Antibody responses against bacterial glycans affinity mature and diversify in germinal centers.bioRxiv : the preprint server for biology • April 16, 2025
Holly Fryer, Catherine Pitt, Hannah Frost, Nitika Kandhari, Sean Byars, Pailene Lim, Trang Nguyen, Kaneka Chheng, Natalie Caltabiano, Alana Whitcombe, Julianne Hamelink, Dean Andrew, Gareth Lloyd, Brian Wilson Boyd, Nicola Slee, Jodie Ballantine, Sarju Vasani, Kathryn Girling, Liam Gubbels, Eric Levi, Karen Davies, Stuart Tangye, Jonathan Noonan, Nicole Moreland, Isaak Quast, Marcus Robinson, Stephen Scally, Melanie Neeland, Shivanthan Shanthikumar, Joshua Osowicki, David Tarlinton, Andrew Steer, Michelle Boyle, Danika Hill
Anti-carbohydrate antibodies (Abs) play crucial roles in pathogen control, but their generation remains poorly understood. By studying responses to Streptococcus pyogenes in humans, we reveal that the glycan-targeted response shifts from IgM towards IgG and IgA memory with age and antigen exposure across blood, spleen, and tonsils. Both natural colonization and controlled human infection with S. pyogenes increased class-switched B cells, with evidence of within-clone switching. Glycan-specific B cells readily participated in germinal center (GC) responses and showed robust somatic hypermutation despite a molecular signature consistent with receiving reduced T cell help. We conclude that mucosal pathogen encounters elicit glycan responses that class-switch, evolve and diversify through the GC. These findings reveal how age and infection history can influence the quality, quantity, and isotype use of glycan-specific B cells, with implications for the design and schedule of glycan-containing vaccines.
Population pharmacokinetics of penicillin G: insights into increased clearance at low concentrations to guide development of improved long-acting formulations for syphilis and prevention of rheumatic fever.Antimicrobial Agents And Chemotherapy • May 20, 2025
Okhee Yoo, Sam Salman, Thel Hla, Joshua Osowicki, Madhu Page Sharp, Julie Marsh, Renae Barr, Kristy Azzopardi, Michael Morici, Kevin Batty, Stephanie Enkel, Joseph Kado, Lara Hatchuel, Alma Fulurija, James Mccarthy, Thomas Snelling, Andrew Steer, Jonathan Carapetis, Laurens Manning
Although benzylpenicillin (penicillin G) is listed by the World Health Organization as an Essential Medicine, dose optimization is a persistent challenge, especially for long-acting intramuscular formulations. Maintaining sustained antibiotic exposure at target concentrations is crucial for secondary chemoprophylaxis of rheumatic heart disease and treatment of syphilis. This study compared the pharmacokinetic profile of continuous low-dose benzylpenicillin infusions with a standard-dose bolus and evaluated which renal function marker (serum creatinine, cystatin C, or combined e-glomerular filtration rate [eGFR]) best predicted clearance. Healthy adult volunteers received a single 600 mg IV benzylpenicillin bolus followed by randomization to continuous infusions targeting steady-state concentrations of 3, 6, 9, 12, or 20 ng/mL. Plasma benzylpenicillin concentrations were measured by liquid chromatography-mass spectrometry. Population pharmacokinetic analysis was performed using NONMEM by incorporating both bolus and infusion data, and various GFR estimations were evaluated as covariates for clearance. Data from 72 participants were analyzed, including 504 bolus and 389 continuous infusion samples. A two-compartment model improved fit when the ratio of central volume of distribution between bolus and low-dose infusion was incorporated, and clearance differences at steady state plasma concentration of 3 ng/mL were accounted for. Of the GFR estimations, cystatin C-based eGFR significantly enhanced model fit compared with creatinine-based equations. Benzylpenicillin pharmacokinetics at very low concentrations demonstrated both a higher volume of distribution and increased clearance. Cystatin C-based eGFR may more accurately predict benzylpenicillin clearance, enabling precision dosing for long-acting preparations used for treatment of syphilis and prevention of rheumatic fever.
