B19 parvovirus induced fetal hydrops: rapid and simple diagnosis by detection of B19 antigens in amniotic fluids.

In our study we describe the direct detection of parvovirus B19 capsid antigens in amniotic fluid samples for the rapid and simple prenatal diagnosis of B19 induced fetal hydrops. The assay was performed on amniotic fluid specimens from fetal hydrops dotted on nylon membranes. The two capsid antigens, VP1 and VP2, which represent four per cent and 96 per cent of the capsid, respectively, were detected using a pool of monoclonal antibodies directed against these two proteins and the complex was visualized by immunoperoxidase staining. The assay could be performed in about four hours and positive results were revealed at the end of the reaction as dark blue spots on the nylon membrane. We analysed 26 amniotic fluid samples from 26 selected cases of non-immune hydrops for the presence of B19 antigens. Out of these 26 samples, 13 had previously proved positive for B19 DNA, detected by dot blot hybridization and/or in situ hybridization and/or nested PCR, and 13 had proved negative. The results obtained with our assay were compared with results obtained for the presence of B19 DNA and a close agreement was found. The method is simple and rapid to perform, does not require costly instruments, and all the reagents used in the assay are commercially available. The assay described can thus be useful for a prompt counselling and management of B19 fetal infection.