Measles virus-specific immunoglobulin G isotype immune response in early and late infections

A total of 154 human serum samples (32 acute-phase and 22 convalescent-phas e serum samples obtained within a week and between days 8 and 26 after the onset of rash, respectively, and 100 samples drawn from healthy immune adul ts) were processed by an immunofluorescence assay for the detection of immu noglobulin M (IgM), total immunoglobulin G (IgG), IgG1, IgG2, IgG3, and IgG 4 measles virus-specific antibodies. In the acute phase, IgG1 was seen firs t, followed by IgG2, IgG3, and IgG4 responses, the mean seropositivity of w hich gradually increased during convalescence, reaching 100% (standard devi ation [SD], 84 to 100%), 57% (SD, 34 to 80%), 86% (SD, 66 to 100%), and 86% (SD, 66 to 100%), respectively, IgG2 rose and fell in connection with IgG3 subclass antibodies, shelving a rate of detection of IgG2 and/or IgG3 subc lass antibodies of 95.5% (range, 100 to 86.5%) in the convalescent phase of infection. The mean percentage of measles IgG2 and IgG3 seropositivity dro pped significantly during the memory phase, to 2% (range, 2 to 6%) and 3% ( range, 3 to 7%), respectively (P < 0.05); meanwhile IgG1 and IgG4 subclass responses remained relatively unmodified in samples obtained years after in fection (mean 100% [SD, 96 to 100%] and 86% [SD, 79 to 93%], respectively). Results obtained defined two highly different immune isotypic response pat terns. One pattern is restrictive to IgG2 and/or IgG3 in the convalescent p hase and is kinetically similar to the IgM antibody response, so its detect ion could be referred to as a recent viral activity. On the other hand, IgG 1 and IgG4 were detected in both the convalescent and memory phases of the immune response, but their isolated occurrence without IgG2 and IgG3 could be related to the long-lasting immunity.