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: 3.32). 11/2002; 302(2):363-72. DOI: 10.1006/viro.2002.1650
Source: PubMed


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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    • "Highly pathogenic PRRS (HP-PRRS) first emerged in China and Vietnam in 2006, and then spread rapidly in pigs throughout Asia [5,6]. Classical PRRSV infection induces apoptosis in different organs (lungs, testes, lymph nodes and thymus) in vivo and in cell lines in vitro [7-10], with apoptosis observed in both PRRSV-positive and PRRSV-negative cells [9,11]. However, apart from that detected in the thymus, there are no reports describing cell apoptosis induced by HP-PRRSV infection. "
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    ABSTRACT: Our previous studies have demonstrated that piglets infected with highly pathogenic porcine reproductive and respiratory syndrome virus (HP-PRRSV) may develop significant thymus atrophy, which related to thymocytes apoptosis. However, apart from that detected in the thymus, there are no reports describing cell apoptosis induced by HP-PRRSV infection. In this study, we analyzed comparatively the pathological changes, cell apoptosis and viral load in peripheral immune organs including tonsil, inguinal lymph nodes (ILNs) and spleen and lungs following experimental infection of piglets with HP-PRRSV HuN4 and classical PRRSV CH-1a. HP-PRRSV HuN4 exhibited much stronger cell tropism than CH-1a in immune organs and lungs of piglets. HuN4 infection led to the serious injuries in tonsils, ILNs, spleens and lungs, especially apoptosis in these organs was significant. HuN4 infection induced severe lesions (gross pathology, histopathology and cell apoptosis) in the peripheral immune organs and lungs of infected piglets. Large numbers of apoptotic cells in immune organs and lung induced by HuN4 may play a role in the pathogenesis of the HP-PRRS and the distinct injuries caused by HuN4 infection may be associated with the high mortality rate of HP-PRRS in pigs.
    Full-text · Article · Jan 2014 · Virology Journal
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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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    Full-text · Article · Sep 2011 · Journal of Animal Science
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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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    ABSTRACT: Porcine reproductive and respiratory syndrome virus (PRRSV) infection compromises the host's innate and adaptive immunity. The aim of this study was to investigate the immune responses of piglets infected with highly pathogenic (HP) PRRSV (HuN4 strain) with or without the immunization with CH-1R attenuated PRRSV vaccine. The response was evaluated for the clinical signs, pathological changes and virus load in immune organs, antibody responses and levels of serum IFN-γ, IL-4 and IL-10. The result showed that in comparison with the piglets received the immunization, the piglets infected with HP-PRRSV alone had the thymus atrophy, decreased serum levels of IL-4 and increased serum levels of IL-10 and INF-γ. These results suggest that elevated IL-10 levels at the early stage of the infection may enhance virus survival and delay the induction of protective immunity, while increased levels of IL-4 induce the effective immune responses and increase the animals' health status.
    Full-text · Article · May 2011 · Veterinary Immunology and Immunopathology
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