Pathology of porcine peripheral white blood cells during infection with African swine fever virus

Although band-to-segmented neutrophils ratio became much higher (3.5) in infected pigs than in control group (0.3), marked neutropenia and lymphopenia were detected from 2 to 3 days post-infection. In addition to band neutrophils, the high number of other immature white blood cells, such as metamyelocytes, was observed during the course of infection. From the beginning of infection, atypical lymphocytes, with altered nuclear shape, arose and became 15% of total cells in the final phase of infection. Image scanning cytometry revealed hyperdiploid DNA content in atypical lymphocytes only from 5 days post-infection, indicating that DNA synthesis in pathological lymphocytes occurred in the later stages of infection.From this study, it can be concluded that ASFV infection leads to serious changes in composition of white blood cells. Particularly, acute ASFV infection in vivo is accompanied with the emergence of immature cells and atypical lymphocytes in the host blood. The mechanisms underlying atypical cell formation remain to be elucidated.African swine fever virus (ASFV) is a large, enveloped virus containing double-stranded DNA (approximately 190 kilobase pairs) and the solo member of the recently created Asfarviridae [1]. It is the causative agent of a devastating hemorrhagic fever of domestic and wild swine. Depending on viral and host factors, ASFV infection of domestic swine can be accompanied with several disease forms, ranging from highly lethal (up to 100%) to subclinical. Infected pigs suffer from fever and anorexia as well as cyanosis of the skin, increased heart and respiratory rate and, finally, death. Currently, there is no vaccine or disease control strategy against ASFV other than movement restrictions, biosecurity and animal slaughter. Thus, the outbreaks of ASFV are still a great challenge for swine breeding.ASFV shares some similarities in genome structure and replication strategies with other families of large, nucleocytoplasmically replicating DNA