Optimising the yield from bronchoalveolar lavage on human participants in infectious disease immunology research

Abstract

Bronchoalveolar lavage (BAL) is becoming a common procedure for research into infectious disease immunology. Little is known about the clinical factors which influence the main outcomes of the procedure. In research participants who underwent BAL according to guidelines, the BAL volume yield, and cell yield, concentration, viability, pellet colour and differential count were analysed for association with important participant characteristics such as active tuberculosis (TB) disease, TB exposure, HIV infection and recent SARS-CoV-2 infection. In 337 participants, BAL volume and BAL cell count were correlated in those with active TB disease, and current smokers. The right middle lobe yielded the highest volume. BAL cell and volume yields were lower in older participants, who also had more neutrophils. Current smokers yielded lower volumes and higher numbers of all cell types, and usually had a black pellet. Active TB disease was associated with higher cell yields, and higher proportions of granulocytes, but this declined at the end of treatment. HIV infection was associated with lower cell yields and more bloody pellets, and recent SARS-CoV-2 infection with a higher proportion of lymphocytes. These results allow researchers to optimise their participant and end assay selection for projects involving lung immune cells.

Mycobacterium tuberculosis resisters despite HIV exhibit activated T cells and macrophages in their pulmonary alveoli

“…While we identi ed a major effector mechanism of resistance, considering the large number of macrophage genes differentially expressed between the study groups, it is possible that additional host response mechanisms contribute to the resistance phenotype. Considering that lymphocytic alveolitis can be observed in 20-30% of healthy persons for unknown reasons 67,70 and that close house hold contacts had the highest BAL lymphocyte counts in a large comparative survey 71 , a possible explanation could be that the infectious pressure experienced by Ugandan resisters was lower and selection for resisters with stronger lymphocytosis expression did not occur. Clearly, more detailed studies of BAL cells in different Mtb exposure settings are required to fully understand the range of the protective effects of poly-cytotoxic CD8 + T cells for Mtb infection resistance.…”

“…All subjects were nonsmokers. Bronchoscopies with BAL were performed according to current recommendations 72,73 in a research bronchoscopy facility (SU-IRG Biomedical Research Unit, Stellenbosch University) as recently described 71 . In brief, all participants were pre-screened for tness for bronchoscopy according to prede ned criteria by a study clinician with knowledge of the procedure.…”

A novel aerosol collection method shows the cough aeromicrobiome of people with tuberculosis is phylogenetically distinct from respiratory tract specimens

“…However, the sputum microbiota more closely resembles the upper respiratory tract (URT) than the lower respiratory tract (LRT) 9,10 , which is the primary site-of-disease in TB. Sampling the LRT is di cult because it requires bronchoscopy 11 , which is invasive, ethically complex for research purposes only, and expensive, often rendering which unfeasible in large cohorts where TB is prevalent 12 . Aerosols, which are more accessible, could be a useful proxy for studying the LRT, as aerosols partly originate from the LRT 13 .…”