Macrophages and respiratory viruses.

This review highlights some of the interactions between alveolar macrophages and human/swine influenza A viruses, porcine reproductive and respiratory syndrome virus (PRRSV), bovine parainfluenza type-3 (PI-3) virus, bovine respiratory syncytial virus (BRSV) and bovine viral diarrhoea virus (BVDV). In influenza A infection, macrophage-cytokines are believed to mediate the typical constitutional effects and inflammation in the respiratory tract. The same cytokines possibly play a role in influenza-bacterial respiratory disease. PRRSV has a very restricted tropism for alveolar macrophages. The virus causes some secondary infections to be more severe, but this could not be related to impaired macrophage functions. Bovine RSV and PI-3 virus, on the other hand, interfere with selected macrophage functions. In addition, PI-3 virus adversely affects lymphocyte proliferation because it interferes with the accessory role of macrophages. One of the characteristic effects of BVDV on monocytes-macrophages is stimulation of prostaglandin E2 production.