A Virus Inhibitor in Pharyngeal Washings from Patients with Influenza.

Pharyngeal washings were obtained from 13 patients in the acute phase of influenza and 3–6 weeks later. Five specimens (from 4 patients) collected at the onset of illness contained an inhibitor of Sindbis virus as assayed in primary cultures of human amnion cells. This inhibitor was found to act on the cultured cells rather than on Sindbis virus itself. It was distinct from influenza virus and was not sedimented by ultracentrifugation. It was inactivated by crystalline trypsin. This inhibitor was not demonstrable in specimens obtained from the same patients during convalescence, from normal adults nor from a limited number of patients with other diseases.