complement

A safe and effective vaccine against multidrug-resistant gonorrhea is urgently needed. An experimental peptide vaccine called TMCP2 that mimics an oligosaccharide epitope in gonococcal lipooligosaccharide, when adjuvanted with glucopyranosyl lipid adjuvant-stable emulsion (GLA-SE), elicits bactericidal IgG and hastens clearance of gonococci in the mouse vaginal colonization model. Here, we show that efficacy of TMCP2 requires an intact terminal complement pathway, evidenced by loss of activity in C9 -/- mice or when C7 function was blocked. In conclusion, TMCP2 vaccine efficacy in the mouse vagina requires membrane attack complex. Serum bactericidal activity may serve as a correlate of protection for TMCP2.

Isolation and immunogenicity of extracted outer membrane vesicles from Pseudomonas aeruginosa under antibiotics treatment conditions

Background and Objectives: Different types of antibiotics have been indicated to enhance the secretion of OMVs from Pseudomonas aeruginosa. We aimed to investigate the effect of meropenem and amikacin antibiotics on inducing the secre- tion of OMVs and immunologic features in P. aeruginosa. Materials and Methods: The OMVs were prepared from P. aeruginosa under hypervesiculation condition (treatment with amikacin and meropenem), and extraction was carried out by the sequential ultracentrifugation. Physicochemical features of extracted OMVs were evaluated by electron microscopy and SDS-PAGE. To quantify antibody synthesis and function after immunization with OMV, we used ELISA, serum bactericidal activity, and opsonophagocytosis. Production of cytokines from splenocytes of immunized mice was measured with ELISA. Results: Specific-antibody IgG production, particularly IgG1 subclass, increased in mice primed with hypervesiculation-de- rived OMVs compared to normal condition-derived OMVs. Serum bactericidal activity and opsonophagocytosis of secreted antibody was enhanced in mice primed with hypervesiculation-derived OMVs. Investigation of cytokine production showed the upregulation of IL-8, IL-12, IL-17, and TNF-α and downregulation of IL-10. Conclusion: Based on our findings, OMVs production can be increased by treating P. aeruginosa with amikacin and mero- penem antibiotics. Moreover, hypervesiculation-derived OMV scan possibly activate the humoral and cellular immune re- sponse more than normal OMVs.

01. Serum Bactericidal Activity Against Circulating and Reference Strains of Meningococcal Serogroup B in the United States: A Review of Meningococcal Serogroup B (MenB) Vaccines in Adolescents and Young Adults

Background US adolescents and young adults are at particular risk of invasive meningococcal disease (IMD). In 2018, menincococcal serogroup B was responsible for 36% of IMD cases in the US overall and for 66% of cases in adolescents and young adults. This age group is at high risk of IMD during outbreaks, which result in significant response-related costs. MenB vaccine efficacy against IMD relies on its ability to provide broad protection against diverse disease-causing strains. MenB-FHbp (Trumenba) and MenB-4C (Bexsero) are MenB vaccines licensed in the US as 2-dose series with an interval of 6 mo or 1 mo, respectively, recommended in healthy adolescents and young adults. We review available data on vaccine coverage of serogroup B strains. Methods A literature review identified relevant information from peer-reviewed publications, congress presentations, and ClinicalTrials.gov. Previously presented but unpublished data from phase 2/3 studies were included. Results After 2 MenB-FHbp doses, percentages of adolescents and young adults achieving serum bactericidal activity assay using human complement (hSBA) titers ≥1:8 were 79%–99% for 4 heterologous representative test strains and 71%–97% for 10 additional strains, confirming cross-protection against a diverse strain panel (Figure 1; unpublished data). These 14 heterologous strains collectively represent ~80% of disease-causing strains in the US and Europe. In a published study with limited sample size, 44%–78% of subjects had hSBA titers ≥1:8 against strains from 4 US college outbreaks after 2 MenB-FHbp doses. After 2 MenB-4C doses, percentages of 10–25-year-olds achieving hSBA titers ≥1:5 against 3 reference strains homologous to the vaccine antigen were 82%–93% (published data); 15%–100% of adolescents achieved hSBA titers ≥1:4 against a panel of 14 strains (unpublished data). Of college students who received 2 MenB-4C doses, 53%–93% achieved hSBA titers ≥1:4 against 5 US outbreak strains (4/5 strains had antigenic similarity to MenB-4C; published data). Conclusion MenB-FHbp and MenB-4C protect against various serogroup B strains. As for the breadth of coverage provided by these vaccines, available data show that MenB-FHbp elicits robust immune responses to a wide variety of disease-causing strains prevalent in the US (Figure 2). Disclosures Tamera Coyne-Beasley, MD, MPH, Pfizer Inc and GlaxoSmithKline (Advisor or Review Panel member) Joseph Bocchini, MD, Pfizer Inc and Dynavax (Advisor or Review Panel member) Alejandro Cane, M.D., Pfizer Inc (Employee, Shareholder) Cindy Burman, PharmD, Pfizer Inc (Employee, Shareholder) Maria J. Tort, PhD, Pfizer Inc (Employee, Shareholder) Jessica Presa, MD, Pfizer Inc (Employee, Shareholder)

