Group B Streptococcus (GBS) is the leading cause of neonatal/infant infection, causing approximately 320,000 infections and 90,000 infant deaths globally. New-borns acquire GBS from their mothers who are unknowingly carrying GBS. The only prevention currently available is to give pregnant women antibiotics during labour if GBS has been detected during their pregnancy. However, GBS is not always detected using the current screening methods, and antibiotics do not prevent all GBS disease cases. Therefore, we need a GBS vaccine that could be given to all pregnant women to protect their infants.

To develop an effective GBS vaccine we need to understand more about the immune response to GBS, particularly the factors that affect whether a woman has GBS in her vagina (bacterial colonisation). One method to improve our understanding is to perform bacterial colonisation studies in healthy non-pregnant volunteers. We can then define factors that prevent colonisation and design vaccines to replicate these protective factors.

However, before we perform these colonisation studies, we need to define the best method to measure vaginal immune responses to GBS. We will investigate this by recruiting 50 GBS-colonised and 50 non-colonised women from the UK and the same numbers from Uganda, asking them for a swab from their vagina and back passage and to insert a menstrual cup to collect vaginal fluid every week for 16 weeks. We will compare antibody responses and participant acceptability of both methods. We will also collect a blood test at recruitment and after 16 weeks to understand the blood response to GBS carriage. This data will underpin our planned colonisation studies by identifying the best sampling technique and providing baseline data on GBS antibody levels in women with and without GBS colonisation. This proposal brings together researchers at St George’s, University of London, Imperial College London and Mulago Johns Hopkins (MUJHU) Partnership in Uganda to test the acceptability of a controlled human infection model in the UK and in Uganda. These new partnerships will enable to development of human challenge model methodology in low and middle-income countries, where the potential for a GBS vaccine is greatest and yet the least is understood about the immunology of infection.

September 2019 – December 2022