Eastern equine encephalitis virus

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1. Classification

a. Higher order taxa

Superkingdom: Viruses

Phylum: Kitrinoviricota

Class: Alsuviricetes

Order: Martellivirales

Family: Togaviridae

Genus: Alphavirus

Species: Eastern equine encephalitis virus (1)

2. Description and significance

Eastern equine encephalitis virus (EEEV) is an arbovirus (i.e. transmitted through arthropod vectors like mosquitos) that was discovered in 1933. EEEV has infected human and horse populations on the East Coast of the United States periodically through the years, resulting in death and extreme neurological impairments in those who survive (2). EEEV epidemics in humans are sporadic, but the number of cases has been rising in the last decade. The United States has an average of 11 human infections annually; however, in 2019, 38 cases were reported to the CDC (3). EEEV has a death rate estimated to be between 35 and 75%, the highest death rate of any mosquito-borne virus in North America (2).

While there is a correlation between changes in the weather and the seasons and increased EEE cases in the US, the exact cause is unknown (14). Current research focuses on the pathology of EEEV that is not fully understood and possible weaponization of the virus (17, 18).

3. Genome structure

EEEV belongs to the Alphavirus genus, which has a positive-sense single-stranded RNA genome that is approximately 12-kb and has a 5’ Cap and 3’ polyadenylated tail (4). The genome structure is highly conserved across strains of the virus (NA and SA EEEV). The genome encodes five structural proteins, which include the capsid and envelope proteins (E1, E2, E3, and 6K), and four non-structural proteins, nsP1-nsP4 (4, 5). The structural proteins are found near the 3’ polyadenylated tail and contain a subgenomic promoter (26S). The non-structural proteins are associated with viral genome replication and polypeptide processing and are found near the 5’ Cap (4,5). The positive-sense RNA can act as an mRNA because it is able to recruit eIF4E, which is a 5’ Cap binding protein that initiates translation by signaling the ribosomal subunits. This allows for the non-structural proteins to be translated (6).

4. Virion structure

The virus’s shell is icosahedral shaped and consists of two layers: outer transmembrane envelope and inner capsid layer. The outer layer contains E1 and E2 proteins. E1 protein’s function is associated with the fusion of the host cell and E2’s function is associated with receptor binding to the host cell (5). E2 has a binding site for heparan sulfate (HS), which allows the virus to avoid lymph node detection. The lymphatic system, which is a network of organs and tissues that filters out toxins, works in conjunction with the immune system by using lymphatic fluids to transport white blood cells and other antibodies. The lymph nodes, which contain immune cells, are able to signal an immune response in the presence of antigen such as a virus (7). E1 and E2 are unable to bind to DC-SIGN (dendritic cell-specific intercellular adhesion molecule-3-grabbing non-integrin) and L-SIGN (liver/lymph node-specific intercellular adhesion molecule-3 grabbing non-integrin) (5). EEEV is internalized by the host through endocytosis, which allows the nucleocapsid to be released into the cytosol of the host. The capsid is able to bind to the host cell’s ribosomes (5).

5. Metabolic processes

Describe important sources of energy, electrons, and carbon (i.e. trophy) for the organism/organisms you are focusing on, as well as important molecules it/they synthesize(s).

6. Ecology

Habitat; symbiosis; contributions to the environment.

7. Pathology

How does this organism cause disease? Human, animal, plant hosts? Virulence factors, as well as patient symptoms.

8. Current Research

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9. References

It is required that you add at least five primary research articles (in same format as the sample reference below) that corresponds to the info that you added to this page. [Sample reference] Faller, A., and Schleifer, K. "Modified Oxidase and Benzidine Tests for Separation of Staphylococci from Micrococci". Journal of Clinical Microbiology. 1981. Volume 13. p. 1031-1035.