Parvovirus B19 infection induces apoptosis of erythroid cells in vitro and in vivo

Objectives: intrauterine parvovirus B19 infection is related to non-immune hydrops fetalis, the pathogenesis of which is based on the strict tropism of B19 for erythroid precursor cells and the massive destruction of the infected erythroid cells, although the mechanism of B19-induced cytotoxicity has not been studied in detail. The purpose of this study is to provide empirical evidence that B19 induces apoptosis of erythroid cells both in vitro and in vivo. Methods: we analysed culture cells infected in vitro by B19 and tissues of nine cases of hydrops fetalis caused by B19 intrauterine infection by histological and biological methods. Results: cells infected in vitro by B19 showed nuclear changes characteristic of apoptosis by light microscopic examination and DNA extracted from the infected cells was fragmented. Electron microscopic examination showed the nuclei of infected cells contained crescent-shaped clumps of heterochromatin with increased density and double staining with anti-B19 antibody and terminal deoxynucleotidyl transferase (TdT)-mediated deoxyuridine triphosphate-digoxigenin nick-end labeling (TUNEL) confirmed apoptosis of individual cells. Tissues of cases of hydrops fetalis caused by B19 contained erythroid cells with nuclear inclusions and characteristic nuclear changes of apoptosis by light microscopy. The double-staining confirmed apoptosis of erythroid cells in the tissues. Immunohistochemical analysis with antibodies against cellular factors involved in apoptosis showed that caspase3, p53 and p21 were positive in infected cells. Conclusions: these data indicate that B19 infection causes apoptosis of infected cells and cellular factors, caspase3, p53 and p21, may play important roles in the apoptotic pathway induced by B19.