Immunization with recombinant Pb27 protein reduces the levels of pulmonary fibrosis caused by the inflammatory response against Paracoccidioides brasiliensis.

Abstract

Paracoccidioidomycosis (PCM) is a systemic mycosis in which the host response to the infectious agent typically consists of a chronic granulomatous inflammatory process. This condition causes lesions that impair lung function and lead to chronic pulmonary insufficiency resulting from fibrosis development, which is a sequel and disabling feature of the disease. The rPb27 protein has been studied for prophylactic and therapeutic treatment against PCM. Previous studies from our laboratory have shown a protective effect of rPb27 against PCM. However, these studies have not determined whether rPb27 immunization prevents lung fibrosis. We therefore conducted this study to investigate fibrosis resulting from infection by Paracoccidioides brasiliensis in the lungs of animals immunized with rPb27. Animals were immunized with rPb27 and subsequently infected with a virulent strain of P. brasiliensis. Fungal load was evaluated by counting colony-forming units, and Masson's trichrome staining was performed to evaluate fibrosis at 30 and 90 days post-infection. The levels of CCR7, active caspase 3, collagen and cytokines were analyzed. At the two time intervals mentioned, the rPb27 group showed lower levels of fibrosis on histology and reduced levels of collagen and the chemokine receptor CCR7 in the lungs. CCR7 was detected at higher levels in the control groups that developed very high levels of pulmonary fibrosis. Additionally, the immunized groups showed high levels of active caspase 3, IFN-γ, TGF-β and IL-10 in the early phase of P. brasiliensis infection. Immunization with Pb27, in addition to its protective effect, was shown to prevent pulmonary fibrosis.