Latent human polyomavirus infection in pregnancy: investigation of possible transplacental transmission

Aims: The purpose of the study was to investigate the transplacental transmission of the human polyomaviruses JCV and BKV. Methods: Urine and blood samples from 300 pregnant women underwent cytological analysis to search for 'decoy cells', nested PCR to identify presence and genotype of isolated polyomaviruses, and sequence analysis of the transcription control region. Nested PCR was also used to study the umbilical cord blood of all their newborns. Results: Decoy cells were identified in only one urine sample (1/300; 0.33%); polyomavirus DNA was detected in 80 urine samples (26.6%) corresponding to BKV alone in 28 samples (9.3%), JCV alone in 49 samples (16.3%) and both JCV-BKV in three samples (1%). Blood samples were positive in 17 cases (5.6%), corresponding to BKV alone in 10 (3.3%), and JCV alone in 7 (2.3%). Rearrangements of the transcription control region were found in only one urinary JCV strain, consisting of the insertion of 13bp at D block, whereas point mutations were identified in 11 BKV and 11 JCV strains detected from urine. Sequence analysis of the BKV strains detected in blood samples revealed a 20bp insertion of P block (P42-61) in human chromosomes 20 (five cases) and 14 (three cases); two JCV strains had single bp point mutations. The search for polyomavirus DNA in umbilical cord blood samples was always negative. Conclusions: Polyomavirus DNA was frequently detected in pregnancy, whereas genomic rearrangements were rare, and no evidence of transplacental transmission of polyomavirus was obtained.