IMMUNOGLOBULIN-G AVIDITY TESTING IN SERUM AND CEREBROSPINAL-FLUID FORANALYSIS OF MEASLES-VIRUS INFECTION

We studied a variety of patients with measles virus infection by using avidity testing for measles virus-specific immunoglobulin G (IgG) in serum and cerebrospinal fluid samples, For the avidity testing, an Enz ygnost measles IgG enzyme-linked immunosorbent assay kit was used with an 8 M urea denaturing method, With this method, low-avidity IgG (acu te primary infection, avidity of <30% within 15 days of the onset of r ash) and high-avidity IgG (subacute sclerosing panencephalitis, avidit y of >75%) could be clearly distinguished by using serum samples, One patient, who developed a typical course of measles despite a previous vaccination, showed a positive IgM response with an initial low titer of measles virus-specific IgG of low avidity, but a later sample revea led a high titer of IgG of intermediate (40%) avidity, suggesting prev ious immunological priming, Two patients with breakthrough infection ( secondary vaccine failure), both having central nervous system involve ment, showed a positive IgM response with initial high titers of serum IgG of high avidity, In addition, one of the patients had a detectabl e level of measles-specific IgG in cerebrospinal fluid, In this patien t, the avidity of both serum and cerebrospinal fluid IgG decreased dur ing the short follow-up period, This phenomenon has never before been reported, In subacute sclerosing panencephalitis patients, the avidity of cerebrospinal fluid IgG was consistently lon;er than that of serum IgG, The difference in avidity between cerebrospinal fluid and serum IgG may be used as a direct indicator of intrathecal production of IgG . In conclusion, the avidity testing is simple to perform, reliable, a nd highly informative in the analysis of measles virus infection.