1183. Serum Bactericidal Activity Induced by Live Attenuated Pertussis Vaccine BPZE1 is Comparable to Boostrix™

Background In a Phase 2b, multi-center, placebo-controlled, randomized study, intranasal BPZE1 induced mucosal and serum antibodies to pertussis antigens and protected against subsequent colonization following attenuated challenge with BPZE1 3 months later. BoostrixTM also induced serum but not mucosal antibodies and did not protect against BPZE1 challenge. We have evaluated the induction of serum bactericidal activity (SBA) for Bordetella pertussis by BPZE1 or Boostrix vaccination. A previous study showed that Boostrix induction of SBA is dependent on Prn whereas B. pertussis infection induces SBA targeting Prn and other antigens. Methods A convenience set of subjects who had a broad range of Prn and PT IgG serum concentrations from treatment groups who received BPZE1+BPZE1 or Boostrix+Placebo (Day 1 and 85 vaccination) were randomly selected to assess SBA using B. pertussis strain B1917. Three timepoints (baseline, 28 days following first and second vaccination) were analyzed and interpolated 50% killing titers determined. The relationship to Prn IgG concentration was assessed. Results BPZE1 and Boostrix elicited similar and significant increases in SBA following vaccination. BPZE1 and Boostrix elicit anti-Prn IgG, with Boostrix eliciting higher concentrations. A greater SBA response relative to PRN IgG was observed for BPZE1 compared to Boostrix. SBA-Prn correlations were high post-Boostrix (0.74) as previously reported; correlation was lower (0.35) following BPZE1, suggesting the involvement of broader antigenic protection beyond Prn alone. Table of GMT and GMFR in SBA and Prn IgG Conclusion In this exploratory investigation, the novel intranasal live-attenuated pertussis vaccine BPZE1 induced SBA titers that were similar to Boostrix using a B. pertussis strain representative of current disease isolates. SBA-Prn correlations were high post-Boostrix, consistent with prior reports showing Prn is the acellular vaccine antigen that mediates SBA. In contrast, BPZE1 bactericidal antibodies appear broader than Prn which may be important given the global rise of Prn-deficient B. pertussis strains. Disclosures All Authors: No reported disclosures

Immersion Vaccination by a Biomimetic-Mucoadhesive Nanovaccine Induces Humoral Immune Response of Red Tilapia (Oreochromis sp.) against Flavobacterium columnare Challenge

Immersion vaccination with a biomimetic mucoadhesive nanovaccine has been shown to induce a strong mucosal immune response against columnaris disease, a serious bacterial disease in farmed red tilapia caused by Flavobacterium columnare. However, the induction of a systemic immune response by the vaccine is yet to be investigated. Here, we examine if a specific humoral immune response is stimulated in tilapia by a biomimetic-mucoadhesive nanovaccine against Flavobacterium columnare using an indirect-enzyme-linked immunosorbent assay (ELISA), serum bactericidal activity (SBA) and the expression of immune-related genes within the head-kidney and spleen, together with assessing the relative percent survival of vaccinated fish after experimentally infecting them with F. columnare. The anti-IgM antibody titer of fish at 14 and 21 days post-vaccination was significantly higher in chitosan complex nanoemulsion (CS-NE) vaccinated fish compared to fish vaccinated with the formalin-killed vaccine or control fish, supporting the serum bactericidal activity results at these time points. The cumulative mortality of the unvaccinated control fish was 87% after challenging fish with the pathogen, while the cumulative mortality of the CS-NE vaccinated group was 24%, which was significantly lower than the formalin-killed vaccinated and control fish. There was a significant upregulation of IgM, IgT, TNF α, and IL1-β genes in the spleen and kidney of vaccinated fish. Significant upregulation of IgM and IgT genes was observed in the spleen of CS-NE vaccinated fish. The study confirmed the charged-chitosan-based mucoadhesive nanovaccine to be an effective platform for immersion vaccination of tilapia, with fish generating a humoral systemic immune response against columnaris disease in vaccinated fish.

