African swine fever (ASF) virus induces immune cell alterations that may be detected by changes in peripheral blood cells phenotypic
antigens and activation markers which were examined by flow cytometry, analyzing both cell proportion and/or expression intensity of superficial
antigens. These studies were conducted in pigs with experimental acute of chronic ASF
infection to determine whether changes among important surface activation markers and phenotypic
antigens, and their correlative lymph node status, reflected similar or disparate aspects of immune pathology. In acute
infection produced by virulent viruses, macrophage and B lymphocyte populations decreased in peripheral blood after a short activation period at the beginning of the
infection. A significative decrease of
interleukin 2 receptor (IL 2R) expression was also observed in those pigs. These variations correlated with lymph node cell depletion due to an intense lymphoid cell death by apoptosis, affecting mainly the B lymphocyte subpopulation as determined by immunohistochemistry. Nevertheless, pigs infected with an attenuated isolate undergoing chronic
persistent infection, presented a distinct pattern of modification, according with a different clinicopathological evolution. Changes consisted in systemic immune activation coincident with the highest
viremia titer, with an augmentation in CD8+ T lymphocyte, macrophage, and B cell populations, and MHC (major histocompatibility complex)
antigens. Percentage elevation of circulating immune subpopulations was accompanied by cell accumulation with lymphoid
hyperplasia but a conserved distribution of B lymphocytes in lymphoid organs of chronically infected pigs.