Safety and immunogenicity of a 4-component GMMA-based Shigella vaccine in healthy European adults: Stage 1 of a randomized, controlled phase I/II clinical trial.

BACKGROUND: We report data from Stage 1 of an ongoing two-staged, phase I/II randomized clinical trial (NCT05073003) with a 4-component Generalized Modules for Membrane Antigens-based vaccine against Shigella sonnei and S. flexneri 1b, 2a and 3a (altSonflex1-2-3, GSK). METHODS: 18-50-year-old Europeans (N=102) were randomized (2:1) to receive two injections of altSonflex1-2-3 or placebo at 3- or 6-month interval. Safety and immunogenicity were assessed at pre-specified timepoints. RESULTS: The most common solicited administration-site event (until 7 days post-each injection) and unsolicited adverse event (until 28 days post-each injection) were pain (altSonflex1-2-3: 97.1%; Placebo: 58.8%) and headache (32.4%; 23.5%), respectively. All serotype-specific functional IgG antibodies peaked 14-28 days post-injection 1 and remained substantially higher than pre-vaccination at 3 or 6 months post-vaccination; the second injection did not boost but restored the initial immune response. The highest seroresponse rates (≥4-fold increase in titers over baseline) were obtained against S. flexneri 2a (ELISA: post-injection 1: 91.0%; post-injection 2 [Day {D}113; D197]: 100%; 97.0%; serum bactericidal activity (SBA): post-injection 1: 94.4%; post-injection 2: 85.7%; 88.9%) followed by S. sonnei (ELISA: post-injection 1: 77.6%; post-injection 2: 84.6%; 78.8%; SBA: post-injection 1: 83.3%; post-injection 2: 71.4%; 88.9%). Immune responses against S. flexneri 1b and S. flexneri 3a, as measured by both ELISA and SBA, were numerically lower compared to those against S. sonnei and S. flexneri 2a. CONCLUSIONS: No safety signals or concerns were identified. altSonflex1-2-3 induced functional serotype-specific immune responses, allowing further clinical development in the target population.

What is the context? Shigella bacteria cause severe and often bloody diarrhea, called shigellosis, that affects mostly young children and can be life-threatening. Shigellosis is particularly common in low- and middle-income countries due to inadequate sanitation and limited access to healthcare. Since the immune response to Shigella is serotype-specific, an ideal vaccine should include multiple Shigella serotypes to ensure broad protection. What is new? We developed a novel vaccine against Shigella that includes Shigella sonnei and three prevalent Shigella flexneri serotypes. In Stage 1 (phase I) of the study, healthy European adults received two vaccine injections given 3 or 6 months apart. We found that: The vaccine was well tolerated, and no safety signals or concerns were identified.Regardless of the interval between injections, specific antibodies were elicited against all four Shigella serotypes, with highest levels against Shigella flexneri 2a and Shigella sonnei.Functional antibody levels peaked after the first injection, remaining higher than the baseline up to 6 months. A second injection did not boost responses but restored functional antibody levels to those after the first injection. What is the impact? The vaccine can now be tested in Stage 2 (phase II) of the study in Africa, a region highly affected by shigellosis.

Putative correlates of protection against shigellosis assessing immunomarkers across responses to S. sonnei investigational vaccine.

Shigella spp. are a leading bacterial cause of diarrhea. No widely licensed vaccines are available and there is no generally accepted correlate of protection. We tested a S. sonnei Generalized Modules for Membrane Antigen (GMMA)-based vaccine (1790GAHB) in a phase 2b, placebo-controlled, randomized, controlled human infection model study (NCT03527173) enrolling healthy United States adults aged 18-50 years. We report analyses evaluating immune responses to vaccination, with the aim to identify correlates of risk for shigellosis among assessed immunomarkers. We found that 1790GAHB elicited S. sonnei lipopolysaccharide specific α4ß7+ immunoglobulin (Ig) G and IgA secreting B cells which are likely homing to the gut, indicating the ability to induce a mucosal in addition to a systemic response, despite parenteral delivery. We were unable to establish or confirm threshold levels that predict vaccine efficacy facilitating the evaluation of vaccine candidates. However, serum anti-lipopolysaccharide IgG and bactericidal activity were identified as potential correlates of risk for shigellosis.