Impacts on the immune system of Cyprinus carpio exposure with a mixed algal extract against Aeromonas hydrophila

This study evaluates the influence of mixed algal extract (<i>Chlorella vulgaris</i>, <i>Euglena viridis</i> and <i>Spirulina platensis</i>) on common carp <i>Cyprinus Carpio</i>, which infected infect with bacterial pathogen <i>Aeromonas hydrophila</i>. <i>C. carpio</i> was administered intraperitoneally with various doses such as methanol extract (0, 0,1, 1, 10 and 100 mg/kg). The immunological parameters of fish blood and serum samples (Neutrophil activity, Lysozyme activity, Serum myeloperoxidase intensity, Serum bactericidal activity, and Serum antiprotease activity) were investigated at 7, 14, 21, and 28 days of post-immunization. Fish had been tested by virulent<i> A. hydrophila</i> for 30 days after treatment and 14 days after infection were identified with mortalities. The findings showed that neutrophil levels, lysozyme activity, serum bactericidal activity, myeloperoxidase activity, and serum antiprotease activity significantly enhanced (p<0.05) compared to untreated control. Mixed dietary algae at 1 and 10 mg/kg levels demonstrated slightly (p<0.05) higher relative percentage survival (90 percent) than control against <i>A. hydrophila</i> disease infection. Results indicated that mixed algal extract in <i>C. carpio</i> positively impacts non-specific immune parameters and boosts disease tolerance to <i>A. hydrophila</i> infections.

PSXIII-30 Late-Breaking: The change of immune function markers and spectrotype of cytokine causing subclinical and clinical mastitis in the dairy cows

The study aimed to determine the immune function markers of clinically healthy cows and cows with subclinical and clinical mastitis caused by the coagulase-negative staphylococci. The materials were milk and blood of cows (n = 20; first group) had the clinical mastitis caused by S. aureus and S. haemolyticus, another 20 (second group) had the subclinical mastitis caused by S. aureus and S. haemolyticus, another 20 (third group) were clinically health cows. The milk was examinated by a Californian mastitis test. The immune markers of blood were researched by ELISA using Bovine Elisa Kit (Cloud-CloneCorp. HoustonTX, USA) and relevance methods (The guidelines for the assessment and correction of animal immune status, Voronezh, Russia, 2005). It has been found that the blood of cows of the 2d group had a high level of Interleukin- 2 (15.9±0.4 pg/mL), TNF-α (639.2±19.1 pg/mL), CIC (0.128±0.01 g/L), Serum Bactericidal Activity (78.5±1.4 %) compared with 3d group. It was the reducing of Ig level by 19.6% (20.6±0.3g/L) and Lysozyme activity by 28.4% (2.097±0.02 µg/mL) (P &lt; 0,05-0,001). The comparative analysis of immune function markers in the blood of 1st and 3d groups showed the reduction of TNF-α by 23,3%, Ig level by 19,6 %, Lysozyme activity by 32,8%, T- lymphocytes by 27,2%, and the increasing of CIC by 52,3%, Serum Bactericidal Activity by 6,8%, B- lymphocytes by 10,1% (P &lt; 0,05-0,001), Phagocytic activity of leucocytes by 6,4%. Mastitis events caused by the coagulase-negative staphylococci were associated with reducing of cellular and humoral immunity by twice increasing of Interleukin-2 level.

