Ebola pathophysiology
|
Ebola Microchapters |
|
Diagnosis |
|---|
|
Treatment |
|
Postmortem Care |
|
Case Studies |
|
Ebola pathophysiology On the Web |
|
American Roentgen Ray Society Images of Ebola pathophysiology |
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Michael Maddaleni, B.S.; Guillermo Rodriguez Nava, M.D. [2]
Overview
The Ebola virus infects the mononuclear phagocyte system, but also other cells such as hepatocytes, spongiocytes, fibroblasts and endothelial cells, inducing tissue necrosis and disrupting the hematological and coagulation systems. The Ebola virus is transmitted by direct contact with infected patients or animals. The natural reservoir has not been identified.[1][2][3][4]
Pathophysiology
Tropism
- Ebola virus infects mainly the cells of the mononuclear phagocyte system, but also fibroblasts, hepatocytes, spongiocytes, adrenal cortical cells and endothelial cells.[1]
- The infection of the mononuclear phagocyte system cells plays a key role in the pathogenesis and spread of the disease as they carry the virus from of the initial infection site, through the lymphatic system and blood, to the regional lymph nodes,spleen and liver.[5]
- The next table summarizes the pathogenesis of the disease according to the virus tropism.
| Organ/Tissue | Effect |
|---|---|
| Endothelial cells | Glycoprotein (GP) on the virion envelope allows introduction of its content into the endothelial cells, which induces a cytopathic effect and damage to the endothelial barrier function that, together with effects of TNF-α released by infected mononuclear cells, leads to the loss of vascular integrity and increased leakage. |
| Liver | Causes hepatocellular necrosis which could impair the synthesis of proteins of the coagulation system[5] |
| Adrenal cortex | Affects the synthesis of enzymes responsible for the synthesis of steroids, leading to hypotension, and fluid and electrolytes disturbances.[5] |
| Lymphatic system | Necrosis of the spleen, lymph nodes and thymus; Apoptosis of lymphocytes leading to lymphopenia.[5][6] |
Immune response
- The virus activates the macrophages synthesis of interleukins (IL), which leads the Th1/Th2 balance towards a more pronounced Th1-cell mediated response.[7]
- Some inflammatory mediators produced during the ebola virus infection include: interferon (IFN)-alpha, IFN-beta, IL-2, IL-6, IL-8, IL-10, interferon-inducible protein 10; monocyte chemoattractant protein 1; regulated upon activation normal T cell expressed and secreted (RANTES); TNF-alpha; and reactive oxygen and nitrogen species.[8][9][10]
- Some viral proteins, such as VP35 and VP24, block the type I interferon response, which plays a key role of the pathogenesis of the disease.[11]
- The reactive oxygen and nitrogen species contribute to the cell and tissue damage, and therefore vascular and organ damage.[12]
- The nitric oxide is known to be an important vasodilator, therefore it plays and important role in the development of hypotension and shock.
Coagulation system
- Ebola infection is associated with hemorrhage in 50% of patients.
- Alterations of the coagulation system are induced by the ebola virus, and are thought to be mediated by the production of tissue factor:[13]
- Consumption of clotting factors
- Increased concentrations of fibrin degradation products
- Disseminated intravascular coagulopathy
Understanding the immune response to the disease
In one case study performed on an individual who had severe Ebola virus infection in Sierra Leone to further understand the immune response during all the stages of the disease.[14] The individual was provided with supportive care only without any other experimental therapies. Daily global gene expression in peripheral white blood cells was recorded and correlated with many clinical and laboratory aspects during the course of disease (Viral load, multiple organ dysfunction, coagulopathy, etc) till complete recovery after 33 days.
The study enabled us to identify the host responses (the genomic shift between increased expression of genes involved in inflammation and cell destruction to increased expression of genes promoting cell repair) that correlate with the viral clearance and recovery.
The study revealed that many changes in gene expression precede the change in the clinical status of the patient emphasizing the role of viral clearance in the cure of systemic illness.
References
- ↑ 1.0 1.1 Ryabchikova E, Kolesnikova L, Smolina M, Tkachev V, Pereboeva L, Baranova S; et al. (1996). "Ebola virus infection in guinea pigs: presumable role of granulomatous inflammation in pathogenesis". Arch Virol. 141 (5): 909–21. PMID 8678836.