Effect of Intrapartum Azithromycin vs Placebo on Neonatal Sepsis and Death: A Randomized Clinical Trial.

Importance: Neonatal sepsis is a leading cause of neonatal mortality. New interventions are needed to decrease neonatal sepsis and mortality in regions with highest burden. Objective: To evaluate the efficacy of intrapartum azithromycin to reduce neonatal sepsis or mortality, as well as neonatal and maternal infections. Design, Setting, and Participants: This double-blind, placebo-controlled, randomized clinical trial enrolled and followed up birthing parents and their infants at 10 health facilities in The Gambia and Burkina Faso, West Africa, between October 2017 and May 2021. Interventions: Participants were assigned at random to receive oral azithromycin (2 g) or placebo (ratio 1:1) during labor. Main Outcomes and Measures: The primary outcome was a composite of neonatal sepsis or mortality, with the former defined based on microbiologic or clinical criteria. Secondary outcomes were neonatal infections (skin, umbilical, eye and ear infections), malaria, and fever; postpartum infections (puerperal sepsis, mastitis), fever, and malaria; and use of antibiotics during 4-week follow-up. Results: The trial randomized 11 983 persons in labor (median age, 29.9 years). Overall, 225 newborns (1.9% of 11 783 live births) met the primary end point. The incidence of neonatal mortality or sepsis was similar in the azithromycin and placebo groups (2.0% [115/5889] vs 1.9% [110/5894]; risk difference [RD], 0.09 [95% CI, -0.39 to 0.57]), as was the incidence of neonatal mortality (0.8% vs 0.8%; RD, 0.04 [95% CI, -0.27 to 0.35]) and neonatal sepsis (1.3% vs 1.3%; RD, 0.02 [95% CI, -0.38 to 0.43]). Newborns in the azithromycin group compared with the placebo group had lower incidence of skin infections (0.8% vs 1.7%; RD, -0.90 [95% CI, -1.30 to -0.49]) and need for antibiotics (6.2% vs 7.8%; RD, -1.58 [95% CI, -2.49 to -0.67]). Postpartum parents in the azithromycin group had lower incidence of mastitis (0.3% vs 0.5%; RD, -0.24 [95% CI, -0.47 to -0.01]) and puerperal fever (0.1% vs 0.3%; RD, -0.19 [95% CI, -0.36 to -0.01]). Conclusions and Relevance: Azithromycin administered orally during labor did not reduce neonatal sepsis or mortality. These results do not support routine introduction of oral intrapartum azithromycin for this purpose. Trial Registration: ClinicalTrials.gov Identifier: NCT03199547.

Towards a Four-Component GMMA-Based Vaccine against Shigella.

Shigellosis remains a major public health problem around the world; it is one of the leading causes of diarrhoeal disease in low- and middle-income countries, particularly in young children. The increasing reports of Shigella cases associated with anti-microbial resistance are an additional element of concern. Currently, there are no licensed vaccines widely available against Shigella, but several vaccine candidates are in development. It has been demonstrated that the incidence of disease decreases following a prior Shigella infection and that serum and mucosal antibody responses are predominantly directed against the serotype-specific Shigella O-antigen portion of lipopolysaccharide membrane molecules. Many Shigella vaccine candidates are indeed O-antigen-based. Here we present the journey towards the development of a potential low-cost four-component Shigella vaccine, eliciting broad protection against the most prevalent Shigella serotypes, that makes use of the GMMA (Generalized Modules for Membrane Antigens) technology, a novel platform based on bacterial outer membranes for delivery of the O-antigen to the immune system.