The use of an immortalised bovine alveolar type II (BATII) cell line in the construction of a bilayer model of the alveolus

Abstract: Bovine tuberculosis (BTB) is a zoonosis with severe socio-economic consequences, costing the UK taxpayer over £100 million per year. The WHO estimates that 3.1 % of human cases of tuberculosis are caused by BTB (1). Early events of BTB infection are poorly understood, due to the absence of in vitro models of the alveolus, which are required to enable comparative studies between species. As part of the distal lung epithelium, alveolar type II (ATII) cells play a key role in the innate immune response and as self-renewing progenitors to replace alveolar type I (ATI) cells. Their secretion of surfactant protein helps to maintain homeostasis in the distal lung and exert protective, antimicrobial properties. A novel in vitro model would enable the evaluation of the role of the alveolar type II ATII cell in the initial stages of BTB pathogenesis. We have generated an immortalised bovine alveolar type II (BATII) cell line and used this in the construction of an in vitro tissue culture model of the bovine alveolus. This integrates an apical bilayer of bovine type II alveolar epithelial cells and basolateral pulmonary endothelial cells. Cultured at air-liquid interface, our cell line displays ATII characteristics and thus recreates the fundamental elements of the bovine pulmonary alveolus. The bilayer provides a physiologically relevant model with which to study early events in the interaction of M.bovis with the bovine lung. Using an immortalised cell line has the advantage of consistency between experimental replicates in long term studies, whilst removing the requirement for further animal use. Furthermore, the principles behind our bilayer model are transferable across species, opening up further opportunities for studies subscribing to the 3Rs ethos.