We present a non-human primate mycobacterial growth inhibition assay (MGIA) using in vitro blood or cell co-culture with the aim of refining and expediting early tuberculosis vaccine testing. We have taken steps to optimise the assay using cryopreserved peripheral blood mononuclear cells, transfer it to end-user institutes, and assess technical and biological validity. Increasing cell concentration or mycobacterial input and co-culturing in static 48-well plates compared with rotating tubes improved intra-assay repeatability and sensitivity. Standardisation and harmonisation efforts resulted in high consistency agreements, with repeatability and intermediate precision <10% coefficient of variation (CV) and inter-site reproducibility <20% CV; although some systematic differences were observed. As proof-of-concept, we demonstrated ability to detect a BCG vaccine-induced improvement in growth inhibition in macaque samples, and a correlation between MGIA outcome and measures of protection from in vivo disease development following challenge with either intradermal BCG or aerosol/endobronchial Mycobacterium tuberculosis (M.tb) at a group and individual animal level.
Bibliographical noteFunding Information:
This work was funded by a grant awarded to RT by the National Centre for the Replacement, Refinement and Reduction of Animals in Research (NC3Rs) (grant number NC/R000905/1); and in part by a studentship awarded to RT by the Universities Federation for Animal Welfare (UFAW). Aspects of this work were conducted as part of the European Research Infrastructures for Poverty Related Diseases (EURIPRED), an EC seventh framework program (grant number 312661). HMcS is a Wellcome Trust Investigator (grant number WT 206331/Z/17/Z). We would like to thank Aeras for supporting the early MGIA development work and NHP Study 3, and for providing and distributing a standardised BCG Pasteur stock. We are grateful to Krista van Meijgaarden and Tom Ottenhoff (Leiden University Medical Centre) and to Marcus Morgan (Oxford University Hospitals NHS Trust) for use of their BD BACTEC MGIT machines for parts of this project. We would also like to thank Michael Andrews (University of California, Los Angeles) for advice on some of the statistical aspects.
- MYCOBACTERIAL GROWTH-INHIBITION
- PERIPHERAL-BLOOD MONOCYTES
- TUBERCULOSIS VACCINE