Table 1.
Alterations and characteristics of virus-induced thymic atrophy.
| Virus | Strain | Reference | Histological and immunophenotype alteration | Molecular characteristics | |
|---|---|---|---|---|---|
| PRRSV | PRRSV-1 | (21) | 1. Apoptosis of CD3+ thymocytes in the cortex. 2. Increase in macrophages both in cortex and medulla. |
a) Increase in TNF-α and IL-10 positive cells. | |
| HP-PRRSV (HuN4) | (22) (23) (24) |
1. Apoptosis in bystander cells (uninfected cells) e.g. CD3+ T cells. 2. Autophagy in both infected and bystander cells. CD14+ cells and thymic epithelial cells are the main autophagic cells. 3. Depletion of DP thymocytes. |
a) Decrease in IL-4. b) Increase in IL-10 and IFN-γ. |
||
| Lena strain | (25) | 1. Apoptosis in medulla and cortex. 2. Positive correlation between thymic atrophy and viral load. |
a) Increase in TUNEL and cCasp3 expression in cortex. b) Increase in cCasp8 and Fas in cortex and medulla. |
||
| BVDV | non-cytopathic BVDV-1a strain 7443 | (26) (27) |
1. Reduction in cortex: medulla ratio 2. Increase in type I collagen deposition and vascularization. |
a) Expression of receptor for BVDV, bovine CD46 in thymus. | |
| influenza A virus (IAV) | mouse-adapted influenza A/Puerto Rico/8/34 (H1N1; PR8) strain | (28) | a) Production of IFN-γby NK cells. | ||
| Avian Influenza A Virus | (29) | a) A consequence of digestive disorder. | |||
| Influenza A (H1N1) pdm09 | (30) (31, 32) |
a) Elevation in IFN-γ secreted by activated thymic innate CD8+CD44hi single-positive (SP) thymocytes. b) Large amounts of cytokines secreted by CD122+CD44hiEomes+ innate T cells upon infected thymic DCs stimulation. c) Anti-IFN-γ therapy aids to attenuate thymic atrophy. |
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| Avian Influenza A Virus (AIV)-H9N2 Mixed AIV-H9N2/Influenza B Virus (IBV) |
(33) | 1. Congestion of medulla blood vessels and hemorrhages together with thymic atrophy. | |||
| LCMV | (34, 35) | a) Via type I interferon and Stat2. b) IL-12 and TNF-α involved. |
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| SIV | SIV mac251-32H | (36) (37) |
1. Depletion of cortical epithelial cells and interdigitating dendrite cells. | a) Intrathymic macaques revealing phagocytosis occurs. | |
| Deletion of the vpu Sequences (novpuSHIVKU-1bMC33) |
(38) | 1. Depletion of thymocyte. 2. Destruction of thymic lobar and replaced by connective tissue. |
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| HIV | (39) (40) |
1. Depletion of DP thymocytes and SP thymocytes. 2. Blockage of maturation process from DN4 to DP. |
a) Growth hormone treatment may reverse. | ||
| Feline immunodeficiency virus (FIV) | (41) (42) |
1. Depletion of CD4+ thymocytes. 2. Acute thymic atrophy in fetal cats and developed chronic thymic atrophy in neonatal cats. |
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| Vaccinia virus (VV) |
neurotropic virulent WR strain | (43) (44) |
1. Depletion of DP thymocytes. | a) 3β-hydroxysteroid dehydrogenase expressed to synthesize steroid hormones encoded by gene A44L of VV. | |
| Murine leukemia virus (MuLV) | Friend murine leukemia virus | (45) | 1. Depletion in cortex. | ||
| Moloney murine leukemia virus (M-MuLV) | (46) | a) Degree of thymocyte apoptosis is positive correlated with M-MuLV leukemogenesis. | |||
| a radiation-induced strain of MuLV (RadLV-Rs) | (47) | 1. At 3rd week after infection: Perivascular clusters of B-cells at the cortico-medullary junction as the first change. 2. At 4th week after infection: depletion in cortex, while a mixed population of large T- and B-cells filled the medulla. |
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| Chicken anemia virus (CAV) | (48) (49) |
1. Depletion of DP thymocytes in cortex. 2. Apoptosis in thymic lymphoblasts. |
a) Thymic cortex is the main target of CAV. | ||
| Duck enteritis virus (DEV) | (50) | 1. Depletion of thymic lymphocytes. 2. Sustained immunosuppression as noted by the secondary bacterial infection. |
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| Mouse hepatitis virus (MHV) | Mouse hepatitis virus A59 (MHV-A59) | (51) | 1. Apoptosis of DP thymocytes. | a) Thymic epithelial cells have MHV receptors. b) Infection of thymic epithelial cells led to release of cytokines. |
|
| CSFV | (52) | 1. Atrophy of thymus | a) CSFV RNA was positive in the thymus when postnatal persistent infection. | ||
| MDPV | (53) | 1. Atrophy of thymus. | |||
| Newcastle disease virus (NDV) | VVNDV | (54) (55) |
1. Necrosis and depletion of the lymphocytes. | a) Vitamin A dietary supplementation delayed thymic atrophy. | |
| Marek’s disease alphaherpesvirus (MDV) | RB-1B | (56) | 1. Cell death in both thymic cells replicating MDV and uninfected cells in the thymus. 2. Premature exit of DP thymocytes. |
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| Rabies virus | (57, 58) | 1. Depletion of DP thymocytes. | a) Reversed by adrenalectomy. | ||
| Reticuloendotheliosis virus (REV) | (59) | 1. Decrease in thymus index 2. Increase in thymic reticular endothelial cells, inflammatory cell infiltration and nuclear damage. |
a) Increase the level of oxidative stress | ||
| Phocid herpesvirus 1 (PhHV-1) | (60) | 1. Thymic atrophy of grey seals Halichoerus grypus | |||
PRRSV, porcine reproductive and respiratory syndrome virus; HP-PRRSV, highly pathogenic porcine reproductive and respiratory syndrome virus; BVDV, bovine viral diarrhea virus; LCMV, lymphocytic choriomeningitis virus; SIV, simian immunodeficiency virus; HIV, human immunodeficiency virus; CSFV, classical swine fever virus; MDPV, muscovy duck parvovirus; VVNDV, velogenic viscerotropic pathotype of newcastle disease virus; DP, double positive.