Jomkwan Ongarj Poster 2025

Miss Jomkwan Ongarj

University of Oxford, UK

Identification of humoral correlates of protection in a BCG controlled human infection model (CHIM)

Poster Abstract

Tuberculosis (TB) remains a global health issue, with over 10 million new cases and 1.2 million deaths reported every year. Currently, the only available vaccine is BCG, which has been in use for over a century, and has highly variable efficacy in providing protection for adults. Although new TB vaccines primarily focusing on cellular immunity are being developed, no improved licensed vaccine for human use has been achieved yet. Potential humoral correlates of protection have been understudied.

In this study, we evaluated the quantity and function of antibodies in relation to protection in BCG controlled human infection models (CHIMs). Serum samples were collected from healthy volunteers who were either BCG-naïve (n = 23) or previously vaccinated with BCG (n = 24) at the screening time point and two weeks after intradermal BCG challenge. The BCG-vaccinated group showed a superior IgG response to M.tb Whole Cell Lysate (WCL) at two weeks post-challenge, with a higher fold change compared to the naïve group using a standardised Enzyme-Linked Immunosorbent Assay (ELISA). The antibody function of BCG-naïve and BCG-vaccinated samples before and after the challenge will also be presented, focusing on avidity, opsonisation, and phagocytosis. Associations between these measures of humoral immunity and protection from challenge will be determined. Better understanding how the quantity and/or function of BCG-induced antibodies relate to protection could help deepen our understanding of protective humoral immunity against TB, and inform the rational design of new TB vaccine candidates.