Ultrastructural alterations in human blood leukocytes induced by porcine circovirus type 1 infection

Swine infectious pathogens, especially viruses, represent a potential public health risk associated with the use of pig tissues for xenotransplantation in humans. We hypothesized that porcine circovirus type I (PCV-1) may infect human mononuclear cells, resulting in ultrastructural alterations of the target cells.

Transmission electron microscopy was used for evaluating ultrastructural alterations of human cells exposed to a PCV-infected PK15 cell line. A polymerase chain reaction (PCR) assay and fluorescence in situ hybridization (FISH) were developed for detecting PCV-1 in human mononuclear cells.

Morphological alterations of the human T cells exposed to PCV PK15 showed ''boomerang-shaped'' intracytoplasmic inclusions. Nucleocapsids appeared free, close to the nucleus, or contained into cytoplasmic vacuoles. Virions were observed near the surface of the human cells. A considerable number of mature virions and immature forms could be observed in the human cells that had a completely intact nuclear membrane with no alteration in the disposition of chromatin. PCV-1 particles were identified budding into typical Golgi saccules and vacuoles. Virions sized up to 23 nm in diameter, and appeared in the nucleus and in the periphery of the cellular core. PCV-1 infection was detected on CD4+, CD8+, CD14+, CD19+, and CD56+ human cells by PCR assay and FISH.

These results suggest that PCV has the capability of infecting human leukocytes in vitro, and should be considered a potential risk of viral transmission during xenotransplantation.