Enterovirus 68 pathophysiology
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: João André Alves Silva, M.D. [2]
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Overview
Unlike other enteroviruses, EV-D68 causes respiratory disease almost exclusively. Its cellular tropism, optimal growth at lower temperatures, and acid-lability are responsible for its infection of leukocytes and cells of the respiratory mucosa. The virus has the ability to replicate inside leukocytes, which allows it to infect the parenchymal tissue, to increase its viral load that will contribute to viral dissemination, and to activate endothelial cells that attract more leukocytes to the infected site. Although viral transmission is not fully understood, the virus can be isolated in respiratory secretions and may be transmitted from person to person via aerosol or direct contact.
Pathogenesis
EV-68 belongs to the Human Enterovirus D species (HEV-D), along with EV-70 and EV-94. Unlike the remaining enteroviruses in its class, EV-68 is acid-labile, which reduces its ability to colonize the gastrointestinal mucosa. It has been implicated in respiratory infections and in very rare occasions in CNS disease. This property of EV-68 sets it apart from other enteroviruses.[1]
Tropism
- The virus shows optimal growth at lower temperatures, making the respiratory tract an adequate host for viral replication. Besides the cells of the respiratory mucosa, EV-68 also shows tropism for leukocytes. The virus binds receptors on the lymphocyte surface containing sialic-acid in order to access the cytoplasm.[2] Since leukocytes are capable of migrating to other tissues, by infecting these cells, the virus gains access to secondary sites.[1] Viral replication inside leukocytes limits their function, thereby facilitating viral replication and spread.[3]
- EV-68 also replicates inside endothelial cells that provide the required increase in viral load for the virus to infect parenchymal tissue, and gain access to secondary sites.[3] The virus also promotes the activation of endothelial cells leading to chemoattraction of further leukocytes.
- However, EV-68 shows less tropism for endothelial cells than EV-70 or EV-94, which makes infection of secondary sites less common.[1]
Transmission
Non-polio enteroviruses can be found in an infected person’s:[4] [5]
- Feces (stool)
- Eye, nose, and mouth secretions (such as saliva, nasal mucus, or sputum)
- Blister fluid
Transmission occurs via the following routes:
- Close contact, such as touching or shaking hands, with an infected person
- Touching objects or surfaces that have the virus on them, then touching eyes, nose, or mouth before washing hands
- Changing diapers of an infected person, then touching the eyes, nose, or mouth before washing hands
- Drinking water that has the virus in it
- Pregnant women who are infected with a non-polio enterovirus shortly before delivery can pass the virus to their babies.
Viral shedding from the respiratory tract, such as through coughing or sneezing, for 1 to 3 weeks or less. Infected people can shed the virus even if they do not have symptoms.
Immune Response
The immune response towards EV-68 is not fully understood. Viral clearance is achieved by an adequate T and B-cell response that contain and eliminate the virus. B lymphocytes, along with tissue macrophages contain the pathogen, while T lymphocytes penetrate the areas of infection, causing tissue damage. Tissue damage may lead to cell death of the affected areas.[6]
References
- ↑ 1.0 1.1 1.2 Smura T, Ylipaasto P, Klemola P, Kaijalainen S, Kyllönen L, Sordi V; et al. (2010). "Cellular tropism of human enterovirus D species serotypes EV-94, EV-70, and EV-68 in vitro: implications for pathogenesis". J Med Virol. 82 (11): 1940–9. doi:10.1002/jmv.21894. PMID 20872722.
- ↑ Vlasak M, Roivainen M, Reithmayer M, Goesler I, Laine P, Snyers L; et al. (2005). "The minor receptor group of human rhinovirus (HRV) includes HRV23 and HRV25, but the presence of a lysine in the VP1 HI loop is not sufficient for receptor binding". J Virol. 79 (12): 7389–95. doi:10.1128/JVI.79.12.7389-7395.2005. PMC 1143622. PMID 15919894.
- ↑ 3.0 3.1 Kramer M, Schulte BM, Toonen LW, de Bruijni MA, Galama JM, Adema GJ; et al. (2007). "Echovirus infection causes rapid loss-of-function and cell death in human dendritic cells". Cell Microbiol. 9 (6): 1507–18. doi:10.1111/j.1462-5822.2007.00888.x. PMID 17298395.
- ↑ "Enterovirus D68".
- ↑ Lu QB, Wo Y, Wang HY, Wei MT, Zhang L, Yang H; et al. (2014). "Detection of enterovirus 68 as one of the commonest types of enterovirus found in patients with acute respiratory tract infection in China". J Med Microbiol. 63 (Pt 3): 408–14. doi:10.1099/jmm.0.068247-0. PMID 24324030.
- ↑ Kreuter JD, Barnes A, McCarthy JE, Schwartzman JD, Oberste MS, Rhodes CH; et al. (2011). "A fatal central nervous system enterovirus 68 infection". Arch Pathol Lab Med. 135 (6): 793–6. doi:10.1043/2010-0174-CR.1. PMID 21631275.