Thymocyte and Peripheral Blood T Lymphocyte Subpopulation Changes in Piglets Following in Utero Infection with Porcine Reproductive and Respiratory Syndrome Virus

Department of Farm Animal Health and Resource Management, College of Veterinary Medicine, North Carolina State University, Raleigh, 27606, USA.
Virology (Impact Factor: 3.28). 11/2002; 302(2):363-72. DOI: 10.1006/viro.2002.1650
Source: PubMed

ABSTRACT Piglets infected in utero with porcine reproductive and respiratory syndrome virus (PRRSV) are born severely immunocompromised. In this article we more closely examine the effects of in utero PRRSV infection on circulating and thymic T cell populations. Numbers of CD4+, CD8+, and dual-positive lymphocytes were quantitated in circulation and in the thymus during the 2 weeks following birth. At birth we found that the number of circulating lymphocytes was suppressed by 60%. Lymphocyte numbers were also suppressed by 42% at day 7, but by day 14 the number of lymphocytes had rebounded and was actually 47% greater than controls. At birth and day 7, a drop in the number of CD4+ cells could partially explain the suppression we observed, while the rebound in total lymphocyte numbers seen at day 14 was due to a nearly fourfold increase in the number of circulating CD8+ cells. As a result, the normal CD4+:CD8+ ratio of between 1.4 and 2.2 for neonatal pigs was reduced to 0.1-0.5. The thymuses of infected piglets were found to be 50% smaller than those of control pigs and were characterized by cortical involution and severe cortical depletion of thymocytes. Analysis of the population of thymocytes revealed that double-positive thymocytes were suppressed to a greater degree than either single positive subpopulation. In addition, we show that the number of thymocytes undergoing apoptosis was increased twofold in piglets infected with PRRSV. Taken together, these results help explain the dramatic immunosuppression observed in neonatal animals infected in utero with PRRSV.

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    • "Previously established flow cytometry procedures were used to assess the T cell and B cell composition of the peripheral blood ( Feng et al . , 2002 ) . The follow - ing antibodies were utilized in 1 - , 2 - , or 3 - color flow cytometry and at the noted dilutions in the following series . Series 1 ( 3 - color ) contained antibodies for the following cells : γδ T cells ( δ - chain , mouse"
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    • "G. Wang et al. / Veterinary Immunology and Immunopathology 142 (2011) 170– 178 171 Utero infection with PRRSV caused serious thymus atrophy which lead to the immunosuppression in piglets born within one month (Feng et al., 2002), but the similar result was not found from the piglets infected with PRRSV after birth (Rossow et al., 1994). Since the suppressive ability is associated with the viral virulence (Charerntantanakul et al., 2006), we need to know the immune responses of pigs infected with HP-PRRSV. "
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    • "It is important to note that both apoptosis and necrosis can result in the reduction of cell size and DNA content and that the methods used in this study could not have differentiated between the two processes. Finally, a study by Feng et al. (2002) showed by the TUNEL method that the number of apoptotic thymocytes was increased two-fold in PRRSV-infected piglets. The study did not attempt to examine the apoptotic cells for the presence of a replicating virus. "
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