Pattern of anti-cytomegalovirus IgM antibodies determined by immunoblotting

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Abstract
In order to improve the knowledge of the humoral immune response to CMV infection, we developed an immunoblotting technique which allowed a better analysis of the changes in the pattern of anti CMV-polypeptides IgM. We examined 234 sera belonging to 27 renal allograft recipients developing a primary or recurrent CMV infection and 12 non infected recipients. Thus we found that 11 main anti CMV-polypeptides IgM antibodies were present in over 25% of the infected patients. They reacted with proteins whose molecular weights ranged from 32K to 205 K. We showed that anti-p 45–47 IgM antibodies were present in 100% of CMV infected recipients and never in the non-infected population. They appeared very early in the course of the infection (5.43 weeks post-graft for primary infection and 5.00 weeks for recurrent ones) and, therefore, constitute a good marker of active infection. Two other CMV-specific IgM antibodies (anti-p 60–64 and anti-p 100) were found exclusively in the course of primary infections. Anti-p 60–64 IgM was observed at a high frequency (57.1%) and with a mean delay of 6.57 weeks post-graft. Therefore, the anti-p 60–64 IgM detection could be helpful for the diagnosis of primary infection. In almost 100% of both primary and recurrent infections, we observed anti-p 140 and anti-p 38 IgM antibodies. Only about 50% of non-infected patients had low levels of anti-p 140 and anti-p 38 IgM. The follow-up of recurrent infections showed that the anti CMV-polypeptides IgM antibodies appeared earlier than in primary infection. When we compared anti-p 45–47 IgM detection by immunoblotting and anti-CMV IgM detected by ELISA we observed that immunoblotting permitted the diagnosis 2.5 weeks earlier for primary infection, and 1 week earlier for recurrent infection, than ELISA. In addition, the detection of anti-p 45–47 IgM antibodies also occurred earlier than virus excretion.