Biology subjects

Osowicki, J.

Publications and source records attributed to Osowicki, J..

6 recordsLinked to original sources

bioRxiv2026

Characterisation and manufacture of a Neisseria gonorrhoeae challenge agent for use in an oropharyngeal controlled human infection model

BackgroundDespite the importance of oropharyngeal gonorrhoea in transmission, suboptimal antimicrobial responses and propensity for horizontal transfer of antimicrobial resistance at this site, it remains understudied. An oropharyngeal N. gonorrhoeae controlled human infection model (CHIM) represents a promising tool to study infection and undertake translational research. MethodsA panel of five contemporary N. gonorrhoeae isolates were subject to detailed characterisation to assess antimicrobial susceptibility, in vitro infectivity, cytotoxicity and serum sensitivity to inform challenge agent selection. A method for challenge agent manufacture, including release testing, was developed and validated. FindingsAll candidate isolates were able to infect the surface of pharyngeal and cervical cells in vitro. One isolate displayed an invasive phenotype, induced higher inflammatory cytokine production and displayed elevated serum resistance and was excluded. The remaining four isolates were minimally inflammatory, did not induce cytotoxicity and were susceptible to serum killing. Three of the four isolates grew in a defined liquid medium. Together these results led to the selection of a contemporary N. gonorrhoeae isolate suitable for use in CHIM. A challenge agent manufacture workflow was established and shown to reliably and reproducibly generate doses suitable for direct inoculation in an oropharyngeal CHIM. ConclusionPhenotypic characterization of candidate N. gonorrhoeae challenge agents led to the successful identification of a contemporary isolate suitable for implementation in a novel oropharyngeal gonorrhoea CHIM. We demonstrate the feasibility of a challenge inoculum manufacturing process that aligns with international best practice guidelines.

microbiology↗

bioRxiv2026

Attenuated interferon signalling in alveolar epithelium limits resistance to Streptococcus pyogenes

The upper respiratory tract is a primary niche for Streptococcus pyogenes colonisation and disease. Lower respiratory tract infection (pneumonia) is the most common invasive S. pyogenes syndrome. Studies have not previously examined how epithelial cells, from the airway to the alveolus, respond to S. pyogenes infection. Here, we established a scalable human in vitro model by differentiating induced pluripotent stem cells (iPSCs) into mature pseudostratified airway epithelium or alveolar type 2 epithelial cells, cultured at air-liquid interface and infected with S. pyogenes (M1UK and M75 strains). Both strains attached to iPSC-derived lung epithelial cells, with significantly greater adherence to the airway epithelium by M75 compared to M1UK. Moreover, invasion by both S. pyogenes strains of alveolar epithelial cells was greater than for the airway epithelium. Dynamic S. pyogenes gene expression changes were evident between 6 and 24 hours after infection, which was influenced by the infected cell type; however, virulence genes were not significantly altered. While infection of the airway epithelium induced rapid and dynamic inflammatory signalling, the alveolar epithelium demonstrated augmented cell death and mounted a transcriptional pro-inflammatory and proliferative response that was uncoupled from cytokine secretion. The airway epithelium model exhibited consistently higher baseline type I interferon (IFN) signalling than the alveolar epithelium. Invasion by S. pyogenes and inflammation was significantly reduced in IFN-{beta}-treated alveolar epithelial cells. In summary, we have established the first model of S. pyogenes infection in physiologically relevant airway and alveolar epithelial cells. Our findings suggest that host responses to infection are influenced by lung compartment, the S. pyogenes strain type, and infection timepoint, highlighting context-specific pathways that could be leveraged therapeutically.

microbiology↗

bioRxiv2025

Sub-clinical exposure to Streptococcus pyogenes drives the development of immunity

Age-related decline in Streptococcus pyogenes infection rates suggests that immunity develops progressively through repeated exposure during early life. However, the intensity or duration of exposure required is unknown, as to why some individuals appear to develop immunity, despite having few or no previously detected infections. Here, drawing on samples from a human challenge model of pharyngeal S. pyogenes infection, we investigate whether symptomatic disease is required for induction of humoral and cellular immunity. Challenge with M75 S. pyogenes induced M75-specific serum IgG and IgA antibodies and memory B cell in both symptomatic and asymptomatic participants, with responses persisting for at least 6 months. Purified IgG from asymptomatic participants exhibited significantly enhanced binding to M75 S. pyogenes and were bactericidal when transferred into a murine model of pharyngeal infection. M75-specific IgG from these participants had an altered Fc glycosylation signature, indicative of enhanced effector function and ability to limit inflammation. However, S. pyogenes challenge had no impact on cellular or humoral immune responses to a conserved cryptic epitope, p*17. These findings show that asymptomatic (or sub-clinical) exposure to M75 S. pyogenes generates functional immune responses and contributes to the streptococcal immunity that emerges by adulthood.

microbiology↗

bioRxiv2025

Antibody responses against bacterial glycans affinity mature and diversify in germinal centers.

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.

immunology↗

bioRxiv2024

Streptococcus pyogenes pharyngitis elicits diverse antibody responses to key vaccine antigens influenced by the imprint of past infections.

Knowledge gaps regarding human immunity to Streptococcus pyogenes have impeded vaccine development. To address these gaps and evaluate vaccine candidates, we established a human challenge model of S. pyogenes pharyngitis. Here, we analysed antibody responses in serum and saliva against 19 antigens to identify characteristics distinguishing 19 participants who developed pharyngitis and 6 who did not. Pharyngitis elicited serum IgG responses to key vaccine antigens and a muted mucosal IgA response, whereas the 6 participants without pharyngitis had more pronounced IgA responses and minimal IgG responses. Serum IgG responses to pharyngitis in adult participants resembled those observed in children and were inversely correlated with the magnitude of pre-existing responses. While a straightforward correlate of protection was not evident, baseline antibody signatures distinguished clinical and immunological outcomes following experimental challenge. This highlights the influence of a complex humoral imprint from previous exposure, relevant for interpreting immunogenicity in forthcoming vaccine trials.

immunology↗

bioRxiv2024

Mycobacterium ulcerans challenge strain selection for a Buruli ulcer controlled human infection model

Critical scientific questions remain regarding infection with Mycobacterium ulcerans, the organism responsible for the neglected tropical disease, Buruli ulcer (BU). A controlled human infection model has the potential to accelerate our knowledge of the immunological correlates of disease, to test prophylactic interventions and novel therapeutics. Here we present microbiological evidence supporting M. ulcerans JKD8049 as a suitable human challenge strain. This non-genetically modified Australian isolate is susceptible to clinically relevant antibiotics, can be cultured in animal-free and surfactant-free media, can be enumerated for precise dosing, and has stable viability following cryopreservation. Infectious challenge of humans with JKD8049 is anticipated to imitate natural infection, as M. ulcerans JKD8049 is genetically stable following in vitro passage and produces the key virulence factor, mycolactone. Also reported are considerations for the manufacture, storage, and administration of M. ulcerans JKD8049 for controlled human infection.

microbiology↗