- ↑ Bray M, Davis K, Geisbert T, Schmaljohn C, Huggins J (1998). "A mouse model for evaluation of prophylaxis and therapy of Ebola hemorrhagic fever". J Infect Dis. 178 (3): 651–61. PMID 9728532.
- ↑ Connolly BM, Steele KE, Davis KJ, Geisbert TW, Kell WM, Jaax NK; et al. (1999). "Pathogenesis of experimental Ebola virus infection in guinea pigs". J Infect Dis. 179 Suppl 1: S203–17. doi:10.1086/514305. PMID 9988186.
- ↑ Bray M, Hatfill S, Hensley L, Huggins JW (2001). "Haematological, biochemical and coagulation changes in mice, guinea-pigs and monkeys infected with a mouse-adapted variant of Ebola Zaire virus". J Comp Pathol. 125 (4): 243–53. doi:10.1053/jcpa.2001.0503. PMID 11798241.
- ↑ 5.0 5.1 5.2 5.3 Geisbert TW, Hensley LE, Larsen T, Young HA, Reed DS, Geisbert JB; et al. (2003). "Pathogenesis of Ebola hemorrhagic fever in cynomolgus macaques: evidence that dendritic cells are early and sustained targets of infection". Am J Pathol. 163 (6): 2347–70. doi:10.1016/S0002-9440(10)63591-2. PMC 1892369. PMID 14633608.
- ↑ Zaki SR, Goldsmith CS (1999). "Pathologic features of filovirus infections in humans". Curr Top Microbiol Immunol. 235: 97–116. PMID 9893381.
- ↑ Qiu X, Audet J, Wong G, Fernando L, Bello A, Pillet S; et al. (2013). "Sustained protection against Ebola virus infection following treatment of infected nonhuman primates with ZMAb". Sci Rep. 3: 3365. doi:10.1038/srep03365. PMC 3842534. PMID 24284388.
- ↑ Villinger F, Rollin PE, Brar SS, Chikkala NF, Winter J, Sundstrom JB; et al. (1999). "Markedly elevated levels of interferon (IFN)-gamma, IFN-alpha, interleukin (IL)-2, IL-10, and tumor necrosis factor-alpha associated with fatal Ebola virus infection". J Infect Dis. 179 Suppl 1: S188–91. doi:10.1086/514283. PMID 9988183.
- ↑ Hensley LE, Young HA, Jahrling PB, Geisbert TW (2002). "Proinflammatory response during Ebola virus infection of primate models: possible involvement of the tumor necrosis factor receptor superfamily". Immunol Lett. 80 (3): 169–79. PMID 11803049.
- ↑ Baize S, Leroy EM, Georges AJ, Georges-Courbot MC, Capron M, Bedjabaga I; et al. (2002). "Inflammatory responses in Ebola virus-infected patients". Clin Exp Immunol. 128 (1): 163–8. PMC 1906357. PMID 11982604.
- ↑ Basler CF, Mikulasova A, Martinez-Sobrido L, Paragas J, Mühlberger E, Bray M; et al. (2003). "The Ebola virus VP35 protein inhibits activation of interferon regulatory factor 3". J Virol. 77 (14): 7945–56. PMC 161945. PMID 12829834.
- ↑ Sanchez A, Lukwiya M, Bausch D, Mahanty S, Sanchez AJ, Wagoner KD; et al. (2004). "Analysis of human peripheral blood samples from fatal and nonfatal cases of Ebola (Sudan) hemorrhagic fever: cellular responses, virus load, and nitric oxide levels". J Virol. 78 (19): 10370–7. doi:10.1128/JVI.78.19.10370-10377.2004. PMC 516433. PMID 15367603.
- ↑ Geisbert TW, Young HA, Jahrling PB, Davis KJ, Kagan E, Hensley LE (2003). "Mechanisms underlying coagulation abnormalities in ebola hemorrhagic fever: overexpression of tissue factor in primate monocytes/macrophages is a key event". J Infect Dis. 188 (11): 1618–29. doi:10.1086/379724. PMID 14639531.
- ↑ "Longitudinal peripheral blood transcriptional analysis of a patient with severe Ebola virus disease | Science Translational Medicine".