Immunofluorescent anti-Junin virus antibodies in Argentine hemorrhagic fever.

Immunofluorescent anti-Junin virus antibodies were detected in 15 nonfatal cases of Argentine hemorrhagic fever between the 2nd and 3rd week after onset of symptoms. In most cases, antibodies appeared by the day of clinical improvement, or between 2 and 4 days later. It was interesting to note that in 5 of 11 cases studied, the first positive serum sample presented anti-Junin virus immunofluorescent antibodies in IgA. In 2 of these 5 cases, IgA was the only immunoglobulin with antibody activity in the early positive serum sample.