Beatrice Nassanga Francis Poster 2025

Miss Beatrice Nassanga Francis

University of Oxford, UK

Developing bovine immune organoids for the screening of bovine TB vaccine candidates

Poster Abstract

Bovine tuberculosis (bTB) causes significant economic losses to farmers in the UK and many low-middle income countries (LMICs), and the only currently available vaccine, BCG, is insufficient. A major challenge in novel bTB vaccine development is the lack of reliable in vitro/ex vivo screening tools, leading to a heavy reliance on costly and resource-intensive in vivo cattle studies. Immune organoids derived from secondary lymphoid organs have been developed for vaccine testing using vaccines against rabies, influenza, and SARS-CoV-2 as proof-of-concept, but to date this approach has not been applied to cattle.

We describe the development of a bovine immune organoid model and optimisation of associated immunological assays to facilitate bTB vaccine candidate screening. Secondary lymphoid tissues (tonsils, lymph nodes and spleens) obtained from 12 healthy Bos taurus cattle (six naïve and six BCG-vaccinated) were dissociated and the harvested cells cryopreserved. The cells were then thawed, checked for viability, and stimulated at different cell densities with media-only (negative control), M. bovis whole cell lysate (WCL), Rift Valley Fever antigen (as a non-specific stimulation control), and PMA/I (positive control) over 7, 14, and 21 days. Microscopy imaging was performed to visualise aggregation and spatial organisation of clustered cells. Supernatants harvested at different time points were analysed for production of WCL-specific IgM and IgG. At the end of the culture period, cell pellets were harvested for ELISpot analysis to identify antibody-secreting B cells and for flow cytometry to profile key immune cell subsets including T and B cells, natural killer cells, dendritic cells and monocytes.

This work represents the initial phase of the project, with the next step being validation of these organoids against in vivo immunogenicity outcomes using bTB vaccine candidates for proof-of-concept.

Biography

I am a final year PhD student at Makerere University, Uganda, and the University of Oxford. I also work as a research assistant in the tuberculosis (TB) vaccines groups of Prof Helen McShane and Associate Prof Rachel Tanner, University of Oxford. I have great interest in the study of TB, a disease which represents a major burden in Africa and Asia. I am particularly interested in investigating the problem of the waning efficacy of TB vaccines and contributing to the development of a more effective TB vaccine. For my PhD project, I am investigating the host and microbial factors influencing the immunogenicity of BCG revaccination and the candidate TB vaccine combination ChAdOx1 85A - MVA85A. I am also working on several related projects, including developing immune organoids for high-throughput immunogenicity screening of novel TB vaccine candidates.

I previously attained an MSc in Immunology and Clinical Microbiology at Makerere University in 2019, during which I investigated T cell responses (phenotype and polyfunctionality) in Mycobacterium tuberculosis (MTB) and Non-tuberculous Mycobacteria (NTM) in the sensitised and un-sensitised Ugandan population. This followed challenges in distinguishing NTM sensitisation from MTB with the conventional Tuberculin Skin Test and Interferon gamma release assays, and the discovery of unique NTM T cell epitopes. I have a Bachelor’s degree in Biomedical Laboratory Technology also attained at Makerere University in 2014. From 2014 to 2016, I worked as a laboratory technologist on several TB and measles vaccine related research projects at MRC/UVRI and LSHTM Uganda Research Unit.