Tissue persistence of parvovirus B19 genotypes in asymptomatic persons

With the aim to investigate the frequency of persistence and the tissue distribution of the three genotypes of B19V, the viral load of the persistent virus and its expression in the affected tissues, 139 tissue samples and 102 sera from 139 asymptomatic individuals have been analyzed by consensus PCRs and genotype specific PCRs for B19V detection and genotyping. Viral load was measured by real time PCR and viral mRNAs were detected by RT-PCR. Altogether, 51% individuals carried B19V DNA, more frequently in solid tissues (65%) than in bone marrow (20%). Genotype 1 was found in 27% tissue samples, genotype 2 in 48% and genotype 3 in 3% only. Twenty two point five % of B19V DNA sequences found in tissue samples were not clearly typeable. Viral load ranged from less then 10 copies to 7x104 copies per 106 cells, with the exception of two myocardium samples showing about 106 copies per 106 cells. Capsid proteins mRNA was present in two bone marrow samples only. In conclusion, in asymptomatic individuals B19V persistence is common in solid tissues more than in bone marrow, and genotype 2 persists more frequently than genotype 1. Altogether the results suggest that the virus persists without replicating, at sub-immunogenic levels.