Differential innate immune responses of human macrophages and bronchial epithelial cells against Talaromyces marneffei .

is a thermally dimorphic fungal pathogen endemic in Southeast Asia. As inhalation of airborne conidia is believed as the major infection route, airway epithelial cells followed by pulmonary macrophages are the first cell types which the fungus encounters inside the host. In this study, we established an infection model based on human peripheral blood-derived macrophages (hPBDMs) cultured with the supplementation of autologous plasma. Using this model, we determined the transcriptomic changes of hPBDMs in response to infection by quantitative real-time reverse-transcription polymerase chain reaction as well as high-throughput RNA sequencing. Results showed that infection could activate hPBDMs to the M1-like phenotype and trigger a potent induction of chemokine and pro-inflammatory cytokine production as well as the expression of other immunoregulatory genes. In contrast to hPBDMs, there was no detectable innate cytokine response against in human bronchial epithelial cells (hBECs). Using a green fluorescent protein-tagged strain and confocal microscopy, internalization of the fungus by hBECs was confirmed. Live cell imaging further demonstrated that the infected cells exhibited normal cellular physiology, especially that the process of cell division could be observed. Moreover, also survived better inside hBECs than hPBDMs. Our results illustrated a potential role of hBECs to serve as reservoir cells for to evade immunosurveillance by phagocytes, from which the fungus reactivates when the host immunity is weakened and causes infection. Such immunoevasion and reactivation may also help explain the long incubation period observed for talaromycosis, in particular the travel-related cases. IMPORTANCE is an important fungal pathogen especially in Southeast Asia. To understand the innate immune response to talaromycosis, a suitable infection model is needed. Here, we established an infection model using human peripheral blood-derived macrophages (hPBDMs). We then examined the transcriptomic changes of hPBDMs in response to infection with this model. We found that contact with could activate hPBDMs to the M1-like phenotype and induced mRNA expressions of five cytokines and eight immunoregulatory genes. Contrary to hPBDMs, such immunoresponse was not elicited in human bronchial epithelial cells (hBECs), despite normal physiology observed in infected cells. We also found that infected hBECs did not eliminate as efficiently as hPBDMs. Our observation suggested that hBECs may potentially serve as reservoir cells for to evade immunosurveillance. When the host immunity deteriorates later, then the fungus reactivates and causes infection.