Infection of porcine cells with human herpesviruses

Porcine organs are valuable candidate materials for xenotransplantation to humans. Long-term maintenance of well functioning transplants is a prerequisite for success. Transplanted organs may be damaged by immune reactions or by infectious agents in hosts. Human herpesviruses (HHVs) establish life-long latency in humans after a primary infection. They can be reactivated with various stimuli, including immunosuppression. This study was performed to verify the infectivity of some HHVs toward porcine cells. PK-15 cells infected with HHV-1 and HHV-2 showed cytopathology from 1 day after infection. Immunofluorescent (IF) staining of HHV-1- and HHV-2-infected PK-15 cells with respective antibodies demonstrated the expression of the respective viral antigens. Permissiveness of PK-15 to HHV-1 and -2 was confirmed by an infection test on Vero cells. Islet cells infected with HHV-5 showed no gross morphologic changes during the experimental course. A limited portion of islet cells reacted only to anti-IE1 and anti-IE2, but not to anti-UL44 or anti-gB antibody by IF staining, whereas a small portion of endothelial cells reacted to anti-IEs and anti-UL44, but not to anti-gB antibody. HHV-1 and -2 can permissively infect porcine cells, but HHV-5 infects a small proportion of cells with limited viral protein expression. HHV-4 could not transform peripheral blood mononuclear cells from miniature pigs. Collectively, because some HHVs can infect and damage porcine cells or impair their functions, HHVs should be cautiously monitored and controlled in humans when porcine cells or organs are transplanted to human beings.