IgG subclasses in human immune response to wild and attenuated (vaccine) Junin virus infection

Different proportions of IgG subclasses have previously been reported to distinguish the immune response elicited by primary and recurrent viral infections, as well as viral vaccines. The goal of this study was to study the IgG subclasses composition in the immune response of patients with Argentine hemorrhagic fever, and vaccinees with Candid #1 strain of Junin virus. Twenty-four individuals inoculated with Candid #1 vaccine and 67 patients with Argentine hemorrhagic fever were studied. Blood samples were drawn at 30, 60, and/or 180 days post-inoculation with Candid #1 and 30, 60, and 90 days after clinical onset of the disease. Specific anti-Junin virus IgG subclasses were titrated with specific human monoclonal antibody fluorescence isothiocyanate conjugate (FITC) by immunofluorescent assay (IFA). IgG(1) anti-Junin virus was found in every subject studied and IgG(3) was also detected in some patients with a severe form of Argentine hemorrhagic fever. IgG(2) and IgG(4) were not detected in any serum sample studied. The mean titer of specific IgG(1) in vaccinees was significantly lower than in patients with Argentine hemorrhagic fever (P < 0.05), but no difference was found between mild and severe cases of the disease (P > 0.05). The results of this study demonstrated a central role of IgG(1) in human recovery from infection with every strain of Junin virus, an observation stressed by the immune response to Candid #1 vaccine, which resulted in no difference in IgG subclasses composition from that found in mild cases of Argentine hemorrhagic fever.