Evidence of interferon production in the hamster lung after primary or secondary exposure to parainfluenza virus type 3.

Experimental infection of the hamster respiratory tract with parainfluenza virus type 3 has been used to study the pathogenesis of viral pneumonia and the host response to infection. In this study, hamsters inoculated intranasally with parainfluenza virus type 3 produced local interferon, which was detected in lung washes obtained by in situ lavage. Interferon activity was present as early as 2 days after infection, and titers correlated directly with the quantity of virus recovered in lung washes. Parainfluenza virus type 3 was sensitive to the antiviral state induced in vitro by the lung wash interferon. Infectious virus induced interferon in cultures of immune and nonimmune lung wash cells, primarily alveolar macrophages. A secondary response of immune, mixed cultures of lymphocytes and alveolar macrophages, stimulated with inactivated virus, produced low concentrations of interferon, perhaps type II. Lymphocyte-alveolar macrophage cultures produced a pH and temperature-sensitive interferon in response to mitogen induction, characteristics of type II or immune interferons in the human and murine systems. Interferon may be an early defense involved in recovery from primary infection with parainfluenza virus type 3, and may contribute to resistance to reinfection.