Interferon in Human Infections with St. Louis Encephalitis Virus

The epidemic of St. Louis encephalitis in Dallas, Tex., 1966, afforded an opportunity to assess the role of interferon in human infections with this virus. Ninety-seven sera from 74 patients and 13 urine specimens from 13 patients, all with laboratory-documented St. Louis encephalitis and collected, for the most part, during the first week of illness, had no detectable interferon. Suspensions of different sections of brain, liver, kidney, and spleen from eight patients dying with St. Louis encephalitis were also assayed. Interferon was detected in suspensions of brain from three patients from whom St. Louis encephalitis virus was isolated and who died early in the course of illness. Two patients had St. Louis encephalitis virus isolated from brain but had no detectable interferon. These two patients had severe underlying illnesses: chronic lymphocytic leukemia and arteriolar nephrosclerosis with uremia. The remaining three patients died later in the course of illness, and neither virus nor interferon could be demonstrated in postmortem specimens.