Antibodies against BK virus in renal transplant recipient sera: results with five different methods indicate frequent reactivations.

Sera from 10 renal transplant recipients were investigated longitudinally for antibodies to human polyomavirus BK (BKV) using specific IgG-, IgA- and IgM-ELISA, hemagglutination inhibition (HAI) and neutralization tests (NT). Nine patients had anti-BKV serum antibodies before transplantation. The serological findings in 5 patients were compatible with reactivation of BKV infections. The results obtained with different tests were generally in good agreement. However, according to the definition of significant titer increase. 1-3 patients would have been undetected by employing HAI alone. High levels of antibodies detected by the other tests generally corresponded well with NT titers, i.e. the ability to neutralize infectivity. All the 5 patients with reactivation also showed an increase in specific IgA antibodies.