SPP1 and pulmonary fibrosis: Furthermore, expression of osteonectin and osteopontin, which have profibrotic effects in the development of pulmonary fibrosis [31, 32], was also promoted significantly (p < 0.01) and was maintained in the lung tissues of MERS-CoV-infected hDPP4-Tg mice compared to those in the control group (Fig. 7B).