Despite microbiological cure, about 50% of TB patients have poor lung recovery. Neutrophils are associated with lung pathology, however, CD16|CD62L-defined subsets have not been studied in TB. Using flow cytometry, we monitored frequencies, phenotype and function of neutrophils following stimulation with Mtb whole cell lysate (WCL) and ESAT-6/CFP-10 fusion protein (EC)) in relation to lung pathology.
Fresh blood from 42 adult, HIV-negative TB patients were analysed pre- and post-therapy, with disease severity determined using Chest X-Rays and bacterial load. Flow cytometry was used to monitor frequencies, phenotype and function (generation of ROS, together with CD11b, TNF and IL10 expression) of neutrophils following 2-hour stimulation with Mtb-specific antigens.
We show that total neutrophils decrease by treatment completion compared to baseline (p=0.0059); however, CD16 brCD62L br (segmented) neutrophils increase (p=0.0031) and CD16 dimCD62L br (banded) neutrophils decrease (p=0.038). Moreover, banded neutrophils are lower in patients with severe lung damage at baseline (p=0.035). Furthermore, we demonstrate that following WCL stimulation, ROS from segmented neutrophils is higher in patients with low Mtb loads even after adjusting for sex (p=0.038) while IL-10-expressing CD16 dimCD62L lo are higher in patients with mild damage (p=0.0397) at baseline. Patients showing good recovery from lung damage possess higher baseline granulocyte frequencies following WCL (p=0.042) and EC stimulation (p=0.011).
Hence, our results suggest that high ROS generation, low levels of banded neutrophils and high levels of IL10-expressing CD16 dimCD62L lo neutrophils are associated with reduced lung pathology at TB diagnosis. Hence, neutrophils are potential early indicators of TB severity and promising targets for TB host-directed therapy.
© The Author(s) 2021. Published by Oxford University Press for the Infectious Diseases Society of America.
About The Expert
Caleb Nwongbouwoh Muefong
Olumuyiwa Owolabi
Simon Donkor
Salome Charalambous
Abhishek Bakuli
Andrea Rachow
Christof Geldmacher
Jayne S Sutherland
References
PubMed