CMV-IGG avidity and CMV-IGM concentration in both immunocompromised and immunocompetent patients.

Both CMV-specific IgG avidity index (AI) and CMV-specific IgM concentration were studied in different stages of CMV infection in both immunocompromised and immunocompetent patients. In these two groups (61 patients), a past CMV infection was associated with a mean AI constantly higher than 80%, just as the secondary infections observed in 18 immunocompromised patients (mean AI = 92%). In the 5 immunocompromised patients with primary CMV infection, the maturation of CMV IgG activity was delayed for at least one year; in contrast, the CMV-specific IgM concentration was persistently high up to 12 months. In additions, the 10 pediatric liver recipients who developed a primary CMV infection despite the administration of CMV specific immunoglobulins during the first two months post-transplantation had initially a high AI for anti-CMV reflecting the AI of passively acquired immunoglobulins. In four immunocompetent patients whose sera were taken less than 100 days after seroconversion, the mean AI was low (less than 35%) and was associated for 3 out of these 4 patients with a high concentration of CMV-specific IgM (IgM ratio > 3). Likewise, the AI of CMV-specific IgG in sera from 25 immunocompetent patients with suspected CMV infection was usually inversely correlated with CMV-specific IgM concentration. Thus, the use of these two parameters may help to date a CMV infection in immunocompetent patients especially in pregnant women.