The effect of Trypanosoma equiperdum on the lesions of experimental influenza virus pneumonia

Abstract The effects of chronic Trypanosoma equiperdum infection on the lesions of influenza Ao WSN virus pneumonia in deer mice ( Peromyscus maniculatus ) were studied by light microscopy and image analysis. Trypanosome-infected mice given virus had a severe bronchitis, bronchiolitis and alveolitis characterized by respiratory epithelial necrosis and dense infiltrations of perivascular and peribronchial spaces by plasma cells. Trypanosome-free mice given virus had similar but less severe lesions and the peribronchial and perivascular infiltrates were mainly neutrophils and lymphoid cells. Regeneration of the bronchiolar epithelium was observed 2 days earlier in trypanosome-free mice than in trypanosome-infected mice. Image analysis showed that cellular infiltration of the respiratory tissues was greater during the course of influenza virus pneumonia in trypanosome-infected mice. It is suggested that the reduced ability of trypanosome-infected mice to mobilize neutrophils caused the more severe influenza virus pneumonia in these mice. It is further suggested that animals suffering from chronic trypanosomiasis have an impaired cell regeneration potential and respond to virus infections by a trypanosome-induced polyclonal activation of plasma cells.