Cardiac monitoring safety assessment framework for early phase group a streptococcal vaccine trials.Vaccine • March 16, 2025
James Marangou, Andrea Beaton, Alma Fulurija, Jonathan Carapetis, Andrew Steer, Liesl ZĂĽhlke, Cheryl Keech
This paper presents a comprehensive cardiac safety framework for early clinical development of Streptococcus pyogenes (Group A Streptococcus) vaccines, endorsed by the Strep A Vaccine Global Consortium (SAVAC) and the Australian Strep A Vaccine Initiative (ASAVI). Given historical concerns about vaccine-associated acute rheumatic fever (ARF), we have established standardized echocardiography protocols integrated with clinical assessment for monitoring cardiac safety in early-phase vaccine trials. We recommend that the Modified Jones Criteria for ARF should be the primary focus for cardiac Adverse Events of Special Interest (AESI) monitoring in S. pyogenes vaccine trials, with echocardiography utilized within this clinical context. Two echocardiography protocols-comprehensive for baseline screening and diagnostic confirmation and abbreviated for interval monitoring-should be performed using full-capability equipment by certified professionals. The framework includes specific exclusion criteria for trial participants, active and passive surveillance for ARF symptoms, and a structured approach to investigating suspected cases. This pragmatic approach enables advancement of S. pyogenes vaccine clinical development with appropriate safety oversight while maintaining operational feasibility. While designed for phase 1 and 2 trials in low-endemic settings, these recommendations provide a foundation that can be adapted for later-phase trials in high-endemic regions as vaccine development progresses.
Epidemiology and clinical profile of paediatric RSV infections: insights from a 6-year Australian cohort study.Archives of disease in childhood • March 03, 2025
Jane Tuckerman, Jeremy Anderson, Annette Alafaci, Paul Licciardi, Andrew Steer, Ian Barr, Nigel Crawford, Danielle Wurzel
Many Australian states experienced unpredictable patterns of respiratory syncytial virus (RSV) infection during the COVID-19 pandemic. Understanding the profile of children with severe RSV infections and changes in the pandemic era may inform RSV prevention programmes. While we previously described the out-of-season surge of RSV infections on relaxation of non-pharmaceutical interventions (NPIs)1 and predictors of severe RSV in the pre-pandemic era,2 this paper includes additional data and secondary analysis. The aims of this study were to describe the impacts of the COVID-19 pandemic on (1) the epidemiology of RSV infections, (2) the clinical profile and (3) the severity of children hospitalised with RSV infections in a single paediatric hospital in Melbourne, Australia.
In this retrospective cohort study, we used data from children (<2 years) hospitalised for laboratory-confirmed RSV infection over six RSV seasons (1 January 2017 and 31 December 2022). Data were collected as part of the WHO RSV surveillance3 and CAMEO-RSV study2 (Clinical And Molecular Epidemiology And Immune Characteristics Of Respiratory
Streptococcal serology reference intervals in an Australian pediatric cohort.Journal Of The Pediatric Infectious Diseases Society • January 14, 2025
Shu Tsoi, Sharon Choo, Lai-yang Lee, Paul Monagle, Stephen Hearps, Vasiliki Karlaftis, Chantal Attard, Janet Burgess, Chuong Tran, Sheree Bazeley, Natalie Challen, Andrew Steer, Joshua Osowicki
Background: Diagnostic criteria for acute rheumatic fever and post-streptococcal glomerulonephritis, the two major autoimmune complications of Streptococcus pyogenes infection, include serological evidence of preceding infection. The S. pyogenes proteins streptolysin O (ASO) and deoxyribonuclease B (ADB) are the most widely used targets for clinical streptococcal serology. We aimed to establish age-based reference intervals (RI) for healthy children in Victoria, Australia, to guide interpretation of anti-streptolysin O levels measured by turbidimetry and nephelometry, and anti-deoxyribonuclease B levels by nephelometry. MethodsSerum samples were collected from healthy pediatric cohorts aged 32 weeks gestation to < 18 years at 4 hospitals in Melbourne, Australia, between February 2015 and October 2018. ASO levels were measured in two cohorts, by turbidimetry in Cohort 1, and by nephelometry in Cohort 2. ADB levels were measured by nephelometry in Cohort 2. Reference intervals (RI) for each age group were generated, including 80% upper limit of normal (ULN) cut-offs.
Results: ASO levels were measured by turbidimetry for 359 samples from Cohort 1, and ASO and ADB levels were measured by nephelometry for 360 samples from Cohort 2. ASO levels, measured by turbidimetry, were highest in children 5 to 9 years of age (80% ULN 346 IU/mL) in Cohort 1. For Cohort 2, there was a linear age-related increase in ASO levels measured by nephelometry (80% ULN 426 IU/mL in those 15 to < 18 years old) and ADB levels were highest in children aged 10 to 14 years (80% ULN 454 IU/mL).
Conclusions: We established age-specific RI for ASO and ADB levels measured by turbidimetry and nephelometry for healthy Australian children. This study highlights the importance of local method-specific age-based RI to interpret ASO and ADB levels when clinicians suspect acute rheumatic fever or post-streptococcal glomerulonephritis in children.