A Salmonella Typhi Controlled Human Infection Study for Assessing Correlation between Bactericidal Antibodies and Protection against Infection Induced by Typhoid Vaccination

Vi-polysaccharide conjugate vaccines are efficacious against typhoid fever in children living in endemic settings, their recent deployment is a promising step in the control of typhoid fever. However, there is currently no accepted correlate of protection. IgG and IgA antibodies generated in response to Vi conjugate or Vi plain polysaccharide vaccination are important but there are no definitive protective titre thresholds. We adapted a luminescence-based serum bactericidal activity (SBA) for use with S. Typhi and assessed whether bactericidal antibodies induced by either Vi tetanus toxoid conjugate (Vi-TT) or Vi plain polysaccharide (Vi-PS) were associated with protection in a controlled human infection model of typhoid fever. Both Vi-PS and Vi-TT induced significant increase in SBA titre after 28 days (Vi-PS; p < 0.0001, Vi-TT; p = 0.003), however higher SBA titre at the point of challenge did not correlate with protection from infection or reduced symptom severity. We cannot eliminate the role of SBA as part of a multifactorial immune response which protects against infection, however, our results do not support a strong role for SBA as a mechanism of Vi vaccine mediated protection in the CHIM setting.

Antibodies Elicited by the Shigella sonnei GMMA Vaccine in Adults Trigger Complement-Mediated Serum Bactericidal Activity: Results From a Phase 1 Dose Escalation Trial Followed by a Booster Extension

Shigella is the second most deadly diarrheal disease among children under five years of age, after rotavirus, with high morbidity and mortality in developing countries. Currently, no vaccine is widely available, and the increasing levels of multidrug resistance make Shigella a high priority for vaccine development. The single-component candidate vaccine against Shigella sonnei (1790GAHB), developed using the GMMA technology, contains the O antigen (OAg) portion of lipopolysaccharide (LPS) as active moiety. The vaccine was well tolerated and immunogenic in early-phase clinical trials. In a phase 1 placebo-controlled dose escalation trial in France (NCT02017899), three doses of five different vaccine formulations (0.06/1, 0.3/5, 1.5/25, 3/50, 6/100 µg of OAg/protein) were administered to healthy adults. In the phase 1 extension trial (NCT03089879), conducted 2–3 years following the parent study, primed individuals who had undetectable antibody levels before the primary series received a 1790GAHB booster dose (1.5/25 µg OAg/protein). Controls were unprimed participants immunized with one 1790GAHB dose. The current analysis assessed the functionality of sera collected from both studies using a high-throughput luminescence-based serum bactericidal activity (SBA) assay optimized for testing human sera. Antibodies with complement-mediated bactericidal activity were detected in vaccinees but not in placebo recipients. SBA titers increased with OAg dose, with a persistent response up to six months after the primary vaccination with at least 1.5/25 µg of OAg/protein. The booster dose induced a strong increase of SBA titers in most primed participants. Correlation between SBA titers and anti-S. sonnei LPS serum immunoglobulin G levels was observed. Results suggest that GMMA is a promising OAg delivery system for the generation of functional antibody responses and persistent immunological memory.

Endogenous complement human serum bactericidal assay (enc-hSBA) for vaccine effectiveness assessments against meningococcal serogroup B

Immunogenicity of vaccines against meningococcal serogroup B (MenB) has been assessed pre-licensure with a human serum bactericidal activity assay (hSBA), tested against small numbers of strains. We report the qualification/validation of an alternative qualitative hSBA which uses endogenous complement (enc-hSBA) present in the vaccinee’s serum. Serum samples were collected from adults pre-vaccination and post-vaccination with the 4-component MenB vaccine (4CMenB). A representative panel of invasive isolates and 4 antigen-specific indicator strains were used in qualification experiments. Each strain was tested in ≥3 experiments with pre/post-vaccination sera to evaluate intermediate precision. A 110-strain panel and the 4 indicator strains met qualification criteria, demonstrating assay precision. Assay robustness, specificity and sensitivity were demonstrated using the 4 indicator strains. Enc-hSBA is highly standardized, allows testing across large panels of epidemiologically-relevant MenB strains, and accounts for complement activity differences between vaccinees. Therefore, enc-hSBA enables a more accurate estimation of effectiveness for vaccines against MenB.