Replication of porcine parvovirus in peripheral blood lymphocytes, monocytes, and peritoneal macrophages

Porcine peripheral blood lymphocytes (PBL), peripheral blood monocytes, and peritoneal macrophages were examined for their ability to support porcine parvovirus (PPV) replication. The cell cultures were infected with the NADL-2 strain of PPV at 0.1 multiplicity of infection. PBL cultures were stimulated with the following phytomitogens: phytohemagglutinin M, concanavalin A, and pokeweed mitogen. Unstimulated PBL cultures infected with PPV and uninfected PBL stimulated with phytomitogens served as controls. All cultures were examined daily for PPV-specific immunofluorescence and hemagglutinin. PPV replicated in PBL cultures stimulated with all phytomitogens. Both viral hemagglutinin in culture fluids and nuclear immunofluorescence in cells were detected. In contrast, unstimulated PBL did not support viral replication; however, PPV antigen was detected in the cytoplasm. PPV persisted in unstimulated PBL for 21 days (duration of the experiment) without replication, but replicated each time with the addition of phytohemagglutinin M at 0, 3, 7, 14, and 21 days after infection. Uninfected PBL stimulated with phytomitogens lacked both viral hemagglutinin and immunofluorescence. Simultaneous detection of lymphocyte surface marker and viral antigens in pokeweed mitogen-stimulated PBL revealed that both T and non-T cells (B and null cells) are able to support PPV replication. Peripheral blood monocytes and peritoneal macrophages phagocytized PPV but did not support virus replication.